Sporadic schwannomas and neurofibromas …

Neuro-Oncology

Updated 05.30.2024
Released 10.15.1996
Expires For CME 05.30.2027

Sporadic schwannomas and neurofibromas

Authors: Stefania Maraka MD, Mariam/Myriam Markouli MD

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Editor: Rimas V Lukas MD

Sporadic schwannomas and neurofibromas

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Introduction

Overview

Sporadic schwannomas and neurofibromas are tumors that arise from the nerve sheaths of cranial nerves, nerve roots, spinal nerves, and peripheral nerves. Most schwannomas originate from the eighth cranial nerve, whereas neurofibromas more commonly arise along the spinal nerve roots. Often, these tumors can be followed clinically and radiographically. Some, however, require treatment. Maximal surgical resection is the treatment of choice for many of these tumors, but radiation therapy can be appropriate in selected cases. Systemic therapies are still under investigation for therapeutic potential. There has been recent regulatory approval for MEK inhibition for a subset of patients with neurofibromas occurring in the setting of neurofibromatosis type 1 (NF1). In this update, the authors discuss the pathophysiology, clinical presentation, treatment, and outcomes of these conditions.

Key points

	• Schwannomas are benign (WHO grade I) slow-growing, extra-axial tumors that can arise from Schwann cells in any cranial nerve, spinal nerve root, or peripheral nerve. They can frequently arise from the eighth cranial nerve.
	• Neurofibromas are usually benign (WHO grade I) peripheral nerve sheath tumors that involve Schwann cells as well as nerve fibers, fibroblasts, and cutaneous tissue. They can occur in superficial (cutaneous, subcutaneous) and deep (visceral, spinal, orbital) locations.
	• When intervention is indicated, surgical resection is the treatment of choice for most schwannomas and neurofibromas. Complete resection can be curative.
	• In selected cases, stereotactic radiosurgery (SRS) or fractionated radiotherapy may be effective for local control of tumor growth
	• There is currently no well-defined role for systemic therapy in sporadic schwannomas and neurofibromas. However, MEK inhibition has received regulatory approval for a subset of patients with neurofibroma occurring in the setting of neurofibromatosis type 1.

Historical note and terminology

Cruveilhier is credited with the most complete initial description of both the clinical and pathologic features of a vestibular schwannoma (15). Sir Charles Balance performed the first successful surgical resection of a vestibular schwannoma in 1894. The neurosurgical community thereafter quickly developed interest for vestibular schwannoma surgery (137), and over the next 30 years, surgical techniques were refined to such a degree that operative mortality was reduced from 50% to 60% in the early 1900s to 4% by 1931 (74). Additional advances, such as the advent of antibiotics, anesthesia, and refinement in surgical techniques have further improved surgical morbidity and mortality.

Schwannomas and neurofibromas are benign (WHO grade I) tumors arising from peripheral nerve sheaths (71). Schwann cells are the neoplastic cells of origin in both schwannomas and neurofibromas, but the latter also contain intratumor nerve fibers and a large variety of additional cell types, such as fibroblasts, perineurial cells, and mast cells (122).

Clinical manifestations

Presentation and course

	• Tumors stemming from peripheral nerve sheaths, sporadic schwannomas, and neurofibromas can originate from cranial nerves, spinal nerves, nerve roots, or peripheral nerves. Therefore, the clinical manifestations and evolution are variable, depending on the tumor location, size, and rate of growth.
	• Nonsporadic schwannomas occur in the context of neurofibromatosis type 2 (NF2) related schwannomatosis and non-NF2-related schwannomatosis, whereas neurofibromas are cardinal manifestations of neurofibromatosis type 1. These hereditary conditions are discussed in other appropriate articles.

Vestibular schwannomas. Vestibular schwannomas account for the vast majority of sporadic schwannomas. Because the Schwann cell-glial junction is variable, the tumor can arise from a lateral position near the inner ear or inside the labyrinth, to a medial position at the porus acusticus, to completely within the cerebellopontine angle (121; 39).

Patients with vestibular schwannomas present with (85):

	• Cochlear nerve dysfunction, as manifested by unilateral sensorineural hearing loss (95%) and tinnitus (63%). Hearing loss may have been present from 1 to 5 years (mean 3.7 years) prior to diagnosis. In most cases, the loss is gradually progressive, but it can present acutely in 10% to 20% of patients (possibly due to occlusion of the internal auditory artery). Sensorineural hearing loss develops from a combination of tumor-induced interference with cochlear vascular supply and compression of the cochlear nerve within the internal auditory canal. Tinnitus is often unilateral, confined to the affected ear, low grade in intensity, and constant.
	• Vestibular nerve dysfunction manifested by gait unsteadiness (61%). Due to the slow-growing nature of these tumors, acute vertigo is uncommon. Of note, intralabyrinthine schwannomas that have an intravestibular component are characterized by significantly worse vestibular function compared to schwannomas with purely cochlear involvement (144).
	• Involvement of the trigeminal nerve (17%), with facial hypoesthesia, paresthesia and pain.
	• Facial nerve compression (6%) leading to facial paralysis and in some cases, taste disturbance, xerophthalmia, xerostomia, or lacrimation.
	• Symptoms due to tumor mass effect on the adjacent infratentorial matter, such as ataxia, hydrocephalus, cerebellar herniation, and lower cranial nerve dysfunction.

Some patients also report subacute or chronic headache (29%). Although rare, patients can present with an acute severe headache associated with nausea and emesis from schwannomas that have hemorrhaged (58).

Trigeminal schwannomas. Trigeminal schwannomas usually arise from the trigeminal ganglion (121). Affected patients present with facial numbness (25% to 30%), pain (20% to 25%), and paresthesia (5% to 10%). Other symptoms may include headache (15%), diplopia (10%), and hearing loss/tinnitus (10%) (87). Notable clinical examination findings include ipsilateral trigeminal dermatome hypoesthesia, a weak or absent ipsilateral corneal reflex, limitations in extraocular movement, pyramidal signs by mass effect on the pons, dysmetria, and ataxia, and exophthalmos by rostral mass effect.

Other cranial nerve schwannomas. Ocular motor nerve schwannomas (III, IV, VI) are extremely rare (125; 54; 47; 48). They arise in the interpeduncular cistern more frequently than in the cavernous sinus or the orbit, and present with diplopia and headache. Patients may also have a variety of symptoms and signs localizing to the causative or adjacent structures (eg, visual loss, facial sensory loss, ataxia, proptosis).

Facial nerve schwannomas arise from the vertical segment of the nerve (within the temporal bone), or less often, near the tympanic membrane or cerebellopontine angle (121). Patients mostly report facial weakness and hearing loss (50% to 90%), tinnitus (60%), and vertigo (34%). The symptoms are slowly progressive in 80% of patients (mean 6 to 7 years), whereas in the remainder, the symptoms have an acute or fluctuating onset (106).

Lower cranial nerve schwannomas (IX, X, XI) may present with the classic jugular foramen syndrome: dysphagia, weakness and atrophy of sternocleidomastoid and trapezius muscles, hoarseness, and diminished taste (125; 07). When the tumor protrudes significantly into the posterior fossa, as is the case most often with glossopharyngeal schwannomas, patients may present with symptoms similar to those of vestibular schwannomas (125; 138).

Hypoglossal schwannomas are very uncommon and can present with tongue atrophy and weakness, vertigo, headache, and other brainstem compression symptoms.

Spinal schwannomas. Spinal schwannomas usually develop from the nerve roots, with a predilection for the dorsal sensory branches. The evolution of symptoms is slowly progressive, with a median symptom-onset to diagnosis delay of a year (14). Symptoms and signs include radicular (72%) and/or localized (59%) pain, peripheral weakness (60%), incontinence (33%), and gait difficulty (28%) (14; 109). Depending on the lesion localization, there may be myelopathic/upper motor neuron as well as lower motor neuron signs.

Peripheral nerve schwannomas. These tumors can arise on any peripheral nerve structure but are most common in the brachial plexus and flexor peripheral nerves, especially the elbow, knees, and wrists (56). Patients initially notice a painless mass, and with time, it may progress to become tender and/or cause compressive symptoms, such as hypoesthesia or paresthesia. On examination, patients typically have a tender mass that can be displaced from side to side, but not longitudinally. Percussion of the mass can often induce painful paresthesia in the distribution of the nerve. In most cases, there are no sensory and motor deficits in the distribution of the affected nerve. Most peripheral nerve schwannomas progress very slowly, but a minority (13%) of patients harbor fast-growing lesions (29). There is no correlation between initial tumor size, age at diagnosis, and tumor growth rate.

Neurofibromas. Similar to peripheral nerve schwannomas, sporadic neurofibromas tend to present as painless masses. Recent neurofibroma classifications have divided these tumors into superficial (cutaneous or subcutaneous) and deep (visceral, spinal or orbital) categories (46).

Arising from a peripheral nerve lying within the dermis or epidermis, a cutaneous superficial neurofibroma presents as a soft gelatinous sessile or pedunculated (“wart-like”), nontender, mobile nodule. There can be an overlying violaceous discoloration. These tumors do not carry a risk of malignant transformation, but they often cause esthetic issues or functional problems mandating surgical intervention.

Plexiform neurofibromas are similar to their cutaneous counterparts, but they tend to involve multiple nerve fascicles or a nerve plexus. When plexiform neurofibromas occur subcutaneously, they are palpable and can either be nodular (rubbery, firm, linear, and beaded) or diffuse (elastic and poorly defined, as a “bag-of-worms”). Unlike schwannomas, these tumors can occasionally cause neurologic deficits. When plexiform neurofibromas are located internally, they are nonpalpable masses involving the cranial cavity, orbit, cranial nerves, spine, or viscera (67). In these cases, clinical presentation and evolution are similar to that of schwannomas arising in the same location (112; 116). The lifetime risk for plexiform neurofibroma malignant transformation is estimated to be 10% (01).

Malignant peripheral nerve sheath tumors. Malignant peripheral nerve sheath tumors (MPNST) most commonly occur in patients with neurofibromatosis type 1, but they can arise in patients with sporadic neurofibromas, particularly nodular and plexiform neurofibromas. Malignant peripheral nerve sheath tumors present similarly to neurofibromas, but symptoms tend to evolve more rapidly and more commonly include motor and sensory deficits attributed to parent structure mononeuropathy or plexopathy, as well as progressive pain.

Clinical vignette

A 56-year-old male with an unremarkable past medical history progressively developed dizziness, tinnitus, and left-sided hearing loss over the span of 12 months. The initial neurologic examination was unremarkable. Audiometry confirmed mild left neurosensorial hearing loss. A left vestibular schwannoma was suspected following discovery on MRI of a 1.0 x 1.5 cm enhancing mass in the left cerebellopontine angle, with a tail that entered the internal auditory canal. The patient was subjected to a suboccipital surgical approach. The cochlear division of cranial nerve VIII was draped over the mass, which was attached to the vestibular division of VIII. After the mass was dissected away from the vestibular division, the tumor was removed piecemeal, with preservation of the facial nerve. The patient did well after surgery, with partial preservation of left-sided hearing and only mild left facial weakness, which improved after several months. Follow-up MRIs did not disclose tumor recurrence.

Biological basis

Etiology and pathogenesis

Sporadic schwannomas and neurofibromas arise from Schwann cells that provide myelinization of cranial nerves, spinal nerve roots, or peripheral nerves. Although the initial genesis of cellular neoplastic transformation is unknown in most cases, various contributory cytogenetic, chromosomal, and molecular biological events are discussed below.

Pathophysiology. In the most recent WHO Classification of Tumors of the Central Nervous System, Fifth Edition, schwannomas and neurofibromas are classified as cranial and paraspinal nerve tumors (71). Schwannomas are composed of a homogeneous mass of transformed Schwann cells in a collagenous background. Neurofibromas contain numerous transformed Schwann cells but also include a mixture of transformed perineurial cells and fibroblasts.

Macroscopic features. Schwannomas always arise at the transition zone between the central glial nerve sheath and the peripheral Schwann cell nerve sheath. Rarely, schwannomas can occur within the substance of the brain or spinal cord (120). There is a predilection for schwannomas to affect sensory nerves, although motor nerves can be involved as well. On gross pathologic inspection, schwannomas appear as discrete, rounded, firm, encapsulated masses of a semitranslucent or milky white color arising from a nerve fascicle. The tumors may have variable amounts of cyst formation, yellowish areas of xanthomatous changes, and hemorrhage.

Sporadic neurofibromas typically arise from small cutaneous terminal nerves, but they can also develop in large peripheral nerves, spinal nerves, or spinal nerve roots (108). On gross pathologic examination, neurofibromas are soft, well-circumscribed, pedunculated, and unencapsulated gelatinous masses of a whitish or opalescent color. Regions of cyst formation, xanthomatous changes, and hemorrhage are not seen as commonly as they are with schwannomas. During initial phases of growth, the tumor infiltrates the parent nerve, causing a localized, fusiform swelling. As the tumor enlarges, the parent nerve and those nerves around it may develop gross alterations of shape and can become encased within the mass.

Microscopic features. On histological examination, schwannomas are classically composed of a heterogeneous, biphasic architecture that contains two distinct regions, Antoni A (dense) and Antoni B (loose) (125). Nuclear palisading (Verocay bodies) is also present. In most tumors, the Antoni A regions predominate and are organized into dense, compact rows or arrays of elongated, spindle-shaped cells that have hyperchromatic, rod-shaped nuclei and eosinophilic cytoplasm. The tissue in Antoni B regions is characterized by large numbers of organelles (eg, mitochondria, lysosomes, osmiophilic bodies) and vacuoles. Immunohistochemical typing of schwannomas demonstrates strong reactivity to S-100 protein (in contrast to meningiomas), as well as Leu-7 and myelin basic protein. Therefore, cytoplasmic S-100 protein is often used to identify nerve sheath tumors (74).

Classic schwannoma showing Antoni A and Antoni B regions (photomicrograph)

Classic schwannoma demonstrating biphasic architecture composed of Antoni A and Antoni B regions. Antoni A regions are characterized by dense, compact rows of elongated, spindle-shaped cells with rod-shaped nuclei and eosinophilic...

Biological features. In general, studies measuring the biological activity of schwannomas are consistent with benign neoplastic processes, demonstrating small growth fractions and limited aggressive biological potential (17; 10). There is growing interest for the oncogenic potential of the inflammatory microenvironment in vestibular schwannomas (41).

The vestibular schwannoma microenvironment is determined by an interplay between stromal and immune cells that produce and remodel extracellular matrix, vascular networks, and promote tumor growth.

Angiogenesis seems to have an impact on tumor microenvironment, by influencing tumor growth index and prognosis. Even though vestibular schwannoma are generally slow-growing tumors, an increased vascularization has been found with delicate blood vessels on the adjacent vestibulocochlear nerve, susceptible to mechanical stress. This suggests that one of the most plausible explanations for hearing loss in vestibular schwannoma is edema of the cochlear nerve due to circulatory disturbances and postoperative hearing loss is likely due to blood vessel surgical injury (12).

Marioni and colleagues also investigated neoangiogenesis in sporadic vestibular schwannoma using CD105 staining and found that CD105 can serve as a useful marker to identify proliferating endothelium (83). It has finally been reported that vestibular schwannoma tumors stain positive for erythropoietin (EPO) and that tumors with higher EPO levels tend to be larger (20).

Immune system functions are also involved in tumor tissue formation. A positive correlation has been shown between tumor tissue inflammation and duration of clinical symptoms (65). When it comes to the highly studied tumor-associated macrophages (TAMs), M2-type macrophages which are known to have tumor-promoting features appeared to be highly expressed in vestibular schwannomas. Macrophage colony stimulating factor (M-CSF), which controls macrophage recruitment, proliferation, and transition towards a pro-tumoral M2-like phenotype, is highly expressed in fast-growing vestibular schwannomas, as well as cystic tumors (18) and can, therefore, be therapeutically targeted. Rapidly progressing vestibular schwannomas are also rich in CD68+ macrophages, CD4+ and CD8+ T lymphocytes, and CD20+ B cells (12).

Genetic features. Biallelic inactivation of the neurofibromin 2 gene (NF2, located on the q12 band on the long arm of chromosome 22), which is known to produce a tumor suppressor protein named merlin (also referred to as schwannomin), is found in most cases of sporadic vestibular schwannomas (148; 35). The most common mutations are small deletions that result in frameshifts (143). Protein expression studies have not revealed the presence of truncated or abnormally sized merlin products in NF2 muted cells, suggesting that mutant merlin proteins are unstable and may undergo rapid degradation (43). Epigenetic alterations of the NF2 gene may also play a role in schwannoma tumorigenesis (37). Overexpression of CPI-17, which can drive Ras activity and promote tumorigenic transformation via merlin inhibition, has been documented in sporadic vestibular schwannomas, suggesting this protein has a role in schwannoma oncogenesis (148). Other genes that are found to be mutated in sporadic vestibular schwannoma include SYNE1, IRS2, APC, CIC, SDHC, BRAF, NUMA1, EXT2, HRAS, BCL11B, MAGI1, RNF123, NLRP1, ASXL1, ADAMTS20, TAF1L, XPC, DDB2, and ETS1 (35).

Analysis into the angiogenic mechanisms underlying schwannoma growth has focused on the expression of vascular endothelial growth factor (VEGF) and its receptor (VEGFR-1) (11; 21). The concentrations of both VEGF and VEGFR-1 seem to correlate with tumor growth rate, but not with tumor size or symptom duration. Furthermore, VEGF expression appears to be greater in malignant peripheral nerve sheath tumor than WHO grade 1 schwannomas and neurofibromas (139). VEGF expression is also significantly higher in recurrent sporadic schwannomas than inaugural tumors, suggesting the protein may have a role in prognosis.

A study suggested that mechanisms including lipid metabolism, as well as Hippo and FOxO pathway dysregulation, may play a role in large vestibular schwannoma growth. They identified five target genes (SCD, LMNB2, TMEM43, JARID2, and CCND1 9) that were enriched and nine miRNAs that were abnormally expressed (miR-7, miR-142 miR-155, miR-342, miR-1269, miR-4664, and miR-6503 were upregulated, whereas miR-204 was down-regulated) in large compared to small intracanalicular vestibular schwannomas (69).

Furthermore, it was shown that nearly a third of sporadic schwannomas are characterized by recurrent in-frame insertion/deletion mutations of SOX10 while lacking changes in known nerve sheath tumor genes. This gene encodes for a transcription factor that controls Schwann cell myelination and differentiation. SOX10 mutation appears to be significantly enriched in schwannomas arising from nonvestibular cranial nerves (eg facial, trigeminal, vagus) and is absent in NF2-related vestibular nerve schwannomas. Functional studies have revealed that these SOX10 indel mutations have preserved DNA binding capacity but disrupted transactivation of myelination and glial differentiation programs (146).

The molecular basis underlying sporadic neurofibromas remains largely unexplored because virtually all tumors analyzed to date have been obtained from patients with neurofibromatosis type 1.

Epidemiology

	• Vestibular schwannomas account for the majority of sporadic schwannomas.
	• The vast part of cases (90%) are unilateral and occur outside of the context of neurofibromatosis type 2. The mean age at diagnosis is 50 years old, with no predominance in gender or lateralization.
	• Radiation exposure, particularly in childhood, is a well-recognized risk factor for the development of vestibular schwannomas. There are conflicting data on the association between vestibular schwannoma incidence and prior phone use.
	• Neurofibromas usually occur in young patients, with a mean age at diagnosis of 20 to 30 years. The grand majority of cases (90%) are solitary and not associated with neurofibromatosis type 1.

Schwannoma epidemiology. Schwannomas account for 6% to 8% of all primary central nervous system tumors, and most cases occur in adulthood (103; 64). The vast majority are sporadic and not associated with neurofibromatosis type 2-related schwannomatosis or non-NF2-related schwannomatosis. Overall, sporadic schwannomas have a peak incidence between 20 and 50 years, without gender or race predominance (96).

Vestibular schwannomas. The majority of cranial nerve VIII schwannomas arise from the vestibular branch of the vestibulocochlear nerve. The incidence of vestibular schwannoma is estimated to be of 0.8 to 1.09 cases per 100,000 population (103; 32; 64; 61), with 2.93 cases per 100,000 in the 65 to 74-year-old age group (64). Sporadic vestibular schwannoma incidence rate has been estimated at 3.0 to 5.2 cases per 100,000 person-years, with the highest rate reported among patients greater than or equal to 70 years of age (80). Overall, the incidence appears to be increasing in recent decades, due in part to incidental diagnoses (68). However, data suggest that increased incidence cannot be solely explained by greater detection alone (82). The mean age at diagnosis is approximately 50 years (103), with schwannomas occurring equally among both genders. Over 90% of schwannomas are unilateral, and there is no lateral predominance (27). Bilateral schwannomas are diagnostic for neurofibromatosis type 2-related schwannomatosis (134).

Other schwannomas. Among all intracranial schwannomas, trigeminal nerve schwannomas represent 0.8% to 8% of cases, whereas facial nerve schwannomas account for 0.5% to 1.9% of cases (125). Schwannomas of the other cranial nerves are extremely rare. The incidences of spinal and peripheral nerve schwannomas are unclear, but the former represent 15% to 50% of extramedullary spinal tumors (59).

Schwannoma risk factors. Epidemiological studies have attempted to identify risk factors for the development of sporadic vestibular schwannomas.

Family history. There have been reports in the literature that support a genetic or familial association between sporadic vestibular schwannoma cases that occur in patients who do not meet criteria for neurofibromatosis type 2-related schwannomatosis (04; 26). It is possible that some of these patients may represent mosaic neurofibromatosis type 2.

Radiation exposure. There is an association between the occurrence of vestibular schwannomas and prior radiation exposure. In a cohort of 3112 patients who had undergone therapeutic irradiation as children, 43 (1.38%) later developed a vestibular schwannoma, with a mean latency of 38.3 years. The relative risk was 1.14 per Gy of exposure (113). There does not appear to be an association between low-frequency magnetic field exposure and vestibular schwannoma incidence (34).

Phone use. Early metaanalyses investigating the possible association between cell and cordless phone use and subsequent brain tumor development found an increased risk for ipsilateral brain tumor incidence (overall odds ratio [OR] 1.6-1.9) in people whose usage exceeded 10 years (42; 55). The increased risk was observed for astrocytomas and vestibular schwannomas, but not for meningiomas. In a later study involving two Danish nationwide cohorts totaling 2.9 million subjects, there was no increased risk for the development of a schwannoma among phone users (115). It is possible that recall bias may be impacting these results. Of the tumors that did develop, tumors were not larger than expected or more likely to be on the ipsilateral side of phone use. In the INTERPHONE Study Group report, which studied 1105 patients with newly diagnosed vestibular schwannomas and 2145 case-matched controls, there was no association between vestibular schwannoma incidence and the use of a cell phone (OR 0.85), even among people who had 10 years of cell phone usage or more (OR 0.76) (49). No trends were noted for subjects with increasing cumulative call time or number of calls. In conclusion, a metaanalysis concluded that current data do not support an association between cell and cordless phone use and vestibular schwannoma incidence (90).

Smoking. There are studies supporting a protective role of cigarette smoking in developing vestibular schwannoma (26).

Medications. Certain medications seem to be protective against vestibular schwannoma, such as aspirin. Pharmacologic treatment of sporadic vestibular schwannoma with aspirin has, therefore, been proposed as a treatment alternative. It is thought to slow vestibular schwannoma growth through the inhibition of cyclooxygenase-2 (26). Metformin also appears to reduce the odds of vestibular schwannoma growth (72). At this time, these are not validated therapeutic approaches.

Noise exposure. Data on noise exposure as a possible risk factor for vestibular schwannoma are conflictual, with most studies relying on self-reported measures of exposure prone to recall bias (27). In a large epidemiological study based in Sweden, occupational exposure to mercury (OR 2.9) and benzene (OR 1.8) were associated with vestibular schwannoma incidence (102).

Neurofibroma epidemiology. Neurofibromas usually occur in young patients, with a mean age at diagnosis of 20 to 30 years. The grand majority of cases (90%) are solitary and not associated with neurofibromatosis type 1 (96). The exact incidence of sporadic neurofibromas is currently unknown.

Malignant peripheral nerve sheath tumor epidemiology. As noted previously, approximately 10% of patients with plexiform neurofibromas develop malignant peripheral nerve sheath tumor (01), with sporadic cases occurring at a later age than those associated with neurofibromatosis type 1 (mean age 40 to 45 years vs. 25 to 35 years, respectively) (70). Although 20% of patients with sporadic malignant peripheral nerve sheath tumor report having suffered prior malignancy, it remains unclear if prior personal or familial malignancy is truly a risk factor for malignant peripheral nerve sheath tumor (95). Prior radiotherapy is a well-documented risk factor for acquired malignant peripheral nerve sheath tumor in both patients with and without prior history of an underlying peripheral nerve sheath tumor (30).

Differential diagnosis

The differential diagnosis of sporadic schwannomas and neurofibromas depend chiefly on the tumor characteristics (eg, location, size, and growth rate). The broad differential diagnosis of all possible presenting symptoms and signs is vast and beyond the scope of this article.

Lesions of the cerebellopontine angle. Vestibular schwannomas account for a substantial percentage of cerebellopontine angle masses (123). The differential diagnosis of cerebellopontine angle lesions is listed in Table 1.

Table 1. Radiological Differential Diagnosis of a Cerebellopontine Angle Lesion

Differential diagnoses	Characteristics
Lesions originating in the cerebellopontine angle
Vestibular schwannomas	Vestibular schwannomas are classically spheric lesions centered around the porus acusticus that deform the canal. They enhance in contrast CT and MRI scans and can sometimes have a dural attachment.
Meningioma	Meningiomas typically grow as an oval or hemispheric mass rather than as a sphere, and usually have a broad dural attachment. Meningiomas are usually centered away from the porus acusticus, and they rarely enlarge or disturb the canal. Meningiomas demonstrate homogenous enhancement in contrast CT and MRI scans.
Endolymphatic sac tumors	These are tumors associated with von Hippel-Lindau disease. They appear in the auditory canal.
Epidermoid inclusion cyst	Lesions are respectively isodense and isointense to the CSF on CT and MRI scans. There may be rim contrast enhancement.
Arachnoid cyst	Lesions are respectively isodense and isointense to the CSF on CT and MRI scans, without contrast enhancement.
Lesions extending into the cerebellopontine angle
Metastases	Most common primary tumors are breast carcinoma, lung carcinoma, and melanoma.
Vascular structure (aneurysm, malformation, or aberrant loop)	These structures show intravascular enhancement on CT-angiography and MR-angiography, as well as flow void on conventional MRI.
Other central nervous system tumors	These include exophytic brainstem glioma, ependymoma, choroid plexus papilloma, schwannoma of other cranial nerves (V, VII, IX, X, and XI), jugular foramen paraganglioma, and lipoma.
Infectious diseases	These include tuberculomas and cysticercosis.

Other cranial nerve schwannomas. The differential diagnosis of schwannomas arising from cranial nerves other than VIII includes meningiomas, epidermoids, chondromas, chordomas, lipomas, and metastatic lesions.

Spinal schwannomas and neurofibromas. In most cases, spinal schwannomas are indistinguishable from spinal neurofibromas. Tumors to consider in the differential diagnosis of spinal nerve sheath tumors include meningiomas, paragangliomas, ependymomas, and intradural extramedullary metastases.

Peripheral nerve schwannomas and neurofibromas. The differential diagnosis of peripheral nerve schwannomas and neurofibromas consists of other neoplasms such as malignant peripheral nerve sheath tumor, lipomas, metastases, desmoid tumors, granular cell tumors, nerve sheath myxomas, lymphangiomas, and myoblastomas.

Syndrome-related and sporadic schwannomas and neurofibromas. Although the anatomical, perfusion, and diffusion properties of these entities are similar, the existence of many lesions across a nerve and signal heterogeneity are distinguishing markers of syndrome-associated neuromas and schwannomas compared to sporadic tumors (16).

Diagnostic workup

• In patients with clinical presentation compatible with a schwannoma or neurofibroma, imaging with a gadolinium contrast MRI is the diagnostic modality of choice.

Audiometry and neurophysiology for vestibular schwannomas. Clinically, benign vestibular conditions such as Ménière disease can present with symptoms and signs similar to those of vestibular schwannomas (hearing loss, tinnitus, nystagmus, and vertigo). However, a tumoral process can be ruled out by a careful history and examination, followed by appropriate paraclinical tests.

Patients reporting unilateral hearing loss or vertigo can undergo audiometry as a first screening test because only 5% of patients with a vestibular schwannoma will have normal results. Typically, affected patients will demonstrate asymmetrical neurosensorial hearing loss, particularly in the higher frequencies. In addition to audiometry, patients may undergo neurophysiological testing with brainstem-evoked response audiometry, which has a 93% to 98% sensitivity and a 90% specificity for vestibular schwannomas (24).

Despite the favorable diagnostic accuracy of these neurophysiological tests, neuroimaging remains the diagnostic modality of choice.

Neuroimaging of schwannomas and neurofibromas. Radiological findings for sporadic schwannomas and neurofibromas are summarized in Table 2. Benign neurofibromas and malignant peripheral nerve sheath tumor can also at times be differentiated with the use of FDG-PET scanning (31).

Table 2. Radiological Findings in Sporadic Schwannomas and Neurofibromas

Tumor	CT	T1-weighted MRI	T2-weighted MRI
Vestibular schwannoma	Isodense or hypodense to the brain, with homogeneous enhancement; erosion and enlargement of the internal auditory canal in 70% to 90%	Isointense or slightly hypointense relative to brain and are hyperintense compared to CSF, with diffuse enhancement	Hyperintense relative to brain, may be isointense to CSF
Trigeminal schwannoma	Mass with similar characteristics to vestibular schwannoma arising near Meckel cave in the middle fossa, posterior fossa, or both
Other cranial nerve schwannoma	Mass with similar characteristics to vestibular schwannoma arising in the respective territories (eg, hypoglossal canal for XII)
Spinal schwannoma and neurofibroma	Round or lobulated, intradural, extramedullary mass that often compresses the spinal cord	Isointense or slightly hypointense relative to spinal cord and hyperintense relative to CSF, with diffuse enhancement (may be heterogeneous if there is cystic degeneration, necrosis, or hemorrhage)	Variable signal intensity (depends on the relative amounts of Antoni A and B zones, cystic degeneration, and hemorrhage)
Peripheral nerve schwannoma and neurofibroma	Well-demarcated masses isodense to muscle, with some contrast enhancement	Hypointense with diffuse contrast enhancement	Hyperintense signal with a characteristic central hypointense region (“target sign”)
Plexiform neurofibroma	Large multilobulated masses composed of several neurofibromas spreading along nerves and their branches.	Hypointense with diffuse contrast enhancement	Hyperintense signal with a characteristic central hypointense region (“target sign”)

Vestibular schwannoma (CT) (1)

(A) Axial, enhanced image at the level of the cerebellopontine angle, demonstrating a large, diffusely enhancing tumor centered over the internal auditory canal. The mass extends through the porus acusticus into the internal enlar...
Vestibular schwannoma in the left cerebellopontine angle (MRI)

Forty-three-year-old male with the complaint of left-sided hearing loss and double vision. Axial T1-weighted (TR 900/TE 15), enhanced MRI at the level of the lower pons, demonstrating a medium-sized, cisternal, vestibular schwanno...
Trigeminal schwannoma (MRI)

Thirty-two-year-old male with a history of trigeminal schwannoma removed 8 years ago developed recurrent right facial numbness. Left: Axial, T1-weighted (TR 500/TE 25), enhanced MRI at the level of the pons and Meckel’s cave. A la...

There is significant heterogeneity in the literature regarding the potential associations of tumor structural characteristics on neuroimaging (for instance, size and location) and the degree of neurosensorial hearing loss at presentation among patients with sporadic vestibular schwannomas, suggesting the pathophysiological mechanisms of hearing loss in this population may be multifactorial (06).

Recent work has suggested that diffusion-weighted magnetic resonance imaging may be useful in differentiating plexiform neurofibromas from malignant peripheral nerve sheath tumor among patients with neurofibromatosis type 1 (142; 147; 60). A systematic review and metaanalysis investigating the role of MRI in malignant peripheral nerve sheath tumor diagnosis showed that tumor apparent diffusion coefficient values were highly sensitive (88%) and specific (94%) for malignant peripheral nerve sheath tumor (147). This research suggests that diffusion-weighted MRI characteristics may be superior to conventional morphologic features for identifying malignant transformation, but this requires further investigation in both patients with and without neurofibromatosis type 1.

Biomarkers. Multiple circulating biomarkers have been studied through liquid biopsies to determine if they can be employed for screening and personalized treatment in vestibular schwannoma. Circulating serum VEGF has been suggested as a potential biomarker for selection criteria of patients who would benefit from anti-VEGF therapy. A study also identified nine biomarkers (TNR-R2, MIF, CD30, MCP-3, IL-2R, BLC, TWEAK, eotaxin, and S100B) that are significantly elevated in vestibular schwannoma and can serve as diagnostic biomarkers as well as potential therapeutic targets. Of note, S100B has been associated with tumor growth and MCP-3 with hearing change. They can, therefore, be used to predict disease progression and guide timing of intervention to preserve hearing (136). CSF is thought to be a source of potential biomarkers with ABCA3 and KLF11 having been identified to positively correlate with vestibular schwannoma tumor size, whereas BASP1 and PRDX2 levels were negatively correlated with tumor growth (105). Ki-67 index is also thought to be a useful biomarker for possibility of tumor recurrence following surgical resection. Ki-67 can thereby help detect early tumor recurrence and potential need for early adjuvant therapy (135). At this time, none of these biomarkers have been prospectively validated and, in turn, are not a component of the standard of care.

Management

	• Overall, schwannomas and neurofibromas can be managed conservatively (with observation), with surgery, radiotherapy, or radiosurgery.
	• In most cases where an intervention is warranted, surgery is the preferred modality and can be curative.
	• There is a limited role to systemic therapy in vestibular schwannomas outside the context of neurofibromatosis type 2-related schwannomatosis.

Vestibular schwannomas. In general, these tumors can be addressed conservatively, with a watch-and-wait approach, or be subjected to intervention with neurosurgery, fractioned radiotherapy, and radiosurgery (36). The goals are to preserve function, particularly hearing, as long as possible and to minimize risks associated with intervention (149). Data on the success and safety of different interventional treatment modalities continue to emerge, but randomized trials comparing different interventions remain sparse and have limited generalizability (133). It is worth mentioning, however, that upfront radiosurgery was shown to be associated with a more pronounced tumor reduction at 4 years compared to conservative management with observation for patients with newly diagnosed small- and medium-sized vestibular schwannoma (19). Supplementary research on long-term clinical outcomes is required, and these results may help guide treatment choices for vestibular schwannoma patients.

Conservative management (observation). Because these tumors tend to progress slowly, a watch-and-wait approach may be appropriate in carefully selected patients. This strategy is most often employed in patients with significant comorbidities or with important contralateral hearing loss, as well as in elderly patients with small (less than 10 mm) asymptomatic schwannomas (50). A study demonstrated that even large Koos grade 4 vestibular schwannomas that compress the brainstem may be initially appropriate for observation and a wait-and-scan approach, if no significant clinical symptoms of mass effect are present that warrant urgent treatment (114). If hearing loss is an important consideration for patients, early intervention is generally associated with better outcomes than intervention following a period of hearing loss during observation (52).

Candidates who undergo observation should be reimaged at a 6 to 12-months for tumor growth surveillance (09). If there are signs or symptoms of tumor progression, or rapid tumor growth (greater than 2.5 mm/year), intervention should be seriously considered regardless of age (111; 104). There is no specific consensus on the ideal duration of serial neuroimaging in patients who do not demonstrate tumor progression, but several authors commend yearly screening for 5 years, followed by less frequent follow-ups if the tumor remains stable (25; 77).

Surgery. Three surgical approaches are used for vestibular schwannoma resection: (1) suboccipital (retrosigmoid), (2) translabyrinthine (anterosigmoid), and (3) middle fossa (subtemporal). Each has specific advantages to offer, based on selection criteria that include tumor size, depth of internal auditory canal penetration by tumor, hearing status, exposure of the facial nerve, and patient age (129).

	• The suboccipital approach can be used for any tumor size, regardless of whether hearing preservation is an issue or not. Postoperative headache is most frequent with this strategy.
	• The translabyrinthine approach is mostly employed for large (greater than 3 cm) tumors or for smaller tumors that are located in the deep internal auditory canal. This intervention abolishes ipsilateral hearing and is associated with postoperative CSF leakage.
	• The middle fossa approach is most appropriate for small (less than 1.5 cm) tumors, particularly those outside the internal auditory canal, when hearing preservation is desired. There is an increased risk of facial nerve trauma with this technique.

Patients undergoing surgery should be monitored for recurrence with yearly neuroimaging. At minimum, they should undergo a control MRI within the year after surgery (25; 78). If there was residual tumor, the minimal duration of follow-up is not clear, with some authors suggesting 3 to 5 years of annual imaging followed by less frequent follow-up in the absence of tumor progression (25; 05).

Patients treated by surgery may also be eligible for simultaneous cochlear implantation, which may restore some degree of ipsilateral hearing following resection (23; 145). Cochlear implantation is preferred over auditory brainstem implantation in vestibular schwannoma patients and offers better hearing outcomes. It offers patients a functioning cochlear nerve, the ability of open set speech discrimination, and an improved quality of life (86).

Radiation therapy. Suitable radiation treatment modalities include stereotactic radiosurgery, stereotactic radiotherapy, proton beam therapy, and fractionated radiation therapy. In the absence of controlled randomized trials comparing these strategies, observational data currently suggest that outcomes are equivalent for all approaches and that the chosen modality should, therefore, depend on patient preferences and center-specific factors, such as expertise and availability (94).

	• Stereotactic radiosurgery is an interesting option for patients with smaller (less than 3 cm) tumors or for those who are not candidates for surgery. Stereotactic radiosurgery seems to have at least equivalent rates of tumor control and hearing preservation compared to microsurgery, with better facial nerve preservation (03).
	• Stereotactic radiotherapy is an alternative to stereotactic radiosurgery, with radiation delivered over a series of treatment sessions. This is also the modality of adjuvant therapy in patients with subtotal surgical resections.
	• Proton beam therapy is a suitable alternative to the two above-mentioned modalities, although currently there is scant literature available on its outcomes and complications.

Patients undergoing radiation therapy should be monitored for recurrence with yearly neuroimaging. The minimal duration of follow-up is not clear, with some authors suggesting 10 years of annual imaging followed by repeat imaging every 2 years.

A study attempted to investigate the clinical outcomes of salvage microsurgery following failed stereotactic radiosurgery or fractionated stereotactic radiotherapy in patients with sporadic vestibular schwannoma (81). More than half of patients developed facial paralysis long-term or could not achieve gross total resection. Growth-free survival rates and perioperative complications like postoperative cerebrospinal fluid leak, hydrocephalus, symptomatic stroke, and meningitis were also worse compared to primary microsurgery rates.

The future progress of stereotactic radiosurgery and its implementation into clinical practice will be further driven by continued advances in imaging, targeted therapeutics, artificial intelligence, and biomedical engineering. The combination of pharmacologic and radiation therapies that act synergistically will help reduce the therapeutic dose needed for radiotherapy, thereby minimizing its adverse effects (89).

Other cranial nerve schwannomas. Owing to their rarity, there are no good quality data on the natural history of these tumors. The viable approaches to management for these schwannomas are overall similar to those of vestibular schwannomas, with the exception of proton beam therapy, which has not been extensively studied in this context. Stereotactic radiotherapy has been successfully applied to patients with trigeminal, jugular foramen, and hypoglossal nerves (100), and stereotactic radiosurgery is also proven successful in trigeminal, facial, oculomotor, and jugular foramen schwannomas (84; 57; 119).

Spinal and peripheral schwannomas and neurofibromas. The decision to intervene on spinal and peripheral nerve schwannomas and noncutaneous neurofibromas depends on individual patient factors, such as the degree of symptomatic and functional burden. Cutaneous neurofibromas are not typically removed in the absence of pain, functional impairment, or significant impact on quality of life.

When patients opt to intervene, surgical management is the standard of care. Overall, the outcomes are better for schwannomas than neurofibromas, mostly because the latter operation often implies sacrificing parent and adjacent nerves fascicles.

Systemic therapy. In general, systemic therapy is not frequently utilized for patients with sporadic schwannomas or neurofibromas. Case reports suggest there may be a benefit in using bevacizumab for schwannomas, mandating further research for this agent that has been more extensively studied in the context of NF2-related schwannomatosis (98; 53; 73). VEGF inhibitors mainly seem to have a role in recurrent vestibular schwannoma and vestibular schwannoma already treated with radiosurgery. These cases of vestibular schwannoma appear to have elevated VEGF expression, possibly protecting the endothelial and/or tumor cells during radiation, causing failure of radiosurgery. It was, therefore, suggested that a combination of radiotherapy and anti-VEGF treatment might improve therapeutic outcomes (63). In addition to monoclonal antibodies, immune check point inhibitors also seem to hold promise for vestibular schwannoma like in many other cancers due to reactivation of antitumor cytotoxic lymphocytes (89).

In a phase 2 trial, selumetinib was successful in inducing durable tumor shrinkage and clinical benefit in children with inoperable plexiform neurofibromas caused by neurofibromatosis type 1 (40). Another phase 2 trial showed that cabozantinib was effective in decreasing neurofibromatosis type 1 related inoperable plexiform neurofibroma size and improving patient outcomes, most importantly pain caused by the tumor (33). Finally, a phase II clinical trial demonstrated that the MAPK/ERK kinase inhibitor, mirdametinib, produced a 42% partial response rate and early signs of pain reduction in patients with NF1 and inoperable plexiform neuromas (141). Systemic therapies for neurofibromas and schwannomas are thus likely to be subjected to further research in the coming years, although most likely among populations of individuals with neurofibromatosis. Because the pathophysiological mechanisms driving tumors are the same for patients with sporadic schwannomas and neurofibromas, these therapies could prove useful in this population as well, especially for situations where surgical and radiation therapies are not optimal choices.

Outcomes

The overall prognosis for survival and intact neurologic function for patients with sporadic schwannomas and neurofibromas is relatively good. In most cases, these are benign, slow-growing, encapsulated tumors with a limited capacity for infiltration and destruction of surrounding tissues.

Vestibular schwannomas. Longitudinal studies suggest that interventional management improves patient outcomes (particularly with regards to local tumor control rates and risk of recurrence), but studies that have focused on patient quality of life have not disclosed an advantage of any particular strategy over observation (88).

Conservative management (observation). A majority (59%) of untreated tumors grow at a rate less than 1 mm/year, but some (12%) progress relatively quickly at rates greater than 3 mm/year (02). Tumor growth rate appears to be a significant predictor of subsequent hearing loss in patients with small vestibular schwannomas (less than 25 mm in diameter), with rates greater than 2.5 mm/year associated with poorer hearing prognosis (127). In fact, median time to hearing loss is much quicker (1 to 2 years) in patients with rapid tumor growth than those with patients with slow or absent growth (15 years) (126).

In a metaanalysis comprising 1345 patients followed for a mean follow-up length of 3.2 years, 43% of tumors grew, whereas 57% remained stable or regressed (124). Importantly, 20% of cases ultimately required intervention for significant tumor growth or symptom progression.

Surgery: outcomes. Complete resection is feasible in 97% to 99% of cases (38; 85) and is considered curative (85), with a recurrence rate after gross total resection of only 1% to 2% in most large series. Among patients with incomplete resection, up to 44% will experience tumor regrowth or recurrence, with 26% requiring additional intervention (28). Hearing loss is unlikely to improve after surgery, but most patients retain intact hearing function after surgery. Tumor size appears to be an important determinant of postoperative hearing preservation (101). At 5-year follow-up, 81% of patients with serviceable post-operative hearing maintain functional audition (22). A helpful marker to determine postoperative recurrence and retreatment is the preoperative neutrophil-to-lymphocyte ratio. A preoperative ratio greater than or equal to 2.21 seems to be significantly associated with retreatment after schwannoma resection and can help in the future guidance on treatment decisions (132). Finally, patients with preoperative hydrocephalus do not require permanent shunting after surgery in 78% of cases (97).

Surgery: complications. The most common surgical complications are headache (46%), which can persist after surgery, and CSF leakage (8.5%). Facial nerve trauma is rare (3% to 6%) (38; 85), but an important proportion of patients experience postoperative facial weakness: 70% of patients with large tumors, 50% of those with medium tumors, and 30% of those with small tumors have neuropraxia of the facial nerve after resection (92; 131). Hydrocephalus can occur postoperatively, particularly in the context of large (greater than 3 cm) tumors (97). Mortality is low (0.2%) (128). As is the case with most surgeries, older patients are at higher risk of medical complications following vestibular schwannoma surgery than their younger counterparts (130). Younger age at surgery is independently associated with complete facial nerve recovery, which can assist in intraoperative decision-making regarding extent of resection and postoperative counseling (76).

A study evaluated the quality of life in patients after vestibular schwannoma surgery, which was mostly impaired by postoperative headaches and facial nerve dysfunction. Patients with large tumors seemed to have a noticeably higher risk of postoperative facial nerve paresis, liquorrhea, and lower chances of hearing preservation. Patients with smaller tumors and history of headaches prior to surgery appeared to have more severe and frequent headaches after surgery, which was associated with higher anxiety and tinnitus. Higher anxiety was noted in patients who became deaf after surgery (66).

In terms of hearing preservation, a study showed that patients that demonstrated a hearing preservation advantage are the ones who underwent microsurgical resection within 3 months from time of diagnosis (91).

Radiation therapy: outcomes. Patients undergoing stereotactic radiosurgery with marginal doses of 12 to 13 Gy have good 10 and 15-year local control rates (91 and 89%, respectively), but a quarter of patients (25%) experience long-term hearing loss (08; 45; 44). Risk factors for hearing loss include older age, tumor size and poorer baseline hearing function (107; 93).

Given that stereotactic radiosurgery is associated with iatrogenic hearing loss, a study aimed to examine the level of hearing preservation in 37 patients with serviceable hearing who underwent stereotactic radiosurgery for sporadic intracanalicular schwannoma (51). Hearing was preserved in patients with smaller tumors and in all patients with a tumor volume of 0.05 cm3 or less, lower marginal doses, and with better preoperative hearing. On the other hand, a marginal dose of over 12 Gy and tumor volumes greater than 0.1 cm3 significantly increase the risk of nonserviceable hearing deterioration.

Stereotactic radiotherapy has similar local tumor control success than stereotactic radiosurgery, with 5 and 10-year control rates of 96%, but patients typically receive larger doses of radiation (25 to 60 Gy) (13). Proton beam therapy has a 5-year control rate of 94%, with 33% of patients retaining functional hearing (140).

Radiation therapy: complications. In patients subjected to stereotactic radiosurgery, about 25% experience long-term hearing loss, as mentioned above. In addition, postradiation tumor expansion is observed in 14% of cases (median delay of 9 months). Among these patients, 57% demonstrate subsequent spontaneous tumor regression, 29% remain stable, and 14% have progressive growth that require intervention (99). Facial and trigeminal neuropathy occurs in less than 5% of cases (94), and 2% of patients develop delayed cystic formation (occurring at a median of 6 years after intervention) (45).

Patients undergoing proton beam therapy sometimes require salvation therapy (6%). Facial and trigeminal nerve injury occurs in 9% and 11% of cases, respectively (140).

Other cranial nerve schwannomas. Trigeminal schwannomas, as well as schwannomas of other cranial nerves, have a less favorable prognosis. In general, complete resection is challenging due to inadequate surgical exposure, involvement of the cavernous sinus, encasement of blood vessels, and adherence to the brainstem (125; 07). For trigeminal tumors, the complete resection rate is 70% to 80% in modern series. Recurrence is rare after total extirpation. However, in cases with residual tumor, progression usually occurs within 3 years.

Spinal and peripheral nerve schwannomas and neurofibromas. Complete surgical resection of spinal schwannomas and neurofibromas occurs in 85% to 90% of cases (116; 109). In patients with subtotal removal, recurrence develops in 50% to 55% of cases, but only 18% require a second intervention (117). Patients undergoing peripheral nerve schwannoma resection can experience objective motor improvement (18%) or resolution of subjective symptoms (52%) (56). Complete resection is curative (150). In the context of operated peripheral neurofibromas, resection of tumors located in the brachial plexus is associated with additional postoperative morbidity in 8% to 31% of cases (56).

Media

References

01: Anderson JL, Gutmann DH. Neurofibromatosis type 1. In: Handbook of Clinical Neurology. 1st ed. Vol. 132. Amsterdam: Elsevier BV, 2015:75-86.
02: Bakkouri WE, Kania RE, Guichard JP, Lot G, Herman P, Huy PT. Conservative management of 386 cases of unilateral vestibular schwannoma: tumor growth and consequences for treatment. J Neurosurg 2009;110(4):662-9. PMID 19099381
03: Balossier A, Sahgal A, Kotecha R, et al. Management of sporadic intracanalicular vestibular schwannomas: A critical review and International Stereotactic Radiosurgery Society (ISRS) practice guidelines. Neuro Oncol 2024;26(3):429-43. PMID 38134966
04: Bikhazi NB, Slattery WH 3rd, Lalwani AK, Jackler RK, Bikhazi PH, Brackmann DE. Familial occurrence of unilateral vestibular schwannoma. Laryngoscope 1997;107(9):1176-80. PMID 9292599
05: Breshears JD, Morshed RA, Molinaro AM, McDermott MW, Cheung SW, Theodosopoulos PV. Residual tumor volume and location predict progression after primary subtotal resection of sporadic vestibular schwannomas: a retrospective volumetric study. Neurosurgery 2020;86(3):410-6. PMID 31232426
06: Brown A, Early S, Vasilijic S, Stankovic KM. Sporadic vestibular schwannoma size and location do not correlate with the severity of hearing loss at initial presentation. Front Oncol 2022;12:836504. PMID 35372070
07: Bulsara KR, Sameshima T, Friedman AH, Fukushima T. Microsurgical management of 53 jugular foramen schwannomas: lessons learned incorporated into a modified grading system. J Neurosurg 2008;109(5):794-803. PMID 18976067
08: Carlson ML, Jacob JT, Pollock BE, et al. Long-term hearing outcomes following stereotactic radiosurgery for vestibular schwannoma: patterns of hearing loss and variables influencing audiometric decline. J Neurosurg 2013;118(3):579-87. PMID 23101446
09: Carlson ML, Link MJ, Driscoll CLW, et al. Working toward consensus on sporadic vestibular schwannoma care: A modified Delphi study. Otol Neurotol 2020;41(10):e1360-71. PMID 33492814
10: Casadei GP, Scheithauer BW, Hirose T, Manfrini M, Van Houton C, Wood MB. Cellular schwannoma: a clinicopathologic, DNA flow cytometric, and proliferation marker study of 70 patients. Cancer 1995;75:1109-19. PMID 7850709
11: Cayé-Thomasen P, Werther K, Nalla A, et al. VEGF and VEGF receptor-1 concentration in vestibular schwannoma homogenates correlates to tumor growth rate. Otol Neurotol 2005;26(1):98-101. PMID 15699727
12: Cazzador D, Astolfi L, Daloiso A, et al. Tumor microenvironment in sporadic vestibular schwannoma: a systematic, narrative review. Int J Mol Sci 2023;24(7):6522. PMID 37047498
13: Combs SE, Welzel T, Schulz-Ertner D, Huber PE, Debus J. Differences in clinical results after LINAC-based single-dose radiosurgery versus fractionated stereotactic radiotherapy for patients with vestibular schwannomas. Int J Radiat Oncol Biol Phys 2010;76(1):193. PMID 19604653
14: Conti P, Pansini G, Mouchaty H, Capuano C, Conti R. Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol 2004;61(1):34-43; discussion 44. PMID 14706374
15: Cruveilhier J. Anatomie pathologique du corps humain. Paris, 1835-1842;2,26:1-8.
16: Debs P, Luna R, Fayad LM, Ahlawat S. MRI features of benign peripheral nerve sheath tumors: how do sporadic and syndromic tumors differ? Skeletal Radiol 2024;53(4):709-23. PMID 37845504
17: Deruaz JP, Janzer RC, Costa J. Cellular schwannomas of the intracranial and intraspinal compartment: morphological and immunological characteristics compared with classical benign schwannomas. J Neuropathol Exp Neurol 1993;52:114-8. PMID 8095064
18: de Vries WM, Briaire-de Bruijn IH, van Benthem PPG, van der Mey AGL, Hogendoorn PCW. M-CSF and IL-34 expression as indicators for growth in sporadic vestibular schwannoma. Virchows Arch 2019;474(3):375-81. PMID 30580386
19: Dhayalan D, Tveiten ØV, Finnkirk M, et al. Upfront radiosurgery vs a wait-and-scan approach for small- or medium-sized vestibular schwannoma: The V-REX randomized clinical trial. JAMA 2023;330(5):421-31. PMID 37526718
20: Dillard DG, Venkatraman G, Cohen C, Delgaudio J, Gal AA, Mattox DE. Immunolocalization of erythropoietin and erythropoietin receptor in vestibular schwannoma. Acta Otolaryngol 2001;121(2):149-52. PMID 11349767
21: Dilwali S, Roberts D, Stankovic KM. Interplay between VEGF-A and cMET signaling in human vestibular schwannomas and schwann cells. Cancer Biol Ther 2015;16(1):170-5. PMID 25692621
22: Dowling EM, Patel NS, Lohse CM, et al. Durability of hearing preservation following microsurgical resection of vestibular schwannoma. Otol Neurotol 2019;40(10):1363-72. PMID 31725593
23: Doyle EJ, Samy RN. Cochlear implantation: an effective modality for hearing restoration following vestibular schwannoma resection. Curr Opin Otolaryngol Head Neck Surg 2022;30(5):309-13. PMID 36036530
24: Doyle KJ. Is there a role for auditory brainstem response audiometry in the diagnosis of acoustic neuroma? Arch Otolaryngol Head Neck Surg 1999;125(2):232-4. PMID 10037293
25: Dunn IF, Bi WL, Mukandan S, et al. Congress of neurological surgeons systematic review and evidence-based guidelines on the role of imaging in the diagnosis and management of patients with vestibular schwannomas. Neurosurgery 2018;82(2):E32-4.** PMID 29309686
26: Durham AR, Tooker EL, Patel NS, Gurgel RK. Epidemiology and risk factors for development of sporadic vestibular schwannoma. Otolaryngol Clin North Am 2023;56(3):413-20. PMID 37019771
27: Edwards CG, Schwartzbaum JA, Lönn S, Ahlbom A, Feychting M. Exposure to loud noise and risk of acoustic neuroma. Am J Epidemiol 2006;163(4):327. PMID 16357108
28: El-Kashlan HK, Zeitoun H, Arts HA, Hoff JT, Telian SA. Recurrence of acoustic neuroma after incomplete resection. Am J Otol 2000;21:389-92. PMID 10821553
29: El Sayed L, Masmejean EH, Parfait B, Kalamarides M, Biau D, Peyre M. Natural history of peripheral nerve schwannomas. Acta Neurochirurgica 2020;162(8):1883-9. PMID 32556523
30: Farid M, Demicco EG, Garcia R, et al. Malignant peripheral nerve sheath tumors. Oncologist. 2014;19(2):193-201. PMID 24470531
31: Ferner RE, Golding JF, Smith M, et al. [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study. Ann Oncol 2008;19(2):390-4. PMID 17932395
32: Fisher JL, Pettersson D, Palmisano S, et al. Loud noise exposure and acoustic neuroma. Am J Epidemiol 2014;180(1):58-67. PMID 24786799
33: Fisher MJ, Shih CS, Rhodes SD, et al. Cabozantinib for neurofibromatosis type 1-related plexiform neurofibromas: a phase 2 trial. Nature Medicine 2021;27(1):165-73. PMID 33442015
34: Forssen UM, Lonn S, Ahlbom A, Savitz DA, Feychting M. Occupational magnetic field exposure and the risk of acoustic neuroma. Am J Ind Med 2006;49:112-8. PMID 16374820
35: Fujita T, Sakai K, Uehara N, et al. Genetic variants of cancer‑associated genes analyzed using next‑generation sequencing in small sporadic vestibular schwannomas. Oncol Lett 2023;25(3):121. PMID 36844630
36: Goldbrunner R, Weller M, Regis J, et al. EANO guideline on the diagnosis and treatment of vestibular schwannoma. Neuro Oncol 2020;22(1):31-45.** PMID 31504802
37: Gonzalez-Gomez P, Bello MJ, Alonso ME, et al. CpG island methylation in sporadic and neurofibromatosis type 2-associated schwannomas. Clin Cancer Res 2003;9(15):5601-6. PMID 14654541
38: Gormley WB, Sekhar LN, Wright DC, Kamerer D, Schessel D. Acoustic neuromas: results of current surgical management. Neurosurgery 1997;41(1):50-8. PMID 9218295
39: Greene J, Al-Dhahir MA. Acoustic neuroma. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing, 2024. PMID 29262098
40: Gross AM, Wolters PL, Dombi E, et al. Selumetinib in children with inoperable plexiform neurofibromas. N Engl J Med 2020;382(15):1430-42. PMID 32187457
41: Hannan CJ, Lewis D, O'Leary C, et al. The inflammatory microenvironment in vestibular schwannoma. Neurooncol Adv 2020;2(1):vdaa023. PMID 32642684
42: Hardell L, Carlberg M. Mobile phones, cordless phones and the risk for brain tumours. Int J Oncol 2009;35(1):5-17. PMID 19513546
43: Harwalkar JA, Lee JH, Hughes G, et al. Immunoblotting analysis of schwannomin/merlin in human schwannomas. Am J Otol 1998;19:654-9. PMID 9752976
44: Hasegawa T, Kato T, Naito T, et al. Long-term outcomes of sporadic vestibular schwannomas treated with recent stereotactic radiosurgery techniques. Int J Radiat Oncol Biol Phys 2020;108(3):725-33. PMID 32473897
45: Hasegawa T, Kida Y, Kato T, Iizuka H, Kuramitsu S, Yamamoto T. Long-term safety and efficacy of stereotactic radiosurgery for vestibular schwannomas: evaluation of 440 patients more than 10 years after treatment with Gamma Knife surgery. J Neurosurg 2013;118(3):557-65. PMID 23140152
46: Hernandez-Martin A, Duat-Rodríguez A. An update on neurofibromatosis type 1: not just café-au-lait spots, freckling, and neurofibromas. an update. part i. dermatological clinical criteria diagnostic of the disease. Actas Dermosifiliogr 2016;107(6):454-64. PMID 26979265
47: Iijima K, Tosaka M, Nagano T, et al. Oculomotor nerve schwannoma associated with acute hydrocephalus: case report. Neurol Med Chir (Tokyo) 2014;54(8):654-8. PMID 24257488
48: Inoue T, Shima A, Hital H, Suzuki F, Matsuda M. Trochlear nerve schwannoma treated with gamma knife after excision: a case report and review of the literature. J Neurol Surg Rep 2015;76(2):e248-52. PMID 26623236
49: INTERPHONE Study Group. Acoustic neuroma risk in relation to mobile telephone use: results of the INTERPHONE international case-control study. Cancer Epidemiol 2011;35:453-64. PMID 21862434
50: Jia H, Sterkers O, Pavillon-Maisonnier C, et al. Management and outcomes of sporadic vestibular schwannoma: a longitudinal study over 12 years. Laryngoscope 2020;25.** PMID 32710655
51: Kang H, Ji SY, Kim CY, et al. Hearing preservation after stereotactic radiosurgery for sporadic intracanalicular vestibular schwannomas classified as Koos grade 1. Cancer Med 2024;13(2):e6990. PMID 38348957
52: Kano H, Kondziolka D, Khan A, Flickinger JC, Lunsford LD. Predictors of hearing preservation after stereotactic radiosurgery for acoustic neuroma: clinical article. J Neurosurg 2013;119:Suppl 863-73. PMID 25077316
53: Karajannis MA, Hagiwara M, Schreyer M, Haque S. Sustained imaging response and hearing preservation with low-dose bevacizumab in sporadic vestibular schwannoma. Neuro Oncol 2019;21(6):822-4. PMID 31180122
54: Kauser H, Rashid O, Anwar W, Khan S. Orbital oculomotor nerve schwannoma extending to the cavernous sinus: a rare cause of proptosis. J Ophthalmic Vis Res 2014;9(4):514-6. PMID 25709780
55: Khurana VG, Teo C, Kundi M, Hardell L, Carlberg M. Cell phones and brain tumors: a review including the long-term epidemiologic data. Surg Neurol 2009;72(3):205-14. PMID 19328536
56: Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center. J Neurosurg 2005;102:246-55. PMID 15739552
57: Kim IY, Kondziolka D, Niranjan A, Flickinger JC, Lunsford LD. Gamma knife surgery for schwannomas originating from cranial nerves III, IV, and VI. J Neurosurg 2008;109 Suppl:149-53. PMID 19123902
58: Kim SH, Youm JY, Song SH, Kim Y, Song KS. Vestibular schwannoma with repeated intratumoral hemorrhage. Clin Neurol Neurosurg 1998;100:68-74. PMID 9637211
59: Koeller KK, Shih RY. Intradural extramedullary spinal neoplasms: Radiologic-pathologic correlation. Radiographics 2019;39(2):468-90. PMID 30844353
60: Koike H, Nishida Y, Ito S, et al. Diffusion-weighted magnetic resonance imaging improves the accuracy of differentiation of benign from malignant peripheral nerve sheath tumors. World Neurosurgery 2022;157:e207-14. PMID 34624521
61: Koo M, Lai JT, Yang EY, Liu TC, Hwang JH. Incidence of vestibular schwannoma in Taiwan from 2001 to 2012: a population-based national health insurance study. Ann Otol Rhinol Laryngol 2018;127(10):694-7. PMID 30032646
62: Kosaraju N, Moore LS, Mulders JY, Blevins NH. Sporadic vestibular schwannoma in a pediatric population: a case series. Childs Nerv Syst 2024;40(3):635-45. PMID 37889276
63: Koutsimpelas D, Bjelopavlovic M, Yetis R, et al. The VEGF/VEGF-R axis in sporadic vestibular schwannomas correlates with irradiation and disease recurrence. ORL J Otorhinolaryngol Relat Spec 2012;74(6):330-8. PMID 23344215
64: Kshettry VR, Hsieh JK, Ostrom QT, Kruchko C, Barnholtz-Sloan JS. Incidence of vestibular schwannomas in the United States. J Neurooncol 2015;124(2):223-8. PMID 26024654
65: Labit-Bouvier C, Crebassa B, Bouvier C, Andrac-Meyer L, Magnan J, Charpin C. Clinicopathologic growth factors in vestibular schwannomas: a morphological and immunohistochemical study of 69 tumours. Acta Otolaryngol 2000;120(8):950-4. PMID 11200590
66: Lazak J, Betka J, Zverina E, et al. Quality of life in patients after vestibular schwannoma surgery. Acta Neurochir (Wien) 2024;166(1):33. PMID 38270649
67: Lee LR, Gigantelli JW, Kincaid MC. Localized neurofibroma of the orbit. A radiographic and histopathologic study. Ophthal Plastic Reconstruc Surg 2000;16:241-6. PMID 10826767
68: Lin D, Hegarty JL, Fischbein NJ, Jackler RK. The prevalence of "incidental" acoustic neuroma. Arch Otolaryngol Head Neck Surg 2005;131(3):241-4. PMID 15781765
69: Litwiniuk-Kosmala M, Makuszewska M, Niemczyk K, Bartoszewicz R, Wojtas B, Gielniewski B. High-throughput RNA sequencing identifies the miRNA expression profile, target genes, and molecular pathways contributing to growth of sporadic vestibular schwannomas. Acta Neurochir (Wien) 2024;166(1):71. PMID 38329606
70: Louis DN, Perry A, Reifenberger G, et al. The 2016 World Health Organization Classification of tumors of the central nervous system: a summary. Acta Neuropathol 2016;131(6):803-20.** PMID 27157931
71: Louis DN, Perry A, Wesseling P, et al. The 2021 World Health Organization Classification of tumors of the central nervous system: a summary. Neuro Oncol 2021;23(8):1231-51.** PMID 34185076
72: Lovin BD, Wilkinson AJ, Qing Y, et al. The effect of metformin on vestibular schwannoma growth: a systematic review and meta-analysis. Laryngoscope 2023;133(9):2066-72. PMID 36744870
73: Lu VM, Ravindran K, Graffeo CS, et al. Efficacy and safety of bevacizumab for vestibular schwannoma in neurofibromatosis type 2: a systematic review and meta-analysis of treatment outcomes. J Neurooncol 2019;144(2):239-48. PMID 31254266
74: Macfarlane R, King TT. Acoustic neurinomas (vestibular schwannoma). In: Kaye AH, Laws ER, editors. Brain tumors. An encyclopedic approach. Edinburgh: Churchill Livingstone, 1995;31:577-622.
75: Machetanz K, Wang SS, Oberle L, Tatagiba M, Naros G. Sex differences in vestibular schwannoma. Cancers (Basel) 2023;15(17):4365. PMID 37686642
76: Macielak RJ, Lohse CM, Wallerius KP, et al. The effect of age on facial nerve recovery after vestibular schwannoma resection. Otol Neurotol 2023;44(7):725-9. PMID 37400264
77: Macielak RJ, Patel NS, Lees KA, et al. Delayed tumor growth in vestibular schwannoma: an argument for lifelong surveillance. Otol Neurotol 2019;40(9):1224-9. PMID 31469794
78: Mahboubi H, Slattery WH 3rd, Miller ME, Lekovic GP. Comparison of Surgeons' Assessment of the extent of vestibular schwannoma resection with immediate post operative and follow-up volumetric MRI analysis. Brain Sci 2023;13(10):1490. PMID 37891857
79: Malina GEK, Heiferman DM, Riedy LN, et al. Pediatric vestibular schwannomas: case series and a systematic review with meta-analysis. J Neurosurg Pediatr 2020;1-9. PMID 32470932
80: Marinelli JP, Beeler CJ, Carlson ML, Caye-Thomasen P, Spear SA, Erbele ID. Global incidence of sporadic vestibular schwannoma: a systematic review. Otolaryngol Head Neck Surg 2022;167(2):209-14. PMID 34464224
81: Marinelli JP, Herberg HA, Moore LS, et al. Salvage microsurgery following failed primary radiosurgery in sporadic vestibular schwannoma. JAMA Otolaryngol Head Neck Surg 2024;150(4):287-94. PMID 38358763
82: Marinelli JP, Lohse CM, Grossardt BR, Lane JI, Carlson ML. Rising incidence of sporadic vestibular schwannoma: true biological shift versus simply greater detection. Otol Neurotol 2020;41(6):813-47. PMID 32150020
83: Marioni G, Blandamura S, Nicolè L, et al. Endoglin-based assessment of neoangiogenesis in sporadic VIII cranial nerve schwannoma. Pathol Res Pract 2019;215(11):152648. PMID 31582184
84: Martin J, Kondziolka D, Flickinger JC, Mathieu D, Niranjan A, Lunsford LD. Cranial nerve preservation and outcomes after stereotactic radiosurgery for jugular foramen schwannomas. Neurosurg 2007;61:76-81. PMID 17621021
85: Matthies C, Samii M. Management of 1000 vestibular schwannomas (acoustic neuromas): clinical presentation. Neurosurgery 1997a;40:1-10. PMID 9092842
86: McClenaghan F, Freeman S, Lloyd S, Stapleton E. Cochlear implantation in sporadic vestibular schwannoma and neurofibromatosis type II. Otolaryngol Clin North Am 2023;56(3):587-98. PMID 37019773
87: McCormick PC, Bello JA, Post KD. Trigeminal schwannoma. Surgical series of 14 cases with review of the literature. J Neurosurg 1988;69:850-60. PMID 3057125
88: Miller LE, Brant JA, Naples JG, Bigelow DC, Lee JYK, Ruckenstein MJ. Quality of Life in Vestibular Schwannoma Patients: A Longitudinal Study. Otology & Neurotology. 2020;41(2):e256-e61.
89: Moore LS, Stankovic KM. The future of vestibular schwannoma management. Otolaryngol Clin North Am 2023;56(3):611-22. PMID 37019772
90: Mornet E, Kania R, Sauvaget E, Herman P, Tran Ba Huy P. Vestibular schwannoma and cell-phones. Results, limits and perspectives of clinical studies. Eur Ann Otorhinolaryngol Head Neck Dis 2013;130(5):275-82. PMID 23725662
91: Moshtaghi O, Dixon PR, Claussen AD, et al. The effect of immediate microsurgical resection of vestibular schwannoma on hearing preservation. Otol Neurotol 2023;44(6):600-4. PMID 37205868
92: Moulin G, Dessi P, Andre P, et al. Role of magnetic resonance imaging in predicting late facial motor function after removal of vestibular schwannomas by the translabyrinthine approach. J Laryngol Otol 1995;109(5):394-8. PMID 7797994
93: Mousavi SH, Niranjan A, Akpinar B, et al. Hearing subclassification may predict long-term auditory outcomes after radiosurgery for vestibular schwannoma patients with good hearing. J Neurosurg 2016;125(4):845-52. PMID 26745482
94: Murphy ES, Suh JH. Radiotherapy for vestibular schwannomas: a critical review. Int J Radiat Oncol Biol Phys 2011;15:985-97. PMID 21353158
95: Pendleton C, Everson MC, Puffer RC, Spinner RJ. Personal and familial malignancy history in patients with malignant peripheral nerve sheath tumors with a focus on sporadic tumors. World Neurosurgery 2020;141:e778-e82. PMID 32526361
96: Pilavaki M, Chourmouzi D, Kiziridou A, Skordalaki A, Zarampoukas T, Drevelengas A. Imaging of peripheral nerve sheath tumors with pathologic correlation: pictorial review. Eur J Radiol 2004;52(3):229-39. PMID 15544900
97: Pirouzmand F, Tator CH, Rutka J. Management of hydrocephalus associated with vestibular schwannoma and other cerebellopontine angle tumors. Neurosurg 2001;48:1246-54. PMID 11383726
98: Plotkin SR, Stemmer-Rachamimov AO, Barker FG, et al. Hearing improvement after bevacizumab in patients with neurofibromatosis type 2. New Engl J Med 2009;361:358-67. PMID 19587327
99: Pollock BE, Driscoll CLW, Foote FL, et al. Patient outcomes after vestibular schwannoma management: A prospective comparison of microsurgical resection and stereotactic radiosurgery. Neuorsurg 2006;59:77-85. PMID 16462477
100: Pollock BE, Foote RL, Stafford SL. Stereotactic radiosurgery: the preferred management for patients with nonvestibular schwannomas. Int J Radiat Oncol Biol Phys 2002;52:1002-7. PMID 11958895
101: Preet K, Ong V, Sheppard JP, et al. Postoperative hearing preservation in patients undergoing retrosigmoid craniotomy for resection of vestibular schwannomas: A systematic review of 2034 patients. Neurosurgery 2020;86(3):332-42. PMID 31149722
102: Prochazka M, Feychting M, Ahlbom A, et al. Occupational exposures and risk of acoustic neuroma. Occup Environ Med 2010;67(11):766-71. PMID 20581419
103: Propp JM, McCarthy BJ, Davis FG, Preston-Martin S. Descriptive epidemiology of vestibular schwannomas. Neuro-Oncol 2006;8:1-11. PMID 16443943
104: Pulec JL. Acoustic neuroma surgery in geriatric patients. Ear Nose Throat J 1999;78(6):429. PMID 10388194
105: Ren Y, Chari DA, Vasilijic S, Welling DB, Stankovic KM. New developments in neurofibromatosis type 2 and vestibular schwannoma. Neurooncol Adv 2020;3(1):vdaa153. PMID 33604573
106: Rocchi G, Artico M, Lunardi P, Gagliardi FM. Intracranial schwannoma of the facial nerve: report of two cases and review of the literature. Neurochir 1991;34:180-3. PMID 1775209
107: Roos DE, Potter AE, Zacest AC. Hearing preservation after low dose linac radiosurgery for acoustic neuroma depends on initial hearing and time. Radiother Oncol 2011;101(3):420-4. PMID 21741718
108: Russell DS, Rubinstein LJ. Pathology of tumours of the nervous system. 5th ed. Baltimore: Williams & Wilkins, 1989:533-89.
109: Safavi-Abbasi S, Senoglu M, Theodore N, et al. Microsurgical management of spinal schwannomas: evaluation of 128 cases. J Neurosurg Spine 2008;9(1):40-7. PMID 18590409
110: Samii M, Matthies C. Management of 1000 vestibular schwannomas (acoustic neuromas): surgical management and results with an emphasis on complications and how to avoid them. Neurosurgery 1997;40:11-23. PMID 8971819
111: Samii M, Tatagiba M, Matthies C. Acoustic neurinoma in the elderly: factors predictive of postoperative outcome. Neurosurgery 1992;31(4):615-9. PMID 1407445
112: Sanguinetti C, Specchia N, Gigante A, de Palma L, Greco F. Clinical and pathological aspects of solitary spinal neurofibroma. J Bone Joint Surg 1993;75B:141-7. PMID 8421013
113: Schneider AB, Ron E, Lubin J, et al. Acoustic neuromas following childhood radiation treatment for benign conditions of the head and neck. Neuro Oncol 2008;10(1):73-8. PMID 18079359
114: Schouten SM, Cornelissen S, Langenhuizen PPHJ, et al. Wait-and-scan management in sporadic Koos grade 4 vestibular schwannomas: A longitudinal volumetric study. Neurooncol Adv 2023;6(1):vdad144. PMID 38187870
115: Schuz J, Steding-Jessen M, Hansen S, et al. Long-term mobile phone use and the risk of vestibular schwannoma: a Danish nationwide cohort study. Am J Epidemiol 2011;174:416-22. PMID 21712479
116: Seppala MT, Haltia MJ, Sankila RJ, Jaaskelainen JE, Heiskanen O. Long-term outcome after removal of spinal neurofibroma. J Neurosurg 1995a;82:572-7. PMID 7897516
117: Seppala MT, Haltia MJ, Sankila RJ, Jaaskelainen JE, Heiskanen O. Long-term outcome after removal of spinal schwannoma: a clinicopathological study of 187 cases. J Neurosurg 1995b;83:621-6. PMID 7674010
118: Shah KJ, Chamoun RB. Large vestibular schwannomas presenting during pregnancy: management strategies. J Neurol Surg B Skull Base 2014;75(3):214-20. PMID 25072015
119: Sheehan JP, Kano H, Xu Z, et al. Gamma knife radiosurgery for facial nerve schwannomas: a multicenter study. J Neurosurg 2015;123(2):387-94. PMID 25955875
120: Singh RV, Suys S, Campbell DA, Broome JC. Malignant schwannoma of the cerebellum: case report. Surg Neurol 1993;39:128-32. PMID 8351625
121: Skolnik AD, Loevner LA, Sampathu DM, et al. Cranial nerve schwannomas: diagnostic imaging approach. Radiographics 2016;36(5):1463-77. PMID 27541436
122: Skovronsky DM, Oberholtzer JC. Pathologic classification of peripheral nerve tumors. Neurosurg Clin N Am 2004;15(2):157-66. PMID 15177315
123: Smirniotopoulos JG, Yue NC, Rushing EJ. Cerebellopontine angle masses: radiologic-pathologic correlation. Radiographics 1993;13:1131-47. PMID 8210595
124: Smouha EE, Yoo M, Mohr K, Davis RP. Conservative management of acoustic neuroma: a meta-analysis and proposed treatment algorithm. Laryngoscope 2005;115(3):450-4. PMID 15744156
125: Strauss R, Post KD. Other schwannomas of cranial nerves. In: Kaye AH, Laws ER, editors. Brain tumors. An encyclopedic approach. Edinburgh: Churchill Livingstone, 1995;33:643-64.
126: Sughrue ME, Kane AJ, Kaur R, et al. A prospective study of hearing preservation in untreated vestibular schwannomas. J Neurosurg 2011b;114(2):381-5. PMID 20486891
127: Sughrue ME, Yang I, Aranda D, et al. The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes. J Neurosurg 2010;112(1):163-7. PMID 19538047
128: Sughrue ME, Yang I, Aranda D, et al. Beyond audiofacial morbidity after vestibular schwannoma surgery. J Neurosurg 2011c;114(2):367-74. PMID 19943734
129: Sweeney AD, Carlson ML, Ehtesham M, et al. Surgical approaches for vestibular schwannoma. Curr Otorhinolaryngol Rep 2014;2:256-64.
130: Sylvester MJ, Shastri DN, Patel VM, et al. Outcomes of Vestibular schwannoma surgery among the elderly. Otolaryngol Head Neck Surg 2017;156(1):166-72. PMID 28045630
131: Taha JM, Tew JM, van Lovern HR, Keller JT, El-Kalliny M. Comparison of conventional and skull base surgical approaches for the excision of trigeminal neurinomas. J Neurosurg 1995;82:719-25. PMID 7714595
132: Takahara K, Tamura R, Kuranari Y, Karatsu K, Akiyama T, Toda M. Prognostic significance of preoperative neutrophil-to-lymphocyte ratio in surgically resected schwannomas. Front Oncol 2023;13:1099384. PMID 36845735
133: Thai NLB, Mai NY, Vuong NL, et al. Treatment for vestibular schwannoma: Systematic review and single arm meta-analysis. Am J Otolaryngol 2022;43(2):103337. PMID 34973662
134: Tiwari R, Singh AK. Neurofibromatosis Type 2. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing, 2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470350/.
135: Vakharia K, Hasegawa H, Graffeo C, et al. Predictive value of K i -67 index in evaluating sporadic vestibular schwannoma recurrence: systematic review and meta-analysis. J Neurol Surg B Skull Base 2022;84(2):119-28. PMID 36895813
136: Vasilijic S, Atai NA, Hyakusoku H, et al. Identification of immune-related candidate biomarkers in plasma of patients with sporadic vestibular schwannoma. Sci Adv 2023;9(45):eadf7295. PMID 37948527
137: Von Monakow. Eber neurofibroma der hinteren schadelgrube. Berl Klin Wsachr 1900;37:721-4.
138: Vorasubin N, Sang U H, Mafee M, Nguyen QT. Glossopharyngeal schwannomas: a 100 year review. Laryngoscope 2009;119(1):26-35. PMID 19117318
139: Wasa J, Nishida Y, Suzuki Y, et al. Differential expression of angiogenic factors in peripheral nerve sheath tumors. Clin Exp Metastasis 2008;25(7):819-25. PMID 18679811
140: Weber DC, Chan AW, Bussiere MR, et al. Proton beam radiosurgery for vestibular schwannoma: Tumor control and cranial nerve toxicity. Neurosurg 2003;53(3):577-86. PMID 12943574
141: Weiss BD, Wolters PL, Plotkin SR, et al. NF106: A neurofibromatosis clinical trials consortium phase II trial of the MEK inhibitor mirdametinib (PD-0325901) in adolescents and adults with NF1-related plexiform neurofibromas. J Clin Oncol 2021;39(7):797-806. PMID 33507822
142: Well L, Salamon J, Kaul MG, et al. Differentiation of peripheral nerve sheath tumors in patients with neurofibromatosis type 1 using diffusion-weighted magnetic resonance imaging. Neuro Oncol 2019;21(4):508-16. PMID 30496452
143: Welling DB, Packer MD, Chang LS. Molecular studies of vestibular schwannomas: a review. Curr Opin Otolaryngol Head Neck Surg 2007;15:341-6. PMID 17823551
144: West NC, Groth JB, Cayé-Thomasen P. Does location of intralabyrinthine vestibular schwannoma determine objective and subjective vestibular function? Otol Neurotol 2024a;45(3):319-25. PMID 38291789
145: West NC, Sørensen RS, Kressner AA, Bille M, Marozeau J, Cayé-Thomasen P. Cochlear implantation in sporadic intralabyrinthine schwannomas with single-sided deafness: implications for binaural hearing. Otol Neurotol 2024b;45(2):128-35. PMID 38206060
146: Williams EA, Ravindranathan A, Gupta R, et al. Novel SOX10 indel mutations drive schwannomas through impaired transactivation of myelination gene programs. Neuro Oncol 2023;25(12):2221-36. PMID 37436963
147: Wilson MP, Katlariwala P, Low G, et al. Diagnostic accuracy of MRI for the detection of malignant peripheral nerve sheath tumors: A systematic review and meta-analysis. AJR Am J Roentgenol 2021;217:31-9. PMID 33909462
148: Xu J, Zhang Y, Shi Y, et al. CPI-17 overexpression and its correlation with the NF2 mutation spectrum in sporadic vestibular schwannomas. Otol Neurotol 2020;41(1):e94-e102. PMID 31789805
149: Yao L, Alahmari M, Temel Y, Hovinga K. Therapy of sporadic and NF2-related vestibular schwannoma. Cancers 2020;12(4):835. PMID 32244314
150: Young ED, Ingram D, Metcalf-Doetsch W, Khan D, Al Sannaa G, Le Loarer F. Clinicopathological variables of sporadic schwannomas of peripheral nerve in 291 patients and expression of biologically relevant markers. J Neurosurg 2018;129(3):805-14. PMID 28885122
151: Zipfel J, Al-Hariri M, Gugel I, et al. Surgical management of peripheral nerve sheath tumours in children, with special consideration of neurofibromatoses. Childs Nervous System 2020;36(10):2433-42. PMID 32506255

Contributors

All contributors' financial relationships have been reviewed and mitigated to ensure that this and every other article is free from commercial bias.

Authors

Stefania Maraka MD

Dr. Maraka of University of Illinois Brain Tumor Center has no relevant financial relationships to disclose.
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Mariam/Myriam Markouli MD

Dr. Markouli of Boston University has no relevant financial relationships to disclose.
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Editor

Rimas V Lukas MD

Dr. Lukas of Northwestern University Feinberg School of Medicine received honorariums from Novartis and Novocure for speaking engagements, honorariums from Cardinal Health, Novocure, and Merck for advisory board membership, and research support from BMS as principal investigator.
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Former Authors

Herbert B Newton MD
Joel Neves Briard MD MSc
Sarah Lapointe MD

Patient Profile

Age range of presentation: 19 to 65+ years
Sex preponderance: female>male, >1:1
Heredity: none
Population groups selectively affected: none selectively affected
Occupation groups selectively affected: none selectively affected

ICD & OMIM codes

ICD-10: Malignant neoplasm of connective and other soft tissue site unspecified: C49.9

Benign neoplasm of cranial nerves: D33.3
ICD-11: Schwannoma, NOS: XH98Z3

Neurofibroma, NOS: XH87J5
ICD-O: Neurofibroma, NOS: M9540/0

Schwannoma, NOS: M9560/0

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Sporadic schwannomas and neurofibromas

Associated Disorders

Acoustic neuroma

Differential Diagnosis

other primary cerebellopontine angle tumors
cysts
vascular malformations
aberrant normal vascular structures
metastatic lesions
- meningiomas
- epidermoid inclusion cyst
- arachnoid cyst
- exophytic brainstem gliomas
- ependymomas
- choroids plexus papillomas
- schwannomas of cranial nerve 9
- schwannomas of cranial nerve 5
- schwannomas of cranial nerve 7
- schwannomas of cranial nerve 10
- schwannomas of cranial nerve 11
- jugular foramen paragangliomas
- lipomas
- metastases
- aneurysm
- malformations
- aberrant loops of normal blood vessels
- tuberculomas
- cysticercosis
- Meniere disease
- vestibular tumors
- chondromas
- chordomas
- astrocytomas
- dermoids
- teratomas
- syringomyelia
- multiple sclerosis
- transverse myelitis
- spondylosis
- herniated disc
- infection
- Lyme disease
- syphilis
- malignant peripheral nerve sheath tumors
- desmoid tumors
- granular cell tumors
- nerve sheath myxomas
- lymphangiomas
- myoblastomas

Also Relevant

Molecular diagnosis of brain tumors
Neurofibromatosis 1
Neurofibromatosis 2
Noise-induced hearing loss
Radiation plexopathy
- Subjective tinnitus
- Tumors of the skull base
- Vestibular schwannoma

Sporadic schwannomas and neurofibromas

Introduction

Overview

Key points

Historical note and terminology

Clinical manifestations

Presentation and course

Clinical vignette

Biological basis

Etiology and pathogenesis

Epidemiology

Prevention

Differential diagnosis

Table 1. Radiological Differential Diagnosis of a Cerebellopontine Angle Lesion

Diagnostic workup

Table 2. Radiological Findings in Sporadic Schwannomas and Neurofibromas

Management

Outcomes

Special considerations

Pregnancy

Anesthesia

Media

References

Contributors

Authors

Editor

Former Authors

Patient Profile

ICD & OMIM codes

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Questions or Comment?

Also in This Category

NF2-related schwannomatosis

Tumors of the skull base

Common maculopathies

Toxic and nutritional deficiency optic neuropathies

Third nerve palsy

Nystagmus

Chronic progressive external ophthalmoplegia

Ganglioglioma

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