Spatial organization of muscular structures within the orbit in the presence of accessory rectus muscles or muscular bands between superior and inferior rectus muscles

Schematic drawings simulating MRI or CT coronal scans demonstrating spatial organization of muscular structures within the orbit in the event of the presence of accessory (supernumerary) rectus muscles or muscular bands between superior and inferior rectus muscles. The drawings were prepared based on a comparison of different MRI scans presented by Khitri, Dremer, and Kighlinger and colleagues (Khitri and Dremer 2010; Kightlinger et al 2017).

(a) Complete muscular bridge seen between temporal edges of superior and inferior rectus muscles (marked by grey arrowheads). On drawing (b) only fragments of certain heads of the supernumerary rectus were captured (grey arrowheads). Abbreviations: IR, inferior rectus muscle; LR, lateral rectus muscle; LPS, levator palpebrae superioris muscle; MR, medial rectus muscle; SR, superior rectus; SO, superior oblique muscle; II, optic nerve.

(Source: Haładaj R, Wysiadecki G, Polguj M, Topol M. Bilateral muscular slips between superior and inferior rectus muscles: case report with discussion on classification of accessory rectus muscles within the orbit. Surg Radiol Anat 2018;40(7):855-62. Creative Commons Attribution 4.0 International [CC BY 4.0] license, creativecommons.org/licenses/by/4.0.)

References cited:
Khitri MR, Demer JL. Magnetic resonance imaging of tissues compatible with supernumerary extraocular muscles. Am J Ophthalmol 2010;150[6]:925-31.

Kightlinger BS, Saraf-Lavi E, Sidani C. Anomalous extraocular muscles: a case series of orbital bands connecting the superior rectus to inferior rectus. Neurographics 2017;7[2]:88-91.)