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HEAD & NECK ABBREVIATION KEY EOM ⫽ extraocular muscle Received July 26, 2015; accepted December 11, 2015. Anomalous Extraocular Muscles: A Case Series of Orbital Bands Connecting the Superior Rectus to Inferior Rectus B.S. Kightlinger, E. Saraf-Lavi, and C. Sidani From the Department of Medicine (B.S.K., E.S.-L., C.S.), University of Miami Miller School of Medicine, Miami, Florida. Presented at: Annual Meeting of the American Society of Neuroradiology, April 25–30, 2015; Chicago, Illinois. Please address correspondence to Blake Kightlinger, MD, Department of Radiology, Shady Grove Medical Center, 9901 Medical Center Dr, Rockville, MD 20850; e-mail: [email protected] http://dx.doi.org/10.3174/ng.2170192 ABSTRACT Orbital bands are rarely reported abnormal connections of tissue that bridge extraocular muscles and/or the globes. A series of 7 cases of orbital bands that bridged the superior and inferior rectus muscles were reviewed. The bands in this small series were discovered as incidental findings, with no relation to the patients’ symptoms and, therefore, may have been of no clinical significance. INTRODUCTION The normal human orbit contains 6 extraocular muscles (EOM), the levator palpebrae superioris muscle, and the orbicularis oculi muscle. Numerical aberrations of the EOMs (also known as accessory EOMs or supernumerary EOMs) are rare. Orbital bands are a heterogeneous group of structures that include acquired conditions of posttraumatic and/or surgical adhesions as well as congenital anomalous muscular or fibrous structures. There are 3 types of orbital bands: anomalous bands of muscle bridging 2 muscles,1 fibrous tissues adjacent to the muscles that may attach to the globe,2 and muscles that arise from the posterior orbit and insert on the globe or extraocular muscles.3 Orbital bands have rarely been reported in the ophthalmologic literature, and only 1 report, by Dobbs et al,4 was found in the radiology literature; Dobbs et al4 describes a case of an 8-year-old boy with Gorlin syndrome and unilateral strabismus who was found, on computerized tomography (CT), to have bilateral anomalous EOMs, which extended from the orbital apex to the posterior globe. A case series by Khitri and De88 兩 mer1 describes various bands that connect the superior to inferior rectus, medial to lateral rectus, lateral to inferior rectus, inferior rectus to the globe, and the superior rectus to superior oblique muscles. The clinical significance of orbital bands is uncertain and possibly depends on size and location. Often they are found incidentally in autopsy or for workup of nonassociated visual symptoms. However, there is an increased incidence of orbital bands in patients with restrictive strabismus, globe retraction, and eyelid retraction.5-7 Khitri and Demer1 found that the incidence of orbital bands in normal adult orthotropic subjects who underwent orbital MRI was 0.8%, whereas patients with strabismus had a higher incidence of 2.4%. Orbital bands have also been reported to be associated with rare entities, including GomezLopez-Hernandez syndrome8 and Duane syndrome.1,9 Most of the early reported cases of orbital bands were discovered at autopsy, surgical exploration, or CT.2,4,5 The increasing universal utilization of high-resolution orbital MRI has significantly improved the noninvasive visualization of these structures. Orbital bands have Neurographics 2017 March/April; 7(2):88 –91; www.neurographics.org Disclosures Based on information received from the authors, Neurographics has determined that there are no Financial Disclosures or Conflicts of Interest to report. Table: Patient characteristics Case No. Age, y Sex Clinical Indication 1 52 F Thyroid orbitopathy 2 33 M Trauma 3 22 F Sinusitis Modality Side TV, mm AP, mm CC, mm CT orbits Right 3.6 15.0 15.9 MRI orbits w/o ⫹ w Right 2.7 10.6 15.3 Left 3.0 7.5 16.6 Right 2.0 7.4 13.8 Left 2.4 6.8 14.6 CT sinus 4 14 F Papilledema MRI orbits w/o ⫹ w Right 2.1 9.4 10.6 5 39 F Esotropia MRI orbits w/o Right 2.1 8.0 15.7 Left 1.3 10.5 17.9 6 53 M Papilledema MRI orbits w/o ⫹ w Left 1.9 12.7 16.9 7 44 F Optic neuropathy MRI orbits w/o ⫹ w Right 2.1 8.9 10.6 Left 2.7 8.5 11.7 Note:—TV indicates transverse; AP, anteroposterior; CC, craniocaudal; w/o, without IV contrast; w, with IV contrast. Fig 1. Coronal (A) and axial (B) T1-weighted MRI orbits in a 39-year-old female patient evaluated for esotropia with bilateral orbital bands connecting the superior and inferior recti. Note:—IR indicates inferior rectus; LR, lateral rectus; MR, medial rectus; ON, optic nerve; SO, superior oblique; SR-LPS, superior rectus–levator palpebrae superioris). now been described in the ophthalmology literature on both CT and MRI. Although Dobbs et al4 describes the first case of orbital bands on CT in the radiology literature, we present, to our knowledge, the first case series of orbital bands discovered on both CT and MRI in the radiology literature. METHODS Institutional review board approval was obtained according to the protocol set forth by the institutional review board of the University of Miami and in accordance with the Health Insurance Portability and Accountability Act. Seven patients with orbital bands seen anecdotally on MRI and/or CT of the orbits were reviewed from 2011 to 2014 from a single institution. Imaging protocols are as detailed: MRI orbits: Precontrast: axial T1-weighted, T1-weighted fat saturation; coronal T1-weighted, T1weighted fat saturation, T2-weighted fat saturation. Postcontrast: axial and coronal T1-weighted, T1weighted fat saturation. Axial images 3 mm thickness; coronal images 3.5 mm thickness. CT sinus: No IV contrast. Axial, coronal, and sagittal images 3 mm thickness. Bone and soft tissue algorithm. CT orbits: No IV con- trast. Axial, coronal, and sagittal images 3mm thickness. Bone and soft tissue algorithm. FINDINGS The 7 subjects included 2 men and 5 women with an age range of 14 to 53 years and an average age of 37 years (Table). All 7 subjects had bands that connected the temporal edge of the superior and inferior rectus muscles coursing lateral to the optic nerve (Fig 1). The bands were found to be similar to EOMs in attenuation on CT and in intensity and enhancement on all MR pulse sequences (Fig 2). However, the bands were smaller in size than EOMs. Five of the cases were found on MRI, 2 on CT. Bilateral bands were seen in 4 patients. Reasons for initial imaging evaluation included thyroid orbitopathy, trauma, sinusitis, papilledema, esotropia, and optic neuropathy. DISCUSSION Orbital bands or accessory EOMs are rarely reported entities where there exists an abnormal connection of tissue connecting the EOMs, the globes,2 and/or the orbital walls.3 A variety of different forms of orbital bands have Neurographics 2017 March/April; 7(2):88 –91; www.neurographics.org 兩 89 been described. However, all 7 cases in our series were bands that connected the temporal edge of the superior and inferior rectus muscles. In the study by Khitri and Demer,1 the superior rectus–inferior rectus band was only seen in 33% of all types of bands. Even though we presented the first cases of superior rectus–inferior rectus band in the radiology literature, this particular form of band was described by several anatomists in the early 1900s.3,10,11 Although our case series lacks statistical power, there does not seem to be any trend for the superior rectus– Fig 2. Coronal T1-weighted postcontrast MRI of the orbits with fat suppression in a 33-year-old male patient evaluated for trauma with bilateral orbital bands that enhance similarly to normal EOMs. Note:—IR indicates inferior rectus; LR, lateral rectus; MR, medial rectus; ON, optic nerve; SO, superior oblique; SR-LPS, superior rectus–levator palpebrae superioris. inferior rectus band to be more common bilaterally or to be in either the right or left orbit. In our series, most subjects were female patients, but it is unclear if there was any statistical predilection of this finding in female patients. In most of our cases, the orbital bands were found on MRI; however, at most institutions, CT sinuses will be performed in greater volume than MRI orbits. This is likely due to the greater soft-tissue detail with MR and to the fact that MRI is the technique of choice in imaging of the patients with a question of orbital pathology. As seen in our cases, orbital bands are usually similar in signal intensity and/or attenuation to normal EOMs on MRI and CT, although smaller in bulk. They have been reported to be more visible on imaging of patients with thyroid orbitopathy,1,12 and, in our series, 1 subject (case 1) had this diagnosis (Fig 3). Although similar in appearance to EOMs, orbital bands may also be confused as normal arteries or veins or as pathology such as lymphoma, orbital pseudotumor, venolymphatic malformations, sarcoid, or metastasis. Orbital bands should not be confused with the normal lateral rectus–superior rectus band or the lateral levator aponeurosis connecting the levator muscle to the lacrimal gland. Degeneration of the lateral rectus–superior rectus band has been implicated with 2 forms of strabismus, heavy eye syndrome, and sagging eye syndrome.13,14 Examples of the normal course and appearance of the lateral rectus–superior rectus band with a normal arc-like shape, and no discontinuities are shown in Fig 4. Degen- Fig 3. Coronal (A) and sagittal (B) CT orbits in a 52-year-old female patient with thyroid orbitopathy reveals unilateral right orbital band connecting the superior and inferior recti. Note the enlarged right medial rectus muscle. Note:—IR indicates inferior rectus; LR, lateral rectus; MR, medial rectus; ON, optic nerve; SR, superior rectus. Fig 4. Two coronal (A, B) T1-weighted MRI orbits in a patient, demonstrating the normal anatomic lateral rectus–superior rectus (LR-SR) band. Note:—IR, inferior rectus; LR, lateral rectus; MR, medial rectus; SO, superior oblique; SR-LPS, superior rectus–levator palpebrae superioris; ON, optic nerve. 90 兩 Neurographics 2017 March/April; 7(2):88 –91; www.neurographics.org eration of the lateral rectus–superior rectus band is suggested by bowing of the structure lateral to the lateral rectus and/or superior to the superior rectus or having discontinuity within the band. Two theories exist on the development of these anomalies. Some researchers believe that orbital bands are an evolutionary remnant of an atavistic retractor bulbi muscle.3 This muscle, found in some mammals, reptiles, and amphibians, allows retraction of the globe into the orbital cavity for protection. However, the described atavistic retractor bulbi muscles have either a cone shape or multiple tendon slips that originate at the orbital apex and extend to surround the optic nerve region.15 Our cases of superior rectus–inferior rectus bands, instead, had a vertical orientation without approximating the orbital apex or optic nerve. Also, the rectractor bulbi has been described to be innervated by the abducens nerve,15 whereas many orbital bands are found to be innervated by branches of the oculomotor nerve.2 The other theory is that accessory EOMs develop from an embryologic disturbance in the mesodermal development of the extraocular muscles.16 This is consistent with the reported case by Dobbs et al4 of an orbital band in a patient with Gorlin syndrome in whom there was a mutation in the coding for sonic hedgehog protein, a ligand involved in induction and promotion of muscle development. Although many patients with orbital bands have no visual symptoms, they have a higher prevalence in people with strabismus among other conditions. The association with strabismus is complex. Bands were found to be additional findings in neuropathic forms of strabismus in patients with cranial dysinnervation syndromes1 and, therefore, were noncontributory to the strabismus symptoms. However, additional reports describe cases in which the bands were found to be the cause of a restrictive strabismus.5-7 Although 2 of our 7 cases had papilledema as their presenting symptom, the remaining other 5 cases had dissimilar clinical indications. One of the patients presented with esotropia, and whereas strabismus has been associated with the presence of some forms of orbital bands, we believe that the form of band found in our series would be unlikely to contribute to a medially deviated globe because the band connects the superior and inferior rectus muscle and does not affect the medial or lateral rectus muscles that contribute to horizontal gaze movements. CONCLUSION The bands in this small series were discovered as incidental findings with no relation to the patient’s symptoms and, therefore, may be of no clinical significance. Given the continued growth in utilization of MRI, it can be expected that there will be an increase in the diagnosis of orbital bands in the general population. Awareness of orbital bands by radiologists will improve their detection. Knowledge also helps radiologists avoid the pitfall for describing a suspi- cious orbital lesion, especially when unilateral, with unnecessary workup for an unrelated symptom. Although bands are most commonly an incidental finding that should not be mistaken for pathology, occasionally, it is an important contributing factor in patients with strabismus. In these cases, the accurate description of orbital bands can guide surgeons in their anatomic approach and ultimately improve patient outcomes. REFERENCES 1. Khitri MR, Demer JL. Magnetic resonance imaging of tissues compatible with supernumerary extraocular muscles. Am J Ophthalmol 2010;150:925–31. 10.1016/j.ajo.2010.06.007 2. von Ldinghausen M. Bilateral supernumerary rectus muscles of the orbit. Clin Anat 1998;11:271–77 3. Whitnall SE. An instance of the retractor bulbi muscle in man. J Anat Physiol 1911;46:36 – 40 4. Dobbs MD, Mawn LA, Donahue SP. Anomalous extraocular muscles with strabismus. AJNR Am J Neuroradiol 2011;32: E167– 68. 10.3174/ajnr.A2291 5. Wylen EL, Brown MS, Rich LS, et al. Supernumerary orbital muscle in congenital eyelid retraction. Ophthalmic Plastic Reconstr Surg 2001;17:120 –22. 10.1097/00002341-20010300000008 6. Ozkan SB, Cakmak H, Dayanir V. Fibrotic superior oblique and superior rectus muscle with an accessory tissue band. J AAPOS 2007;11:491–94. 10.1016/j.jaapos.2007.05.005 7. Valmaggia C, Zaunbauer W, Gottlob I. Elevation deficit caused by accessory extraocular muscle. Am J Ophthalmol 1996;121:444 – 45. 10.1016/S0002-9394(14)70445-3 8. Belliveau MJ, Arthur BW. Orbital bands in Gomez-LopezHernandez syndrome. Arch Ophthalmol 2012;130:1496 –97. 10.1001/archophthalmol.2012.703 9. Man F, Wang Z, Wang J, et al. Unilateral vertical retraction syndrome with orbital band. J AAPOS 2009;13:419 –21. 10.1016/j.jaapos.2009.04.006 10. Eisler P. Die anatomie des menschlichen auges. In: Schieck F and Brückner A, eds. Kurzes Handbuch der Ophthalmologie, Bd. 1. Berlin: Springer-Verlag; 1930:1–96 11. Whitnall SE. Some abnormal muscles of the orbit. Anat Rec 1921;21:143–52 12. Sinclair NE, Roberts MA, Hourihan MD, et al. Radiologically manifested accessory extraocular muscles in thyroid eye disease. Ophthal Plast Reconstr Surg 2010;26:286–88. 10.1097/ IOP.0b013e3181ba56e0 13. Patel SH, Cunnane ME, Juliano AF, et al. Imaging appearance of the lateral rectus-superior rectus band in 100 consecutive patients without strabismus. AJNR Am J Neuroradiol 2014; 35:1830 –35. 10.3174/ajnr.A3943 14. Rutar T, Demer JL. “Heavy eye” syndrome in the absence of high myopia: A connective tissue degeneration in elderly strabismic patients. J AAPOS2009;13:36 – 44. 10.1016/j.jaapos. 2008.07.008 15. Dyce KM, Sack WO, Wensing CJC, eds. Textbook of Veterinary Anatomy. Philadelphia: Saunders; 1987:335–36, 342 16. Sevel D. The origins and insertions of the extraocular muscles: development, histologic features, and clinical significance. Trans Am Ophthalmol Soc 1986;84:488 –526 Neurographics 2017 March/April; 7(2):88 –91; www.neurographics.org 兩 91