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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
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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
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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.
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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
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