1. Orbital Bands/Accessory Extraocular Muscles
B Kightlinger1, E Saraf Lavi1, C Sidani1, A Sneider1
1University of Miami Miller School of Medicine, Miami, FL
We present 7 cases of orbital bands. All were believed to be unrelated to the patient's presenting symptoms. Reasons for initial imaging evaluation include Thyroid orbitopathy, trauma, sinusitis, papilledema, esotropia, and orbital neoplasm. Six of our cases involve bands that bridge the superior and inferior rectus muscles. One case revealed bilateral bands that extended from the inferior rectus muscles and attached to the temporal aspect of the globes. Five of the cases were found on MRI, two on CT. Bilateral bands were seen in 4 cases, unilateral in 3 cases.
Orbital bands on imaging are found to be isodense and isotense to normal EOM on CT and MRI respectively. They are often smaller in bulk than normal EOM. Orbital bands should not be confused with the normal lateral rectus-superior rectus band (LR-SR) or the lateral levator aponeurosis (LLA) connecting the levator muscle to the lacrimal gland. Degeneration of the LR-SR has been implicated with two forms of strabismus, heavy eye syndrome and sagging eye syndrome.
Purpose:
Orbital bands and accessory extraocular muscles (EOM) have rarely been described in the neuroradiology literature. We discuss the various forms of these anatomic variants, their imaging appearance, clinical significance, and imaging pitfalls.
Approach/Methods:
Seven patients with orbital bands/accessory EOM seen on MRI/CT orbits were retrospectively reviewed from 2011 to 2014 from a single institution
SR-LPS SR
BAND ON MR LR LR MR IR IR IR
BAND SR IR IR F
Table 1.
Case No.
Age (yrs)
Sex
Clinical Indication
Eye
Band Course
Modality 1 52 F
Thyroid Orbitopathy R
SR-IR CT 2 33 M
Trauma
B/L MR 3 22
Sinusitis 4 14
Papilledema 5 39
Esotropia 6 53 L 7 56
Orbital Neoplasm
IR-Globe ON
BAND
BAND
BAND
Figure 4. Coronal and axial T1W MR Orbits with
band connecting from the inferior rectus to the inferior globe.
(IR: Inferior Rectus; LR: Lateral Rectus; MR: Medial Rectus; SR-LPS: Superior Rectus-Levator Palpebrae Superioris) IR
Figure 2. Coronal and sagittal CT Orbits in a patient with thyroid orbitopathy unilateral right orbital band connecting superior and inferior recti. Note enlarged right medial rectus muscle.
(IR: Inferior Rectus; LR: Lateral Rectus; MR: Medial Rectus; ON: Optic Nerve; SR: Superior Rectus)
Summary/Conclusion:
Orbital bands or accessory EOM are a rarely reported entity where there exists an abnormal connection of tissue bridging EOM and/or the globes. While many patients with orbital bands have no visual symptoms, they have a higher prevalence in people suffering from strabismus among other conditions. Awareness of orbital bands by radiologists will improve their detection, guide surgeons in their anatomic approach, and ultimately improve patient outcomes. Knowledge of orbital bands will also help radiologists avoid the pitfall for describing a suspicious orbital mass with unnecessary work up for an unrelated symptom.
Findings/Discussion:
The normal human orbit contains six EOM, levator palpebral superioris muscle, and the orbicularis oculi muscle. Numerical aberrations of the EOM are rare with an estimated prevalence of 2%.
Three types of accessory EOM include: anomalous bands of muscle bridging two muscles; fibrous tissues adjacent to the muscles, which may attach to the globe; and muscles arising from the posterior orbit and inserting on the globe or EOM. Accessory EOM have rarely been reported in ophthalmologic literature but only one report has been found in radiology literature.
The clinical importance of orbital bands likely depends on the size and location. Often they are found incidentally in autopsy or for workup of non associated visual symptoms. However, there is an increased incidence of orbital bands in patients with restrictive strabismus, globe retraction, and eyelid retraction.
SR-LPS SO ON LR
LR-SR MR
LR-SR IR
SR-LPS
BAND SO ON MR
BAND
LR-SR MR
LR-SR
References:
1. Khitri MR, Demer JL. Magnetic Resonance Imaging of Tissues Compatible with Supernumerary Extraocular Muscles. Am J Ophthalmol 2010 Dec;150(6):925-31
2. Dobbs MD, Mawn LA, Donahue SP. Anomalous Extraocular Muscles with Strabismus. AJNR Am J Neuroradiol 2011 Oct;32(9):E167-8
3. 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 Sep;35(9):1830-5
4. Sinclair NE, Roberts MA, Hourihan MD, et al. Radiologically manifested accessory extraocular muscles in thyroid eye disease. Ophthal Plast Reconstr Surg 2010 Jul-Aug;26(4):286-8
5. von Ludinghausen M. Bilateral supernumerary rectus muscles of the orbit.
Clin Anat 1998;11:271–77 LR IR
Figure 1. Coronal and axial T1W MR Orbits with bilateral orbital bands connecting the superior and inferior recti.
(IR: Inferior Rectus; LR: Lateral Rectus; MR: Medial Rectus; ON: Optic Nerve; SO: Superior Oblique; SR-LPS: Superior Rectus-Levator Palpebrae Superioris)
Figure 3. Coronal T1W MR Orbits in a patient demonstrating the normal anatomical LR-SR band.
(IR: Inferior Rectus; LR: Lateral Rectus; MR: Medial Rectus; SO: Superior Oblique; SR-LPS: Superior Rectus-Levator Palpebrae Superioris; ON: Optic Nerve; LR-SR: Lateral Rectus-Superior Rectus Band)