American Journal of Ophthalmology
Volume 150, Issue 6 , Pages 925-931.e2, December 2010

Magnetic Resonance Imaging of Tissues Compatible with Supernumerary Extraocular Muscles

  • Monica R. Khitri

      Affiliations

    • Jules Stein Eye Institute and Department of Ophthalmology, University of California, Los Angeles, Los Angeles, California
    • ,
  • Joseph L. Demer

      Affiliations

    • Jules Stein Eye Institute and Department of Ophthalmology, University of California, Los Angeles, Los Angeles, California
    • Department of Neurology, University of California, Los Angeles, Los Angeles, California
    • Neuroscience Interdepartmental Program, University of California, Los Angeles, Los Angeles, California
    • Bioengineering Interdepartmental Program, University of California, Los Angeles, Los Angeles, California
    • Corresponding Author InformationInquiries to Joseph L. Demer, Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, 100 Stein Plaza, Los Angles, CA 90095-7002

Accepted 12 June 2010. published online 31 August 2010.

Purpose

To determine by magnetic resonance imaging (MRI) the prevalence and anatomy of anomalous extraocular muscle (EOM) bands.

Design

Prospective, observational case series.

Methods

High-resolution, multipositional, surface coil orbital MRI was performed using T1 or T2 fast spin echo weighting with target fixation control under a prospective protocol in normal adult subjects and a diverse group of strabismic patients between 1996 and 2009. Images demonstrating anomalous EOM bands were analyzed digitally to evaluate their sizes and paths, correlating findings with complete ophthalmic and motility examinations.

Results

Among 118 orthotropic and 453 strabismic subjects, 1 (0.8%) orthotropic and 11 (2.4%) strabismic subjects exhibited unilateral or bilateral orbital bands having MRI signal characteristics identical to EOM. Most bands occurred without other EOM dysplasia and coursed in the retrobulbar space between rectus EOMs such as the medial rectus to lateral rectus, from superior to inferior rectus, or from 1 EOM to the globe. In 2 cases, horizontal bands from the medial rectus to lateral rectus muscles immediately posterior to the globe apparently limited supraduction by collision with the optic nerve. All bands were too deep to be approached via conventional strabismus surgical approaches.

Conclusions

Approximately 2% of humans exhibit on MRI deep orbital bands consistent with supernumerary EOMs. Although band anatomy is nonoculorotary, some bands may cause restrictive strabismus.

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PII: S0002-9394(10)00431-9

doi:10.1016/j.ajo.2010.06.007

American Journal of Ophthalmology
Volume 150, Issue 6 , Pages 925-931.e2, December 2010

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