Original articleMagnetic Resonance Imaging of Tissues Compatible with Supernumerary Extraocular Muscles
Section snippets
Methods
Between December 1, 1996, and December 31, 2009, a total of 118 orthotropic volunteers and 453 strabismic patients underwent high-resolution orbital imaging under a prospective protocol designed to optimize image resolution using the best available methods at the time. We selected for detailed analysis those cases with evidence of anomalous EOMs. Written informed consent was obtained prospectively according to a protocol approved by the Institutional Review Board of the University of
Results
From December 1996 through December 2009, a total of 118 normal subjects without strabismus and 453 strabismic subjects underwent high-resolution orbital MRI. Twelve of these subjects were identified who had a band consistent with 1 or more supernumerary EOMs. Bands had intensities equivalent to that of typical EOMs. Eleven of these subjects had underlying strabismus, giving a prevalence of supernumerary EOM bands in strabismic subjects of 2.4% and in normal subjects of 0.8%, a difference that
Discussion
We believe the present report to be the largest case series of supernumerary human EOMs, which in this series have been identified on high-resolution MRI as having signal characteristics matching those of known EOMs. These supernumerary muscular bands occurred in numerous variations, most commonly as connections between 2 EOMs or between an EOM and the globe. The prevalence of these anomalous EOM bands is higher in the strabismic (2.4%) than the nonstrabismic (0.8%) population, but nonetheless
Monica R. Khitri, MD, has recently completed her residency in ophthalmology at the Jules Stein Eye Institute, University of California Los Angeles. She is starting her fellowship in pediatric ophthalmology and strabismus at Children's Hospital of Philadelphia.
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Monica R. Khitri, MD, has recently completed her residency in ophthalmology at the Jules Stein Eye Institute, University of California Los Angeles. She is starting her fellowship in pediatric ophthalmology and strabismus at Children's Hospital of Philadelphia.
Joseph L. Demer, MD, PhD, is Chief of Comprehensive Ophthalmology and Professor of Neurology at the University of California Los Angeles. He holds the Leonard Apt Professorship, Directs the Ocular Motility Clinical Laboratory, and chairs the EyeSTAR Training Program.
With a PhD in Biomedical Engineering, Dr. Demer has worked for more than 30 years on neural and mechanical factors regulating ocular motility, particularly MRI of the functional anatomy of extraocular muscles and orbital connective tissues.