Original article
High-Resolution Magnetic Resonance Imaging of the Extraocular Muscles and Nerves Demonstrates Various Etiologies of Third Nerve Palsy

https://doi.org/10.1016/j.ajo.2006.10.035Get rights and content

Purpose

The etiology of third nerve palsy is usually diagnosed by history, motility examination, and presence of lid and pupil involvement, as well as cranial and vascular imaging. We used high-resolution magnetic resonance imaging (hrMRI) of the oculomotor nerve and affected extraocular muscles (EOMs) to investigate oculomotor palsy.

Design

Prospective, noncomparative, observational case series in an academic referral setting.

Methods

Twelve patients with nonaneurysmal oculomotor palsy of 0.75 to 252 months’ duration were studied. In the orbit and along the intracranial oculomotor nerve, hrMRI at 1- to 2-mm thickness was performed. Coronal plane images of each orbit were obtained in multiple, controlled gaze positions. Structural abnormalities of the oculomotor nerve and associated changes in EOM volume and contractility were evaluated.

Results

Cases were categorized as tumor related, congenital, diabetic, traumatic, and idiopathic according to clinical characteristics and hrMRI findings. Reduction of volume and contractility of affected EOMs were noted in six patients; however, there was no marked EOMs atrophy in two cases of diabetic oculomotor palsy, and there were four cases of aberrant regeneration. hrMRI demonstrated the oculomotor nerve at the midbrain and at EOMs in all cases, and in two cases with previous normal neuroimaging elsewhere that demonstrated contrast-enhancing tumors on the oculomotor nerve. One patient with apparently unilateral congenital inferior division oculomotor palsy had no detectable ipsilateral and a hypoplastic contralateral oculomotor nerve exiting the midbrain.

Conclusions

hrMRI provides valuable information in patients with oculomotor palsy, such as structural abnormalities of the orbit and oculomotor nerve, and atrophy and diminished contractility of innervated EOMs. This information could be helpful in diagnosis and management of oculomotor palsy.

Section snippets

Patients and methods

Twelve consecutive patients with oculomotor palsy were identified from an ongoing prospective hrMRI study of strabismus conducted at the Jules Stein Eye Institute, a referral facility at the University of California, Los Angeles, from 1993 to 2004. No patient had intracranial aneurysm. All participants in this study provided written informed consent according to a protocol conforming to the Declaration of Helsinki, and the study was approved by our institutional review board.

Complete

Results

Characteristics of the 12 patients with oculomotor palsy are summarized in the Table and include data for seven men and five women with a mean ± SD average age of 37.3 ± 23.5 years (range, six to 82 years). Duration of oculomotor palsy ranged from 0.75 to 252 months before enrollment onto the study. These 12 patients included two cases attributable to tumors, one congenital,11 two diabetic, and three traumatic. In four cases, we could find no definite cause after complete evaluation, and thus

Discussion

Multiple structural causes of oculomotor palsy can be demonstrated by hrMRI. We used hrMRI to evaluate 12 patients with oculomotor palsy; we often found unsuspected causes. Multipositional hrMRI of EOMs in these patients further demonstrated various degrees of EOM atrophy and decreased contractility that could be important in surgical planning.

Two cases of presumed neuroma-related oculomotor palsy had previous neuroimaging that was reported to be normal. However, hrMRI demonstrated

Hui-Chuan Kau, MD, MS, is the head Chief of Ophthalmology at Taoyuan Veterans Hospital, and an Instructor in Ophthalmology at National Yang-Ming University, and Taipei Veterans General Hospital in Taiwan. Dr Kau received medical training at National Yang-Ming University, Ophthalmology residency at Taipei Veterans General Hospital, and fellowship in Pediatric Ophthalmology at the Jules Stein Eye Institute, University of California, Los Angeles. Dr Kau conducts clinical research on strabismus,

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    Hui-Chuan Kau, MD, MS, is the head Chief of Ophthalmology at Taoyuan Veterans Hospital, and an Instructor in Ophthalmology at National Yang-Ming University, and Taipei Veterans General Hospital in Taiwan. Dr Kau received medical training at National Yang-Ming University, Ophthalmology residency at Taipei Veterans General Hospital, and fellowship in Pediatric Ophthalmology at the Jules Stein Eye Institute, University of California, Los Angeles. Dr Kau conducts clinical research on strabismus, and laboratory research on oxidative stress in ocular diseases.

    Joseph L. Demer, MD, PhD, is Leonard Apt Professor Professor and Chief of Comprehensive Ophthalmology, and Professor of Neurology, David Geffen School of Medicine at UCLA. He directs the Ocular Motility Clinical Laboratory and the EyeSTAR Program. In 2003, Dr Demer received the Friedenwald Award from ARVO, and a Recognition Award from the Alcon Research Institute in 2004 for his work on the extraocular muscles and orbital connective tissues. Dr Demer chairs the ARVO Awards Committee.

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