Nonaneurysmal cranial nerve compression as cause of neuropathic strabismus: evidence from high-resolution magnetic resonance imaging

Am J Ophthalmol. 2011 Dec;152(6):1067-1073.e2. doi: 10.1016/j.ajo.2011.05.031. Epub 2011 Sep 8.

Abstract

Purpose: To seek evidence of neurovascular compression of motor cranial nerves (CNs) in otherwise idiopathic neuropathic strabismus using high-resolution magnetic resonance imaging (MRI).

Design: Prospective, observational case series.

Methods: High-resolution, surface coil orbital MRI was performed in 10 strabismic patients with idiopathic oculomotor (CN III) or abducens (CN VI) palsy. Relationships between CNs and intracranial arteries were demonstrated by 0.8-mm thick, 162-μm resolution, heavily T2-weighted MRI in fast imaging using steady-state acquisition sequences. Images were analyzed digitally to evaluate cross-sectional areas of extraocular muscles.

Results: In one patient with CN III palsy, an ectatic posterior communicating artery markedly flattened and thinned the ipsilateral subarachnoid CN III. Cross-sections of the affected medial, superior, and inferior rectus muscles 10 mm posterior to the globe-optic nerve junction were 17.2 ± 2.5 mm(2), 15.5 ± 1.3 mm(2), and 9.9 ± 0.8 mm(2), significantly smaller than the values of 23.6 ± 1.9 mm(2), 30.4 ± 4.1 mm(2), and 28.8 ± 4.6 mm(2), respectively, of the unaffected side (P < .001). In 2 patients with otherwise unexplained CN VI palsy, ectatic basilar arteries contacted CN VI. Mean cross-sections of affected lateral rectus muscles were 24.0 ± 2.3 mm(2) and 29.8 ± 3.1 mm(2), significantly smaller than the values of 33.5 ± 4.1 mm(2) and 36.9 ± 1.6 mm(2), respectively, in unaffected contralateral eyes (P < .05).

Conclusions: Nonaneurysmal motor CN compression should be considered as a cause of CN III and CN VI paresis with neurogenic muscle atrophy when MRI demonstrates vascular distortion of the involved CN. Demonstration of a benign vascular cause can terminate continuing diagnostic investigations and can expedite rational management of the strabismus.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Abducens Nerve Diseases / diagnosis
  • Abducens Nerve Diseases / etiology*
  • Adolescent
  • Adult
  • Cerebral Arterial Diseases / complications*
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Intracranial Aneurysm / pathology
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Nerve Compression Syndromes / complications*
  • Oculomotor Muscles / pathology
  • Oculomotor Nerve Diseases / diagnosis
  • Oculomotor Nerve Diseases / etiology*
  • Prospective Studies
  • Strabismus / etiology*
  • Subarachnoid Space
  • Young Adult