High-Resolution Magnetic Resonance Imaging Demonstrates Abnormalities of Motor Nerves and Extraocular Muscles in Patients With Neuropathic Strabismus

doi:10.1016/j.jaapos.2005.12.006

Journal of American Association for Pediatric Ophthalmology and Strabismus

Volume 10, Issue 2, April 2006, Pages 135-142

Presented at the AAPOS Meeting Orlando Florida March, 2005.

https://doi.org/10.1016/j.jaapos.2005.12.006 Get rights and content

Introduction: Although the ocular motility examination has been used traditionally in the diagnosis of strabismus that is a result of cranial nerve (CN) abnormalities, magnetic resonance imaging (MRI) now permits the direct imaging of lesions in CN palsies. Methods: Prospectively, nerves to extraocular muscles (EOMs) were imaged with T1 weighting in orbits of 83 orthotropic volunteers and 96 strabismic patients in quasicoronal planes using surface coils. Intraorbital resolution was 234–312 microns within 1.5- to 2.0-mm thick planes. CNs were imaged at the brainstem using head coils and T2 weighting, yielding 195 micron resolution in planes 1.0-mm thick in 6 normal volunteers and 22 patients who had oculomotor (CN3), trochlear (CN4), or abducens (CN6) palsies and Duane syndrome. Results: Oculomotor (CN3) and abducens (CN6) but not trochlear (CN4) nerves were demonstrable in the orbit and skull base in all normal subjects. Patients with congenital CN3 palsies had hypoplastic CN3s both in orbit and skull base, with hypoplasia of involved EOMs. Patients with chronic CN6 and CN4 palsies exhibited atrophy of involved EOMs. Patients with Duane syndrome exhibited absence or hypoplasia of CN6 in both orbit and brainstem regions, often with mild hypoplasia and apparent misdirection of CN3 to the lateral rectus muscle. Unlike CN6 palsy, patients with Duane syndrome exhibited no EOM hypoplasia. Patients with congenital fibrosis exhibited severe hypoplasia of CN3, moderate hypoplasia of CN6, and EOM hypoplasia, particularly severe for the superior rectus and levator muscles. Conclusion: High-resolution MRI can directly demonstrate pathology of CN3 and CN6 and affected EOM atrophy in strabismus caused by CN palsies. Direct imaging of CNs and EOMs by MRI is feasible and useful in differential diagnosis of complex strabismus.

Section snippets

Subjects and methods

In a prospective study of imaging ongoing since 1990, a total of 83 orthotropic volunteers and 96 patients with strabismus presumed on clinical grounds to be caused by cranial neuropathy underwent high-resolution orbital MRI under a prospective protocol. Orthotropic volunteers were recruited by advertising; the patients were recruited from referral strabismus practices and a collaborative study of EOM dysinnervation disorders. In all subjects, written informed consent was obtained prospectively

Extraocular Muscle Imaging

The stereotypic locations and sizes of normal EOMs have been reported using this technique.1, 4, 5, 6, 7, 8, 9, 10, 11, 12 All findings were consistent with previous reports.

Imaging of Intraorbital Motor Nerves

It was possible to examine, in the deep orbit, the motor nerves to the EOMs in image planes of 1.5- to 2-mm thickness and field of view 6 to 8 cm. In normal subjects, all of the motor nerves to the EOMs could be visualized in some cases (Fig. 1). Motor nerves to the medial rectus (MR), inferior rectus (IR), inferior oblique

Discussion

Orbital imaging, particularly using MRI, has broadened understanding of the anatomy and physiology of the EOMs and their associated connective tissues.5, 17 In living humans, it is now possible to image at near microscopic resolution the physiologic changes associated with conjugate eye movements, vergence, and accommodation.⁶ It has been possible for some years to use clinically available equipment to image the size, contractility, and position of each EOM.

The current study was a directed,

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: Supported by grants from the National Eye Institute: EY08313, EY13583, and EY00331. Also supported by an unrestricted grant from Research to Prevent Blindness. Joseph L. Demer is the Leonard Apt Professor of Ophthalmology.

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Major articleHigh-Resolution Magnetic Resonance Imaging Demonstrates Abnormalities of Motor Nerves and Extraocular Muscles in Patients With Neuropathic Strabismus

Section snippets

Subjects and methods

Extraocular Muscle Imaging

Imaging of Intraorbital Motor Nerves

Discussion

Am J Ophthalmol

Ophthalmology

Am J Ophthalmol

A 12 year, prospective study of extraocular muscle imaging in complex strabismus

J AAPOS

MR imaging of cranial nerve lesions using six different high-resolution T1 and T2(*)-weighted 3D and 2D sequences

Acta Radiol

Orbital imaging in strabismus surgery

Three-dimensional location of human rectus pulleys by path inflections in secondary gaze positions

Invest Ophthalmol Vis Sci

Anatomy of strabismus

Major article
High-Resolution Magnetic Resonance Imaging Demonstrates Abnormalities of Motor Nerves and Extraocular Muscles in Patients With Neuropathic Strabismus