Isolated fourth nerve palsy

Paul H Phillips MD (Dr. Phillips of the University of Arkansas Medical Center has no relevant financial relationships to disclose.)
Jonathan D Trobe MD, editor. (Dr. Trobe of the University of Michigan has no relevant financial relationships to disclose.)
Originally released January 12, 2000; last updated February 15, 2016; expires February 15, 2019

This article includes discussion of isolated fourth nerve palsy, superior oblique palsy, and trochlear nerve palsy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Isolated fourth nerve palsy is usually benign. The most common etiologies are congenital, traumatic, ischemic, and idiopathic causes. Extensive evaluations for isolated fourth nerve palsies are generally not indicated, but more intensive evaluation for underlying etiology may be necessary for nonisolated or bilateral fourth nerve palsies. Evaluation of ocular torsion enables differentiation of fourth nerve palsy from skew deviation and other causes of vertical diplopia. Spectacle prisms and strabismus surgery are effective treatments for most unresolved cases.

Key points

 

• Isolated fourth nerve palsy is usually benign and typically does not require an extensive evaluation.

 

• Nonisolated fourth nerve palsy should undergo imaging and evaluation directed to the topographically localizing symptoms and signs.

 

• The most common etiologies for a fourth nerve palsy are congenital, traumatic, ischemic, and idiopathic causes.

 

• Thyroid-related orbitopathy, skew deviation, and myasthenia gravis can mimic fourth nerve palsy.

 

• Spectacle prisms and strabismus surgery can be effective treatments for most unresolved cases.

Historical note and terminology

The terms “superior oblique paralysis,” “trochlear nerve palsy,” and “fourth nerve palsy” are essentially interchangeable for the purposes of this review.

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