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  • Updated 11.16.2021
  • Released 01.12.2000
  • Expires For CME 11.16.2024

Isolated fourth nerve palsy

Introduction

Overview

Isolated fourth nerve palsy is a typically benign condition that causes vertical or oblique binocular diplopia. The most frequent etiologies for isolated fourth nerve palsy are decompensation of a congenital weakness, head or surgical trauma, extra-axial nerve ischemia, nerve inflammation, and local compression by tumor. Thyroid-related orbitopathy, skew deviation, myasthenia gravis, and sagging eye syndrome may mimic fourth nerve palsy. Spectacle prisms and strabismus surgery can be effective treatments for cases that do not resolve spontaneously.

Key points

• Isolated fourth nerve palsy is usually benign and typically does not require an extensive evaluation.
• Isolated fourth nerve palsy causes ipsilateral hypertropia in primary gaze that increases on contralateral gaze and ipsilateral head tilt.

• Non-isolated fourth nerve palsy should undergo neuroimaging and evaluation directed to the topographically localizing symptoms and signs.

• The most important etiologies for a fourth nerve palsy are decompensation of a congenital weakness, head or surgical trauma, extra-axial nerve ischemia, nerve inflammation, and local compression by tumor.

• Thyroid-related orbitopathy, skew deviation, myasthenia gravis, and sagging eye syndrome 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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