Duane's retraction syndrome Type I (most common type) results from which developmental anomaly?

• A Fibrosis of the lateral rectus muscle due to ischemia
• B Absence of the trochlear nucleus with anomalous superior oblique innervation
• C Absence of the abducens nucleus with aberrant innervation of the lateral rectus by the oculomotor nerve ✓
• D Maldevelopment of the superior orbital fissure causing mechanical restriction

Explanation

Duane's retraction syndrome Type I results from aplasia or hypoplasia of the abducens nucleus and nerve, with consequent aberrant innervation of the lateral rectus by a branch of the oculomotor nerve (CN III). When the patient attempts adduction, the oculomotor nerve branch co-innervates both the medial and lateral recti, causing simultaneous contraction — producing globe retraction and narrowing of the palpebral fissure. Abduction is limited because there is no true abducens input to the lateral rectus. It is more common in the left eye and in females.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.