What is Duane Syndrome?
Duane syndrome is a congenital cranial dysinnervation disorder characterized by limited horizontal eye movement (typically restricted abduction), globe retraction with eyelid fissure narrowing on attempted adduction, and often abnormal vertical eye movements (up- or downshoots) due to co-contraction of the lateral and medial rectus muscles. 1, 2
Pathophysiology
The fundamental defect involves dysinnervation of the lateral rectus muscle due to aplasia or hypoplasia of the abducens nucleus, with secondary aberrant innervation of the lateral rectus by branches from the medial rectus subnucleus of the oculomotor nerve 2. This misdirection of axons destined for the medial rectus creates the characteristic paradoxical innervation pattern 3.
Clinical Presentation
Key Diagnostic Features
- Horizontal duction deficits: Most commonly limited abduction (outward movement) of the affected eye 2
- Globe retraction: The eye pulls back into the orbit during attempted adduction (inward movement) 1, 4
- Palpebral fissure narrowing: The eyelid opening becomes smaller when the eye attempts to look inward 4, 2
- Abnormal vertical movements: Up- or downshoots may occur during horizontal eye movements 1, 2
Epidemiology and Laterality
- Usually unilateral presentation 2
- Female preponderance 2
- Most cases are sporadic, though up to 10% are familial with autosomal dominant inheritance 3
Clinical Classification
Three types of Duane syndrome are recognized based on the pattern of horizontal eye movement limitation 3:
- Type 1 (most common): Limited abduction with relatively preserved adduction
- Type 2: Limited adduction with relatively preserved abduction
- Type 3: Limited both abduction and adduction
The esotropic form (inward deviation) is most common 1.
Distinguishing Duane Syndrome from Other Strabismus
When evaluating esotropia, full abduction on monocular duction testing distinguishes infantile or accommodative esotropia from paretic or restrictive esotropia, or esotropic Duane syndrome 5. Duane syndrome is listed among conditions associated with exotropia, alongside congenital fibrosis syndrome, craniofacial abnormalities, and ocular myasthenia gravis 5.
Associated Abnormalities
Duane syndrome may occur as an isolated finding or with systemic manifestations 3:
- Ocular abnormalities in the affected or fellow eye 4
- Dysmorphic features in certain autosomal dominant syndromes 3
- Rare associations include crocodile tear syndrome, preauricular tags, and Hirschsprung disease 4
- Chromosomal loci at 4q, 8q, and 22q have been suggested 3
Management Principles
Indications for Intervention
Surgery aims to improve binocular alignment in primary gaze, reduce abnormal head turn, minimize globe retraction, and eliminate up- or downshoots 1, 2. There is no perfect cure for Duane syndrome, and treatment must be individualized based on severity of clinical findings 6.
Surgical Approaches
- For esotropia or exotropia in primary gaze: Differential recessions of the lateral and medial rectus muscles 2
- For globe retraction and shoots: Y-split or periosteal fixation of the lateral rectus muscle depending on severity 2
- Transposition procedures: May involve full or partial vertical rectus transposition, rectus muscle union, or single vertical rectus transposition (superior or inferior) 1
- Augmentation techniques: Posterior fixation sutures, resection of transposed muscles, and/or simultaneous weakening of the ipsilateral medial rectus may enhance effectiveness 1