Duane Syndrome: Board Essentials
Master Duane syndrome for NBEO and OKAP: types, globe retraction, key differentials and surgical indications.
The most accepted pathophysiologic mechanism in Duane retraction syndrome is:
Duane Syndrome in 30 Seconds
Duane syndrome is a congenital cranial dysinnervation disorder that causes horizontal duction deficits with globe retraction on adduction. For NBEO and OKAP, recognize the retraction sign, classify the pattern of horizontal motility limitation and distinguish it from a sixth nerve palsy.
The Underlying Mechanism
Congenital absence or hypoplasia of the abducens (sixth nerve) nucleus leaves the lateral rectus without normal innervation. The lateral rectus receives aberrant innervation from the inferior division of the oculomotor (third) nerve, causing paradoxical co-contraction of the medial and lateral rectus during adduction. This pulls the globe posteriorly and narrows the palpebral fissure.
The Three Types
- Type 1: Abduction is limited more than adduction. This is the most common type and often produces esotropia in primary gaze.
- Type 2: Adduction is limited more than abduction. It often presents with exotropia in primary gaze.
- Type 3: Both abduction and adduction are limited. Primary-position alignment may be esotropic or exotropic.
4 Facts Exams Always Ask
- Globe retraction with palpebral fissure narrowing on adduction is the pathognomonic sign.
- Type 1 is the most common form of Duane syndrome.
- Disease is usually unilateral, favors the left eye and occurs more often in girls.
- Upshoot or downshoot can occur on adduction. Observation is appropriate for patients with good primary-position alignment, minimal abnormal head posture and no significant functional symptoms. Consider surgery for significant primary-position deviation, marked head posture or severe retraction.
The Classic Trap
Do not call type 1 Duane syndrome an acquired sixth nerve palsy solely because abduction is limited. Both can produce esotropia with abduction deficit. Duane syndrome shows globe retraction, palpebral fissure narrowing and sometimes vertical overshoots on adduction. A sixth nerve palsy lacks these retraction findings and often has a larger esotropic angle. Unlike a restrictive process, Duane syndrome typically shows little or no limitation of passive globe rotation, so forced ductions are generally normal unless secondary contracture develops.
Clinical Pearl
The narrowed palpebral fissure on adduction represents induced pseudoptosis from globe retraction rather than true eyelid ptosis. Watching the globe during versions is often more informative than assessing ductions alone, since globe retraction identifies congenital cranial dysinnervation rather than an isolated extraocular muscle palsy. Patients frequently adopt a compensatory face turn to maintain binocular single vision. Surgery improves primary-position alignment, abnormal head posture and severe globe retraction, but it does not restore normal ocular motility, because the underlying problem is congenital misinnervation.
Checkpoint 1
Which finding is most typical of Duane retraction syndrome type I?
Checkpoint 2
Which subtype of Duane retraction syndrome is characterized by limited abduction AND limited adduction?
A 7-year-old girl has longstanding left esotropia and a mild left face turn. Left abduction is markedly limited. Her parents report the eye has looked this way since infancy. You are deciding between Duane syndrome type 1 and an acquired sixth nerve palsy.
Which finding helps differentiate Duane syndrome type I from an acquired sixth nerve palsy in a young child with an abduction deficit?
Sources & Reviewer Info
Diagram created with AI image generation, clinically reviewed for accuracy.
References
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 6: Pediatric Ophthalmology and Strabismus.
- American Association for Pediatric Ophthalmology and Strabismus. "Duane Syndrome."
- American Academy of Ophthalmology EyeWiki. "Duane Retraction Syndrome."
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