Duane Retraction Syndrome 1

Duane retraction syndrome is a clinically and genetically heterogeneous condition with a highly variable phenotype.  Most cases occur sporadically but others are familial and about 30% of affected individuals have other congenital anomalies.  It is also seen as part of other syndromes such as Goldenhar (164210), and Wildervanck (314600).  In the absence of other anomalies, it is called isolated Duane syndrome.  In addition, three types with autosomal dominant inheritance have been defined.  The clinical features are highly variable making distinction difficult.  Intrafamilial variation may be less than interfamilial differences.  Patients with type 1 discussed here are more likely to have esotropia with a head turn to the involved side in unilateral cases whereas those with type 2 are considered more likely to have an exotropia with a head turn toward the uninvolved side. 

This is a congenital and non-progressive strabismus syndrome.  Sporadic cases are mostly unilateral while familial ones are more likely to be bilateral.  The essential features are globe retraction upon adduction with narrowing of the lid fissure, and some limitation of abduction. Vertical deviation during adduction is sometimes seen.  Frank strabismus in primary position is evident in as many as 76% of individuals and a compensatory head turn is often adopted but amblyopia still occurs in at least 10% of individuals.  Females are affected more frequently than males.

At one point the syndrome was considered to be a myopathic disorder based on histologic changes in the lateral rectus but current thought based on MRI and neurohistologic studies favors a neuropathic etiology.  The abducens motor neurons and the sixth nerve may be absent or dysplastic.  Branches of the third nerve may also co-innervate the lateral and medial rectus muscles.  EMG studies have documented simultaneous activation of the two muscles which likely accounts for at least some of the globe retraction.  However, hypoplastic muscles, including the superior oblique, superior rectus, and levator, have also been visualized on MRI.