BACKGROUNDResearches in ocular electromyography (EMG) and Magnetic resonance imaging (MRI) of patients with Duane retraction syndrome (DRS) suggest that there may be additional abnormalities such as paradoxical innervation between horizontal rectus muscles and vertical rectus muscles, hypoplasia of vertical rectus muscle and that oblique muscles may also contribute to the heterogeneity of the clinical manifestation of DRS. This paper reports the results of superior rectus recession for vertical deviation and A pattern in DRS Type III and discusses the pathogenesis of the disease.

METHODSSuperior and lateral rectus recession were performed in 5 cases of Huber type III DRS to treat vertical deviation and A pattern strabismus. Before operation, MRI of the brain, brainstem, cavernous sinus, and orbits were performed.

RESULTSAll subjects had unilateral limitation of both abduction and adduction, with palpebral fissure narrowing and globe retraction in adduction. Three cases had A pattern of strabismus, three cases had hypertropia. The abducens nerves (CN6) were either absent or hypoplasitic in the brainstem in all patients. Two eyes had larger oculomotor foramen. Two eyes had hypoplasia of the superior rectus and the inferior rectus. There was presumably a branch of the third cranial nerve (CN3) innervating the lateral rectus (LR) in one eye. While in another eye, two branches of CN3 sent into medial rectus were revealed. After surgery, vertical deviation in the primary position was reduced in all patients and A pattern was eliminated in 3 patients. One patient developed 10Δ consecutive esotropia postoperatively.

CONCLUSIONThe results suggest that structural abnormalities of vertical muscle and abnormal orbital innervation may be related to vertical deviation and the presence of A pattern in DRS type III. Recession of the superior rectus muscle seems to be a safe and effective treatment for vertical deviation and A pattern strabismus in DRS Type III.