Oculomotor-abducens synkinesis

Oculomotor-abducens synkinesis (OCABSN) is an autosomal recessive disorder characterized by a specific anomaly of extraocular muscle movements involving the oculomotor nerve (cranial nerve III) and the abducens nerve (cranial nerve VI). The superior branch of CN3 innervates the levator palpebrae superioris muscle, which raises the eyelid, and CN6 innervates the lateral rectus muscle, which controls lateral eye movement. Affected individuals show ptosis as well as elevation of the eyelid on ipsilateral abduction. The features indicate abnormal innervation of these muscles and suggest synkinesis of the oculomotor and abducens nerves. The disorder can be classified as a congenital cranial dysinnervation disorder (CCDD), and also shows features of congenital fibrosis of the extraocular muscles (CFEOM; see 135700) (summary by Khan et al., 2004 and Whitman et al., 2019). See also oculomotor-levator synkinesis (OCLEVS; 151610), a similar disorder. [from OMIM]