Oculomotor-levator synkinesis (OCLEVS) is characterized by abnormal eyelid elevation or retraction during ipsilateral adduction. The disorder most likely results from aberrant innervation of extraocular muscles by the oculomotor nerve (cranial nerve III). Normally, the levator muscle is served by the superior branch of CN3 and the medial rectus muscle is served by the inferior branch of CN3. The clinical features suggest synkinesis between the medial rectus and levator muscle branches. 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 Pang et al., 1986 and Khan et al., 2004) See also oculomotor-abducens synkinesis (OCABSN; 619215), caused by mutation in the ACKR3 gene (610376) on chromosome 2q37.