Probable Ciliary Nerve Within Capsule of an Orbital Cavernous Venous Malformation.

Removal of an orbital cavernous venous malformation in a 39-year-old white female resulted in a significant intraoperative sectoral mydriasis. White fascicles were recorded as running into the mass at surgery, and one of these was confirmed histologically to be peripheral nerve within the capsule of a markedly fibrous orbital cavernous venous malformation. Most efferent pupillary anomalies after orbital surgery are probably due to ischemic or tractional neuropraxia, but the resected nerve raises the possibility of unplanned excision of a few fascicles of the postganglionic (parasympathetic) short ciliary nerves.