Cavernous malformation of the oculomotor nerve mimicking a partially thrombosed posterior communicating artery aneurysm: report of two cases.

BACKGROUND AND IMPORTANCE: Cavernous malformations of the cranial nerves are exceedingly rare. The classic radiographic appearance of cavernous malformations may not be obvious when located in a cranial nerve. CLINICAL
PRESENTATION: We present 2 cases of acute oculomotor paresis caused by cavernous malformations of the oculomotor nerve that were mistaken for a thrombosed posterior communicating artery aneurysm on magnetic resonance imaging, magnetic resonance angiography, and digital subtraction angiography. Both patients underwent a craniotomy with exploration of the lesion. Both cavernous malformations were completely resected while the integrity of the third cranial nerve was maintained. One patient experienced complete resolution of the oculomotor palsy.
CONCLUSION: Although rare, cavernous malformations should be included in the differential diagnosis of a partially thrombosed posterior communicating artery aneurysm. Exploration and complete lesional resection are possible with improvement of the cranial nerve function.