A rare case of a parasellar arachnoid
cyst presenting with oculomotor
palsy is presented. The patient is a 45-year-old male who presented with acute onset
diplopia and frontal
headache. Neurologic examination revealed right ptosis, pupillary dilation, and opthalmoparesis consistent with an oculomotor
palsy. Computed tomography (CT) scan and lumbar puncture failed to reveal evidence of a
subarachnoid hemorrhage. Magnetic resonance imaging (MRI) of the brain demonstrated a 1 cm right parasellar nonenhancing mass that was hyperintense on T2 flair and with a fluid-fluid level concerning for a thrombosed posterior communicating artery (PCommA)
aneurysm. There was an additional finding of a left occipital pole intraparenchymal
hemorrhage in the setting of multiple hereditary cavernomas. Formal cerebral angiography revealed normal intracranial and extracranial vasculature. The patient was taken to the operating room for a right frontotemporal
craniotomy, which revealed compression of the right oculomotor nerve by an arachnoid
cyst. The
cyst was fenestrated and resected with
decompression of the oculomotor nerve. Postoperatively, the
third nerve palsy had completely resolved.
CONCLUSIONS: The above case demonstrates that
arachnoid cysts should be considered in the differential for patients presenting with nonpupil sparing
third nerve palsy and require timely surgical intervention. As is the case for an expanding PCommA
aneurysm, prompt
decompression results in the best chance for recovery of oculomotor nerve function.