Abstract
Background:Arachnoid cysts are congenital lesions that contain fluid identical to cerebrospinal fluid (CSF). They usually do not communicate with CSF spaces. The vast majority of arachnoid cysts are congenital asymptomatic lesions that are discovered incidentally. Those lesions that do become symptomatic typically present in childhood with signs and symptoms of intracranial hypertension, seizures, and focal neurologic deficits specific to cyst location.Case Description: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.
Highlights
Arachnoid cysts are well-described congenital fluid-filled structures lined with meningothelial cells first reported in the 16th century by Dutch Anatomist Pieter Paux and first described by Bright in 1831.[6]. These cysts generally do not communicate with cerebrospinal fluid (CSF) spaces and contain fluid that is identical to CSF
Hustler et al presented a similar case in a 16-month-old boy who presented initially with right-sided mydriasis and subsequently developed a progressive oculomotor palsy over the ensuing 14 months
Figure 6: 3‐month postoperative Magnetic resonance imaging (MRI) demonstrating resolution of T2 FLAIR signal abnormality consistent with complete surgical resection of the right parasellar arachnoid cyst as a consequence of trauma, infection, or hemorrhage; the pathologic components of these cysts are distinctly different from true congenital arachnoid cysts
Summary
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
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