Enlarging Temporal Arachnoid Cyst Extending Inside the Sphenoid Sinus.

BACKGROUND: Cerebral arachnoid cysts that eroded the skull base and extended into the paranasal sinus are very rare with only a few cases reported.

CASE DESCRIPTION: A 71-year-old woman with history of headache for 4 years was evaluated because of an enlarging right temporal cystic lesion with evidence of resorption of the greater wing of the sphenoid bone and a fluid-filled sphenoid sinus. For 3 years, the cerebral cyst remained stable and minimally symptomatic. On her last magnetic resonance imaging, the cyst enlarged and perilesional edema was identified. The patient was treated with an open intracranial approach to explore the cyst. An arachnoid cyst was found which extended into the sphenoid sinus through a defect in the temporal fossa floor. The skull base defect was repaired using a muscle plug and fibrin sealant to obliterate the dural and bony defect. The arachnoid cyst was fenestrated to the basal cisterns.

CONCLUSIONS: Cerebral arachnoid cysts extending into the paranasal sinuses are very rare presenting mostly with rhinorrhea and nasal symptoms. Patients with neurologic symptoms may need intracranial surgery to fenestrate the cyst. Obliteration of the fistula into the paranasal sinus is essential to prevent further complications.