Delayed recurrent arachnoid cyst of the occipital convexity in an elderly woman.

A 62-year-old woman presented with a symptomatic arachnoid cyst of the right occipital convexity manifesting as visual disturbances and headache. She underwent craniotomy with membranectomy and fenestration to the subarachnoid space. Postoperatively, her complaints disappeared and brain magnetic resonance (MR) imaging showed cyst shrinkage. During the first 1 year after surgery, she made a good recovery without clinical symptoms or cyst enlargement. However, she complained of visual disturbances after 6 years. Brain MR imaging revealed cyst enlargement and Goldmann perimetry detected left lower quadrantanopia. The diagnosis was recurrent arachnoid cyst. A second surgical procedure was performed including membranectomy for histological examination of the cyst membrane, and an Ommaya reservoir was inserted into the cyst cavity to prevent further cyst enlargement. The histological findings were compatible with arachnoid cyst, similar to the results seen at the first surgery. She was discharged 3 weeks after the second operation with no complications, and follow up continues as an outpatient. Patients with symptomatic arachnoid cysts typically have good progress after surgery, but the present case shows that follow up should continue for at least 6 years after surgery, even if cyst volume reduction was initially favorable.