[A case of symptomatic arachnoid cyst of the occipital convexity in an adult].

Symptomatic arachnoid cyst in an adult patient is rare. We present a case of a 51-year-old female with an arachnoid cyst of the right occipital convexity who developed homonymous hemianopsia. She had complained of numbness in the limbs at the age of 47 and based on MRI was diagnosed with a cystic space-occupying lesion in the right occipital convexity. After being under observation for four and a half years, she complained of headache and visual disturbance, at which time we diagnosed growth of the cyst. On ophthalmologic examination, homonymous hemianopsia was demonstrated. She underwent membranectomy, which resulted in the disappearance of visual disturbance. This case is comparatively rare among previously reported cases of symptomatic arachnoid cyst with regard to both location and symptom. Membranectomy is one of effective methods for treating symptomatic arachnoid cyst in the occipital convexity.