[Interhemispheric arachnoid cyst; report of three cases].

Three operated cases of the interhemispheric arachnoid cyst were reported. Case 1: a 58-year-old female suffering from progressive right hemi-rigidity and gait disturbance for the past two years. Case 2: a 66-year-old female was admitted with chronic headache. MRI demonstrated a large interhemispheric cyst in these two patients. Case 3: a 6-month-old male had frequent episodes of tonic seizure. MRI demonstrated interhemispheric cyst and agenesis of the anterior part of corpus callosum. The resection of the cystic wall via the interhemispheric approach was performed for all cases. General convulsive seizure developed in the early stage following operation in case 1 and case 2, in spite of routine administration of prophylactic anticonvulsant. The seizures were well controlled thereafter. In all cases, the cyst disappeared on the follow up CT. Simple resection of cyst wall is effective in the surgical treatment of interhemispheric arachnoid cysts.