[A case of symptomatic arachnoid cyst, that had been growing for 14 years, at the posterior part of the left temporal lobe].

The authors report a 54-year-old woman with headache in whom a cyst was detected at the posterior part of the left temporal lobe following a traffic accident in 1993. Symptoms had recently worsened and computed tomography demonstrated an enlarged cyst in 2007. Thereafter, the patient underwent cyst fenestration. Intraoperative findings showed multilocular cysts with calcification. Symptoms improved immediately. Histological findings showed that the cyst was composed of collagenous membrane and a monolayer of cells compatible with arachnoid cyst. These findings also showed calcification and we considered that growth of the arachnoid cyst had been induced by trauma. We expected an arachnoid cyst with a single cavity, but this lesion was multilocular. Retrospectively, cine magnetic resonance image (MRI) seemed to show multilocular cysts. Cine MRI might be an effective tool to determine whether a cyst is multilocular.