title: Postnatal development and enlargement of primary middle cranial fossa arachnoid cyst recognized on repeat CT scans.
abstract: The etiology and mechanism of expansion of primary intracranial arachnoid cysts have been much debated. A rare case of an 8-month-old boy is reported, in which postnatal development and enlargement of a middle cranial fossa arachnoid cyst was detected on follow-up CT scans. Based on intraoperative and histological findings, the cyst was found to be intra-arachnoid. The wall was excised completely, and the lobe adjacent to the cyst appeared normal apart from signs of atrophy. Histological study of the excised cyst revealed a common arachnoid membrane with neither ependymal nor inflammatory cells; the cyst fluid was similar to CSF. The etiology of the lesion remains unclear, but it was considered that the expansion of the cyst might have occurred through a ball-valve mechanism of the membrane in communication with the general subarachnoid space.
mesh_terms: D001099:Arachnoid; D002493:Central Nervous System Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D002533:Cerebral Angiography; D003399:Craniotomy; D003560:Cysts / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D006801:Humans; D007223:Infant; D008297:Male; D014057:Tomography, X-Ray Computed