[A case of arachnoid cyst associated with chronic subdural hematoma]

An 11-year-old boy was admitted to our clinic with complaint of headache. On admission he was in drowsy state and neurological examination revealed minimal motor weakness of the right hand. Plain skull roentgenogram demonstrated a thinning of the left temporal bone and elevation of the left sphenoidal wing. CT showed marked displacement of the midline structures from left to right. The left lateral ventricle was collapsed. A well circumscribed, homogenous, high density area was delineated in the left middle fossa. Contrast enhancement was negative. A-P view of left CAG showed a crescent shaped subdural avascular area in the parietal region. The anterior cerebral artery was roundly shifted from left to right. Chronic subdural hematoma due to bleeding of arachnoid cyst was most likely. Subdural collection was evacuated by trephination. The postoperative course was uneventful. Postoperative CT 3 week after operation delineated the arachnoid cyst more clearly as round low density area. Follow-up CT 6 months later showed the arachnoid cyst markedly reduced in size.