Middle cranial fossa arachnoid cyst developing in infancy. Case report.

The pathophysiology of primary arachnoid cysts of the middle cranial fossa is still unclear, and no widely accepted therapeutic criteria for this condition have been established. The authors present the case of a 7-year-old boy with this cyst accompanied by temporal lobe hypoplasia. On the basis of computerized tomography taken on the 2nd day after birth and magnetic resonance imaging upon admission, the arachnoid cyst in this case was attributed to brain hypoplasia secondary to abnormal arachnoid development and was confirmed to have developed primarily during infancy. Experience with this case yielded new findings useful in clarifying the pathophysiology of this condition and establishing therapeutic criteria for such a case.