Asymptomatic massive subdural hematoma in a patient with bitemporal agenesis and bilateral temporal arachnoid cysts.

The case of a 38-year-old man with a history of chronic migraine is reported. Despite a 3 week history of changes in his migraine pattern, a normal neurologic examination led to conservative treatment. He later presented with worsening headaches and imbalance; tendon reflexes were increased on the right side, and brain computed tomography and magnetic resonance imaging revealed a massive subacute subdural hematoma over the left hemisphere, developing on the grounds of bilateral temporal agenesis. The presence of bilateral temporal arachnoid cysts along with bitemporal agenesis altered clinical findings, causing only mild symptoms where an otherwise acute and devastating neurologic deterioration would be expected.