Occult encephaloceles and temporal lobe epilepsy: developmental and acquired lesions in the middle fossa.

Three patients with medically refractory partial complex seizures were shown to have small and initially unsuspected encephaloceles of the middle fossa. All had bitemporal, independent, interictal epileptogenic abnormalities, and the side of origin of the seizures could not be determined by surface EEG alone. The encephaloceles were missed on the initial radiologic studies and were found retrospectively in two patients; the third was found at operation and was not demonstrable radiologically, even in retrospect. One was the sequel of remote mastoid surgery, another was neoplasm-related, and the third, developmental. In all, bony defects of the middle cranial fossa were associated with temporal lobe herniation. The patients were treated surgically and have had no further partial complex seizures since operation.