Abstracts

Cerebral hemiatrophy with ipsilateral mesial temporal sclerosis (CHIMTS) poses a dilemma during evaluation for epilepsy surgery. It is unclear if seizures arise from the mesial temporal sclerosis (MTS) or elsewhere in the atrophic hemisphere. Whether epilepsy differs between subjects with CHIMTS and MTS alone (MTSA) is unknown. We compared features of epilepsy and surgical outcomes in subjects with CHIMTS and MTSA enrolled in the Multicenter Study of Epilepsy Surgery. CHIMTS and MTSA were diagnosed by cerebral MRI utilizing uniform protocol designed to detect epileptogenic lesions and MTS. MRI interpreted and coded by 2 blinded reviewers with good interobserver reliability. Both hippocampal atrophy and increased signal at high certainty required for diagnosis of MTS. Four controls with MTSA, enrolled following index case at same center, selected for each CHIMTS subject. Features of epilepsy and outcome following epilepsy surgery assessed prospectively using standardized questionnaires. 9/512 (1.8%) enrolled subjects had CHIMTS. 4/9 had minor focal neurological signs contralateral to CHIMTS; none had hemiparesis. Age at seizure onset, duration of epilepsy, occurrence of febrile seizures or status epilepticus did not differ between CHIMTS and MTSA. 8/9 CHIMTS and 8/36 MTSA had risk factors for epilepsy other than febrile seizures (p=.0002). Tonic-clonic seizures were more frequent in CHIMTS (p=.046), complex partial seizures were more frequent in MTSA (p=.008). Scalp video-EEG monitoring localized seizure onset in 5/9 CHIMTS and 21/36 MTSA. Intracranial recording was required in 1/9 CHIMTS and 6/36 MTSA. All CHIMTS subjects were offered surgery: 2 refused, 6 had anteromedial temporal lobectomy, 1 lateral temporal resection. 27/36 MTSA underwent surgery (anteromedial temporal lobectomy). 3/7, 3/7, and 4/6 CHIMTS and 22/26, 19/25, and 17/21 MTSA were free of seizures (other than auras) during postoperative year 1,2,and 3. Differences were statistically significant in postoperative year 1 only. Seizures appear to emerge from mesial temporal regions in CHIMTS. Seizure onset area can usually be determined with scalp video-EEG monitoring alone. Outcome following anteromedial temporal lobectomy differs from that seen in MTSA only during the first postoperative year. Clinically meaningful differences in later outcomes cannot be ruled out; studies with larger samples are indicated. (Supported by RO1 NS32375 (NIH-NINDS).)