Abstracts

RATIONALE: Most studies of surgical treatment of epilepsy have not analyzed outcomes as a function of resection side, though a few have reported overall similar sucess for left and right temporal resections. This study compares seizure free rates for resections in the language dominant and nondominant sides in the subgroup of patients with pathologically verified mesial temporal sclerosis.
METHODS: All epilepsy surgery patients with pathologically verified hippocampal sclerosis from 1991 to 1999 with minimum followup of one year were included (N= 116). Patients were classed as dominant resections (DOM, N = 46), nondominant resections (NDOM, N = 59), or mixed or unclear language dominance OTH, N = 11). Outcome was based on the last year (Seizure free except for auras (SF, N = 76), improved ([gt]75% seizure reduction, IM, N = 29) or not seizure free (NSF, N = 11).
RESULTS: The DOM group had significantly (p [lt] 0.05) better outcome (SF 78%, IM 17%, NSF 4%; NDOM, SF 56%, IM 31%, NSF 14%; OTH, SF 64%, IM 27%, NSF 9%). Followup time (DOM 2.9 y, NDOM 2.8 y, OTH 3.0 y), age of seizure onset (DOM 9.7 y, NDOM 9.4 y, OTH 6.3 y) and age at surgery (DOM 31.2 y, NDOM 31.7 y, OTH 30.0 y) did not differ. Gender, history of febrile seizures or status epilepticus, family history of seizures, and psychiatric history were also similar. Significant etiological factors such as trauma with intracranial injury, CNS infection, shunt, or AVM were more common in the NDOM group (DOM 20%, NDOM 36%, OTH 27%). WAIS full scale IQ scores were not different (DOM 86.0, NDOM 87., OTH 79.9). Scalp EEG showed similar portions with interictal spikes strictly on the side ipsilateral to resection (DOM 61% ipsilateral, 39% bilateral; NDOM 56%, ipsilateral, 44% bilateral; OTH 82% ipsilateral, 18% bilateral). MRI sometimes showed more extensive abnormalities in the NDOM group, including bilateral hippocampal atrophy (DOM 4.4%, NDOM 6.8%, OTH 9.1%), additional ipsilateral neocortical changes (DOM 8.7%, NDOM 15%, OTH 27%), or bilateral neocortical changes (DOM 0%, NDOM 3.4%, OTH 0%). Mean hippocampal resection was larger in the NDOM group (DOM 27.8 mm, NDOM 30.6 mm, OTH 28.7).
CONCLUSIONS: Superior seizure free rates for lobectomy for mesial temporal sclerosis in the dominant hemisphere is a new and unexpected finding. There are no obvious demographic differences in the groups, but nondominant resection patients were more likely to have specific etiological factors, or neuroimaging evidence of abnormalities beyond the resected hippocampus. Outcomes are needed from other centers to determine whether this difference is due to referral or selection bias.