Hippocampal electrical stimulation in mesial temporal lobe epilepsy.
BACKGROUND
Adjustable, reversible therapies are needed for patients with pharmacoresistant epilepsy. Electrical stimulation of the hippocampus has been proposed as a possible treatment for mesial temporal lobe epilepsy (MTLE).


METHODS
Four patients with refractory MTLE whose risk to memory contraindicated temporal lobe resection underwent implantation of a chronic stimulating depth electrode along the axis of the left hippocampus. The authors used continuous, subthreshold electrical stimulation (90 microsec, 190 Hz) and a double blind, multiple cross-over, randomized controlled design, consisting of three treatment pairs, each containing two 1-month treatment periods. During each treatment pair the stimulator was randomly turned ON 1 month and OFF 1 month. Outcomes were assessed at monthly intervals in a double blind manner, using standardized instruments and accounting for a washout period. The authors compared outcomes between ON, OFF, and baseline periods.


RESULTS
Hippocampal stimulation produced a median reduction in seizures of 15%. All but one patient's seizures improved; however, the results did not reach significance. Effects seemed to carry over into the OFF period, and an implantation effect cannot be ruled out. The authors found no significant differences in other outcomes. There were no adverse effects. One patient has been treated for 4 years and continues to experience substantial long-term seizure improvement.


CONCLUSIONS
The authors demonstrate important beneficial trends, some long-term benefits, and absence of adverse effects of hippocampal electrical stimulation in mesial temporal lobe epilepsy. However, the effect sizes observed were smaller than those reported in non-randomized, unblinded studies.
Department of Clinical Neurological Sciences, University of Western Ontario, London Health Sciences Centre, London, Ontario, Canada.
J F
JF
Tellez-Zenteno
R S
RS
McLachlan
A
A
Parrent
C S
CS
Kubu
S
S
Wiebe
D000328:Adult; D038481:Anterior Temporal Lobectomy; D000927:Anticonvulsants / Q000627:therapeutic use; D003131:Combined Modality Therapy; D000075202:Contraindications; D018592:Cross-Over Studies; D046690:Deep Brain Stimulation; D004311:Double-Blind Method; D004833:Epilepsy, Temporal Lobe / Q000188:drug therapy / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D006624:Hippocampus / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D012647:Self-Assessment; D016896:Treatment Outcome
D000927:Anticonvulsants