Memory lateralization in medial temporal lobe epilepsy assessed by functional MRI.
OBJECTIVE
To determine the utility of functional magnetic resonance imaging (fMRI) in preoperative lateralization of memory function in patients with medial temporal lobe epilepsy (MTLE).


METHODS
Nine patients with MTLE underwent standard preoperative assessment including video-EEG and intracarotid amytal testing (IAT). fMRI was performed while subjects encoded four types of stimuli (patterns, faces, scenes, and words). Activation maps were created for each subject representing areas more active for novel than for repeated stimuli. Regions of interest were drawn around the MTL in individual subjects, suprathreshold voxels were counted, and an asymmetry index was calculated.


RESULTS
In eight of nine subjects, lateralization of memory encoding by fMRI was concordant with that obtained from the IAT. Group-level analysis demonstrated greater activation in the MTL contralateral to the seizure focus such that in the left MTLE group, verbal encoding engaged the right MTL, whereas in the right MTLE group, nonverbal encoding engaged the left MTL.


CONCLUSIONS
fMRI is a valid tool for assessing of memory lateralization in patients with MTLE and may therefore allow noninvasive preoperative evaluation of memory lateralization. FMRI revealed that memory encoding may be reorganized to the contralateral MTL in patients with MTLE.
Golby
Alexandra J
AJ
Department of Radiology, Stanford University, Stanford, California, U.S.A. agolby@partners.org
Poldrack
Russell A
RA
Illes
Judy
J
Chen
David
D
Desmond
John E
JE
Gabrieli
John D E
JD
D000328:Adult; D000654:Amobarbital; D001519:Behavior; D002339:Carotid Arteries; D004292:Dominance, Cerebral; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D007269:Injections, Intra-Arterial; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory; D008875:Middle Aged
D000654:Amobarbital