Memory fMRI lateralizes temporal lobe epilepsy.
BACKGROUND
The assessment of mesial temporal lobe (MTL) function is important for the diagnosis and treatment of temporal lobe epilepsy (TLE) and other brain diseases. Declarative memory depends on the integrity of the MTL region.


OBJECTIVE
To investigate hemispheric asymmetries of MTL activity in patients with symptomatic TLE.


METHODS
With use of blood oxygenation level-dependent fMRI, hemispheric asymmetries in MTL activation of 30 individual patients with refractory symptomatic TLE and 17 healthy control subjects were studied. Activation was induced by a task employing mental navigation and recall of landmarks based on the retrieval of individually familiar visuospatial knowledge.


RESULTS
The study demonstrated that the memory task used reliably activated MTL structures in individual control subjects and patients with refractory TLE including children, older subjects, and patients with low formal IQ. Interhemispheric differences in MTL activation lateralized the side of seizure onset in 90% of patients with symptomatic unilateral TLE. In contrast, healthy control subjects did not show a systematic asymmetry of MTL activation. Correlations between MTL activation and neuropsychological measures suggest that the fMRI-detectable MTL changes were specifically related to memory rather than to memory-independent visuospatial abilities.


CONCLUSIONS
fMRI of memory-induced MTL activation lateralizes the side of seizure onset in patients with refractory symptomatic TLE and may provide complementary information for presurgical evaluation.
Jokeit
H
H
Bethel Epilepsy Center, Mara Hospital, and Society for Epilepsy Research, Bielefeld, Germany.
Okujava
M
M
Woermann
F G
FG
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D013702:Temporal Lobe / Q000503:physiopathology; D014706:Verbal Learning / Q000502:physiology