Correlations of interictal FDG-PET metabolism and ictal SPECT perfusion changes in human temporal lobe epilepsy with hippocampal sclerosis.
BACKGROUND
The pathophysiological role of the extensive interictal cerebral hypometabolism in complex partial seizures (CPS) in refractory mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) is poorly understood. Our aim was to study ictal-interictal SPECT perfusion versus interictal fluorodeoxyglucose (FDG)-PET metabolic patterns.


METHODS
Eleven adults with refractory unilateral mTLE-HS, who were rendered seizure free after epilepsy surgery, were included. All had an interictal FDG-PET and an interictal and ictal perfusion SPECT scan. FDG-PET data were reconstructed using an anatomy-based reconstruction algorithm, which corrected for partial volume effects, and analyzed semi-quantitatively after normalization to white matter activity. Using Statistical Parametric Mapping (SPM), we compared interictal metabolism of the patient group with a control group. We correlated metabolic with ictal perfusion changes in the patient group.


RESULTS
Global cerebral grey matter glucose metabolism in patients was decreased 10-25% compared with control subjects. Interictal PET hypometabolism and ictal SPECT hypoperfusion were maximal in the ipsilateral frontal lobe. Ictal frontal lobe hypoperfusion was associated with crossed cerebellar diaschisis. The ipsilateral temporal lobe showed maximal ictal hyperperfusion and interictal hypometabolism, which was relatively mild compared with the degree of hypometabolism affecting the frontal lobes.


CONCLUSIONS
Interictal hypometabolism in mTLE-HS was greatest in the ipsilateral frontal lobe and represented a seizure-related dynamic process in view of further ictal decreases. Crossed cerebellar diaschisis suggested that there is a strong ipsilateral frontal lobe inhibition during CPS. We speculate that surround inhibition in the frontal lobe is a dynamic defense mechanism against seizure propagation, and may be responsible for functional deficits observed in mTLE.
Nelissen
N
N
Department of Neurology, University Hospital Gasthuisberg, 49 Herestraat, 3000 Leuven, Belgium.
Van Paesschen
W
W
Baete
K
K
Van Laere
K
K
Palmini
A
A
Van Billoen
H
H
Dupont
P
P
D000328:Adult; D000465:Algorithms; D001786:Blood Glucose / Q000378:metabolism*; D002531:Cerebellum / Q000098:blood supply / Q000000981:diagnostic imaging; D002540:Cerebral Cortex / Q000098:blood supply / Q000000981:diagnostic imaging; D003545:Cysteine / Q000031:analogs & derivatives; D004292:Dominance, Cerebral / Q000502:physiology; D004569:Electroencephalography; D004734:Energy Metabolism / Q000502:physiology; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D019788:Fluorodeoxyglucose F18; D005625:Frontal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D049268:Positron-Emission Tomography; D012039:Regional Blood Flow / Q000502:physiology; D012598:Sclerosis; D013223:Statistics as Topic; D013702:Temporal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging*; D015899:Tomography, Emission-Computed, Single-Photon
D001786:Blood Glucose; D015609:Organotechnetium Compounds; D019788:Fluorodeoxyglucose F18; C059659:technetium Tc 99m bicisate; D003545:Cysteine