Topography of interictal glucose hypometabolism in unilateral mesiotemporal epilepsy

Abstract

We mapped the regional cerebral glucose metabolism (rCMRGlu) in 20 patients suffering from medically refractory focal epilepsy of either left or right mesiotemporal origin (mTLE) during resting wakefulness. After temporal lobectomy, histology demonstrated hippocampal sclerosis in 18 patients. Pixel-by-pixel comparisons with healthy control subjects showed significant (p < 0.001) depressions of the mean rCMRGlu ipsilateral to the epileptic focus in the mesiotemporal region, including the hippocampus and the parahippocampal gyrus and middle temporal gyrus. Additional remote rCMRGlu depressions occurred bilaterally in the fronto-orbital cortex and ipsilaterally in the posterior insula and the thalamus. Patients with left-sided mTLE had additional rCMRGlu depressions in the left inferior frontal gyrus (Broca's region) and superior temporal gyrus at the parietotemporal junction, whereas corresponding rCMRGlu depressions were not present in patients with right mTLE. Neuropsychological testing showed impaired verbal fluency, verbal intelligence, and verbal memory in the left mTLE patients. Correlations of the specific mean rCMRGlu depressions and the neuropsychological deficits suggest that impaired language functions in patients with left mTLE could result from functional changes beyond the temporal lobe.

Metabolism is Normal in Astrocytes in Chronically Epileptic Rats: A 13C NMR Study of Neuronal—Glial Interactions in a Model of Temporal Lobe Epilepsy

“…However, this was only statistically significant for unlabeled glucose, not for [1-13 C]glucose, likely because the percentage of enrichment in glucose was only 18%, thus the differences might have been too small to be detectable. This decreased consumption is in agreement with animal and human data showing interictal hypometabolism within the hippocampus, which could extend to extratemporal cortical and subcortical regions (Arnold et al, 1996;Dube et al, 2001;Vielhaber et al, 2003b;Chassoux et al, 2004). Moreover, in these areas neuronal loss does not necessarily correlate with interictal hypometabolism (Ryvlin et al, 1991;O'Brien et al, 1997;Foldvary et al, 1999;Dube et al, 2001).…”

“…These lesions can also be found in extrahippocampal structures, such as in the parahippocampal cortices, amygdala, and thalamus (Cendes et al, 1993;Arnold et al, 1996;Chassoux et al, 2004).…”

Gender‐specific Differences of Hypometabolism in mTLE: Implication for Cognitive Impairments

“…Spatially standardized and metabolically normalized rCMRGlu images (reference: mean global metabolism of the control group) were used in comparisons within and between control and patient groups. Comparisons were performed by using t-maps calculated according to a random-effects model on a pixel-by-pixel basis, as previously described (6). The t-maps thresholded at p < 0.01 were analyzed for clusters of ≥12 pixels, which partially corrected for spatial correlation and multiple comparisons (6,13).…”

“…FDG-PET has been used for lateralization of the seizure-onset zone, especially in those cases in which surface EEG and magnetic resonance imaging (MRI) provided discordant findings. However, FDG-PET revealed not only hypometabolism in the epileptogenic zone in mTLE, but also extratemporal metabolic disturbances (6)(7)(8).…”

“…These areas are supposed to be affected secondarily by ongoing subclinical seizure activity, inhibition, and deafferentation rather than by morphologic tissue damage (8,9). The degree of hypometabolism in these regions was shown to correlate well with neuropsychological impairments such as verbal memory function or cognitive abilities (6,7).…”