Elsevier

Epilepsy Research

Volume 28, Issue 3, October 1997, Pages 233-243
Epilepsy Research

Thalamic glucose metabolism in temporal lobe epilepsy measured with 18F-FDG positron emission tomography (PET)

https://doi.org/10.1016/S0920-1211(97)00049-1Get rights and content

Abstract

Thalamic glucose metabolism has been studied in 24 patients suffering from temporal lobe epilepsy (TLE) using interictal 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). A total of 17 patients had a unilateral TL seizure onset, 11 of these patients had a mesial temporal lobe epilepsy syndrome (MTLE), with mesial gliosis and a mesial TL seizure origin. Three patients had a lateral TL seizure origin, and 3 patients had mesial TL tumors. Bilateral TLE was assumed in 7 patients. Only in the patient group with MTLE (n=11), the ipsilateral thalamic glucose uptake showed a statistically significant lower value when compared to the thalamus of the contralateral side (Wilcoxon paired sign test, P=0.012). There was a more pronounced hypometabolism in right TLE compared to left TLE. A `hypersynchronous seizure onset pattern' in ictal EEG was only seen in 6 (26%) patients (1 patient with bilateral, 5 with unilateral TLE). No correlation existed between the thalamic, temporal glucose metabolism and the `hypersynchronous seizure onset pattern'.

Introduction

The mesial temporal lobe (TL) structures, i.e. amygdala and the hippocampus play a major role in the initiation of seizures in TL epilepsy (TLE) [22]. These structures are functionally related to the anterior and dorsomedian thalamus by the Papez circuit (hippocampus→fornix→mamillary body→Vicq D'Azyr bundle→anterior thalamus→cingulate gyrus→hippocampus) and the Yakovlev circuit (amygdala→uncinate fascicle→orbitofrontal cortex→dorsomedian thalamus→amygdala). Moreover, the thalamus itself is involved in the regulation of cortical excitability 1, 2, 3, 5, 14, 15, 16, 20, 22, 29.

Recently, it has been claimed that the seizure onset in patients suffering from the syndrome of mesial TLE (MTLE) 6, 24may consist of an irregular, slow (2–3/s) sharp-slow wave activity as a relatively characteristic ictal onset pattern, the so-called `hypersynchronous pattern' 24, 26. This ictal onset pattern is associated with mesial temporal gliosis in patients with MTLE and resembles to a certain degree the classical 3/s spike-and-wave pattern seen in generalized absence epilepsy, where the thalamus plays a proven role in the initiation of this pattern [4]. 18F-fluordeoxyglucose positron emission tomography (18F-FDG-PET) studies in patients suffering from MTLE have shown hypometabolism of the affected TL 7, 8, 10, 11.

PET studies in patients with TLE investigating glucose utilization in the subcortical brain structures suggest a hypometabolism especially in the thalamus and caudate nucleus ipsilateral to the side of the epileptogenic focus 13, 21. The present study investigated the thalamic metabolism in patients suffering from TLE and examined whether a correlation existed between the degree of hypometabolism in MTLE patients seen either in the ipsilateral mesial TL or the ipsilateral thalamus, and the `hypersynchronous ictal onset pattern' as recorded by foremen ovale (FO) electrodes 25, 27.

Section snippets

Patients

Our study population consisted of 24 patients (12 males and 12 females, with a mean age of 27 years; min/max=14/52). Clinical and demographic data of the patients are listed in Table 1A. All patients were diagnosed as suffering from medically refractory TLE. As part of their presurgical evaluation, each patient underwent a thorough clinical examination as well as seizure monitoring using scalp and in most cases FO-electrodes [25], MRI and 18F-FDG-PET. Controls consisted of 13 healthy

Results

Regional CMRglu in μmol/100 ml/min of each patient for the ipsilateral and contralateral thalamus, temporal lobe, mesial temporal cortex, lateral temporal cortex, and temporal pole are listed in Table 1B. The means and standard deviations of the calculated glucose utilization in the thalamic and temporal cortex regions are listed in Table 2, Table 3, Table 4.

Discussion

Thalamic participation in terms of triggering and modification of cortical spike and wave discharges has been extensively studied both in animal models and human generalized 3/s spike wave absence epilepsy [4]. Our hypothesis, that those patients who show the so-called hypersynchronous ictal onset pattern in mesial TL would exhibit a more marked thalamic hypometabolism on the ipsilateral side was, however, not confirmed. Furthermore, we found in this study that the hypersynchronous seizure

Acknowledgements

This study was supported by the Swiss National Research Foundation, Grant No: 31-30079.90.

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