Insular cortex involvement in mesiotemporal lobe epilepsy: A positron emission tomography study

Abstract

Somesthetic and emotional symptoms that are common in patients with mesial temporal lobe epilepsy are usually related to hippocampo-amygdalar complex involvement. Recent stereo-electroencephalographic studies have shown a relationship between such symptoms and epileptic insular discharges. To further investigate this problem, we carried out a positron emission tomography study using fluorodeoxyglucose (18F-FDG) and flumazenil (11C-FMZ) in mesial temporal lobe epilepsy patients. The aim of our study was to assess the existence of a cortical insular involvement in order to examine its clinical correlates and the relationship between the postoperative outcome and the insular involvement. Fluorodeoxyglucose and flumazenil-positron emission tomography studies were carried out in 18 patients with mesial temporal lobe epilepsy patients. A statistical parametric mapping (SPM96) was performed to analyze the data in comparison to 18 healthy volunteers. For each set of fluorodeoxyglucose and flumazenil images a group and an individual analysis were performed. In addition, a region of interest analysis was performed to validate the results. Focusing on the metabolic abnormalities, we also investigated the role of insular cortex in the symptoms experienced by the patients and the prognostic value of insular metabolic abnormalities. Highly significant hypometabolism and BZR binding decreases were detected in the insular cortex. Results were similar using the region of interest approach. Insular involvement (mainly ipsilateral to the seizure focus) was present in 60% of the patients. Emotional symptoms correlated with hypometabolism in the anterior part of the ipsilateral insular cortex, whereas somesthetic symptoms correlated with hypometabolism in the posterior part. No relationship between postoperative outcome and ipsilateral insular hypometabolism was found. Unilateral mesial temporal lobe epilepsy is associated with insular hypometabolism and benzodiazepine receptor loss. Our results also suggest that the anterior part of the insular cortex is involved in the emotional symptoms and the posterior insular cortex is involved in the somesthetic symptoms. Hypometabolism located in the insula did not influence postoperative outcome after anterior lobectomy.

Ictal bradycardia in a young child with focal cortical dysplasia in the right insular cortex

“…Of interest, the concomitant activation of the insular cortex was described in 60% of patients with mesiotemporal epilepsy in a recent PET study. 13 Phenytoin, which was part of our patient's antiepileptic medication, is known to have antiarrhythmic effects, but no significant bradycardia has been reported in long-term ECG monitoring studies of patients presenting with phenytoin overdose.…”

18FDG‐PET in different subtypes of temporal lobe epilepsy: SEEG validation and predictive value

“…Interictal metabolic changes have been further correlated in other studies with ictal electroclinical patterns, 12 initial ictal discharge frequency, 13 and ictal brain SPECT perfusion. 11 In particular, comparisons of patients with and without ictal symptoms showed relationships between dystonic posturing and interictal hypometabolism of putaminal and extratemporal cortical areas; 25 between emotional/somesthetic symptoms and respectively anterior/ posterior insular hypometabolism; 26 between d ej a-vu and parahippocampal hypometabolism; 19 and between hyperkinetic behaviors and subcortical hypometabolism. 27 This study is the first to use a whole-brain voxel-based analysis to determine metabolic involvement in subgroups of TLE patients defined by SEEG recordings.…”

Epileptiform synchronization in the rat insular and perirhinal cortices in vitro

“…Other studies have corroborated these results. One group reported involvement of the IG in 60% of TLE seizures using positron emission tomography (PET; Bouilleret et aL, 2002), while assorted case studies of patients with insular lobe seizures report similar visceral and somatosensory sensations during ictal discharges (Rossetti et aL, 2005;Ryvlin, 2006). Such findings have prompted the proposai for an alternative epileptic syndrome designation, "Temporal Plus Epilepsy" (TPE).…”