Hypometabolism and Interictal Spikes during Positron Emission Tomography Scanning in Temporal Lobe Epilepsy

Abstract

To study the influence of interictal spikes on ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET), EEG monitoring was performed during PET scanning in 21 patients with temporal lobe epilepsy. Asymmetry indices were calculated in the polar, mesial, anterior-lateral, mid-lateral and posterior-lateral temporal region of interests of FDG-PET (PET-AI). 70.7% of spikes were recorded with their maximum at the anterior temporal region (F₇, F₈, FT₉, FT₁₀), 29.3% at mid-temporal (T₇, T₈), and none at posterior temporal region (P₇, P₈). Regardless of the side of epileptic focus, right-left difference of the total spikes had a significant negative correlation with right/left PET-AIs of the anterior-lateral temporal region (Spearman’s ρ = –0.565, p = 0.009), polar (ρ = –0.500, p = 0.021) and whole temporal region (ρ = –0.480, p = 0.028). FDG-PET hypometabolism may reflect not only a permanent functional deficit but also a transient regional cerebral dysfunction related to the occurrence of interictal spikes.

Quantitative Analysis of Simultaneous EEG Features during PET Studies for Childhood Partial Epilepsy

“…In this study, areas of increase in the frequency of interictal spikes were well correlated with hypometabolism on PET, when compared to those of lower frequency. That is, 70.7% of all spikes in the anterior temporal area matched PET findings in temporal lobe epilepsy 14,15. Previously, PET localization using α-[ 11 C]-Methyl-L-tryptophan was proven with interictal spike frequency in tuberous sclerosis 15.…”

“…In the present study, we became concerned with whether the localized epileptogenic area represented by interictal spikes and focal polymorphic slow waves was a seizure focus or not. However, previous reports have indicated that the location of the epileptogenic area in EEG closely matched the foci of hypometabolism on PET, and the area of ictal onset and propagation in surgical cases showed slight hypometabolism in PET/MRI coregistration 12,14,16,18,19…”

Subdural electrodes

“…Morphological methods can point to an area that may need to be removed but can't, so far, tell us how much tissue around that area to remove, tell us in which abnormality seizures originate when there is more than one abnormality, or tell us what morphologically normal tissue might also need to be removed. Positron emission tomographic (PET) scans can show areas of abnormal, or at least unusual, metabolic activity but doesn t necessarily tell us which part of that unusual activity arises from where the seizures actually start(Hong et al, 2002). Techniques based on blood flow such as functional magnetic resonance imaging (fMRI) can suggest areas of greater cortical activity, if only by inference, but the time frame of fMRI acquisition is in seconds, and we know that seizure activity can spread widely within seconds.…”

Application of MicroPET in Basic Epilepsy Research

“…FDG-PET has been successfully used to identify the brain regions responsible for seizure generation. FDG-PET imaging is also frequently utilized in the presurgical evaluation of TLE patients with unremarkable MRI scans to identify the epileptogenic zone, which can provide useful data towards a decision to carry out an invasive intracranial EEG recording [5,6].…”