Brain areas involved in medial temporal lobe seizures: A principal component analysis of ictal SPECT data

Abstract

The study describes brain areas involved in medial temporal lobe (mTL) seizures of 12 patients. All patients showed so-called oro-alimentary behavior within the first 20 s of clinical seizure manifestation characteristic of mTL seizures. Single photon emission computed tomography (SPECT) images of regional cerebral blood flow (rCBF) were acquired from the patients in ictal and interictal phases and from normal volunteers. Image analysis employed categorical comparisons with statistical parametric mapping and principal component analysis (PCA) to assess functional connectivity. PCA supplemented the findings of the categorical analysis by decomposing the covariance matrix containing images of patients and healthy subjects into distinct component images of independent variance, including areas not identified by the categorical analysis. Two principal components (PCs) discriminated the subject groups: patients with right or left mTL seizures and normal volunteers, indicating distinct neuronal networks implicated by the seizure. Both PCs were correlated with seizure duration, one positively and the other negatively, confirming their physiological significance. The independence of the two PCs yielded a clear clustering of subject groups. The local pattern within the temporal lobe describes critical relay nodes which are the counterpart of oro-alimentary behavior: (1) right mesial temporal zone and ipsilateral anterior insula in right mTL seizures, and (2) temporal poles on both sides that are densely interconnected by the anterior commissure. Regions remote from the temporal lobe may be related to seizure propagation and include positively and negatively loaded areas. These patterns, the covarying areas of the temporal pole and occipito-basal visual association cortices, for example, are related to known anatomic paths.

Temporal lobe epilepsy: Differential pattern of damage in temporopolar cortex and white matter

“…Electrophysiological [Chabardes et al, 2005] and perfusion studies using single photon emission computed tomography [Weder et al, 2006] have demonstrated the early involvement of the temporal pole in the genesis of seizures. There have been also observations of MRI signal changes, most notably an increase in T2-weighted signal intensity in the WM of the anterior temporal lobe, which is sometimes associated with hypointense signal on T1-weighted images [Mitchell et al, 1999].…”

Localizing Seizure-Onset Zones in Presurgical Evaluation of Drug-Resistant Epilepsy by Electroencephalography/fMRI: Effectiveness of Alternative Thresholding Strategies

“…Clusters outside the mesiotemporal lobe (mean, 15) were mainly distributed among brain areas with known ictal functional connectivity to the mesiotemporal lobe in MTLE. 34,35 In patients 4 and 7, BOLD responses within the SOZ were negative. Negative BOLD signal correlates within the presumed SOZ have been reported in interictal as well as ictal EEG/fMRI recordings in approximately 30% of cases.…”

“…Three recordings localized the PA outside the SOZ within the cingulate gyrus and ipsilateral precentral gyrus, cortical areas embedded in a distant part of the MTLE network. 34,35,38 The cluster with the highest correlation may thus represent the effects of propagation. 36 Although the SOZ is usually considered to generate the most intensive increase in blood flow and consequently the most robust BOLD signal change, [39][40][41][42][43] the magnitude of the BOLD response in the hippocampal formation is smaller than that in neocortical areas.…”

Realistic Simulated MRI and SPECT Databases

“…Functional variability may be characterized by exploring the structure of covarying areas among functional data issued from homogeneous populations. Principal component analysis [7,8] and correspondence analysis [9] have proved their ability to characterize normal perfusion and ictal perfusion in patients with MTLE.…”