Quantitative multi-compartmental SPECT image analysis for lateralization of temporal lobe epilepsy

Abstract

This study assesses the utility of compartmental analysis of SPECT data in lateralizing ictal onset in cases of a putative mesial temporal lobe epilepsy (mTLE). An institutional archival review provided 46 patients (18M, 28F) operated for a putative mTLE who achieved an Engel class Ia postoperative outcome. This established the standard to assure a true ictal origin. Ictal and interictal SPECT images were separately coregistered to T1-weighted (T1W) magnetic resonance (MR) image using a rigid transformation and the intensities matched with an l1 norm minimization technique. The T1W MR image was segmented into separate structures using an atlas-based automatic segmentation technique with the hippocampi manually segmented to improve accuracy. Mean ictal-interictal intensity difference values were calculated for select subcortical structures and the accuracy of lateralization evaluated using a linear classifier. Hippocampal SPECT analysis yielded the highest lateralization accuracy (91%) followed by the amygdala (87%), putamen (67%) and thalamus (61%). Comparative FLAIR and volumetric analyses yielded 89% and 78% accuracies, respectively. A multi-modality analysis did not generate a higher accuracy (89%). A quantitative anatomically compartmented approach to SPECT analysis yields a particularly high lateralization accuracy in the case of mTLE comparable to that of quantitative FLAIR MR imaging. Hippocampal segmentation in this regard correlates well with ictal origin and shows good reliability in the preoperative analysis.

Lateralization of temporal lobe epilepsy by multimodal multinomial hippocampal response-driven models

“…Hippocampal fluid-attenuated inversion recovery (FLAIR) MRI lateralization accuracy when using both mean signal intensity and standard deviation has been shown to be 75% when control cases were used to establish a boundary domain within which study cases were deemed inconclusive [4]. Using a similar approach with subtraction SPECT coregistered to MRI, a lateralization accuracy of 89% was achieved for patients attaining a seizure-free outcome [5]. Interestingly, no significant correlation arose between hippocampal FLAIR MRI and SPECT suggesting that the two modalities bore complementary information.…”

“…The four hippocampal imaging attributes used for this study were volume [4], mean and standard deviation of FLAIR intensity [4], and mean of normalized ictal–interictal SPECT intensity (the difference between ictal and interictal intensities normalized to the whole brain interictal mean value) [5]. …”

“…Automated and manual hippocampal segmentation approaches for volume assessment have yielded 74% and 78% lateralization accuracy [2, 3] whereas, fluid-attenuated inversion recovery (FLAIR) MRI signal analysis yielded a 98% accuracy in a single study [4]. Compartmentalized hippocampal SPECT analysis correctly lateralized mTLE in 91% of cases [5]. …”

Lateralization of temporal lobe epilepsy by imaging-based response-driven multinomial multivariate models

“…Four hippocampal imaging attributes including volumetrics [2], mean and standard deviation of FLAIR intensity [2], and mean of normalized ictal–interictal SPECT intensity (the difference between ictal and interictal intensities normalized to the whole brain interictal mean value [3]) were extracted. They were then incorporated into the development of four univariate (Models 1 to 4), and three multivariate (Model 5 to Model 7) response models for lateralization of epileptogenicity.…”

Time-Shift Homotopic Connectivity in Mesial Temporal Lobe Epilepsy

“…14,26 Imaging studies have demonstrated structural 27,28 and functional abnormalities in these regions. [29][30][31][32][33] Thus, we considered that reduced homotopic connectivity might result from nodal impairments of these regions in mTLE. Moreover, studies have proposed a variety of propagation patterns of epileptic activity from the originating focus to the contralateral side; the limbic structures and basal ganglia are the important nodes within the propagation pathway.…”