Evaluation of ictal brain SPET using statistical parametric mapping in temporal lobe epilepsy

Abstract

An automated voxel-based analysis of brain images using statistical parametric mapping (SPM) is accepted as a standard approach in the analysis of activation studies in positron emission tomography and functional magnetic resonance imaging. This study aimed to investigate whether or not SPM would increase the diagnostic yield of ictal brain single-photon emission tomography (SPET) in temporal lobe epilepsy (TLE). Twenty-one patients (age 27.14 +/- 5.79 years) with temporal lobe epilepsy (right in 8, left in 13) who had a successful seizure outcome after surgery and nine normal subjects were included in the study. The data of ictal and interictal brain SPET of the patients and baseline SPET of the normal control group were analysed using SPM96 software. The t statistic SPM¿t¿ was transformed to SPM¿Z¿ with various thresholds of P<0.05, 0.005 and 0.001, and corrected extent threshold P value of 0.05. The SPM data were compared with the conventional ictal and interictal subtraction method. On group comparison, ictal SPET showed increased uptake within the epileptogenic mesial temporal lobe. On single case analysis, ictal SPET images correctly lateralized the epileptogenic temporal lobe in 18 cases, falsely lateralized it in one and failed to lateralize it in two as compared with the mean image of the normal group at a significance level of P<0.05. Comparing the individual ictal images with the corresponding interictal group, 15 patients were correctly lateralized, one was falsely lateralized and four were not lateralized. At significance levels of P<0.005 and P<0.001, correct lateralization of the epileptogenic temporal lobe was achieved in 15 and 13 patients, respectively, as compared with the normal group. On the other hand, when comparison was made with the corresponding interictal group, only 7 out of 21 patients were correctly lateralized at the threshold of P<0.005 and five at P<0.001. The result of the subtraction method was close to the single case analysis on SPM at P<0.05. However, at higher thresholds (P<0.005 and 0.001) the subtraction method was comparable to the SPM results only when individual ictal images were compared with the normal control group, and not when comparison was with the interictal group. It is concluded that SPM is an alternative diagnostic method for the localization or lateralization of the seizure focus in temporal lobe epilepsy and that interictal SPET could be omitted if a normal brain SPET database were to be established. The medical cost of seizure localization would thereby be reduced.

Statistical voxel-wise analysis of ictal SPECT reveals pattern of abnormal perfusion in patients with temporal lobe epilepsy

“…A previous study 6 o b s e rved parietal hyp e r p e rfusion in a few patients using SPM96 when comparing each individual ictal BSI with their interictal group. These authors believed that the findings of extra-temporal hyperperfusion at a lower threshold could be a false-positive result or a r a pid propagation of seizure discharge.…”

“…In addition to visual inspection, BSI is also suitable for statistical analysis. Statistical analysis of BSI has been used to analyze the regions of the brain that show diff e rences in perfusion in pathologies such as Alzheimer's disease 4 , systemic lupus erythematosus 5 and in the evaluation of epileptic foci in BSI [6][7][8] .…”

Clinical Value of the First Dedicated, Commercially Available Automatic Injector for Ictal Brain SPECT in Presurgical Evaluation of Pediatric Epilepsy: Comparison with Manual Injection

“…More recently, subtraction ictal SPECT techniques and statistical comparison with normal control SPECT databases have been validated by several studies, showing a rate of epileptogenic focus localization that was equivalent or superior to that seen in interictal-ictal side-by-side visual analysis (17)(18)(19)(20)(21).…”

Detection of Inter-hemispheric Asymmetries of Brain Perfusion in SPECT

“…These approaches aim at studying either inter-scan and intra-subject variability [12] or inter-scan and inter-subject variability [13], [14]. We believe that our approach studying intra-scan and intra-subject variability is different and complementary.…”