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. 2023 Mar;8(1):183-192.
doi: 10.1002/epi4.12694. Epub 2023 Jan 30.

The diagnostic value of ictal SPECT-A retrospective, semiquantitative monocenter study

Freya Schulte  1 , Felix Bitzer  1 , Florian Christoph Gärtner  2 , Tobias Bauer  1 , Randi von Wrede  1 , Tobias Baumgartner  1 , Attila Rácz  1 , Valeri Borger  3 , Tim von Oertzen  4 , Hartmut Vatter  3 , Markus Essler  2 , Rainer Surges  1 , Theodor Rüber  1
Affiliations

The diagnostic value of ictal SPECT-A retrospective, semiquantitative monocenter study

Freya Schulte et al. Epilepsia Open. 2023 Mar.

Abstract

Objective: Ictal single photon emission computed tomography (SPECT) can be used as an advanced diagnostic modality to detect the seizure onset zone in the presurgical evaluation of people with epilepsy. In addition to visual assessment (VSA) of ictal and interictal SPECT images, postprocessing methods such as ictal-interictal SPECT analysis using SPM (ISAS) can visualize regional ictal blood flow differences. We aimed to evaluate and differentiate the diagnostic value of VSA and ISAS in the Bonn cohort.

Methods: We included 161 people with epilepsy who underwent presurgical evaluation at the University Hospital Bonn between 2008 and 2020 and received ictal and interictal SPECT and ISAS. We retrospectively assigned SPECT findings to one of five categories according to their degree of concordance with the clinical focus hypothesis.

Results: Seizure onset zones could be identified more likely on a sublobar concordance level by ISAS than by VSA (31% vs. 19% of cases; OR = 1.88; 95% Cl [1.04, 3.42]; P = 0.03). Both VSA and ISAS more often localized a temporal seizure onset zone than an extratemporal one. Neither VSA nor ISAS findings were predicted by the latency between seizure onset and tracer injection (P = 0.75). In people who underwent successful epilepsy surgery, VSA and ISAS indicated the correct resection site in 54% of individuals, while MRI and EEG showed the correct resection localization in 96% and 33% of individuals, respectively. It was more likely to become seizure-free after epilepsy surgery if ISAS or VSA had been successful. There was no MR-negative case with successful surgery, indicating that ictal SPECT is more useful for confirmation than for localization.

Significance: The results of the most extensive clinical study of ictal SPECT to date allow an assessment of the diagnostic value of this elaborate examination and emphasize the importance of postprocessing routines.

Keywords: epilepsy; neuroimaging; perfusion; presurgical evaluation; seizure onset zone.

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Conflict of interest statement

FS, FB, FCG, and TBauer have no conflict of interest to disclose. RvW has received travel support, fees as speaker or for serving on the advisory board from Angelini, Apocare, Arvelle, Cerbomed, Desitin, Eisai, GW pharmaceuticals‐JAZZ pharma and UCB Pharma. These activities were not related to the content of this manuscript. TBaumgartner and AR have no conflict of interest to disclose. VB has received fees for serving as clinical consultant from Brainlab AG. These activities were not related to the content of this manuscript. TvO and HV have no conflict of interest to disclose. RS has received fees as speaker or for serving on the advisory board from Angelini, Arvelle, Bial, Desitin, Eisai, Janssen‐Cilag GmbH, LivaNova, Novartis, Precisis GmbH, UCB Pharma, UnEEG and Zogenix. These activities were not related to the content of this manuscript. TR declares that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest. The results were presented in a poster at the DGFE 2022 in Leipzig and at the OHBM 2022 in Glasgow.

Figures

FIGURE 1
FIGURE 1
Schematic of image acquisition (A), visual SPECT assessment (B) and Ictal‐Interictal SPECT Analysis by SPM (C).
FIGURE 2
FIGURE 2
Classification of intermodal coherence between visual SPECT assessment (VSA)/ictal‐interictal SPECT Analyses by SPM (ISAS) and the clinical focus hypothesis in alphabetical order and with decreasing accuracy of the findings.
FIGURE 3
FIGURE 3
Comparisons of evaluations of ictal SPECT and of different subgroups. (A) Degree of intermodal coherence in the full cohort. The bracket marks category A (sublobar level) of the VSA and ISAS cohorts tested against categories B, C, D, E (P = 0.03). (B) Degree of intermodal coherence in the temporal and frontal cohort. (C) Degree of intermodal coherence of all people with and without MRI abnormalities (MR‐positive vs. MR‐negative). (D) Degree of intermodal coherence in individuals who did and who did not become seizure‐free after surgery. The x‐axis determines the classification of intermodal coherence. The y‐axis shows the percentage of individuals within the respective concordance categories (P < 0.05 = *).
FIGURE 4
FIGURE 4
Venn diagram of diagnostic validity in seizure‐free individuals after surgery (n = 24). (A) The inner circle indicates the resected area. The four outer circles represent the four diagnostic modalities EEG, MRI, visual SPECT assessment (VSA), and ictal‐interictal SPECT Analyses by SPM (ISAS). The overlap of the modalities with the resection area indicates the percentage of cases in which the respective modality was localizing (Category A or B). The fraction not overlapping with the resection area indicates the percentage of cases in which the modality was not localizing (Category C, D or E). (B) The overlap of the presurgical modalities inter se is shown. The total size of localizing results within each modality is visualized by the lower left bar plot. Every possible intersection is represented by the lower right plot, and number of their occurrence is shown on the top bar plot. The dark blue dots show that the modality is localizing the resected area, the light blue dots show the modality is not localizing. In sum, the displayed combinations result in the 24 individuals with epilepsy.
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