Prospective use of subtraction ictal SPECT coregistered to MRI (SISCOM) in presurgical evaluation of epilepsy

Abstract

SUMMARYPurpose: In patients with drug-refractory focal epilepsy, nonlesional magnetic resonance imaging (MRI) or discordant data of presurgical standard investigations leads to failure generating a sufficient hypothesis for electrode implantation or epilepsy surgery. The seizure-onset zone can be further investigated by subtraction ictal singlephoton emission computed tomography (SPECT) coregistered to MRI (SISCOM). This is an observational study of a large consecutive cohort of patients undergoing prospective SISCOM to generate hypothesis for electrode implantation or site of epilepsy surgery. Methods: One hundred seventy-five consecutive patients undergoing presurgical evaluation with either nonlesional MRI or discordant data of standard investigations preventing the generation of hypothesis for seizure onset were evaluated with SISCOM. Results were compared to gold standard for seizure onset detection, either electrocorticography (ECoG) and/or postoperative outcome. Key Findings: One hundred thirty patients had successful SPECT injection. Hypothesis for electrode implantation/ site of surgery was generated in 74 patients. Forty patients had gold standard comparison. Twenty-eight patients underwent resective surgery. SISCOM was concordant to site of surgery in 82%. An additional 12 patients underwent invasive EEG monitoring but were not suitable for surgery. SISCOM was concordant multifocal in 75%. Two years postsurgical follow-up of 26 patients showed favorable outcome in 22 (Engel class I and class II). Significance: SISCOM is a highly valuable diagnostic tool to localize the seizure-onset zone in nonlesional and extratemporal epilepsies. Outcome in this patient group was unexpectedly good, even in patients with nonlesional MRI. The high correlation with ECoG and site of successful surgery is a strong indicator that outcome prediction in this patient group should be adapted accordingly, which may encourage more patients to undergo electrode implantation and subsequent successful surgery. Statistical analysis showed that SISCOM with shorter duration of seizures, focal seizures, and lesional MRI was more likely to generate implantation hypothesis. KEY WORDS: Epilepsy, Neurosurgery, Human, SPECT, MRI, EEG.Localization of the epileptogenic zone in patients with drug-refractory partial epilepsy undergoing presurgical evaluation is challenging. Standard investigations include epilepsy-dedicated magnetic resonance imaging (MRI) brain, simultaneous video-electroencephalography (EEG) long-term monitoring, and neuropsychological testing. However, in a considerable number of patients these tests might not exactly reveal the epileptogenic zone. In those cases the test results might be used to generate a hypothesis of intracranial electrode placement to further investigate the seizure-onset zone. Particularly in extratemporal epilepsies and patients with normal MRI results it is more likely that no conclusive hypothesis for seizure-onset zone can be generated and further tests are necessary.Ictal single-photon emission c...

Clinical Role of Subtraction Ictal SPECT Coregistered to MR Imaging and18F-FDG PET in Pediatric Epilepsy

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A new method for intraoperative localization of epilepsy focus by means of a gamma probe

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“…Such lesions may be or not be visible to the naked eye, and their identification may require some preoperative or even intraoperative techniques, including morphological methods (CT and MRI), functional methods (SPECT, PET, EEG) or electrocorticography (10) . Other intraoperative methods such as MRI and CT imply high costs and are available only in a few centers around the world (10) . A feasible alternative would be the utilization of neuronavigation surgery (11) , whose hardware can be rented.…”

Refractory Nonlesional Neocortical Epilepsy: Current Trends

“…Furthermore, small differences between ictal and interictal SPECT and variability in overall intensity and orientation make visual side by side interpretation of EZs difficult. Subtraction ictal SPECT coregistered with MRI (SISCOM) largely solves these problems, and compared to subtraction ictal SPECT and FDG-PET, SISCOM shows better concordance with iEEG, particularly for extratemporal epilepsy [52][53][54][55]. EZ localization by SISCOM has been shown to predict a favorable outcome of epilepsy surgery [52][53][54]56].…”

“…Subtraction ictal SPECT coregistered with MRI (SISCOM) largely solves these problems, and compared to subtraction ictal SPECT and FDG-PET, SISCOM shows better concordance with iEEG, particularly for extratemporal epilepsy [52][53][54][55]. EZ localization by SISCOM has been shown to predict a favorable outcome of epilepsy surgery [52][53][54]56]. It is important to note that localizability in these studies were dependent in part on early radiotracer injection times [43,52].…”