Interictal Single Photon Emission Computed Tomography Research Articles

Ictal and interictal SPECT with 99m Tc-HMPAO in presurgical epilepsy. II: Methodological considerations onhyper- and hypoperfusion.

Single-photon emission computed tomography (SPECT) with the tracer 99m Tc-HMPAO is a method to visualize the cerebral hyperperfusion during an epileptic seizure and thus localize the epileptogenic zone and seizure propagation. Subtraction of interictal from Ictal SPECT Co-registered to MRI (SISCOM) visualizes areas with relative increases in cerebral blood flow. The purpose of this retrospective study is to explore the added value of visualizing areas of hypoperfusion as well as hyperperfusion, so-called reversed SISCOM. Fifty-six patients operated for epilepsy who had been investigated with SISCOM were included in the analysis. The patients were divided into two groups based on seizure duration after tracer injection, above or below 30 s. The preoperative SISCOM description was compared to the area of resection and given a concordance score. The 56 SISCOM were recalculated visualizing also areas of hypoperfusion and again compared to the site of resection using the same scale of concordance. The reversed SISCOM were categorized into three subgroups: "Altered Conclusion," "Confirmed Conclusion," and "Adds Nothing." If an area of hyperperfusion had an area of hypoperfusion in close proximity, it was re-interpreted as noise, thus possibly altering the conclusion. If the areas of hypoperfusion were in the opposite hemisphere it was interpreted as confirming factor. Further the concordance scores from conventional SISCOM and reversed SISCOM was compared to surgical outcome to explore the difference in sensitivity, positive predictive value (PPV), and odds ratio. In approximately half of the cases reversed SISCOM added additional value, meaning either altered the conclusion or confirmed the conclusion. The sensitivity, PPV, and odds ratio was also better in the subgroup of long, >30 s seizure duration after injection, and got worse in the group with short, <30 s seizure duration after injection. Adding reversed SISCOM performed better than conventional SISCOM at predicting good surgical outcome.

Ictal Single Photon Emission Computed Tomography (SPECT) In Patients with Focal Aware Seizure without Ictal Electroencephalographic Changes: A Single Center Experience (P2-1.012)

<h3>Objective:</h3> N/A <h3>Background:</h3> There is currently limited literature on the localization value of ictal SPECT tracer injection during patient-reported typical focal aware seizures (auras) that lack electrographic changes. One study reported that ictal SPECT studies in isolated auras lack reliability, with concordant localization with the seizure onset zone obtained in 5%, and lateralization in 35% of cases. In another study, localizing information of self-injection of ictal SPECT was better in three patients and obviated the need for intracranial monitoring in one patient. We present a study in which tracer injection was administered for patient-reported typical focal aware seizures, where the subsequent analysis of ictal and interictal SPECT helped inform further management. <h3>Design/Methods:</h3> We performed a retrospective review of cases who underwent ictal SPECT between 2020 to 2022 at University of Kentucky hospital. Cases with radiotracer injection during patient-reported auras lacking electrographic changes were identified. Timing of injection from onset of reported aura, hyperperfusion changes on ictal SPECT, and the outcome of imaging on further management of refractory epilepsy were noted. <h3>Results:</h3> 20 patients underwent ictal SPECT, of which 7 met our inclusion criteria. None of the 7 cases had electrographic correlate with aura on scalp EEG. Time of tracer injection ranged from 1–17 seconds following onset of aura. The ictal SPECT changes correctly localized the seizure onset zone in five patients. This was followed by intracranial monitoring and subsequent temporal lobectomy in three patients, interventricular ablation of epileptogenic focus in one patient, and Responsive Neurostimulation implant in one patient. One patient was managed medically, and one is ongoing pre-surgical evaluation. <h3>Conclusions:</h3> Ictal SPECT with radiotracer injection during typical focal aware seizures (patient reported auras) without ictal electrographic changes is helpful in the localization of the seizure onset zone. Additional studies with larger sample size and outcome information are needed to assess accuracy of localization. <b>Disclosure:</b> Dr. Pervin has nothing to disclose. Dr. Khan has received personal compensation for serving as an employee of University of Kentucky. Dr. Clay has nothing to disclose. Riham El Khouli has nothing to disclose. Dr. Mirza has nothing to disclose. Dr. Mathias has received research support from My Epilepsy Society Non Profit Organization.

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

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. 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. 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. 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.

Brain perfusion single photon emission computed tomography abnormality in MRI-negative stroke-like patients post COVID-19 vaccination.

Stroke-like symptoms after COVID-19 vaccination was thought to be functional if there was no anatomical image abnormality. We aimed to analyze brain perfusion changes in these patients. A case-control study of brain perfusion single photon emission computed tomography (SPECT) of 12 vaccinated patients with left-sided stroke-like symptoms were compared with 12 age- and gender-matched normal interictal brain SPECTs using voxel-based analysis. Significant hyperperfusion was seen on the right side in postcentral, inferior parietal, mid temporal, parahippocampal, and caudate regions, and on the left side in the thalamus, hippocampus, and mid temporal areas. In addition, there were hypoperfused bilateral superior frontal gyri and right mid/posterior cingulate cortex (Family-wise-error corrected p-values < .05). Both hypoperfusion and hyperperfusion in the brain are demonstrated. We hypothesize that these findings might be the result of the functional neurological disorder. However, based on other previous studies, circulating spike protein in the patients' plasma early after vaccination might also be the cause.

Relation of Brain Perfusion Patterns to Sudden Unexpected Death Risk Stratification: A Study in Drug Resistant Focal Epilepsy.

To explore the role of the interictal and ictal SPECT to identity functional neuroimaging biomarkers for SUDEP risk stratification in patients with drug-resistant focal epilepsy (DRFE). Twenty-nine interictal-ictal Single photon emission computed tomography (SPECT) scans were obtained from nine DRFE patients. A methodology for the relative quantification of cerebral blood flow of 74 cortical and sub-cortical structures was employed. The optimal number of clusters (K) was estimated using a modified v-fold cross-validation for the use of K means algorithm. The two regions of interest (ROIs) that represent the hypoperfused and hyperperfused areas were identified. To select the structures related to the SUDEP-7 inventory score, a data mining method that computes an automatic feature selection was used. During the interictal and ictal state, the hyperperfused ROIs in the largest part of patients were the bilateral rectus gyrus, putamen as well as globus pallidus ipsilateral to the seizure onset zone. The hypoperfused ROIs included the red nucleus, substantia nigra, medulla, and entorhinal area. The findings indicated that the nearly invariability in the perfusion pattern during the interictal to ictal transition observed in the ipsi-lateral putamen F = 12.60, p = 0.03, entorhinal area F = 25.80, p = 0.01, and temporal middle gyrus F = 12.60, p = 0.03 is a potential biomarker of SUDEP risk. The results presented in this paper allowed identifying hypo- and hyperperfused brain regions during the ictal and interictal state potentially related to SUDEP risk stratification.

Surgical Outcome in Extratemporal Epilepsies Based on Multimodal Pre-Surgical Evaluation and Sequential Intraoperative Electrocorticography

Objective: to present the postsurgical outcome of extratemporal epilepsy (ExTLE) patients submitted to preoperative multimodal evaluation and intraoperative sequential electrocorticography (ECoG). Subjects and methods: thirty-four pharmaco-resistant patients with lesional and non-lesional ExTLE underwent comprehensive pre-surgical evaluation including multimodal neuroimaging such as ictal and interictal perfusion single photon emission computed tomography (SPECT) scans, subtraction of ictal and interictal SPECT co-registered with magnetic resonance imaging (SISCOM) and electroencephalography (EEG) source imaging (ESI) of ictal epileptic activity. Surgical procedures were tailored by sequential intraoperative ECoG, and absolute spike frequency (ASF) was calculated in the pre- and post-resection ECoG. Postoperative clinical outcome assessment for each patient was carried out one year after surgery using Engel scores. Results: frontal and occipital resection were the most common surgical techniques applied. In addition, surgical resection encroaching upon eloquent cortex was accomplished in 41% of the ExTLE patients. Pre-surgical magnetic resonance imaging (MRI) did not indicate a distinct lesion in 47% of the cases. In the latter number of subjects, SISCOM and ESI of ictal epileptic activity made it possible to estimate the epileptogenic zone. After one- year follow up, 55.8% of the patients was categorized as Engel class I–II. In this study, there was no difference in the clinical outcome between lesional and non lesional ExTLE patients. About 43.7% of patients without lesion were also seizure- free, p = 0.15 (Fischer exact test). Patients with satisfactory seizure outcome showed lower absolute spike frequency in the pre-resection intraoperative ECoG than those with unsatisfactory seizure outcome, (Mann– Whitney U test, p = 0.005). Conclusions: this study has shown that multimodal pre-surgical evaluation based, particularly, on data from SISCOM and ESI alongside sequential intraoperative ECoG, allow seizure control to be achieved in patients with pharmacoresistant ExTLE epilepsy.

SPECT activation patterns in psychogenic non-epileptic seizures in temporal lobe epilepsy patients

IntroductionThe diagnosis of psychogenic non-epileptic seizures (PNES) can often be challenging. When video-electroencephalography (EEG) is not conclusive, single-photon emission computed tomography (SPECT) can be useful by quantifying changes in regional cerebral blood flow (rCBF). MethodsWe conducted a retrospective case-control study in adult patients with pharmacoresistant temporal lobe epilepsy (TLE). Those patients with an ictal SPECT obtained during an event finally diagnosed as PNES were included as cases (PNES+). The control group consisted of patients with TLE without PNES (PNES-). Clinical episodes were analysed and classified according to PNES subtypes. Subtraction ictal SPECT coregistered to MRI (SISCOM) analysis was performed for the detection of areas with significant changes in perfusion compared to individual interictal studies. Group comparisons in SPM12 included paired t-tests of ictal vs. interictal studies in each group of temporal lobe seizures and PNES events. ResultsTen patients with TLE and PNES were included. We found no patterns of regional hyperperfusion typical of TLE seizures during the PNES events. In two of these cases, an ictal SPECT during a confirmed epileptic seizure was also obtained, showing antero-mesial temporal lobe hyperperfusion. Group comparisons between ictal and interictal SPECTs showed increased rCBF in the temporal lobe with reduced perfusion in the default mode network areas and cerebellum during temporal lobe seizures in PNES- patients and decreased perfusion restricted to the posterior parietal cortex without significant rCBF increases in PNES events. ConclusionsIctal SPECT can be a helpful tool to characterize rCBF changes in PNES and for differential diagnosis with seizures in TLE patients.

MNI SISCOM: an Open-Source Tool for Computing Subtraction Ictal Single-Photon Emission CT Coregistered to MRI.

Subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM) is a well-established technique for quantitative analysis of ictal vs interictal SPECT images that can contribute to the identification of the seizure onset zone in patients with drug-resistant epilepsy. However, there is presently a lack of user-friendly free and open-source software to compute SISCOM results from raw SPECT and MRI images. We aimed to develop a simple graphical desktop application for computing SISCOM. MNI SISCOM is a new free and open-source software application for computing SISCOM and producing practical MRI/SPECT/SISCOM image panels for review and reporting. The graphical interface allows any user to quickly and easily obtain SISCOM images with minimal user interaction. Additionally, MNI SISCOM provides command line and Python interfaces for users who would like to integrate these features into their own scripts and pipelines. MNI SISCOM is freely available for download from: https://github.com/jeremymoreau/mnisiscom .

Injection of prophylactic lorazepam versus antiseizure drugs on the localization value of ictal SPECT studies and treatment-emergent adverse events: A single-center prospective study

ObjectiveWe aimed to examine the impact of resumption of home antiseizure drugs alone (ASD−) compared with adjunct administration of scheduled intravenous (IV) lorazepam 2 mg every 6 h (ASD+) following ictal single-photon emission computed tomography (SPECT) injection on the localization value of SPECT studies and treatment-emergent adverse events (TEAEs). MethodsWe conducted a prospective study at Mayo Clinic inpatient epilepsy monitoring unit (EMU) between January 2018 and May 2020 in Jacksonville, Florida. The ASD− and ASD+ groups were compared for concordance of SPECT studies with the epilepsy surgical conference (ESC) consensus or intracranial electroencephalography (icEEG) findings as reference. Treatment-emergent adverse events, obtained from surveys at 24 h and one week postictal SPECT injection, were also compared between both groups. ResultsTwenty-two consecutive patients with temporal (eight patients, 36%) and extratemporal (14 patients, 64%) epilepsy were included: 12 ASD+ and 10 ASD−. The two groups were well matched with regard to clinical and ictal SPECT injection characteristics including the occurrence of seizure between ictal and interictal SPECT injections. The localization value of SPECT studies was similar in the two groups. Patients in the ASD+ group reported higher rates of dizziness and excessive sedation at 24 h (p-value = 0.008). Fourteen patients (64%) underwent icEEG monitoring. For the entire cohort, the localization concordance of SPECT analysis by statistical parametric mapping (SPM) was superior to raw ictal SPECT (p-value = 0.003) and subtraction ictal SPECT coregistered to magnetic resonance imaging (MRI) (SISCOM; p-value = 0.021). Eventually, seven patients (31.8%) underwent resective brain surgery of whom four (57.1%) became seizure-free (median follow-up = 22 months). ConclusionsOur findings suggest that resuming home ASDs without the addition of scheduled IV lorazepam following inpatient ictal SPECT injection is equally efficacious for seizure onset zone (SOZ) localization on SPECT studies, especially SPM. This approach is also associated with fewer transient TEAEs and lower financial cost with no difference in preventing seizure between ictal and interictal SPECT injections.

Utility of single-photon emission computed tomography (SPECT) in presurgical evaluation of children: A single-center experience

ObjectiveSingle-photon emission computed tomography (SPECT) is an ancillary noninvasive test commonly used to identify the epileptogenic zone. However, its proper utilization may be limited depending on the resources available at each center. This study aimed to investigate the utility of SPECT in presurgical evaluation of children at our center. MethodsThis was an observational retrospective study in 150 children who were admitted to the Epilepsy Monitoring Unit for presurgical evaluation between 2012 and 2019. The utility of interictal and ictal SPECT in different clinical cohorts was analyzed. ResultsOnly interictal SPECT was performed on 87 patients (58 %), while ictal SPECT was performed on 62 (41.3 %), and interictal SPECT alone was considered of low diagnostic value. Ictal SPECT was unremarkable in 27 of 62 patients and abnormal in 35. Ictal SPECT was localized to the temporal lobe in 62.8 % and to the extratemporal lobe in 25.7 % of the patients and lateralized to one hemisphere in 11.4 % of the patients. In the abnormal SPECT group, ictal SPECT was considered unnecessary in 7/35 (20 %) patients with a single lesion and 3/35 (8.5 %) patients with a hemispheric lesion. In the remaining 25 patients, surgery was recommended more frequently than invasive EEG monitoring (IEM) for diffuse lesion cases (P = 0.03), while IEM was recommended more frequently than surgery for MRI-negative cases (P = 0.03), and in this group none of the MRI-negative patients underwent surgery. In our entire cohort, epilepsy surgery was performed on 24.4 % of the patients, 64 % with a single lesion, 7.6 % with a hemispheric lesion, 25.6 % with a diffuse lesion, and only one MRI-negative patient (2.5 %). Surgery was performed in 48.7 % of single lesion cases and 20.5 % of diffuse lesion cases with either unremarkable or no ictal SPECT. Engel class I outcome was achieved in 62 % and class II outcome in 33 % of the patients. In the single lesion etiology, 72 % (18/25) patients achieved excellent outcome and within this group, 22 % (4/18) patients had a positive ictal SPECT whereas 78 % (14/18) patients either did not get an ictal SPECT or it was unremarkable. SignificanceBased on our findings, we suggest carefully selecting patients for SPECT imaging to improve its utility and prevent overutilization and potential harm to children.

A Novel Noninvasive Approach Based on SPECT and EEG for the Location of the Epileptogenic Zone in Pharmacoresistant Non-Lesional Epilepsy.

Background and objectives: The aim of this study is to propose a methodology that combines non-invasive functional modalities electroencephalography (EEG) and single photon emission computed tomography (SPECT) to estimate the location of the epileptogenic zone (EZ) for the presurgical evaluation of patients with drug-resistant non-lesional epilepsy. Materials and Methods: This methodology consists of: (i) Estimation of ictal EEG source imaging (ESI); (ii) application of the subtraction of ictal and interictal SPECT co-registered with MRI (SISCOM) methodology; and (iii) estimation of ESI but using the output of the SISCOM as a priori information for the estimation of the sources. The methodology was implemented in a case series as an example of the application of this novel approach for the presurgical evaluation. A gold standard and a coincidence analysis based on measures of sensitivity and specificity were used as a preliminary assessment of the proposed methodology to localize EZ. Results: In patients with good postoperative evolution, the estimated EZ presented a spatial coincidence with the resection site represented by high values of sensitivity and specificity. For the patient with poor postoperative evolution, the methodology showed a partial incoherence between the estimated EZ and the resection site. In cases of multifocal epilepsy, the method proposed spatially extensive epileptogenic zones. Conclusions: The results of the case series provide preliminary evidence of the methodology’s potential to epileptogenic zone localization in non-lesion drug-resistant epilepsy. The novelty of the article consists in estimating the sources of ictal EEG using SISCOM result as a prior for the inverse solution. Future studies are necessary in order to validate the described methodology. The results constitute a starting point for further studies in order to support the clinical reliability of the proposed methodology and advocate for their implementation in the presurgical evaluation of patients with intractable non-lesional epilepsy.

Non-invasive Seizure Localization with Ictal Single-Photon Emission Computed Tomography is Impacted by Preictal/Early Ictal Network Dynamics.

More than one third of children with epilepsy have medically intractable seizures. Promising therapies, including targeted neurostimulation and surgery, depend on accurate localization of the epileptogenic zone. Ictal perfusion Single-Photon Emission Computed Tomography (SPECT) can localize the seizure focus noninvasively, with comparable accuracy to that of invasive EEG. However, multiple factors including seizure dynamics may affect its spatial specificity. Using subtracted ictal from interictal SPECT and scalp EEG from 118 pediatric epilepsy patients (40 of whom had surgery after the SPECT studies), information theoretic measures of association and advanced statistical models, this study investigated the impact of preictal and ictal brain network dynamics on SPECT focality. Network dynamics significantly impacted the SPECT localization ~30 s before to ~45 s following ictal onset. Distributed early ictal connectivity changes, indicative of a rapidly evolving seizure, were negatively associated with SPECT focality. Spatially localized connectivity changes later in the seizure, indicating slower seizure propagation, were positively associated with SPECT focality. In the first ~60 s of the seizure, significantly higher network connectivity was estimated in an area overlapping with the area of hyperperfusion. Finally, ~75% of patients with Engel class 1a/1b outcomes had SPECTs that were concordant with the resected area. Slowly evolving seizures are more likely to be accurately imaged with SPECT, and the identified focus may overlap with brain regions where significant topological changes occur. Measures of preictal/early ictal network dynamics may help optimize the SPECT localization, leading to improved surgical and neurostimulation outcomes in refractory epilepsy.

Brain molecular imaging in pharmacoresistant focal epilepsy: Current practice and perspectives

This review aims to synthesize all the available data on brain molecular imaging, such as single-photon emission computed tomography (SPECT) and interictal fluorodeoxyglucose positron emission tomography (FDG-PET), in focal epilepsies. SPECT imaging is able to measure regional cerebral blood flow and its major innovation remains its ictal imaging value. On the other hand, FDG-PET, which has higher spatial resolution and lower background activity than SPECT, enables glycolytic metabolism to be identified in interictal states. Therefore, interictal FDG-PET has greater sensitivity than interictal SPECT, especially in temporal lobe epilepsies (TLEs). Thus, 18F-FDG-PET is a necessary step in the presurgical evaluation of TLEs, but also of extratemporal epilepsies (ETEs), contributing to >30% of the decision to undertake surgery. In addition, FDG-PET has particular diagnostic value in focal epilepsies showing normal magnetic resonance imaging (MRI). PET also has good prognostic value for post-surgical outcomes as well as cognitive impairment, especially in cases where the hypometabolism extent is limited. Moreover, the notion of an epileptic network is well highlighted by functional PET imaging, allowing better understanding of the pathological substrates of these disorders. Future development of quantitative analysis software and of novel radiotracers and cameras will certainly enhance its clinical usefulness.

Functional neuroimaging findings in patients with lateral and mesio-lateral temporal lobe epilepsy; FDG-PET and ictal SPECT studies.

The differentiation of combined mesial and lateral temporal onset of seizures (mesio-lateral TLE, MLTLE) from lateral TLE (LTLE) is critical to achieve good surgical outcomes. However, the functional neuroimaging features in LTLE patients based on the ictal onset zone utilizing intracranial EEG (iEEG) in a large series have not been investigated. We enrolled patients diagnosed with MLTLE (n = 35) and LTLE (n = 53) based on the site of ictal onset zone from iEEG monitoring. MLTLE is defined when ictal discharges originate from the mesial and lateral temporal cortices independently, whereas seizures of LTLE arise exclusively from the lateral temporal cortex. Compared to patients with LTLE, patients with MLTLE were more likely to have 18F- fluorodeoxyglucose positron emission tomography (FDG-PET) hypometabolism and hyperperfusion on ictal single-photon emission computed tomography (SPECT) restricted to the temporal areas. MLTLE patients had more frequent aura or secondarily generalized seizures than LTLE patients. No significant differences were found in scalp EEG, MRI, and Wada asymmetry between groups. The overall seizure-free rate was good (73.8%, mean follow-up = 9.7 years), which was not different (Engel class I, 74.3% in MLTLE vs. 73.6% in LTLE). Postsurgical memory function was spared in LTLE patients, while visual memory was impaired in MLTLE patients when their mesial temporal structures were sufficiently resected. It suggests that functional neuroimaging (interictal PET and ictal and interictal SPECT) may play a crucial role to differentiate between MLTLE and LTLE.

Nuclear Medicine Imaging in Epilepsy

For epilepsy patients who are not responding to anticonvulsant medications, surgery is an alternative treatment. A key issue in epilepsy surgery is the accurate localization of the “epileptogenic zone”. To date, pre-surgical evaluation of the epileptogenic network can be carried out by Electroencephalogram (EEG), video-EEG, magnetic resonance imaging, magneto-encephalography, single-photon emission computed tomography (SPECT) and positron emission tomography (PET). The interictal FDG-PET reveals hypometaboism at the epileptic focus, and it has been demonstrated to be much more sensitive than the interictal SPECT, and similarly sensitive to the ictal SPECT for the accurate localization of epileptogenic foci prior to surgical therapy. Visual assessment of 18F-FDG-PET is associated with interobserver and intraobserver variability. We have studied the issues of rigorous quantitation of FDG-PET brain studies and developed self-normalization technique. In addition to FDG-PET imaging, PET receptor imaging has also been demonstrated to provide significant insight into the mechanisms of neurotransmitters in epileptogenesis. In conclusion, we believe that nuclear medicine imaging can facilitate the identification of epileptic foci and investigate novel treatment for epilepsy.

Hot water epilepsy: Phenotype and single photon emission computed tomography observations.

We studied the anatomical correlates of reflex hot water epilepsy (HWE) using multimodality investigations viz. magnetic resonance imaging (MRI), electroencephalography (EEG), and single photon emission computed tomography (SPECT). Five men (mean age: 27.0 ΁ 5.8 years) with HWE were subjected to MRI of brain, video-EEG studies, and SPECT scan. These were correlated with phenotypic presentations. Seizures could be precipitated in three patients with pouring of hot water over the head and semiology of seizures was suggestive of temporal lobe epilepsy. Ictal SPECT showed hyperperfusion in: left medial temporal — one, left lateral temporal — one, and right parietal — one. Interictal SPECT was normal in all five patients and did not help in localization. MRI and interictal EEG was normal in all the patients. The clinical and SPECT studies suggested temporal lobe as the seizure onset zone in some of the patients with HWE.

Ictal single photon emission computed tomography in epileptic auras

Little is known about whether ictal single photon emission computed tomography (SPECT) during an isolated aura can localize the epileptogenic zone (EZ). This study seeks to evaluate the yield of ictal SPECT injection in isolated epileptic auras. We identified 20 patients with focal epilepsy studied during 26 isolated auras by ictal interictal subtraction SPECT coregistered to magnetic resonance imaging (SISCOM). Studies were rated by two readers who blindly scored the images for presence or absence of an area of dominant hyperperfusion and the lateralization and localization of ictal hyperperfusion; kappa statistics were calculated. Results are correlated with the localization or lateralization of the EZ, time of injection, and electroencephalography (EEG) findings during aura. Fourteen (53%) of 26 injections in 13 patients were rated by both readers as having an area of dominant hyperperfusion with poor interobserver agreement (k = 0.128). Nine of 26 injections in eight patients were correctly lateralized to the side of the EZ (κ = 0.46), but only one of 21 injections in one patient was correctly localized (κ = 0.146). No difference was found when comparing temporal and extratemporal cases. Studies obtained in auras with ictal EEG change were no more likely to be correctly localized than in ones without (p = 0.19). The timing of injection was not a predictor of success. Ictal SPECT injection during an isolated aura has a low yield of correct localization of the EZ and cannot be relied on alone during presurgical evaluation. A repeat injection during a seizure with clinical signs and ictal EEG accompaniment is recommended.

Tonic seizures ofLennox‐Gastaut syndrome: Periictal single‐photon emission computed tomography suggests a corticopontine network

Lennox-Gastaut syndrome (LGS) is a severe epileptic disorder with characteristic electroclinical features but diverse etiologies. The shared electroclinical characteristics suggest that common cerebral networks are involved in generating seizures. We sought to reveal these networks by comparing ictal and interictal single-photon emission computed tomography (SPECT). We identified 10 ictal-interictal SPECT pairs from seven patients with LGS (median age 11years; range 1-38) who were studied during video electroencephalography (EEG)-confirmed tonic seizures. We performed a voxel-wise comparison of ictal and interictal SPECT studies across the group. The evolution of blood flow changes was explored by examining early and late injection groups. Median duration of tonic seizures was 10s (range 6-29 s), and injection latency from seizure offset was -8 to 48s. In the early injection group (<10s; three studies), there was hyperperfusion over pons and cerebellar hemispheres (p<0.05 cluster corrected family wise error), and hypoperfusion bilaterally over the pericentral region, with a trend toward hyperperfusion over bilateral superior and middle frontal gyri, and lateral parietal cortex. In the late injection group, there was hyperperfusion over midline and lateral cerebellar regions, with hypoperfusion widely over bilateral frontal regions. This study suggests that the tonic seizures of LGS result from activity in a network, containing bilateral frontal and parietal association areas and the pons. We postulate that tonic seizures recruit the corticoreticular system, which connects frontal attentional areas to the pontine reticular formation, and is normally responsible for postural tone and orienting behavior.

The Localizaing Value of Ictal SPECT during Auras in Focal Epilepsy (P03.109)

Objective: To evaluate the localizing value of Ictal Single Photon Emission Computed Tomography (SPECT) in isolated epileptic auras. Background Ictal SPECT is an important test to localize the epileptogenic zone (EZ) with an earlier injection reported as more successful. The epileptic aura is the earliest symptom of a seizure but there are little data on whether ictal SPECT injection during an isolated aura can localize the EZ. Design/Methods: From 529 ictal SPECT studies between 2003 and 2011 we identified 21 patients (5%) with focal epilepsy who had 27 ictal SPECT injections during isolated auras. Ictal and interictal SPECT studies were obtained using 99m TC-ECD as isotope, co-registered, normalized, subtracted, and transformed into a z-score and fused with the MRI (SISCOM). Studies were rated by 2 readers who blindly scored the SPECT for: presence or absence, lateralization, and localization of dominant hyperperfusion, and kappa statistics were calculated. Results are compared to aura type, time of injection, EEG findings during aura, and final localization or lateralization of the EZ based on consensus of scalp EEG, MRI, PET; invasive EEG, and post-operative outcome. Results: 8 patients had temporal, 4 frontal, 2 temporo-parietal, 1 fronto-temporal and 6 hemispheric epilepsy. The EZ was localized in 15 and lateralized in 6. Two readers agreed that 14/27 (52%) studies in 13/21 patients showed an area of dominant hyperperfusion with poor interobserver agreement (kappa=0.10). Of these 9/21 (43%) studies in 9/21 patients were correctly lateralized (kappa = 0.42 ) and only 1/15 studies in 1/15 patients were correctly localized (kappa=0.12). Studies obtained in auras with ictal EEG change were no more likely to be correctly localized (p=0.15). The timing of injection was not a predictor of success. Conclusions: Ictal SPECT injection during isolated auras has a low yield of correct localization of the EZ. Disclosure: Dr. So has nothing to disclose. Dr. Elwan has nothing to disclose. Dr. Alexopoulos has received personal compensation for activities with UCB Pharma as a speaker. Dr. Huang has nothing to disclose. Dr. Wu has nothing to disclose.

Decreased benzodiazepine receptor and increased GABA level in cortical tubers in tuberous sclerosis complex

PurposeTo elucidate the functional characteristics of cortical tubers that might be responsible for epilepsy in tuberous sclerosis complex (TSC), proton magnetic resonance spectroscopy (1H-MRS) and [123I] iomazenil (123I-IMZ) single photon emission computed tomography (SPECT) were performed. Methods1H-MRS using a clinical 3-tesla magnetic resonance imager was performed in four children with TSC and 10 age-and sex-matched healthy control subjects. A single voxel was set on the right parietal lobe in control subjects. In patients with TSC, a single voxel was set on the epileptogenic tuber in the parietal or temporal lobe, and another voxel was set on the contralateral normal-appearing brain region. N-Acetylaspartate (NAA), myo-Inositol (mIns) and Glutamate (Glu) were analyzed using a conventional STEAM (Stimulated Echo Acquisition Mode) method. The concentration of gamma-aminobutyric acid (GABA) was quantified using MEGA-Point Resolved Spectroscopy (PRESS). Interictal 123I-IMZ SPECT was examined in all four patients with TSC. ResultsA significant decrease in the NAA concentration and significant increases in the mIns and GABA concentrations were detected in the cortical tubers of all 4 patients. No significant difference was observed in Glu concentrations. In all of the cortical tubers detected by magnetic resonance imaging, 123I-IMZ binding was significantly decreased. ConclusionEpileptogenesis in TSC might be caused by decreased inhibition secondary to the decrease in GABA receptors in dysplastic neurons of cortical tubers. An increase in the GABA concentration may compensate for decreased inhibition.