Ictal SPECT

Regional cerebral blood perfusion impairment in type 1 narcolepsy patients: An arterial spin labeling study

OBJECTIVE

To investigate the pathophysiological characteristics of cerebral blood flow (CBF) in patients with narcolepsy type 1 (NT1) via the arterial spin labeling (ASL) technique.

METHODS

Thirty patients with diagnostic NT1 (PTs) and 34 age- and sex-matched healthy controls (HCs) were recruited for this study. Basic information was collected, and clinical evaluation and neuroimaging, including ASL and T1-3DBRAVO, was performed. The z-normalized CBF (zCBF) and spatial coefficient of variation (sCoV) were calculated, and the changes in NT1 were compared via analysis of covariate (ANCOVA). Furthermore, spearman's correlation analysis between impaired regional perfusion and clinical features was performed. Age, sex, and normalized grey matter volume were included as covariates.

RESULTS

Compared with that of HCs, the zCBF of PTs significantly differed in regions of fronto-temporal-occipital cortex, right insula and posterior insula, and left rostral/dorsal anterior cingulate gyrus (ACG) (P < 0.006). Moreover, the sCoV was significantly altered in the frontotemporal cortex, rostral ACG, right hippocampus, and posterior insula (P < 0.003). In PTs, positive correlations were identified between the zCBF of the right superior/middle frontal gyrus (SFG/MFG) and mean sleep latency, and between the zCBF of the left SFG of the frontal pole and sleep hallucination severity. Moreover, the sCoV of the right MFG/hippocampus were positively associated with Rapid Eye Movement efficiency and negatively associated with Hamilton Anxiety Scale score, respectively.

CONCLUSION

PTs exhibited abnormal regional perfusion in the frontal-temporal-occipital cortex and limbic system regions, which may serve as patient-specific imaging markers. Alterations in perfusion may lead to the clinical manifestations of underlying psychological and sleep disorders in PTs.

Ictal SPECT success rate using a single SPECT session protocol

INTRODUCTION

Ictal single-photon emission computed tomography (SPECT) provides additional information on the localisation of the epileptogenic zone. However, ictal SPECT is labour-intensive and expensive. We have developed a more affordable protocol with a single SPECT radiotracer session during a 48-hour video-EEG monitoring (VEM). This study aimed to determine the success rate of ictal SPECT with a single SPECT session (HMPAO or ECD).

METHODS

This retrospective observational study included all VEM cases performed in the University Malaya Medical Centre, Kuala Lumpur, Malaysia from 1st January 2011 to 30th April 2024, with SPECT as part of the pre-surgical evaluation.

RESULTS

A total of 189 cases were included. The mean age was 33.3 years old (range 9-68), and 105 (55.6 %) were male. The mean baseline seizure frequency before VEM was 21.8 per month. The mean number of seizures recorded during a 48-hour VEM was 10.9. A total of 44 (23.3 %) patients had ictal SPECT with a single SPECT session. Ictal SPECT was significantly associated with a higher number of seizures during 48-hour VEM (31.5 ± 58.7 vs 4.4 ± 6.3, p < 0.001) and younger age (29.9 ± 11.8 vs 34.2 ± 11.9, p < 0.05). On multivariate analysis, only the number of seizures during 48-hour VEM was a significant predictor for ictal SPECT (95 % CI, 1.03-1.12; odds ratio, 1.073; p = 0.002). Those with at least three seizures during VEM had a ≥ 30 % chance of having ictal SPECT and ≥ 40 % in those with six or more seizures.

CONCLUSION

A single SPECT session on day 3 of VEM can be a cost-effective option, particularly in those patients with multiple seizures in the first 48 hours of monitoring following a fast medication taper.

Epilepsy surgery in children with operculoinsular epilepsy: Results of a large unicentric cohort

OBJECTIVE

Epilepsy surgery in the operculoinsular cortex is challenging due to the difficult delineation of the epileptogenic zone and the high risk of postoperative deficits.

METHODS

Pre- and postsurgical data from 30 pediatric patients who underwent operculoinsular cortex surgery at the Motol Epilepsy Center Prague from 2010 to 2022 were analyzed.

RESULTS

Focal cortical dysplasia (FCD; n = 15, 50%) was the predominant cause of epilepsy, followed by epilepsy-associated tumors (n = 5, 17%) and tuberous sclerosis complex (n = 2, 7%). In eight patients where FCD was the most likely etiology, the histology was negative. Seven patients (23%) displayed normal magnetic resonance imaging results. Seizures exhibited diverse semiology and propagation patterns (frontal, perisylvian, and temporal). The ictal and interictal electroencephalographic (EEG) findings were mostly extensive. Multimodal imaging and advanced postprocessing were frequently used. Stereo-EEG was used for localizing the epileptogenic zone and eloquent cortex in 23 patients (77%). Oblique electrodes were used as guides for better neurosurgeon orientation. The epileptogenic zone was in the dominant hemisphere in 16 patients. At the 2-year follow-up, 22 patients (73%) were completely seizure-free, and eight (27%) experienced a seizure frequency reduction of >50% (International League Against Epilepsy class 3 and 4). Fourteen patients (47%) underwent antiseizure medication tapering; treatment was completely withdrawn in two (7%). Nineteen patients (63%) remained seizure-free following the definitive outcome assessment (median = 6 years 5 months, range = 2 years to 13 years 5 months postsurgery). Six patients (20%) experienced corona radiata or basal ganglia ischemia; four (13%) improved to mild and one (3%) to moderate hemiparesis. Two patients (7%) operated on in the anterior insula along with frontotemporal resection experienced major complications: pontine ischemia and postoperative brain edema.

SIGNIFICANCE

Epilepsy surgery in the operculoinsular cortex can lead to excellent patient outcomes. A comprehensive diagnostic approach is crucial for surgical success. Rehabilitation brings a great chance for significant recovery of postoperative deficits.

Ex-SPECTing success: Predictors of successful SPECT radiotracer injection during presurgical video-EEG admissions

OBJECTIVES

To determine predictors of successful ictal single photon emission computed tomography (SPECT) injections during Epilepsy Monitoring Unit (EMU) admissions for patients undergoing presurgical evaluation for drug-resistant focal epilepsy.

METHODS

In this retrospective study, consecutive EMU admissions were analyzed at a single center between 2019 and 2021. All seizures that occurred during the admission were reviewed. "Injectable seizures" occurred during hours when the radiotracer was available. EMU-level data were analyzed to identify factors predictive of an EMU admission with a successful SPECT injection (successful admission). Seizure-level data were analyzed to identify factors predictive of an injectable seizure receiving a SPECT injection during the ictal phase (successful injection). A multivariate generalized linear model was used to identify predictive variables.

RESULTS

125 EMU admissions involving 103 patients (median 37 years, IQR 27.0-45.5) were analyzed. 38.8% of seizures that were eligible for SPECT (n = 134) were successfully injected; this represented 17.4% of all seizures (n = 298) that occurred during admission. Unsuccessful admissions were most commonly due to a lack of seizures during EMU-SPECT (19.3%) or no injectable seizures (62.3%). Successful EMU-SPECT was associated with baseline seizure frequency >1 per week (95% CI 2.1-3.0, P < 0.001) and focal PET hypometabolism (95% CI 2.0-3.7, P < 0.001). On multivariate analysis, the only factor associated with successful injection was patients being able to indicate they were having a seizure to staff (95% CI 1.0-4.4, P = 0.038).

SIGNIFICANCE

Completing a successful ictal SPECT study remains challenging. A baseline seizure frequency of >1 per week, a PET hypometabolic focus, and a patient's ability to indicate seizure onset were identified as predictors of success. These findings may assist EMUs in optimizing their SPECT protocols, patient selection, and resource allocation.

Determinants of successful ictal SPECT injection in phase 1 epilepsy presurgical evaluation: Findings from the pediatric epilepsy research consortium surgery database project

OBJECTIVES

The main goal of presurgical evaluation in drug-resistant focal epilepsy is to identify a seizure onset zone (SOZ). Of the noninvasive, yet resource-intensive tests available, ictal single-photon emission computed tomography (SPECT) aids SOZ localization by measuring focal increases in blood flow within the SOZ via intravenous peri-ictal radionuclide administration. Recent studies indicate that geographic and center-specific factors impact utilization of these diagnostic procedures. Our study analyzed successful ictal SPECT acquisition (defined as peri-ictal injection during inpatient admission) using surgery-related data from the Pediatric Epilepsy Research Consortium (PERC) surgery database. We hypothesized that a high seizure burden, longer duration of video EEG monitoring (VEEG), and more center-specific hours of SPECT availability would increase the likelihood of successful ictal SPECT.

METHODS

We identified study participants (≤18 years of age) who underwent SPECT as part of their phase 1 VEEG from January 2018 to June 2022. We assessed association between ictal SPECT outcomes (success vs. failure) and variables including patient demographics, epilepsy history, and center-specific SPECT practices.

RESULTS

Phase 1 VEEG monitoring with ictal SPECT injection was planned in 297 participants and successful in 255 participants (85.86%). On multivariable analysis, the likelihood of a successful SPECT injection was higher in patients of non-Hispanic ethnicity (p = 0.040), shorter duration VEEG (p = 0.004), and higher hours of available SPECT services (p < 0.001). Higher seizure frequency (p = 0.033) was significant only in bivariate analysis. Patients treated at centers with more operational hours were more likely to experience pre-admission protocols prior to VEEG (p = 0.002).

SIGNIFICANCE

There is inter-center variability in protocols and SPECT acquisition capabilities. Shorter duration of EEG monitoring, non-Hispanic ethnicity (when on private insurance), extended operational hours of nuclear medicine as noted on multivariate analysis and higher seizure frequency in bivariate analysis are strongly associated with successful ictal SPECT injection.

PLAIN LANGUAGE SUMMARY

In pediatric patients with drug-resistant epilepsy, single-photon emission computed tomography (SPECT) scans can be helpful in localizing seizure onset zone. However, due to many logistical challenges described below, which include not only the half-life of the technetium isotope used to inject intravenously during a seizure (called the ictal SPECT scan) but also available nuclear scanner time in addition to the unpredictability of seizures, obtaining an ictal SPECT during a planned elective inpatient hospital stay is not guaranteed. Thus, as healthcare costs increase, planning a prolonged hospital stay during which an ictal SPECT scan is not feasible is not optimal. We leveraged our prospective surgery database to look at center-specific factors and patient-specific factors associated with an ictal SPECT injection in the first, pediatric-focussed, large-scale, multicenter, prospective, SPECT feasibility study. We found that longer availability of the scanner is the most important center-specific factor in assuring ictal SPECT injection. Although seizure frequency is an important patient-specific factor on bivariate analysis, this factor lost statistical significance when other factors like patient insurance status and video EEG duration were also considered in our multivariable logistical model.

Mesoscopic mapping of hemodynamic responses and neuronal activity during pharmacologically induced interictal spikes in awake and anesthetized mice

Imaging hemodynamic responses to interictal spikes holds promise for presurgical epilepsy evaluations. Understanding the hemodynamic response function is crucial for accurate interpretation. Prior interictal neurovascular coupling data primarily come from anesthetized animals, impacting reliability. We simultaneously monitored calcium fluctuations in excitatory neurons, hemodynamics, and local field potentials (LFP) during bicuculline-induced interictal events in both isoflurane-anesthetized and awake mice. Isoflurane significantly affected LFP amplitude but had little impact on the amplitude and area of the calcium signal. Anesthesia also dramatically blunted the amplitude and latency of the hemodynamic response, although not its area of spread. Cerebral blood volume change provided the best spatial estimation of excitatory neuronal activity in both states. Targeted silencing of the thalamus in awake mice failed to recapitulate the impact of anesthesia on hemodynamic responses suggesting that isoflurane's interruption of the thalamocortical loop did not contribute either to the dissociation between the LFP and the calcium signal nor to the alterations in interictal neurovascular coupling. The blood volume increase associated with interictal spikes represents a promising mapping signal in both the awake and anesthetized states.

EANM practice guidelines for an appropriate use of PET and SPECT for patients with epilepsy

Epilepsy is one of the most frequent neurological conditions with an estimated prevalence of more than 50 million people worldwide and an annual incidence of two million. Although pharmacotherapy with anti-seizure medication (ASM) is the treatment of choice, ~30% of patients with epilepsy do not respond to ASM and become drug resistant. Focal epilepsy is the most frequent form of epilepsy. In patients with drug-resistant focal epilepsy, epilepsy surgery is a treatment option depending on the localisation of the seizure focus for seizure relief or seizure freedom with consecutive improvement in quality of life. Beside examinations such as scalp video/electroencephalography (EEG) telemetry, structural, and functional magnetic resonance imaging (MRI), which are primary standard tools for the diagnostic work-up and therapy management of epilepsy patients, molecular neuroimaging using different radiopharmaceuticals with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) influences and impacts on therapy decisions. To date, there are no literature-based praxis recommendations for the use of Nuclear Medicine (NM) imaging procedures in epilepsy. The aims of these guidelines are to assist in understanding the role and challenges of radiotracer imaging for epilepsy; to provide practical information for performing different molecular imaging procedures for epilepsy; and to provide an algorithm for selecting the most appropriate imaging procedures in specific clinical situations based on current literature. These guidelines are written and authorized by the European Association of Nuclear Medicine (EANM) to promote optimal epilepsy imaging, especially in the presurgical setting in children, adolescents, and adults with focal epilepsy. They will assist NM healthcare professionals and also specialists such as Neurologists, Neurophysiologists, Neurosurgeons, Psychiatrists, Psychologists, and others involved in epilepsy management in the detection and interpretation of epileptic seizure onset zone (SOZ) for further treatment decision. The information provided should be applied according to local laws and regulations as well as the availability of various radiopharmaceuticals and imaging modalities.

Measurable transitions during seizures in intracranial EEG: A stereoelectroencephalography and SPECT study

OBJECTIVE

Ictal Single Photon Emission Computed Tomography (SPECT) and stereo-electroencephalography (SEEG) are diagnostic techniques used for the management of patients with drug-resistant focal epilepsies. While hyperperfusion patterns in ictal SPECT studies reveal seizure onset and propagation pathways, the role of ictal hypoperfusion remains poorly understood. The goal of this study was to systematically characterize the spatio-temporal information flow dynamics between differently perfused brain regions using stereo-EEG recordings.

METHODS

We identified seizure-free patients after resective epilepsy surgery who had prior ictal SPECT and SEEG investigations. We estimated directional connectivity between the epileptogenic-zone (EZ), non-resected areas of hyperperfusion, hypoperfusion, and baseline perfusion during the interictal, preictal, ictal, and postictal periods.

RESULTS

Compared to the background, we noted significant information flow (1) during the preictal period from the EZ to the baseline and hyperperfused regions, (2) during the ictal onset from the EZ to all three regions, and (3) during the period of seizure evolution from the area of hypoperfusion to all three regions.

CONCLUSIONS

Hypoperfused brain regions were found to indirectly interact with the EZ during the ictal period.

SIGNIFICANCE

Our unique study, combining intracranial electrophysiology and perfusion imaging, presents compelling evidence of dynamic changes in directional connectivity between brain regions during the transition from interictal to ictal states.

Short post-injection seizure duration is associated with reduced power of ictal brain perfusion SPECT to lateralize the seizure onset zone

BACKGROUND

The aim of this study was to assess the impact of the post-injection electrical seizure duration on the identification of the seizure onset zone (SOZ) in ictal brain perfusion SPECT in presurgical evaluation of drug-resistant epilepsy.

METHODS

176 ictal SPECT performed with 99mTc-HMPAO (n = 140) or -ECD (n = 36) were included retrospectively. Visual interpretation of the SPECT images (together with individual MRI and statistical hyperperfusion maps) with respect to lateralization (right, left, none) and localization (temporal, frontal, parietal, occipital) of the SOZ was performed by 3 independent readers. Between-readers agreement was characterized by Fleiss' κ. An ictal SPECT was considered "lateralizing" if all readers agreed on right or left hemisphere. It was considered "localizing" if it was lateralizing and all readers agreed on the same lobe within the same hemisphere. The impact of injection latency and post-injection seizure duration on the proportion of lateralizing/localizing SPECT was tested by ANOVA with dichotomized (by the median) injection latency and post-injection seizure duration as between-subjects factors.

RESULTS

Median [interquartile range] (full range) of injection latency and post-injection seizure duration were 30 [24, 40] (3-120) s and 50 [27, 70] (-20-660) s, respectively. Fleiss' κ for lateralization of the SOZ was largest for the combination of early (< 30 s) injection and long (> 50 s) post-injection seizure duration (κ = 0.894, all other combinations κ = 0.659-0.734). Regarding Fleiss' κ for localization of the SOZ in the 141 (80.1%) lateralizing SPECT, it was largest for early injection and short post-injection seizure duration (κ = 0.575, all other combinations κ = 0.329-0.368). The proportion of lateralizing SPECT was lower with short compared to long post-injection seizure duration (estimated marginal means 74.3% versus 86.3%, p = 0.047). The effect was mainly driven by cases with very short post-injection seizure duration ≤ 10 s (53.8% lateralizing). Injection latency in the considered range had no significant impact on the proportion of lateralizing SPECT (p = 0.390). The proportion of localizing SPECT among the lateralizing cases did not depend on injection latency or post-injection seizure duration (p ≥ 0.603).

CONCLUSIONS

Short post-injection seizure duration is associated with a lower proportion of lateralizing cases in ictal brain perfusion SPECT.

Triggered Seizures for Ictal SPECT Imaging: A Case Series and Feasibility Study

Ictal SPECT is an informative seizure imaging technique to tailor epilepsy surgery. However, capturing the onset of unpredictable seizures is a medical and logistic challenge. Here, we sought to image planned seizures triggered by direct stimulation of epileptic networks via stereotactic electroencephalography (sEEG) electrodes. Methods: In this case series of 3 adult participants with left temporal epilepsy, we identified and stimulated sEEG contacts able to trigger patient-typical seizures. We administered 99mTc-HMPAO within 12 s of ictal onset and acquired SPECT images within 40 min without any adverse events. Results: Ictal hyperperfusion maps partially overlapped concomitant sEEG seizure activity. In both participants known for periictal aphasia, SPECT imaging revealed hyperperfusion in the speech cortex lacking sEEG coverage. Conclusion: Triggering of seizures for ictal SPECT complements discrete sEEG sampling with spatially complete images of early seizure propagation. This readily implementable method revives interest in seizure imaging to guide resective epilepsy surgery.

Effective connectivity relates seizure outcome to electrode placement in responsive neurostimulation

Responsive neurostimulation is a closed-loop neuromodulation therapy for drug resistant focal epilepsy. Responsive neurostimulation electrodes are placed near ictal onset zones so as to enable detection of epileptiform activity and deliver electrical stimulation. There is no standard approach for determining the optimal placement of responsive neurostimulation electrodes. Clinicians make this determination based on presurgical tests, such as MRI, EEG, magnetoencephalography, ictal single-photon emission computed tomography and intracranial EEG. Currently functional connectivity measures are not being used in determining the placement of responsive neurostimulation electrodes. Cortico-cortical evoked potentials are a measure of effective functional connectivity. Cortico-cortical evoked potentials are generated by direct single-pulse electrical stimulation and can be used to investigate cortico-cortical connections in vivo. We hypothesized that the presence of high amplitude cortico-cortical evoked potentials, recorded during intracranial EEG monitoring, near the eventual responsive neurostimulation contact sites is predictive of better outcomes from its therapy. We retrospectively reviewed 12 patients in whom cortico-cortical evoked potentials were obtained during stereoelectroencephalography evaluation and subsequently underwent responsive neurostimulation therapy. We studied the relationship between cortico-cortical evoked potentials, the eventual responsive neurostimulation electrode locations and seizure reduction. Directional connectivity indicated by cortico-cortical evoked potentials can categorize stereoelectroencephalography electrodes as either receiver nodes/in-degree (an area of greater inward connectivity) or projection nodes/out-degree (greater outward connectivity). The follow-up period for seizure reduction ranged from 1.3-4.8 years (median 2.7) after responsive neurostimulation therapy started. Stereoelectroencephalography electrodes closest to the eventual responsive neurostimulation contact site tended to show larger in-degree cortico-cortical evoked potentials, especially for the early latency cortico-cortical evoked potentials period (10-60 ms period) in six out of 12 patients. Stereoelectroencephalography electrodes closest to the responsive neurostimulation contacts (≤5 mm) also had greater significant out-degree in the early cortico-cortical evoked potentials latency period than those further away (≥10 mm) (P < 0.05). Additionally, significant correlation was noted between in-degree cortico-cortical evoked potentials and greater seizure reduction with responsive neurostimulation therapy at its most effective period (P < 0.05). These findings suggest that functional connectivity determined by cortico-cortical evoked potentials may provide additional information that could help guide the optimal placement of responsive neurostimulation electrodes.

Identifying and troubleshooting the pitfalls of ictal/interictal brain perfusion SPECT studies

Epilepsy is a prevalent condition, and surgical intervention can benefit patients with refractory seizures. Single photon emission computed tomography (SPECT) using 99mTc-HMPAO or 99mTc-ECD provides assessment of regional cerebral blood flow and is the primary non-invasive approach for imaging brain perfusion in ictal and interictal states. Ictal/interictal SPECT is valuable in localising epileptogenic foci, particularly when MRI and electroencephalography are negative. However, to obtain accurate images reflecting brain perfusion in both states, meticulous preparation of the patient, timely radiotracer injection and close coordination between neurology and nuclear medicine teams are essential. Tracers also have inherent limitations, and patients may present with coexisting brain pathologies for which coregistration of SPECT images with MRI is recommended to improve diagnostic accuracy. Inconclusive SPECT findings may require repeating the exam or considering additional investigations. A comprehensive approach, considering various factors, is crucial for accurate interpretation of SPECT studies in presurgical epilepsy evaluations. This article provides a summary of the organisation and key challenges involved in conducting ictal/interictal SPECT studies, covering the entire process from a patient's hospital arrival to the integration of results within their presurgical pathway and using our experience of 182 patients over 10 years.

Regional cerebral blood flow in a patient with asystole episodes associated with anti-NMDA receptor encephalitis

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is a rare and severe autoimmune encephalitis that displays neuropsychiatric symptoms and autonomic instability, e.g., hypoventilation and cardiac arrhythmia. Severe arrhythmia including asystole associated with this encephalitis is rare. Several causes have been suggested. Nevertheless, no report of the literature has described examination by functional brain imaging of a patient with asystole during anti-NMDA receptor encephalitis. This case is that of a 34-year-old woman diagnosed as having anti-NMDA receptor encephalitis. She repeatedly showed 10-20 s asystole episodes necessitating a temporary transvenous pacemaker. After resection of the bilateral ovarian cystic tumor, her symptoms improved. Regional cerebral blood flow (rCBF) was evaluated using single-photon emission computed tomography. The rCBF was increased in the amygdala, hypothalamus, anterior cingulate, hippocampus, and anterior temporal lobes, but decreased in the dorsolateral frontal lobes, parietal lobes, and occipital lobes. Findings in this case suggest that altered rCBF in the patient with asystole episodes associated with anti-NMDA receptor encephalitis was observed in several brain lesions. The rCBF increases in the central autonomic networks, i.e., the amygdala, hypothalamus, and anterior cingulate, might be associated with dysregulation of sympathetic and parasympathetic nervous systems leading to asystole.

Novel noninvasive identification of patient-specific epileptic networks in focal epilepsies: Linking single-photon emission computed tomography perfusion during seizures with resting-state magnetoencephalography dynamics

Single-photon emission computed tomography (SPECT) during seizures and magnetoencephalography (MEG) during the interictal state are noninvasive modalities employed in the localization of the epileptogenic zone in patients with drug-resistant focal epilepsy (DRFE). The present study aims to investigate whether there exists a preferentially high MEG functional connectivity (FC) among those regions of the brain that exhibit hyperperfusion or hypoperfusion during seizures. We studied MEG and SPECT data in 30 consecutive DRFE patients who had resective epilepsy surgery. We parcellated each ictal perfusion map into 200 regions of interest (ROIs) and generated ROI time series using source modeling of MEG data. FC between ROIs was quantified using coherence and phase-locking value. We defined a generalized linear model to relate the connectivity of each ROI, ictal perfusion z score, and distance between ROIs. We compared the coefficients relating perfusion z score to FC of each ROI and estimated the connectivity within and between resected and unresected ROIs. We found that perfusion z scores were strongly correlated with the FC of hyper-, and separately, hypoperfused ROIs across patients. High interictal connectivity was observed between hyperperfused brain regions inside and outside the resected area. High connectivity was also observed between regions of ictal hypoperfusion. Importantly, the ictally hypoperfused regions had a low interictal connectivity to regions that became hyperperfused during seizures. We conclude that brain regions exhibiting hyperperfusion during seizures highlight a preferentially connected interictal network, whereas regions of ictal hypoperfusion highlight a separate, discrete and interconnected, interictal network.

Neurological update: structural and functional imaging in epilepsy surgery

Structural and functional imaging prior to surgery in drug-resistant focal epilepsy, has an important role to play alongside electroencephalography (EEG) techniques, in planning the surgical approach and predicting post-operative outcome. This paper reviews the role of structural and functional imaging of the brain, namely computed tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging in the preoperative work-up of people with medically refractory epilepsy. In MRI-negative patients, the precise localisation of the epileptogenic zone may be established by demonstrating hypometabolism on PET imaging or hyperperfusion on SPECT imaging in the area surrounding the seizure focus. These imaging modalities are far less invasive than intracranial EEG, which is the gold standard but requires surgical placement of electrodes or recording grids. Even when intracranial EEG is needed, PET or SPECT imaging can assist in the planning of EEG electrode placement, due to its' limited spatial sampling. Multimodal imaging techniques now allow the multidisciplinary epilepsy surgery team to identify and better characterise focal pathology, determine its' relationship to eloquent areas of the brain and the degree of interconnectedness within both physiological and pathological networks, as well as improve planning and surgical outcomes for patients. This paper will update the reader on this whole field and provide them with a practical guide, to aid them in the selection of appropriate investigations, interpretation of the findings and facilitating patient discussions in individuals with drug-resistant focal epilepsy.

Tailoring Materials for Epilepsy Imaging: From Biomarkers to Imaging Probes

Excising epileptic foci (EF) is the most efficient approach for treating drug-resistant epilepsy (DRE). However, owing to the vast heterogeneity of epilepsies, EF in one-third of patients cannot be accurately located, even after exhausting all current diagnostic strategies. Therefore, identifying biomarkers that truly represent the status of epilepsy and fabricating probes with high targeting specificity are prerequisites for identifying the "concealed" EF. However, no systematic summary of this topic has been published. Herein, the potential biomarkers of EF are first summarized and classified into three categories: functional, molecular, and structural aberrances during epileptogenesis, a procedure of nonepileptic brain biasing toward epileptic tissue. The materials used to fabricate these imaging probes and their performance in defining the EF in preclinical and clinical studies are highlighted. Finally, perspectives for developing the next generation of probes and their challenges in clinical translation are discussed. In general, this review can be helpful in guiding the development of imaging probes defining EF with improved accuracy and holds promise for increasing the number of DRE patients who are eligible for surgical intervention.

Lateralized Periodic Discharges in a Patient With Dural Arteriovenous Fistula: SPECT and DWI Studies Suggest They are Ictal

Lateralized periodic discharges (LPDs) are unilateral electroencephalography (EEG) waveforms, recurring at regular intervals. There has been a long-lasting debate about whether they represent ictal or interictal phenomena. Very few patients in the literature have been investigated with multimodal functional imaging techniques. Here, we present a 58-year-old male patient with symptomatic epilepsy who had cerebral venous sinus thrombosis in the right temporo-parietal area and dural arteriovenous fistula (dAVF) over the left fronto-parietal region. He developed acute speech disturbances and altered mental status after a generalized tonic-clonic seizure. Video-EEG monitoring (VEEGM) demonstrated LPDs over the left fronto-central area, overlapping in part with the dAVF. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) sequences revealed restricted diffusion compatible with cytotoxic edema, whereas single-photon emission computed tomography (SPECT) indicated hyperperfusion in the same region, leading to the conclusion that he was having possible nonconvulsive status epilepticus (NCSE). An increase in antiseizure medications led to gradual improvement in clinical status and the disappearance of LPDs.

Epileptic seizures in the emergency room: clinical and electroencephalographic findings associated with brain perfusion patterns on computed tomography

Background

Diagnosis of epileptic seizures, particularly regarding status epilepticus (SE), may be challenging in an emergency room setting. The aim of the study was to study the diagnostic yield of perfusion computed tomography (pCT) in patients with single epileptic seizures and SE.

Methods

We retrospectively reviewed the records of patients who followed an acute ischemic stroke pathway during a 9-month period and who were finally diagnosed with a single epileptic seizure or SE. Perfusion maps were visually analyzed for the presence of hyperperfusion and hypoperfusion. Clinical data, EEG patterns, and neuroimaging findings were compared.

Results

We included 47 patients: 20 (42.5%) with SE and 27 (57.5%) with single epileptic seizure. Of 18 patients who showed hyperperfusion on pCT, 12 were ultimately diagnosed with SE and eight had EEG findings compatible with an SE pattern. Focal hyperperfusion on pCT had a sensitivity of 60% (95% CI 36.4–80.2) and a specificity of 77.8% (95% CI 57.2–90.6) for predicting a final diagnosis of SE. The presence of cerebral cortical and thalamic hyperperfusion had a high specificity for predicting SE presence. Of note, 96% of patients without hyperperfusion on pCT did not show an SE pattern on early EEG.

Conclusions

In acute settings, detection by visual analysis of focal cerebral cortical hyperperfusion on pCT in patients with epileptic seizures, especially if accompanied by the highly specific feature of thalamic hyperperfusion, is suggestive of a diagnosis of SE and requires clinical and EEG confirmation. The absence of focal hyperperfusion makes a diagnosis of SE unlikely.

Impact of reconstruction parameters on lesion detection and localization in joint ictal/inter-ictal SPECT reconstruction

PURPOSE

Previously, a joint ictal/inter-ictal SPECT reconstruction was proposed to reconstruct a differential image representing the change of brain SPECT image from an inter-ictal to an ictal study. The so-called joint method yielded better performance for epileptic foci localization than the conventional subtraction method. In this study, we evaluated the performance of different reconstruction settings of the joint reconstruction of ictal/inter-ictal SPECT data, which creates a differential image showing the difference between ictal and inter-ictal images, in lesion detection and localization in epilepsy imaging.

METHODS

Differential images reconstructed from phantom data using the joint and the subtraction methods were compared based on lesion detection performance (channelized Hotelling observer signal-to-noise ratio (SNRCHO) averaged across four lesion-to-background contrast levels) at the optimal iteration. The joint-initial method which was the joint method that was initialized by the subtraction method at optimal iteration was also used to reconstruct differential images. These three methods with respective optimal iteration and the subtraction method with four iterations were applied to epileptic patient datasets. A human observer lesion localization study was performed based on localization receiver operating characteristic (LROC) analysis.

RESULTS

From the phantom study, at their respective optimal iteration, the joint method yielded an improvement in lesion detection performance over the subtraction method of 26%, which increased to 145% when using the joint-initial method. From the patient study, the joint-initial method yielded the highest area under the LROC curve as compared with those of the joint and the subtraction methods with optimal iteration and with 4 iterations (0.44 vs 0.41, 0.39 and 0.36, respectively).

CONCLUSIONS

In lesion detection and localization, the joint method at optimal iteration outperformed the subtraction method at optimal iteration and at iteration typically used in clinical practice. Furthermore, initialization by the subtraction method improved the performance of the joint method.

Identification of Negative BOLD Responses in Epilepsy Using Windkessel Models

Alongside positive blood oxygenation level–dependent (BOLD) responses associated with interictal epileptic discharges, a variety of negative BOLD responses (NBRs) are typically found in epileptic patients. Previous studies suggest that, in general, up to four mechanisms might underlie the genesis of NBRs in the brain: (i) neuronal disruption of network activity, (ii) altered balance of neurometabolic/vascular couplings, (iii) arterial blood stealing, and (iv) enhanced cortical inhibition. Detecting and classifying these mechanisms from BOLD signals are pivotal for the improvement of the specificity of the electroencephalography–functional magnetic resonance imaging (EEG-fMRI) image modality to identify the seizure-onset zones in refractory local epilepsy. This requires models with physiological interpretation that furnish the understanding of how these mechanisms are fingerprinted by their BOLD responses. Here, we used a Windkessel model with viscoelastic compliance/inductance in combination with dynamic models of both neuronal population activity and tissue/blood O₂ to classify the hemodynamic response functions (HRFs) linked to the above mechanisms in the irritative zones of epileptic patients. First, we evaluated the most relevant imprints on the BOLD response caused by variations of key model parameters. Second, we demonstrated that a general linear model is enough to accurately represent the four different types of NBRs. Third, we tested the ability of a machine learning classifier, built from a simulated ensemble of HRFs, to predict the mechanism underlying the BOLD signal from irritative zones. Cross-validation indicates that these four mechanisms can be classified from realistic fMRI BOLD signals. To demonstrate proof of concept, we applied our methodology to EEG-fMRI data from five epileptic patients undergoing neurosurgery, suggesting the presence of some of these mechanisms. We concluded that a proper identification and interpretation of NBR mechanisms in epilepsy can be performed by combining general linear models and biophysically inspired models.

Automated Brain Perfusion Imaging in Acute Ischemic Stroke: Interpretation Pearls and Pitfalls

Recent advancements in computed tomography technology, including improved brain coverage and automated processing of the perfusion data, have reinforced the use of perfusion computed tomography imaging in the routine evaluation of patients with acute ischemic stroke. The DAWN (Diffusion Weighted Imaging or Computerized Tomography Perfusion Assessment With Clinical Mismatch in the Triage of Wake Up and Late Presenting Strokes Undergoing Neurointervention) and DEFUSE 3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3) trials have established the benefit of endovascular thrombectomy in patients with acute ischemic stroke with anterior circulation large vessel occlusion up to 24 hours of last seen normal, using perfusion imaging-based patient selection. The compelling data has prompted stroke centers to increasingly introduce automated perfusion computed tomography imaging in the routine evaluation of patients with acute ischemic stroke. We present a comprehensive overview of the acquisition and interpretation of automated perfusion imaging in patients with acute ischemic stroke with a special emphasis on the interpretation pearls, pitfalls, and stroke mimicking conditions.

Mesoscopic Mapping of Ictal Neurovascular Coupling in Awake Behaving Mice Using Optical Spectroscopy and Genetically Encoded Calcium Indicators

Unambiguously identifying an epileptic focus with high spatial resolution is a challenge, especially when no anatomic abnormality can be detected. Neurovascular coupling (NVC)-based brain mapping techniques are often applied in the clinic despite a poor understanding of ictal NVC mechanisms, derived primarily from recordings in anesthetized animals with limited spatial sampling of the ictal core. In this study, we used simultaneous wide-field mesoscopic imaging of GCamp6f and intrinsic optical signals (IOS) to record the neuronal and hemodynamic changes during acute ictal events in awake, behaving mice. Similar signals in isoflurane-anesthetized mice were compared to highlight the unique characteristics of the awake condition. In awake animals, seizures were more focal at the onset but more likely to propagate to the contralateral hemisphere. The HbT signal, derived from an increase in cerebral blood volume (CBV), was more intense in awake mice. As a result, the “epileptic dip” in hemoglobin oxygenation became inconsistent and unreliable as a mapping signal. Our data indicate that CBV-based imaging techniques should be more accurate than blood oxygen level dependent (BOLD)-based imaging techniques for seizure mapping in awake behaving animals.

Use of Innovative SPECT Techniques in the Presurgical Evaluation of Patients with Nonlesional Extratemporal Drug-Resistant Epilepsy

Up to 30% of patients with epilepsy may not respond to antiepileptic drugs. Patients with drug-resistant epilepsy (DRE) should undergo evaluation for seizure onset zone (SOZ) localization to consider surgical treatment. Cases of drug-resistant nonlesional extratemporal lobe epilepsy (ETLE) pose the biggest challenge in localizing the SOZ and require multiple noninvasive diagnostic investigations before planning the intracranial monitoring (ICM) or direct resection. Ictal Single Photon Emission Computed Tomography (i-SPECT) is a unique functional diagnostic tool that assesses the SOZ using the localized hyperperfusion that occurs early in the seizure. Subtraction ictal SPECT coregistered to MRI (SISCOM), statistical ictal SPECT coregistered to MRI (STATISCOM), and PET interictal subtracted ictal SPECT coregistered with MRI (PISCOM) are innovative SPECT methods for the determination of the SOZ. This article comprehensively reviews SPECT and sheds light on its vital role in the presurgical evaluation of the nonlesional extratemporal DRE.

Impact of ictal subtraction SPECT and PET in presurgical evaluation

OBJECTIVE

To assess the relative contribution of ictal subtraction single-photon emission computed tomography (ISSPECT) and ¹⁸ F-fluorodeoxyglucose positron emission tomography computed tomography (PET) in epilepsy surgery decision making.

MATERIALS AND METHODS

A retrospective 3-year study of consecutive patients with resistant focal epilepsy who underwent ISSPECT and PET to evaluate to what extent these modalities influence decisions in epilepsy surgery and outcomes. ISSPECT imaging was performed in 106 patients and 58 (55%) had PET also. The clinical consensus (ClinC) was the final arbiter for decisions. Post-surgical outcomes were collected from follow-up clinics. Non-parametric statistics were used to assess association and logistic regression to evaluate prediction of outcomes.

RESULTS

Of 106 patients, 60 were males (57%). MRI was non-lesional in 46 (43%). Concordance with ClinC was seen in 80 patients (76%) for ISSPECT, in 46 patients (79%) for PET, and in 37 patients (64%) for ISSPECT + PET. Fifty-six patients (53%) were planned for intracranial video-electroencephalography monitoring (IVEM). Those with ClinC-PET concordance were likely to proceed to IVEM (p = 0.02). ClinC-PET concordance and ClinC-ISSPECT concordance did not predict decision to proceed to surgery, but VEM-MRI concordance did in lesional cases (p = 0.018). Forty-five (42%) underwent surgery of which 29 had minimum follow-up for 1 year (mean, 20 months; SD, 8) and 22 (76%) had Engel class I outcomes. ClinC-ISSPECT concordance (p = 0.024) and VEM-MRI concordance (p = 0.016) predicted Engel class I outcomes.

CONCLUSION

Those with ClinC-PET concordance were more likely to proceed with IVEM. ClinC-ISSPECT concordance and VEM-MRI concordance predicted good surgical outcomes.

Neurovascular networks in epilepsy: Correlating ictal blood perfusion with intracranial electrophysiology

Perfusion patterns observed in Subtraction Ictal SPECT Co-registered to MRI (SISCOM) assist in focus localization and surgical planning for patients with medically intractable focal epilepsy. While the localizing value of SISCOM has been widely investigated, its relationship to the underlying electrophysiology has not been extensively studied and is therefore not well understood. In the present study, we set to investigate this relationship in a cohort of 70 consecutive patients who underwent ictal and interictal SPECT studies and subsequent stereo-electroencephalography (SEEG) monitoring for localization of the epileptogenic focus and surgical intervention. Seizures recorded during SEEG evaluation (SEEG seizures) were matched to semiologically-similar seizures during the preoperative ictal SPECT evaluation (SPECT seizures) by comparing the semiological changes in the course of each seizure. The spectral changes of the ictal SEEG with respect to interictal ones over 7 traditional frequency bands (0.1 to 150Hz) were analyzed at each SEEG site. Neurovascular (SEEG/SPECT) relations were assessed by comparing the estimated spectral power density changes of the SEEG at each site with the perfusion changes (SISCOM z-scores) estimated from the acquired SISCOM map at that site. Across patients, a significant correlation (p<0.05) was observed between spectral changes during the SEEG seizure and SISCOM perfusion z-scores. Brain sites with high perfusion z-score exhibited higher increased SEEG power in theta to ripple frequency bands with concurrent suppression in delta and theta frequency bands compared to regions with lower perfusion z-score. The dynamics of the correlation of SISCOM perfusion and SEEG spectral power from ictal onset to seizure end and immediate postictal period were also derived. Forty-six (46) of the 70 patients underwent resective epilepsy surgery. SISCOM z-score and power increase in beta to ripple frequency bands were significantly higher in resected than non-resected sites in the patients who were seizure-free following surgery. This study provides for the first time concrete evidence that both hyper-perfusion and hypo-perfusion patterns observed in SISCOM maps have strong electrophysiological underpinnings, and that integration of the information from SISCOM and SEEG can shed light on the location and dynamics of the underlying epileptic brain networks, and thus advance our anatomo-electro-clinical understanding and approaches to targeted diagnostic and therapeutic interventions.

Effect of automatic injectors on the injection latency, safety, and seizure onset zone localization of ictal single photon emission computed tomography studies in adult epilepsy monitoring unit

BACKGROUND

Ictal Single Photon Emission Computed Tomography (iSPECT) is one of the established tools utilized in the presurgical evaluation of patients with drug-resistant epilepsy (DRE). Timely isotope injection for an iSPECT is critical for optimal yield but poses logistical challenges when done manually. We aim to evaluate the added value of automatic iSPECT injectors (ASIs) in overcoming such challenges.

METHODS

We retrospectively reviewed all cases admitted to the University of Pittsburgh Medical Center (UPMC) Epilepsy Monitoring Unit from Jan 1, 2010, through Dec 31, 2016, who underwent an iSPECT. We compared the manually injected iSPECTs with those performed with ASIs.

RESULTS

A total of 123 iSPECTs were reviewed. The manually injected iSPECT group consisted of 35 patients (median age, 35 years; and 19 males). The automatically injected iSPECT group consisted of 88 patients (median age, 36 years; and 46 males). The two groups were comparable in age, gender, epilepsy treatment, focal features on neuropsychological testing (NPT), EEG, and MRI, and temporal origin of seizures (p > 0.05). Compared to manually injected iSPECTs, automatically injected ISPECTs' median injection latency (IL) was shorter (18.5 vs. 60 s, p < 0.001); the ratio of IL/total duration of seizure was lower (0.395 vs. 0.677, p < 0.001); postictal injections were less frequent (4 (4.5 %) vs. 7 (20 %), p = 0.007); the number of isotope spills was less (zero vs. 3, p = 0.022); and successfully localizing iSPECTs were more prevalent (81.8 % vs. 62.9 %, p = 0.025), even after adjusting for focal features on NPT, EEG, and MRI, the temporal origin of seizures, and seizure duration (OR of 5.539, 95 %CI = 1.653-18.563, p = 0.006).

CONCLUSIONS

Utilization of ASIs leads to a significant shortening of iSPECT IL with less postictal injections, provides a safer injection option for the EMU staff, and leads to a significant improvement in the number of successfully localizing iSPECTs.

Epileptic seizures triggered by eating in dogs

Background

Seizures triggered by eating (STE) behavior are very rare in humans and have not been documented previously in dogs.

Objectives

To document the occurrence of STE in dogs and describe their clinical features.

Animals

Ten client‐owned dogs with STE diagnosed at 5 European referral centers.

Methods

A call for suspected cases of STE was made online. This call was followed by a retrospective review of medical records, combined with a questionnaire to be completed by both the owner and the board‐certified neurologist who made the diagnosis. Cases were included if >50% of the seizures that occurred were related to eating and if a minimum diagnostic evaluation for seizures had been performed.

Results

Four cases only had STE and 6 cases had both STE and spontaneous seizures. Four of the dogs were retrievers. The most common seizure type was focal epileptic seizures evolving to become generalized. Nine dogs were diagnosed with idiopathic epilepsy. One dog had a presumptive diagnosis of glioma involving the margins of the parietal, temporal, and frontal cortex (the perisylvian region), an area known to have a key role in eating‐associated epilepsy in people. Treatment strategies included a combination of pharmacological management and eating habit changes.

Conclusions and Clinical Importance

We have identified a form of reflex epilepsy in dogs, with STE behavior. Further studies are warranted to improve the characterization and management of STE.

Restrictive cerebral cortical venopathy: A new clinicopathological entity

We present a case of a novel restrictive cerebral venopathy in a child, consisting of a bilateral network of small to medium cortical veins without evidence of arteriovenous shunting, absence of the deep venous system, venous ischemia, elevated intracranial pressure, and intracranial calcifications. The condition is unlike other diseases characterized by networks of small veins, including cerebral proliferative angiopathy, Sturge-Weber syndrome, or developmental venous anomaly. While this case may be the result of an anatomic variation leading to the congenital absence of or early occlusion of the deep venous system, the insidious nature over many years argues against this. The absence of large cortical veins suggests a congenital abnormality of the venous structure. The child's presentation with a seizure-like event followed by protracted hemiparesis is consistent with venous ischemia. We propose that this is likely to represent a new clinicopathological entity.

A study of perfusion changes with Insula Epilepsy using SPECT

PURPOSE

The non-invasive localisation of insular lobe epilepsy is a challenge. We aimed to determine if ictal SPECT is a reliable adjunctive test in insular cases and to explore its role in the tailoring of intracranial strategies.

METHOD

From a dataset of patients who underwent SEEG between December 2012 and December 2016, we collected patients with focal insular onset epilepsy. We examined semiology, EEG, PET and SPECT hyperperfusion pattern with SISCOM. We also reviewed relevant literature.

RESULTS

5 patients were identified, 4 females, from a dataset of 51 patients. Median age of seizure onset was 8 years old (8 months to 10 years). All patients had an ictal SPECT during pre-surgical work-up: median injection time was 7 s (3-17 sec) from clinical onset, and median seizure duration was 42 s (11-85 sec). Insula cortex showed focal hyperaemia in four patients, all bilateral, with the greatest hyperperfusion contralateral to the ictal onset in two cases, using SISCOM threshold at 1.5 standard deviation. Other sites with hyperaemia included basal ganglia and middle temporal gyrus. The SEEG confirmed insular onset seizures in all the cases. All patients had epilepsy surgery and were seizure free at 21 to 50 months follow up. The results from the literature review showed frequent hyperperfusion in structures outside insula and frequently over the contralateral hemisphere.

CONCLUSIONS

This study highlights the technical limitations of SPECT when attempting to assess seizures arising from the insula. Our findings and the literature show ictal SPECT can be localising but falsely lateralising in seizures arising from the insula.

An acute stroke CT imaging algorithm incorporating automated perfusion analysis

In this paper, we propose a CT imaging algorithm for patients presenting with suspected acute stroke that incorporates automated CT perfusion (CTP) imaging. The algorithm details evaluation of the non-contrast CT (NCCT) for hemorrhage and acute ischemia, calculation of ASPECTS, with performance and interpretation of CTP if appropriate. In particular, we consider the key steps in expeditious interpretation of non-contrast CT and CT angiography in the context of suspected acute ischemic stroke. Given the recent expansion of the "imaging based" treatment window for thrombectomy from 6 to 24 h in the 2018 American Heart Association stroke guidelines, we consider the key criteria in the decision to perform CT perfusion and the patient cohorts in which this might be most helpful. We also describe how imaging findings might be incorporated into the treatment paradigm for suspected with acute ischemic stroke and we allude to some of the most frequently encountered pitfalls associated with CTP which we think will be particularly helpful for radiologists and stroke physicians who are considering adding CT perfusion to their work-up for acute stroke.

Seizure in code stroke: Stroke mimic and initial manifestation of stroke

BACKGROUND

Although seizure is one of the common causes of stroke mimics and can be an initial manifestation of acute stroke, accurate diagnosis of seizure during acute stroke management is frequently difficult. The objective of this study was to analyze the frequency, characteristics and results of neuroimaging including CT perfusion in patients with seizures manifesting initially as stroke-like symptoms.

METHODS

We retrospectively reviewed the medical records of patients who were treated with code stroke alarming system. We studied the frequency and characteristics of patients who were finally diagnosed with seizures and further correlated their clinical features with the results of neuroimaging including CT perfusion.

RESULTS

Among the 4673 patients who were treated with code stroke alarming system, seizure was the third most frequent diagnosis (188 patients, 4.0%) among the causes of stroke mimics including 27 patients who manifested seizure as an initial manifestation of acute stroke. CT perfusion showed perfusion changes in more than 25% of them (49 of 188 patients, 26.1%). Thrombolysis was not performed in six patients who presented with seizure as an initial presentation of stroke for delayed diagnosis while one patient underwent thrombolysis for misdiagnosis of seizure.

CONCLUSIONS

Seizure is a frequent final diagnosis in acute stroke management. However, careful interpretation of clinical features and results of perfusion imaging is necessary to avoid unnecessary thrombolysis in patients with seizure as a stroke mimic and thrombolysis failure due to delayed diagnosis of seizure as an initial manifestation of stroke.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

SIGNIFICANCE

Measures of preictal/early ictal network dynamics may help optimize the SPECT localization, leading to improved surgical and neurostimulation outcomes in refractory epilepsy.

Can perfusion CT unmask postictal stroke mimics?

Objective

To study the diagnostic value of volume perfusion CT (VPCT) in patients with transient focal neurologic deficits following and during epileptic seizures, that mimic symptoms of stroke.

Methods

A retrospective case-control study was performed on 159 patients who presented with a seizure and received an emergency VPCT within the first 3.5 hours of admission, after being misjudged to have an acute stroke. The reference test was a clinical-based, EEG-supported diagnostic algorithm for seizure.

Results

We included 133 patients: 94 stroke-mimicking cases with postictal focal neurologic deficits (“Todd phenomenon,” n = 67) or ongoing seizure on hospital admission (“ictal patients,” n = 27), and 39 postictal controls without focal neurologic deficits. Patients with Todd phenomenon showed normal perfusion (64%), hypoperfusion (21%), and hyperperfusion (14%) on early VPCT. Ictal patients displayed more hyperperfusion compared to postictal patients (p = 0.015). Test sensitivity of hyperperfusion for ictal patients is 38% (95% confidence interval [CI] 20.7%–57.7%), specificity 86% (95% CI 77.3%–91.7%), positive predictive value is 42% (95% CI 27.5%–58.7%), and the negative predictive value 83% (95% CI 78.6%–86.9%). A cortical distribution was seen in all hyperperfusion scans, compared to a cortico-subcortical pattern in hypoperfusion (p < 0.001). A history of complex focal seizure and age were associated with hyperperfusion (p = 0.046 and 0.038, respectively).

Conclusion

VPCT can differentiate ictal stroke mimics with hyperperfusion from acute ischemic stroke, but not postictal patients who display perfusion patterns overlapping with ischemic stroke.

Classification of evidence

This study provides Class IV evidence that VPCT accurately differentiates ictal stroke mimics from acute ischemic stroke.

Serum NT-pro CNP levels in epileptic seizure, psychogenic non-epileptic seizure, and healthy subjects

PURPOSE

Epileptic seizure is the result of uncontrollable neural excitation in the brain. The C-type natriuretic peptide is a member of natriuretic peptide hormone family and is synthesized by brain and blood vessels in CNS. NT-pro CNP is an amino-terminal fragment of C-type natriuretic peptide and is more stable compared to its predecessor. In this study, we aimed to evaluate the role of NT-pro CNP in psychogenic non-epileptic seizures, epileptic seizures, and normal subjects.

METHODS

Thirty-three patients with epilepsy and 43 patients with psychogenic non-epileptic seizures were enrolled in this study. The control group consisted of 28 healthy subjects. Post-ictal serum levels of NT-pro CNP were acquired from all participants. Statistically significant differences between patient groups and controls regarding serum levels of NT-pro CNP were sought.

RESULTS

NT-pro CNP levels were significantly lower in the epilepsy group than the psychogenic non-epileptic seizure group and control group with no significant difference between the psychogenic non-epileptic seizure and control group (p < 0.05).

CONCLUSION

Post-ictal serum NT-pro CNP levels were lower in epileptic seizures compared to psychogenic non-epileptic seizures as well as healthy controls. We think that such a difference is associated with C-type natriuretic peptide-related neural mechanisms such as altered microcirculation, increased brain-blood barrier permeability, and synaptic stabilization.

Role of contrast-free MR-perfusion in the diagnosis of potential epileptogenic foci in children with focal epilepsia

ASL (Arterial Spin Labeling) – a novel modality of MR angiography – is based on radio-frequency labeling of aqueous protons in the arterial blood; the method is used to monitor blood supply to  organs, including the brain. So far there has been little information on the use of ASL in children with focal epilepsy, especially in the pre-surgery period.

Aim:to evaluate the perfusion patterns in seizure-free children with drug resistant focal epilepsy (FE) using the ASL mode of MRI.

Materials and methods.We studied the ASL data of 54 (23-boys/31 girls) patients with FE  treated in the Dpt. of Neurology at the Russian State Children Hospital from 2015 to 2018. The  patients’ age varied from 4 months to 17 years. All images were produced with a 3T GE Discovery  750W system.

Results. We found several brain perfusion patterns in children with FE; among other factors, those patterns depended on the clinical status of the patient, i. e. the interictal period or the early post- seizure period. The main pattern of the interictal period was characterized by a focal decrease in  perfusion located around a structural focus identified on MRI scans. In the early post-seizure  period, there was an increase in the arterial perfusion in the area of a structural epileptogenic lesion.

Conclusion.ASL-MRI is an effective diagnostic method providing more information on children  with FE during their pre-surgery phase. The ASL modality needs further research to rationalize its wider use as a preferred diagnostic tool or as a combination with the more complex PET and SPECT.

On the optimal z-score threshold for SISCOM analysis to localize the ictal onset zone

Background

In epilepsy patients, SISCOM or subtraction ictal single photon emission computed tomography co-registered to magnetic resonance imaging has become a routinely used, non-invasive technique to localize the ictal onset zone (IOZ). Thresholding of clusters with a predefined number of standard deviations from normality (z-score) is generally accepted to localize the IOZ. In this study, we aimed to assess the robustness of this parameter in a group of patients with well-characterized drug-resistant epilepsy in whom the exact location of the IOZ was known after successful epilepsy surgery. Eighty patients underwent preoperative SISCOM and were seizure free in a postoperative period of minimum 1 year. SISCOMs with z-threshold 2 and 1.5 were analyzed by two experienced readers separately, blinded from the clinical ground truth data. Their reported location of the IOZ was compared with the operative resection zone. Furthermore, confidence scores of the SISCOM IOZ were compared for the two thresholds.

Results

Visual reporting with a z-score threshold of 1.5 and 2 showed no statistically significant difference in localizing correspondence with the ground truth (70 vs. 72% respectively, p = 0.17). Interrater agreement was moderate (κ = 0.65) at the threshold of 1.5, but high (κ = 0.84) at a threshold of 2, where also reviewers were significantly more confident (p < 0.01).

Conclusions

SISCOM is a clinically useful, routinely used modality in the preoperative work-up in many epilepsy surgery centers. We found no significant differences in localizing value of the IOZ using a threshold of 1.5 or 2, but interrater agreement and reader confidence were higher using a z-score threshold of 2.

Analysis of Brain SPECT Images Coregistered with MRI in Patients with Epilepsy: Comparison of Three Methods

BACKGROUND AND PURPOSE

SISCOM and STATISCOM were clinically proved to be effective for ictal/inter-ictal single-photon emission computed tomography (SPECT) analysis coregistered with magnetic resonance imaging (MRI) for seizure localization. Recently, a software package also became available for this analysis. This study aimed to investigate and compare the performance of these analysis methods for seizure localization.

METHODS

A total of 378 patients who underwent ^99m Tc-ethyl cysteinate dimer (ECD) SPECT scans were retrospectively reviewed and 28 remained after applying exclusion criteria. Their SPECT and MRI images were analyzed with SISCOM (with z-score of 1.5 and 2), STATISCOM, and MIMneuro, resulting in a total of 112 image data sets. Two experienced radiologists participated in the blind review process using a custom tool and they can mark up to two hyper- and/or hypoperfusion regions. Their review results were analyzed using the Jackknife Free Response Receiver-Operating Characteristics (JAFROC) test and the JAFROC figure-of-merit (FoM) was reported for each method. The interobserver agreement was also assessed using Cohen's kappa test.

RESULTS

Based on the readers' two choices, averaged FoM was 85.7%, 83.9%, 66.1%, and 51.8% for STATISCOM, MIMneuro, SISCOM (z-score = 2), and SISCOM (z-score = 1.5), respectively. The average confidence rating was 2.5, 2.3, 1.6, and 1.1 for STATISCOM, MIMneuro, SISCOM (z-score = 2), and SISCOM (z-score = 1.5), respectively. For interobserver agreement, kappa was .742 for STATISCOM, .816 for MIMneuro, .517 for SISCOM (z-score = 2), and .441 for SISCOM (z-score = 1.5; all P < .001).

CONCLUSION

Our study demonstrated that STATISCOM showed the best performance for seizure localization, which was closely followed by MIMneuro. In addition, MIMneuro was not inferior to SISCOM with either z-score.

Connectivity in ictal single photon emission computed tomography perfusion: a cortico-cortical evoked potential study

Subtraction ictal and interictal single photon emission computed tomography can demonstrate complex ictal perfusion patterns. Regions with ictal hyperperfusion are suggested to reflect seizure onset and propagation pathways. The significance of ictal hypoperfusion is not well understood. The aim of this study was to verify whether ictal perfusion changes, both hyper- and hypoperfusion, correspond to electrically connected brain networks. A total of 36 subtraction ictal and interictal perfusion studies were analysed in 31 consecutive medically refractory focal epilepsy patients, evaluated by stereo-electroencephalography that demonstrated a single focal onset. Cortico-cortical evoked potential studies were performed after repetitive electrical stimulation of the ictal onset zone. Evoked responses at electrode contacts outside the stimulation site were used as a measure of connectivity. The evoked responses at these electrodes were compared to ictal perfusion values noted at these locations. In 67% of studies, evoked responses were significantly larger in hyperperfused compared to baseline-perfused areas. The majority of hyperperfused contacts also had significantly increased evoked responses relative to pre-stimulus electroencephalogram. In contrast, baseline-perfused and hypoperfused contacts mainly demonstrated non-significant evoked responses. Finally, positive significant correlations (P < 0.05) were found between perfusion scores and evoked responses in 61% of studies. When the stimulated ictal onset area was hyperperfused, 82% of studies demonstrated positive significant correlations. Following stimulation of hyperperfused areas outside seizure onset, positive significant correlations between perfusion changes and evoked responses could be seen, suggesting bidirectional connectivity. We conclude that strong connectivity was demonstrated between the ictal onset zone and hyperperfused regions, while connectivity was weaker in the direction of baseline-perfused or hypoperfused areas. In trying to understand a patient's epilepsy, one should consider the contribution of all hyperperfused regions, as these are likely not random, but represent an electrically connected epileptic network.

The promise of subtraction ictal SPECT co-registered to MRI for improved seizure localization in pediatric epilepsies: Affecting factors and relationship to the surgical outcome

OBJECTIVE

Ictal SPECT is promising for accurate non-invasive localization of the epileptogenic brain tissue in focal epilepsies. However, high quality ictal scans require meticulous attention to the seizure onset. In a relatively large cohort of pediatric patients, this study investigated the impact of the timing of radiotracer injection, MRI findings and seizure characteristics on ictal SPECT localizations, and the relationship between concordance of ictal SPECT, scalp EEG and resected area with seizure freedom following epilepsy surgery.

METHODS

Scalp EEG and ictal SPECT studies from 95 patients (48 males and 47 females, median age=11years, (25th, 75th) quartiles=(6.0, 14.75) years) with pharmacoresistant focal epilepsy and no prior epilepsy surgery were reviewed. The ictal SPECT result was examined as a function of the radiotracer injection delay, seizure duration, epilepsy etiology, cerebral lobe of seizure onset identified by EEG and MRI findings. Thirty two patients who later underwent epilepsy surgery had postoperative seizure freedom data at <1, 6 and 12 months.

RESULTS

Sixty patients (63.2%) had positive SPECT localizations - 51 with a hyperperfused region that was concordant with the cerebral lobe of seizure origin identified by EEG and 9 with discordant localizations. Of these, 35 patients (58.3%) had temporal and 25 (41.7%) had extratemporal seizures. The ictal SPECT result was significantly correlated with the injection delay (p<0.01) and cerebral lobe of seizure onset (specifically frontal versus temporal; p=0.02) but not MRI findings (p=0.33), epilepsy etiology (p≥0.27) or seizure duration (p=0.20). Concordance of SPECT, scalp EEG and resected area was significantly correlated with seizure freedom at 6 months after surgery (p=0.04).

SIGNIFICANCE

Ictal SPECT holds promise as a powerful source imaging tool for presurgical planning in pediatric epilepsies. To optimize the SPECT result the radiotracer injection delay should be minimized to≤25s, although the origin of seizure onset (specifically temporal versus frontal) also significantly impacts the localization.

Nuclear Medicine Imaging in Pediatric Neurology

Nuclear medicine imaging can provide important complementary information in the management of pediatric patients with neurological diseases. Pre-surgical localization of the epileptogenic focus in medically refractory epilepsy patients is the most common indication for nuclear medicine imaging in pediatric neurology. In patients with temporal lobe epilepsy, nuclear medicine imaging is particularly useful when magnetic resonance imaging findings are normal or its findings are discordant with electroencephalogram findings. In pediatric patients with brain tumors, nuclear medicine imaging can be clinically helpful in the diagnosis, directing biopsy, planning therapy, differentiating tumor recurrence from post-treatment sequelae, and assessment of response to therapy. Among other neurological diseases in which nuclear medicine has proved to be useful are patients with head trauma, inflammatory-infectious diseases and hypoxic-ischemic encephalopathy.

"Eating" epilepsy revisited- an electro-clinico-radiological study

This study aimed to evaluate the clinical, video electroencephalographic and MRI attributes of patients with eating epilepsy (EE). Consecutive patients who were diagnosed with EE and underwent potential pre-surgical work-up from 2003 to 2012 formed the study cohort. Their electro-clinico-radiological and seizure outcome data were obtained from our prospectively maintained medical records. Out of 7094 patients who underwent evaluation for refractory seizures, 47 patients satisfied the criteria for EE. Twenty-three (48.9%) had exclusive EE; the remainder had a combination of predominantly eating-induced and unprovoked seizures with no differences noted in timing of seizures in relation to meals. Lesional epilepsy was seen in 34% of patients, with posterior cortex (PC; posterior temporo-parieto-occipital) predominance. In MRI negative patients, PC interictal epileptiform discharges were present in 34.4% of patients and multifocal in 20.6% of patients compared to the MRI positive group with 12.5% and 6.5%, respectively (p=0.003). Among 24 patients (51.1%) with co-existent unprovoked seizures, developmental delay and PC ictal onset was more prevalent (p=0.013 and 0.029) as compared to exclusive EE. The seizure frequency and outcome did not significantly differ between patients with or without MRI abnormality. Two patients underwent anterior temporal lobectomy, with persistence of their eating seizures postoperatively. EE is a complex reflex epilepsy of cryptogenic and symptomatic etiology. As opposed to the traditionally implied temporo-limbic mechanisms behind epileptogenesis, a multilobar network originating from the PC receiving sensory and visual inputs linked to the limbic-opercular pathways represents a plausible mechanism. Surgical selection should be diligent and cautious in this group of patients.