Ictal SPECT Images Research Articles

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.

Predicting the Outcome of Epilepsy Surgery by Covariance Pattern Analysis of Ictal Perfusion SPECT.

Previous studies on the utility of specific perfusion patterns in ictal brain perfusion SPECT for predicting the outcome of temporal lobe epilepsy surgery used qualitative visual pattern classification, semiquantitative region-of-interest analysis, or conventional univariate voxel-based testing, which are limited by intra- and interrater variability or low sensitivity to capture functional interactions among brain regions. The present study performed covariance pattern analysis of ictal perfusion SPECT using the scaled subprofile model for unbiased identification of predictive covariance patterns. Methods: The study retrospectively included 18 responders to temporal lobe epilepsy surgery (Engel I-A at 12 mo follow-up) and 18 nonresponders (≥Engel I-B). Ictal SPECT images were analyzed with the scaled subprofile model masked to group membership for unbiased identification of the 16 covariance patterns explaining the highest proportion of variance in the whole dataset. Individual expression scores of the covariance patterns were evaluated for predicting seizure freedom after temporal lobe surgery by receiver-operating-characteristic analysis. Kaplan-Meier analysis including all available follow-up data (up to 60 mo after surgery) was also performed. Results: Among the 16 covariance patterns only 1 showed a different expression between responders and nonresponders (P = 0.03). This favorable ictal perfusion pattern resembled the typical ictal perfusion pattern in temporomesial epilepsy. The expression score of the pattern provided an area of 0.744 (95% CI, 0.577-0.911, P = 0.004) under the receiver-operating-characteristic curve. Kaplan-Meier analysis revealed a statistical trend toward longer seizure freedom in patients with positive expression score (P = 0.06). The median estimated seizure-free time was 48 mo in patients with positive expression score versus 6 mo in patients with negative expression score. Conclusion: The expression of the favorable ictal perfusion pattern identified by covariance analysis of ictal brain perfusion SPECT provides independent (from demographic and clinical variables) information for the prediction of seizure freedom after temporal lobe epilepsy surgery. The expression of this pattern is easily computed for new ictal SPECT images and, therefore, might be used to support the decision for or against temporal lobe surgery in clinical patient care.

Relative contribution of individual versus combined functional imaging studies in predicting seizure freedom in pediatric epilepsy surgery: an area under the curve analysis.

The goal of this study was to evaluate the predictive value and relative contribution of noninvasive presurgical functional imaging modalities based on the authors' institutional experience in pursuing seizure-free surgical outcomes in children with medically refractory epilepsy. This was a retrospective, single-institution, observational cohort study of pediatric patients who underwent evaluation and surgical treatment for medically refractory partial epilepsy between December 2003 and June 2016. During this interval, 108 children with medically refractory partial epilepsy underwent evaluation for localization and resective epilepsy surgery. Different noninvasive functional imaging modalities, including ictal SPECT, FDG-PET, and magnetoencephalography-magnetic source imaging, were utilized to augment a standardized paradigm (electroencephalography/semiology, MRI, and neuropsychology findings) for localization. Outcomes were evaluated at a minimum of 2 years (mean 7.5 years) utilizing area under the receiver operating characteristic curve analysis. Localizing modalities and other clinical covariates were examined in relation to long-term surgical outcomes. There was variation in the contribution of each test, and no single presurgical workup modality could singularly and reliably predict a seizure-free outcome. However, concordance of presurgical modalities yielded a high predictive value. No difference in long-term outcomes between inconclusive (normal or diffusely abnormal) and abnormal focal MRI results were found. Long-term survival analyses revealed a statistically significant association between seizure freedom and patients with focal ictal EEG, early surgical intervention, and no history of generalized convulsions. Comprehensive preoperative evaluation utilizing multiple noninvasive functional imaging modalities is not redundant and can improve pediatric epilepsy surgical outcomes.

Subtraction Ictal SPECT coregistered to MRI (SISCOM) as a guide in localizing childhood epilepsy.

ObjectiveTo assess feasibility and efficacy of subtraction ictal SPECT coregistered to MRI (SISCOM) for epilepsy localization in children who are candidates for resective surgery.MethodsWe retrospectively reviewed all patients ≤16 years with drug‐resistant epilepsy screened for epilepsy surgery in the University Hospital of Leuven from January 2009 to January 2018. Fifty‐eight hospitalizations for ictal SPECT and 51 SISCOM analyses in 44 patients were included. Mean age was 9.1 years. Hospitalizations for SISCOM were analyzed in terms of multiple variables affecting feasibility and efficacy. The localization of SISCOM was compared with the localization of the presumed epileptogenic zone (PEZ) as determined by video‐EEG.ResultsSISCOM was feasible in terms of chronic medication management, rescue antiepileptic therapy during hospitalization, and operative timings. Radiotracer injection occurred within 30 seconds from seizure onset in 91.4% of the patients. ictal SPECT imaging was performed within two hours from injection in 100% of the patients (mean: 40 minutes). SISCOM was able to localize the PEZ in 51.0% (26/51) and to additionally lateralize the PEZ in 17.6% (9/51), achieving better localizations than ictal SPECT, FDG‐PET, and MRI (P < .01). SISCOM was useful to localize the PEZ in 25% of patients with poorly localizing video‐EEG and in 27.8% of MRI‐negative cases. The occurrence of habitual seizures during injection for ictal SPECT and the temporal localization of the PEZ both correlated with a better SISCOM localization (P < .05). 36.4% (16/44) patients were finally selected for resective surgery, with a 87.5% seizure‐free rate at 12 months. A localizing SISCOM was associated with seizure freedom in 66.7% and with a Engel I‐II in 75.0% of our patients.SignificanceSISCOM is a reliable tool to localize the epileptogenic zone in clinical practice and is both feasible and useful in children, adding precious presurgical information especially in patients with noninformative MRI or a poorly localizing video‐EEG.

B.04 Insight into the mesial frontal negative motor area: The girl with a very unusual interest in having her back patted

Background: Currently, there is limited insight in to the function of the mesial frontal negative motor area (NMA) and the anatomic structures implicated in its function. Methods: We present a patient with a Rett-like phenotype, refractory frontal lobe epilepsy, and reflexogenic seizures in which backpatting induced atonic seizures with a semiology resembling the patient falling asleep. The patient underwent video EEG monitoring and ictal/interictal SPECT imaging capturing the reflexogenic seizures. Iterative reconstruction was performed, with images co-registered to previously acquired MRI with subtraction Ictal-Interictal imaging co-registered to MRI. Results: Interictally, the patient’s EEG showed a slow background and right frontal spikes. Ictally, the patient had numerous subclinical frontal seizures. The reflexogenic seizures had an ictal pattern at the vertex (Cz) with the ictal SPECT imaging, showing hyperperfusion in the right mesial frontal region, both paramedian precentral and postcentral gyri, and right basal ganglia. Conclusions: Our findings support the hypothesis that the negative motor area may be activated by the primary sensory cortex; moreover, the ictal SPECT now suggests involvement of the basal ganglia in the NMA’s function.

FV 4. U-Fiber Density Imaging identifies specific microstructural alterations in the epileptogenic zone in individual patients with cryptogenic focal epileps

Patients with cryptogenic focal epilepsy (cFE), where conventional MRI does not show any structural lesion represent the fastest growing number of epilepsy surgery candidates in most tertiary referral centers. The absence of a visible surgical target challenges presurgical evaluation and requires complementary diagnostic methods to guide further investigations, especially intracranial EEG recordings. Here we present a new diagnostic approach, based on the quantification of regional u-fiber density to identify specific microstructural abnormalities in the epileptogenic zone of patients with cFE. 55 patients with cFE and 60 healthy controls were investigated. Diffusion Tensor Imaging (DTI) data was acquired on a GE Signa HDx 3T MRI Scanner, using an acquisition scheme with 64 diffusion weighted directions, a b-value of 1000 s/mm[b] and 2.4 mm slice thickness. Whole brain tractography was performed, creating an average of 1.05 million fiber tracts per subject. From this dataset, we specifically selected u-fibers, based on length, curvature and shape criteria. Density images were created, specifying the number of u-fibers within any 1 mm[c] voxel of the brain. These u-fiber density images (UFDI) were spatially normalized to a template in MNI-space and smoothed with an 8 mm kernel. For every single patient the UDFI was statistically compared against the control population, using SPM software. Clusters of significant reductions in UFDI were determined, thresholding at a minimum size of 5 cm[c] and a p-value <0.001, correcting for multiple comparisons using the family wise error (FWE) method. Localization of UFDI reductions was compared with clinical data from the presurgical evaluation. All patients had normal conventional MRI, using a specific epilepsy protocol on a 3T scanner. In 43 patients, a conclusive hypothesis on the epileptogenic zone could be derived, based on ictal and interictal EEG, seizure semiology, FDG-PET and ictal SPECT imaging and neuropsychological assessment. Only those 43 patients were included in the final analysis. In the remaining 12, clinical data was inconclusive, preventing further analysis of their UDFI alterations. Clusters of significant UFDI reductions were found in 91% of the patients and 78% of these reductions were consistent with the clinically suspected epileptogenic zone. Twelve patients underwent intracranial EEG recording with depth electrodes, confirming seizure onset in 74% of the detected UFDI reductions. Eight patients had resective surgery and the most frequent histopathological finding was a mild architectural disturbance with blurred gray-white matter border and ectopic neurons in the white matter. Quantitative UFDI has proven sensitive and specific to detect microstructural alterations in patients with cFE, superior to other complementary diagnostic methods. Histopathology has shown mild malformations of cortical development (MCD), a well-known cause of cFE. MCD typically affect the gray-white matter border, and this is exactly where u-fibers are located, spanning between neighboring gyri, directly underneath the cortex. We hypothesize the ectopic neurons disrupt the microstructural order of subcortical white matter, thereby artificially reducing the number of u-fibers we could reconstruct in this region. UFDI has become a routine diagnostic method in our department for all patients with cFE and is now routinely used to guide implantation of intracranial electrodes.

Eating epilepsy: Phenotype, MRI, SPECT and video-EEG observations

Eating epilepsy is one of the rare forms of reflex epilepsy precipitated by eating. Previous studies have demonstrated lesions due to variable aetiology involving the temporolimbic and suprasylvian regions. To study anatomical correlates of reflex eating epilepsy using multimodality investigations (MR imaging, video-EEG and SPECT). Six patients (M:F=3:3; mean age: 20.7±4.9 years) with eating epilepsy were subjected to MRI of brain, video-EEG studies and SPECT scan. These were correlated with phenotypic presentations. Among the five patients with ictal recording of eating epilepsy during video-EEG, semiology was characterized by behavioural arrest followed by either flexion or extension of trunk and neck and two patients had speech arrest and four had salivation from angle of mouth. Another patient had EEG changes during "thought about eating". Four patients had perisylvian frontal lobe lesions and one had high frontal lesion on MRI. Ictal EEG (n=6) showed ictal rhythmic slowing/fast activity in parieto-temporal (n=2) or fronto-temporal (n=4) regions with subsequent secondary generalization in three. Ictal and interictal SPECT imaging showed changes in frontal lobe (n=1), anterior temporal lobe (n=1), and parieto-insular region (n=1) suggesting it to be seizure onset zone. Three of four patients with structural lesions in MRI had concordant ictal EEG and ictal SPECT changes. Lesions near the perisylvian region might play a major role in eating epilepsy.

Surgical treatment of refractory status epilepticus in children

Refractory status epilepticus (RSE) is a life-threatening neurological emergency associated with high morbidity and mortality. Affected patients often require prolonged intensive care and can suffer multiple complications. Surgical intervention to control RSE is rarely used but can obviate the risks of prolonged seizures and intensive care treatment. Authors of the present study analyzed their experience with the surgical management of patients suffering from RSE. The Epilepsy Surgery Database at Miami Children's Hospital was reviewed for patients who had undergone surgery for RSE. Clinical presentation, electrophysiological profile, radiological data, surgical details, and postoperative course were evaluated. Between 1990 and 2012, 15 patients underwent surgery for uncontrolled seizures despite high-dose medical suppressive therapy. The mean preoperative duration of status epilepticus was 8 weeks. Ictal SPECT and FDG-PET imaging in conjunction with intraoperative electrophysiological studies helped to outline the extent of resection. Surgical intervention controlled seizures in all patients and facilitated the transition out of intensive care. Adverse events related to a prolonged intensive care unit stay included sepsis and respiratory complications. Four patients had worsened neurological function, developing hemiparesis and dysphasia. There was no operative mortality. Surgical intervention can successfully control refractory partial status epilepticus, prevent associated morbidity, and decrease intensive care unit stay. Ictal SPECT and PET are valuable in guiding resection.

Ictal and Interictal 99mTc-HMPAO Brain SPECT of a MELAS Case Presented With Epilepsy-like Visual Hallucination

A 55-year-old woman was diagnosed with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). She was referred for Tc-HMPAO brain SPECT because of visual hallucinations, which were suspected to be related to epileptic seizures. Ictal SPECT images showed remarkable hyperperfusion in the left occipital cortex, which returned to near-normal status on the interictal SPECT images after treatment with anticonvulsants. It is very rare to see such an ictal SPECT image of epileptic or epilepsy-like disorders, especially in the setting of MELAS syndrome with visual hallucination.

Quantitative multi-compartmental SPECT image analysis for lateralization of temporal lobe epilepsy

This study assesses the utility of compartmental analysis of SPECT data in lateralizing ictal onset in cases of a putative mesial temporal lobe epilepsy (mTLE). An institutional archival review provided 46 patients (18M, 28F) operated for a putative mTLE who achieved an Engel class Ia postoperative outcome. This established the standard to assure a true ictal origin. Ictal and interictal SPECT images were separately coregistered to T1-weighted (T1W) magnetic resonance (MR) image using a rigid transformation and the intensities matched with an l(1) norm minimization technique. The T1W MR image was segmented into separate structures using an atlas-based automatic segmentation technique with the hippocampi manually segmented to improve accuracy. Mean ictal-interictal intensity difference values were calculated for select subcortical structures and the accuracy of lateralization evaluated using a linear classifier. Hippocampal SPECT analysis yielded the highest lateralization accuracy (91%) followed by the amygdala (87%), putamen (67%) and thalamus (61%). Comparative FLAIR and volumetric analyses yielded 89% and 78% accuracies, respectively. A multi-modality analysis did not generate a higher accuracy (89%). A quantitative anatomically compartmented approach to SPECT analysis yields a particularly high lateralization accuracy in the case of mTLE comparable to that of quantitative FLAIR MR imaging. Hippocampal segmentation in this regard correlates well with ictal origin and shows good reliability in the preoperative analysis.

Contribution of subtraction ictal SPECT coregistered to MRI to epilepsy surgery: a multicenter study

A multicenter prospective study was performed to assess the additional value of a subtraction ictal SPECT coregistered to MRI (SISCOM) technique to traditional side-by-side comparison of ictal- and interictal SPECT images in epilepsy surgery. One hundred and twenty-three patients with temporal and extratemporal lobe epilepsy who had undergone epilepsy surgery after evaluation of scalp ictal and interictal electroencephalogram (EEG), MRI, and ictal and interictal SPECT scans were followed up in terms of postsurgical outcome for a period of at least 1 year. Three reviewers localized the epileptogenic focus using ictal and interictal SPECT images first by side-by-side comparison and subsequently by SISCOM. Concordance of the localization of the epileptogenic focus by SPECT diagnosis with the surgical site and inter-observer agreement between reviewers was compared between side-by-side comparison and SISCOM. Logistic regression analysis was performed in predicting the surgical outcome with the dependent variable being the achievement of a good postsurgical outcome and the independent variables using the SISCOM, side-by-side comparison of ictal and interictal SPECT images, MRI, and scalp ictal EEG. The SISCOM presented better concordance in extratemporal lobe epilepsy and less concordance in temporal lobe epilepsy than side-by-side comparison. Inter-observer concordance was higher in SISCOM than in side-by-side comparison. Much higher concordance of the epileptogenic focus by SPECT diagnosis with the surgical site was obtained in patients with good surgical outcome than in those with poor surgical outcome. These differences in concordance between good and poor surgical outcomes were greater in SISCOM than in side-by-side comparison. Logistic regression analysis showed the highest odds ratio of 12.391 (95% confidence interval; 3.319, 46.254) by SISCOM evaluation for concordance of the epileptogenic focus with the surgical site in predicting good surgical outcome. A SISCOM technique of ictal and interictal SPECT images provides higher predictive value of good surgical outcome and more reliability on the diagnosis of the epileptogenic focus than side-by-side comparison in medically intractable partial epilepsy.

A Neurofunctional Evaluation Strategy for Presurgical Selection of Temporal Lobe Epilepsy Patients

Introduction Temporal lobe epilepsy (TLE) is the prototype of a surgically correctable syndrome. Successful surgical outcomes depend on a thorough presurgical evaluation aimed primarily at identifying the epileptogenic zone. Objective Describe the noninvasive presurgical selection and evaluation strategy for TLE patients introduced at the International Neurological Restoration Center (CIREN) in Havana, Cuba, and evaluated between 2001 and 2006 for its accuracy in identifying candidates for non-lesional resection surgery. Methods Ictal onset electrographic patterns of 1,679 seizures in 72 patients with drug-resistant partial epilepsy, obtained through longterm scalp Video EEG (V-EEG) monitoring, were evaluated. The correlation between the V-EEG-defined epileptogenic zone and the dysfunction shown by single photon emission computed tomography (ictal and interictal brain SPECT) and nuclear magnetic resonance spectroscopy (MRS) was established. Results V-EEG monitoring determined that 44.4% of evaluated patients had complex partial temporal lobe seizures. Identification of patients with medial temporal epilepsy (MTE) increased as a result of lateralization and localization of the dominant mean ictal pattern frequency (5.56 ± 1.31 Hz) during the period of maximum spectral power VARETA localization of an ictal epileptiform activity source coincided with the epileptogenic zone in all TLE patients who subsequently underwent a successful temporal lobectomy. Semiquantitative analysis of ictal and interictal brain SPECT images, as well as metabolic ratios measured by MRS, combined with V-EEG findings, enabled localization/lateralization of the epileptogenic zone in TLE patients whose MRIs were normal or showed bilateral structural abnormalities. Conclusions Confirmation of correct localization/lateralization of the epileptogenic zone following successful surgical outcomes in selected TLE patients led CIREN to develop a surgical treatment strategy for patients in Cuba with drug-resistant temporal lobe epilepsy. This strategy offers an appropriate, cost-effective treatment alternative for developing countries like Cuba, with the benefit of significantly improving TLE patients' quality of life.

Utility of subtraction ictal SPECT images in detecting focal leading activity and understanding the pathophysiology of spasms in patients with West syndrome

The aims of the study were to evaluate the detectability of focal leading activity in three cases of West syndrome having focal abnormal activity on EEG by comparing subtraction ictal images and raw ictal images, and to interpret the results in 16 cases. Subtraction images were constructed using iNeurostat (revision 2). In three cases with focal abnormal activity on EEG, subtraction ictal images reflected the EEG findings; in contrast, raw ictal images did not. Diverse degrees of cortical hyperperfusion, ranging from zero to 10 sites, seen in the other 13 cases seemed to reflect spasm pathophysiology and rapid spasm propagation. Subtraction ictal images also allowed the ready detection of hyperperfusion of subcortical structures and of a tight cortico-subcortical relationship in a subset of cases. We showed the superiority of subtraction ictal images in detecting the focal epileptic region and in showing propagation pathways from the cortex to subcortical structures. A subset of spasms in WS may be focal cortical-onset secondarily generalized seizures. We believe that subtraction analysis is valuable in patients with complex WS who have partial seizures and spasms simultaneously along with focal epileptic EEG activity, as they will likely be candidates for epilepsy surgery.

A Neurological Cause of Recurrent Choking During Sleep

We describe a case of nocturnal choking episodes caused by insular seizures. Recurrent choking spells from sleep showed no response to treatment for sleep apnea or gastroesophageal reflux. Laryngoscopy revealed no abnormalities. Although continuous EEG monitoring during events was normal, ictal SPECT imaging showed increased radiotracer uptake in the left insular region, an area involved in sensation of the upper gastrointestinal tract. The episodes remitted after initiation of an antiepileptic drug. Obstructive sleep apnea is the most common cause for presentation to a sleep center, but seizures should remain in the differential diagnosis of nocturnal choking episodes.

Imagerie morphologique et fonctionnelle : particularités chez l’enfant

Surgery of partial epilepsies in childhood has largely benefited from the recent advances of imaging techniques, which carry a triple goal: (1) to contribute to the localization of the epilepsy onset zone, (2) to detect and delineate an underlying lesion, and (3) to study the spatial relationship between the epileptogenic zone and the neighboring functional cortex, in order to select patients and plan the resection. This noninvasive presurgical imaging workup must be compared to clinical and electrical data to estimate the postoperative prognosis, while invasive techniques such as SEEG, cortical stimulations, and IAT often remain indispensable in difficult cases, i.e., in cryptogenic epilepsies. As in adults, advances in MRI allow us to detect more and more subtle underlying lesions, but this requires repeating MR studies during early childhood and using adapted sequence parameters to account for ongoing myelination. Ictal SPECT and PET imaging prove especially useful in planning depth electrode placement when video-EEG is not contributive, when MRI looks normal or shows multiple abnormalities, or in cases of discrepant findings. Multimodal imaging greatly enhances the sensitivity of all of these techniques. Finally, functional MRI of motor and language functions provide noninvasive cortical mapping of essential functions, using age-adapted paradigms, in cooperating children from age five to six and from IQs around 60.

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

To investigate the pattern of perfusion abnormalities in ictal and interictal brain perfusion SPECT images (BSI) from patients with temporal lobe epilepsy (TLE). It was acquired interictal and ictal BSI from 24 patients with refractory TLE. BSIs were analyzed by visual inspection and statistical parametric mapping (SPM2). Statistical analysis compared the patients group to a control group of 50 volunteers. The images from patients with left-TLE were left-right flipped. It was not observed significant perfusional differences in interictal scans with SPM. Ictal BSI in SPM analysis revealed hyperperfusion within ipsilateral temporal lobe (epileptogenic focus) and also contralateral parieto-occipital region, ipsilateral posterior cingulate gyrus, occipital lobes and ipsilateral basal ganglia. Ictal BSI also showed areas of hypoperfusion. In a group analysis of ictal BSI of patients with TLE, voxel-wise analysis detects a network of distant regions of perfusional alteration which may play active role in seizure genesis and propagation.

Free Communications: Surgery

Abstract Ictal SPECT in Supplementary Motor Area Seizure. 1 Masafumi Fukuda, 2 Hiroshi Masuda, 2 Junpei Honma, 2 Ayataka Fujimoto, 2 Shigeki Kameyama, and 1 Ryuichi Tanaka ( 1 Department of Neurosurgery, Brain Research Institute, University of Niigata 2 Department of Neurosurgery, Epilepsy Center, Nishi-Niigata-Chuo National Hospital, Niigata, Japan ). Purpose: The clinical semiology of supplementary motor area (SMA) seizures is characterized by abrupt, bilateral, tonic posturing of the extremities, vocalization, mostly preserved consciousness, and short duration. The SMA has multiple reciprocal connections with the primary sensorimotor cortex (SMC), anterior cingulate cortex (ACC), and various parietal somatosensory areas. Therefore, the epileptic discharges from SMA can rapidly propagate to these structures. In the present study, we used ictal SPECT to clarify the propagation pathways of epileptic discharges in patients with SMA seizures who were evaluated with chronic subdural electrodes for a definite localization of the seizure onset zone. Methods: We studied four patients (four males; age range, 18–27 years) with SMA seizures. The seizures occurred 1–10 times per day and lasted for 10–15 seconds. In two patients, proton magnetic resonance (MR) imaging revealed a hyperintense lesion indicative of focal cortical dysplasia (FCD) in the right SMA, where subdural electrode monitoring also localized the ictal onset. After complete resection of the FCD including the epileptic foci, these patients remained seizure free. In the other two patients, MR images were normal, but subdural electrode monitoring permitted verification of ictal onset in the left SMA. After partial resection of the SMA, including the epileptic foci, these patients experienced a significant (>90%) reduction of seizure frequency and were classified as class IIB outcome according to Engel's classification. SPECT studies were performed in all patients as a preoperative evaluation. Ictal SPECT was performed during seizures that occurred while the patients were undergoing inpatient video-EEG monitoring. The radioisotope 99mTc-ECD was injected immediately after seizure onset. The interval from seizure onset to the time of injection was no more than 3 seconds. Ictal and interictal SPECT images were acquired within 30 minutes after radioisotope injections. Regional cerebral blood flow (rCBF) measurements obtained under ictal and interictal conditions were compared on a voxel-by-voxel basis using the paired t-test option in SPM99. Images from the two patients with no lesions on MR images were reversed such that the hemisphere having epileptic foci appeared on the right. The changes were considered significant when the p-value was less than 0.001, uncorrected for multiple independent comparisons. Results: SPM analysis revealed significant increases of rCBF in bilateral ACC (x= 10, y=–6, z= 44 mm; Zmax= 4.97 and x=–18, y=–20, z= 42; Zmax= 4.49), the right globus pallidus (x= 20, y=–2, z= 2; Zmax= 4.23), and the cerebellar hemisphere (x=–26, y=–48, z=–38; Zmax= 4.22) in ictal condition. The right ACC contained a cluster with a submaximum in the right primary SMC (x= 36, y=–18, z= 46; Z= 4.35). No reduction in rCBF was observed in ictal condition. Conclusions: In patients with SMA seizures, hyperperfusion areas depicted on ictal SPECT did not localize within the SMA but spread to the adjacent cortex such as ACC and SMC ipsilateral to the epileptic foci. Additionally, epileptic discharges propagated to remote areas such as the globus pallidus and cerebellum that have direct or indirect reciprocal connections with the SMA. We caution that in patients with SMA seizures, ictal SPECT localization is not always concordant with epileptogenic foci but reveals already spread seizure activities.

Stereotactic radiosurgery planning with ictal SPECT images

This paper is motivated by a clinical requirement to utilise ictal SPECT images for target localisation in stereotactic radiosurgery treatment planning using the xknife system which only supports CT and MRI images. To achieve this, the SPECT images were converted from raw (pixel data only) format into a part 10 compliant DICOM CT fileset. The minimum requirements for the recasting of a raw format image as DICOM CT or MRI data set are described in detail. The method can be applied to the importation of raw format images into any radiotherapy treatment planning system that supports CT or MRI import. It is demonstrated that the combination of the low spatial resolution SPECT images, depicting functional information, with high spatial resolution MRI images, which show the structural information, is suitable for stereotactic radiosurgery treatment planning.

Late postictal residual perfusion abnormality in epileptogenic zone found on 6-hour postictal SPECT.

Temporal evolution of regional hyperperfusion in the late postictal stage in epilepsy has not been clearly defined. To establish the late temporal evolution of the perfusion in epileptogenic zones using 6-hour postictal SPECT. Ictal 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) SPECT was performed in 10 patients with intractable epilepsy (4 temporal lobe epilepsy, 6 neocortical epilepsy) followed by delayed acquisition and another 6-hour postictal SPECT after reinjection of 99mTc-HMPAO. The delayed acquired SPECT was subtracted from the reinjection SPECT to yield the 6-hour postictal SPECT. Interictal SPECT was acquired on another day. Late postictal perfusion was examined visually, and asymmetric indexes were compared with each other on ictal, 6-hour postictal, and interictal SPECT. Ictal SPECT images of delayed acquisition were visually and quantitatively similar to those of early acquisition. In 7 of 10 patients, 6-hour postictal SPECT showed hyperperfusion. In one patient, the 6-hour postictal SPECT image showed less perfusion than the interictal SPECT image in the epileptogenic zone. Late postictal hyperperfusion was found in more than half of the patients. Postictal perfusion abnormalities did not come back to the interictal phase 6 hours after ictus and these were identified on ictal/postictal 99mTc- HMPAO SPECT.

The role of quantitative ictal SPECT analysis in the evaluation of nonepileptic seizures.

Nonepileptic seizures may represent difficult diagnostic problems. Identifying their presence and frequency is critical for determining appropriate treatment. The authors investigated the value of quantitative perfusion changes as measured by ictal single-photon emission tomography (SPECT) difference images in differentiating nonepileptic from epileptic seizures. Eleven patients with a clinical suspicion of nonepileptic events had ictal and interictal technetium-99m hexamethylpropylene amine SPECT scans during continuous audiovisual surface electroencephalogram (EEG) monitoring. The authors analyzed perfusion difference images based on registration, normalization, and subtraction of ictal and interictal SPECT images. The difference images were registered to each patient's magnetic resonance imaging scan to anatomically localize ictal perfusion changes. Three of 11 patients also carried the diagnosis of epilepsy and were taking antiepileptic medication. Five patients were taking antiepileptic drugs, but the diagnosis of epilepsy was not confirmed. In all patients, continuous video EEG monitoring revealed no ictal EEG findings. In nine of these patients, visual interpretation of ictal SPECT was suggestive of localized increased (n = 6) or decreased perfusion (n = 3). In all patients, however, no blood flow changes were noted on quantitative SPECT analysis with injections performed during the seizure-like event, suggesting the diagnosis of pseudoseizures. The authors' results suggest that quantitative ictal SPECT analysis is a useful tool in the diagnosis of nonepileptic seizures.