Interictal Positron Emission Tomography Research Articles

Imaging in the presurgical evaluation of epilepsy

Während zwei Drittel der PatientInnen mit Epilepsie durch Medikamente anfallsfrei werden, ist die Erkrankung bei 30 % pharmakoresistent. Bei pharmakoresistenter fokaler Epilepsie bietet die Epilepsiechirurgie eine etwa 65 %ige Chance auf Anfallsfreiheit. Vorab muss der Anfallsfokus exakt eingegrenzt werden, wofür bildgebende Methoden unverzichtbar sind. In den letzten Jahren hat sich in der Prächirurgie der Anteil von PatientInnen mit unauffälliger konventioneller Magnetresonanztomographie (MRT) erhöht. Allerdings konnte die Sensitivität der MRT durch spezielle Aufnahmesequenzen und Techniken der Postprozessierung gesteigert werden. Die Quellenlokalisation des Signals von Elektro- und Magnetenzephalographie (EEG und MEG) verortet den Ursprung iktaler und interiktaler epileptischer Aktivität im Gehirn. Nuklearmedizinische Untersuchungen wie die interiktale Positronen-Emissions-Tomographie (PET) und die iktale Einzelphotonen-Emissionscomputertomographie (SPECT) detektieren chronische oder akute anfallsbezogene Veränderungen des Hirnmetabolismus und können auch bei nichtlokalisierendem MRT auf den epileptogenen Fokus hinweisen. Alle Befunde zusammengenommen werden zur Planung eventueller invasiver EEG-Ableitungen und letztlich der chirurgischen Operation eingesetzt. Konkordante Befunde sind mit besseren chirurgischen Ergebnissen assoziiert und zeigen auch im Langzeitverlauf signifikant höhere Anfallsfreiheitsraten.

Insular interictal positron emission tomography hypometabolism in patients with ictal asystole.

We aimed to explore brain area(s) involved in the generation of ictal asystole (IA) by analyzing the interictal positron emission tomography (PET) metabolism of patients with IA recorded by video-electroencephalography or video-stereo-electroencephalography. We identified in our cohort of focal epilepsy patients who had undergone presurgical evaluation those who had a recorded period of IA of more than 3 s. We investigated the anatomometabolic changes (interictal 18 F-fluorodeoxyglucose PET) of these patients in comparison with (1) healthy subjects with similar age and sex distribution (n=19) using whole-brain voxel-based analysis (p-voxel < .001, p-cluster < .05, uncorrected) and (2) patients without IA with similar age and seizure onset zone (n=55). We found 12 patients with IA. Epilepsy was mainly temporal (four right temporal mesial, four bitemporal, two left temporal lateral, one right temporal lateral, and one right temporal "plus"). Seven patients had negative magnetic resonance imaging. Whole-brain statistical analysis of PET imaging was performed at the voxel level, showing that in comparison to healthy subjects and to epileptic patients without IA, a hypometabolism in the right posterior insula characterized epileptic patients with IA. Our study suggests involvement of the right posterior insula-a part of the central autonomic network-in the pathophysiological mechanism of IA.

Neural networks underlying hyperkinetic seizures: A quantitative PET and SEEG study

ObjectiveHyperkinetic seizures (HKS) are characterized by complex movements that commonly occur during seizures arising from diverse cortical structures. A common semiology network may exist and analyzing the anatomo-electrical mechanisms would facilitate presurgical evaluation. Here, quantitative positron emission tomography (PET) and stereoelectroencephalography (SEEG) analysis was used to explore the underlying mechanism of HKS. MethodsWe retrospectively collected patients with epilepsy with HKS between 2014 and 2019. The interictal PET data of patients with epilepsy with HKS were compared with those of 25 healthy subjects using statistical parametric mapping to identify regions with significant hypometabolism. Then, regions of interest (ROI) for SEEG analysis were identified based on the results of PET analysis. Patients in which the ROIs were covered by intracerebral electrodes were selected for further analysis. Stereoelectroencephalography –clinical correlations with latency measurements were analyzed, and we also performed coherence analysis among ROIs both before and during HKS. ResultsBased on the inclusion criteria, 27 patients were analyzed. In the PET analysis, significant hypometabolism was observed in the ipsilateral dorsoanterior insular lobe, bilateral mesial frontal lobes (supplementary motor area/middle cingulate cortex, SMA/MCC), and the bilateral heads of the caudate nuclei in patients with HKS compared with the control group (p < 0.001). We selected dorsoanterior insula and SMA/MCC as ROIs for SEEG analysis. Eight patients with 23 HKS events were selected for further analysis. There was a linear correlation between the ictal involvement of both the dorsoanterior insula and SMA/MCC with the onset of HKS. Stereoelectroencephalography analysis indicated alpha range activity seemed more often associated with dorsoanterior insula and SMA/MCC involvement during HKS. ConclusionsThe dorsoanterior insular lobe, mesial frontal lobes (SMA/MCC), and the bilateral heads of the caudate nuclei were probably involved in the generation of HKS. The SEEG analysis further indicated that the occurrence of HKS might be partly associated with synchronized rhythmical alpha activity between dorsoanterior insula and SMA/MCC.

The Rolandic operculum generates different semiologies in insulo-opercular and temporal lobe epilepsies

PurposeThe role of the Rolandic operculum in in mesial temporal lobe epilepsy (MTLE) is to produce oroalimentary automatisms (OAAs). In insulo-opercular epilepsy (IOE), the Rolandic operculum may produce perioral muscle clonic or tonic movements or contractions. This paper aims to confirm the symptomatogenic zone of facial symptoms in IOE and to explain this phenomenon. MethodsA total of 45 IOE patients and 15 MTLE patients were analyzed. The patients with IOE were divided into facial (+) and (-) groups according to the facial symptoms. The interictal positron emission tomography (PET) data were compared among groups. Furthermore, electroclinical correlation, functional connectivity and energy ratio (ER) were analyzed with stereo-electroencephalography (SEEG). ResultsIntergroup PET differences were observed mainly in the Rolandic operculum. Electroclinical correlation showed that the Rolandic operculum was the only brain area showing any correlations. Compared with the facial (-) group, the facial (+) group showed stronger functional connectivity and a higher ER in the alpha 1, alpha 2 and beta sub-bands. In the Rolandic operculum, compared with those of the MTLE group, the h2 and ER of the facial (+) group were higher in the high frequency sub-bands. Intergroup comparison of the ER in the seizure onset zones (SOZ) showed no significant difference. SignificanceThe symptomatogenic zone of facial symptoms in IOE is the Rolandic operculum. Seizure propagation to the Rolandic operculum generates different semiologies because of the different synchronization frequencies and energies of the sub-bands depending on the site of seizure origin. This may be due to the complex spreading pathway from the SOZ to the symptomatogenic zone.

Evaluation of brain FDG PET images in temporal lobe epilepsy for lateralization of epileptogenic focus using data mining methods

Background/aimIn temporal lobe epilepsy (TLE), brain positron emission tomography (PET) performed with F-18 fluorodeoxyglucose (FDG) is commonly used for lateralization of the epileptogenic temporal lobe. In this study, we aimed to evaluate the success of quantitative analysis of brain FDG PET images using data mining methods in the lateralization of the epileptogenic temporal lobe. Materials and methods Presurgical interictal brain FDG PET images of 49 adult mesial TLE patients with a minimum of 2 years of postsurgical follow-up and Engel I outcomes were retrospectively analyzed. Asymmetry indices were calculated from PET images from the mesial temporal lobe and its contiguous structures. The J48 and the logistic model tree (LMT) data mining algorithms were used to find classification rules for the lateralization of the epileptogenic temporal lobe. The classification results obtained by these rules were compared with the physicians’ visual readings and the findings of single-patient statistical parametric mapping (SPM) analyses in a test set of 18 patients. An additional 5-fold cross-validation was applied to the data to overcome the limitation of a relatively small sample size. Results In the lateralization of 18 patients in the test set, J48 and LMT methods were successful in 16 (89%) and 17 (94%) patients, respectively. The visual consensus readings were correct in all patients and SPM results were correct in 16 patients. The 5-fold cross-validation method resulted in a mean correct lateralization ratio of 96% (47/49) for the LMT algorithm. This ratio was 88% (43 / 49) for the J48 algorithm.Conclusion Lateralization of the epileptogenic temporal lobe with data mining methods using regional metabolic asymmetry values ​​obtained from interictal brain FDG PET images in mesial TLE patients is highly accurate. The application of data mining can contribute to the reader in the process of visual evaluation of FDG PET images of the brain.

Clinico-pathological features of temporal lobe epilepsy with enlarged amygdala

To summarize the clinical, video electroencephalogram (VEEG), radiological and pathological features of 3 patients of temporal lobe epilepsy (TLE) with amygdala enlargement (AE). Three TLE patients with AE who were hospitalized in Peking University International Hospital were collected. The above features were retrospectively analyzed, and the amygdala volume was measured as well. Of all the 3 patients, 2 were females and 1 male, whose seizure onset ages varied from 21 to 40 years. Two cases presented with secondarily generalized tonicclonic seizures after falling asleep during the night. One of the 2 cases had complex partial seizures (CPSs) with episodic memory and automatism after one year, and the third one had CPSs with lip smacking and tongue wagging during the night. All the patients suffered from obvious anxious disorder. Unilateral AE by MRI was demonstrated in the 3 cases, one on the right side, and the other two on the left side. The average amygdala volume of the enlarged side and the other side were (2 123.7±131.8) mm3 and (1 276.3±156.9) mm3, respectively. Unilateral interictal epileptic discharges were ipsilateral to the AE in 2 cases, while the other patient showed bilateral interictal epileptic discharges. The ictal VEEG showed that the seizure onset zone was ipsilateral to the AE and was confined to the anterior and middle temporal regions in the 3 patients. The interictal single-photon emission computed tomography (SPECT) was negative in 2 cases. The interictal positron emission tomography (PET) showed hypometabolism in the AE in one case. The histological pathology revealed focal cortical dysplasia in the amygdala and temporal lobe in the 3 cases, and one of the 3 cases was combined with hippocampal sclerosis. All the patients became seizure free after surgery in the half year following-up. VEEG revealed slow wave activity and occasional spike wave in the operated side. AE may be one subtype of TLE. It is necessary to recognize AE in TLE with MRI-negative. For those poorly responsive to antiepileptic drugs, surgical treatment could provide a better solution. Focal cortical dysplasia may be one of the most common pathological features of TLE with AE.

F09. Predictors of post-surgical seizure outcomes in refractory temporal lobe epilepsy

Introduction The effectiveness of epilepsy surgery depends on precise identification of epileptogenic zone and historically temporal lobe epilepsy has been described to have highest seizure freedom rates after surgery. Researches have previously analyzed multiple variables with distinct predictive values of postsurgical outcome. We attempted to identify prognostic variables in temporal lobe epilepsy using the diagnostic studies that are routinely performed during presurgical evaluation. Methods Retrospective analysis of electroencephalogram (EEG), Magnetic resonance imaging (MRI), Positron emission tomography (PET), Single-photon emission computed tomography (SPECT) and Magnetoencephalography (MEG) was performed on 93 adult patients with refractory temporal lobe epilepsy who underwent selective temporal lobectomy was performed. Outcomes was assessed on a clinical basis using modified Engel’s classification. Results At one year follow up, there were 73 patients (78.5%) with good surgical outcome (E1 & E2) and 10 patients (10%) with poor outcome (E3 & E4) and 10 patients were lost to follow up. EEG findings such as consistently unilateral interictal epileptiform discharges (IEDs) during NREM sleep (91%), consistent lateralized focal ictal onset (90%) and IEDs concordant with ictal onset on scalp and intracranial EEG were highly predictive of a good outcome. Mesial temporal sclerosis and other hippocampal abnormalities on MRI correlated with good outcome (82–100%). Concordant findings on ictal and interictal EEG MRI, PET and MEG also correlated with good outcome. The type of ictal onset pattern did not have significant difference. In patients with poor outcome (E3 & E4), there was lack of correlation between MRI/PET with interictal and ictal EEG. The presence of any lesion on the MRI did not seem to make any difference in outcome, especially in patients who skipped an invasive monitoring. In two-thirds of the patients with poor outcome, having concordant MRI findings and ictal onset did not change the surgical outcome. Subset analysis of non-lesional patients with hypometabolism on PET had a good outcome (33%). Conclusion Several factors have been identified with some postsurgical predictive value and majority of the studies have included patients with mesial temporal sclerosis (MTS), which is usually considered to be of excellent prognostic value. Contrary to this, the presence of MTS on MRI, did not improve the outcome in our study. This may indicate that the presence of MTS is an independent variable, and other diagnostic studies should be considered to make a reasonable prognostication and such information can be used to counsel the patients appropriately.

Predictive value of preoperative statistical parametric mapping of regional glucose metabolism in mesial temporal lobe epilepsy with hippocampal sclerosis

ObjectiveThis study was designed to use statistical parametric mapping of interictal positron-emission tomography using [18F]Fluorodeoxyglucose (FDG-PET) to compare the brain metabolisms of patients with mesial temporal lobe epilepsy (MTLE)/hippocampal sclerosis and controls. Another aim of this study was to analyze the potential differences among patients in terms of epilepsy duration, side of hippocampal sclerosis, histopathological findings, insult in their history, and postoperative outcomes. MethodsWe analyzed FDG-PET scans from 49 patients with MTLE/hippocampal sclerosis and 24 control subjects. We analyzed the differences in regional glucose metabolism between the patients and the control group and within the patient group using multiple variables. ResultsWe observed widespread hypometabolism in the patient group in comparison with the control group in temporal and extratemporal areas on the epileptogenic side (ES). On the nonepileptogenic side (NES), we observed the most hypometabolism in the thalamus and the anterior and middle cingulate gyrus. In the group of patients with more severe hippocampal sclerosis, we observed statistically significant hypometabolism in the insula on the ES. In patients with poor postoperative outcomes, we found statistically significant hypometabolism in the insula on the ES and the temporal pole (TP) on the NES. Patients with any insult in their history showed hypermetabolism in the TP on both sides. ConclusionOur study showed that there are widespread changes in metabolism in patients with MTLE in comparison to controls, either inside or outside the temporal lobe. There are significant differences among these patients in terms of postoperative outcomes, degree of hippocampal sclerosis, and insults in their history.

Seizure onset zone localization using postictal hypoperfusion detected by arterial spin labelling MRI.

Neurological dysfunction following epileptic seizures is a well-recognized phenomenon. Several potential mechanisms have been suggested to explain postictal dysfunction, with alteration in cerebral blood flow being one possibility. These vascular disturbances may be long lasting and localized to brain areas involved in seizure generation and propagation, as supported by both animal and human studies. Therefore, measuring perfusion changes in the postictal period may help localize the seizure onset zone. Arterial spin labelling is a non-invasive, rapid and reproducible magnetic resonance imaging technique that measures cerebral perfusion. To this end, we measured postictal perfusion in patients with drug resistant focal epilepsy who were admitted to our seizure-monitoring unit for presurgical evaluation. Twenty-one patients were prospectively recruited and underwent arterial spin labelling scanning within 90 min of a habitual seizure. Patients also underwent a similar scan in the interictal period, after they were seizure-free for at least 24 h. The acquired scans were subtracted to identify the areas of significant postictal hypoperfusion. The location of the maximal hypoperfusion was compared to the presumed seizure onset zone to assess for concordance. Also, the localizing value of this technique was compared to other structural and functional imaging modalities. Postictal perfusion reductions of >15 units (ml/100 g/l) were seen in 15/21 patients (71.4%). In 12/15 (80%) of these patients, the location of the hypoperfusion was partially or fully concordant with the location of the presumed seizure onset zone. This technique compared favourably to other neuroimaging modalities, being similar or superior to structural magnetic resonance imaging in 52% of cases, ictal single-photon emission computed tomography in 60% of cases and interictal positron emission tomography in 71% of cases. Better arterial spin labelling results were obtained in patients in whom the seizure onset zone was discernible based on non-invasive data. Thus, this technique is a safe, non-invasive and relatively inexpensive tool to detect postictal hypoperfusion that may provide useful data to localize the seizure onset zone. This technique may be incorporated into the battery of conventional investigations for presurgical evaluation of patients with drug resistant focal epilepsy.

Current use of imaging and electromagnetic source localization procedures in epilepsy surgery centers across Europe.

In 2014 the European Union-funded E-PILEPSY project was launched to improve awareness of, and accessibility to, epilepsy surgery across Europe. We aimed to investigate the current use of neuroimaging, electromagnetic source localization, and imaging postprocessing procedures in participating centers. A survey on the clinical use of imaging, electromagnetic source localization, and postprocessing methods in epilepsy surgery candidates was distributed among the 25 centers of the consortium. A descriptive analysis was performed, and results were compared to existing guidelines and recommendations. Response rate was 96%. Standard epilepsy magnetic resonance imaging (MRI) protocols are acquired at 3 Tesla by 15 centers and at 1.5 Tesla by 9 centers. Three centers perform 3T MRI only if indicated. Twenty-six different MRI sequences were reported. Six centers follow all guideline-recommended MRI sequences with the proposed slice orientation and slice thickness or voxel size. Additional sequences are used by 22 centers. MRI postprocessing methods are used in 16 centers. Interictal positron emission tomography (PET) is available in 22 centers; all using 18F-fluorodeoxyglucose (FDG). Seventeen centers perform PET postprocessing. Single-photon emission computed tomography (SPECT) is used by 19 centers, of which 15 perform postprocessing. Four centers perform neither PET nor SPECT in children. Seven centers apply magnetoencephalography (MEG) source localization, and nine apply electroencephalography (EEG) source localization. Fourteen combinations of inverse methods and volume conduction models are used. We report a large variation in the presurgical diagnostic workup among epilepsy surgery centers across Europe. This diversity underscores the need for high-quality systematic reviews, evidence-based recommendations, and harmonization of available diagnostic presurgical methods.

Can Ictal F18-FDG PET/CT Drawing Epileptogenic Zone in Refractory Focal Epilepsy? Histopathological and Outcome Correlation

Unlike interictal Positron Emission Tomography (PET), ictal PET is not regularly used in the study of refractory focal epilepsy, and its usefulness in presurgical evaluations, and prognosis value have not been established. The aim is to present six patients with epilepsy whose PET/CT brain scans showed focal hypermetabolism, and analyze their correlation with the histopathological findings and clinical results. We reviewed 146 18F-FDG PET/CT scans performed on patients with refractory focal epilepsy. Only those cases with hypermetabolic foci which were subsequently surgically resected were selected. The epidemiological and clinical data were reviewed in addition to the brain MRI, Electroencephalography (EEG), video-EEG monitoring, intraoperative Electrocorticography (ECoG), histopathology, and postsurgical outcome. The PET findings were correlated with the clinical characteristics of the seizures, the EEG, brain MRI, ECoG, and histopathology. Seven PET/CT scans carried out on six patients showed well-defined hypermetabolic foci (three temporal, four extratemporal). There was a high correlation between the clinical lateralization, EEG/ECoG findings, and hypermetabolic foci located by PET. An MRI correctly identified the resected histopathological lesion in five cases and it was negative in two. Three patients had Focal Cortical Dysplasia (FCD), one had FCD with areas of polymicrogyria, one had temporal lobe cavernoma associated with hippocampal sclerosis, and one had a focal subcortical heterotopia. Mean postsurgical follow-up was 29.1 months (range: 16-24 months) and all patients were seizure free during this period. This small series of patients who underwent surgery for intractable focal epilepsy have shown good correlation between the ictal F18-FDG PET/CT scan and the electroclinical and pathological findings. These results suggest that hypermetabolic foci showed in PET/CT provides a reliable estimation of epileptogenic zone. Focus size underestimation in one case suggest the need of doing an interictal PET before surgery.

The utility of magnetoencephalography in the presurgical evaluation of refractory insular epilepsy

To study the utility of magnetoencephalography (MEG) in patients with refractory insular epilepsy. Covered by highly functional temporal, frontal, and parietal opercula, insular-onset seizures can manifest a variety of ictal symptoms falsely leading to a diagnosis of temporal, frontal, or parietal lobe seizures. Lack of recognition of insular seizures may be responsible for some epilepsy surgery failures. We retrospectively reviewed and analyzed MEG data in 14 patients with refractory insular seizures defined through intracranial electroencephalography (EEG) or by the presence of an epileptogenic lesion in the insula with compatible seizure semiology. MEG was performed as part of the noninvasive presurgical evaluation, using a 275-channel whole head MEG system. MEG data were analyzed using a single equivalent current dipole model. MEG localization was compared to interictal positron emission tomography (PET) and ictal single photon emission computed tomography (SPECT) results and to the resection margin. Three patterns of MEG spike sources were observed. Seven patients showed an anterior operculoinsular clusters and two patients had a posterior operculoinsular cluster. No spikes were detected in one patient, and the remaining four patients showed a diffuse perisylvian distribution. Spike sources showed uniform orientation perpendicular to the sylvian fissure. Nine patients proceeded to insular epilepsy surgery with favorable surgical outcome. Among patients with anterior operculoinsular cluster who proceeded to have surgery, MEG provided superior information to ictal SPECT in four of six patients and to interictal PET in five of six patients. MEG is useful in identifying patients who are likely to benefit from epilepsy surgery targeting the insula, particularly if a tight dipole cluster is identified even if other noninvasive modalities fail to produce localizing results.

FDG PET of the Brain in Pediatric Patients: Imaging Spectrum with MR Imaging Correlation

Positron emission tomography (PET) of the brain is an important problem-solving tool in pediatric neuroimaging, neurology, and neurosurgery. Fluorine 18 fluorodeoxyglucose (FDG) PET or dual-modality PET and computed tomographic (CT) imaging (PET/CT), with magnetic resonance (MR) imaging correlation, can be used to evaluate childhood epilepsy and pediatric brain tumors, areas in which PET adds value in patient management. FDG PET has been widely used in pediatric temporal lobe epilepsy, most commonly manifesting as mesial temporal sclerosis, which demonstrates hypometabolism at interictal PET and hypermetabolism during seizures. Recently, FDG PET has shown added value for patients with extratemporal epilepsy, in whom FDG PET can help identify cortical foci of interictal hypometabolism that are undetectable or difficult to detect with MR imaging. These findings can then guide additional investigations and surgery. FDG PET also enhances medical decision making in children with brain tumors, in whom FDG PET can be used to (a) improve the diagnostic yield of stereotactic biopsies by detecting metabolically active areas of tumor, (b) help guide the surgeon in achieving total tumor resection, and (c) increase detection of residual or recurrent tumor. Technologic advances in the past decade have allowed fusion of PET and MR images, combining the high resolution of MR imaging with the low-resolution functional capability of PET. As dual-modality integrated PET/MR imaging systems become available, CT coregistration for PET can be eliminated, thus reducing patient radiation exposure. Increasing familiarity with normal and abnormal appearances of FDG PET brain images correlated with MR images can enhance diagnostic yield and improve the care of children with epilepsy and brain tumors.

Altered brain metabolism in vestibular migraine: Comparison of interictal and ictal findings

Vestibular symptoms/signs frequently coexist with migraine, but the mechanisms of migraine-related vestibular dysfunction remain to be elucidated. This study aimed to determine altered brain metabolism in vestibular migraine. Two patients with vestibular migraine underwent (18)F-fluorodeoxy glucose (FDG) positron-emission tomography (PET) during and between attacks of vestibular migraine in addition to detailed neurotological evaluation. We analyzed the regional brain metabolism of the patients in comparison with that of age-matched healthy controls in each patient. We also compared ictal with interictal FDG PET using a subtraction method. During the attacks, both patients showed an activation of the bilateral cerebellum and frontal cortices, and deactivation of the bilateral posterior parietal and occipitotemporal areas. One patient also showed hypermetabolism in the dorsal pons and midbrain, right posterior insula, and right temporal cortex while the other patient had an additional activation of the left temporal cortex. Compared with interictal images, ictal PET showed increased metabolism in the bilateral cerebellum, frontal cortices, temporal cortex, posterior insula, and thalami. During the attacks of vestibular migraine, the increased metabolism in the temporo-parieto-insular areas and bilateral thalami indicates activation of the vestibulo-thalamo-cortical pathway, and decreased metabolism in the occipital cortex may represent reciprocal inhibition between the visual and vestibular systems.

Quantitative Analysis of Simultaneous EEG Features during PET Studies for Childhood Partial Epilepsy

PurposeTo demonstrate the significance of simultaneous electroencephalography (EEG) recording during 2-deoxy-2-[18F] fluoro-D-glucose (FDG)-positron emission tomography (PET) in childhood partial epilepsy.Materials and MethodsWe included 46 children with partial epilepsy who underwent simultaneous EEG during PET. We compared the epileptogenic area of several EEG features including epileptiform discharges, focal polymorphic slow waves, and electrographic seizures, with the abnormal metabolic region on PET. We also compared the epileptogenic area of simultaneous EEG and PET with findings on magnetic resonance imaging (MRI) and video/EEG, as well as the histopathological diagnosis of the resected cortical area, in eight patients who underwent surgical resection of the epileptogenic area.ResultsHypometabolic regions on interictal PET were concordant with epileptogenic areas of epileptiform discharges and focal polymorphic slow waves, according to their frequency and/or severity, with odds ratios of 1.35 and 1.81, respectively (p<0.05). Hypermetabolic PET was also concordant with epileptogenic areas of ictal events longer than 20 seconds during the period of FDG uptake. Among the eight patients who underwent surgical resection, six patients, including two with non-lesional MRI, had concordant EEG and PET findings, were confirmed pathologically, and became seizure-free after surgery.ConclusionSimultaneous EEG is useful in identifying epileptogenic areas due to a high concordance with abnormal PET metabolic areas. Moreover, simultaneous EEG may also prevent false lateralization of PET from postictal and mixed metabolism during ictal events, as well as abnormal hypermetabolism, during frequent interictal epileptiform discharges.

Interictal PET and ictal subtraction SPECT: Sensitivity in the detection of seizure foci in patients with medically intractable epilepsy

Interictal positron emission tomography (PET) and ictal subtraction single photon emission computed tomography (SPECT) of the brain have been shown to be valuable tests in the presurgical evaluation of epilepsy. To determine the relative utility of these methods in the localization of seizure foci, we compared interictal PET and ictal subtraction SPECT to subdural and depth electrode recordings in patients with medically intractable epilepsy. Between 2003 and 2009, clinical information on all patients at our institution undergoing intracranial electroencephalography (EEG) monitoring was charted in a prospectively recorded database. Patients who underwent preoperative interictal PET and ictal subtraction SPECT were selected from this database. Patient characteristics and the findings on preoperative interictal PET and ictal subtraction SPECT were analyzed. Sensitivity of detection of seizure foci for each modality, as compared to intracranial EEG monitoring, was calculated. Fifty-three patients underwent intracranial EEG monitoring with preoperative interictal PET and ictal subtraction SPECT scans. The average patient age was 32.7 years (median 32 years, range 1-60 years). Twenty-seven patients had findings of reduced metabolism on interictal PET scan, whereas all 53 patients studied demonstrated a region of relative hyperperfusion on ictal subtraction SPECT suggestive of an epileptogenic zone. Intracranial EEG monitoring identified a single seizure focus in 45 patients, with 39 eventually undergoing resective surgery. Of the 45 patients in whom a seizure focus was localized, PET scan identified the same region in 25 cases (56% sensitivity) and SPECT in 39 cases (87% sensitivity). Intracranial EEG was concordant with at least one study in 41 cases (91%) and both studies in 23 cases (51%). In 16 (80%) of 20 cases where PET did not correlate with intracranial EEG, the SPECT study was concordant. Conversely, PET and intracranial EEG were concordant in two (33%) of the six cases where the SPECT did not demonstrate the seizure focus outlined by intracranial EEG. Thirty-three patients had surgical resection and >2 years of follow-up, and 21 of these (64%) had Engel class 1 outcome. No significant effect of imaging concordance on seizure outcome was seen. Interictal PET and ictal subtraction SPECT studies can provide important information in the preoperative evaluation of medically intractable epilepsy. Of the two studies, ictal subtraction SPECT appears to be the more sensitive. When both studies are used together, however, they can provide complementary information.

Positron emission tomography plus VEEG in the localization of epileptic foci in negative-MRI interact epilepsy

To explore the application value of positron emission tomography (PET) in the localization of magnetic resonance imaging (MRI)-negative epileptogenic focus. Brain images of 18fluoro-2-deoxy-D-glucose (18F-FDG) and 13N-NH3·H2O-PET, MRI and video electroencephalography (VEEG) were obtained in 65 patients. Preoperative and postoperative localizations were compared in MRI-negative patients. And the results of PET and VEEG were compared between the MRI-positive and MRI-negative groups. MRI scans were normal in 26 cases and abnormal in 35 cases. Sixty-one patients had interictal epileptiform discharge on VEEG (brain regions, n = 12; multiple brain areas, n = 16; hemisphere, n = 13; unspecified location, n = 20) and interictal PET imaging (brain regions, n = 23; multiple brain areas, n = 28; hemisphere, n = 5; unspecified location, n = 6). And 17 MRI-negative patients underwent operations and 12 of them reached the Engels I-II level standard. Both PET and VEEG were compared between the MRI-positive and MRI-negative groups. No significant differences existed between two group (P < 0.05). A comparison of PET and VEEG showed statistical significance in two group (P > 0.05). PET imaging is both sensitive and effective in the detection and localization of epileptogenic foci. Especially for MRI-negative cases, it is an indispensable tool of localizing epileptogenic foci.

Temporo-spatial analyses define epileptogenic and functional zones in a case of Dyke–Davidoff–Masson syndrome

Dyke–Davidoff–Masson syndrome (DDMS) is a rare epilepsy syndrome that is characterized by cerebral hemiatrophy, homolateral skull hyperplasia, hyperpneumatization of the paranasal sinuses, seizures with or without mental retardation, and contralateral hemiparesis. We describe a case of DDMS in a 40-year-old female who had complex partial seizures with occasional secondary generalization since the age of 4 years. Her seizure frequency was 10–20 seizures/month even though she took four antiepileptic drugs. We applied magnetic resonance imaging (MRI), positron emission tomography (PET), functional MRI, and invasive electroencephalography (EEG) to define her epileptogenic and functional zones. Brain MRI showed prominent atrophy in the left frontal dorsal and lateral regions and mild atrophy of the left superior temporal gyrus and left parietal gyri. Interictal PET revealed decreased glucose metabolism in the atrophic regions. Functional MRI demonstrated that the inferior frontal and inferior parieto-occipital regions of the right hemisphere were activated by language testing. Invasive EEG revealed that the left lateral temporal lobe was the sole source of her seizures. Our results imply that the “metabolic border zone” rather than the atrophic region plays an important role in seizure activity, and that reorganization of functional zones occur after cerebral damage early in life.

Interictal arterial spin-labeling MRI perfusion in intractable epilepsy

Magnetic resonance imaging (MRI) is required for the investigation of surgically intractable epilepsy. In addition to the standard MRI techniques, perfusion sequences can be added to improve visualization of underlying pathological changes. Arterial spin-labeling (ASL) MRI perfusion does not require contrast administration and, for this reason, may have advantages in these patients. We report here on 16 patients with epilepsy who underwent MRI of the brain with ASL and positron emission tomography (PET). Despite a slightly reduced resolution with ASL, we found a correlation between ASL, PET and electrophysiological data, with hypoperfusion on ASL that corresponded with hypoperfusion on interictal PET. Given the correlation between ASL and PET and electrophysiology, perfusion with ASL could become part of the standard work-up in patients with epilepsy.

PET and SPECT in epilepsy: A critical review

Molecular imaging with ictal and interictal single-photon emission computed tomography (SPECT) as well as positron emission tomography (PET) rank among the established functional imaging tests for the presurgical evaluation of epileptic onset zone in patients with intractable partial epilepsy. In temporal lobe epilepsy the sensitivity of these methods was shown to be excellent, in particular if a multimodal platform is used, which combines the functional imaging with the additional morphological information of magnetic resonance imaging (MRI), but was lower in extra temporal lobe epilepsy. Functional imaging with SPECT and PET reflects seizure related changes of cerebral perfusion, glucose-metabolism and neuroreceptor status. In this review the usefulness of SPECT and PET imaging in clinical routine in epilepsy as well as the role of different neuroreceptor PET-tracer, which were used in epilepsy are discussed. The use of perfusion SPECT tracer allows the investigation of ictal activations, but the low temporal resolution of ictal perfusion SPECT often results in the detection of both the ictal onset zone as well as the propagation pathways, an area that has not always need to be resected in order to render a patient seizure free. The additional use of interictal PET with fluorine-18 fluorodeoxyglucose which measures regional cerebral metabolism or interictal perfusion SPECT enhance the informational value of ictal SPECT and were shown to be important tools to better define the ictal onset and surround inhibition zones. In recent years PET imaging of different cerebral neuroreceptor-systems inter alia GABA(A) receptors, serotonin receptors (5-HT(1A)), opioid receptors as well as dopamine receptors was used to investigate the neurochemical basis of epilepsy, the role of these neurotransmitters for the epileptogenesis as well as the spread of epileptic activity during seizures and partially entered in clinical routine. Currently some of these radioligands are also used to investigate new treatment approaches.