Epilepsy in adults

Epilepsy is one of the most common serious brain conditions, affecting over 70 million people worldwide. Its incidence has a bimodal distribution with the highest risk in infants and older age groups. Progress in genomic technology is exposing the complex genetic architecture of the common types of epilepsy, and is driving a paradigm shift. Epilepsy is a symptom complex with multiple risk factors and a strong genetic predisposition rather than a condition with a single expression and cause. These advances have resulted in the new classification of epileptic seizures and epilepsies. A detailed clinical history and a reliable eyewitness account of a seizure are the cornerstones of the diagnosis. Ancillary investigations can help to determine cause and prognosis. Advances in brain imaging are helping to identify the structural and functional causes and consequences of the epilepsies. Comorbidities are increasingly recognised as important aetiological and prognostic markers. Antiseizure medication might suppress seizures in up to two-thirds of all individuals but do not alter long-term prognosis. Epilepsy surgery is the most effective way to achieve long-term seizure freedom in selected individuals with drug-resistant focal epilepsy, but it is probably not used enough. With improved understanding of the gradual development of epilepsy, epigenetic determinants, and pharmacogenomics comes the hope for better, disease-modifying, or even curative, pharmacological and non-pharmacological treatment strategies. Other developments are clinical implementation of seizure detection devices and new neuromodulation techniques, including responsive neural stimulation.

MRI-PET registration with automated algorithm

OBJECTIVE

We have previously reported an automated method for within-modality (e.g., PET-to-PET) image alignment. We now describe modifications to this method that allow for cross-modality registration of MRI and PET brain images obtained from a single subject.

METHODS

This method does not require fiducial markers and the user is not required to identify common structures on the two image sets. To align the images, the algorithm seeks to minimize the standard deviation of the PET pixel values that correspond to each MRI pixel value. The MR images must be edited to exclude nonbrain regions prior to using the algorithm.

RESULTS AND CONCLUSION

The method has been validated quantitatively using data from patients with stereotaxic fiducial markers rigidly fixed in the skull. Maximal three-dimensional errors of < 3 mm and mean three-dimensional errors of < 2 mm were measured. Computation time on a SPARCstation IPX varies from 3 to 9 min to align MR image sets with [18F]fluorodeoxyglucose PET images. The MR alignment with noisy H2(15)O PET images typically requires 20-30 min.

Abnormalities of gyration, heterotopias, tuberous sclerosis, focal cortical dysplasia, microdysgenesis, dysembryoplastic neuroepithelial tumour and dysgenesis of the archicortex in epilepsy. Clinical, EEG and neuroimaging features in 100 adult patients

Cerebral cortical dysgenesis (CD) is a heterogeneous disorder of cortical development and organization commonly associated with epilepsy, with a variety of subtypes. We reviewed the clinical, EEG and neuroimaging features in 100 adult patients with CD. There were 39 men and 61 women with a median age of 27 years (range 15-63 years). All patients were referred because of medically refractory epilepsy. Median age at seizure onset was 10 years (range 3 weeks to 39 years); in 30 patients, onset was in adulthood. The epilepsy was classified as generalized in 16 patients and localization-related in 84. Of the latter, the epileptic syndromes in decreasing frequency were frontal (32%), temporal (31%), parietal (14%) and occipital (7%). Only 15% of patients had a history of status epilepticus. Prenatal/perinatal problems were reported in 32 patients but these were severe in only four: exposure to drugs (three) and infection (one) during the first trimester. Delayed developmental milestones were seen in 10%, mental retardation in 9%, additional congenital abnormalities in 4% and neurological deficits in 14% of patients. Diagnosis of CD was based on neuroimaging in 70, pathology in four and both methods in the remaining 26. The following subcategories were identified: agyria/diffuse macrogyria (four patients), focal macrogyria (16), focal polymicrogyria (one), focal macrogyria/polymicrogyria associated with a cleft (11), minor gyral abnormalities (seven), subependymal grey matter heterotopia (20), bilateral subcortical laminar grey matter heterotopia (eight), tuberous sclerosis (five), focal cortical dysplasia/microdysgenesis (seven) and dysembryoplastic neuroepithelial tumours (DNT) (21). Sixty-eight percent of patients had normal CT and 19 out of 36 patients had normal previous conventional MRI. MRI-based hippocampal volume measurements in 47 patients revealed ratios (smaller: larger hippocampus) of < 0.90 in 16, 0.90-0.94 in 14 and > or = 0.95 in 17 patients. EEGs were normal in only five patients. Alpha rhythm was preserved in 78 patients, including one patient with bilateral posterior macrogyria. Localized polymorphic slow activity was present in 43 patients. Five of 68 patients with focal/unilateral CD had only bilateral independent/synchronous spiking and 14 out of 32 with diffuse/bilateral CD only focal/unilateral spiking. In 60 patients with nondiffuse CD or with abnormal gyration or DNT, the epileptiform abnormalities were less extensive than coextensive with the lesion in 28, more extensive than and overlapped the lesion in 18 and remote from the lesion in five; nine patients did not have epileptiform abnormalities. There was poor correlation between the epileptic syndromes and EEG abnormalities and the location/extent of CD as defined by MRI and pathology.(ABSTRACT TRUNCATED AT 400 WORDS)

Secondary epileptogenesis in man

It is difficult to prove the existence of secondary epileptogenesis in man. In the majority of cases of human focal epilepsy, where the cause is likely to be trauma, infection, or vascular disease, the occurrence of additional or new epileptogenic foci is usually attributed to multiple primary injuries (maturing at different rates), or to progressive disease. Cerebral tumor is the only common cause in which the probability of multiple primary lesions is vanishingly low. Therefore, a personally followed series of cases of cerebral tumor seen as epilepsy are reviewed in which clinical, electrophysiologic, and pharmacologic data are analyzed for evidence of secondary epileptogenesis. Such evidence was found in 34% of our tumor patients. It was possible to demonstrate, in humans, the three stages of secondary epileptogenesis previously documented in animals. A pharmacologic test is described that separates the reversible from the irreversible stage of secondary epileptogenesis and allows prediction of the results of surgical removal of the primary focus.

The relative contributions of MRI, SPECT, and PET imaging in epilepsy

Functional and structural neuroimaging techniques are increasingly indispensable in the evaluation of epileptic patients for localization of the epileptic area as well as for understanding pathophysiology, propagation, and neurochemical correlates of chronic epilepsy. Although interictal single photon emission computed tomography (SPECT) imaging of cerebral blood flow is only moderately sensitive, ictal SPECT markedly improves yield. Positron emission tomography (PET) imaging of interictal cerebral metabolism is more sensitive than measurement of blood flow in temporal lobe epilepsy. Furthermore, PET has greater spatial resolution and versatility in that multiple tracers can image various aspects of cerebral function. Interpretation of all types of functional imaging studies is difficult and requires knowledge of time of most recent seizure activity and structural correlates. Only magnetic resonance imaging (MRI) can image the structural changes associated with the underlying epileptic process, and quantitative evidence of hippocampal volume loss has been highly correlated with seizure onset in medial temporal structures. Improved resolution and interpretation have made quantitative MRI more sensitive in temporal lobe epilepsy, as judged by pathology. When judged by electroencephalography (EEG), ictal SPECT and interictal PET have the highest sensitivity and specificity for temporal lobe epilepsy; these neuroimaging techniques have lower sensitivity and higher specificity for extratemporal EEG abnormalities. Regardless of the presence of structural abnormalities, functional imaging by PET or SPECT provides complementary information. Ideally these techniques should be used and interpreted together to improve the localization and understanding of epileptic brain.

Rapid assessment of regional cerebral metabolic abnormalities in single subjects with quantitative and nonquantitative [18F]FDG PET: A clinical validation of statistical parametric mapping

The [18F]fluorodeoxyglucose ([18F]FDG) method for measuring brain metabolism has not the wide clinical application that one might expect, partly because of its high cost and the complexity of the quantification procedure, but also because of reporting techniques based on region of interest (ROI) analysis, which are time-consuming and not fully objective. In this paper we report a clinical validation of statistical parametric mapping (SPM) using rCMRglc (quantitative) and radioactivity distribution (nonquantitative) [18F]FDG PET data. We show that a 10-min noninteractive voxel-based SPM analysis on a standard workstation enables objective assessment, including localization in stereotactic space, of regional glucose consumption abnormalities, whose reliability can be assessed on statistical and clinical grounds. Clinical validity was established using a small series of patients with degenerative or developmental disorders, including probable Alzheimer's disease, progressive aphasia, multiple sclerosis, developmental specific language impairment, and epilepsy. Analysis of quantitative and nonquantitative data showed the same pattern of results, suggesting that, for clinical purposes, quantitation and invasive arterial cannulation can be avoided. This should facilitate a wider application of the technique and the extension of SPM clinical analysis to H215O PET or high resolution SPECT perfusion studies.

Quantitative relaxometry of the brain

The exquisite soft tissue contrast provided by magnetic resonance imaging arises principally from differences in the intrinsic relaxation properties, T1 and T2. Although the intricate relationships that link tissue microstructure and the longitudinal and transverse relaxation times remain to be firmly established, quantitative measurement of these parameters, also referred to as quantitative relaxometry, can be informative of disease-related tissue change, developmental plasticity, and other biological processes. Further, relaxometry studies potentially offer a more detailed characterization of tissue, compared with conventional qualitative or weighted imaging approaches.The purposes of this review were to briefly review the biophysical basis of relaxation, focusing specifically on the T1, T2, and T2* relaxation times, and to detail some of the more widely used and clinically feasible techniques for their in vivo measurement. We will focus on neuroimaging applications, although the methods described are equally well suited to cardiac, abdominal, and musculoskeletal imaging. Potential sources of error, and methods for their correction, are also touched on. Finally, the combination of relaxation time data with other complementary quantitative imaging data, including diffusion tensor imaging, is discussed, with the aim of more thoroughly characterizing brain tissue.

Imaging epileptogenic tubers in children with tuberous sclerosis complex using alpha-[11C]methyl-L-tryptophan positron emission tomography

Several reports have indicated that cortical resection is effective in alleviating intractable epilepsy in children with tuberous sclerosis complex (TSC). Because of the multitude of cortical lesions, however, identifying the epileptogenic tuber(s) is difficult and often requires invasive intracranial electroencephalographic (EEG) monitoring. As increased concentrations of serotonin and serotonin-immunoreactive processes have been reported in resected human epileptic cortex, we used alpha-[11C]methyl-L-tryptophan ([11C]AMT) positron emission tomography (PET) to test the hypothesis that serotonin synthesis is increased interictally in epileptogenic tubers in patients with TSC. Nine children with TSC and epilepsy, aged 1 to 9 years (mean, 4 years 1 month), were studied. All children underwent scalp video-EEG monitoring, PET scans of glucose metabolism and serotonin synthesis, and EEG monitoring during both PET studies. [11C]AMT scans were coregistered with magnetic resonance imaging and with glucose metabolism scans. Whereas glucose metabolism PET showed multifocal cortical hypometabolism corresponding to the locations of tubers in all 9 children, [11C]AMT uptake was increased in one tuber (n=3), two tubers (n=3), three tubers (n=1), and four tubers (n=1) in 8 of the 9 children. All other tubers showed decreased [11C]AMT uptake. Ictal EEG data available in 8 children showed seizure onset corresponding to foci of increased [11C]AMT uptake in 4 children (including 2 with intracranial EEG recordings). In 2 children, ictal EEG was nonlocalizing, and in 1 child there was discordance between the region of increased [11C]AMT uptake and the region of ictal onset on EEG. The only child whose [11C]AMT scan showed no regions of increased uptake had a left frontal seizure focus on EEG; however, at the time of his [11C]AMT PET scan, his seizures had come under control. [11C]AMT PET may be a powerful tool in differentiating between epileptogenic and nonepileptogenic tubers in patients with TSC.

Identification of neural oscillations and epileptiform changes in human brain organoids

Brain organoids represent a powerful tool for studying human neurological diseases, particularly those that affect brain growth and structure. However, many diseases manifest with clear evidence of physiological and network abnormality in the absence of anatomical changes, raising the question of whether organoids possess sufficient neural network complexity to model these conditions. Here, we explore the network-level functions of brain organoids using calcium sensor imaging and extracellular recording approaches that together reveal the existence of complex network dynamics reminiscent of intact brain preparations. We demonstrate highly abnormal and epileptiform-like activity in organoids derived from induced pluripotent stem cells from individuals with Rett syndrome, accompanied by transcriptomic differences revealed by single-cell analyses. We also rescue key physiological activities with an unconventional neuroregulatory drug, pifithrin-α. Together, these findings provide an essential foundation for the utilization of brain organoids to study intact and disordered human brain network formation and illustrate their utility in therapeutic discovery.

The current place of epilepsy surgery

PURPOSE OF REVIEW

Three randomized controlled trials demonstrate that surgical treatment is safe and effective for drug-resistant epilepsy (DRE), yet fewer than 1% of patients are referred for surgery. This is a review of recent trends in surgical referral for DRE, and advances in the field. Reasons for continued underutilization are discussed.

RECENT FINDINGS

Recent series indicate no increase in surgical referral for DRE over the past two decades. One study suggests that decreased referrals to major epilepsy centers can be accounted for by increased referrals to low-volume nonacademic hospitals where results are poorer, and complication rates higher. The increasing ability of high-resolution MRI to identify small neocortical lesions and an increase in pediatric surgeries, in part, explain a relative greater decrease in temporal lobe surgeries. Misconceptions continue to restrict referral. Consequently, advocacy for referral of all patients with DRE to epilepsy centers that offer specialized diagnosis and other alternative treatments, as well as psychosocial support, is recommended. Recent advances will continue to improve the safety and efficacy of surgical treatment and expand the types of patients who benefit from surgical intervention.

SUMMARY

Surgical treatment for epilepsy remains underutilized, in part because of persistent misconceptions. Rather than promote referral for surgery, it would be more appropriate to advocate that all patients with DRE deserve a consultation at a full-service epilepsy center that offers many options for eliminating or reducing disability.

Surgical treatment of extratemporal epilepsy: clinical, radiologic, and histopathologic findings in 60 patients

PURPOSE AND METHODS

The aim of this study was to analyze clinical, radiologic, and histopathologic findings in 60 consecutive patients with medically intractable extratemporal epilepsy who were operated on between November 1987 and May 1993.

RESULTS

Histologically, there were distinct structural abnormalities in 50 (83%) of the surgical specimens. Signal abnormalities on magnetic resonance imaging (MRI) were present in all patients with neoplastic lesions (n = 17) and in 94% of patients with nonneoplastic focal lesions (n = 32). Overall, structural abnormalities were detected by MRI in 47 (96%) of 49 patients with focal lesions. During a mean follow-up of 4 years, 30 (54%) patients remained completely seizure free, 11 (20%) had < or = 2 seizures per year, seven (12%) showed a seizure reduction of > or = 75%, and eight (14%) had < 75% reduction in seizure frequency. The fraction of seizure-free patients was 12 (80%) of 15 in patients with neoplastic lesions, 16 (52%) of 31 in patients with nonneoplastic focal lesions, and two (20%) of 10 for those without histopathologic abnormalities. The differences in seizure outcome between patients with and without focal lesions were statistically significant (p < 0.05), if seizure-free outcome was compared with persistent seizures.

CONCLUSIONS

Focal lesions and particularly neoplasms are associated with improved postoperative seizure control compared with patients without histopathologic abnormalities. We advise caution in considering surgery to treat extratemporal epilepsy in patients who have normal MRI scans, because the outcome with the approach described in this study is poor in such cases.

Localization of epileptic foci with postictal single photon emission computed tomography

Effective surgical treatment of patients with intractable complex partial seizures depends on accurate preoperative seizure focus localization. We evaluated seizure localization with interictal and immediate postictal single photon emission computed tomographic images of cerebral perfusion using technetium-99m-hexamethyl-propyleneamineoxime (99mTc-HMPAO) in comparison with conventional ictal electroencephalographic (EEG) localization. Thirty-two patients with intractable complex partial seizures were studied. The mean delay from seizure onset to injection was 6.3 +/- 5.3 (SD) minutes. Independent blinded observers assessed the scans for interictal hypoperfusion and postictal focal hyperperfusion. Interictal scans alone were unreliable, indicating the correct localization in 17 patients (53%) and an incorrect site in 3 (9%). When interictal and postictal scans were interpreted together, the focus was correctly localized in 23 patients (72%). There was 1 false-positive study, and 8 patients had inconclusive changes, including 2 with inconclusive depth EEG studies. Postictal hyperperfusion was predominantly mesial temporal and frequently associated with hypoperfusion of lateral temporal cortex. Secondarily generalized seizures tended to show focal hyperperfusion less often than complex partial seizures did (Fisher's exact test p = 0.09). Combined interictal and immediate postictal single photon emission computed tomography with 99mTc-HMPAO is a useful noninvasive technique for independent confirmation of electrographic seizure localization. It may provide a suitable alternative to the use of depth electrode studies for confirmation of surface EEG findings in many patients with complex partial seizures.

Corpus callosotomy for epilepsy. I. Seizure effects

Twenty-two patients were analyzed 2 or more years after corpus callosum section (9 partial, 13 total). Forty-one percent had class 1 outcome (elimination of secondarily generalized and complex partial seizures), 32% had class 2 outcome (elimination of secondarily generalized seizures), and 27% had class 3 outcome (no appreciable change). Total section was twice as effective in abolishing secondarily generalized seizures as was partial section (77% versus 35%). Statistically significant associations were seen between focal CT lesions and class 1 outcome, and between IQ less than 45 and class 2 or 3 outcome.

Temporal lobectomy for uncontrolled seizures: the role of positron emission tomography

We evaluated the role of positron emission tomography (PET) with [18F]deoxyglucose (FDG) (FDG-PET) for planning surgery in 53 patients who had temporal lobectomy for uncontrolled seizures at National Institutes of Health from 1981 to 1990. Investigators blinded to PET data used results of telemetered video-electroencephalographic ictal monitoring and other standard criteria to decide whether subdural electrodes (22 patients, i.e., the "invasive" group) should be implanted or surgery performed. PET scans were analyzed using a standard regional template. Mean lateral but not mesial temporal asymmetry was significantly higher in patients who became seizure free (p < 0.03). Patients with > or = 15% hypometabolism were significantly more likely to be seizure free in the entire study population and the invasive subgroup. Visual identification of hypometabolism was less accurate. When a clear temporal ictal surface electroencephalographic focus was present, FDG-PET provided less additional information. FDG-PET may be particularly valuable if the surface electroencephalographic scan is nonlocalizing. In addition to helping to identify the seizure focus, it may allow limitation of invasive electrode placement to those necessary for functional mapping. When PET is used to identify epileptic foci, quantitative measurements of asymmetry should be made.

Identification of early recurrence of primary central nervous system tumors by [18F]fluorodeoxyglucose positron emission tomography

As aggressive neurosurgery and adjuvant therapy have become standard care for most patients with primary central nervous system (CNS) tumors, limitations of posttreatment neuroimaging techniques have become more apparent. Interpretation of computed cranial tomography (CT) and magnetic resonance imaging (MRI) in patients with brain tumors is complicated by changes related to surgery, corticosteroids, radiation, and chemotherapy. We investigated the role of 18F-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (FDG-PET) in these difficult diagnostic situations by obtaining FDG-PET scans in 5 patients following temporal lobectomy for epilepsy, in 5 patients with recurrent anaplastic gliomas before and after corticosteroid therapy, and in 5 patients after the development of histologically confirmed radionecrosis. We also obtained postoperative FDG-PET scans in 32 consecutive patients undergoing initial resection of a primary brain tumor. Our results indicate that glucose uptake as detected by FDG-PET scanning with [18F]fluorodeoxyglucose is not increased in the postoperative period; is not affected by steroid therapy; and accurately predicts early recurrence of tumor, supplementing other predictors of tumor behavior, including extent of resection, histological diagnosis, and postoperative CT. Thus PET using [18F]fluorodeoxyglucose can contribute to the optimum management of patients with primary brain tumors.

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.

Patent foramen ovale, a possible cause of symptomatic migraine: a study of 74 patients with acute ischemic stroke

Recent studies reported an increased prevalence of patent foramen ovale (PFO) in patients with migraine with aura (MA+). To investigate the possible relationship between MA+ and paradoxical embolism, we studied the prevalence of both conditions. Investigation of PFO was undertaken in 74 consecutive patients presenting with an acute stroke of undetermined origin. The patients were questioned about MA+ or migraine without aura (MA-) according to the criteria of the International Headache Society. Follow-up was performed to investigate the evolution of MA+ and MA- according to different treatments of stroke. PFO was found in 44 of 74 patients, 16 of whom had MA+ (36%), compared to 4 (13%) MA+ patients without PFO (p = 0.03). Of 25 patients in whom the PFO was considered to play a causal role in the stroke, 13 (52%) had MA+, whereas only 3 (16%) of 19 patients in whom PFO was considered unrelated had MA+ (p = 0.014). Thirty-nine of the patients with MA+ and MA- were studied over a mean follow-up of 13 months. Seven of 15 patients with MA+ and PFO, treated either with surgical closure or anticoagulants, noticed complete disappearance of MA+ attacks. The prevalence of MA+ is high among stroke patients with PFO. In patients with a high presumption of paradoxical embolism, the proportion of MA+ is increased, and this suggests a possible role of this association in the occurrence of the cerebrovascular event. Forty-seven percent of patients with PFO and MA+ reported complete suppression of their aura attacks after surgical closure or anticoagulant treatment. This finding suggests that at least in some patients, MA+ attacks may be due to paradoxical embolism.

Preoperative evaluation for epilepsy surgery (Bonn Algorithm)

SUMMARY

Epilepsy surgery has been established as a successful treatment in patients with drug-resistant focal epilepsies. Different standardized surgical approaches were developed for resective or functional treatment. Successful surgical treatment, however, necessitates a careful presurgical evaluation. Although there are international standards for non invasive and invasive presurgical procedures most centers differ in their diagnostic strategy. This article gives a survey of the Bonn Epilepsy surgery program within which more than 1300 patients have been treated. After the method of patient selection different we describe tools of non invasive and invasive evaluation. This article serves only as a description of current practice in one center with a relatively large volume of cases. It presents just one opinion of a specific group within a wide spectrum of possible algorithms for presurgical evaluation that have briefly been outlined for 33 centers in Engels book [4].

Comparison of [11C]flumazenil and [18F]FDG as PET markers of epileptic foci

Recent PET results indicate that the benzodiazepine (BZ) receptor density measured with the BZ receptor antagonist [11C]flumazenil is reduced in human epileptic foci. The present study examines the applicability of this finding in the presurgical investigation of patients with intractable partial epilepsy. In eight patients, the PET measurements were performed after injection of the BZ receptor antagonist [11C]flumazenil and [2-18F]2-deoxy-2-fluoro-D-glucose ([18F]FDG)--a tracer for measurements of the rate of regional glucose metabolism. The focus localising ability of the two PET tracers was examined using extra--and intracranial EEG recordings as reference. The focus was first determined visually on the PET images obtained after a bolus injection of each of the PET tracers. Its anatomical localisation and spatial delimitation was then evaluated for each patient with a computerised anatomical brain atlas. [11C]flumazenil was found to be a more sensitive and accurate focus localiser than [18F]FDG. This observation was valid both for quantified and non-quantified images. In the preoperative diagnosis of epileptic foci, the PET measurements of BZ receptors may be a suitable and, in some cases, superior method to the generally used "[18F]FDG-PET" method.

Epileptic seizure detection in EEG signals using tunable-Q factor wavelet transform and bootstrap aggregating

BACKGROUND AND OBJECTIVE

Epileptic seizure detection is traditionally performed by expert clinicians based on visual observation of EEG signals. This process is time-consuming, burdensome, reliant on expensive human resources, and subject to error and bias. In epilepsy research, on the other hand, manual detection is unsuitable for handling large data-sets. A computerized seizure identification scheme can eradicate the aforementioned problems, aid clinicians, and benefit epilepsy research.

METHODS

In this work, a new automated epilepsy diagnosis scheme based on Tunable-Q factor wavelet transform (TQWT) and bootstrap aggregating (Bagging) using Electroencephalogram (EEG) signals is proposed. Until now, this is the first time spectral features in the TQWT domain in conjunction with Bagging are employed for epilepsy seizure identification to the best of the authors' knowledge. At first, we decompose the EEG signal segments into sub-bands using TQWT. We then extract various spectral features from the TQWT sub-bands. The suitability of spectral features in the TQWT domain is established through statistical measures and graphical analyses. Afterwards, Bagging is employed for epileptic seizure classification. The efficacy of Bagging in the proposed detection scheme is also studied in this research. The effects of various TQWT and Bagging parameters are investigated. The optimal choices of these parameters are also determined. The performance of the proposed scheme is studied using a publicly available benchmark EEG database for various classification cases that include inter-ictal (seizure-free interval), ictal (seizure) and healthy; seizure and non-seizure; ictal and inter-ictal; and seizure and healthy.

RESULTS

In comparison with the state-of-the-art algorithms, the performance of the proposed method is superior in terms of sensitivity, specificity, and accuracy.

CONCLUSION

The seizure detection method proposed herein therefore can alleviate the burden of medical professionals of analyzing a large bulk of data by visual inspection, speed-up epilepsy diagnosis and benefit epilepsy research.

The human action recognition system and its relationship to Broca's area: an fMRI study

Primate studies have identified populations of neurons that are capable of action recognition. These "mirror neurons" show spiking activity both when the monkey executes or observes a grasping movement. These neurons are located in the ventral premotor cortex, possibly the homologue of "Broca's area" in human. This led to the speculation that action recognition and language production share a common system [Trends Neurosci. 21 (1998), 188]. To test this hypothesis, we combined an action recognition with a language production (VERB) and a grasping movement task (MOVE) by using functional magnetic resonance imaging. Action recognition-related activation was observed in the left inferior frontal gyrus and on the border between the inferior frontal gyrus and precentral gyrus (defined as IFG/PG), the ventral occipitotemporal junction, the superior and inferior parietal cortex, and in the intraparietal sulcus in the left hemisphere. An overlap of activations due to the language production, movement execution, and action recognition was found in the parietal cortex, the left inferior frontal gyrus, and the IFG-PG border (IFG/PG). The activation peaks of action recognition and verb generation were always different in single subjects, but no consistent spatial relationship was detected, in accord with the hypothesis that action recognition and language production share a common functional architecture.

Ictal SPECT

The localizing value of ictal single-photon emission computed tomography (SPECT) performed with cerebral blood flow agents in patients with epilepsy is based on cerebral metabolic and perfusion coupling. Ictal hyperperfusion is used to localize the epileptogenic zone noninvasively, and is particularly useful in magnetic resonance (MR)-negative partial epilepsy and focal cortical dysplasias. Subtraction ictal SPECT coregistered with MRI (SISCOM) improves the localization of the area of hyperperfusion. Ictal SPECT should always be interpreted in the context of a full presurgical evaluation. Early ictal SPECT injections minimize the problem of seizure propagation and of nonlocalization due to an early switch from ictal hyperperfusion to postictal hypoperfusion during brief extratemporal seizures. The degree of thresholding of SISCOM images affects the sensitivity and specificity of ictal SPECT. Ictal hypoperfusion may reflect ictal inhibition or deactivation. Postictal and interictal SPECT studies are less useful to localize the ictal-onset zone. Statistical parametric mapping analysis of groups of selected ictal-interictal difference images has the potential to demonstrate the evolution of cortical, subcortical, and cerebellar perfusion changes during a particular seizure type, to study seizure-gating mechanisms, and to provide new insights into the pathophysiology of seizures.

Epileptic psychosis: an evaluation of PSE profiles

Data are presented on 24 patients with epilepsy and psychosis whose clinical presentation was rated using the Present State Examination (PSE). Seventeen had complex partial seizures and a diagnosis of temporal lobe epilepsy, seven had generalised epilepsy. An association between a CATEGO category of nuclear schizophrenia (NS) and a lesion of the left side was noted. No clear link between depressive symptoms and a right-sided focus was discovered. Affective disorders were noted in both groups of epileptic patients, although paranoid psychoses were commoner in the temporal lobe group. There was also a tendency for the latter to have more delusions of persecution, ideas of reference, and special features of depression. The group rated as NS appear less likely to show evidence of intellectual deterioration than the other psychotic patients; in addition, the interval between the onset of their epilepsy and the onset of their psychosis is shorter. Radiological assessment by CAT reveals few differences between groups, but the psychotic samples do show higher than expected values on a number of variables, in particular the bilateral septum-caudate distance and the size of the third and fourth ventricle.