Distinct effects of the basal ganglia and cerebellum on the thalamocortical pathway in idiopathic generalized epilepsy.

The aberrant thalamocortical pathways of epilepsy have been detected recently, while its underlying effects on epilepsy are still not well understood. Exploring pathoglytic changes in two important thalamocortical pathways, that is, the basal ganglia (BG)-thalamocortical and the cerebellum-thalamocortical pathways, in people with idiopathic generalized epilepsy (IGE), could deepen our understanding on the pathological mechanism of this disease. These two pathways were reconstructed and investigated in this study by combining diffusion and functional MRI. Both pathways showed connectivity changes with the perception and cognition systems in patients. Consistent functional connectivity (FC) changes were observed mainly in perception regions, revealing the aberrant integration of sensorimotor and visual information in IGE. The pathway-specific FC alterations in high-order regions give neuroimaging evidence of the neural mechanisms of cognitive impairment and epileptic activities in IGE. Abnormal functional and structural integration of cerebellum, basal ganglia and thalamus could result in an imbalance of inhibition and excitability in brain systems of IGE. This study located the regulated cortical regions of BG and cerebellum which been affected in IGE, established possible links between the neuroimaging findings and epileptic symptoms, and enriched the understanding of the regulatory effects of BG and cerebellum on epilepsy.

Seizure outcome during bilateral, continuous, thalamic centromedian nuclei deep brain stimulation in patients with generalized epilepsy: a prospective, open-label study.

OBJECTIVE: We report on the seizure frequency and attention outcome during thalamic centromedian stimulation (CM-DBS) in patients with refractory generalized epilepsy (GE). METHODS: Twenty consecutive patients with GE who were submitted to CM-DBS and had at least one year of follow-up were prospectively studied. The CM was targeted bilaterally. Stimulation intensity was ramped up (bipolar, continuous, 130 Hz; 300µsec) until 4.5 V or until side effects developed. Contacts` position was determined on postoperative volumetric MRI scans. Attention was qualitatively evaluated using the SNAP-IV (Swanson, Nolan, and Pelham) questionnaire. Patients were considered responders during CM-DBS if an at least 50% seizure frequency reduction was obtained compared to baseline. RESULTS: Median age was 15.5 years (13 males). Median follow-up time was 2.55 years. EEG disclosed generalized spike-and wave discharges in all patients. MRI was normal in 10 patients, showed diffuse atrophy in 6 patients, and showed abnormalities in 4 patients (3 patients had bilateral cortical development abnormalities and one had unilateral hemispheric atrophy). Patients presented with daily multiple seizure types (8 to 66 per day; median: 37), including tonic, atonic, myoclonic, atypical absence and generalized tonic-clonic seizures. Mean DBS intensity was 4.3 V. An insertional effect was noted in 14 patients. CM-DBS was able to significantly reduce the frequency of tonic (p < 0.001), atypical absence seizures (p < 0.001), atonic seizures (p = 0.001) and bilateral generalized tonic-clonic seizures (p = 0.004). One patient became seizure-free. Ninety percent of the patients were considered responders (>50% seizure frequency reduction). All patients showed some improvement in attention. The mean number of items in which improvement was noted in the SNAP-IV questionnaire was 4.8. There was a significant relationship between overall seizure frequency reduction and improvement of attention (p = 0.033). DISCUSSION: This prospective, open label study included a large, homogeneous cohort and provided evidence on the efficacy of CM-DBS in reducing the seizure burden and increasing attention in patients with refractory generalized epilepsy.

Clinical features and outcome of Wilson's disease with generalized epilepsy in Chinese patients.

OBJECTIVE: Generalized epilepsy is rarely reported in patients with Wilson disease (WD) and lacks experience in clinical practice. We aim to provide better experience for the diagnosis and treatment for WD patients with epilepsy in the future. METHODS: A retrospective study was performed in 13 Chinese WD patients with generalized epilepsy. Each patient was diagnosed with WD by clinical evaluation and genetic screening. Patients were given small doses of antiepileptic drugs (AEDs), followed by copper-chelation therapy when the seizures stabilized. Clinical manifestations, brain imaging changes, and treatment and outcome after a long-term follow-up were analyzed. RESULTS: Four out of 13 (30.8%) patients stopped taking copper-chelation drugs for more than 1 year before they were admitted for epilepsy. The incidence of epilepsy of WD patients in our cohort is 1.43% (13/910), lower than those (4.5%-5.9%) in other populations. After the attack of epilepsy, frontal lobes were the most common abnormalities (13/13, 100%) in patients, followed by brain stem (8/13, 61.5%) and thalamus (7/13, 53.8%). After a long-term follow-up, brain imaging and clinical manifestations of 8 (8/9, 88.9%) WD patients were significantly improved. CONCLUSIONS: We firstly described WD patients with generalized epilepsy in the Chinese population. WD patients with aggravation of neuropsychiatric symptoms are prone to occur epilepsy; thus, brain MRI should be performed regularly in those patients. Cortical abnormality in brain MRI is a warning sign of epilepsy. Irregular use of copper-chelation drugs and excessive copper deposition in the brain may be the cause of seizures. Long-term standardized treatment for WD can effectively prevent the extensive brain damage and reduce the incidence of epilepsy in WD patients.

Community-informed connectomics of the thalamocortical system in generalized epilepsy.

OBJECTIVE: To study the intrinsic organization of the thalamocortical circuitry in patients with generalized epilepsy with tonic-clonic seizures (GTCS) via resting-state fMRI (rs-fMRI) connectome analysis and to evaluate its relation to drug response. METHODS: In a prospectively followed-up sample of 41 patients and 27 healthy controls, we obtained rs-fMRI and structural MRI. After 1 year of follow-up, 27 patients were classified as seizure-free and 14 as drug-resistant. We examined connectivity within and between resting-state communities in cortical and thalamic subregions. In addition to comparing patients to controls, we examined associations with seizure control. We assessed reproducibility in an independent cohort of 21 patients. RESULTS: Compared to controls, patients showed a more constrained network embedding of the thalamus, while frontocentral neocortical regions expressed increased functional diversity. Findings remained significant after regressing out thalamic volume and cortical thickness, suggesting independence from structural alterations. We observed more marked network imbalances in drug-resistant compared to seizure-free patients. Findings were similar in the reproducibility dataset. CONCLUSIONS: Our findings suggest a pathoconnectomic mechanism of generalized epilepsy centered on diverging changes in cortical and thalamic connectivity. More restricted thalamic connectivity could reflect the tendency to engage in recursive thalamocortical loops, which may contribute to hyperexcitability. Conversely, increased connectional diversity of frontocentral networks may relay abnormal activity to an extended bilateral territory. Network imbalances were observed shortly after diagnosis and related to future drug response, suggesting clinical utility.

[Cerebral structural changes in generalized idiopathic epilepsy identified by automated magnetic resonance imaging analysis]. / Cambios estructurales cerebrales en epilepsia generalizada idiopática identificados por análisis de imágenes de resonancia magnética automatizados.

The purpose of this study was to combine two automated methods of magnetic resonance imaging (MRI) structural analysis in order to identify structural changes in patients born in Argentina with idiopathic generalized epilepsy (IGE) compared to a healthy adult control group. Twenty-eight patients with IGE and 26 controls with no significant demographic differences were included. The analysis of the brain structures was conducted with two automated methods of magnetic resonance image analysis: voxelbased morphometry and FSL-integrated registration and segmentation toolbox (FSL-FIRST). FSL showed volume decrease in both thalamus in patients with IGE compared to the control group (left: 8092 mm3 control group vs. 7424 mm3 IGE, p = 0.0015; right: 7951 mm3 control group vs. 7247 mm3 IGE, p = 0.0016). A reduction in the volume of both caudate nuclei was also seen (left: 3612 mm3 control group vs. 3376 mm3 IGE, p = 0.01; right: 3683 mm3 control group vs. 3459 mm3 IGE, p = 0.04). Voxel-based-morphometry showed a volume decrease in both caudate nuclei in patients with IGE compared to the control group. The other cerebral structures analyzed did not show significant differences between the groups. In conclusion, this study shows the reduction in volume in the subcortical, thalamic, and caudate nuclei structures in patients with IGE in comparison to control group. This study conducted in our country delves into the analysis of brain structural changes in patients with EGI compared to healthy subjects.

El objetivo de este estudio fue combinar dos métodos automatizados de análisis estructural de imágenes de resonancia magnética para identificar cambios estructurales en pacientes nacidos en Argentina con epilepsia generalizada idiopática (EGI) en comparación con un grupo control de adultos sanos. Fueron incluidos 28 pacientes con EGI y 26 controles sin diferencias demográficas significativas. El análisis de las estructuras cerebrales se realizó con dos métodos automatizados de análisis de imágenes de resonancia magnética: la morfometría basada en vóxel y con la herramienta de segmentación y registro integrada FSL (FSL-FIRST). FSL mostró una disminución del volumen en ambos tálamos en EGI en comparación con el grupo control (tálamo izquierdo: 8092 mm3 grupo control vs. 7424 mm3 EGI, p = 0.0015; tálamo derecho: 7951 mm3 grupo control vs. 7247 mm3 EGI, p = 0.0016). Se observó una reducción en el volumen de ambos núcleos caudados (izquierdo: 3612 mm3 grupo control vs. 3376 mm3 EGI, p = 0.01; derecho 3683 mm3 grupo control vs. 3459 mm3 EGI, p = 0.04). La morfometría basada en vóxel mostró una disminución del volumen en ambos núcleos caudados en EGI en comparación con el grupo control. Las otras estructuras cerebrales analizadas no mostraron diferencias significativas entre los grupos. Este estudio muestra la reducción en el volumen en las estructuras subcortical, tálamos y núcleos caudados en pacientes con EGI comparado con un grupo control.

Cambios estructurales cerebrales en epilepsia generalizada idiopática identificados por análisis de imágenes de resonancia magnética automatizados / Cerebral structural changes in generalized idiopathic epilepsy identified by automated magnetic resonance imaging analysis

El objetivo de este estudio fue combinar dos métodos automatizados de análisis estructural de imágenes de resonancia magnética para identificar cambios estructurales en pacientes nacidos en Argentina con epilepsia generalizada idiopática (EGI) en comparación con un grupo control de adultos sanos. Fueron incluidos 28 pacientes con EGI y 26 controles sin diferencias demográficas significativas. El análisis de las estructuras cerebrales se realizó con dos métodos automatizados de análisis de imágenes de resonancia magnética: la morfometría basada en vóxel y con la herramienta de segmentación y registro integrada FSL (FSL-FIRST). FSL mostró una disminución del volumen en ambos tálamos en EGI en comparación con el grupo control (tálamo izquierdo: 8092 mm³ grupo control vs. 7424 mm³ EGI, p = 0.0015; tálamo derecho: 7951 mm³ grupo control vs. 7247 mm³ EGI, p = 0.0016). Se observó una reducción en el volumen de ambos núcleos caudados (izquierdo: 3612 mm³ grupo control vs. 3376 mm³ EGI, p = 0.01; derecho 3683 mm³ grupo control vs. 3459 mm³ EGI, p = 0.04). La morfometría basada en vóxel mostró una disminución del volumen en ambos núcleos caudados en EGI en comparación con el grupo control. Las otras estructuras cerebrales analizadas no mostraron diferencias significativas entre los grupos. Este estudio muestra la reducción en el volumen en las estructuras subcortical, tálamos y núcleos caudados en pacientes con EGI comparado con un grupo control.

The purpose of this study was to combine two automated methods of magnetic resonance imaging (MRI) structural analysis in order to identify structural changes in patients born in Argentina with idiopathic generalized epilepsy (IGE) compared to a healthy adult control group. Twenty-eight patients with IGE and 26 controls with no significant demographic differences were included. The analysis of the brain structures was conducted with two automated methods of magnetic resonance image analysis: voxel-based morphometry and FSL-integrated registration and segmentation toolbox (FSL-FIRST). FSL showed volume decrease in both thalamus in patients with IGE compared to the control group (left: 8092 mm³ control group vs. 7424 mm³ IGE, p = 0.0015; right: 7951 mm³ control group vs. 7247 mm³ IGE, p = 0.0016). A reduction in the volume of both caudate nuclei was also seen (left: 3612 mm³ control group vs. 3376 mm³ IGE, p = 0.01; right: 3683 mm³ control group vs. 3459 mm³ IGE, p = 0.04). Voxel-based-morphometry showed a volume decrease in both caudate nuclei in patients with IGE compared to the control group. The other cerebral structures analyzed did not show significant differences between the groups. In conclusion, this study shows the reduction in volume in the subcortical, thalamic, and caudate nuclei structures in patients with IGE in comparison to control group. This study conducted in our country delves into the analysis of brain structural changes in patients with EGI compared to healthy subjects.

Hypoxemia following generalized convulsive seizures: Risk factors and effect of oxygen therapy.

OBJECTIVE: To analyze the factors that determine the occurrence or severity of postictal hypoxemia in the immediate aftermath of a generalized convulsive seizure (GCS). METHODS: We reviewed the video-EEG recordings of 1,006 patients with drug-resistant focal epilepsy included in the REPO2MSE study to identify those with ≥1 GCS and pulse oximetry (SpO2) measurement. Factors determining recovery of SpO2 ≥ 90% were investigated using Cox proportional hazards models. Association between SpO2 nadir and person- or seizure-specific variables was analyzed after correction for individual effects and the varying number of seizures. RESULTS: A total of 107 GCS in 73 patients were analyzed. A transient hypoxemia was observed in 92 GCS (86%). Rate of GCS with SpO2 <70% dropped from 40% to 21% when oxygen was administered early (p = 0.046). Early recovery of SpO2 ≥90% was associated with early administration of oxygen (p = 0.004), absence of postictal generalized EEG suppression (PGES) (p = 0.014), and extratemporal lobe epilepsy (p = 0.001). Lack of early administration of O2 (p = 0.003), occurrence of PGES (p = 0.018), and occurrence of ictal hypoxemia during the focal phase (p = 0.022) were associated with lower SpO2 nadir. CONCLUSION: Postictal hypoxemia was observed in the immediate aftermath of nearly all GCS but administration of oxygen had a strong preventive effect. Severity of postictal hypoxemia was greater in temporal lobe epilepsy and when hypoxemia was already observed before the onset of secondary GCS.

Thalamic volume reduction in drug-naive patients with new-onset genetic generalized epilepsy.

OBJECTIVE: Patients with genetic generalized epilepsy (GGE) have subtle morphologic abnormalities of the brain revealed with magnetic resonance imaging (MRI), particularly in the thalamus. However, it is unclear whether morphologic abnormalities of the brain in GGE are a consequence of repeated seizures over the duration of the disease, or are a consequence of treatment with antiepileptic drugs (AEDs), or are independent of these factors. Therefore, we measured brain morphometry in a cohort of AED-naive patients with GGE at disease onset. We hypothesize that drug-naive patients at disease onset have gray matter changes compared to age-matched healthy controls. METHODS: We performed quantitative measures of gray matter volume in the thalamus, putamen, caudate, pallidum, hippocampus, precuneus, prefrontal cortex, precentral cortex, and cingulate in 29 AED-naive patients with new-onset GGE and compared them to 32 age-matched healthy controls. We subsequently compared the shape of any brain structures found to differ in gray matter volume between the groups. RESULTS: The thalamus was the only structure to show reduced gray matter volume in AED-naive patients with new-onset GGE compared to healthy controls. Shape analysis revealed that the thalamus showed deflation, which was not uniformly distributed, but particularly affected a circumferential strip involving anterior, superior, posterior, and inferior regions with sparing of medial and lateral regions. SIGNIFICANCE: Structural abnormalities in the thalamus are present at the initial onset of GGE in AED-naive patients, suggesting that thalamic structural abnormality is an intrinsic feature of GGE and not a consequence of AEDs or disease duration.

Sleep onset uncovers thalamic abnormalities in patients with idiopathic generalised epilepsy.

The thalamus is crucial for sleep regulation and the pathophysiology of idiopathic generalised epilepsy (IGE), and may serve as the underlying basis for the links between the two. We investigated this using EEG-fMRI and a specific emphasis on the role and functional connectivity (FC) of the thalamus. We defined three types of thalamic FC: thalamocortical, inter-hemispheric thalamic, and intra-hemispheric thalamic. Patients and controls differed in all three measures, and during wakefulness and sleep, indicating disorder-dependent and state-dependent modification of thalamic FC. Inter-hemispheric thalamic FC differed between patients and controls in somatosensory regions during wakefulness, and occipital regions during sleep. Intra-hemispheric thalamic FC was significantly higher in patients than controls following sleep onset, and disorder-dependent alterations to FC were seen in several thalamic regions always involving somatomotor and occipital regions. As interactions between thalamic sub-regions are indirect and mediated by the inhibitory thalamic reticular nucleus (TRN), the results suggest abnormal TRN function in patients with IGE, with a regional distribution which could suggest a link with the thalamocortical networks involved in the generation of alpha rhythms. Intra-thalamic FC could be a more widely applicable marker beyond patients with IGE.

Thalamic hypoperfusion and disrupted cerebral blood flow networks in idiopathic generalized epilepsy: Arterial spin labeling and graph theoretical analysis.

PURPOSE: The aim of this study was to investigate interictal cerebral blood flow (CBF) distributions and graph theoretical networks in idiopathic generalized epilepsy (IGE) using arterial spin labeling (ASL) imaging and anatomical covariance methods of graph theoretical analysis. MATERIAL AND METHODS: We recruited 19 patients with IGE and 19 age-/gender-matched healthy controls. Their CBF images were obtained by pseudo-continuous ASL imaging and compared using statistical parametric mapping 8 software (SPM8) and Graph Analysis Toolbox (GAT). RESULTS: The ASL imaging could detect interictal hypoperfusion in the thalamus, upper midbrain, and left cerebellum in IGE. Additionally, the graph theoretical analyses revealed characteristic findings of the CBF network of IGE, including significantly reduced resilience to attacks and changes of regional clustering especially in the bilateral temporo-occipital areas and lateral frontal lobes. There was no significance in the comparisons of network metrics. CONCLUSION: These findings could contribute to a better understanding of the pathophysiology of IGE.

Effects of Marijuana on Ictal and Interictal EEG Activities in Idiopathic Generalized Epilepsy.

Marijuana-based treatment for refractory epilepsy shows promise in surveys, case series, and clinical trials. However, literature on their EEG effects is sparse. Our objective is to analyze the effect of marijuana on EEG in a 24-year-old patient with idiopathic generalized epilepsy treated with cannabis. We blindly reviewed 3 long-term EEGs-a 24-hour study while only on antiepileptic drugs, a 72-hour EEG with Cannabis indica smoked on days 1 and 3 in addition to antiepileptic drugs, and a 48-hour EEG with combination C indica/sativa smoked on day 1 plus antiepileptic drugs. Generalized spike-wave discharges and diffuse paroxysmal fast activity were categorized as interictal and ictal, based on duration of less than 10 seconds or greater, respectively. Data from three studies concatenated into contiguous time series, with usage of marijuana modeled as time-dependent discrete variable while interictal and ictal events constituted dependent variables. Analysis of variance as initial test for significance followed by time series analysis using Generalized Autoregressive Conditional Heteroscedasticity model was performed. Statistical significance for lower interictal events (analysis of variance P = 0.001) was seen during C indica use, but not for C indica/sativa mixture (P = 0.629) or ictal events (P = 0.087). However, time series analysis revealed a significant inverse correlation between marijuana use, with interictal (P < 0.0004) and ictal (P = 0.002) event rates. Using a novel approach to EEG data, we demonstrate a decrease in interictal and ictal electrographic events during marijuana use. Larger samples of patients and EEG, with standardized cannabinoid formulation and dosing, are needed to validate our findings.

Altered structural and functional thalamocortical networks in secondarily generalized extratemporal lobe seizures.

Structural and functional abnormalities in the thalamocortical network in primary generalized epilepsies or mesial temporal lobe epilepsy have recently been identified by voxel-wise analyses of neuroimaging. However, evidence is needed regarding the profiles of the thalamocortical network in patients with secondarily generalized seizures from focal neocortical sources. We used high-resolution T1-weighted, diffusion-tensor and resting-state functional MR imaging (rs-fMRI) to examine 16 patients with secondarily generalized extratemporal lobe seizures and 16 healthy controls. All the patients were medically effective and MRI-negative. Using whole brain voxel-based morphometry (VBM) to compare the patients with the normal controls, we observed significantly decreased gray matter (GM) density in the thalamus and 3 frontal gyri and significantly reduced white matter (WM) fractional anisotropy (FA) in the bilateral anterior corona radiata of the patients. Alterations in the thalamocortical functional connectivity with different cortices were identified by the rs-fMRI analysis seeding of the whole thalamus. The prefrontal gyri with the greatest functional connectivity were also traced by seeding a sub-thalamic region that is demarcated in an atlas, in which the thalamic parcellation is based on the WM connectivity to the cortices. This sub-thalamic region anatomically contains the mediodorsal thalamic nucleus where, concordantly, there was a significant decrease in thalamic GM density in the VBM study. In contrast to the negative correlation between the disease duration and reduced thalamic densities and subcortical FA values, the strength of the functional thalamocortical connectivity had a paradoxical correlation. Our results conclusively indicate that generalized seizures with a focal cortical source are associated with structural and functional alterations in the thalamocortical network.

Generalized tonic-clonic seizures in a thalassemic patient with hypoparathyroidism and brain calcinosis.

Acquired hypoparathyroidism (HPT) is a not uncommon complication in patients with b-thalassemia major. The insufficient production of parathyroid hormone is mainly due to iron overload in parathyroid glands. We report a 22-year-old female thalassemic patient referred to our Unit for hypogonadism. During the previous two years she had presented with tonic-clonic seizures. After the second episode the patient was treated with phenytoin and valproate. Laboratory investigations were compatible with a diagnosis of HPT. A computed tomography scan of the head showed diffuse cerebral calcifications in the basal ganglia, frontal subcortical white matter, lentiform nucleus and cerebellum. After treatment with oral calcium supplementation and calcitriol she did not experience any further seizures. In addition, we present a brief review of the literature and report the Authors' recommendations.

Imaging onset and propagation of ECT-induced seizures.

PURPOSE: Regions of seizure onset and propagation in human generalized tonic-clonic seizures are not well understood. Cerebral blood flow (CBF) measurements with single photon emission computed tomography (SPECT) during electroconvulsive therapy (ECT)-induced seizures provide a unique opportunity to investigate seizure onset and propagation under controlled conditions. METHODS: ECT stimulation induces a typical generalized tonic-clonic seizure, resembling spontaneous generalized seizures in both clinical and electroencephalogram (EEG) manifestations. Patients were divided into two groups based on timing of ictal (during seizure) SPECT tracer injections: 0 s after ECT stimulation (early group), and 30 s after ECT (late group). Statistical parametric mapping (SPM) was used to determine regions of significant CBF changes between ictal and interictal scans on a voxel-by-voxel basis. RESULTS: In the early injection group, we saw increases near the regions of the bitemporal stimulating electrodes as well as some thalamic and basal ganglia activation. With late injections, we observed increases mainly in the parietal and occipital lobes, regions that were quiescent 30 s prior. Significant decreases occurred only at the later injection time, and these were localized to the bilateral cingulate gyrus and left dorsolateral frontal cortex. CONCLUSIONS: Activations in distinct regions at the two time points, as well as sparing of intermediary brain structures, suggest that ECT-induced seizures propagate from the site of initiation to other specific brain regions. Further work will be needed to determine if this propagation occurs through cortical-cortical or cortico-thalamo-cortical networks. A better understanding of seizure propagation mechanisms may lead to improved treatments aimed at preventing seizure generalization.

Positron emission tomography in epileptogenic hypothalamic hamartomas.

Whether the intrinsic epileptogenicity of hypothalamic hamartomas (HH) is responsible for the entire clinical spectrum of epileptic, neuropsychological and behavioural disorders associated with HH, remains an open issue, in as much as morphologically similar HH can be associated with dramatically different seizure types and cognitive outcomes. The aim of this study was to investigate brain glucose metabolism in patients with epileptogenic HH, in an attempt to identify signs of focal cortical and subcortical dysfunction which might correlate with other clinical data. We have studied five patients with epileptogenic HH using [18F]-fluoro-desoxyglucose and positron emission tomography (FDG-PET). All our patients also underwent an optimal MRI and a video-EEG monitoring, as well as an intra-cranial EEG recording in one of them. The anatomical distribution of FDG-PET abnormalities was compared to that of interictal and ictal electroclinical findings. All five patients demonstrated focal hypometabolism, ipsilateral to the predominant EEG abnormalities and side of HH. Hypometabolic areas greatly varied between patients, but were grossly concordant with the cortical regions suspected to participate in the ictal discharges in each individual. Epileptogenic hypothalamic hamartomas are usually associated with focal cortical hypometabolism in regions which might participate in the overall HH-driven epileptic network. Whether these cortical abnormalities only reflect the propagation of ictal discharges, or a potentially independent seizure onset zone remains unknown.

Centromedian-thalamic and hippocampal electrical stimulation for the control of intractable epileptic seizures.

The following two different modulatory procedures to control intractable epileptic seizures are presented: (1) chronic electrical stimulation of the centromedian-thalamic nucleus (ESCM) for control of generalized tonic-clonic seizures and atypical absences, and (2) subacute hippocampal stimulation (SAHCS) and chronic hippocampal stimulation for control of nonlesional temporal lobe seizures. The ESCM antiepileptic effect seems to be the result of activation of a nonspecific reticulothalamocortical system responsible for generalized electrocortical responses (recruiting, desynchronization, negative direct current shifts, and three spike-wave complexes per second). The success of the ESCM procedure depends on the following predictor factors: case selection (primary and secondary tonic-clonic seizures and atypical absences of the Lennox Gastaut syndrome), ventriculographic and electrophysiologic definition of the optimal stereotactic targets (based on the anterior commissure, posterior commissure, and the vertical line perpendicular to the posterior commissure and electrocortical recruiting responses), periodic electrophysiologic monitoring of the reliability of ESCM in the absence of the patient's subjective sensations and with totally internalized subcutaneous stimulation systems (by recording scalp electrocortical recruiting, desynchronizing, and direct current responses), quantitative evaluation of clinical and EEG improvement, and analysis of the ON and OFF effects, taking into account a long-lasting (possibly plastic) effect of ESCM. SAHCS blocks clinical and EEG signs of temporal lobe epileptogenesis with no additional damage of the stimulated hippocampal tissue. Preliminary results suggest that this antiepileptic effect is, at least in part, the result of a physiologic inhibition of the stimulated hippocampal tissue, because after SAHCS the authors found the following: (1) increased threshold and decreased duration, propagation, and blockage of the clinical signs accompanied with the hippocampal afterdischarge; (2) flattening of the hippocampal-evoked response recovery cycles; (3) single photon emission computed tomographic hypoperfusion; and (4) increased concentration of benzodiazepine receptor binding at the stimulated hippocampal region. Chronic hippocampal stimulation persistently blocked temporal lobe epileptogenesis in one patient under open protocols during 24 months with no apparent additional alterations in recent memory.

Central benzodiazepine/gamma-aminobutyric acid A receptors in idiopathic generalized epilepsy: an [11C]flumazenil positron emission tomography study.

PURPOSE: Previous [11C]flumazenil (FMZ) positron emission tomography (PET) investigations in patients with idiopathic generalized epilepsy (IGE) have demonstrated nonsignificant global cortical decreases in central benzodiazepine gamma-aminobutyric acid A (GABA[A]) receptor (cBZR) binding or focal decreases in the thalamus and increases in the cerebellar nuclei with no changes in cerebral cortex. We previously reported lower [11C]FMZ binding in cerebral cortex of IGE patients treated with valproate (VPA) than in cerebral cortex of controls. We now report high-resolution three-dimensional [11C]FMZ PET studies in a larger number of subjects using an improved method to detect differences in cBZR between IGE patients and controls and a more powerful longitudinal design to determine the functional effect of VPA. METHODS: We compared parametric images of [11C]FMZ volume of distribution (FMZVD) in 10 IGE patients before and after addition of VPA and in 20 normal subjects. RESULTS: Mean FMZVD was significantly higher in the cerebral cortex (11%, p = 0.009), thalamus (14%, p = 0.018), and cerebellum (15%, p = 0.027) of the 10 IGE patients as compared with that of 20 normal controls. Using statistical parametric mapping, no significant areas of focal abnormality of FMZVD were detected. Addition of VPA was not associated with a significant change in mean FMZVD in any brain area. CONCLUSIONS: Our finding of increased FMZVD in IGE could reflect microdysgenesis or a state of cortical hyperexcitability. Our data suggest that short-term VPA therapy does not affect the number of available cBZR in patients with IGE.