High-frequency burst vagal nerve simulation therapy in a natural primate model of genetic generalized epilepsy.

PURPOSE: Since the approval of Vagal Nerve Stimulation (VNS) Therapy for medically refractory focal epilepsies in 1997, it has been also reported to be effective for a wide range of generalized seizures types and epilepsy syndromes. Instead of conventional VNS Therapy delivered at 20-30Hz signal frequencies, this study evaluates efficacy and tolerability of high-frequency burst VNS in a natural animal model for genetic generalized epilepsy (GGE), the epileptic baboon. METHODS: Two female baboons (B1 P.h. Hamadryas and B2 P.h. Anubis x Cynocephalus) were selected because of frequently witnessed generalized tonic-clonic seizures (GTCS) for VNS implantation. High-frequency burst VNS Therapy was initiated after a 4-5 week baseline; different VNS settings (0.25, 2 or 2.5mA, 300Hz, 4 vs 7 pulses, 0.5-2.5s interburst interval, and intermittent stimulation for 1-2 vs for 24h per day) were tested over the subsequent 19 weeks, which included a 4-6 week wash-out period. GTCS frequencies were quantified for each setting, while seizure duration and postictal recovery times were compared to baseline. Scalp EEG studies were performed at almost every setting, including intermittent light stimulation (ILS) to evaluate photosensitivity. Pre-ILS ictal and interictal discharge rates, as well as ILS responses were compared between trials. The Novel Object test was used to assess potential treatment effects on behavior. RESULTS: High-frequency burst VNS Therapy reduced GTCS frequencies at all treatment settings in both baboons, except when output currents were reduced (0.25mA) or intermittent stimulation was restricted (to 1-2h/day). Seizure duration and postictal recovery times were unchanged. Scalp EEG studies did not demonstrate treatment-related decrease of ictal or interictal epileptic discharges or photosensitivity, but continuous treatment for 120-180s during ILS appeared to reduce photoparoxysmal responses. High-frequency burst VNS Therapy was well-tolerated by both baboons, without cardiac or behavioral changes. Repetitive muscle contractions involving the neck and left shoulder girdle were observed intermittently, most commonly at 0.5 interburst intervals, but these were transient, resolving with a few cycles of stimulation and not noted in wakefulness. CONCLUSIONS: This preclinical pilot study demonstrates efficacy and tolerability of high-frequency burst VNS Therapy in the baboon model of GGE. The muscle contractions may be due to aberrant propagation of the stimulus along the vagal nerve or to the ansa cervicalis, but can be reduced by minimal adjustment of current output or stimulus duration.

Subdural electrode recording of generalized photoepileptic responses.

We evaluated the spatiotemporal distribution of photic driving (PDR), photoparoxysmal (PPR), and photoconvulsive (PCR) responses recorded by intracranial electrodes (ic-EEG) in a patient with generalized photosensitivity and right frontal lobe cortical dysplasia. Intermittent light stimulation (ILS) was performed thirteen times in nine days. Cortical responses to ILS recorded by ic-EEG were reviewed and classified as PDRs, PPRs, and PCRs. Photic driving responses were restricted to the occipital lobe at ILS frequencies below 9 Hz, spreading to the parietal and central regions at > 9 Hz. Photoparoxysmal responses commonly presented as focal, medial occipital, and parietal interictal epileptic discharges (IEDs), the latter propagating to the sensorimotor cortices. Generalized IEDs were also generated in the setting of PPRs. Photoconvulsive responses, characterized by repetitive bilateral upper extremity myoclonus sustained until the end of the stimulus, were associated with propagation of the medial parieto-occipital discharge to the primary sensorimotor and supplementary area cortices, while generalized myoclonic seizures were associated with a generalized spike-and-wave discharge with an interhemispheric posterior cingulate onset sparing the sensorimotor cortices. Both types of PCR could occur during the same stimulus. Regardless of the pathway, PCRs only occurred when PDRs involved the parietal cortices. While there may be more than one pathway underlying PCRs, parietal lobe association cortices appear to be critical to their generation.

Cortical sulcal areas in baboons (Papio hamadryas spp.) with generalized interictal epileptic discharges on scalp EEG.

Brain MRI studies in people with idiopathic generalized epilepsies demonstrate regional morphometric differences, though variable in magnitude and location. As the baboon provides an excellent electroclinical and neuroimaging model for photosensitive generalized epilepsy in humans, this study evaluated MRI volumetric and morphometric differences between baboons with interictal epileptic discharges (IEDs) on scalp EEG and baboons with normal EEG studies. Seventy-seven baboons underwent high-resolution brain MRI and scalp EEG studies. The scans were acquired using an 8-channel primate head coil (Siemens TRIO 3T scanner, Erlangen, Germany). After spatial normalization, sulcal measurements were obtained by object-based-morphology methods. One-hour scalp EEG studies were performed in animals sedated with ketamine. Thirty-eight (22F/16M) baboons had normal EEGs (IED-), while 39 (22F/17M) had generalized IEDs (IED+). The two groups were compared for age, total brain volume, and sulcal areas (Hotelling's Trace) as well as between-subjects comparison of 11 individual sulcal areas (averaged between left and right hemispheres). There were no differences between IED- and IED+ groups with respect to age or total brain (gray or white matter) volume, and multivariate tests demonstrated a marginally significant decrease of sulcal areas in IED+ baboons (p=0.075). Tests of between-subjects effects showed statistically significant decreases in the intraparietal (p=0.002), central (p=0.03) and cingulate sulci (p=0.02), and marginal decreases involving the lunate (p=0.07) and superior temporal sulci (p=0.08). Differences in sulcal areas in IED+ baboons may reflect global developmental abnormalities, while decreases of areas of specific sulci reflect anatomical markers for potential generators or cortical nodes of the networks underlying spontaneous seizures and photosensitivity in the baboon.

MR imaging volumetry of subcortical structures and cerebellar hemispheres in temporal lobe epilepsy.

BACKGROUND AND PURPOSE: There is mounting evidence of extratemporal volume changes associated with medically refractory temporal lobe epilepsy (TLE). This MR imaging study aimed to characterize volume changes in subcortical structures and cerebellar hemispheres with respect to lateralization of the seizure focus, onset and duration of epilepsy, and frequency of generalized tonic-clonic seizures (GTCS). METHODS: Amygdalar, hippocampal, thalamic, caudate head, and cerebellar volume measurements were obtained in the preoperative MR images of 40 patients with TLE (20 right, 20 left), who underwent temporal lobe resection with good outcome, and in 20 right-handed control participants. All 3D MR images were spatially aligned and normalized before measurements were obtained. Standardized volumes and right-to-left volume ratios (VRs) were compared between control participants and right and left TLE groups. Multiple regression analyses were performed to study the effects of epilepsy onset and duration and GTCS frequency on ipsilateral-to-contralateral VRs with respect to the resected seizure focus. RESULTS: Thalamic volumes were smaller bilaterally in patients with TLE. Hippocampal volumes were smaller ipsilateral to the seizure focus, but there was no significant volume loss involving the amygdala, caudate, or cerebellum. Hippocampal and amygdalar right-to-left VRs differed significantly between right and left TLE groups and controls, whereas thalamic right-to-left VRs differed only between the TLE groups. Thalamic ipsilateral-to-contralateral VRs were correlated positively with epilepsy onset and negatively with epilepsy duration. Caudate ipsilateral-to-contralateral VRs were positively, whereas amygdalar and cerebellar VRs were negatively, correlated with GTCS frequency. CONCLUSIONS: Unilateral amygdalar and bilateral thalamic volume loss, in the absence of caudate head atrophy, is likely to reflect seizure-induced injury due to TLE. Correlations of VRs affecting the amygdala, caudate, and cerebellum with GTCS frequency may also reflect injury or a prediposition for secondary generalization. Potential effects of complex partial seizures, febrile seizures, or antiepileptic medications on subcortical structures need to be evaluated in future studies.

Amygdalar and hippocampal volumetry in control participants: differences regarding handedness.

BACKGROUND AND PURPOSE: Amygdalar and hippocampal volume measurements indicate a right-greater-than-left asymmetry for right-handed normal participants in most studies. The purpose of this study was to compare amygdalar and hippocampal volume ratios between right- and left-handed participants. METHODS: Amygdalar and hippocampal volume measurements were performed in 34 (20 right-handed and 14 left-handed) normal participants. All participants completed a 10-item handedness questionnaire. The MR imaging sequence was a 3D T1-weighted gradient-echo acquisition of the whole brain (24/6 [TR/TE]; flip angle, 25 degrees). MR images were spatially normalized, and volumes were painted with a 1.0-mm(3) resolution cursor on an SGI workstation. RESULTS: In right-handed participants, the amygdala and hippocampus (P <.001 for both) were significantly larger on the right side than on the left. The left-handed group did not show a significant difference between right- and left-sided structures. Right-to-left volume ratios differed significantly between right- and left-handed participants for both amygdalar (P <.02) and hippocampal (P <.01) structures. Gender did not affect right-to-left amygdalar and hippocampal volume ratios in right- or left-handed participants. CONCLUSION: Handedness, but not gender, seems to affect right-to-left amygdalar and hippocampal volume ratios.

Symptomatic or cryptogenic partial epilepsy of childhood onset: fourteen-year follow-up.

This study reports on the seizure and psychosocial outcome of 29 patients with electroclinically well-defined childhood-onset symptomatogenic or cryptogenic partial epilepsy with complex partial seizures who were followed prospectively over 14 years. Many were refractory at the time of enrollment. At 14-year follow-up, we acquired information on seizure type and frequency, psychiatric history, substance abuse, criminal activity, in addition to educational, vocational, and marital status through chart reviews and/or structured telephone interviews. Sixteen patients were only treated medically. They were divided by their following responses to medications: eight patients with less than one seizure per month were in the medically responsive group and eight patients with at least one seizure per month constituted the medically refractory group. Thirteen patients underwent focal resection for medically refractory epilepsy. Medically refractory patients displayed worse educational, vocational, social, and behavioral outcomes than medically responsive patients. Behavioral abnormalities persisted or evolved in five medically refractory patients when they became seizure free. Other studies have indicated that patients with medically refractory complex partial seizures have poor psychosocial outcomes. Although behavioral problems can occur even when seizures are well controlled, their early detection and treatment may be essential to the improvement of psychosocial outcomes.

Epilepsy surgery in children with pervasive developmental disorder.

Pervasive developmental disorder (PDD) is occasionally associated with medically intractable complex partial seizures. The outcome of PDD was explored in three males and two females who underwent epilepsy surgery at 32 months to 8 years of age (mean = 4 years) after onset of epilepsy at 1 week to 21 months of age (mean = 11 months). Four children had temporal lobe resections (three right, one left; two for focal cortical dysplasia, and two for tumors), and one had a right temporoparieto-occipital resection (for focal cortical dysplasia). Each child underwent repeated evaluations by a pediatric neuropsychologist and psychiatrist. Fourteen to 47 months (mean = 23 months) after operation, one child with persistent seizures had moderate developmental and behavioral improvement, three children (two seizure free, one with rare staring spells) had mild developmental and behavioral improvement, and the remaining child (seizure free) experienced a worsening of her PDD. The four children with mild-to-moderate improvement in postoperative cognitive and behavioral development still demonstrated persistent delay. Cognitive gains were confirmed by neuropsychologic testing in the oldest patient but were not reflected in test results from the three younger children, who had more modest improvement. The child with worsening of her PDD had cognitive and emotional deterioration to babbling, echolalia, aggressiveness, decreased social interaction, and increased mouthing of objects beginning several months postoperatively. These results suggest that families should be counseled that PDD symptoms in children with focal epileptogenic lesions may or may not improve after epilepsy surgery, even if the surgery is successful with respect to seizure control.

Vasoactive substances produced by cultured rat brain endothelial cells.

The vasoactive substances synthesized by primary cultures of rat brain endothelial cells were investigated and compared to those from two, immortalized cell lines, RBE4 and GP8. The vasoactivity of endothelium-derived substances was measured on isolated canine coronary artery. Vascular tone was significantly decreased by both primary and GP8, but not by RBE4 cells. Indomethacin pretreatment of primary and GP8 cells turned vasorelaxation into contraction while N(omega)-nitro-L-arginine pretreatment decreased the vasorelaxation induced by primary, but not by GP8 cells. Eicosanoid production was determined after incubation with [14C]arachidonic acid. The predominant vasoactive eicosanoid was prostaglandin E2 in both primary and GP8 cells. RBE4 cells synthetized mainly prostaglandin E2 and thromboxane B2 and significantly less prostaglandin E2 than did either primary or GP8 cells. The capacity of cerebral endothelium to regulate vascular tone by production of dilator and constrictor substances can be preserved under certain circumstances in immortalized cell lines.

Hippocampal volumetry in children 6 years or younger: assessment of children with and without complex febrile seizures.

PURPOSE: To study the relationship of complex febrile seizures (CFS) in the evolution of mesial temporal sclerosis. METHODS: We studied five children 22-68 (mean 44) months old with MRI volumetry 2 days-46 months after their first CFS, and compared total hippocampal volumes and right to left hippocampal volume ratios to those of 11 controls, 15-83 (mean 55) months old, who had MRI for complaints which turned out to be neurologically insignificant. RESULTS: In control children, total hippocampal volumes increased linearly with age, while right to left hippocampal volume ratios tended to decrease with age. In children with CFS total hippocampal volumes tended to be smaller than in controls. Right to left ratios were greater than 1 in all five children with CFS compared to seven of 11 controls. Hippocampal asymmetry was noted in only one child, with the right to left volume ratio exceeding two standard deviations from the control mean. The MRI of this child also demonstrated a subarachnoid cyst in the left frontocentral region, ipsilateral to the smaller hippocampus. Visual inspection of the remaining patients revealed no definite structural cortical abnormalities. None of the children developed subsequent afebrile seizures during the brief follow-up period. CONCLUSIONS: Hippocampal volumetry in controls revealed a linear increase in total hippocampal volumes and a statistically nonsignificant trend toward reduced right larger than left hippocampal ratios between 17 and 83 months old. The tendency for smaller total hippocampal volumes and larger right to left hippocampal volume ratios in children with CFS compared to controls could suggest a developmental abnormality, injury during CFS, or be age-related. The significant hippocampal asymmetry in a single child with CFS suggests that age may not be a factor in every case. Further studies are needed to collect control data in young children as well as prospectively follow children with CFS with serial imaging to better understand the relationship between CFS and the evolution of hippocampal atrophy.

Expression of glutamate receptors on cultured cerebral endothelial cells.

Activation of glutamate receptors has been shown to mediate a large number of neuronal processes such as long-term potentiation and ischemic damage. In addition to neurons and glia, glutamate receptors may occur on cerebral endothelial cells (CECs). The aim of the present study was to determine which glutamate receptors are expressed in CECs and to demonstrate the functional presence of such channels. By using reverse transcriptase-polymerase chain reaction, we showed that primary cultures of rat CECs express N-methyl-D-aspartate (NMDA) receptors (NR1 subunit, which is necessary for the formation of functional NMDA receptors, and NR2A-C subunits), 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl-propionate (AMPA) receptors (GLUR1-4 subunits), and metabotropic receptors (mGLUR). Exposure of the cultures to 2 mM glutamate, a well-established mediator of ischemic damage, for 30 min increased significantly the phosphorylation of calcium/calmodulin-dependent protein kinase II even after 10- and 60-min recovery times. This effect could be prevented by the NMDA blocker MK-801. The presence of multiple glutamate receptor types may confer a finely tuned responsiveness of the cerebral endothelium to glutamate in physiological and pathological conditions.

Cerebral ischemia reperfusion-induced vasogenic brain edema formation in rats: effect of an intracellular histamine receptor antagonist.

Resuscitation in pediatric emergency and some neurological interventions may result in ischemia reperfusion-induced cerebral injuries. Histamine is one of the well established mediators of cerebral swelling and H1- and H2-receptor antagonists could prevent the development of ischemic brain edema. In the present study, time-dependent changes in the blood-brain barrier (BBB) permeability were investigated in the cerebral cortex of male Wistar rats 1, 2, 4, 8, and 16 h after the beginning of post-ischemic reperfusion. Cerebral ischemia-reperfusion evoked by the 4-vessel occlusion model resulted in significant (p < 0.05) elevations in BBB permeability for albumin, but not for sodium fluorescein. Pre-treatment with a new intracellular histamine receptor antagonist could not prevent ischemic brain edema formation in that model. We conclude that experimental studies could help us to reveal the therapeutic role of histamine receptor antagonists during ischemic brain edema.

Expression of G-protein subtypes in cultured cerebral endothelial cells.

This paper describes Western-blotting evidence for the presence of various guanine nucleotide binding proteins, G-proteins in cultured rat cerebral endothelial cells (CECs) and two immortalized cerebral endothelial cell lines, RBE4 and GP8. By using specific antibodies raised against known sequences of appropriate G-protein types that were previously characterized, we demonstrated the presence of Gsalpha, Gi2alpha, Gi3alpha, Gq/11alpha, Goalpha and Gbeta in cell lysates of primary cultures of CECs, and plasma membranes of RBE4 and GP8 cells. The appearance of Goalpha proteins in CECs might be of special importance, since they were not detected in peripheral endothelial cells in previous studies. Isoproterenol and bradykinin displayed significant, dose-dependent stimulation of [35S]GTPgammaS binding above basal values. This assay, reflecting the GDP-GTP exchange reaction on Galpha-subunits by receptor agonists, suggested that there were functional, G-protein coupled beta-adrenergic and bradykinin receptors in these systems. No significant stimulation of [35S]GTP7gammaS binding was noted with serotonin under our experimental conditions. Since stimulation of [35S]GTPgammaS binding by isoproterenol and bradykinin was additive, it was concluded that different Galpha proteins were activated by these two ligands. In analogy to other systems, activation of Gs is most likely by isoproterenol, while Gi and/or Gq/11 proteins might be activated by bradykinin receptors. The possible significance of the receptors and G-proteins detected is being discussed in the functioning of cerebral endothelium, and thus the blood-brain barrier.

Neuropsychological effect of temporal lobe resection in preadolescent children with epilepsy.

PURPOSE: Numerous studies have demonstrated changes in cognitive, memory, and language functioning in adults and adolescents after temporal lobectomy, yet little information is available regarding neuropsychological outcome in preadolescent children. METHODS: We studied pre- and postoperative neuropsychological test results from 14 children who underwent temporal lobe resection for intractable epilepsy at age 7-12 years (mean 9.4 years). RESULTS: Thirteen patients (93%) had no seizures or less than one seizure a year at follow-up 23-48 months (mean 34 months) after operation. Postoperative neuropsychological testing was performed 6-9 months (mean 7 months) after surgery in 13 patients and 36 months after the first operation in 1 patient who underwent two-stage resection of a tumor. Verbal, Performance, and Full Scale IQ were initially in the low-average range, with no significant change across the pre- and postoperative evaluations. Immediate verbal memory performance decreased significantly in children who initially performed above the median preoperatively and tended to decrease in children who had left rather than right temporal lobe resection. Significant postoperative decreases in delayed memory scores were independent of preoperative ability or side of resection. CONCLUSIONS: Our small study suggests vulnerability to postoperative decline in immediate verbal memory scores in preadolescent children who have higher baseline immediate memory function or undergo left rather than right temporal lobe resection, similar to that observed in adolescents in adults. The entire group exhibited a statistically significant decrease in delayed verbal memory. Study of larger series of patients will be important to clarify further the short- and long-term risks and benefits of temporal lobe resection in childhood.

Production of pure primary rat cerebral endothelial cell culture: a comparison of different methods.

To study the blood-brain barrier in vitro pure cerebral endothelial cell cultures, without contaminating cells have to be obtained. Most other cell types besides endothelial cells can be pericytes, a few astrocytes, some smooth muscle cells, fibroblasts and meningeal cells. Careful removal of large vessels and meninges during the dissection and the optimal duration of enzymic digestions can reduce the ratio of contaminant cells. In order to further increase the purity of the culture endothelial cells can be subcloned, however, this is not useful for cells of every species. An alternative choice in cultures from rat is to perform a selective cytolysis by complement and monoclonal anti-Thy 1.1 antibody to eliminate pericytes and astrocytes. The presence of growth factors and the type of serum are also important for successful endothelial cell cultures. With the combination of the cytolysis of contaminating cells and the use of plasma-derived serum, the culturing of pure primary cerebral endothelial cells was successful.

Intracarotid amobarbital testing for language and memory dominance in children.

The intracarotid amobarbital procedure (IAP) was attempted in 22 pediatric epilepsy surgery candidates, ages 5-12 years old. With extra pre-test teaching and emotional preparation, adjusted amobarbital dosage for younger patients, and simplified test items tailored to the child's abilities, language and memory testing were accomplished after at least one injection for 19 (86%) of patients. Language dominance was clarified in 11 children overall (50% of patients), in all of the children who had bilateral testing and at least borderline intelligence (IQ > 70), and in 57% of the children with mild or moderate mental retardation. Memory assessment was accomplished in 18 children after amobarbital injection of the hemisphere ipsilateral to the predominant epileptogenic zone. IAP retention scores tended to be lower in children than adults, especially in the setting of mental retardation. Retention scores after ipsilateral injection were > 60% in all 10 of the children with at least borderline intelligence, but < 60% (25-50%) in five of eight children with mental retardation. Retention scores after contralateral injection were > 60% in only four of 12 children. Our results suggested that a modified pediatric IAP protocol can clarify the hemisphere of language dominance in most verbal preadolescent children with at least borderline intelligence, and in many children with mental retardation. However, IAP memory retention scores tended to be lower in children than adults and should be interpreted with caution.