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PubMed1999

Successful management of intractable epilepsy with intravenous lidocain and lidocain tapes.

The authors report on the successful management of a 6-year-old male with intractable epilepsy using intravenous lidocaine and lidocaine tapes. At 4 years of age, he developed psychomotor deterioration and intractable epilepsy associated with leukoencephalopathy secondary to the treatment of central nervous system leukemia. His seizures were refractory to conventional antiepileptic drugs. The adjunct treatment with intravenous lidocaine and lidocaine tapes proved effective in controlling the intractable seizures. Mental state and motor activity subsequently began to improve after the reduction of the seizures.

Administration, Cutaneous↗
PubMed1998

Glutamate receptor GluR3 antibodies and death of cortical cells.

Rasmussen's encephalitis (RE), a childhood disease characterized by epileptic seizures associated with progressive destruction of a single cerebral hemisphere, is an autoimmune disease in which one of the autoantigens is a glutamate receptor, GluR3. The improvement of some affected children following plasma exchange that removed circulating GluR3 antibodies (anti-GluR3) suggested that anti-GluR3 gained access to the central nervous system where it exerted deleterious effects. Here, we demonstrate that a subset of rabbits immunized with a GluR3 fusion protein develops a neurological disorder mimicking RE. Anti-GluR3 IgG isolated from serum of both ill and healthy GluR3-immunized animals promoted death of cultured cortical cells by a complement-dependent mechanism. IgG immunoreactivity decorated neurons and their processes in neocortex and hippocampus in ill but not in healthy rabbits. Moreover, both IgG and complement membrane attack complex (MAC) immunoreactivity was evident on neurons and their processes in the cortex of a subset of patients with RE. We suggest that access of IgG to epitopes in the central nervous system triggers complement-mediated neuronal damage and contributes to the pathogenesis of both this animal model and RE.

Animals↗
PubMed2003

Electrical impedance tomography of human brain function using reconstruction algorithms based on the finite element method.

Electrical impedance tomography (EIT) is a recently developed technique which enables the internal conductivity of an object to be imaged using rings of external electrodes. In a recent study, EIT during cortical evoked responses showed encouraging changes in the raw impedance measurements, but reconstructed images were noisy. A simplified reconstruction algorithm was used which modelled the head as a homogeneous sphere. In the current study, the development and validation of an improved reconstruction algorithm are described in which realistic geometry and conductivity distributions have been incorporated using the finite element method. Data from computer simulations and spherical or head-shaped saline-filled tank phantoms, in which the skull was represented by a concentric shell of plaster of Paris or a real human skull, have been reconstructed into images. There were significant improvements in image quality as a result of the incorporation of accurate geometry and extracerebral layers in the reconstruction algorithm. Image quality, assessed by blinded subjective expert observers, also improved significantly when data from the previous evoked response study were reanalysed with the new algorithm. In preliminary images collected during epileptic seizures, the new algorithm generated EIT conductivity changes which were consistent with the electrographic ictal activity. Incorporation of realistic geometry and conductivity into the reconstruction algorithm significantly improves the quality of EIT images and lends encouragement to the belief that EIT may provide a low-cost, portable functional neuroimaging system in the foreseeable future.

Adult↗
PubMed2003

Nonconvulsive status epilepticus due to a de novo contralateral focus during tiagabine adjunctive therapy.

We describe a 30-year-old woman with an infantile-onset epilepsy due to a left temporal gliotic area who developed a nonconvulsive status epilepticus (NCSE) during tiagabine (TGB) adjunctive therapy. The ictal EEG recording showed a de novo right temporal focus not previously evident. After the i.v. administration of 4 mg lorazepam, the NCSE episode rapidly resolved and her usual left temporal EEG abnormalities reappeared. To our knowledge this is the first case of paradoxical seizure exacerbation associated with TGB therapy in which the clinical and EEG features are congruous with a new contralateral focus.

Adult↗
PubMed1995

Deliberate overdose with the novel anticonvulsant tiagabine.

Tiagabine is a novel antiepileptic drug which acts by decreasing gamma aminobutyric acid uptake in astrocytes and neurones. Here the first case of deliberate overdose with this compound in a patient on concomitant phenytoin is reported. On admission to hospital his conscious level deteriorated to grade III coma. No changes in the electrocardiogram were noted. Recovery from the initial effects was rapid, and there were no sequelae. Plasma levels of tiagabine (3.1 micrograms/ml) 4 hours after ingestion were 30 times higher than at typical steady state during therapeutic dosing. The effects of poisoning with current first-line antiepileptic drugs are reviewed. The newer agents, particularly those with greater biochemical specificity, may be safer in overdose than the more established anticonvulsants.

Adult↗
PubMed1996

Combination vigabatrin and lamotrigine therapy for intractable epilepsy.

Vigabatrin (GVG) and lamotrigine (LTG) are new antiepileptic drugs (AEDs) individually effective as add-on therapy for refractory seizures. The efficacy of GVG and LTG in combination was evaluated in a prospective audit of 42 patients with intractable epilepsy. There was a statistically significant median reduction of 62% (P < 0.025) from a median baseline monthly seizure frequency (MSF) of 29 (mean 59, 95% CI 22, 96) to a median MSF of 11 (mean 23, 95% CI 8, 38) during a median treatment period of eight months, with a greater than 50% reduction in MSF in 29 patients (69%) treated with the add-on combination of GVG and LTG. The additional MSF reduction achieved by the combination amounted to 21% (18% when GVG was added to LTG and 24% when LTG was added to GVG). The median trough plasma lamotrigine concentration was 9.9 mg/l (range 3.4-19.6 mg/l). The average daily dose of LTG was 517 mg (range, 175-800 mg) and GVG 2400 mg (range, 1500-3500 mg). Adverse events requiring alteration of therapy occurred in 24 patients (57%) with a drop-out rate of 12%. The combination of GVG and LTG should be considered as a therapeutic option in patients with intractable epilepsy. The results of the present study support the need to confirm additive efficacy of GVG and LTG by conducting controlled trials of this combination therapy.

Adolescent↗
PubMed1998

Heart period variability during vagal nerve stimulation.

Vagal nerve stimulation is an emerging therapy for epilepsy, yet little is known regarding the effects of this stimulation on heart period variability. We selected 10 patients (two female, eight male) who were receiving high-frequency, high-intensity left vagal nerve stimulation for intractable epilepsy. Electrocardiogram data were recorded for a 7 min baseline, 2.5 min of stimulation and a 7 min post-stimulation period. We found no significant changes in average heart period, instantaneous changes of successive R-to-R intervals greater than 50 ms or fractal dimension. We also found no significant changes in the total power in the 0.0-0.04 Hz, 0.04-0.12 Hz and 0.2-0.4 Hz bands with stimulation of the left vagus nerve. This study suggests that left vagal nerve stimulation has little acute effect on the cardiac rhythm or heart period variability.

Adolescent↗
PubMed2000

Remote effects of cortical dysgenesis on the primary motor cortex: evidence from the silent period following transcranial magnetic stimulation.

OBJECTIVE: In cortical dysgenesis (CD), animal studies suggested abnormal cortico-cortical connections. Cerebral areas projecting to the primary motor cortex (M1) modulate the cortical silent period (CSP) following transcranial magnetic stimulation (TMS). Therefore, we used the CSP to investigate remote effects of CD on the M1. METHODS: A detailed investigation, including single-pulse TMS and electrical nerve stimulation, was performed in 3 consecutive adults with focal CD located outside the M1 and in 18 controls. Two patients with unilateral CD were epileptic and treated with anti-epileptic drugs. One patient with focal CD on both sides had no history of seizures. Neurological examination was normal in all patients. Recordings were made from both first dorsal interosseous muscles. RESULTS: In CD patients, the CSP was significantly lengthened contralaterally to the affected hemispheres. In treated patients with unilateral CD, the interside difference of the CSP duration was also significantly increased. In contrast, excitability threshold, peripheral and corticospinal motor conduction studies, and peripheral as well as ipsilateral silent periods were not significantly modified. CONCLUSIONS: Our findings indicate that focal CD outside the M1 may produce CSP modifications, which are likely due to changes of afferent control.

Adult↗
PubMed2001

Space-oriented segmentation and 3-dimensional source reconstruction of ictal EEG patterns.

OBJECTIVES: Characterization of the EEG pattern during the early phase of a seizure is crucial for identifying the epileptic focus. The purpose of the present investigation was to evaluate a method that divides ictal EEG activity into segments of relatively constant surface voltage distribution, and to provide a 3-dimensional localization of the activity during the different segments. METHODS: For each timepoint the electrical voltage distribution on the scalp (the voltage map) was determined from the digitized EEG recording. Through a spatial cluster analysis time sequences where the maps did not change much (segments) were identified, and a 3-dimensional source reconstruction of the activity corresponding to the different mean maps was performed using a distributed linear inverse solution algorithm. RESULTS: Segments dominating early in seizure development were identified, and source reconstruction of the EEG activity corresponding to the maps of these segments yielded results which were consistent with the results from invasive recordings. In some cases a sequence of consecutive segments was obtained, which might reflect ictal propagation. CONCLUSIONS: Segmentation of ictal EEG with subsequent 3-dimensional source reconstruction is a useful method to non-invasively determine the initiation and perhaps also the spread of epileptiform activity in patients with epileptic seizures.

Adolescent↗
PubMed2001

Somatosensory evoked high frequency oscillations recorded from subdural electrodes.

OBJECTIVES: To examine high frequency oscillations (HFOs) of somatosensory evoked potentials (SEPs) recorded directly from subdural electrodes to investigate the relationship between the primary somatosensory cortex and HFOs. METHODS: SEPs were recorded directly from subdural electrodes previously implanted in 3 patients for clinical evaluation prior to surgical treatment of intractable epilepsy. RESULTS: The primary sensory cortex (area 3b) was proposed as the source of somatosensory HFOs, because the distribution of HFOs recorded from the subdural electrodes agreed with the distribution of the N20-P20 components of the somatosensory evoked potential. The somatosensory HFOs showed a strictly somatotopic source arrangement. There was a polarity inversion of the prophase component and also the N20-P20 component of HFOs across the central sulcus. However, the phase was synchronized in the latter part of the HFOs. CONCLUSIONS: We propose that the origins of the early and latter parts of HFOs are different, and that there was a clear somatotopy.

Adult↗
PubMed1999

Face-selective spectral changes in the human fusiform gyrus.

OBJECTIVE: To characterize ventral occipitotemporal and prefrontal EEG during cognitive processing. METHODS: Depth probes were implanted for seizure localization in 16 pharmaco-resistant epileptics. Probes penetrated from middle temporal through fusiform to lingual gyrus, and from inferior frontal to anterior cingulate gyrus. Event-related potentials (ERPs) and event-related spectral power (ERSP) were calculated during delayed recognition for faces or words. RESULTS: Face stimuli evoked a broadband fusiform ERSP increase from 5 to 45 Hz at 150-210 ms after stimulus onset. This ERSP increase was immediately followed by an ERSP decrease in the same region from 300 to 1000 ms. Both the early increased ERSP and the late decreased ERSP, were greater for faces than words. Simultaneous with the late temporal ERSP decrease, the prefrontal depth EEG displayed a low frequency (5-12 Hz) ERSP increase to face and word stimuli. CONCLUSION: Early temporal ERSP increases occur at a time when the fusiform gyrus is thought to contribute to face processing. This increase is also reflected in spectral analysis of the ERP, but the late temporal ERSP decrease and frontal ERSP increase are not. Thus, intracranial recordings in humans demonstrate event-related fluctuations in EEG spectral power with clear anatomical, temporal and cognitive specificity.

Brain↗
PubMed1999

Measuring the coherence of intracranial electroencephalograms.

OBJECTIVE: Previous coherence studies of human intracranial electroencephalograms (EEGs) can be faulted on two methodological issues: (1) coherence estimates in a majority were formed from a very small number of independent sample spectra, and (2) the statistical significance of coherence estimates was either not reported or was poorly evaluated. Coherence estimator performance may be poor when a small number of independent sample spectra are employed, and the coupling of poor estimation and statistical testing can result in inaccuracy in the measurement of coherence. The performance characteristics of the coherence estimator and statistical testing of coherence estimates are described in this manuscript. METHODS: The bias, variance, probability density functions, and confidence intervals of the estimate of magnitude squared coherence (MSC); and power analysis for the test of zero MSC were developed from the exact analytic form of the probability density function of the estimate of MSC for Gaussian random processes. The coherence of a single epoch of background EEG, recorded from a patient with intractable seizures, was evaluated with different parameter values to aid in the exposition of the concepts developed here. RESULTS: The statistical characteristics of WOSA coherence estimates are a function of a single estimator parameter, the number of independent sample spectra employed in the estimation. Bias and variance are high, confidence intervals may be large, and the probability of Type II errors is high if a small number of independent sample spectra are employed. A considerable improvement in measurement accuracy is possible with careful selection of estimator parameter values. CONCLUSIONS: Coherence measurement accuracy can be improved over previous applications by attention to estimator performance and accurate statistical testing of coherence estimates.

Adult↗
PubMed1999

Reorganization of verbal memory and language: a case of dissociation.

Left-to-right reorganization of verbal memory following early left hemisphere damage has been reported in patients whose expressive language is governed by the right hemisphere. We present a case in which verbal memory performance was intact, despite severe left mesial temporal damage, and despite aphasia on left internal carotid sodium amytal ablation. The distribution and degree of left mesial temporal damage was assessed visually and quantitatively on MRI. These findings raise the possibility that verbal memory may shift to the language-nondominant hemisphere as a result of early left mesial temporal damage.

Brain Damage, Chronic↗
PubMed2000

A quantitative study of gamma-band activity in human intracranial recordings triggered by visual stimuli.

This paper studies gamma-band responses from two implanted epileptic patients during a simple visual discrimination task. Our main aim was to ascertain, in a reliable manner, whether evoked (stimulus-locked) and induced (triggered by, but not locked to, stimuli) responses are present in intracranial recordings. For this purpose, we introduce new methods adapted to detect the presence of gamma responses at this level of recording, intermediary between EEG-scalp and unicellular responses. The analysis relies on a trial-by-trial time-frequency analysis and on the use of surrogate data for statistical testing. We report that visual stimulation reliably elicits evoked and induced responses in human intracranial recordings. Induced intracranial gamma activity is significantly present in short oscillatory bursts (a few cycles) following visual stimulation. These responses are highly variable from trial to trial, beginning after 200 ms and lasting up to 500 ms. In contrast, intracranial-evoked gamma responses concentrate around 100 ms latencies corresponding to evoked responses observed on the scalp. We discuss our results in relation to scalp gamma response in a similar protocol [Tallon-Baudry et al. (1996) J. Neurosci., 16, 4240-4249] and draw some conclusions for bridging the gap between gamma oscillations observed on the scalp surface and their possible cortical sources.

Adolescent↗