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M Baulac

Publications and source records attributed to M Baulac.

At least 37 records · Page 2Linked to original sources

Recommendations on the clinical use of oxcarbazepine in the treatment of epilepsy: a consensus view.

Extensive clinical use and a series of clinical trials have shown that oxcarbazepine is a valuable antiepileptic drug for the treatment of adults and children with partial onset seizures both in initial monotherapy, for conversion to monotherapy and as adjunctive therapy. The clinically recommended titration scheme for all forms of therapy in adults is to start with 150 mg/day at night and to increase by 150 mg/day every second day until a target dose of 900-1200 mg/day is reached. If necessary, one can go faster and start with up to 600 mg/day and titrate with weekly increments of up to 600 mg/day. In children, treatment can be initiated with 8-10 mg/kg/day body weight in two to three divided doses. Dosage can be increased by 8-10 mg/kg/day in weekly increments if necessary for seizure control. Hyponatremia (serum sodium <125 mmol/l) can develop gradually during the first months of oxcarbazepine therapy in approximately 3% of patients with a previously normal serum sodium. However, there is no need to measure baseline serum sodium concentrations unless the patient has renal disease, is taking medication which may lower serum sodium levels (such as diuretics, oral contraceptives or nonsteroidal anti-inflammatory drugs) or--in rare cases--has clinical symptoms of hyponatremia. During oxcarbazepine maintenance therapy measurement of serum sodium levels should also be considered if medications known to decrease sodium levels are added or symptoms of hyponatremia develop. Oxcarbazepine does not appear to have any clinically notable effects on other safety parameters such as renal and liver function or haematological test results. In summary, oxcarbazepine is a safe and well tolerated antiepileptic drug for partial epilepsy.

Anticonvulsants↗

First genetic evidence of GABA(A) receptor dysfunction in epilepsy: a mutation in the gamma2-subunit gene.

Major advances in the identification of genes implicated in idiopathic epilepsy have been made. Generalized epilepsy with febrile seizures plus (GEFS+), benign familial neonatal convulsions and nocturnal frontal lobe epilepsy, three autosomal dominant idiopathic epilepsies, result from mutations affecting voltage-gated sodium and potassium channels, and nicotinic acetylcholine receptors, respectively. Disruption of GABAergic neurotransmission mediated by gamma-aminobutyric acid (GABA) has been implicated in epilepsy for many decades. We now report a K289M mutation in the GABA(A) receptor gamma2-subunit gene (GABRG2) that segregates in a family with a phenotype closely related to GEFS+ (ref. 8), an autosomal dominant disorder associating febrile seizures and generalized epilepsy previously linked to mutations in sodium channel genes. The K289M mutation affects a highly conserved residue located in the extracellular loop between transmembrane segments M2 and M3. Analysis of the mutated and wild-type alleles in Xenopus laevis oocytes confirmed the predicted effect of the mutation, a decrease in the amplitude of GABA-activated currents. We thus provide the first genetic evidence that a GABA(A) receptor is directly involved in human idiopathic epilepsy.

Amino Acid Sequence↗

Is amygdalohippocampectomy really selective in medial temporal lobe epilepsy? A study using positron emission tomography with (18)fluorodeoxyglucose.

PURPOSE: Selective amygdalohippocampectomy (SAH) is a surgical technique effective for the treatment of medial temporal lobe epilepsy, which selectively removes the epileptogenic hippocampus and amygdala but spares the temporal neocortex. However, the benefit of SAH in terms of functional outcome is debated. In this study, we aimed to assess the metabolic consequences of SAH. METHODS: Volumetric magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (PET) studies were performed in nine patients with medial temporal lobe epilepsy associated with hippocampal sclerosis before and after SAH. Regions of interest were delineated on MRIs and then replaced on PET images using an automatic 3D image registration. We calculated absolute metabolic rates of glucose and normalized metabolic values in each region of interest. RESULTS: The comparison between preoperative and postoperative metabolic values showed a statistically significant worsening of the hypometabolism on the ipsilateral temporal pole on the superior and the hippocampal levels (p < 0.05 and 0.0045, respectively). A postoperative increase of the metabolic activity also was noted in the contralateral anterior hippocampus (p < 0.05) and the orbitofrontal cortex bilaterally (p < 0.002 and 0.001, respectively) CONCLUSIONS: SAH functional benefit is controversial. SAH worsened significantly the hypometabolism of a temporal structure that was not surgically removed (i.e., the temporal pole), and it improved postoperatively the metabolic activity in the contralateral hippocampus and the orbitofrontal cortex. Whether this postoperative improvement is linked to the selectivity of the surgical procedure must be further clarified.

Adult↗

Cerebral substrates for musical temporal processes.

Music as well as language consists of a succession of auditory events in time, which require elaborate temporal processing. Although several lines of evidence suggest that the left dominant hemisphere is predominantly involved in the processing of rapid temporal changes of speech, very little is known about the cerebral substrates underlying such auditory temporal processes in music. To investigate this issue, we examined epileptic patients with either left (LTL) or right (RTL) temporal lobe lesions as well as normal control subjects (NC) in two different tasks involving the processing of time-related (temporal) information. By manipulating the interonset interval (IOI) in a psychophysical task, as well as in a task of detection of rhythmic changes in real tunes, we studied the processing of temporal microvariations in music. The first task assessed anisochrony (or irregularity) discrimination of sequential information according to different presentation rates (between 80 and 1000 ms IOI). For all subjects, an effect of tempo was obtained; thresholds were lower for the 80 ms IOI than for longer IOIs. Furthermore, there was a specific impairment of rapid anisochronous discrimination (80 ms IOI) for LTL patients as compared to RTL and NC subjects, but no deficit was observed for longer IOIs. These findings suggest the specialization of left temporal lobe structures in processing rapid sequential auditory information. The second task involved the detection of IOI increments in familiar monodic tunes. Performance was measured for two increments (easy vs. difficult to detect according to cognitive expectation) to assess the effect of cognitive expectation using a forced-choice paradigm (changed vs. unchanged melody). The results showed that LTL patients but not RTL were impaired as compared to NC subjects in the increment detection. However, all groups showed differences between the two levels of difficulty, suggesting that top-down processing remains functional. These findings suggest that left temporal lobe structures are predominantly involved in perceiving time-related perturbations in familiar tunes as well as in isochronous sequences, extending to the musical domain findings previously reported in speech.

Auditory Perception↗

Functional MR evaluation of temporal and frontal language dominance compared with the Wada test.

OBJECTIVE: To evaluate the reliability of temporal and frontal functional MRI (fMRI) activation for the assessment of language dominance, as compared with the Wada test. PATIENTS AND METHODS: Ten patients with temporal lobe epilepsy were studied using blood oxygen level dependent fMRI and echoplanar imaging (1.5-T). Three tasks were used: semantic verbal fluency, covert sentence repetition, and story listening. Data were analyzed using pixel by pixel autocorrelation and cross-correlation. fMRI laterality indices were defined for several regions of interest as the ratio (L - R)/(L + R), L being the number of activated voxels in the left hemisphere and R in the right hemisphere. Wada laterality indices were defined as the difference in the percentages of errors in language tests between left and right carotid injections. RESULTS: Semantic verbal fluency: The asymmetry of frontal activation was correlated with Wada laterality indices. The strongest correlation was observed in the precentral/middle frontal gyrus/inferior frontal sulcus area. Story listening: The asymmetry of frontal, but not temporal, activation was correlated with Wada laterality indices. Covert sentence repetition: No correlation was observed. CONCLUSIONS: There was a good congruence between hemispheric dominance for language as assessed with the Wada test and fMRI laterality indices in the frontal but not in the temporal lobes. The story listening and the covert sentence repetition tasks increased the sensitivity of detection of posterior language sites that may be useful for brain lesion surgery.

Adolescent↗

[Surgery of epilepsy: current status].

PRELIMINARY EXPLORATIONS: The advent of magnetic resonance imaging and its capacity to detect fine structural injury and SPECT and PET functional imaging as well as the generalization of EEG-video and the simplification of intracranial electrode implantation techniques has given a whole new life to surgery in epilepsy. Preoperative explorations are shorter and less invasive, allowing surgery without implantation of intracranial electrodes in more than 70% of the cases. SURGERY: New surgical techniques (subpial transection, neuro-navigation...) and improvement in well-known procedures (amygdalo-hippocampectomy...) has made it possible to propose lower risk procedures with minimal trauma (overall complication rate < 10%), particularly for temporal epilepsy where the success rate is greater than 80%. FUNDAMENTAL RULE: The key to success however directly depends on rigorous application of the fundamental rule of anatomo-electro-clinical correlation.

Amygdala↗

Accurate prediction of postoperative outcome in mesial temporal lobe epilepsy: a study using positron emission tomography with 18fluorodeoxyglucose.

BACKGROUND: Recent studies suggest that positron emission tomography may be a reliable predictive indicator of clinical outcome following surgical treatment for epilepsy. OBJECTIVE: We evaluated 30 patients with documented medial temporal lobe epilepsy to determine if prediction of postoperative outcome is improved with the use of positron emission tomography with (18)fluorodeoxyglucose. PATIENTS AND METHODS: We performed a discriminant analysis to determine the combination of metabolic asymmetry indexes in temporal and extratemporal regions defined by magnetic resonance imaging that best predicted the postoperative outcome. Seizure outcome was assessed at least 2 years after surgery: patients were classified as seizure free (n = 14, group A), mostly improved (n = 10, group B), or as having persistent seizures (n = 6, group C). RESULTS: Discriminant analysis was first performed in groups A and C. The temporal pole seemed to be the only temporal region for which metabolism was a significant predictor of the postoperative outcome (F(1,18) = 10.19; P =.005). The predictive value of positron emission tomography with (18)fluorodeoxyglucose was considerably improved by the multivariate analysis (F(4,15) = 7.21; P =.002), which correctly predicted the 2 -year prognosis in 100% of the patients using 4 regions: the temporal pole, the medial temporal region, the anterior part of the lateral temporal neocortex, and the basofrontal region. As a validation, we performed this 4-region analysis in the patients in group B. The difference among the 3 groups was highly significant (F = 15.5, P<.001). CONCLUSION: These findings suggest that the interictal metabolic pattern reliably predicts the 2-year prognosis after surgery in patients with medial temporal lobe epilepsy.

Adult↗

Spatio-temporal characterizations of non-linear changes in intracranial activities prior to human temporal lobe seizures.

Recent studies have shown that non-linear analysis of intracranial activities can detect a 'pre-ictal phase' preceding the epileptic seizure. Nevertheless, the dynamical nature of the underlying neuronal process and the spatial extension of this pre-ictal phase still remain unknown. In this paper, we address these aspects using a new non-linear measure of dynamic similarity between different parts of intracranial recordings of nine patients with medial temporal lobe epilepsy recorded during transitions to seizure. Our results confirm that non-linear changes in neuronal dynamics allow, in most cases (16 out of 17), a seizure anticipation several minutes in advance. Furthermore, we show that the spatial distribution of pre-ictal changes often involves an extended network projecting beyond the limits of the epileptogenic region. Finally, the pre-ictal phase could frequently (13 out of 17) be characterized with a marked shift toward slower frequencies in upper delta or theta frequency range.

Cerebral Cortex↗

Episodic memory in left temporal lobe epilepsy: a functional MRI study.

Left medial temporal lobe epilepsy (MTLE) is associated with verbal memory impairment usually related to hippocampal damage. We used functional MRI (fMRI) to investigate the patterns of functional activity in healthy volunteers and MTLE patients engaged in verbal episodic memory tasks to look for evidence of a reallocation of verbal memory in epileptic patients. fMRI data were collected from seven MTLE patients with left-sided hippocampal sclerosis and 10 healthy right-handed control subjects on a 3T scanner. Subjects were instructed to learn a list of 17 words (encoding) and then to recall them (retrieval) on successive trials. Healthy volunteers and patients both exhibited bilateral activation (right higher than left) of the parahippocampal gyrus during the retrieval. This effect was more marked in the control subjects. In contrast to the control subjects, patients exhibited consistent and extensive left prefrontal activations in all the memory tasks. These findings show that verbal memory tasks did not involve the same functional patterns in patients and healthy volunteers. This may be interpreted as a dysfunctional response due to the epilepsy and left hippocampal sclerosis, and could reflect the early onset and progressive course of the disease.

Adolescent↗

Lesions affecting the parahippocampal cortex yield spatial memory deficits in humans.

Anatomical studies in monkeys, and functional imaging and lesion studies in humans, suggest that, within the primate medial temporal neocortex, the parahippocampal cortex (PHC) is particularly involved in spatial tasks. However, evidence for a functional specialization of the PHC regarding its spatial memory functions has so far been lacking. Here, we investigated spatial memory functions of the human perirhinal cortex (PRC) and PHC. Patients with lesions affecting the PRC but sparing the PHC, and patients with lesions affecting both PRC and PHC, performed an oculomotor delayed response task with unpredictably varied memory delays of up to 30 s. Compared to controls, patients with PRC+PHC lesions showed a significant delay-dependent inaccuracy of memory-guided eye movements contralateral to the lesion side, whereas patients with PRC lesions showed no significant inaccuracy. Our results show that the PHC is a critical component for spatial memory in humans and suggest that (i) extrahippocampal spatial memory functions of the medial temporal lobe may not be equally distributed in the medial temporal neocortex, but may be largely confined to the PHC, and (ii) damage to connections between cortices involved in spatial cognition and rostral regions of the temporal lobe is unlikely to account for the observed spatial memory deficits with PHC lesions.

Adult↗

[Study of hemispheric lateralization of language regions by functional MRI. Validation with the Wada test].

Language hemispheric dominance can be assessed by the Wada test before temporal lobectomy, in patients with refractory epilepsy of the mesial temporal lobe. Functional MR is a less invasive technique which recently demonstrated the ability to localize some language areas. The aim of this study was to determine if functional MR can be substituted to the Wada test in the determination of language dominance. Seven patients with a refractory epilepsy of the mesial temporal lobe were included. The MR protocol was carried out using a 1.5 T system including 12 axial gradient echo BOLD EPI images. A semantic fluency task, interspersed with rest periods, was used as activation paradigm. An activation of middle and inferior frontal region was found in all patients. It predominated in the left hemisphere in 6 cases and in the right hemisphere in 1 case. The hemispheric and frontal lobe lateralization of the functional MR activation was correlated with the hemispheric language dominance as assessed by the Wada test. In conclusion, functional MR is a promising technique in the determination of language dominance.

Adolescent↗

[MRI of drug-resistant epilepsies: contribution of FLAIR sequence in a series of 150 patients].

We studied the usefulness of the Fluid-Attenuated Inversion-Recovery (FLAIR) pulse sequence for patients with intractable seizures by reviewing the MR images of 150 consecutive patients including a standard imaging protocol and a FLAIR sequence. FLAIR images revealed a cortical lesion in 8 of the 81 patients with no lesion detected on the standard MR imaging protocol. In addition, FLAIR images provided additional informations for 13 patients of the 69 patients for whom a lesion was already detected on the standard MR imaging protocol. Therefore, our results indicated that FLAIR sequences were a useful imaging tool for patients with intractable seizures since it improved the MR diagnosis in 21 of 150 patients (14%).

Adolescent↗

Anticipating epileptic seizures in real time by a non-linear analysis of similarity between EEG recordings.

In a previous publication we showed that non-linear analysis can extract spatio-temporal changes of brain electrical activity prior to epileptic seizures. Here we describe a new method to analyze this long-term non-stationarity in the EEG by a measure of dynamical similarity between different parts of the time series. We apply this method to the study of a group of patients with temporal lobe epilepsy recorded intracranially during transitions to seizure. We show that the method, which can be implemented on a personal computer, can track in real time spatio-temporal changes in brain dynamics several minutes prior to seizure.

Algorithms↗

Association of ipsilateral motor automatisms and contralateral dystonic posturing: a clinical feature differentiating medial from neocortical temporal lobe epilepsy.

BACKGROUND: Clinical features that may help to differentiate medial temporal lobe epilepsy (MTLE) from neocortical temporal lobe epilepsy (NTLE) are lacking. OBJECTIVE: To investigate the localizing and lateralizing value of the association of ipsilateral motor automatisms and contralateral dystonic posturing in patients with medically refractory temporal lobe epilepsy. PATIENTS AND METHODS: Videotapes of 60 patients with well-defined MTLE, NTLE, or both were reviewed to assess the presence and the localizing value of unilateral dystonic posturing associated with motor automatisms. RESULTS: Twenty-eight of the 60 patients exhibited unilateral dystonic posturing. This sign was observed in patients with MTLE and NTLE. It was mostly contralateral to the seizure focus in patients with MTLE and exclusively ipsilateral in patients with NTLE. Unilateral motor automatisms occurred in 26 of the 60 patients with MTLE or NTLE. It was predominantly ipsilateral to the seizure focus in patients with MTLE and exclusively contralateral in patients with NTLE. The association of ipsilateral motor automatisms and contralateral dystonic posturing was found in 14 patients with MTLE but in none of the patients with NTLE. Two patients who had medial and neocortical seizure onset also exhibited this clinical feature. This association was not significantly correlated with the postoperative outcome in patients with MTLE. CONCLUSIONS: The association of ipsilateral motor automatisms and contralateral dystonic posturing may help to differentiate MTLE from NTLE with a reliable lateralizing value. This clinical association may reflect a specific pattern in the spread of the ictal discharge.

Adult↗

Spatial memory deficits in patients with lesions affecting the medial temporal neocortex.

Lesion studies in monkeys suggest that neocortical subregions of the medial temporal lobe (MTL) carry memory functions independent of the hippocampal formation. The present study investigates possible differential contributions of MTL subregions to spatial memory in humans. Eye movements toward remembered spatial cues (memory-guided saccades) with unpredictably varied memorization delays of up to 30 seconds were recorded in patients with postsurgical lesions of the right MTL, either restricted to the hippocampal formation (n = 3) or including the adjacent neocortex (n = 5) and in 10 controls. Although saccadic targeting errors of patients with selective hippocampal lesions did not differ from controls, saccadic targeting errors of patients with additional neocortical involvement showed a significant and contralaterally pronounced increase at memorization delays above 20 seconds. We conclude that the human medial temporal neocortex carries spatial memory functions independent of the hippocampal formation and distinct from spatial short-term memory.

Adult↗

Bilateral mesial temporal sclerosis: MRI with high-resolution fast spin-echo and fluid-attenuated inversion-recovery sequences.

We report a retrospective analysis of MRI in 206 patients with intractable seizures and describe the findings in bilateral mesial temporal sclerosis (MTS) on fast spin-echo (FSE) and fast fluid-attenuated inversion-recovery (fFLAIR) sequences. Criteria for MTS were atrophy, signal change and loss of the digitations of the head of the hippocampus. In patients with bilateral MRI signs of MTS, correlation with clinical electro, volumetric MRI data and neuropsychological tests, when available, was performed. Bilateral MTS was observed in seven patients. Bilateral loss of the digitations and signal change on fFLAIR was seen in all seven. In three, bilateral atrophy was obvious. In two patients, mild bilateral atrophy was observed and in two others, the hippocampi were: asymmetrical, with obvious atrophy on only one side. Volumetric data confirmed bilateral symmetrical atrophy in five patients, and volumes were at the lowest of the normal range in the other two. The EEG showed temporal abnormalities in all patients, unilateral in five and bilateral in two. All patients had memory impairment and neuropsychological data confirmed visual and verbal memory deficits; two patients failed the Wada test on both sides. High-resolution T2-weighted FSE and fFLAIR sequences allow diagnosis of bilateral MTS, which has important therapeutic and prognostic implications.

Adult↗

Specificity of memory deficits after right or left temporal lobectomy.

An impairment of verbal memory has consistently been associated with resection of the left dominant temporal lobe, whereas non-verbal memory deficits have been less reliably observed following resection of the right temporal lobe. Such a dissociation may be due to material-specific differences of processing between verbal and non-verbal information. Alternatively, the influence of the left and right limbic structures may vary according to the stage of memory processing. The aim of the study was to test these hypotheses by comparing verbal and spatial learning in patients with left or right temporal lobe resection for intractable epilepsy, using verbal and visuospatial memory tasks with the same design: control of encoding, multiple trial learning, free and cued recall, short and long delays. The results showed: (1) a similar pattern of learning and recall in the two groups; (2) a higher performance in spatial learning for patients with left temporal lobe resection and in verbal learning for patients with right temporal lobe resection; (3) material-specific effects characterized by a higher sensitivity to cues in the verbal domain and a better retention of information during delays in the spatial domain. These results suggest parallel processing of the two temporal lobes at the various memory stages, rather than an interaction between memory stage and side of the lesion similar to that already proposed for the frontal lobes. They also confirm a double dissociation between verbal/spatial information processing and side of temporal lobe resection.

Adult↗