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M D'Havé

Publications and source records attributed to M D'Havé.

14 recordsLinked to original sources
PubMed2002

Vagus nerve stimulation for epilepsy, clinical efficacy of programmed and magnet stimulation.

RATIONALE: Vagus nerve stimulation (VNS) by intermittent and programmed electrical stimulation of the left vagus nerve in the neck, has become widely available. It is an effective treatment for patients with refractory epilepsy. Patients can be provided with a magnet that allows to deliver additional stimulation trains. Since earlier studies have demonstrated the persistence of a stimulation effect after discontinuation of the stimulation train, we evaluated the clinical efficacy of VNS both in the programmed intermittent stimulation mode and magnet stimulation mode. METHODS: A group of 30 patients (16 F, 14 M) with medically refractory partial epilepsy, who were unsuitable candidates for resective surgery, were included in the study. The patients, their companions and caregivers were instructed on how to administer additional stimulation trains using a hand-held magnet when an aura or a seizure onset occurred. Patients or caregivers could recognize habitual seizures and were able to evaluate sudden interruption of these seizures. Using seizure diaries, detailed accounts of magnet use and regular clinic follow-up visits, data on seizure frequency and severity and number of magnet applications were collected. Patients who provided unreliable information were excluded from the analysis. RESULTS: Forty-seven percent of all patients had an improvement in seizure control with a reduction in seizure frequency of more than 50% during a mean follow-up of 33 months (range: 4-67 months). More than half of the patients used the magnet and provided reliable information. In 63% of patients who were able to self-administer or receive additional magnet stimulation, seizures could be interrupted, be it consistently or occasionally. More than half of the patients who reported a positive effect of magnet stimulation became responders. In most cases the magnet was applied by a caregiver. CONCLUSIONS: To our knowledge, this study is the first to explore the efficacy of magnet-induced vagus nerve stimulation. Results suggest that the magnet is a useful tool that provides patients and mainly caregivers with an additional means of controlling refractory seizures. Additional controlled studies comparing programmed stimulation and magnet-induced stimulation in monitoring conditions are warranted.

Adolescent↗
PubMed2002

Direct medical costs of refractory epilepsy incurred by three different treatment modalities: a prospective assessment.

PURPOSE: More than 20% of epilepsy patients have refractory seizures. Treatment options for these patients include continued polytherapy with/without novel antiepileptic drugs (AEDs), epilepsy surgery (ES), or vagus nerve stimulation (VNS). The purpose of this study was prospectively to compare epilepsy-related direct medical costs (ERDMCs) incurred by these different treatment modalities. METHODS: Eighty-four patients underwent a complete presurgical evaluation protocol at our institution. As a result, 24 (29%) patients were treated with continued AED polytherapy only; 35 (40%) underwent ES; and 25 (30%) had VNS. In each patient, annual costs in the 2 years preceding the therapeutic decision (ERDMC-pre) and during the follow-up afterward (ERDMC-post) were prospectively calculated. Furthermore, frequency of complex partial seizures with/without secondary generalization (CPS+/-SG), dosage and number of AEDs, number of hospital admission days, clinic visits, and laboratory tests before and after the therapeutic decision also were prospectively assessed. ERDMC-pre and ERDMC-post were compared in and among the three treatment groups. RESULTS: In patients conservatively treated with AEDs, mean frequency of CPSs decreased from 12 per month to nine per month, whereas mean ERDMCs decreased from $2,525 U.S. to $2,421 U.S. In surgical patients, mean seizure frequency decreased from six to fewer than one per month; mean ERDMCs per year decreased from $1,465 U.S. preoperatively to $1,186 U.S. postoperatively. In the VNS group, mean seizure frequency decreased from 21 per month to seven per month. ERDMCs in this subgroup decreased from $4,826 U.S. to $2,496 U.S. Mean seizure frequency changes were significant when conservatively treated patients were compared with surgically treated and VNS patient groups (chi2 test, p<0.001 and p=0.0019, respectively). ERDMC changes in conservatively treated patients also were statistically significant when compared with surgically treated and VNS patients (chi2 test, p=0.0007 and p=0.0036, respectively). No statistically significant differences were found in ERDMC changes between the surgical and VNS groups (chi2 test, p=0.387). CONCLUSIONS: Ongoing daily treatment of patients who underwent resective surgery costs significantly less than conservative treatment. For patients in whom resective surgery is not an option, ERDMC show a significant decrease in VNS-treated patients compared with conservatively treated patients.

Adult↗
PubMed2001

Anticipation of epileptic seizures from standard EEG recordings.

BACKGROUND: New methods derived from non-linear analysis of intracranial recordings permit the anticipation of an epileptic seizure several minutes before the seizure. Nevertheless, anticipation of seizures based on standard scalp electroencephalographical (EEG) signals has not been reported yet. The accessibility to preictal changes from standard EEGs is essential for expanding the clinical applicability of these methods. METHODS: We analysed 26 scalp-EEG/video recordings, from 60 min before a seizure, in 23 patients with temporal-lobe epilepsy. For five patients, simultaneous scalp and intracranial EEG recordings were assessed. Long-term changes before seizure onset were identified by a measure of non-linear similarity, which is very robust in spite of large artifacts and runs in real-time. FINDINGS: In 25 of 26 recordings, measurement of non-linear changes in EEG signals allowed the anticipation of a seizure several minutes before it occurred (mean 7 min). These preictal changes in the scalp EEG correspond well with concurrent changes in depth recordings. INTERPRETATION: Scalp-EEG recordings retain sufficient dynamical information which can be used for the analysis of preictal changes leading to seizures. Seizure anticipation strategies in real-time can now be envisaged for diverse clinical applications, such as devices for patient warning, for efficacy of ictal-single photon emission computed tomography procedures, and eventual treatment interventions for preventing seizures.

Electroencephalography↗
PubMed2001

Programmed and magnet-induced vagus nerve stimulation for refractory epilepsy.

Vagus nerve stimulation (VNS) is an effective alternative treatment for patients with refractory epilepsy. The generator produces intermittent stimulation trains and does not require patient intervention. Using currently available technology, continuous stimulation is incompatible with a reasonable battery life. Because earlier studies have demonstrated the persistence of a stimulation effect after discontinuation of the stimulation train, we intended to evaluate the clinical efficacy of VNS in both the programmed intermittent stimulation mode and the magnet stimulation mode. Patients, companions, and caregivers were instructed on how to administer additional stimulation trains when an aura or a seizure onset occurred. We assumed that patients or caregivers could recognize habitual seizures and were able to evaluate sudden interruption of these seizures. During a mean follow-up of 35 months, 46% of patients became responders, with a reduction in seizure frequency of more than 50%. Twenty-nine percent of patients stopped having convulsive seizures. In two thirds of patients who were able to self-administer or receive additional magnet stimulation, seizures could be interrupted consistently or occasionally. More than half of the patients who reported a positive effect of magnet stimulation became responders. Only three patients were able to use the magnet themselves. In most cases, support from caregivers was necessary. This study is the first to document the efficacy of magnet-induced VNS in a larger patient population during long-term follow-up. The magnet is a useful tool that provides patients who are treated with VNS and mainly caregivers of such patients with an additional means of controlling seizures. To further confirm the self-reported results from our patients, additional studies comparing programmed stimulation and magnet-induced stimulation during monitoring conditions are needed.

Adolescent↗
PubMed2000

Dipole location errors in electroencephalogram source analysis due to volume conductor model errors.

An examination is made of dipole location errors in electroencephalogram (EEG) source analysis, due to not incorporating the ventricular system (VS), omitting a hole in the skull and underestimating skull conductivity. The simulations are performed for a large number of test dipoles in 3D using the finite difference method. The maximum dipole location error encountered, utilising 27 and 53 electrodes is 7.6 mm and 6.1 mm, respectively when omitting the VS, 5.6 mm and 5.2 mm, respectively when neglecting the hole in the skull, and 33.4 mm and 28.0 mm, respectively when underestimating skull conductivity. The largest location errors due to neglecting the VS can be found in the vicinity of the VS. The largest location errors due to omitting a hole can be found in the vicinity of the hole. At these positions the fitted dipoles are found close to the hole. When skull conductivity is underestimated, the dipole is fitted close to the skull-brain border in a radial direction for all test dipoles. It was found that the location errors due to underestimating skull conductivity are typically higher than those found due to neglecting the VS or neglecting a hole in the skull.

Electric Conductivity↗
PubMed2000

Influence of measurement noise and electrode mislocalisation on EEG dipole-source localisation.

Measurement noise in the electro-encephalogram (EEG) and inaccurate information about the locations of the EEG electrodes on the head induce localisation errors in the results of EEG dipole source analysis. These errors are studied by performing dipole source localisation for simulated electrode potentials in a spherical head model, for a range of different dipole locations and for two different numbers (27 and 148) of electrodes. Dipole source localisation is performed by iteratively minimising the residual energy (RE), using the simplex algorithm. The ratio of the dipole localisation error (cm) to the noise level (%) of Gaussian measurement noise amounts to 0.15 cm/% and 0.047 cm/% for the 27 and 148 electrode configurations, respectively, for a radial dipole with 40% eccentricity The localisation error due to noise can be reduced by taking into account multiple time instants of the measured potentials. In the case of random displacements of the EEG electrodes, the ratio of dipole localisation errors to electrode location errors amounts to 0.78 cm-1 cm and 0.27 cm-1 cm for the 27 and 148 electrode configurations, respectively. It is concluded that it is important to reduce the measurement noise, and particularly the electrode mislocalisation, as the influence of the latter is not reduced by taking into account multiple time instants.

Electricity↗
PubMed2000

EEG dipole source localization using artificial neural networks.

Localization of focal electrical activity in the brain using dipole source analysis of the electroencephalogram (EEG), is usually performed by iteratively determining the location and orientation of the dipole source, until optimal correspondence is reached between the dipole source and the measured potential distribution on the head. In this paper, we investigate the use of feed-forward layered artificial neural networks (ANNs) to replace the iterative localization procedure, in order to decrease the calculation time. The localization accuracy of the ANN approach is studied within spherical and realistic head models. Additionally, we investigate the robustness of both the iterative and the ANN approach by observing the influence on the localization error of both noise in the scalp potentials and scalp electrode mislocalizations. Finally, after choosing the ANN structure and size that provides a good trade off between low localization errors and short computation times, we compare the calculation times involved with both the iterative and ANN methods. An average localization error of about 3.5 mm is obtained for both spherical and realistic head models. Moreover, the ANN localization approach appears to be robust to noise and electrode mislocations. In comparison with the iterative localization, the ANN provides a major speed-up of dipole source localization. We conclude that an artificial neural network is a very suitable alternative for iterative dipole source localization in applications where large numbers of dipole localizations have to be performed, provided that an increase of the localization errors by a few millimetres is acceptable.

Brain↗
PubMed2000

Acute single photon emission computed tomographic study of vagus nerve stimulation in refractory epilepsy.

PURPOSE: Left-sided vagus nerve stimulation (VNS) is an efficacious treatment for patients with refractory epilepsy. The precise mechanism of action remains to be elucidated. Only limited data on VNS-induced changes in regional cerebral blood flow (rCBF) are available. The aim of this study was to investigate rCBF changes during initial VNS with single-photon emission computed tomography (SPECT). METHODS: In 12 patients (8 women, 4 men) with mean age of 32 years and mean duration of epilepsy of 19 years, VNS-induced rCBF changes were studied by means of a 99mTc-ethyl cysteinate dimer activation study with a single-day split-dose protocol before and immediately after initial stimulation. Images were acquired on a triple-head camera with fan-beam collimators and were reconstructed with scatter and attenuation correction. After coregistration to a standardized template, both a semiquantitative analysis using predefined volumes-of-interest (VOIs) as well as voxel-by-voxel analysis of the intrasubject activation were performed. During follow-up, efficacy of VNS in terms of seizure-frequency reduction was studied. RESULTS: The semiquantitative analysis, with reference to the total counts in all VOIs, revealed a significant decrease of activity in the left thalamus immediately after the initial stimulation train. These results agreed with voxel-by-voxel analysis. In our study ipsilateral thalamic hypoperfusion was the most significant finding. Mean frequency of complex partial seizures was reduced from 30 per month before implantation to six per month after implantation. CONCLUSIONS: VNS induces rCBF changes immediately after initial stimulation that can be studied with SPECT. VNS-induced changes in the thalamus may play an important role in suppression of seizures. However, no significant relation between the level of hypoperfusion and subsequent clinical efficacy was found.

Adolescent↗
PubMed1999

Long-term results of vagus nerve stimulation in refractory epilepsy.

Vagus nerve stimulation (VNS) is an adjunctive antiepileptic treatment for patients with refractory epilepsy. Limited information on long-term treatment with VNS is available. The purpose of this paper is to present our experience with VNS with a follow-up of up to 4 years. Twenty-five patients (13 females and 12 males) with refractory partial epilepsy were treated with VNS. The first 15 patients with a mean age of 30 years and a mean duration of epilepsy of 17.5 years have sufficient follow-up for analysis. Mean post-implantation follow-up was 29 months and mean stimulation output 2.25 mA. There was a mean seizure frequency reduction from 14 complex partial seizures (CPS) per month before implantation to 8 CPS per month after implantation (P = 0.0016; Wilcoxon signed-rank rest (WSRT)). The mean maximum CPS-free interval changed from 9 to 312 days (P = 0.0007; WSRT). Six patients were free of CPS for at least one year. In one patient, one antiepileptic drug (AED) was tapered; in 10 patients, AEDs remained unchanged; in four, one adjunctive AED was administered. Side effects occurred in six patients, three of whom required a temporary reduction of output current. Nine patients reported no side effects at all. Treatment with VNS remains effective in the long-term. In this series 4 / 15 (27%) patients with highly refractory epilepsy experienced entirely seizure-free intervals of 12 months or more.

Adolescent↗
PubMed1999

Source localization in refractory partial epilepsy.

In this paper, 51 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum MR (space-occupying: n = 16; atrophic: n = 32; dysplastic: n = 3) were studied. Video-EEG monitoring showed CPS in all patients. In 13 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 12 and medial occipital ictal onset in 1 patient. Interictal and ictal dipole modeling using a spherical head model and realistic electrode coordinates were performed. Spatiotemporal dipole mapping of interictal epileptic discharges revealed two distinct dipole patterns. Patients with lesions located in the medial temporal lobe (n = 41) and medial occipital lobe (n = 2) uniformly presented a dipole with an elevation of more than 15 degrees relative to the axial plane. Eight out of ten patients with extratemporal lesions and 1 patient with a pure neocortical temporal lesion had a less stable dipole with an elevation less than 15 degrees relative to the axial plane. Dipole modeling of epochs of early ictal discharges revealed a striking correspondence with the interictal findings in individual patients. Ictal dipole modeling identified the ictal onset zone correctly when compared with intracranial EEG recordings from bilateral hippocampal depth electrodes in patients with medial temporal seizure onset. Mapping of dipoles on MR images of individual patients facilitated clinical interpretation of the EEG data. Interictal and ictal dipole mapping provided additional and clinically relevant information and may obviate the need for intracranial EEG studies in some surgical candidates for refractory CPS.

Adolescent↗
PubMed1997

Dipole modelling and intracranial EEG recording: correlation between dipole and ictal onset zone.

This study includes 11 patients (3 males, 8 females) with mean age of 29 years (range: 15-42 years) who underwent a presurgical evaluation for refractory complex partial seizures (CPS). In all patients, neuroimaging (1.5 T optimum-MR) demonstrated intracranial structural abnormalities (space-occupying: n = 2; atrophic: n = 8; dysplastic: n = 1) and video-EEG monitoring showed CPS, because of discrepancies in the non-invasive examinations, all underwent additional intracranial EEG monitoring. After tailored resective procedures, all but one patient became seizure free. Mean follow-up was 30 months (range: 12-52 months). Results of intracranial EEG recording were compared with spatiotemporal dipole mapping of interictal and ictal epileptic discharges. Interictal dipole modelling revealed two distinct dipole patterns. Patients with lesions located in the medial temporal lobe uniformly presented a combined dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Patients with extrahippocampal lesions had a less stable dipole with a predominant radial component. Dipole modelling of early ictal discharges revealed a striking correspondence with the interictal findings in individual patients. Elevation of ictal dipoles was always congruent with localisation based on intracranial EEG recordings. Interictal and ictal dipole mapping of medial temporal lobe sources may limit the number of surgical candidates for refractory CPS that need intracranial EEG recording. Whether ictal dipole modelling can be equally useful in extratemporal epilepsy remains to be proven.

Adolescent↗
PubMed1997

Dipole modeling in epilepsy surgery candidates.

PURPOSE: The validity and clinical significance of dipole modeling in epilepsy surgery candidates is not fully established. PATIENTS AND METHODS: Interictal and ictal dipole modeling was performed in 43 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum magnetic resonance imaging (MRI: space-occupying, n = 15; atrophic, n = 26; dysplastic, n = 2). Video-EEG monitoring showed CPS in all patients. In 12 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 11 patients and medial occipital ictal onset in 1. RESULTS: Spatiotemporal dipole mapping of averaged interictal spikes and epochs of early ictal discharges revealed two distinct dipole patterns. Patients with lesions located in the medial (+/-lateral) temporal lobe (n = 34) and medial occipital lobe (n = 1) uniformly presented a combined interictal dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Eight of 9 patients with extratemporal lesions had a less stable dipole with a predominant radial component. Ictal dipole modeling identified the ictal onset zone correctly as compared with intracranial EEG recordings from bilateral hippocampal depth electrodes. Ictal dipoles showed a striking correspondence with the interictal dipoles in individual patients. CONCLUSIONS: Interictal and ictal dipole mapping provided additional, reliable, and relevant localizing information in surgical candidates for refractory CPS. Ictal dipole analysis may limit the number of patients who require intracranial electrodes.

Adolescent↗
PubMed1995

Interictal and ictal dipole modelling in patients with refractory partial epilepsy.

Fifteen patients (7 men, 8 women) with mean age of 34 years and mean duration of refractory partial seizures of 17 years were included in a presurgical evaluation protocol. Neuroimaging (CAT, 1.5 T MR) demonstrated intracranial structural lesions (space-occupying: n = 9; atrophic: n = 6) and video-EEG monitoring showed complex partial seizures in all patients. Four patients underwent additional intracranial EEG monitoring that demonstrated hippocampal seizure onset in all. Voltage topography and spatiotemporal dipole mapping of interictal epileptic discharges revealed two distinct distinct dipole types. Patients with lesions in the medial (and lateral) temporal lobe uniformly presented with a negative voltage field with a steep gradient over the inferior temporal area and a stable, combined dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Patients with extratemporal lesions had a more diffuse, less dipolar voltage field and a corresponding dipole which was less stable and had a predominant radial component. Dipole modelling of epochs of early ictal discharges revealed a striking correspondence with the interictal findings in individual patients. Interictal spike voltage topography and corresponding dipole mapping provided additional and reliable information that was relevant in surgical candidates for refractory partial epilepsy, e.g. by suggesting in some patients that the medial temporal structures were not primarily involved. Ictal dipole modelling revealed concordant results with interictal data. It shows promising but needs further confirmation and validation in a larger patient population with intracranial EEG recordings. Despite intrinsic limitations, spike voltage topography and dipole mapping contributes to a better localisation of the underlying brain source of epileptic discharges.

Adolescent↗