The performance of the finite difference reciprocity method (FDRM) to solve the inverse problem i... more The performance of the finite difference reciprocity method (FDRM) to solve the inverse problem in EEG dipole source analysis is investigated in the analytically solvable three-shell spherical head model for a large set of test dipoles. The location error for a grid with 2 mm and 3 mm node spacing is in general, not larger than twice the internode distance,
Summary: Purpose: The validity and clinical significance of dipole modeling in epilepsy surgery c... more Summary: 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 ...
Acute Single Photon Emission Computed Tomographic Study of Vagus Nerve Stimulation in Refractory Epilepsy
Epilepsia, 2000
Summary: Purpose: Left‐sided vagus nerve stimulation (VNS) is an efficacious treatment for patien... more Summary: 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 analy...
This study includes 11 patients (3 males, 8 females) with mean age of 29 years (range: 15-42 year... more 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.
Objectives: Few adverse events on heart rate have been reported with vagus nerve stimulation (VNS... more Objectives: Few adverse events on heart rate have been reported with vagus nerve stimulation (VNS) for refractory epilepsy. We describe three cases with intraoperative bradycardia during device testing. Patients and methods: At our hospital 111 patients have received a VNS system. Intraoperative device testing is performed under ECGmonitoring. We reviewed the patients and their VNS-therapy follow-up outcome who experienced a change in heart rate, during device testing (Lead Test). Results: Three patients with medically refractory epilepsy showed a bradycardia during intraoperative Lead Test. Postoperative the VNStherapy started under ECG-monitoring. No change in cardiac rhythm occurred. Subsequent chronic stimulation is uneventful. All three have reduced seizure frequency. Two already have had their second implant, without the occurrence of bradycardia. Conclusion: In case of intraoperative bradycardia VNS-therapy onset should be done under ECG-monitoring. Subsequent chronic stimulation is safe in respect to heart rate. Bradycardia during intraoperative device testing is no reason to abort the operation.
For ageing individuals, declining physical functional capacity can lead to loss of independence, ... more For ageing individuals, declining physical functional capacity can lead to loss of independence, decreased engagement in the community and reductions in quality of life. As such, solutions that can effectively and affordably supplement older adults' diminishing functional capacity, and thus facilitate maintained independence and social participation over time are urgently required. The AXO-SUIT project-funded by the European Commission under the Ambient Assisted Living Joint Programmeis developing assistive exoskeleton devices for older adults with impaired mobilityand/ordifficulties in performingactivities of daily living. This paper will report ongoing research which aims to identify end user needs,and thus provide inputs to specify the design requirements of the AXO-SUIT exoskeletons. The objectives of this initial questionnaire study are to identify the functional assistance requirements of potential end users of the AXO-SUIT in terms of mobility, reaching and handling, and fullbody support for performing activities of daily livingat home and in the wider community. The end user requirements identified will be used to formulate functional specifications for the AXO-SUIT lower-body and upper-body subsystems , which will ensure that the AXO-SUIT prototypes will provide for the specific mobility, reaching and handling needs of end users, and also to provide useful insights into the perspectives and needs of end users in relation to assistive exoskeletons in general.
Vagus nerve stimulation (VNS) is an effective alternative treatment for patients with refractory ... more 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%. Twentynine 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.
Vagus nerve stimulation (VNS) is an established treatment for patients with medically refractory ... more Vagus nerve stimulation (VNS) is an established treatment for patients with medically refractory epilepsy who are unsuitable candidates for conventional epilepsy surgery. VNS requires an initial financial investment but apart from our own previous study there are no reports on cost-benefit published to date. The purpose of this paper is to assess prospectively the cost-benefit ratio of VNS in a series of patients with long term follow-up. Our experience with VNS comprises 25 patients of whom 20 with sufficient follow-up will be further discussed. These 20 patients have a mean post-implantation follow-up of 26 months (range: 6-50 months). Mean age was 30 years (range: 12-45 years); mean duration of epilepsy 17 years (range: 5-35 years). We prospectively assessed seizure frequency, prescribed AEDs, number of hospital admission days and side effects and calculated the epilepsy related direct medical cost and compared this with pre-implantation data. Mean seizure frequency decreased fro...
The performance of the finite difference reciprocity method (FDRM) to solve the inverse problem i... more The performance of the finite difference reciprocity method (FDRM) to solve the inverse problem in EEG dipole source analysis is investigated in the analytically solvable three-shell spherical head model for a large set of test dipoles. The location error for a grid with 2 mm and 3 mm node spacing is in general, not larger than twice the internode distance,
Summary: Purpose: The validity and clinical significance of dipole modeling in epilepsy surgery c... more Summary: 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 ...
Acute Single Photon Emission Computed Tomographic Study of Vagus Nerve Stimulation in Refractory Epilepsy
Epilepsia, 2000
Summary: Purpose: Left‐sided vagus nerve stimulation (VNS) is an efficacious treatment for patien... more Summary: 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 analy...
This study includes 11 patients (3 males, 8 females) with mean age of 29 years (range: 15-42 year... more 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.
Objectives: Few adverse events on heart rate have been reported with vagus nerve stimulation (VNS... more Objectives: Few adverse events on heart rate have been reported with vagus nerve stimulation (VNS) for refractory epilepsy. We describe three cases with intraoperative bradycardia during device testing. Patients and methods: At our hospital 111 patients have received a VNS system. Intraoperative device testing is performed under ECGmonitoring. We reviewed the patients and their VNS-therapy follow-up outcome who experienced a change in heart rate, during device testing (Lead Test). Results: Three patients with medically refractory epilepsy showed a bradycardia during intraoperative Lead Test. Postoperative the VNStherapy started under ECG-monitoring. No change in cardiac rhythm occurred. Subsequent chronic stimulation is uneventful. All three have reduced seizure frequency. Two already have had their second implant, without the occurrence of bradycardia. Conclusion: In case of intraoperative bradycardia VNS-therapy onset should be done under ECG-monitoring. Subsequent chronic stimulation is safe in respect to heart rate. Bradycardia during intraoperative device testing is no reason to abort the operation.
For ageing individuals, declining physical functional capacity can lead to loss of independence, ... more For ageing individuals, declining physical functional capacity can lead to loss of independence, decreased engagement in the community and reductions in quality of life. As such, solutions that can effectively and affordably supplement older adults' diminishing functional capacity, and thus facilitate maintained independence and social participation over time are urgently required. The AXO-SUIT project-funded by the European Commission under the Ambient Assisted Living Joint Programmeis developing assistive exoskeleton devices for older adults with impaired mobilityand/ordifficulties in performingactivities of daily living. This paper will report ongoing research which aims to identify end user needs,and thus provide inputs to specify the design requirements of the AXO-SUIT exoskeletons. The objectives of this initial questionnaire study are to identify the functional assistance requirements of potential end users of the AXO-SUIT in terms of mobility, reaching and handling, and fullbody support for performing activities of daily livingat home and in the wider community. The end user requirements identified will be used to formulate functional specifications for the AXO-SUIT lower-body and upper-body subsystems , which will ensure that the AXO-SUIT prototypes will provide for the specific mobility, reaching and handling needs of end users, and also to provide useful insights into the perspectives and needs of end users in relation to assistive exoskeletons in general.
Vagus nerve stimulation (VNS) is an effective alternative treatment for patients with refractory ... more 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%. Twentynine 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.
Vagus nerve stimulation (VNS) is an established treatment for patients with medically refractory ... more Vagus nerve stimulation (VNS) is an established treatment for patients with medically refractory epilepsy who are unsuitable candidates for conventional epilepsy surgery. VNS requires an initial financial investment but apart from our own previous study there are no reports on cost-benefit published to date. The purpose of this paper is to assess prospectively the cost-benefit ratio of VNS in a series of patients with long term follow-up. Our experience with VNS comprises 25 patients of whom 20 with sufficient follow-up will be further discussed. These 20 patients have a mean post-implantation follow-up of 26 months (range: 6-50 months). Mean age was 30 years (range: 12-45 years); mean duration of epilepsy 17 years (range: 5-35 years). We prospectively assessed seizure frequency, prescribed AEDs, number of hospital admission days and side effects and calculated the epilepsy related direct medical cost and compared this with pre-implantation data. Mean seizure frequency decreased fro...
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Papers by Michel D'havé