SEEG-guided RF-thermocoagulation of epileptic foci: a therapeutic alternative for drug-resistant non-operable partial epilepsies.

BACKGROUND: Previous literature includes numerous reports of acute stereotactic ablation for epilepsy. Most reports focus on amygdalotomies or amygdalohippocampotomies, some others focus on various extra-limbic targets. These stereotactic techniques proved to have a less favourable outcome than that of standard surgery, so that their rather disappointing benefit/risk ratio explains why they have been largely abandoned. However, depth electrode recordings may be required in some cases of epilepsy surgery to delineate the best region of cortical resection. We usually implant depth electrodes according to Talairach's stereo electroencephalography (SEEG) methodology. Using these chronically implanted depth electrodes, we are able to perform radiofrequency (RF)-thermolesions of the epileptic foci. This paper reports the technical data required to perform such multiple cortical thermolesions, as well as the results in terms of seizure outcome in a group of 41 patients. TECHNICAL DATA: Lesions are placed in the cortex areas showing either a low amplitude fast pattern or spike-wave discharges at the onset of the seizures. Interictal paroxysmal activities are not considered for planning thermocoagulation sites. All targets are first functionally evaluated using electrical stimulation. Only those showing no clinical response to stimulation are selected for thermolesion, including sites located inside or near primary functional area. Lesions are performed using 120mA bipolar current (50 V), applied for 10-30 sec. Each thermocoagulation produces a 5-7mm diameter cortical lesion. A total of 2-31 lesions were performed in each of the 41 patients. Lesions are placed without anaesthesia. RESULTS: 20 patients (48.7%) experienced a seizure frequency decrease of at least 50% that was more than 80% in eight of them. One patient was seizure free after RF thermocoagulation. In 21 patients, no significant reduction of the seizure frequency was observed. Amongst the characteristics of the disease (age and sex of the patient, lobar localization of the EZ) and the characteristics of the thermocoagulations (topography, lateralization, number, morphology of the lesions on MRI) no factor was significantly linked to the outcome. However, the best results were clearly observed in epilepsies symptomatic of a cortical development malformation (CDM), with 67% of responders in this group of 20 patients (p = 0.052). Three transient post-procedure side-effects, consisting of paraesthetic sensations in the mouth (2 cases), and mild apraxia of the hand, were observed. CONCLUSION: SEEG-guided-RF-thermolesioning is a safe technique. Our results indicate that such lesions can lead to a significant reduction of seizure frequency. Our experience suggests that SEEG-guided RF thermocoagulation should be dedicated to drug-resistant epileptic patients for whom conventional resection surgery is risky or contra-indicated on the basis of invasive pre-surgical evaluation, particularly those suffering from epilepsy symptomatic of cortical development malformation.

[Long-term efficiency of vagus nerve stimulation (VNS) in non-surgical refractory epilepsies in adolescents and adults]. / Efficacité de la stimulation intermittente du nerf vague dans les épilepsies pharmaco-résistantes non chirurgicales de l'adolescent et de l'adulte.

Vagus Nerve Stimulation (VNS) is recognized as an efficient procedure for controlling seizures in patients with drug-refractory epilepsies. It is used as a palliative procedure as a complement to conventional treatment by antiepileptic (AE) drugs and, according to literature, 40 to 50p.cent of patients report a decrease in seizures frequency >or=50p.cent, which is usually accepted to classify patients as responders in add on AE drug trials. The objectives of this study based on retrospective analysis of 50 consecutive patients with partial (39) or generalized (11) refractory epilepsy non eligible for surgery were; firstly to evaluate the global long term VNS efficacy and secondly to identify potential predictors of the VNS effects on seizure frequency. No patient has been seizure free at any moment of the follow up (2.8+/-1.8 years, max: 6 years) and the AE has been maintained in all. During follow up 44, 66, 61 and 58p.cent of patients were classified as responders at 6 months, 1, 2 and 3 years, respectively. Logistic regression analysis showed that: the percentage of responders at 6 months of follow up and later was significantly higher than that before 6 months (p=0.002); generalized epilepsy was predictive of a better outcome as compared to partial epilepsy (p=0.03); there was a trend for a better outcome in partial epilepsies symptomatic of a focal lesion than in those with normal brain MRI (p=0.06). These results are in line with previously published data in terms of global efficiency and confirm that seizures control does not reach its maximal level before at least one year of VNS. In severe generalized epilepsies (either secondary or cryptogenic) manifesting by frequent falls due to atonic or tonic-clonic generalized seizures VNS is a useful palliative procedure, which entails much les of surgical risk than callosotomy. The better VNS effects in patients with partial epilepsy possibly reflect the high incidence in our series of Malformations of Cortical Development, which have been identified as one the few variables possibly predictive of a response over 50p.cent of seizures frequency reduction.

Subthalamic nucleus stimulation in Parkinson's disease : anatomical and electrophysiological localization of active contacts.

OBJECTIVES: 1 - To assess the anatomical localization of the active contacts of deep brain stimulation targeted to the subthalamic nucleus (STN) in Parkinson's disease patients. 2 - To analyze the stereotactic spatial distribution of the active contacts in relation to the dorsal and the ventral electrophysiologically-defined borders of the STN and the stereotactic theoretical target. METHODS: Twenty-eight patients underwent bilateral high-frequency stimulation of the STN (HFS-STN). An indirect anatomical method based on ventriculography coupled to electrophysiological techniques were used to localize the STN. Clinical improvement was evaluated by Unified Parkinson's Disease Rating Scale motor score (UPDRS III). The normalized stereotactic coordinates of the active contact centres, dorsal and ventral electrophysiologically-defined borders of the STN were obtained from intraoperative X-rays images. These coordinates were represented in a three-dimensional stereotactic space and in the digitalized atlas of the human basal ganglia. RESULTS: HFS-STN resulted in significant improvement of motor function (62.8%) in off-medication state and levodopa-equivalent dose reduction of 68.7% (p < 0.05). Most of the active contacts (78.6%) were situated close to (+/- 1.6 mm) the dorsal border of the STN (STN-DB), while 16% were dorsal and 5.4% were ventral to it. Similar distribution was observed in the atlas. The euclidean distance between the STN-DB distribution center and the active contacts distribution center was 0.31 mm, while the distance between the active contacts distribution center and the stereotactic theoretical target was 2.15 mm. Most of the space defined by the active contacts distribution (53%) was inside that defined by the STN-DB distribution. CONCLUSION: In our series, most of the active electrodes were situated near the STN-DB. This suggests that HFS-STN could influence not only STN but also the dorsal adjacent structures (zona incerta and/or Fields of Forel).

The timing of antiparkinsonian treatment reduction after subthalamic nucleus stimulation.

The objective of this work was to precisely analyse the reduction of the antiparkinsonian treatment in 18 consecutive patients with Parkinson's disease (PD) operated on for bilateral subthalamic nucleus (STN) stimulation, first after 1 month of follow-up, then at 1 year postoperatively. Trihexyphenidyle, selegiline, entacapone, apomorphine and lisuride could be withdrawn shortly after starting STN electrical stimulation. The levodopa mean daily dose was reduced by 57% at 1 month after surgery and remained stable at 1 year. The mean ropinirole and bromocriptine daily dose decrements after surgery corresponded to 54 and 63%, respectively, at 1 month and to 77 and 40% at 1 year. At 12 months postoperatively, one third of the patients no longer received any antiparkinsonian drugs and the others were on monotherapy of either levodopa or dopamine agonists or received a combined treatment of a dopaminergic agonist and levodopa. In conclusion, STN stimulation allows a major reduction and simplification of antiparkinsonian treatment which can usually be achieved during the early postoperative period.

Subthalamic nucleus stimulation in Parkinson's disease: clinical evaluation of 18 patients.

The aim of the present study was to assess the efficacy and safety of chronic subthalamic nucleus deep-brain stimulation (STN-DBS) in patients with Parkinson's disease (PD). 18 consecutive severely affected PD patients were included (mean age, SD: 56.9+/-6 years; mean disease duration: 13.5+/-4.4 years). All the patients were evaluated clinically before and 6 months after the surgical procedure using the Unified Parkinson's Disease Rating Scale (UPDRS). Additionally, a 12 months follow-up was available in 14 patients. The target coordinates were determined by ventriculography under stereotactic conditions, followed by electrophysiology and intraoperative stimulation. After surgery, continuous monopolar stimulation was applied bilaterally in 17 patients at 2.9+/-0.4 V through 1 (n = 31) or 2 contacts (n = 3). One patient had bilateral bipolar stimulation. The mean frequency of stimulation was 140+/-16 Hz and pulse width 68+/-13 micros. Off medication, the UPDRS part III score (max = 108) was reduced by 55 % during on stimulation (score before surgery: 44.9+/-13.4 vs at 6 months: 20.2+/-10; p < 0.001). In the on medication state, no difference was noted between the preoperative and the postoperative off stimulation conditions (scores were respectively: 17.9+/-9.2 and 23+/-12.6). The severity of motor fluctuations and dyskinesias assessed by UPDRS IV was reduced by 76 % at 6 months (scores were respectively: 10.3+/-3 and 2.5+/-3; p < 0.001). Off medication, the UPDRS II or ADL score was reduced by 52.8 % during on stimulation (26.9+/-6.5 preop versus 12.7+/-7 at 6 months). The daily dose of antiparkinsonian treatment was diminished by 65.5 % (levodopa equivalent dose -- mg/D -- was 1045 +/- 435 before surgery and 360 +/- 377 at 6 months; p < 0.01). These results remained stable at 12 months for the 14 patients studied. Side effects comprised lower limb phlebitis (n = 2), pulmonary embolism (n = 1), depression (n = 6), dysarthria and freezing (n = 1), sialorrhea and drooling (n = 1), postural imbalance (n = 1), transient paresthesias and dyskinesias. This study confirms the great value of subthalamic nucleus stimulation in the treatment of intractable PD. Some adverse events such as depression may be taken into account in the inclusion criteria and also in the post-operative outcome.

Precentral cortex stimulation for the treatment of central neuropathic pain: results of a prospective study in a 20-patient series.

The authors report a series of 23 patients with central neuropathic pain who were treated with the recently developed technique of precentral cortex stimulation (PCS). Of the 20 patients with a follow-up of more than 1 year (mean of 23 months) 25% had an excellent, 35% a good and 15% a fair relief of pain. In 25% the method failed. On the basis of these findings and the literature data (127 reported cases), the authors advocate PCS in patients with severe and medically refractory poststroke pain.