Kristl Vonck

Ictal Source localization in presurgical patients with refractory epilepsy

Summary Source localization of epileptic foci using ictal spatiotemporal dipole modeling (ISDM) yields reliable anatomic information in presurgical candidates. It requires substantial resources from EEG and neuroimaging laboratories. The profile and number of patients who may benefit from it are currently unknown. The purpose of this study is to demonstrate the clinical usefulness of source localization in a prospectively analyzed series. One hundred patients (51 male and 49 female patients) with mean age of 31 years (range, 2 to 63 years) and mean duration of refractory epilepsy of 20 years (range, 1 to 49 years) were enrolled consecutively in a presurgical protocol. Ictal EEG was available in 93 patients. ISDM was performed when suitable ictal EEG files were available. The clinical applicability of ISDM was examined in three patients groups: 37 patients in whom ictal EEG recording and MRI were congruent (group I), 30 patients in whom results were not completely congruent but not incongruent (group II), and 26 patients in whom the results were incongruent (group III). ISDM could be performed in 31 of 100 patients: 11 in group I, 8 in group II, and 12 in group III. ISDM influenced decision making in none of the patients in group I, in 4 of 8 patients in group II, and in 10 of 12 patients in group III. Typically, the results of ISDM directed avoiding intracranial EEG recordings in what appeared to be unsuitable candidates for resection by clearly confirming the incongruency between ictal EEG and MRI findings. In this series of 100 presurgical candidates, ictal source localization could be performed in 31% of patients. In 14% of patients, it proved to be a key element in the surgical decision process.

Vagal nerve stimulation--a 15-year survey of an established treatment modality in epilepsy surgery.

Neurostimulation is an emerging treatment for neurological diseases. Electrical stimulation of the tenth cranial nerve or vagus nerve stimulation (VNS) has become a valuable option in the therapeutic armamentarium for patients with refractory epilepsy. It is indicated in patients with refractory epilepsy who are unsuitable candidates for epilepsy surgery or who have had insufficient benefit from such a treatment. Vagus nerve stimulation reduces seizure frequency with > 50% in 1/3 of patients and has a mild side effects profile. Research to elucidate the mechanism of action of vagus nerve stimulation has shown that effective stimulation in humans is primarily mediated by afferent vagal A- and B-fibers. Crucial brainstem and intracranial structures include the locus coeruleus, the nucleus of the solitary tract, the thalamus and limbic structures. Neurotransmitters playing a role may involve the major inhibitory neurotransmitter GABA but also serotoninergic and adrenergic systems. This manuscript reviews the clinical studies investigating efficacy and side effects in patients and the experimental studies aiming to elucidate the mechanims of action.

Increased rat serum corticosterone suggests immunomodulation by stimulation of the vagal nerve

The role of the vagal nerve within the immune system has not been fully elucidated. Vagal afferents connect to several central nervous system structures, including the hypothalamus. We investigated the effect of vagal nerve stimulation (VNS) on serum corticosterone levels in rats. Corticosterone levels were measured following 1 h of high frequency (30 Hz) or low frequency (1 Hz) VNS in awake animals. There was a significant increase (p < 0.05) in serum corticosterone levels following 30 Hz VNS compared to 1 Hz VNS or sham stimulation. These results suggest an immediate effect of VNS on the hypothalamic pituitary-adrenal (HPA) axis and support the role of the vagal nerve in immunomodulation.

Technical aspects of neurostimulation: Focus on equipment, electric field modeling, and stimulation protocols

Neuromodulation is a field of science, medicine, and bioengineering that encompasses implantable and non-implantable technologies for the purpose of improving quality of life and functioning of humans. Brain neuromodulation involves different neurostimulation techniques: transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS), which are being used both to study their effects on cognitive brain functions and to treat neuropsychiatric disorders. The mechanisms of action of neurostimulation remain incompletely understood. Insight into the technical basis of neurostimulation might be a first step towards a more profound understanding of these mechanisms, which might lead to improved clinical outcome and therapeutic potential. This review provides an overview of the technical basis of neurostimulation focusing on the equipment, the present understanding of induced electric fields, and the stimulation protocols. The review is written from a technical perspective aimed at supporting the use of neurostimulation in clinical practice.

Amygdalohippocampal Deep Brain Stimulation (Ah-DBS) for Refractory Temporal Lobe Epilepsy

Four patients had a left-sided focal medial temporal lobe onset. Three patients had a right-sided regional medial temporal lobe onset. One patient had a bilateral regional temporal lobe onset with predominant involvement of the left side. Two patients had a leftsided regional medial temporal lobe onset. Nine out of 10 patients had a >50% reduction of interictal spikes during the initial AH-DBS trial period. In one patient who showed very infrequent spiking, seizure frequency that had significantly decreased, was used as a criterion for implantation. One patient did not meet the chronic implantation criterion and underwent a selective amygdalo-hippocampectomy. Nine out of 10 patients were implanted with an internal generator. The mean follow-up in these patients was 16 months (range: 9–25 months). One patient has been free of complex partial seizures (CPS) for 2 years and has been tapered off 2 anti-epileptic drugs (AEDs). Another patient has become seizure-free in the past 9 months; 3/10 patients have a >50% reduction in seizure frequency; 3/4 patients have been taIntroduction

LP6: Ictal tachycardia in childhood epilepsy

Results: Out of all examined patients with epilepsy and a specific comorbid disease, 916 (56.4%) patients have diffuse changes in the background activity, 32 (2%) patients have generalized paroxysmal activity, 157 (9.6%) patients have disorganized background activity with generalized paroxysmal activity, 591 (32%) of the patients have focal activity. There is a dependency between the EEG changes of some most often encountered somatic and neurological diseases. Conclusions: The presence of comorbid diseases relates to a higher risk for aggravating the condition of the patient, increasing the EEG changes, a presence of interdependence between the separate diseases, as well as between their treatment.

Why does VNS take so long to work

Publisher Summary nThis chapter presents the case of a woman diagnosed with drug-resistant bitemporal lobe epilepsy. In this patient with a long history of medically refractory epilepsy, the efficacy of VNS became evident only after about 5 months of treatment. Large patient series have shown that one-third of patients treated with VNS are nonresponders. This had been discussed with the patient prior to VNS but she was however very disappointed with the initial lack of seizure control. This right-handed 38-year-old female with a history of mild mental retardation developed severe refractory epilepsy with complex partial seizures (CPSs) and secondary generalization at the age of 2. She had been treated with various combinations of antiepileptic drugs (AEDs) including phenytoin, valproate, carbamazepine, gabapentin, primidone, and clonazepam. In July 2001 she was implanted with VNS. The perioperative period was uneventful. The AED regimen remained unchanged. Three months later the patient reported a CPS frequency of < 1 per month. After 2 years of follow-up, the patient reports occasional CPS, about once every 3 months with a markedly reduced postictal period. She also reports occasionally using the magnet when she experiences an aura with a frequency of about one per month. Secondary generalized convulsions have not reoccurred. Side effects have fully resolved. The chapter also includes further comments on the issues brought up in the case.