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The purpose of this paper is to demonstrate the diagnostic efficacy and therapeutic relevance of video-EEG monitoring in an large patient population with long-term follow-up.Between October 1990 and May 1997, 400 patients were monitored at the Epilepsy Monitoring Unit (EMU) of the University Hospital in Gent. In all patients, the following parameters were retrospectively examined: reason for referral, tentative diagnosis, prescribed antiepileptic drugs (AEDs), seizure frequency, number of admission days, number of recorded seizures, ictal and interictal EEG, clinical and electroencephalographic diagnosis following the monitoring session. During follow-up visits at the Epilepsy Clinic, we prospectively collected data on different types of treatment and post-monitoring seizure control.255/400 (64%) patients were referred for refractory epilepsy. 145/400 (36%) patients were evaluated for attacks of uncertain origin. Mean follow-up, available in 225 patients, was 28 months (range: 6-80 months). Mean duration of a single monitoring session was 4 days (range: 2-7 days). Prolonged interictal EEG was recorded in all patients and ictal EEG in 258 (65%) patients. Following the monitoring session, the diagnosis of epilepsy was confirmed in 217 patients. Pseudoseizures were diagnosed in 31 patients (8%). AEDs were started in 19 patients, stopped in 6 and left unchanged in 110. The type and/or number of AEDs was changed in 111 patients. Sixty patients underwent epilepsy surgery. In 48 surgery patients, follow-up data were available, 29 of whom became seizure-free, and 16 of whom experienced a greater than 90% seizure reduction. Vagus nerve stimulation was performed in 11 patients, 2 became seizure-free, and 7 improved markedly. Of the non-invasively treated patients in whom follow-up was available (n = 135), 70 became seizure-free or experienced a greater than 50% reduction in seizure frequency; 51 patients experienced no change in seizure frequency. Outcome was unrelated to the availability of ictal video-EEG recording. In patients with complex partial seizures, seizure control was significantly improved when a well-defined ictal onset zone could be defined during video-EEG monitoring.Prolonged interictal EEG monitoring is mandatory in the successful management of patients with refractory epilepsy. Ictal video-EEG monitoring is very helpful but not indispensable, except in patients enrolled for presurgical evaluation or suspected of having pseudoseizures.

Neurostimulation is an emerging treatment for refractory epilepsy. To date the precise mechanism of action remains to be elucidated. Better insight in the mechanism of action may identify seizure types or syndromes that respond to such a treatment and may guide the search for optimal stimulation parameters and finally improve clinical efficacy. In the past ten years some progress has been made through neurophysiological, neuroanatomical, neurochemical and cerebral blood flow studies in patients and animals undergoing vagus nerve stimulation (VNS). Interesting results have been found in VNS-treated patients that underwent evoked potential measurements, cerebrospinal fluid investigation, neuropsychological testing and PET, SPECT and fMRI testing. Desynchronisation of abnormal synchronous epileptic activity is one of the hypotheses on the mode of action that might primarily be responsible for an anti-seizure effect. There is however increasing evidence from research and clinical observation that VNS might establish a true and long-term anti-epileptic effect. It has been shown that VNS influences neurotransmission in the brain and provokes long-term changes in cerebral blood flow in areas crucial for epileptogenesis such as the thalamus and medial temporal lobe structures. Deep brain stimulation (DBS) for epilepsy has regained interest. Central nervous system structures known to play a key role in the epileptogenic network such as the thalamus and subthalamic nucleus have been targeted. Another approach is to target the ictal onset zone such as the medial temporal lobe. At Ghent University Hospital 10 patients have been treated with long-term amygdalohippocampal DBS. Several hypotheses have been raised for the mechanism of action of DBS for refractory seizures. Seizure reduction may be due to a microlesion caused by electrode insertion or by provoking a reversible functional lesion due to the effect of electrical current on hyperexcitable tissue. Neurophysiological techniques such as evoked potentials monitoring and intraoperative single unit potential recordings may guide correct electrode placement, individual DBS titration and elucidation of the mechanims of action of DBS for epilepsy.

Between January 1992 and June 1995, 160 patients were presurgically evaluated for medically refractory epilepsy by the Epilepsy Monitoring and Surgery Team at the University Hospital of Gent. All these patients underwent a comprehensive presurgical evaluation, including extensive neurological history and examination, video-EEG monitoring of interictal EEG and habitual seizures, CT and optimum MR. In a large subgroup of these patients a comprehensive neuro-psychological examination and interictal 18FDG-PET were performed. After the non-invasive phase of the presurgical evaluation, a bilateral carotid angiography and intracarotid amytal procedure was planned in 27 patients to establish hemispheric language dominance and bilateral memory function. After proper selection, 14 patients underwent invasive video-EEG monitoring with intracranial implantation of parenchymal and/or subdural electrodes to further document the area of seizure onset. From the initial group of 160 potential surgical candidates, 40 patients (20 M, 20 F) with mean age of 31 years (range: 2 months-55 years) and mean duration of uncontrolled seizures of 16 years (range: 2 months-47 years) eventually underwent a surgical procedure. 30/40 patients were on high dose antiepileptic polytherapy. Optimum MR detected structural abnormalities, confined to a limited brain area, in 39 patients. These abnormalities were of space-occupying nature in 21 cases; an atrophic lesion was suspected in 17 patients. Structural abnormalities were most frequently located in the temporal lobe (n = 26) and the frontal lobe (n = 7). Video-EEG monitoring documented complex partial seizures in 32 patients with occasional secondary generalisation in 14. In most of these patients, seizures could be subclassified as being of temporal lobe origin based on clinical and EEG criteria. Two patients had only simple partial seizures. One patient with Sturge-Weber syndrome and a strictly unilateral angioma had hemiconvulsions. A mentally retarded patient with Lennox-Gastaut syndrome had different types of seizures. After non-invasive and invasive exploration, the area of seizure onset could be determined in all patients. Standard or modified temporal lobectomy +/- hippocampectomy were the most commonly performed procedures (n = 26). In 5 patients complete lesionectomies were performed for epileptogenic structural lesions in and outside the temporal lobe. In 2 patients only partial lesionectomies were possible; in 5 patients only biopsies could be performed. Anterior 2/3 callosotomy and hemispherectomy were each performed in one patient. Postsurgical seizure control, after average follow-up of 20 months (range: 6-40 months), was excellent in 27 patients who became seizure-free. In these patients antiepileptic therapy was tapered 2 years after surgery. An additional 4 patients continue to experience non-disabling simple partial seizures only. Patients in whom only biopsies or partial lesionectomies were performed have poor seizure control. Three patients died as a result of the intrinsic malignancy of their space-occupying lesion. Two patients who are seizure free experienced a moderate postoperative hemiparesis with subtotal recovery. Overall quality of life was substantially improved both in patients who became entirely seizure free or who experienced a very significant reduction in seizure frequency. Presurgical evaluation and epilepsy surgery are a labour intensive but rewarding therapeutic alternative for patients with medically refractory epilepsy. Besides providing therapeutic efficacy, comprehensive presurgical evaluation and epilepsy surgery allow for fruitful clinical neurological research.

Between January 1992 and July 1998, 320 patients were presurgically evaluated for medically refractory epilepsy at the University Hospital of Gent. All patients underwent a comprehensive presurgical evaluation, including extensive neurological history and examination, video-EEG monitoring of interictal EEG and habitual seizures, and optimum magnetic resonance (MR). In a large subgroup of these patients, a comprehensive neuropsychological examination and interictal 18FDG-PET were performed. Subsequently, a bilateral carotid angiography and intracarotid amytal procedure (Wada-test) were planned in 49 patients to establish hemispheric language dominance and bilateral memory function. After proper selection, 23 patients underwent invasive video-EEG monitoring with intracranial implantation of parenchymal and/or subdural electrodes to further document the area of seizure onset. From the initial group of 320 potential surgical candidates, 75 patients (42 males, 33 females) with mean age of 29 years (range: 2 months-55 years) and mean duration of uncontrolled seizures of 15 years (range: 2 weeks-38 years) eventually underwent a surgical procedure. Sixty of 75 patients were on high dose antiepileptic polytherapy. Optimum MR detected structural abnormalities, confined to a limited brain area, in 71 patients. These abnormalities were of space-occupying nature in 31 cases; an atrophic lesion was suspected in 39 patients; a combination of space-occupying and atrophic lesion was seen in 1 case. Structural abnormalities were most frequently located in the temporal lobe (n = 53) and the frontal lobe (n = 10). Video-EEG monitoring documented complex partial seizures in 67 patients with occasional secondary generalisation in 32. Most patients had complex partial seizures of temporal lobe as defined by clinical and EEG criteria. Two patients had only simple partial seizures. Ultimately, an area of seizure onset could be determined in all patients. Temporal lobectomy with hippocampectomy was the most commonly performed procedure (n = 42). In 13 patients, complete lesionectomies were performed for epileptogenic structural lesions in and outside the temporal lobe. In 2 patients, only partial lesionectomies were possible; in 5 patients, only biopsies in combination with partial lesionectomies could be performed. Anterior 2/3 callosotomy was performed in 4 patients and hemispherectomy was performed in 2 patients. Postsurgical seizure control, after average follow-up of 50 months (range: 12-98 months), was excellent in 49 patients who became seizure-free. In these patients, antiepileptic therapy was tapered 2 years after surgery. Patients in whom only biopsies or partial lesionectomies were performed have poor seizure control. Epilepsy surgery is a rewarding therapeutic alternative for patients with medically refractory epilepsy. Comprehensive presurgical evaluation and epilepsy surgery provide excellent neurological, neurophysiological, neuropsychological and imaging research opportunities.