Hypersomnolence and narcolepsy; a pragmatic diagnostic neurophysiological approach

Out of a group of 250 consecutive patients who were examined for various disorders of sleep and waking at Ghent University Hospital within a period of 24 months, 30 patients with hypersomnolence associated with a suspected underlying neurological etiology were selected. The population consisted of 15 males and 15 females with mean age of 36 years (range: 16-60 years). Twenty-one patients had had hypersomnolence for more than 2 years. All patients underwent a single night polysomnography (PSG) and a 4-nap multiple sleep latency test (MSLT). PSG was normal in 23 patients. Sleep onset REM period (SOREMP) was defined as the occurrence of REM sleep within 15 min. after initiation of sleep. PSG demonstrated SOREMP's in only 1 patient and showed evidence of obstructive sleep apnea in 4 patients. Two patients had a low sleep efficiency. MSLT demonstrated hypersomnolence in 17 patients of whom 6 showed SOREMP. Significant hypersomnolence was defined as a mean sleep latency < or = 5 min. 4 patients fulfilled the classical clinical and polygraphic criteria (> or = 2 SOREMP) of narcolepsy. In 8 patients the tentative diagnosis of idiopathic CNS hypersomnolence was made. 13 patients did not sleep during MSLT. These results emphasize the relative importance of MSLT. Our limited 4-nap MSLT protocol proved useful in distinguishing narcolepsy from idiopathic CNS hypersomnolence.

Dose-response effect of levetiracetam 1000 and 2000 mg/day in partial epilepsy

PURPOSE

To evaluate the efficacy, dose-response, tolerability, and withdrawal effects of levetiracetam (Keppra) as adjunctive therapy in adult patients with partial epilepsy.

METHODS

In this European multicenter, double-blind, randomized, cross-over trial, levetiracetam 1000 or 2000 mg/day given in two divided doses was compared to placebo as add-on therapy in 324 patients with refractory partial seizures with or without secondary generalization. This trial consisted of six periods: an 8- or 12-week baseline, a treatment period A (4-week titration and 12-week evaluation), a treatment period B (4-week titration and 12-week evaluation), and a withdrawal period. During each evaluation period (A and B), patients received two of the three possible treatment regimens.

RESULTS

This study provides additional information on dose-response effects and withdrawal phenomena and confirms the responder and seizure freedom rates previously reported in the parallel part of the study (Epilepsia 41 (2000) 1179-1186). Both doses of levetiracetam significantly decreased mean partial seizure frequency compared with placebo (P<0.001), and significantly more patients receiving levetiracetam had > or = 50 and > or = 75% reductions in partial seizure frequency (1000 mg, P=0.004 and P=0.043, respectively; 2000 mg P=0.001 and P<0.001, respectively). In addition, 5.5% (10/183) of patients receiving levetiracetam 1000 mg/day and 6.3% (11/175) of patients receiving levetiracetam 2000 mg/day were seizure-free during the corresponding evaluation period, compared with 1.2% (2/172) of patients on placebo. A within-patient comparison revealed a significantly greater responder rate for the higher levetiracetam dose (P=0.018). The most commonly reported adverse effects (> or = 5% and more frequent in one of the groups with levetiracetam) were headache, asthenia, infection, somnolence, pharyngitis, dizziness, and pain. No withdrawal-related adverse events were reported during the cross-titration period.

CONCLUSIONS

Levetiracetam was effective and well-tolerated and decreased seizure frequency in a dose-dependent manner, with no evidence of typical withdrawal-related adverse events or rebound phenomena after withdrawal or down-titration.

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.

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.

Vagus nerve stimulation for refractory epilepsy

Vagus nerve stimulation (VNS) is a neurophysiological treatment for patients with medically or surgically refractory epilepsy. Since the first human implant in 1989, more than 10 000 patients have been treated with VNS. Two randomized controlled studies have shown a statistically significant decrease in seizure frequency during a 12-week treatment period versus a baseline period when 'high stimulation' mode was compared with 'low stimulation' mode. The efficacy appears to increase over time. In general, one third of the patients show a >50% reduction of seizure frequency; one third show a 30-50% seizure reduction, and one third of patients show no response. Few patients become seizure-free. Side effects during stimulation are mainly voice alteration, coughing, throat paraesthesia and discomfort. When studied on a long-term basis, VNS is an efficacious, safe and cost-effective treatment not only in adults but also in children and the elderly. The precise mechanism of action remains to be elucidated. In recent years much progress has been made through neurophysiological, neuroanatomical, neurochemical and cerebral blood flow studies in animals and patients treated with VNS. Further elucidation of the mechanism of action of VNS may increase its clinical efficacy and our general understanding of some physiopathological aspects of epilepsy. Finally, VNS may become an alternative treatment for other conditions such as depression and pain.

The mechanism of action of vagus nerve stimulation for refractory epilepsy: the current status

Vagus nerve stimulation (VNS) is a neurophysiologic treatment for patients with medically or surgically refractory epilepsy. Since the first human implant in 1989, more than 10,000 patients have been treated with VNS. The precise mechanism of action remains to be elucidated. Animal experiments with VNS were initially performed to demonstrate efficacy and safety preceding the clinical trials in human patients. Mechanism of action research involving animal experiments can provide essential clues. Animal experiments are often labor-intensive even in the hands of experienced researchers, however, and the results remain only a reflection of the complicated pathophysiologic systems of the human brain. Mechanism of action research in human patients treated with VNS is particularly challenging because of safety concerns, the large number of patients required, and the heterogeneous nature of various small patient series. This study provides an overview of the progress that has been made in the past 10 years through neurophysiologic, neuroanatomic, neurochemical, and cerebral blood flow studies in animals and patients treated with VNS. Further elucidation of the mechanism of action of VNS may increase its clinical efficacy. It may also provide inspiration for the development of new therapeutic modalities for refractory epilepsy.

Cost minimization analysis of antiepileptic drugs in newly diagnosed epilepsy in 12 European countries

A recent United Kingdom cost minimization analysis (CMA) of four antiepileptic drugs (AEDs) used to treat newly diagnosed adult epilepsy demonstrated that a new drug, lamotrigine (LTG), incurred higher costs than carbamazepine (CBZ), phenytoin (PHT), and valproate (VPA), whose costs were similar. This analysis took account of each drug's side-effect and tolerability profile. The present analysis investigated the costs of treatment with LTG, CBZ, PHT, and VPA in 12 European countries. Data were derived from published sources and from a panel of locally based experts. When no published data were available, estimates were obtained using expert opinion by a consensus method. These data were incorporated into a treatment pathway model, which considered the treatment of patients during the first 12 months after diagnosis. The primary outcome considered was seizure freedom. Randomized controlled trials demonstrate that the drugs considered are equally effective in terms of their ability to achieve seizure freedom, and thus the most appropriate form of economic evaluation is a CMA. These trials provided data on the incidence of side effects, dosages, and retention rates. The economic perspective taken was that of society as a whole and the analysis was calculated on an "intent-to-treat" basis. Only direct medical costs were considered. In each country considered, LTG was twofold to threefold more expensive than the other drugs considered. A sensitivity analysis demonstrated that varying each of the assumptions (range defined by expert panels) did not significantly alter the results obtained.

Day length has a major effect on the response of protein synthesis rates to feeding in growing Japanese quail

We investigated the effect of day length on mixed protein fractional synthesis rates (K(S)) in 14- and 21-d-old Japanese quail (Coturnix c. japonica) habituated to either a long day length, 18 h light/6 h dark (LDL), or short day length, 6 h light/18 h dark (SDL), with free access to food during the light period. Rates of protein synthesis were measured by a flooding dose of L-[1-(13)C]leucine. In both groups, we measured K(S) of pectoral muscle, liver and heart after an overnight period of food deprivation and after 2-h food access at dawn. Rates of protein synthesis were also measured in LDL quail starved for 18 h and refed for 2 h. SDL chicks were smaller and had lower tissue weights at 2 wk of age than did LDL chicks (P<0.05). Starvation led to a lower rate of protein synthesis in those animals starved for 18 h. Food availability after starvation for 18 h induced a significant rise in tissue protein synthesis in both SDL and LDL quail (P<0.05). This increase was absent in LDL quail after a 6-h starvation period. There was an increase in K(S) to ad hoc changes in food supply. By determining the daily period in which feeding can occur, day length has a major effect on protein synthesis rates. This effect will determine the overall growth chicks are able to achieve that have been subjected to different day lengths.

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.

Cobalt-55 positron emission tomography in late-onset epileptic seizures after thrombo-embolic middle cerebral artery infarction

The pathogenesis of late-onset epileptic seizures after thrombo-embolic cerebral infarction is poorly understood. Our previous positron emission tomographic (PET) studies with 15O have demonstrated that post-apoplectic epilepsy is associated with more severe brain ischemia, but we were unable to determine if this was the cause or the consequence of the seizures. Using cobalt-55 (55Co) as PET tracer we can now distinguish recurrent, recent infarction in patients with a previous old infarct in the same vascular territory. In seven out of twelve patients with post-apoplectic seizures an increased uptake of 55Co was observed in the border area and in two of them also within the old infarct core. In the control group, composed of eight seizure-free patients with also an old infarct involving the cortical territory of the middle cerebral artery, no increase in 55Co uptake was observed on PET examination. The present study indicates that in a significant number of patients late-onset epilepsy is the clinical expression of recurrent strokes, occurring in the same vascular territory.

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.

Effect of photoperiod on body weight gain, and daily energy intake and energy expenditure in Japanese quail (Coturnix c. japonica)

Effect of photoperiod and food duration on body weight gain, energy intake, energy expenditure, and sexual development were investigated in two strains of Japanese quail (Coturnix c. japonica), bred for meat (broilers) or egg production (layers), from 7 to 71 days of age. In a first experiment chicks were subjected to 18L:6D, 15L:9D, 12L:12D, 9L:15D, or 6L:18D, with ad lib food during the light period. In a second experiment birds were exposed to a long photoperiod (18L:6D or 15L:9D) with ad lib food during part of the light period (first 6 or 9 h, respectively). Longer photoperiods were associated with larger weight gains. In 18L:6D broilers total body weight gain was 262 g compared to 213 g in 6L:18D broilers. In layers, corresponding values were 182 and 131 g. This effect of photoperiod on weight gain was primarily due to the effect of photoperiod on food availability. The photoperiod below which detrimental effects on weight gain occurred was 9L:15D for both strains. Chicks subjected to 9L:15D or 6L:18D exploited crop filling to enhance energy intake. They also decreased nocturnal metabolic rates to a greater extent compared to levels during the light phase than chicks subjected to light periods of 12 h or more. Sexual maturation was stimulated by photoperiod. At the age of 71 days, eight out of nine females subjected to 18L:6D were producing eggs, but none of the 6L:18D females. It is concluded that changes in feeding behavior and energy expenditure shown under short photoperiods are part of a strategy that allow chicks to gain weight continuously.

Vagus nerve stimulation in refractory epilepsy: SPECT activation study

Left-sided vagus nerve stimulation (VNS) is an efficacious treatment for patients with refractory epilepsy. The exact mechanism of action remains to be elucidated. This study investigated the acute effects of initial VNS in patients with refractory complex partial epilepsy with or without secondary generalization (complex partial seizures [CPS] +/- SG) by means of a perfusion activation study with SPECT.

METHODS

Twelve patients (mean age, 32.2 +/- 10.2 y; age range, 12-47 y) with a mean duration of CPS +/- SG of 19.8 +/- 10.0 y (range, 5-33 y) received VNS. All patients were considered unsuitable candidates for resective surgery because of nonlocalizing findings on presurgical evaluation. VNS efficacy was evaluated for patients with at least 4-mo follow-up. VNS-induced regional cerebral blood flow alterations were studied by a (99m)Tc-ethyl cysteinate dimer activation study with a single-day split-dose protocol before and immediately after an initial stimulation. Images were acquired on a triple-head camera with fanbeam collimators. After coregistration to a standardized template, both a semiquantitative analysis using predefined volumes of interest and a voxel-by-voxel analysis of the intrasubject activation (statistical parametric mapping) were performed.

RESULTS

Seizure-frequency changes ranged from 100% decrease to 0% after VNS. The semiquantitative analysis revealed a consistent decrease of activity in the left thalamus (ratio stimulator on/off = 0.94 +/- 0.04; P = 0.005). These results were concordant with the voxel-by-voxel analysis in which a significant deactivation in the left thalamus was found with spread to the ipsilateral hippocampus. There was no statistically significant correlation between initial VNS-induced thalamic hypoperfusion and seizure reduction at maximum follow-up.

CONCLUSION

Our findings are consistent with the hypothesis that acute VNS reduces seizure onset or propagation through inhibition of the thalamic relay center. Differences with limited H2(15)O PET data may be associated with temporal effects caused by a stimulation-induced local hemodynamic response and need further investigation. SPECT allows study of cerebral physiopathologic effects of vagus nerve electrostimulation in complex partial epilepsy.

Automatic localization of EEG electrode markers within 3D MR data

The electrical activity of the brain can be monitored using ElectroEncephaloGraphy (EEG). From the positions of the EEG electrodes, it is possible to localize focal brain activity. Thereby, the accuracy of the localization strongly depends on the accuracy with which the positions of the electrodes can be determined. In this work, we present an automatic, simple, and accurate scheme that detects EEG electrode markers from 3D MR data of the human head.

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.

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.

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.

The value of the number-needed-to-treat method in antiepileptic drug trials

PURPOSE

There is controversy between clinicians and statisticians on the appropriateness of the number needed to treat (NNT) as a summary statistic to report the effectiveness of a treatment. We examine the two viewpoints and make proposals concerning the reporting of clinical trial results.

METHODS

In the context of antiepileptic treatments, we explain the two different viewpoints and illustrate the use of the odds ratio, relative risk, absolute difference, and NNT on the results of randomized clinical trials with topiramate (TPM). Special attention is paid to the use of these summary statistics in meta-analyses. Here, the NNT is the expected number of patients one would need to treat to achieve a single occurrence of a specified good outcome (e.g., 50% reduction in seizure rate) in comparison to no (or placebo) treatment.

RESULTS

Although the NNT is readily interpretable in some instances, it exhibits undesirable statistical behavior in other cases. In particular, confidence intervals for the NNT may split into two intervals and extend to positive and negative infinity when treatment efficacy is not clearly established by the data. Meta-analyses cannot be sensibly conducted directly on the NNT scale.

CONCLUSIONS

Although other measures, such as the odds ratio, have been more commonly used in the context of meta-analyses, clinicians prefer the NNT because it gives them a clearer clinical interpretation of the effectiveness of a (new) treatment. On the other hand, statisticians do not recognize the value of the NNT, as it has undesirable statistical properties. Some reconciliation between the two views could be achieved when the clinicians acknowledge the weak aspects of the NNT and when statisticians realize that statistical appropriateness is not the same as clinical relevance. It is suggested that the NNT be used as a secondary reporting tool not on an equal footing with the classic scales.

Interictal and ictal video-EEG monitoring

PURPOSE

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.

PATIENTS AND METHODS

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.

RESULTS

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.

CONCLUSION

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.