Ictal effects of anticonvulsant medication withdrawal in epileptic patients

Neurologic Care of Forcibly Displaced Persons: Emerging Issues in Neurology

There is a growing number of forcibly displaced persons (FDPs) worldwide. With more than 100 million people forcibly displaced today, there is an urgent mandate to understand the neurologic care needs of this population and how neurologists and other health care workers can most effectively provide that care. In this Emerging Issues in Neurology article, we attempt to (1) define the scope of the problem of providing neurologic care to FDPs, (2) highlight commonly encountered clinical challenges related to neurologic care of FDPs, and (3) provide useful clinical information for neurologists and other clinicians who deliver care to FDPs with neurologic needs. We address the terminology of forcible displacement and how terms may differ across a person's migration journey. Common challenges encountered by FDPs with neurologic needs across settings include loss of support systems, loss of personal health information, language barriers and differing expression of symptoms, differing belief systems, epidemiologic patterns of disease unfamiliar to the clinician, and patients' fear and perceived risks of engaging with health systems. Practical approaches are shared for clinicians who encounter an FDP with a neurologic presentation. Finally, the article discusses many unmet neurologic needs of FDPs, which require significant investment. These include addressing lapses in neurologic care during displacement and understanding the effects of forcible displacement on people with chronic neurologic conditions. Future research and educational resources should focus on improving epidemiologic intelligence for neurologic conditions across geographies, developing curricula for optimizing the neurologic care of FDPs, and evaluating the most appropriate and effective uses of health technologies in humanitarian settings.

Multiple mechanisms shape the relationship between pathway and duration of focal seizures

A seizure's electrographic dynamics are characterized by its spatiotemporal evolution, also termed dynamical 'pathway', and the time it takes to complete that pathway, which results in the seizure's duration. Both seizure pathways and durations have been shown to vary within the same patient. However, it is unclear whether seizures following the same pathway will have the same duration or if these features can vary independently. We compared within-subject variability in these seizure features using (i) epilepsy monitoring unit intracranial EEG (iEEG) recordings of 31 patients (mean: 6.7 days, 16.5 seizures/subject), (ii) NeuroVista chronic iEEG recordings of 10 patients (mean: 521.2 days, 252.6 seizures/subject) and (iii) chronic iEEG recordings of three dogs with focal-onset seizures (mean: 324.4 days, 62.3 seizures/subject). While the strength of the relationship between seizure pathways and durations was highly subject-specific, in most subjects, changes in seizure pathways were only weakly to moderately associated with differences in seizure durations. The relationship between seizure pathways and durations was strengthened by seizures that were 'truncated' versions, both in pathway and duration, of other seizures. However, the relationship was weakened by seizures that had a common pathway, but different durations ('elasticity'), or had similar durations, but followed different pathways ('semblance'). Even in subjects with distinct populations of short and long seizures, seizure durations were not a reliable indicator of different seizure pathways. These findings suggest that seizure pathways and durations are modulated by multiple different mechanisms. Uncovering such mechanisms may reveal novel therapeutic targets for reducing seizure duration and severity.

Focal to bilateral motor seizures in temporal lobe epilepsy during video-EEG monitoring: effects on surgical outcome

The aim of this study was to determine whether the occurrence of focal to bilateral motor seizures in the course of partial drug withdrawal during video-EEG monitoring (FTBMS-M) had a predictive value for seizure recurrence in surgically treated patients with mesial temporal lobe epilepsy (MTLE). We analyzed the outcomes of 59 patients who underwent temporal lobe resection at 12 month postoperative follow up. In total, 48 out of 59 patients were rendered seizure free (81.4%). We analyzed seizure recurrence after surgery with reference to: (i) occurrence of seizures after partial drug withdrawal during video-EEG monitoring (FTBMS-M); (ii) history of secondarily generalized seizures during antiepileptic drug treatment prior to presurgical evaluation (FTBMS-H) and (iii) other possible confounding factors (sex, age, epilepsy duration, side of surgery, presence of hippocampal sclerosis, and history of febrile seizures). We found no differences in the frequency of seizure recurrences between patients with FTBMS-M and patients without FTBMS-M (4/20 vs. 7/39; p = 0.848). Conversely, the frequency of seizure recurrence was significantly higher among the patients with FTBMS-H than among the patients without FTBMS-H (7/20 vs. 4/39; p = 0.021). The predictive value of FTBMS-H for postoperative seizure recurrence was confirmed in logistic regression analysis. We found a statistically significant influence of FTBMS-H on poor outcome after surgery, but not of FTBMS-M or other confounding variables, which suggests that withdrawal seizures do not affect postsurgical seizure control.

Risk of seizure clusters and status epilepticus following rapid and ultra-rapid medication discontinuation during intracranial EEG monitoring

OBJECTIVE

Anti-seizure medications (ASMs) are discontinued in the course of intracranial EEG (iEEG) monitoring for presurgical evaluation. The ASM withdrawal facilitates an emergence of seizures but may also precipitate seizure clusters (SC) and status epilepticus (SE). The aim of this study was to compare the rates of SC and SE during the ultra-rapid withdrawal (URW) and rapid withdrawal (RW) of ASMs during iEEG.

METHODS

We performed a retrospective observational study of all consecutive patients with drug resistant epilepsy who completed iEEG at our comprehensive epilepsy center from 2012-2018. SC was defined as three or more seizures in 24 h with a return to baseline between the events. SE was defined as ≥ 5 min of clinical seizure or ≥ 10 min of ictal electrographic activity or series of seizures with no return to the neurological baseline between the events.

RESULTS

Of 107 patients who completed iEEG with intracranial grid or strip electrodes, 46 (43%) were male. Median age at the time of iEEG was 35.4 years (interquartile range [IQR], 26.4 - 44.9). Ninety patients (84.1%) had all AEDs held on admission, while 16 patients (15%) underwent a rapid taper. The median time to first seizure was 15.1 (8.2 - 22.6) h. Sixty-two patients (57.9%) developed SC, while 10 (9.4%) developed SE. Twenty-six patients (36.1%) with these complications required intravenous lorazepam or other rescue ASMs, while the remaining patients had spontaneous resolution of seizures; intubations were not required. While there were differences in the proportions in patients who experienced SC, SE, or neither in the URW and RW groups, these differences were not significant at the 0.05 alpha level.

SIGNIFICANCE

Ultra-rapid and rapid ASM withdrawal are accompanied by SC and SE the majority of which terminate spontaneously. These data support the use of either approach of the medication taper for seizure provocation in iEEG.

Semiological differences of focal onset bilateral motor (convulsive) seizure between mesial temporal lobe epilepsy and neocortical epilepsy

OBJECTIVE

We investigated the semiology of focal onset bilateral motor (convulsive) seizure (FBMS) in patients with intractable focal epilepsy who underwent epilepsy surgery to understand its value in localizing the origin of the seizure.

METHODS

The study included 20 patients who underwent resective surgery after intracranial video-EEG monitoring (iEEG) with a favorable seizure outcome (Engel class I), and had at least one FBMS during iEEG. The diagnosis was mesial temporal lobe epilepsy (MTLE) for 7 patients and neocortical epilepsy (NE) for 13 patients (lateral temporal lobe, 3; posterior cortex, 6; frontal lobe, 3; perirolandic, 1). Videotaped FBMSs were carefully analyzed.

RESULTS

A generalized tonic phase appeared in all 7 patients with MTLE, but was absent in 6 of the 13 patients with NE (P = .044). Tonic cry was more frequently observed in MTLE than in NE (P = .012). Facial tonicity preceding limb tonicity was more frequently seen in patients with MTLE (P = .001).

CONCLUSION

Notably, patients with MTLE and those with NE showed semiological differences during bilateralization. FBMS includes not only focal to bilateral tonic-clonic seizure but also focal to bilateral clonic seizure.

Focal-to-bilateral motor seizures in temporal lobe epilepsy during video-EEG monitoring: effects on surgical outcome

The aim of this study was to determine whether the occurrence of focal-to-bilateral motor seizures in the course of partial drug withdrawal during video-EEG monitoring (FTBMS-M) had a predictive value for seizure recurrence in surgically treated patients with mesial temporal lobe epilepsy (MTLE). We analyzed the outcomes of 59 patients who underwent temporal lobe resection and had postoperative follow-up from 6 to 58 months. In total, 48 out of 59 patients were rendered seizure free (81.4%). We analyzed seizure recurrence after surgery with reference to: (i) occurrence of seizures after partial drug withdrawal during video-EEG monitoring (FTBMS-M); (ii) history of secondarily generalized seizures during antiepileptic drug treatment prior to presurgical evaluation (FTBMS-H) and (iii) other possible confounding factors (sex, age, epilepsy duration, side of surgery, presence of hippocampal sclerosis, and history of febrile seizures). We found no differences in the frequency of seizure recurrences between patients with FTBMS-M and patients without FTBMS-M (4/20 vs. 7/39; p = 0.848). Conversely, the frequency of seizure recurrence was significantly higher among the patients with FTBMS-H than among the patients without FTBMS-H (7/20 vs. 4/39; p = 0.021). The predictive value of FTBMS-H for postoperative seizure recurrence was confirmed in logistic regression analysis. We found a statistically significant influence of FTBMS-H on poor outcome after surgery, but not of FTBMS-M or other confounding variables, which suggests that withdrawal seizures do not affect post-surgical seizure control.

Seizure pathways change on circadian and slower timescales in individual patients with focal epilepsy

Personalized medicine requires that treatments adapt to not only the patient but also changing factors within each individual. Although epilepsy is a dynamic disorder characterized by pathological fluctuations in brain state, surprisingly little is known about whether and how seizures vary in the same patient. We quantitatively compared within-patient seizure network evolutions using intracranial electroencephalographic (iEEG) recordings of over 500 seizures from 31 patients with focal epilepsy (mean 16.5 seizures per patient). In all patients, we found variability in seizure paths through the space of possible network dynamics. Seizures with similar pathways tended to occur closer together in time, and a simple model suggested that seizure pathways change on circadian and/or slower timescales in the majority of patients. These temporal relationships occurred independent of whether the patient underwent antiepileptic medication reduction. Our results suggest that various modulatory processes, operating at different timescales, shape within-patient seizure evolutions, leading to variable seizure pathways that may require tailored treatment approaches.

Mesial temporal resection following long-term ambulatory intracranial EEG monitoring with a direct brain-responsive neurostimulation system

OBJECTIVE

To describe seizure outcomes in patients with medically refractory epilepsy who had evidence of bilateral mesial temporal lobe (MTL) seizure onsets and underwent MTL resection based on chronic ambulatory intracranial EEG (ICEEG) data from a direct brain-responsive neurostimulator (RNS) system.

METHODS

We retrospectively identified all patients at 17 epilepsy centers with MTL epilepsy who were treated with the RNS System using bilateral MTL leads, and in whom an MTL resection was subsequently performed. Presumed lateralization based on routine presurgical approaches was compared to lateralization determined by RNS System chronic ambulatory ICEEG recordings. The primary outcome was frequency of disabling seizures at last 3-month follow-up after MTL resection compared to seizure frequency 3 months before MTL resection.

RESULTS

We identified 157 patients treated with the RNS System with bilateral MTL leads due to presumed bitemporal epilepsy. Twenty-five patients (16%) subsequently had an MTL resection informed by chronic ambulatory ICEEG (mean = 42 months ICEEG); follow-up was available for 24 patients. After MTL resection, the median reduction in disabling seizures at last follow-up was 100% (mean: 94%; range: 50%-100%). Nine patients (38%) had exclusively unilateral electrographic seizures recorded by chronic ambulatory ICEEG and all were seizure-free at last follow-up after MTL resection; eight of nine continued RNS System treatment. Fifteen patients (62%) had bilateral MTL electrographic seizures, had an MTL resection on the more active side, continued RNS System treatment, and achieved a median clinical seizure reduction of 100% (mean: 90%; range: 50%-100%) at last follow-up, with eight of fifteen seizure-free. For those with more than 1 year of follow-up (N = 21), 15 patients (71%) were seizure-free during the most recent year, including all eight patients with unilateral onsets and 7 of 13 patients (54%) with bilateral onsets.

SIGNIFICANCE

Chronic ambulatory ICEEG data provide information about lateralization of MTL seizures and can identify additional patients who may benefit from MTL resection.

Drug withdrawal in the epilepsy monitoring unit - The patsalos table

Investigation of possible candidates for epilepsy surgery will usually require inpatient EEG to capture seizures and allow full operative planning. Withdrawal of antiepileptic drugs increases the yield of this valuable diagnostic information and the benefits of this should justify any increase in the risk of harm associated with these seizures This paper outlines our opinion on what would constitute proposed best practice for management of antiepileptic drug (AED) dosing when patients are admitted for monitoring of seizures to an epilepsy monitoring unit (EMU). In the vast majority of cases EMU admissions are safe and, even if seizures occur, will pass off without complication. Previous guidance has concentrated on ensuring practice around technical aspects of EEG monitoring itself and staffing within the unit. In this guidance we aim to outline optimally safe ways of ensuring that EMUs ensure the minimisation of risk to the patients admitted under their care. We propose an algorithm for enhancing the safety of AED withdrawal in VT admissions while ensuring adequate seizure yields. Risk minimisation requires planned management of drug dosing (with reduction if appropriate), provision of adequate rescue medication, and adequate supervision to allow rapid response to generalised seizures. This algorithm is accompanied by a table which uses knowledge of the clinical and pharmacological properties of each AED to ensure dose withdrawal and reduction is timely and safe taking into account the severity and frequency of the individual's seizures.

Focal epilepsies and focal disorders

Electroencephalographic (EEG) investigations are crucial in the diagnosis and management of patients with focal epilepsies. EEG may reveal different interictal epileptiform discharges (IEDs: abnormal spikes, sharp waves). The EEG visibility of a spike depends on the surface area of cortex involved (>10cm²) and the brain localization of cortical generators. Regions generating IEDs (defining the "irritative zone") are not necessarily equivalent to the seizure onset zone. Focal seizures are dynamic processes originating from one or several brain regions (that generate fast oscillations and are called the epileptogenic zone) before spreading to other structures (that generate lower frequency oscillations and are called the propagation zone). Several factors limit the expression of seizures on scalp EEG, such as the area involved, degree of synchronization, and depth of the cortical generators. Different scalp EEG seizure onset patterns may be observed: fast discharge, background flattening, rhythmic spikes, sinusoidal discharge, or sharp activity. However, to a large extent EEG changes are linked to seizure propagation. Finally, in the context of presurgical evaluation, the combination of interictal and ictal EEG features is crucial to provide an optimal hypothesis concerning the epileptogenic zone.

Does early postoperative drug regimen impact seizure control in patients undergoing temporal lobe resections?

OBJECTIVE

To evaluate the impact of postoperative antiepileptic drug (AED) load on seizure control in patients who underwent surgical treatment for pharmacoresistant mesiotemporal lobe epilepsy during the first two postoperative years.

PATIENTS AND METHODS

532 consecutive patients (48.7% males and 51.7% females) who underwent surgical treatment for mesiotemporal lobe epilepsy were retrospectively evaluated regarding effects of AED load on seizures control during the first 2 years following epilepsy surgery. We analyzed whether postoperative increases in postoperative AED load are associated with better seizure control in patients initially not seizure free, and if postoperative decreases in postoperative AED load would increase the risk for seizure persistence or recurrence. For statistical analyses, Fisher's exact and Wilcoxon test were applied.

RESULTS

68.9, 64.0 and 59.1% of patients were completely seizure free (Engel Ia) at 3, 12 and 24 months after surgery, respectively. Patients in whom daily drug doses were increased did not have a higher rate of seizure freedom at any of the three follow-up periods. Of 16 patients achieving secondary seizure control at 12 months after surgery, only one did so with an increase in drug load in contrast to 15 patients who experienced a running down of seizures independent of drug load increases. Decreases in drug load did not significantly increase the risk for seizure recurrence. Of postoperatively seizure free patients at 3 months after surgery in whom AED were consequently reduced, 85% remained completely seizure free at 1 year and 76% at 1 year after surgery, respectively, as opposed to 86% each when AED was not reduced (differences n.s.). Mean daily drug load was significantly lower in seizure free patients at 12 and 24 months compared to patients with ongoing seizures.

CONCLUSION

In this large patient cohort stratified to the epilepsy syndrome neither did a postoperative reduction in drug load significantly increase the risk for seizure relapse nor did increases in drug dosages lead to improved seizure control. Mean drug load was on average lower in seizure free- than non-seizure free patients at 12 and 24 months of follow-up. Secondary seizure control after initial postoperative seizures in > 90% of cases occurred as a running down, independent of an AED increase. Thus, the effect of the surgical intervention rather than the postoperative drug regimen was the key determinant for seizure control. This finding supports a curative role of temporal lobe surgery rather than an effect rendering the majority of patients' pharmacoresponsive with a critical role of the antiepileptic drug regime for seizure control.

Effect of partial drug withdrawal on the lateralization of interictal epileptiform discharges and its relationship to surgical outcome in patients with hippocampal sclerosis

OBJECTIVE

To assess changes in the relative lateralization of interictal epileptiform discharges (IEDs) and interictal EEG prognostic value in terms of surgical outcome between periods with full medication (FMP) and reduced medication (RMP) in patients with temporal lobe epilepsy (TLE) associated with hippocampal sclerosis (HS).

METHODS

Interictal scalp EEGs of 43 patients were evaluated for the presence of IEDs separately in a waking state (WS) and sleeping state (SS) during FMP and RMP. In each period, patients were categorized as having unitemporal or bitemporal IEDs. Surgical outcome was classified at year 1 after surgery and at last follow-up visit as Engel I or Engel II-IV; and alternatively as completely seizure-free or not seizure-free.

RESULTS

There were significant changes in relative IED lateralization between FMP and RMP during SS. The representation of patients with unitemporal IEDs declined from 37 (86%) in FMP during SS to 25 (58%) in RMP during SS (p=0.003). At year 1 after surgery, the relative IED lateralization is a predictive factor for surgical outcome defined as Engel I vs. Engel II-IV in both FMP during WS (p=0.037) and during SS (p=0.007), and for surgical outcome defined as completely seizure-free vs. not seizure-free in FMP during SS (p=0.042). At last follow up visit, the relative IED lateralization is a predictor for outcome defined as Engel I vs. Engel II-IV in FMP during SS (p=0.020), and for outcome defined as completely seizure-free vs. not seizure-free in both FMP during WS (p=0.043) and in FMP during SS (p=0.015). When stepwise logistic regression analysis was applied, only FMP during SS was found to be an independent predictor for surgical outcome at year 1 after surgery (completely seizure-free vs. not seizure-free p=0.032, Engel I vs. Engel II-IV p=0.006) and at last follow-up visit (completely seizure-free vs. not seizure-free p=0.024, Engel I vs. Engel II-IV p=0.017). Gender was found to be independent predictor for surgical efficacy at year 1 if the outcome was defined as completely seizure-free vs. not seizure-free (p=0.036).

CONCLUSION

The predictive value of relative IED lateralization with respect to surgical outcome in interictal EEG is present only during FMP; the predictive value decreases with the reduction of AEDs caused by the change of relative IED lateralization.

Withdrawal of antiepileptic drugs during presurgical video-EEG monitoring: an observational study for evaluation of current practice at a referral center for epilepsy

OBJECTIVES

Withdrawal of antiepileptic drugs (AEDs) before and during video-EEG-monitoring is commonly implemented to reduce time needed to register a sufficient number of seizures during presurgical evaluation. There are, however, few guidelines regarding withdrawal rate and observation time.

MATERIAL AND METHODS

We performed an observational study including sixty patients admitted to the national Norwegian epilepsy centre and registered tapering of AEDs and their effect on seizure rate and possible complications.

RESULTS

The mean daily seizure rate before admission to the EMU was 0.4 (range 0.02-4) increasing to 1.1 (range 0-8) at the EMU. 29 patients (48%) followed a slow tapering rate whereas 31 (52%) had an intermediate tapering rate. There was no significant difference between the patients with a daily seizure rate during LTM of more or <0.7 seizures per day, an increase of seizure frequency from habitual to during LTM of more or <3.3 or 6.9 with regard to rate of tapering (slow vs intermediate) etiology or AED monotherapy vs polytherapy. Twenty-six patients (43%) had a sufficient number of seizures registered within 3 days to conclude regarding the presurgical evaluation. Two patients received escape treatment while 25 patients did have 24 h-seizure-clusters. There was no serious event.

CONCLUSIONS

Less than 50% of the patients got a sufficient number of seizures for a conclusive result within 3 days. An increase in the registration period could increase the number of successful registrations.

Does the patient's hand hold the key to preventing secondary generalization in mesial temporal lobe epilepsy?

This study aimed to analyze the impact of ictal dystonic posturing (DP) in postoperative seizure outcome and to assess the influence of DP in generalized tonic-clonic seizure (GTCS) occurrence during video-EEG monitoring of patients with temporal lobe epilepsy with mesial temporal sclerosis. The impact of DP on surgical outcome remains controversial. Moreover, DP has been recently associated with brain networks avoiding GTCS occurrence. Five hundred twenty-seven seizures of 171 patients who were submitted to standard anterior temporal lobectomy (ATL) between 2002 and 2010, with at least one year of post-surgical follow-up, were retrospectively analyzed and classified as with or without DP and as evolving or not to GTCS. The ictal semiologic correlates of DP, timing elapsed since precedent seizure and antiepileptic drug (AED) intake before each seizure were evaluated. Seizure outcome after ATL was assessed according to Engel's scale. Fifty-eight out of 171 patients (34%) exhibited ictal DP, of which 91.5% were always unilateral and contralateral to the operated side. DP was related to shorter seizures (p=0.007) and a much lower likelihood of the seizure evolving to GTCS (p=0.001), even during AED withdrawal (p=0.002). There was no association between DP and prognosis regarding seizure control as the result of the surgical resection, either in patients with shorter or in those with longer period of follow-up. Our data support the hypothesis that DP reflects a brain network activation that helps avoid GTCS, even during AED withdrawal.

Epileptic seizures: Quakes of the brain?

A dynamical analogy supported by five scale-free statistics (the Gutenberg-Richter distribution of event sizes, the distribution of interevent intervals, the Omori and inverse Omori laws, and the conditional waiting time until the next event) is shown to exist between two classes of seizures ("focal" in humans and generalized in animals) and earthquakes. Increments in excitatory interneuronal coupling in animals expose the system's dependence on this parameter and its dynamical transmutability: moderate increases lead to power-law behavior of seizure energy and interevent times, while marked ones to scale-free (power-law) coextensive with characteristic scales and events. The coextensivity of power law and characteristic size regimes is predicted by models of coupled heterogeneous threshold oscillators of relaxation and underscores the role of coupling strength in shaping the dynamics of these systems.

Intraoperative hyperventilation vs remifentanil during electrocorticography for epilepsy surgery - a case report

BACKGROUND

Traditionally, intraoperative intracranial electroen-cephalography-recordings are limited to the detection of the irritative zone defined by interictal spikes. However, seizure patterns revealing the seizure onset zone are thought to give better localizing information, but are impractical due to the waiting time for spontaneous seizures. Therefore, provocation by seizure precipitants may be used with the precaution that spontaneous and provoked seizures may not be identical.

OBJECTIVE

We present evidence that hyperventilation induced and drug induced focal seizures may arise from different brain regions in the same patient.

METHODS

Hyperventilation and ultra short acting opioid remifentanil were used separately as intraoperative precipitatants of seizure patterns, while recording from subdural and intraventricular electrodes in a patient with temporal lobe epilepsy. Two different ictal onset zones appeared in response to hyperventilation and remifentanil. Both zones were resected and the patient has remained essentially seizure free for 1 year. Furthermore, this is the first description of hyperventilation used as an intraoperative seizure precipitant in human focal epilepsy.

Effect of medication withdrawal on the interictal epileptiform EEG discharges in presurgical evaluation

Medication withdrawal (MW) is an important method of provoking seizures and activating epileptiform EEG activity during the diagnostic work-up of patients evaluated for epilepsy surgery. Previously it was suggested that MW might influence the seizure-type and activate cortical areas otherwise not producing epileptiform discharges, leading to a false localization of the irritative zone. In order to investigate this we reviewed 42 consecutive cases of MW, of 36 patients, during a 3-year period. We compared seizure frequency, seizure-types and the localization of interictal epileptiform discharges before and after MW. Seizure frequency was significantly higher after MW. In the whole group we found an increase in seizure propagation: the proportion of the complex partial seizures and secondarily generalised seizures increased, while the proportion of the simple partial seizures decreased following MW. In one-third of the patients the interictal EEGs after the MW were different from those recorded before the MW. However, in these discordant cases the EEG findings after the MW (and not before the MW) were concordant with the seizure onset zone and the lesional zone. We conclude that MW is an effective and reliable seizure provoking method, and it does not lead to false localization of the irritative zone.

Interictal spikes on intracranial recording: behavior, physiology, and implications

PURPOSE

The physiological, pathological, and clinical meaning of interictal spikes (IISs) remains controversial. We systematically analyzed the frequency, occurrence, and distribution of IISs recorded from multiple intracranial electrodes in 34 refractory epileptic patients with respect to seizures and antiepileptic drug (AED) changes.

METHODS

Continuous spike counts from all recorded contacts of all implanted electrodes, and also separately for the subset of contacts involved at seizure onset, were tabulated for every hour of every day of recording, and expressed as spikes per hour in six preselected, 24-h intervals (defined to exclude seizures): (1) on medications; (2) prepreseizure; (3) preseizure; (4) postseizure; (5) off meds; and (6) resumed meds. Mean spike rates were analyzed for differences between designated 24-h intervals.

RESULTS

Spike rate in all recorded contacts consistently and significantly decreased after AED withdrawal, despite variability in initial spike rate, diurnal occurrence, seizure character/number/localization of onset, and type(s) of AED continued or withdrawn (p < 0.0001). A significant increase in spike rate was noted in the 24 h after seizures of medial temporal origin, in the medial temporal lobe contacts; neocortical onset seizures did not show any increase.

CONCLUSIONS

These observations confirm and extend previous reports, suggesting a general effect of AED withdrawal, and a more specific effect of medial temporal lobe seizures, on IIS rate. AED mechanisms and efficacy might be demonstrated by quantifying IIS with changes in AEDs. Furthermore, variability in IIS rate after seizures distinguishes localization of seizure onset in medial temporal versus neocortical locations.

Time from ictal subdural EEG seizure onset to clinical seizure onset: an electrocorticographic time factor associated with temporal lobe epileptogenicity

Long-term subdural video/electroencephalographic (EEG) monitoring was performed in a series of patients with medically intractable complex partial seizures, in a study of diagnostic accuracy, to test the hypothesis that the time from ictal subdural EEG seizure onset to clinical seizure onset (ECOT) is correlated with temporal lobe epileptogenicity and confirm measures of validity of ECOT for predicting seizure-free outcome following anterior temporal lobectomy and amygdalohippocampectomy (ATL/AH). In 34 patients with refractory temporal lobe epilepsy, subdural EEG monitoring localized the ictal epileptogenic focus to a single temporal lobe. In each patient, ECOT was analysed for correlation with temporal lobe epileptogenicity as measured by seizure interval in hours. Patients in whom ECOT was equal to or less than the mean (i.e. subdural EEG seizure onset preceding clinical seizure onset by at least 11.7 seconds) had a significantly greater likelihood of becoming seizure-free following ATL/AH compared to patients in whom ECOT was greater than the mean (i.e. subdural EEG seizure onset preceding clinical seizure onset by less than 11.7 seconds) (x(2) = 5.78, p<0.05). The validity of ECOT for predicting seizure-free outcome following ATL/AH is confirmed to have sensitivity of 55.0%, specificity of 85.7%, false positive rate of 15.4%, false negative rate of 42.9%, diagnostic value of 84.6% and diagnostic accuracy of 67.6%. In addition, a significant correlation, described by a second order polynomial relationship, was found between the natural exponential function of ECOT and seizure interval [f(x=0.415x(2) -25.554x + 267.036, r= 0.731, df= 32, t =6.05, p<0.001, where f(x)=e(ECOT) and x= seizure interval). This result provides the epileptologist with a quantitative tool capable of predicting seizure interval based on ECOT. The capability of ECOT to predict seizure interval may allow the patient and epileptologist to anticipate future seizure onset based on ECOT, potentially facilitating accurate timing of ictal seizure focus localization techniques and clinical intervention to abort seizure onset using various available central and peripheral nervous system stimulation therapeutic strategies. The results suggest a relationship between ECOT and seizure interval. Fundamental pathophysiologic processes involved in the transition from ictal EEG to clinical seizure onset may be responsible for temporal lobe epileptogenicity.

Ictal scalp EEG findings in patients with mesial temporal lobe epilepsy

The syndrome of mesial temporal lobe epilepsy (MTLE) is a well-defined clinical entity that responds to surgical treatment in a considerable number of patients. Although it has been subjected to intensive clinical research, few investigators have published the ictal scalp EEG findings and looked for specific features that might predict postoperative outcome. This study was designed to examine ictal scalp EEG characteristics in detail, in a group of patients with pathologically confirmed hippocampal sclerosis (HS). Patients who underwent long-term video-EEG monitoring at our center during a 3-year period and were diagnosed to have MTLE and pathologically proven HS were included in this retrospective study. All ictal scalp EEGs were investigated in a common reference montage, paying attention to the localization, morphology and frequency of ictal discharges that were accepted to represent a specific phase if the findings were sustained for at least 3 seconds. Any significant change in localization, morphology or frequency of discharges was said to represent a different phase. The ictal EEG patterns in different phases were later compared among seizures of different patients. In addition, the ictal EEG characteristics of the patients in Group I (Engel's classification) were compared with the ictal EEG findings in patients who were included in another group. All the patients have been followed for more than 5 years. Seventy-one ictal EEGs were investigated in 25 adult patients (11 M, 14 F). Onset patterns were lateralized in 81.7% and localized in 76% of the seizures. Thirteen different patterns of onset were detected, the most common of which was the cessation of interictal discharges (35.2%). The most common ictal pattern following the initial changes was ipsilateral temporal rhythmic theta-delta activity (85.2%) that occurred on the average 13.4 seconds after onset. Nonlocalized/lateralized seizure onset of all the seizures or bilateral independent onset was present in 75% of the patients in Groups II-III, whereas this ratio was 14.3% in the patients in Group I (p=0.031). In conclusion, ictal scalp EEG in MTLE allows correct lateralization and localization in most of the seizures. Onset patterns may vary considerably; however, a later significant pattern consisting of rhythmic ipsilateral temporal build-up develops in the majority of seizures. Some ictal EEG characteristics may be related to post-operative outcome.

Value and Limitations of Seizure Semiology in Localizing Seizure Onset

Seizure semiology has been the foundation of clinical diagnosis of seizure disorders. This article discusses the value and the limitations of behavioral features of seizure episodes in localizing seizure onset. Studies have shown that some semiologic features of seizures are highly accurate in the hemispheric lateralization and lobar localization of seizures. There is good agreement between blinded reviewers in lateralizing video-recorded seizures in temporal lobe and extratemporal lobe epilepsies. However, seizure semiology alone should not be used to determine the site of seizure onset. Each semiologic feature may falsely localize seizure onset. Seizure semiology in some patients may signify the site of seizure propagation rather than origination. Moreover, seizure semiology may not be as reliable in multifocal epilepsies as it is in unifocal epilepsies. Many semiologic features of seizures of adults are often missing in seizures of children. Seizure semiology should be analyzed and integrated with EEG and neuroimaging data to localize the seizure focus. A sample of the recorded seizures should be shown to the patient's relatives or friends to verify that it is representative of habitual seizures.

Uncontrolled epilepsy following discontinuation of antiepileptic drugs in seizure-free patients: a review of current clinical experience

PURPOSE

We reviewed the impact of planned discontinuation of antiepileptic drugs (AEDs) in seizure-free patients on seizure recurrence and the seizure outcome of reinstituted treatment.

METHODS

A literature review was performed yielding 14 clinical observations of seizure recurrence after discontinuation and its treatment outcome.

RESULTS

Seizure recurrence rate after AED discontinuation ranged between 12 and 66% (mean 34%, 95%CI: 27-43) in the 13 reviewed studies (no data in one study). Reinstitution of AEDs after recurrence was efficacious between 64-91% (mean of 14 studies, 80%, 95%CI: 75-85%) at follow-up. Mean follow-up ranged from 1-9 years. Seizure outcome of resumed treatment was not different for series in children and adolescents (84%, mean of 4 studies, 95%CI: 75-93) or in adults only (80%, mean of 9 studies, 95%CI: 74-86). Although seizure control was regained within approximately one year in half of the cases becoming seizure free, it took some patients as many as 5-12 years. In addition, in 19% (mean of 14 studies, 95%CI: 15-24%), resuming medication did not control the epilepsy as before, and chronic drug-resistant epilepsy with many seizures over as many as five years was seen in up to 23% of patients with a recurrence. Factors associated with poor treatment outcome of treating recurrences were symptomatic etiology, partial epilepsy and cognitive deficits.

CONCLUSIONS

These serious and substantial risks weigh against discontinuation of AEDs in seizure-free patients, except perhaps for selected patients with idiopathic epilepsy syndromes of childhood or patients with rare seizures.

Self-reported Seizure Frequency and Time to First Event in the Seizure Monitoring Unit

PURPOSE

To compare seizure frequency reported in the clinic with time to first diagnostic event during video-EEG monitoring. The effect of the artificial environment of the monitoring unit on self-reported seizure frequency was explored.

METHODS

The 155 consecutive patients were seen in the Washington University Epilepsy Center and subsequently underwent video-EEG monitoring during 2001. Of these, 112 had a diagnostic event during monitoring; 31 left without having a definite event; and 12 could not provide an estimate of seizure frequency in the clinic. The time to first event was compared with self-reported seizure frequency. The patients were then divided into three equal groups (tertiles) based on mean seizure frequency, and time to first seizure was compared between groups. Then the numbers of patients staying >7 days without ever having an event were compared between the low and high seizure-frequency groups. Finally, Kaplan-Meier survival curves were calculated.

RESULTS

No correlation was found between self-reported seizure rate and time to diagnostic event (r= 0.18; p = 0.06). Time to first event was 2.8 days in the low seizure-frequency group (mean, 2.2/month), 2.1 days in the medium (mean, 8.8/month), and 2.1 days in the high (mean, 24.1/month) groups, which were not significantly different (p = 0.19). Of patients in the low-frequency group, 79% had an event within 7 days.

CONCLUSIONS

In the artificial environment of the monitoring unit, self-reported outpatient seizure frequency is not an accurate predictor of duration of video-EEG monitoring required to make a definitive classification of clinical events and should not contribute to the decision as to whether to refer a patient for monitoring.

Epilepsy surgery. Presurgical evaluation

The presurgical evaluation should result in a clear understanding of whether surgery can be undertaken and its associated risks and potential for benefit. The results of surgery are best when there is congruence in the seizure semiology, the irritative zone on interictal EEG, and the ictal onset zone with the epileptogenic lesion as defined on MRI and PET, and when there is a clear understanding of the ictal onset zone's relationship to eloquent cortex as defined by neuropsychologic evaluation, the intracarotid amobarbital test, and cortical functional mapping.

Antiepileptic drug withdrawal in patients with temporal lobe epilepsy undergoing presurgical video-EEG monitoring

PURPOSE

To investigate antiepileptic drug (AED) withdrawal during video-EEG monitoring in adult patients with temporal lobe epilepsy (TLE).

METHODS

Between 1995 and 1997, 102 consecutive patients with refractory TLE were admitted to the epilepsy monitoring unit for presurgical evaluation. Patients were monitored with ongoing AEDs being rapidly decreased and discontinued in 4-6 days. The monitoring was continued until sufficient numbers of seizures were recorded. Serum AED levels were checked at admission and after the first complex partial seizure (CPS).

RESULTS

In all, 89 patients had 429 CPSs (mean, 4.8 per patient), including 156 (36.4%) secondarily generalized. A mean of 153.8 h (16-451 h) was required for completing the monitoring in each patient. Forty-three (48.3%) patients experienced seizure clusters, and eight (9.0%) had generalized seizures that had never occurred or had been absent for years. However, none evolved to status epilepticus. Carbamazepine was the most commonly used AED in 71.9% of patients, followed by valproate and phenytoin. When the first CPS occurred, mean 77.2 h since the beginning of the monitoring, serum levels of these three AEDs were mostly subtherapeutic rather than minimal.

CONCLUSIONS

Acute AED withdrawal effectively provoked seizures in TLE patients undergoing presurgical video-EEG monitoring. However, nearly 50% of patients had seizure clusters or secondarily generalized seizures. Serum AED levels were mostly subtherapeutic when the first CPS occurred.

Increased seizures after discontinuing carbamazepine: results from the gabapentin monotherapy trial

Studies in patients with epilepsy undergoing telemetry evaluation for surgery have suggested that discontinuation of carbamazepine (CBZ) is associated with increased seizures. The period of observation in that setting, however, was limited to a few days. The authors reviewed the occurrence of seizures in patients with epilepsy who had all their antiepileptic medications discontinued during an 8-week period, converted to gabapentin monotherapy, and observed for 26 weeks as part of the gabapentin trial #945-082. Two hundred and seventy-five patients were enrolled. Kaplan-Meier estimates of time to exit for all patients showed that 18% of patients previously treated with CBZ completed the study as compared with 30% of the patients receiving other antiepileptic medications. Increase in the frequency of seizures was maximal in the 2 weeks following CBZ discontinuation. Seizures increased both in frequency and severity but no new seizure types were observed. The findings in this study show that removal of CBZ is associated with increased frequency of seizures in patients with a previous history of epilepsy with incompletely controlled seizures. The period of maximal increase was the first 2 weeks after CBZ discontinuation.

Pediatric epilepsy surgery: neuroimaging, neuropsychology, and anticonvulsants

Neuroimaging and the neuropsychological evaluation are important components of the presurgical evaluation for epilepsy surgery. Advances in neuroimaging over the last decade, to a large part, underlie improvements in pediatric epilepsy surgery outcomes. The neuropsychological evaluation plays an important role in the evaluation of the older child and adolescent, particularly in the evaluation of mesial temporal sclerosis. However, its role in the young child being considered for surgery remains to be defined. This section reviews the definition of medical intractability, issues related to medication withdrawal during video-EEG monitoring, recent neuroimaging advances, and the neuropsychological evaluation.

Electrocorticographic factors associated with temporal lobe epileptogenicity

Continuous subdural electrocorticographic (ECoG) monitoring was performed to test the hypothesis that human temporal lobe epileptogenicity, during long-term monitoring following antiepileptic drug (AED) withdrawal, regardless of the specific AED regimen, is dependent upon ECoG ictal onset and interhemispheric spread of epileptic activity. In 121 patients, ECoG parameters were analyzed for association with seizure frequency, a clinical measure of epileptogenicity. Significantly associated with increased seizure frequency were: ictal medial temporal lobe onset, absence of ictal frontal lobe desynchronization and short interhemispheric propagation time (IHPT). Seizure frequency during long-term ECoG monitoring was not predictive of post-operative seizure outcome. It is concluded that, following AED withdrawal, regardless of the specific AED regimen, increased seizure frequency is associated with medial temporal lobe ictal onset, short IHPT and absence of frontal lobe desynchronization. The results confirm the hypothesis that human temporal lobe epileptogenicity, after withdrawal, is dependent upon ECoG ictal onset and interhemispheric spread of epileptic activity. Future development of procedures which promote ECoG factors associated with increased seizure frequency following AED withdrawal might decrease duration of invasive long-term monitoring and improve efficiency for the pre-surgical selection of temporal lobectomy candidates. Intervention producing ictal frontal lobe desynchronization and increased IHPT might inhibit temporal lobe epileptogenicity and should be evaluated for therapeutic efficacy outside of the long-term monitoring context.

Subacute electrical stimulation of the hippocampus blocks intractable temporal lobe seizures and paroxysmal EEG activities

PURPOSE

To investigate the clinical, electroencephalographic (EEG), and histopathologic effects of subacute electrical stimulation of the hippocampal formation or gyrus (SAHCS) on 10 patients with intractable temporal lobe seizures.

METHODS

Bilateral, depth, hippocampal or unilateral, subdural, basotemporal electrodes were implanted in all 10 patients for a topographic diagnosis of the site and extent of the epileptic focus before a temporal lobectomy. In all patients, antiepileptic drugs (AEDs) were discontinued from 48 to 72 h before a program of continuous SAHCS, which was performed for 2-3 weeks. Stimulation parameters were biphasic Lilly wave pulses, 130/s in frequency, 450 micros in duration, and 200-400 microA in amplitude. The stimuli were delivered 23 of every 24 h for the 2-3-week SAHCS period. The effects of SAHCS on the number of clinical seizures per day and the percentage of interictal EEG spikes per 10-second samples of maximal paroxysmal activity at the epileptic focus were determined daily during the 16 days of SAHCS. At the completion of this program, patients underwent an en bloc temporal lobectomy, and the histopathologic effects of SAHCS on the stimulated tissue were analyzed by means of light-microscopy studies.

RESULTS

In seven patients whose stimulation electrode contacts were placed within the hippocampal formation or gyrus and who experienced no interruption in the stimulation program, SAHCS abolished clinical seizures and significantly decreased the number of interictal EEG spikes at the focus after 5-6 days. The most evident and fast responses were found by stimulating either the anterior pes hippocampus close to the amygdala or the anterior parahippocampal gyrus close to the entorhinal cortex. Other surface, hippocampal, and basotemporal EEG signs predicted and accompanied this antiepileptic response. These included an electropositive DC shift and monomorphic delta activity at the medial hippocampal and parahippocampal regions, and a normalization of the background EEG activity and signs of slow-wave sleep in surface. depth, and subdural regions. In contrast, no evident antiepileptic responses or no responses at all were found in three patients when stimulation was either interrupted or when it was administered outside the hippocampus. Light microscopy analysis of the stimulated hippocampal tissue showed histopathological abnormalities attributable to the depth-electrode penetration damage or to the pial surface reaction to the subdural, Silastic electrode plate. However, no evident histopathological differences were found between the stimulated and nonstimulated hippocampal tissue.

CONCLUSIONS

SAHCS appears to be a safe procedure that can suppress temporal lobe epileptogenesis with no additional damage to the stimulated tissue.

Iatrogenic seizures

This article focuses on the subject of iatrogenic seizures, particularly those that are potentially avoidable. Seizures due to medications, surgical therapy, medical procedures, and diagnostic tests are all examined. Withdrawing antiepileptic drug (AED) therapy from epileptic patients who are undergoing inpatient evaluation for epilepsy surgery is also discussed.

Neuronal complexity loss in temporal lobe epilepsy: effects of carbamazepine on the dynamics of the epileptogenic focus

Analysis methods derived from the theory of non-linear dynamics have been shown to provide new information about the complex spatio-temporal behaviour of neuronal networks involved in temporal lobe epilepsy. To test whether day to day alterations in neuronal complexity are influenced by changes in serum level of carbamazepine (CBZ), a moving-window correlation dimension analysis was applied to electrocorticographic and stereoelectroencephalographic recordings of 10 patients with unilateral temporal lobe epilepsy. Data sets (n = 78) were obtained from interictal states at subsequent days during the presurgical evaluation with strongly variant CBZ serum levels. The so-called neuronal complexity loss L* was used to quantify the change of dimensionality in brain electrical activity recorded under different levels of medication. We found a significant inverse relationship between L* and CBZ serum level spatially restricted to the primary epileptogenic area. This finding can be assumed to reflect the mechanism of action of CBZ attributed to an inhibition of sustained high-frequency firing of bursting neurons.

Negative myoclonic status due to antiepileptic drug tapering: report of three cases

PURPOSE

Epileptic negative myoclonus (ENM) has been increasingly recognized in different epilepsies, but the reasons for its appearance and prognosis remain uncertain. We report 3 patients who developed de novo, almost continuous ENM, triggered by antiepileptic drug (AED) tapering, that resolved with treatment.

METHODS

Three patients aged 16, 19, and 65 years with a 13- to 36-year history of partial epilepsy were receiving a therapeutic dosage of carbamazepine or phenobarbital plus either clobazam (CLB) or valproate (VPA). None had previously had ENM. Forty-eight to 72 h after CLB or VPA withdrawal, the habitual seizures recurred. The patient also began to report repetitive postural lapses of one or more limbs that interfered with eating or writing. At this time, each patient underwent polygraphy with simultaneous surface electromyography (EMG) of deltoid, biceps, and triceps muscles and of the wrist extensor and flexor bilaterally.

RESULTS

In all patients, EEGs demonstrated almost continuous epileptiform discharges whose spatial distribution was similar to that observed before ENM appearance. Polygraphic recordings showed repetitive loss of postural EMG activity in one or more limbs, 100-400 ms in duration, which occurred in conjunction with the spike-waves. One milligram of clonazepam intravenously always terminated ENM status, which has not recurred in the ensuing 9-36 months.

CONCLUSIONS

ENM may emerge as a new type of seizure due to tapering of AED therapy. This effect is possibly related to the great activation of epileptiform activity with consequent interference with cortical activity.

Seizure occurrence during long-term monitoring

PURPOSE

Intensive long-term monitoring (LTM) for patients with refractory seizures is common and expensive. Methods to decrease the length of stay would improve patient experience and reduce cost. Therefore, we prospectively analyzed seizure occurrence in 36 patients who had LTM.

METHODS

Antiepileptic drug (AED) levels and reduction were monitored and seizures were related to these changes. Patients were divided into temporal and extratemporal groups.

RESULTS

Twenty patients had partial seizures of temporal lobe origin. The temporal lobe partial seizures occurred between LTM days 1 and 16. All but 4 of the patients required reduction or discontinuation of a least one AED and had subtherapeutic levels of the tapered medications. In 16 patients with extratemporal partial seizures, seizures occurred between LTM days 1 and 8. Six of these patients required reduction of at least one AED, and 5 of the 6 had subtherapeutic levels of that medication. These differences between length of monitoring and AED reduction in temporal and extratemporal patients were statistically significant. The groups did not differ significantly with respect to number or identity of tapered or nontapered medications or levels of nontapered medications. Reported seizure frequency at home was significantly related to number of seizures recorded in the temporal group only. The only significant predictor of secondarily generalized seizure activity during monitoring was a history of such activity occurring at home.

CONCLUSIONS

We conclude that patients with extratemporal partial seizures need little reduction of AED for seizures to be captured in a minimal time period. Patients with temporal lobe seizures, however, required drastic reduction of AEDs to allow capture of seizures in a long time period.

Prognosis of epilepsy withdrawn from antiepileptic drugs

Antiepileptic drugs (AED) were discontinued in 55 epileptics who had been free from seizures treated with AED, in accordance with the following criteria and procedures. (i) A reduction in AED commences when patients have been free from seizures for at least 2 years and epileptic discharges have also disappeared in repeated electroencephalogram (EEG) recordings during that period. (ii) AED are gradually reduced if no relapse is seen in clinical seizures and epileptic discharges in EEG. (iii) As a rule at least 2 years are required as the interval from the onset of a reduction to the withdrawal of AED. Forty-three patients were followed up by a questionnaire and/or by telephone and the follow-up period from the withdrawal of AED to the survey ranged from 0.9 to 8.8 years; in 38 patients (88.4%) the period was longer than 2 years. No relapse of seizures was found in any of the 43 patients. The severity of epilepsy judged by the total number of frequency of seizures, the presence of neuropsychiatric complications, the combination of different types of seizures, and the duration of epilepsy from the seizure onset to the last seizure appeared not to be risk factors for the recurrence of seizure. Normal EEG was, however, considered to be an important prerequisite for a good prognosis.

Clinical utility of video-EEG monitoring

This study investigated the efficiency of simultaneous video-electroencephalography (EEG) monitoring in documenting paroxysmal events, the value in clinical diagnosis, and the effect on treatment. In this retrospective review, 230 children underwent this procedure between January, 1990 and December, 1992. The data demonstrated that video-EEG monitoring can be used as a daytime procedure with a high success rate (80%) in detecting and differentiating the nature of recurrent paroxysmal behaviors that have occurred on a daily basis. Video-EEG monitoring has a high diagnostic rate in differentiating seizure versus nonseizure events (70%), in classifying seizure types (88%), and in evaluating the candidacy for epilepsy surgery (64%). Video-EEG diagnosis resulted in an alteration of clinical management in 45% of patients. Continuous video-EEG monitoring is an efficient and valuable procedure in the diagnosis and management of paroxysmal disorders in children.

Utility of stereoelectroencephalography in preoperative assessment of temporal lobe epilepsy

Of 269 consecutive patients entered into a preoperative assessment programme for possible surgical treatment of epilepsy, 33 had intracranial recording (SEEG) with combined subdural and depth electrodes for the purpose of localising a suspected temporal site of seizure onset. The findings in these patients are analysed with particular reference to: 1) the criteria of selection for SEEG and their validity; 2) information on SEEG compared with that obtained by less invasive means, including foramen ovale telemetry; 3) information on the use of intracerebral electrodes compared with subdural placements; 4) possible predictors of failure of localisation by SEEG and of surgical outcome. It was concluded that SEEG had usefully contributed to the management of 69% of the patients in whom it was used, establishing a previously unidentified site of seizure onset in 33%, correcting an erroneous localisation in 15%, and establishing inoperability in 21% of patients. No predictors of failure of SEEG or of surgery emerged; thus there was no evidence of unnecessary use of this procedure. Five patients were found with incorrect lateralisation of seizure onset on foramen ovale recording (of a total of 192 foramen ovale telemetries). Localisation of the ictal onset zone either by the distribution of inter-ictal discharges or by the initial ictal changes at subdural electrodes was unreliable, confirming the need for ictal, depth recordings.

Alcohol-related seizures, Part II: Clinical presentation and management

Alcoholism may be society's most devastating problem short of war and malnutrition. Perhaps the most complex and preplexing medical complication of alcoholism is alcohol-related seizures. This article is a collective review designed to provide emergency physicians with an overview of the topic that is pertinent to their clinical practice. Part 1 addressed the pathophysiology, differential diagnosis, and evaluation of alcohol-related seizures. Part 2 focuses on the clinical presentation, management, and disposition. In addition, a classification of alcohol-related seizures is proposed.

Reduction of antiepileptic drug dosage for monitoring epileptic seizures

Eleven epileptic patients, candidates for surgical treatment, were examined in order to localize epileptic foci. The daily doses of antiepileptic drugs (AEDs) were reduced by fifty per cent or less, and the reduced dosages were maintained until a seizure had occurred. The reduction resulted in seizures within five days among all patients, and the number of seizures increased significantly in comparison with the five-day period before AED reduction. The seizures so provoked were typical for each patient, as confirmed by clinical observation and video-EEG telemetry. No status epilepticus or withdrawal psychosis occurred. The AED concentrations at the time of the seizures were generally within the reference values.

Discontinuation of phenytoin, carbamazepine, and valproate in patients with active epilepsy

The effects of discontinuing individual antiepileptic drugs (AEDs) in patients with active epilepsy who are receiving combination therapy have not been studied systematically. We report a double-blind, prospective study of discontinuation of phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA) in 70 patients with chronic active epilepsy. Each drug discontinuation was randomized to one of two relatively fast rates of reduction, and a control group of 25 patients continued with stable therapy. Patients who had CBZ removed had a significant increase in seizures that was maintained for 4 weeks after the end of drug reduction, and 10 of these 23 patients had to restart therapy with CBZ. There was no significant change in seizure numbers in the other groups. Two patients discontinued from VPA had to restart the drug; none had to restart PHT. The optimal rates of reduction of CBZ remain uncertain. There was no evidence for a clinically or temporally distinct burst of "discontinuation seizures" in any group. Any marked increase in seizures always resolved on reintroduction of the discontinued drug.

The evaluation of patients with intractable complex partial seizures

Conceptual advantages, together with advances in both technique and technology, have considerably altered the approach to intractable epilepsy over the past two decades. Appropriate utilization of these advances allows our evaluation of patients with intractable seizures to be much more precise and specific than was once the case and allows us to improve considerably our ability to treat patients with intractable epilepsy. We propose an algorithm for the evaluation and treatment of patients with intractable complex partial seizures. Other forms of intractable epilepsy may benefit from similar diagnostic and therapeutic approaches.

Long-term EEG-video-audio monitoring: detection of partial epileptic seizures and psychogenic episodes by 24-hour EEG record review

Twenty-seven patients with medically refractory paroxysmal disorders underwent EEG-video-audio (EVA) monitoring in an inpatient neurology-neurosurgery unit over 1-15 (mean 8.9) days. Fast visual review of all EEG records (5,784 h) and subsequent analysis of synchronized EVA patterns demonstrated a total of 208 partial epileptic seizures (ES) in 12 individuals and 87 psychogenic episodes (PE) in 15 subjects. Clinical ES lasted 83.3 s on the average and were most frequent from day 7 to 9 of monitoring (42.3%) and during sleep (56.4%). PE were longer in duration (mean 724.5 s), most numerous during the first 2 days of monitoring (41.4%), and occurred exclusively during wakefulness. Subjects with PE signaled (by pressing on a push button) more events (35.6%) than did the individuals with ES (27.9%). Multiple observers raised the proportion of alarms to 69.0% of PE compared to 39.9% of ES. Following the alarm, nurses reached the patients' bedside within a brief time (mean 22.2 s). To differentiate partial ES from PE or to establish the association of these disorders, EVA monitoring is best performed around the clock over a period of 1-2 weeks. The limited number of paroxysmal events, especially ES, signaled by the patients should be considered when designing studies of the effectiveness of pharmacologic, surgical, and other treatments.

Depth electrode investigations in patients with bitemporal epileptiform abnormalities

Fifty-seven patients showing bitemporal independent epileptiform abnormalities on extracranial electroencephalograms (EEGs) in whom the epileptogenic zone could not be localized or lateralized by extracranial EEG and other noninvasive tests were investigated with stereotactic depth electrode recordings. In a majority of 44 patients (77%), seizures originated exclusively or with a strong predominance in one temporal lobe only. Of the remaining 13 patients (23%), 8 had seizures originating independently in either temporal lobe without significant lateralized predominance, and 5 had multiple seizure patterns, which were often diffuse. The patterns of seizure onset as recorded by depth electrodes tended to vary even in the same patient. Electrical stimulation studies and the determination of afterdischarge thresholds were of limited utility for lateralization of seizure onset.

Withdrawal of anticonvulsant drugs in patients free of seizures for two years. A prospective study

We discontinued anticonvulsant drugs in 92 patients who had been free of seizures during two years of treatment with a single drug. All the patients had epilepsy that had previously been untreated, and had been randomly assigned to receive carbamazepine, phenytoin, or sodium valproate. Thirty-one patients relapsed, and 61 remained free of seizures. The mean duration of the follow-up in the patients remaining free of seizures was 35 months (range, 6 to 62). There was no significant difference between the relapse rate among adults (35 percent) and that among children (31 percent). Our results suggest that the number of seizures a patient had before control was achieved, the number of drugs tried as single-drug therapy, and the type of treatment withdrawn all influenced the outcome. Among the various types of seizures, complex partial seizures with secondary generalization carried the worst prognosis. In comparison, the risk of relapse was 65 percent lower in patients with generalized seizures and 97 percent lower in patients with complex or simple partial seizures in the absence of secondary generalized attacks. Among the four electroencephalographic classes, class 4 (abnormal before treatment and unchanged before withdrawal) carried the worst prognosis. The risk of relapse was 94 to 99 percent lower in patients in the other three electroencephalographic classes. Among the three anticonvulsants, withdrawal of sodium valproate carried the worst prognosis. In comparison, the odds of relapsing were 28 percent lower after withdrawal of phenytoin and 85 percent lower after withdrawal of carbamazepine. We conclude that withdrawal of anticonvulsant medication should be considered in patients free of seizures for two years.