Temporary abolition of seizure activity by flumazenil in a case of valproate-induced non-convulsive status epilepticus

Low risk of seizures with slow flumazenil infusion and routine anticonvulsant prophylaxis for high-dose benzodiazepine dependence

High-dose benzodiazepine (BZD) dependence represents an emerging and under-reported addiction phenomenon and is associated with reduced quality of life. To date there are no guidelines for the treatment of high-dose BZD withdrawal. Low-dose slow flumazenil infusion was reported to be effective for high-dose BZD detoxification, but there is concern about the risk of convulsions during this treatment. We evaluated the occurrence of seizures in 450 consecutive high-dose BZD dependence patients admitted to our unit from April 2012 to April 2016 for detoxification with low-dose slow subcutaneous infusion of flumazenil associated with routine anticonvulsant prophylaxis. In our sample, 22 patients (4.9%) reported history of convulsions when previously attempting BZD withdrawal. Only four patients (0.9%) had seizures during ( n = 2) or immediately after ( n = 2) flumazenil infusion. The two patients with seizures during flumazenil infusion were poly-drug misusers. The most common antiepileptic drugs (AEDs) used for anticonvulsant prophylaxis were either valproate 1000 mg or levetiracetam 1000 mg. Our data indicate that, when routinely associated with AEDs prophylaxis, low-dose slow subcutaneous flumazenil infusion represents a safe procedure, with low risk of seizure occurrence.

Drug-induced status epilepticus

Drug-induced status epilepticus (SE) is a relatively uncommon phenomenon, probably accounting for less than 5% of all SE cases, although limitations in case ascertainment and establishing causation substantially weaken epidemiological estimates. Some antiepileptic drugs, particularly those with sodium channel or GABA(γ-aminobutyric acid)-ergic properties, frequently exacerbate seizures and may lead to SE if used inadvertently in generalized epilepsies or less frequently in other epilepsies. Tiagabine seems to have a particular propensity for triggering nonconvulsive SE sometimes in patients with no prior history of seizures. In therapeutic practice, SE is most commonly seen in association with antibiotics (cephalosporins, quinolones, and some others) and immunotherapies/chemotherapies, the latter often in the context of a reversible encephalopathy syndrome. Status epilepticus following accidental or intentional overdoses, particularly of antidepressants or other psychotropic medications, has also featured prominently in the literature: whilst there are sometimes fatal consequences, this is more commonly because of cardiorespiratory or metabolic complications than as a result of seizure activity. A high index of suspicion is required in identifying those at risk and in recognizing potential clues from the presentation, but even with a careful analysis of patient and drug factors, establishing causation can be difficult. In addition to eliminating the potential trigger, management should be as for SE in any other circumstances, with the exception that phenobarbitone is recommended as a second-line treatment for suspected toxicity-related SE where the risk of cardiovascular complications is higher anyways and may be exacerbated by phenytoin. There are also specific recommendations/antidotes in some situations. The outcome of drug-induced status epilepticus is mostly good when promptly identified and treated, though less so in the context of overdoses. This article is part of a Special Issue entitled "Status Epilepticus".

Focal nonconvulsive seizures during detoxification for benzodiazepine abuse

Chronic benzodiazepine (BDZ) abuse is currently treated with detoxification using a low-dose flumazenil infusion, a relatively recently developed and promising procedure. Given the possibility reported in the literature of the occurrence of generalized seizures during therapeutic BDZ detoxification, we usually administer preventive antiepileptic drug (AED) therapy. We describe two patients with no previous history of seizures or evidence of intracerebral lesions who, during detoxification for benzodiazepine abuse, developed repetitive focal nonconvulsive seizures instead of generalized seizures, even with appropriate doses of preventive AED therapy. There are no previous reported cases of focal nonconvulsive seizures occurring during this procedure or, more generally, during abrupt BDZ discontinuation. The cases we describe suggest that during detoxification for BDZ abuse, not only generalized, but also focal nonconvulsive seizures may occur. In this context, the focal seizures probably result from a diffuse decrease in the seizure threshold (caused by a generalized excitatory rebound), which may trigger focal seizures arising from cortical regions with higher intrinsic epileptogenicity. Detoxification for benzodiazepine abuse, even if performed with adequate-dosage AED treatment, may not be as safe a procedure as previously considered, because not only convulsive, but also nonconvulsive seizures may occur and go unnoticed. It is therefore strongly advisable to perform this detoxification under close medical supervision and to maintain a low threshold for EEG monitoring in the event of sudden onset of behavioral changes.

Fatal valproate overdose in a newborn baby

Valproate is a widely used drug in the treatment of epilepsy in children and adults. However, it is not safe for patients under two years of age, especially during the newborn period. This study presents a case of fatal valproate overdose in a 26-day-old female newborn, who is the youngest patient in the literature.

Aggravation of epilepsy by antiepileptic drugs

Antiepileptic drugs may paradoxically worsen seizure frequency or induce new seizure types in some patients with epilepsy. The mechanisms of seizure aggravation by antiepileptic drugs are mostly unknown and may be related to specific pharmacodynamic properties of these drugs. This article provides a review of the various clinical circumstances of seizure exacerbation and aggravation of epilepsy by antiepileptic drugs as well as a discussion of possible mechanisms underlying the occasional paradoxical effect of these drugs. Antiepileptic drug-induced seizure aggravation can occur virtually with all antiepileptic medications. Drugs that aggravate seizures are more likely to have only one or two mechanisms of action, either enhanced gamma-aminobutyric acid-mediated transmission or blockade of voltage-gated sodium channels. Antiepileptic drug-induced seizure exacerbation should be considered and the accuracy of diagnosis of the seizure type should be questioned whenever there is seizure worsening or the appearance of new seizure types after the introduction of any antiepileptic medication.

Use of naloxone in valproic acid overdose: case report and review

We present a case of a mixed ingestion of valproic acid, gabapentin, mexilitine, and ethanol with central nervous system depression that was reversed by naloxone. This report represents the fourth case demonstrating the antidotal efficacy of naloxone in reversing central nervous system depression associated with acute valproic acid overdose. Increasing clinical experience will more fully elucidate indications for, and optimal dosing of, naloxone in valproic acid toxic states.

Absence seizures aggravated by valproic acid

PURPOSE

To report on pediatric patients with absence epilepsy who experienced absence seizure aggravation while receiving valproic acid (VPA).

METHODS

The charts of all children from four pediatric epilepsy clinics receiving VPA for absence epilepsy were reviewed. Patients were evaluated and followed up between 1994 and 2000.

RESULTS

Eight cases (six boys) of absence seizure aggravation were detected. Mean age at seizure onset was 5.8 years (range, 3-12 years). Six patients had simple absence seizures, one had myoclonic absences, and one had absences with automatisms. The electroencephalogram in all cases depicted generalized 3-Hz spike-and-wave activities. All eight patients experienced an increase in the frequency of absence seizures within days of VPA introduction. Dose increments resulted in further seizure aggravation. Serum levels of VPA were within therapeutic range in all patients. No case was attributed to VPA-induced encephalopathy. All patients improved on VPA discontinuation. In five children, VPA was reintroduced, resulting in further seizure aggravation.

CONCLUSIONS

VPA can occasionally provoke absence seizure aggravation in patients with absence epilepsy.

Induction of partial epileptic seizures by flumazenil

PURPOSE

This study addressed the efficacy of flumazenil (FMZ) to induce or activate interictal or ictal epileptic discharges in patients with medically intractable partial epilepsies.

METHODS

Flumazenil, 1 mg, was injected intravenously in 67 patients undergoing presurgical monitoring for epilepsy surgery, 49 of whom had been treated with benzodiazepines (BZDs) before flumazenil was given. Continuous video electroencephalogram (EEG) monitoring with surface or intracranial electrodes was used to evaluate interictal EEG activity, ictal discharges, and the occurrence and semiology of clinically manifest epileptic seizures.

RESULTS

Interictal epileptiform potentials did not change in frequency or distribution after FMZ. In patients not pretreated with BZDs, epileptic seizures could not be provoked. In eight of the 49 patients pretreated with BZDs, epileptic seizures occurred within 30 min of FMZ application. Seizure semiology and regional EEG onset were identical to seizures recorded without FMZ. Patients operated on according to seizure-onset localization with FMZ had a >75% reduction in seizure frequency or became seizure free.

CONCLUSIONS

Seizure induction by FMZ seems to be a valid method for evaluating seizure semiology and localization of the seizure-onset zone during presurgical monitoring of patients with medically intractable localization-related epilepsies.

Paradoxic response to diazepam in complex partial status epilepticus

BACKGROUND

Antiepileptics including benzodiazepines have long been recognized to provoke seizures and precipitate status epilepticus occasionally. This has a special clinical importance in the case of diazepam because of its use as first choice medication in its management. This report is intended to highlight the clinical importance of such a situation.

METHODS

The clinical course of a 28-year old man with complex partial status, which lasted for two months, is described in detail.

RESULTS

Paradoxic response to diazepam was documented under EEG monitoring. A similar response was also noted for midazolam, and had probably contributed in exacerbating and prolonging the duration of status.

CONCLUSION

Paradoxic response to diazepam and midazolam is rare, but may be under-recognized. It should be considered in the setting of refractory status epilepticus.

Nonconvulsive status epilepticus in two patients receiving tiagabine treatment

In the course of an open study on the add-on treatment of tiagabine (TGB) in patients with localization-related epilepsy syndromes, 2 of 9 patients developed nonconvulsive status epilepticus (NCSE) with electroclinical features consistent with those of atypical absence seizures. One patient had never had atypical absence seizures before. In both cases, immediate discontinuation of TGB was followed by complete and sustained electroclinical remission; we suggest a possible causative role of TGB. This observation may be consistent with a paradoxical effect of TGB in selected cases. Possible risk factors and a pathophysiological hypothesis are discussed.

Aggravation of generalized epilepsies

Generalized epilepsies are treatable with a number of antiepileptic drugs (AEDs) that are effective in different seizure types and epilepsy syndromes. The mechanisms of action of these AEDs are incompletely understood but include inhibition of low-threshold calcium currents and of voltage-gated sodium channels and facilitation of GABA(A) receptor currents. The mechanisms of aggravation are also unknown but could include elevation of brain GABA, blockade of voltage-gated sodium channels, and idiosyncratic toxicity reactions. Anecdotal reports suggest that aggravation of generalized epilepsy can occur with virtually all AEDs. The best-documented examples are aggravation of absences by carbamazepine and aggravation of symptomatic generalized epilepsies by vigabatrin. Therefore, the physician must be constantly aware of the problem of aggravation of seizures by AEDs. With careful diagnosis of the epileptic syndrome and an awareness of the problem, aggravation of seizures can be minimized.

Antiepileptic drugs as a cause of worsening seizures

PURPOSE

Although the paradoxical ability of antiepileptic drugs (AEDs) to increase seizure activity has been recognized for decades, the underlying mechanisms are poorly understood and few systematic studies have addressed this problem. This article is intended to provide a critical review of available literature on this topic.

METHODS

Information was collected by means of computerized literature searches, screening of journals and textbooks, and consultation with colleagues. Mechanisms which potentially might precipitate underlying drug-induced exacerbation of seizures were considered based on available pharmacologic and clinical knowledge.

RESULTS

The reviewed information suggests that a paradoxical increase in seizure frequency may occur as a result of at least two separate mechanisms. The first appears to involve a nonspecific manifestation of drug intoxication; seizure-worsening in this context is usually reversible by dosage reduction or elimination of unnecessary polypharmacy. Conversely, the other mechanism may involve a distinct adverse primary action of the drug in specific seizure types or in syndromic forms. Carabamazepine, in particular, has been reported to precipitate or exacerbate a variety of seizures, most notably absence, atonic, or myoclonic seizures in patients with generalized epilepsies characterized by bursts of diffuse and bilaterally synchronous spike-and-wave EEG activity. Phenytoin and vigabatrin also have been implicated in worsening of seizures, particularly generalized seizures, whereas gabapentin has been associated repeatedly with precipitation of myoclonic jerks. Benzodiazepines occasionally have been reported to precipitate tonic seizures, especially when given intravenously to control other seizure types in patients with Lennox-Gastaut syndrome. Seizure deterioration has been reported also with other drugs; though in most cases evidence is still insufficient for meaningful conclusions to be drawn.

CONCLUSIONS

Drug-induced exacerbation of seizures is a serious and common clinical problem that is often unrecognized or overlooked by the treating physician. Its occurrence appears to be related to three possible causes: an incorrect diagnosis of seizure type or syndromic form, lack of knowledge about certain drugs that are contraindicated in specific types of epilepsies, or to prescription of excessive drug dosages and drug combinations. Further studies are required to evaluate the prevalence of this phenomenon of drug-induced exacerbation of seizures, to investigate its mechanisms in greater detail and to characterize additional prognostic factors that may be used for early identification of patients at risk.

Benzodiazepine antagonists reduce epileptiform discharges in rat hippocampal slices

PURPOSE

The antiepileptic effects of benzodiazepine-receptor (BZR) agonists have been well documented. Surprisingly, an antiepileptic effect for the BZR antagonist, flumazenil, has also been described, the mechanism of which is unknown. We investigated the effects of nanomolar concentrations of flumazenil and a structurally dissimilar BZR antagonist, propyl-beta-carboline-3-carboxylate (beta-CCP), on normal synaptic responses and epileptiform discharges induced by a variety of methods in the CA1 region of rat hippocampal slices.

METHODS

Extracellular field potentials were recorded from stratum pyramidale of the CA1 region. Orthodromic stimulation was delivered by a bipolar electrode placed in the stratum radiatum at the border of the CA2/CA3 regions. Drugs were bath applied, and epileptiform discharges were quantified by using the Coastline Bursting Index, which calculates the total length of the discharge waveform of evoked multiple population spikes. For statistical comparisons, we calculated the Coastline Bursting Index for the average of five traces at the end of the control period (20 min), drug application (20 min), and washout (20-40 min).

RESULTS

Flumazenil was without effect on normal synaptic responses; however, flumazenil reduced epileptiform discharges evoked in the presence of high [K+]o, leu-enkephalin, the BZR inverse agonist, methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), or after a cold-shock procedure. beta-CCP exhibited an action similar to that observed for flumazenil, suggesting that the antiepileptic effect is due to properties common to BZR antagonists.

CONCLUSIONS

We suggest that the antiepileptic effect we observed for flumazenil and beta-CCP is mediated at the BZR and might be due to competition with endogenous BZR inverse agonists released preferentially during epileptiform activity.

Negative myoclonus during valproate-related stupor. Neurophysiological evidence of a cortical non-epileptic origin

We retrospectively reviewed clinical and neurophysiological data of 6 epileptic patients who developed negative myoclonus and stupor a few days after introduction of valproate (VPA). Prompt remission of clinical signs and symptoms followed valproate withdrawal. We attempted to elucidate the pathophysiological mechanism of VPA-induced stupor and provide further polygraphic and backaveraging EEG documentation of negative myoclonus. During VPA-induced stupor electroencephalograms revealed posterior background slowing in all patients. Interictal epileptiform discharges were present in 3 patients. In all 6 patients close examination using simultaneous video-polygraphic recording showed negative myoclonus which was not time-related to lateralized spike discharges. In 2 of 3 patients with no spikes on conventional EEG who underwent backaveraged EEG recordings we detected a large (5 microV) cortical positive-negative wave time-locked (30-40 msec) with the postural modification of the contralateral wrist. This cortical potential was similar to that observed in patients with asterixis secondary to metabolic or toxic encephalopathies. In one patient i.v. administration of 10 mg diazepam did not modify this cortical potential and did not reverse the clinical manifestations. In all patients the only abnormal laboratory finding was an increased level of venous ammonemia. Our findings are against an epileptic origin of VPA encephalopathy and provide further argument in favour of a cortical non-epileptic mechanism mediating negative myoclonus. Benzodiazepines should be avoided in the management of this condition.