Management approaches to prolonged seizures and status epilepticus

Common emergent pediatric neurologic problems

Although there are a variety of neurologic disease processes that the emergency physician should be aware of the most common of these include seizures, closed head injury, headache, and syncope. When one is evaluating a patient who has had a seizure, differentiating between febrile seizures, afebrile seizures, and SE helps to determine the extent of the work-up. Febrile seizures are typically benign, although a diagnosis of meningitis must not be missed. Educating parents regarding the likelihood of future seizures, and precautions to be taken should a subsequent seizure be witnessed, is important. The etiology of a first-time afebrile seizure varies with the patient's age at presentation, and this age-specific differential drives the diagnostic work-up. A follow-up EEG is often indicated, and imaging studies can appropriate on a nonurgent basis. Appropriate management of SE requires a paradigm of escalating pharmacologic therapy, and early consideration of transport for pediatric intensive care services if the seizure cannot be controlled with conventional three-tiered therapy. Closed head injury frequently is seen in the pediatric emergency care setting. The absence of specific clinical criteria to guide the need for imaging makes management of these children more difficult. A thorough history and physical examination is important to uncover risk factors that prompt emergent imaging. Headaches are best approached by assessing the temporal course, associated symptoms, and the presence of persistent neurologic signs. Most patients ultimately are diagnosed with either a tension or migraine headache; however, in those patients with a chronic progressive headache course, an intracranial process must be addressed and pursued with appropriate imaging. Syncope has multiple causes but can generally be categorized as autonomic, cardiac, or noncardiac. Although vasovagal syncope is the most common cause of syncope, vigilance is required to identify those patients with a potentially fatal arrhythmia or with heart disease that predisposes to hypoperfusion. As such, all patients who present with syncope should have an ECG. Additional work-up studies are guided by the results of individual history and physical examination.

Clinical review: status epilepticus

Status epilepticus (SE) has an annual incidence exceeding 100,000 cases in the United States alone, of which more than 20% result in death. Thus, increased awareness of presentation, etiologies, and treatment of SE is essential in the practice of critical care medicine. This review discusses current definitions of SE, as well as its clinical presentation and classification. The recent literature on epidemiology is reviewed, including morbidity and mortality data. An overview of the systemic pathophysiologic effects of SE is presented. Finally, significant studies on the treatment of acute SE and refractory SE are reviewed, including the use of anticonvulsants, such as benzodiazepines, and other drugs.

Intravenous valproate in status epilepticus

OBJECTIVE

To evaluate the role of intravenous valproate sodium (IV VPA) in the treatment of status epilepticus (SE).

DATA SOURCES

A literature search of the English language was performed (MEDLINE 1966-July 2000). Search terms included valproate, valproic acid, and status epilepticus. Bibliographies of articles chosen were reviewed to identify other possible sources.

DATA SYNTHESIS

A review of the medical literature was conducted to evaluate the safety and efficacy of IV VPA in the treatment of SE.

CONCLUSIONS

Experience with IV VPA in the treatment of SE is too limited to recommend its use as a first-line agent. IV VPA may represent a third- or fourth-line option in cases of SE when other agents are ineffective or contraindicated.

Status epilepticus in older patients: epidemiology and treatment options

Status epilepticus (SE) is a medical and neurological emergency that has been associated with significant morbidity and mortality. The most widely accepted definition of SE is more than 30 minutes of either continuous seizure activity, or intermittent seizures without full recovery of consciousness between seizures. SE is a major clinical concern in the elderly population, both because it has increased incidence in the elderly compared with the general population, and because of concurrent medical conditions that are more likely to complicate therapy and worsen prognosis in elderly individuals. The incidence of SE in the elderly is almost twice that of the general population at 86 per 100,000 per year. With the anticipated growth of the elderly population, SE is likely to become an increasingly common problem facing clinicians, and an important public health issue. The elderly have the highest SE-associated mortality of any age group at 38%, and the very old elderly (>80 years of age) have a mortality of at least 50%. Acute or remote stroke is the most common aetiology of SE in the elderly. Nonconvulsive SE (NCSE) has a wide range of clinical presentations, ranging from confusion to obtundation. It occurs commonly in elderly patients who are critically ill and in the setting of coma. Electroencephalogram is the only reliable method of diagnosing NCSE. The goal of treatment for SE is rapid cessation of clinical and electrical seizure activity. Most treatment protocols call for the immediate administration of an intravenous benzodiazepine, followed by phenytoin or fosphenytoin. Recent studies suggest that when this initial treatment of SE fails, little is gained by using additional standard drugs. General anaesthetic agents (such as pentobarbital, midazolam, or propofol) should be expeditiously employed, although these treatments have their own potential complications. Intravenous valproic acid is a recent addition to the armamentarium of drugs for the treatment of SE, with a low risk of hypotension, respiratory depression and hypotension, making it a potentially useful drug for the treatment of SE in the elderly. However, further information is needed to establish its role in the overall treatment of SE.

The etiology and diagnosis of status epilepticus

Status epilepticus (SE) is a common, serious, potentially life-threatening, neurologic emergency characterized by prolonged seizure activity. Generalized convulsive status epilepticus (GCSE) is the most widely recognized form of SE. Direct consequences of convulsive movements from SE can result in injury to the body and brain. Nonconvulsive status epilepticus (NCSE) is underrecognized, with controversy surrounding the consequences and treatment. High mortality rates with GCSE have been noted in the past. New treatments for SE are emerging with new parenteral drug formulations as well as new agents for refractory SE, offering an opportunity to improve outcome. Special drug delivery systems, drug combinations, and neuroprotective agents that prevent the subsequent development of epilepsy may soon emerge as future options for treating SE.

Neurosurgical treatment of medically intractable status epilepticus

Medically intractable status epilepticus can be defined as status epilepticus (SE) that persists or recurs despite medical treatment with intravenous agents that suppress cortical activity. We describe the successful neurosurgical treatment of three patients with medically intractable status epilepticus who responded either to focal resection, multiple subpial transection, or callosal section. The duration of medically intractable status epilepticus before surgery ranged between 23 and 42 days, and multiple medical complications occurred during the failed medical therapy. We suggest that patients with medically intractable status epilepticus who fail to respond to three courses of cerebral suppressant therapy for approximately 2 weeks be considered for surgical treatment in the absence of any known remitting etiology. Focal resection and/or subpial transection is preferred for intractable partial SE with focal electrographic changes or a focal lesion demonstrated by structural or functional neuroimaging. Corpus callosotomy may be used for patients with generalized or non-localizable intractable status epilepticus.

Status epilepticus

Status epilepticus is a medical emergency that requires rapid and vigorous treatment to prevent neuronal damage and systemic complications. Failure to diagnose and treat status epilepticus accurately and effectively results in significant morbidity and mortality. Cerebral metabolic decompensation occurs after approximately 30 min of uncontrolled convulsive activity, and the window for treatment is therefore limited. Therapy should proceed simultaneously on four fronts: termination of seizures; prevention of seizure recurrence once status is controlled; management of precipitating causes of status epilepticus; management of the complications. This article reviews current opinions about the classification, aetiology and pathophysiology of adult generalised convulsive status epilepticus and details practical management strategies for treatment of this life-threatening condition.

Reduced excitatory drive onto interneurons in the dentate gyrus after status epilepticus

Impaired GABAergic inhibition may contribute to the development of hyperexcitability in epilepsy. We used the pilocarpine model of epilepsy to demonstrate that regulation of excitatory synaptic drive onto GABAergic interneurons is impaired during epileptogenesis. Synaptic input from granule cells (GCs), perforant path, and CA3 inputs onto hilar border interneurons of the dentate gyrus were examined in rat hippocampal slices during the latent period (1-8 d) after induction of status epilepticus (SE). Short-term depression (STD) of GC inputs to interneurons induced by brief (500-800 msec), repetitive (5-20 Hz) stimulation, as well as paired-pulse depression at both GC and CA3 inputs to interneurons, were significantly (p < 0.05) enhanced in SE-experienced rats. In contrast, we found no significant differences between SE-experienced and age-matched control rats in the properties of minimal EPSCs evoked at low frequency (0.3 Hz). Consistent with reduced GABAergic inhibition onto granule cells, paired-pulse depression of perforant path-evoked granule cell population spikes was lost in SE-experienced rats. Enhanced STD was partially mediated by group II metabotropic glutamate receptors, because the selective antagonist, 2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid, attenuated STD in SE-experienced rats but had no effect on STD of GC inputs in the normal adult rat. The group II mGluR agonist, (2S',1R',2R',3R')-2-(2,3-dicarboxylcyclopropyl) glycine (1 micrometer), produced a greater depression of GC input to hilar border interneurons in SE-experienced rats than in controls. These results indicate that, in the SE-experienced rat, excitatory drive to hilar border inhibitory interneurons is weakened through a use-dependent mechanism involving group II metabotropic glutamate receptors.

Pharmacokinetics of Phenobarbital During Certain Enhanced Elimination Modalities to Evaluate Their Clinical Efficacy in Management of Drug Overdose

This work was performed to study the pharmacokinetics of phenobarbital during renal clearance enhancement, intestinal clearance enhancement, and a combination of both to determine which method is clinically more effective in the management of drug poisoning. Thirty young patients with phenobarbital overdose were enrolled in the study. They were classified according to the method of treatment to enhance the elimination of phenobarbital into three equal groups: those treated with multiple-dose activated charcoal (MDAC) alone; those treated with urinary alkalinization alone; and those treated with a combination of the two methods. All patients received the required supportive care at the same time as the elimination procedures. Plasma phenobarbital levels were determined on admission and at 6, 12, 18, 24, 30, 36, 42, and 48 hours after admission by the enzyme multiplied immunoassay technique. The results showed that the decrease in plasma phenobarbital levels with MDAC was significantly greater than with either urinary alkalinization or the combined use of both. The results also revealed statistically significant greater total body clearance for phenobarbital and consequently a shorter half-life with MDAC treatment versus either urinary alkalinization alone or the combined use of both. Thus, the authors conclude that the management of drug overdose in the case of weak acidic drugs that have small volumes of distribution should include the sole use of MDAC and supportive care, without urinary alkalinization.

Treatment of status epilepticus

The approach to treatment of status epilepticus has changed because of the demonstration of decreased mortality with rapid intervention, completion of a randomized, double-blind VA Cooperative study comparing first-line agents, and further understanding of the pathophysiologic changes discovered in experimental animal studies. This article reviews the treatments of generalized convulsive status epilepticus in the prehospital, emergency department, and intensive care unit settings.

Current practice in administration and clinical criteria of emergent EEG

Policies of administration and availability of EEG offered during nonbusiness hours vary widely among EEG laboratories. The authors surveyed medical directors of accredited EEG laboratories (n = 84) to determine the ranges of availability and clinical indications for approval of continuously available emergent EEG (E-EEG). Of 46 respondents, 37 (80%) offered E-EEG. Two centers recently lost funding for E-EEG. Availability was not associated with the total number of EEGs performed annually. The mean estimated response time from request to expert interpretation was 3 +/- 4 hours (range, 1-24 hours). The five clinical indications for which most respondents approved E-EEGs were possible nonconvulsive status epilepticus (100%), treatment of status epilepticus (84%), cerebral death exam (81%), diagnosis of convulsive status epilepticus (79%), and diagnosis of coma or encephalopathy (70%). Respondents disagreed widely when asked which clinical situations merited E-EEG, with some approving all requests and others denying all except for nonconvulsive status epilepticus. The wide range of current practice suggests that research focused on outcomes of aggressive, EEG-aided patient evaluation and treatment are needed to define better the costs and benefits of a continuously available EEG service.

[Anesthesia for epilepsy surgery]

Epilepsy is rather common, affecting 0.5 to 2% of the population. Numerous patients, particularly those resistant to the antiepileptic therapy, can be surgically treated after a thorough evaluation. Surgery for epilepsy can be carried out either under general or local anaesthesia with sedation. This second approach is reserved for the extirpation of foci localised in motor, sensory or language areas. During the preoperative anaesthetic evaluation, two specific points have to be taken into account: the psychological aspect and the antiepileptic medication. During the procedure, an electrocorticography with or without stimulation may be indicated, particularly when a perioperative stimulation is scheduled. Low doses of volatile agents are chosen, and no curare and large doses of benzodiazepines and barbiturates. Awakening takes place on the operation table for a rapid and reliable neurological evaluation. During procedures performed under local anaesthesia, the anaesthetist must be ready at any time to intubate the patient in order to secure the airway.

Generalized status epilepticus associated with massive pulmonary aspiration and transient central diabetes insipidus: case report

Status epilepticus causes significant morbidity and mortality. A case of generalized status epilepticus followed by massive pulmonary aspiration, acute respiratory failure and transient central diabetes insipidus is presented. Seizures were promptly controlled, but the patient required mechanical ventilation and correction of polyuria with desmopressin acetate. During hospitalization mental status improved, diabetes insipidus spontaneously remitted and he was discharged without neurologic sequelae. The clinical and pathophysiological features of this case are discussed.

[The difficulty of defining and classifying status epilepticus]

Status epilepticus (SE) can theoretically be described using a simple definition based on physiopathological mechanisms: any seizure of epileptic nature, partial or generalized, convulsive or non-convulsive, lasting over a period of more than 30 minutes; or repeated seizures lasting for a period of over 30 minutes without recovery of consciousness. In the context of a historical review of various definitions, the validity of this definition is assessed and questioned. The heterogeneous nature of this condition is evidenced in daily clinical practice and by the results of epidemiologic studies. In the present study, the authors propose a more pragmatic and heuristic classification, taking into account not only clinical but also electroencephalographic data, as well as the particular nature of the epileptic syndrome when this is known.