Status epilepticus is a neurological emergency requiring immediate evaluation and management to prevent significant morbidity or mortality. Previously, status epilepticus was defined as a seizure with a duration equal to or greater than 30 minutes, or a series of seizures in which the patient does not regain normal mental status between seizures. The Neurocritical Care Society guidelines from 2012 revised the definition to a seizure with 5 minutes or more of continuous clinical and/or electrographic seizure activity, or recurrent seizure activity without recovery between seizures.
Status epilepticus may be convulsive, non-convulsive, focal motor, myoclonic and any of these can become refractory. Convulsive status epilepticus consists of generalized tonic-clonic movements and mental status impairment. Non-convulsive status epilepticus is defined as seizure activity identified on an electroencephalogram (EEG) with no accompanying tonic-clonic movements. Focal motor status epilepticus involves the refractory motor activity of a limb or a group of muscles on one side of the body with or without loss of consciousness. Myoclonic status epilepticus Refractory status epilepticus refers to continuing seizures (convulsive or non-convulsive) despite the administration of appropriate anti-epileptic drugs.
There are multiple etiologies for status epilepticus. Potential acute processes include:
Chronic processes that may result in status epilepticus include pre-existing epilepsy with breakthrough seizures or non-compliance with anti-epileptic drugs, ethanol withdrawal, CNS tumors, and remote CNS pathology (e.g., traumatic brain injury, stroke).
Acute processes account for most cases of status epilepticus in adults. Febrile status epilepticus is the most common cause in pediatric patients. CNS infections and inborn errors of metabolism are also common etiologies in children. The majority of pediatric patients with the first presentation of status epilepticus have no previous history of seizures.
The incidence of status epilepticus has a bimodal age distribution with peaks during infancy and in the elderly. The incidence rate ranges between approximately 7 to 40 cases per 100,000 persons/year. Status epilepticus seems to be more common in males. A significant proportion of both children (16% to 38%) and adults (42% to 50%) with status epilepticus have a history of epilepsy. The short-term mortality (within 30 days) of status epilepticus ranges from 7.6% to 22% across all age groups and is highest amongst the elderly.
A seizure is a paroxysmal electrical discharge of neurons in the brain resulting in a change of function or behavior. It is important to understand that a seizure is a CNS event and may present as convulsive or non-convulsive. There are both excitatory neurotransmitters (glutamate, aspartate, and acetylcholine) and inhibitory neurotransmitters (gamma-aminobutyric acid) and mechanisms (calcium ion-dependent potassium ion current and magnesium blockade of N-methyl-d-aspartate (NMDA)) in the brain that play a role in the genesis and inhibition of isolated seizures. Excessive excitation and/or inadequate inhibition results in status epilepticus.
Status epilepticus is classified into different types based on the following axes:
Status epilepticus is defined as a seizure with 5 minutes or more of continuous clinical and/or electrographic seizure activity or recurrent seizure activity without recovery between seizures. The findings of convulsive status epilepticus include generalized tonic-clonic movements of the extremities and impaired mental status. Temporary focal neurological deficits (e.g., Todd’s paralysis) may be present in the post-ictal period. Non-convulsive status epilepticus presents with impaired mental status and may or may not have subtle motor signs such as tonic eye deviation. In non-convulsive status epilepticus, seizure activity is seen on the electroencephalography (EEG) despite the absence or paucity of overt clinical signs.
The diagnosis of convulsive status epilepticus is made clinically but requires emergent neuroimaging and laboratory studies to identify a potential etiology. A head computed tomography (CT) scan is appropriate in most situations and most easily obtained. Magnetic resonance imaging (MRI) of the brain is more sensitive for identifying malformations in pediatric patients, but may be difficult to obtain and may require sedation. Laboratory studies should include bedside blood glucose level, serum electrolytes (sodium, potassium, calcium, and magnesium), BUN, creatinine, serum bicarbonate, a complete blood count and a lumbar puncture with cerebrospinal fluid (CSF) evaluation. If the patient has a known seizure disorder, anti-epileptic drug levels should be obtained. Suspicion of toxic ingestion mandates toxicology studies (e.g., urine toxicology screen, serum levels of specific toxins such as theophylline or lithium). Other studies may be considered based on the presentation (liver function tests, inborn errors of metabolism and coagulation studies). A pregnancy test should be obtained in all women of child-bearing age. An EEG should be obtained. Non-convulsive status epilepticus requires all of the previously mentioned imaging and laboratory studies for the identification of an underlying etiology but also requires EEG monitoring for diagnosis.
Status epilepticus must be addressed quickly and in an organized manner, with simultaneous assessment/management of the airway, breathing, and circulation, while also administering antiepileptic drug (AED) treatment. The primary goal of management is to definitively abort seizure activity as rapidly as possible while supporting the patient’s cardiovascular and respiratory status.
All patients with status epilepticus require hospital admission, preferably to the intensive care unit.
Differential diagnoses of status epilepticus include:
The mortality rate for patients with the first episode of generalized convulsive status epilepticus is between 16 to 20 percent , [. Mortality is dependent on the etiology of status epilepticus, with anoxic status epilepticus approaching 80 percent . Refractory status epilepticus has mortality rates between 35 to 60 percent with patients needing prolonged courses of barbiturates or benzodiazepines worst effected. Young patients who have cryptogenic refractory status epilepticus fare somewhat better than older patients who have etiology identified. , . Some in vitro models show that permanent neurological damage can set in after 30 minutes of status epilepticus. About 40 percent of patients with the first episode of status epilepticus develop subsequent epilepsy and there is a 25 to 30 percent risk of recurrent status epilepticus after the first episode .
Complications of status epilepticus can be separated into medical and neurological complications and also immediate and delayed complications.
Medical complications include cardiac arrhythmia, cardiac damage because of catecholamine surge, respiratory failure, hypoventilation, hypoxia, aspiration pneumonia, pulmonary edema, fever, and leukocytosis are some of the common and serious complications seen in patients with status epilepticus.
Neurological complications include progression to chronic epilepsy and recurrent status epilepticus. In cases of prolonged refractory status epilepticus there can be permanent neurological damage induced by the hyper-metabolic activity in regions of the brain that are undergoing prolonged and abnormal electrical activity.
There are known risks of congenital disabilities due to exposure to some antiepileptic drugs (phenytoin, valproate sodium, and phenobarbital) during the first trimester of pregnancy. In the setting of status epilepticus, fetal well-being is dependent on the immediate, successful management of seizure activity in the mother. Lorazepam is recommended for emergency control treatment if status epilepticus occurs during the first trimester. Levetiracetam should be considered for urgent control therapy in this setting as evidence suggests a lower risk of associated congenital disabilities in comparison to some other antiepileptic drugs (phenytoin, valproate sodium, and phenobarbital). If eclampsia is suspected, intravenous magnesium sulfate is the antiepileptic drug of choice. Delivery of the fetus is the definitive treatment of eclampsia.
Status epilepticus is best managed by an interprofessional team that includes neurology nurses. To improve outcomes, clinicians should avoid unnecessary imaging studies or laboratory workup when the patient is having a seizure. Status epilepticus must be addressed quickly and in an organized manner, with simultaneous assessment/management of the airway, breathing, and circulation, while also administering antiepileptic drug (AED) treatment. The primary goal of management is to definitively abort seizure activity as rapidly as possible while supporting the patient’s cardiovascular and respiratory status.
Once the patient is stable, investigations can begin.
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