The diagnosis and management of status epilepticus is an essential skill for emergency physicians. Should we rely on newly marketed products? Or should evidence-based literature guide diagnosis and management?

Status epilepticus has been defined as seizure(s) greater than or equal to 30 minutes in which the patient does not regain normal mental status between seizures. Alternatively, the Neurocritical Care Society defines it as a seizure with five minutes or more of continuous clinical or EEG seizure activity, or recurrent seizure activity without recovery between seizures.¹

History and physical examination have been the cornerstones of seizure diagnosis in the emergency department (ED). History-taking, which relies on the patient’s or witness’ accounts of the seizure event, can provide critical clues to differentiate seizures from other episodic disorders. However, its sensitivity is limited by the accuracy and completeness of the recollection, which can be affected by the patient’s postictal state or the observer’s understanding of seizure manifestations. Physical examination, including the assessment of postictal signs such as Todd’s paralysis, tongue bite marks, or loss of bladder control, offers additional diagnostic clues but also lacks specificity for seizure diagnosis.

Diagnosing Non-Convulsive Seizures

These issues are compounded in the diagnosis of non-convulsive seizures in critically ill patients. This subset of seizures lacks the dramatic convulsive movements typically associated with seizures, instead manifesting with either subtle clinical signs or altered mental status without any overt seizure-like activity. These seizures are detectable only with electroencephalography (EEG) monitoring, and similar to convulsive seizures, when prolonged or repetitive, non-convulsive seizures can present a neurological emergency termed non-convulsive status epilepticus.²

A 2013 study of routine EEG in the ED found that 5 percent of ED patients with altered mental status had non-convulsive seizures (of which 75 percent were in non-convulsive status epilepticus).³ A systematic review of non-convulsive seizures and status epilepticus in the intensive care unit (ICU) reported a pooled prevalence of 15 percent using continuous EEG. However, this prevalence varied considerably according to the clinical context or underlying etiology (8 percent among patients with coma, 10 percent in sepsis, 15 percent in stroke, 23 percent with post-cardiac arrest, and 33 to 48 percent following treatment of convulsive status epilepticus).⁴ With the increasing use of EEG, especially continuous EEG, non-convulsive seizures have been increasingly recognized and diagnosed as a cause of altered mental status in critically ill patients.

Although they may not appear to be as physically injurious as convulsive seizures, non-convulsive seizures can significantly impact the neurological outcomes and overall prognosis of patients in critical care settings. Especially in the case of status epilepticus, delayed treatment can lead to a phenomenon known as pharmacoresistance, in which the effectiveness of antiseizure medications diminishes over time due to neurobiological changes that alter drug targets (e.g., reduced surface expression of postsynaptic GABA-A receptors) and drug transport mechanisms (e.g., increased expression of drug efflux transporters) to enable self-sustaining ictal rhythms.^5,6 This underscores the importance of vigilance and integrating clinical findings with advanced diagnostic tools like EEG to improve diagnostic accuracy for seizures and refine the management of critically ill patients to ensure comprehensive neurological care.⁷

EEG Monitoring in Managing Seizures

Several studies demonstrated the importance of EEG monitoring in the management of seizures.^8-11 Although continuous EEG monitoring would be the gold standard for diagnosing and managing non-convulsive seizures, it is either unavailable or delayed at many centers, and it is rarely performed in the ED. This is because conventional EEG requires a large machine, a qualified technologist, and a significant amount of time for set up, and the output data must be reviewed and interpreted by a neurologist. Some institutions have the capability to perform real-time EEG monitoring and interpretation by a neurologist in the ED. Other devices demonstrated potential use as an alternative to traditional EEG monitoring.

For example, other modes of EEG monitoring may be used in the operative setting, including bispectral index monitoring (BIS), SEDline device, and others to monitor depth of sedation.¹² Several commercially available point-of-care EEG devices exist.¹³ A point-of-care EEG system has been developed to provide real-time EEG data.¹⁴ Preliminary data suggest that among 157 adult patients, point-of-care EEG enabled acquisition of EEG data within 90 minutes of ED arrival, identified epileptiform activity in 36 percent of patients, and impacted treatment decisions.¹⁵ The potential advantage of point-of-care EEG is rapid diagnosis, although focal seizures may be missed due to fewer electrodes. Future research is needed to determine the sensitivity and specificity of this device, particularly in the ED environment, where patients might have taken medications or recreational drugs, or might have received sedative or antiepileptic medications.

Diagnostic studies useful in determining the etiology may include POC glucose, serum electrolytes, and complete blood count. Other considerations dependent on the clinical setting and history may include CT scan, MRI, or lumbar puncture.

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Management of status epilepticus includes stabilization of airway, breathing, and circulation. If a patient is obtunded or unable to protect the airway, endotracheal intubation is indicated. Following stabilization, pharmacologic therapy should be initiated with first-line therapy of a benzodiazepine, such as lorazepam. Appropriate dosing is associated with seizure termination and reduced complications.^16-18 Antiepileptic medication may be administered concurrently, such as fosphenytoin, phenytoin, levetiracetam, or valproic acid.^19-22 Refractory status epilepticus may be treated with a continuous infusion of antiepileptic medication, such as propofol, ketamine, midazolam, or pentobarbital.

Consultation with neurology should be sought to guide therapy. Patients with status epilepticus require hospital admission, often to an intensive care setting.

Disclaimer: This article is not a comprehensive review of diagnosis and treatment of status epilepticus, but an overview of management and future directions. Authoritative sources should be used for diagnostic and treatment decisions.

Dr. Marco is a professor of emergency medicine at Penn State Health—Milton S. Hershey Medical Center at Penn State College of Medicine and an assistant editor of ACEP Now.

References

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