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How to Manage Non-Convulsive Status Epilepticus

December 5, 2023

By Laura Murphy

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This is a review of the diagnosis and management of non-convulsive status epilepticus (NCSE) in the emergency department. Nonspecific signs and symptoms at presentation make it challenging to identify, which can lead to under-diagnosis and delay in treatment.

NCSE: Something’s just not right
NCSE is a form of status epilepticus that presents with prolonged seizure activity without overt convulsive motor activity; the definition includes a change in cognitive and mental processes from baseline (with electrographic abnormalities noted on EEG) lasting over 10 minutes continuously or greater than 20% of one hour on EEG monitoring. There are different types including generalized/absence, focal/lateralization and autonomic, and it can occur in non-comatose or comatose patients.

NCSE is caused by a variety of conditions including epilepsy, cerebral pathology or systemic insult such as infection, drugs, or toxins. It is most commonly associated with epilepsy, and up to half of cases are associated with inadequate treatment of seizures or subtherapeutic levels of anti-seizure medications. These patients generally have a lower mortality. Other causes include acute brain injury such as ischemic stroke, subarachnoid hemorrhage, hypoxic ischemic encephalopathy, encephalitis as well as systemic insult such as infection, alcohol, ingestion, metabolic derangements, infection and sepsis, or autoimmune disease.

NCSE can present with both negative (anorexia, amnesia, aphasia, catatonia, coma/confusion, lethargy, staring) and positive (agitation, aggression, blinking or crying, delirium, echolalia, eye deviation or nystagmus, nausea and vomiting, tremor, psychosis) signs or symptoms. The most common symptom is altered mental status, ranging from confusion to coma. The most specific finding is abnormal ocular movements, including blinking, eyelid twitching, pupillary dilation, gaze deviation or nystagmus. Consider NCSE in the following patients: those with altered sensorium and abnormal ocular movements, prolonged post-ictal state after convulsive seizure, prolonged confusion in the setting of cerebral injury, or with unexplained altered mental status (including psychiatric symptoms).

Workup includes laboratory panel (including serum AED levels if relevant) and neuroimaging. Definitive diagnosis typically requires EEG, which can be difficult to obtain in the ED. Management focuses on treatment of the underlying cause as well as rapid seizure termination with benzodiazepines and anti-epileptics (such as fosphenytoin, valproate or levetiracetam). ED clinicians should have a low threshold to initiate neurologic evaluation and EEG monitoring and to trial treatment with benzodiazepines and/or antiepileptics.

The prevalence of NCSE approaches 30% in ICU patients who are altered, and NCSE accounts for almost half of all cases of status epilepticus in ICU patients. While brain damage from NCSE can be difficult to differentiate from underlying conditions, mortality increases with duration of NCSE; sustained neuronal excitation leads to cerebral injury. Therefore, early recognition in the ED is key. Approximately half of patients who survive NCSE have a persistent neurologic deficit, and only 25% return to their neurologic baseline.

How will this change my practice?
As the article highlights, NCSE is a tricky clinical entity due to significant overlap with other similar or concurrent conditions, but it is associated with high morbidity and mortality. However, it is likely more common than we recognize, so I will have a lower threshold to consider a trial of anti-seizure medication and initiation of EEG evaluation in altered patients who do not return to baseline.

Nonconvulsive Status Epilepticus: A Review for Emergency Clinicians. J Emerg Med. 2023 Oct;65(4):e259-e271. doi: 10.1016/j.jemermed.2023.05.012. Epub 2023 Jun 5.

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