Nonconvulsive Status Epilepticus in the Neurosurgical Setting

Herein, we review the current state of nonconvulsive status epilepticus (NCSE). NCSE has recently been recognized as one of the causes of unexplained impaired consciousness in the neurosurgical or neurocritical setting. The causes of NCSE include not only central nervous system disorders such as craniotomy, stroke, traumatic brain injury, and central nervous system inflammation, but also severe critical conditions such as sepsis and uremia, among others. NCSE shows no overt clinical manifestations; therefore, prompt and correct diagnosis is difficult. The diagnosis of NCSE should be made by electroencephalogram (EEG), especially continuous EEG (CEEG) monitoring, because NCSE is caught only by prolonged recording. However, the interpretation of the EEG findings is also challenging because of the varying EEG characteristic of NCSE. While the diagnosis should be based on temporal or spatial EEG changes, several definitions and criteria have been proposed, and uniform, universal criteria are still lacking. Once NCSE is diagnosed, antiepileptic drugs (AEDs) should be aggressively administrated. Although there are no standardized international therapeutic guidelines, several AEDs have been attempted in clinical practice in other countries, including fosphenytoin, midazolam, levetiracetam, and valproate. Particularly, several AEDs should be considered prior to using anesthetics. Finally, the prognosis of NCSE depends on the cause thereof; however, in general, earlier intervention for NCSE appears important in terms of better recovery.