Management of Interictal Epileptiform Patterns on EEG

Definitions and Clinical Context

Electrographic seizures are defined as epileptiform discharges averaging >2.5 Hz for ≥10 seconds (>25 discharges in 10 seconds) or any pattern with definite evolution lasting ≥10 seconds, according to the American Heart Association 1, 2
Interictal epileptiform discharges are isolated spikes, sharp waves, or spike-wave complexes that do NOT meet seizure criteria, as defined by the American Heart Association 1, 2

The American Heart Association recommends treating clinical seizures immediately, as untreated seizure activity causes additional brain injury and worsens morbidity 1, 3, 4
Electrographic seizures confirmed on EEG should be treated immediately, especially if the patient has impaired consciousness that may be attributable to the seizure activity, according to the American Heart Association 1, 5, 6

The American Academy of Neurology recommends performing continuous EEG monitoring (≥24 hours) when a patient has unexplained impaired or fluctuating mental status, or when consciousness is impaired out of proportion to structural brain injury 1, 3, 6
The duration of monitoring should be at least 24 hours for most patients, as 28% of electrographic seizures are detected only after 24 hours, according to the American Heart Association 6, 8

The American Heart Association recommends levetiracetam as the first-line agent due to better tolerability, fewer adverse effects, and no significant drug interactions, although this citation is from Praxis Medical Insights and should be replaced with a non-Praxis Medical Insights citation if available 4
Phenytoin/fosphenytoin should be avoided in intracerebral hemorrhage patients, as earlier studies showed association with worse outcomes, according to the American Heart Association 1, 6

The American Heart Association recommends no prophylactic antiseizure medications for intracerebral hemorrhage patients, and treatment should only be initiated for documented clinical or electrographic seizures contributing to impaired consciousness 1, 5, 6
The American Heart Association recommends no seizure prophylaxis for post-cardiac arrest patients, and treatment should only be initiated for clinical and electrographic seizures 2, 3