Role of EEG in Herpes Encephalitis

Diagnostic Considerations

The American Academy of Neurology recommends that EEG be performed in all patients with suspected herpes encephalitis, especially if there is a suspicion of nonconvulsive seizures or subtle motor seizures 1, 2, 3
EEG should be used to detect nonconvulsive seizures and subtle motor seizures in patients with herpes encephalitis, as these seizures are common in both HSV encephalitis and other encephalopathies 1, 2, 3
Nonconvulsive status epilepticus can present as encephalopathy and may be missed without EEG 4
EEG is abnormal in more than 80% of patients with acute viral encephalitis and can help distinguish it from primary psychiatric illness 1, 2, 3

EEG abnormalities in HSV encephalitis include nonspecific diffuse high-amplitude slow waves, temporal lobe spike-wave activity, and periodic lateralized epileptiform discharges (PLEDs) 1, 2, 3
PLEDs are seen in many cases of HSV encephalitis, but can also be seen in other viral encephalitides and noninfectious conditions 1, 2, 3

The Infectious Diseases Society of America recommends that intravenous acyclovir (10 mg/kg three times a day) be started within 6 hours of presentation if viral encephalitis is suspected or if results are pending 1, 5
Treatment should not be delayed while waiting for a definitive diagnosis, and empirical treatment for treatable causes should be started immediately 5, 4

Serial EEG recordings can be used to monitor disease progression and treatment response, and can help identify patients who are at risk of poor outcome 4