Acute Encephalitis Syndrome Diagnosis and Management

Immediate Actions and Initial Assessment

The American College of Neurology recommends that all patients with suspected acute encephalitis require immediate neurological specialist assessment within 24 hours and should be managed in appropriate settings to optimize morbidity and mortality outcomes 1, 2
Empiric acyclovir 10 mg/kg IV every 8 hours should be started immediately for all adults with suspected encephalitis, particularly those with seizures or altered consciousness, while awaiting diagnostic confirmation 1
Airway protection and ventilatory support needs should be assessed urgently in patients with declining consciousness, as encephalitis can cause rapid deterioration requiring ICU-level management of raised intracranial pressure and cerebral perfusion optimization 1, 2

The American Academy of Neurology recommends that MRI is the imaging modality of choice and must be obtained within 48 hours, as it detects early cerebral changes in approximately 90% of cases versus only 25% sensitivity for CT 2
Lumbar puncture with results ideally available within 24-48 hours is essential, and CSF studies should include PCR assays for HSV and other viral pathogens 2, 3
EEG should be obtained when distinguishing psychiatric versus organic causes in patients with mildly altered behavior, or when subtle motor or non-convulsive seizures are suspected (abnormal in >80% of encephalitis cases) 2, 3

The Infectious Diseases Society of America recommends that acyclovir 10 mg/kg IV every 8 hours for 14-21 days is the treatment of choice for Herpes Simplex Virus encephalitis in adults and children 1
The American College of Neurology recommends that high-dose corticosteroids as first-line treatment for Acute Disseminated Encephalomyelitis (ADEM) 2
The American Academy of Neurology recommends that rituximab is used for known or highly suspected antibody-mediated autoimmunity (e.g., NMDAR-antibody encephalitis) as second-line immunotherapy 4, 1

The American Epilepsy Society recommends that IV valproate 20-30 mg/kg loading dose achieves 88% seizure cessation within 20 minutes without associated hypotension 1
Levetiracetam 30-60 mg/kg/day demonstrates 73% seizure cessation rate 1
Phenytoin 18-20 mg/kg IV (or fosphenytoin equivalent) has only 56% efficacy following benzodiazepines and causes hypotension in 12% of cases 1

The Neurocritical Care Society recommends that airway protection and ventilatory support, management of raised intracranial pressure, optimization of cerebral perfusion pressure, and correction of electrolyte imbalances are priorities in ICU management 2
Plasma exchange is particularly effective in refractory cases, with 5-10 sessions every other day 4

The American College of Neurology recommends that patients should not be discharged without either definite or suspected diagnosis, and arrangements for outpatient follow-up and ongoing therapy/rehabilitation should be made at discharge meeting 2
All patients require access to rehabilitation assessment, as sequelae may not be immediately apparent at discharge and commonly include anxiety, depression, and cognitive deficits 1, 2, 3

Standard analgesics such as acetaminophen or non‑steroidal anti‑inflammatory drugs should be used for headache symptom control as part of supportive care while antiviral therapy is administered. 5

Clinicians must monitor for signs of increased intracranial pressure, because such findings require management strategies different from simple analgesic therapy. 5
A decline in level of consciousness accompanied by worsening headache mandates immediate intensive‑care assessment for airway protection, control of raised intracranial pressure, and optimization of cerebral perfusion pressure. 5

For varicella‑zoster virus (VZV) encephalitis, intravenous aciclovir at 10–15 mg/kg three times daily is recommended; corticosteroids (e.g., prednisolone 60–80 mg daily for 3–5 days) may be added when a vasculitic component is present. 5
In enterovirus encephalitis, the antiviral agent pleconaril has been shown in phase III trials to shorten headache duration by roughly two days compared with placebo, although the drug is not widely available. 5

Routine use of corticosteroids for viral encephalitis–related headache is not advised, except in specific circumstances such as VZV‑associated vasculitis or acute disseminated encephalomyelitis (ADEM). 5
Renal function should be monitored regularly when administering aciclovir, especially at higher dosing regimens (e.g., 15 mg/kg) used for VZV infection, to mitigate the risk of nephrotoxicity. 5