What is the treatment for viral brainstem encephalitis?

Treatment of Viral Brainstem Encephalitis

Start intravenous acyclovir 10 mg/kg every 8 hours immediately upon suspicion of viral brainstem encephalitis, as HSV is the most treatable cause and delays beyond 48 hours worsen outcomes. 1, 2

Immediate Empiric Antiviral Therapy

• Acyclovir must be initiated within 6 hours of admission if CSF/imaging results are not immediately available, or if the patient is severely ill or deteriorating 1, 3
• The standard dose is 10 mg/kg IV every 8 hours for adults, continuing for 14-21 days for confirmed HSV encephalitis 1, 2
• For children aged 3 months to 12 years, use 10-15 mg/kg three times daily 1
• HSV-1 accounts for 79% of HSV brainstem encephalitis cases, with mortality reaching 41% without treatment, but dropping to 22% with acyclovir 4
• Do not wait for PCR confirmation before starting treatment—CSF remains PCR-positive for several days after acyclovir initiation, so delayed lumbar puncture can still confirm diagnosis 1

Critical Distinction: Brainstem Encephalitis vs. Cerebellitis

This distinction is crucial because treatment differs dramatically:

• Brainstem encephalitis requires immediate acyclovir due to high mortality and potential for HSV involvement 4
• Isolated viral cerebellitis is self-limiting and requires only supportive care without antivirals, as the pathogenic process is immune-mediated demyelination rather than direct viral cytopathology 1, 5
• Common pitfall: Do not withhold acyclovir in brainstem involvement—the 41% mortality without treatment versus 22% with acyclovir demonstrates the critical importance of empiric therapy 4

Clinical Features Suggesting Brainstem Involvement

• Neuro-ophthalmologic findings (81% of cases), cranial nerve deficits (69%), and fever (69%) are the hallmark presentations 4
• Vegetative nervous system dysfunction is characteristic, particularly with enterovirus 71 6
• Quadriplegia occurs in 19% of cases and indicates severe involvement 4
• Pulmonary edema or hemorrhage may develop 3-4 days after onset, requiring early identification 6

Specific Pathogen Considerations

HSV Brainstem Encephalitis

• Continue IV acyclovir for 14-21 days 1
• Perform repeat lumbar puncture at completion to confirm CSF is HSV PCR-negative 1
• If CSF remains positive, continue acyclovir with weekly PCR monitoring until negative 1
• Patients under 30 years with less severe neurologic involvement at presentation have the best outcomes 2

VZV Encephalitis

• Use acyclovir 10-15 mg/kg three times daily for up to 14 days 1, 7
• If vasculopathy or stroke-like presentation is present, add corticosteroids (e.g., prednisolone 60-80 mg daily for 3-5 days) due to the inflammatory nature of the lesion 1
• VZV is less sensitive to acyclovir than HSV, justifying the higher dose of 15 mg/kg if renal function permits 1

Enterovirus (Including EV71)

• No specific antiviral treatment is recommended 3
• Pleconaril or IV immunoglobulin may be considered in severe disease if available 3, 8, 9
• Focus on supportive care: reduction of intracranial pressure with mannitol/furosemide, methylprednisolone for inflammation, and management of pulmonary complications 6

Corticosteroid Use: A Nuanced Decision

• Do not use corticosteroids routinely in HSV encephalitis while awaiting results of ongoing randomized controlled trials 1
• Corticosteroids may have a role under specialist supervision for marked cerebral edema, brain shift, or raised intracranial pressure, but their immunomodulatory effects could theoretically facilitate viral replication 1
• Exception: VZV vasculopathy with stroke presentation warrants corticosteroids in addition to acyclovir 1, 7

Critical Care Management

• Patients require immediate hospitalization with access to intensive care units 3, 8, 9
• Falling level of consciousness demands urgent ICU evaluation for airway protection, ventilatory support, and management of increased intracranial pressure 3
• Multidisciplinary involvement includes neurology, infectious disease, virology, neurophysiology, neuroradiology, and intensive care 3
• EEG monitoring is essential to identify non-convulsive seizures in confused or comatose patients 7

Diagnostic Workup (While Treatment Proceeds)

• Lumbar puncture should be performed as soon as possible unless contraindicated by signs of increased intracranial pressure 1, 3
• CSF PCR results should be available within 24-48 hours 3
• MRI is preferred over CT for neuroimaging 3, 8, 9
• Brain biopsy has no role in initial evaluation but should be considered after the first week if no diagnosis is established, especially with focal imaging abnormalities 3

Dose Adjustments for Renal Impairment

• Reduce acyclovir dose in pre-existing renal impairment to prevent crystalluria and obstructive nephropathy, which can affect up to 20% of patients after 4 days of IV therapy 1, 2
• Geriatric patients have higher acyclovir plasma concentrations due to age-related renal changes and require dose reduction 2
• Monitor renal function closely throughout treatment 1

Duration and Follow-up

• Transfer to a specialized neurology service within 24 hours if diagnosis is not rapidly established or patient fails to improve 1, 3
• Do not discharge without a definitive or suspected diagnosis 3
• All patients require rehabilitation assessment regardless of age 3
• Arrange outpatient follow-up with plans for ongoing therapy and rehabilitation 3