From the Guidelines
Encephalitis caused by herpes simplex virus (HSV), West Nile virus, and rabies virus requires immediate and targeted treatment to reduce morbidity, mortality, and improve quality of life. The management of encephalitis involves early recognition of the clinical syndrome, appropriate diagnostic evaluation, and emergent administration of certain antimicrobial agents 1. For HSV encephalitis, immediate treatment with intravenous acyclovir at 10 mg/kg every 8 hours for 14-21 days is essential to reduce mortality and neurological sequelae 1. Early diagnosis through lumbar puncture and PCR testing of cerebrospinal fluid is crucial, with a reported sensitivity and specificity of 96%–98% and 95–99%, respectively, in adults 1.
Key Considerations
- For West Nile virus encephalitis, treatment is primarily supportive as no specific antiviral therapy exists; management focuses on controlling symptoms, maintaining hydration, and preventing complications 1.
- Rabies encephalitis is almost universally fatal once symptoms appear, making prevention through post-exposure prophylaxis critical, including thorough wound cleansing, rabies immune globulin (20 IU/kg) infiltrated around the wound, and a series of rabies vaccinations (days 0,3,7, and 14) 1.
- All forms of encephalitis require close monitoring for increased intracranial pressure, seizures, and respiratory compromise 1.
- The different treatment approaches reflect the underlying pathophysiology: HSV responds to antiviral medication that inhibits viral DNA synthesis, while West Nile virus lacks specific inhibitors, and rabies causes irreversible neuronal damage once the virus reaches the brain 1.
Diagnostic Evaluation
- Evaluation of CSF samples is essential for all patients with encephalitis, unless contraindicated, and should include PCR testing for viral nucleic acids 1.
- Neuroimaging, such as MRI, is useful for detecting early changes in encephalitis and excluding other conditions with similar clinical presentations 1.
- The diagnostic evaluation should be individualized and guided by epidemiologic and clinical clues, as well as laboratory findings 1.
Treatment Approaches
- The treatment approach for encephalitis should be guided by the suspected or confirmed etiology, with HSV encephalitis requiring antiviral therapy, West Nile virus encephalitis requiring supportive care, and rabies encephalitis requiring post-exposure prophylaxis 1.
- In cases where the etiology is unknown, empiric treatment with acyclovir should be considered, as well as other supportive measures to manage symptoms and prevent complications 1.
From the FDA Drug Label
Herpes Simplex Encephalitis Sixty-two patients ages 6 months to 79 years with brain biopsy-proven herpes simplex encephalitis were randomized to receive either acyclovir (10 mg/kg every 8 hours) or vidarabine (15 mg/kg/day) for 10 days (28 were treated with acyclovir and 34 with vidarabine) Overall mortality at 12 months for patients treated with acyclovir was 25% compared to 59% for patients treated with vidarabine.
- Key points:
- Acyclovir is used to treat herpes simplex encephalitis.
- The recommended dose is 10 mg/kg every 8 hours for 10 days.
- Acyclovir has been shown to decrease mortality and improve outcomes in patients with herpes simplex encephalitis compared to vidarabine 2.
- Note: There is no information in the provided drug label about the treatment of West Nile virus or rabies encephalitis.
From the Research
Causes of Encephalitis
- Encephalitis can be caused by viral infections, such as herpes simplex virus (HSV) type 1, West Nile virus, and Japanese encephalitis virus 3, 4
- Autoimmune causes, such as N-methyl D-aspartate receptor (NMDAR) antibody encephalitis, are also recognized 4, 5
- Other causes include postinfectious, paraneoplastic, or idiopathic autoimmune processes 6
Clinical Manifestations
- Patients with encephalitis may present with a combination of fever, alterations in behavior, personality, cognition, and consciousness 6
- Focal neurological deficits, seizures, movement disorders, and/or autonomic instability may also be exhibited 6
- Symptoms can fluctuate rapidly, and psychiatric manifestations, such as psychosis and aggression, may be prominent in autoimmune encephalitis 4
Diagnosis and Management
- Diagnosis of encephalitis hinges crucially on lumbar puncture and cerebrospinal fluid (CSF) examination, but imaging and electroencephalography (EEG) may also be helpful 5
- Treatment of HSV encephalitis with aciclovir dramatically improves outcome, but the optimal management of autoimmune encephalitis is still uncertain 5
- Specific treatment options are available for herpesvirus group and non-viral infections, and various forms of immunotherapy are used for autoimmune encephalitis 3, 4
- Supportive care, including general supportive care and intensive care admission, may be necessary for some patients 3