What is the diagnosis and treatment for viral encephalitis (inflammation of the brain caused by a virus)?

From the Guidelines

Viral encephalitis should be treated with acyclovir (10 mg/kg IV every 8 hours for 14-21 days) as the first-line therapy, especially for herpes simplex virus encephalitis, and supportive care should include management of increased intracranial pressure, seizure control, and maintaining adequate hydration and nutrition. The diagnosis of viral encephalitis involves cerebrospinal fluid analysis, brain imaging (MRI preferred over CT), and PCR testing to identify the specific virus 1. Early treatment is crucial as delays can lead to permanent neurological damage or death, and the prognosis varies depending on the causative virus, patient age, and how quickly treatment begins 1. Some key points to consider in the diagnosis and treatment of viral encephalitis include:

• The use of acyclovir as the first-line therapy for herpes simplex virus encephalitis, which has been shown to improve outcomes in adults with HSV encephalitis, reducing mortality to less than 20-30% 1.
• The importance of supportive care, including management of increased intracranial pressure, seizure control with anticonvulsants like levetiracetam (500-1500 mg twice daily), and maintaining adequate hydration and nutrition 1.
• The need for close monitoring in a hospital setting, often in intensive care, and the importance of early treatment to prevent permanent neurological damage or death 1.
• The role of prevention strategies, including vaccination against viruses like measles, mumps, and Japanese encephalitis, and avoiding mosquito bites in areas where arthropod-borne viruses are endemic 1. It is also important to note that the diagnostic evaluation of a patient who presents with encephalitis needs to be individualized and should be guided by epidemiologic and clinical clues and laboratory findings 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. The diagnosis of viral encephalitis, specifically herpes simplex encephalitis, is typically made by brain biopsy. The treatment for herpes simplex encephalitis is acyclovir at a dose of 10 mg/kg every 8 hours for 10 days 2. Key points about the treatment include:

• Acyclovir has been shown to decrease mortality and improve outcomes compared to vidarabine.
• Patients less than 30 years of age and those with less severe neurologic involvement at the start of treatment tend to have better outcomes.

From the Research

Diagnosis of Viral Encephalitis

• The diagnosis of viral encephalitis involves identifying a true parenchymal virus infection of the brain, distinguishing it from non-infective encephalopathy and acute disseminated encephalomyelitis (ADEM) 3
• Analysis of cerebrospinal fluid (CSF) for protein and glucose contents, cellular analysis, and identification of the pathogen by polymerase chain reaction (PCR) amplification are essential for diagnosis 4
• Neuroimaging, preferably by magnetic resonance imaging (MRI), is also a crucial aspect of evaluation 4, 5
• Lumbar puncture should be performed as soon as possible, unless there are strict contraindications, and brain biopsy should be reserved for unusual and diagnostically difficult cases 4

Treatment of Viral Encephalitis

• Early treatment with intravenous acyclovir is essential for patients suspected of having herpes simplex encephalitis (HSE) due to its remarkable safety and efficacy 3, 6
• Acyclovir has been proven to reduce mortality by 50% in HSE cases 6
• Supportive therapy is an important basis of management, and specific anti-viral therapy, such as acyclovir, is available for HSE 4
• Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered effective and their use is controversial 4
• Surgical decompression may be indicated for impending uncal herniation or increased intracranial pressure refractory to medical management 4

Specific Considerations

• Herpes simplex virus (HSV) encephalitis is the most common cause of nonendemic sporadic encephalitis in the United States 6, 5
• The use of PCR techniques to amplify the genome of HSV from CSF has become the diagnostic procedure of choice for HSE 5
• Negative CSF HSV PCR results should always be interpreted in the context of the timing of specimen collection and the likelihood of disease 5
• Patients with HSE will typically have a negative CSF HSV PCR after 14 days of acyclovir treatment, and a persisting positive PCR should prompt consideration of additional or revised antiviral therapy 5