Usage of Dexamethasone to Treat Herpes Simplex Virus Encephalitis
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Reviewed & Translated by Dat Tien Nguyen, B.A, ScM.
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Posted on April 24th, 2026
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Herpes simplex virus (HSV) encephalitis is a severe neurological condition characterized by inflammation and swelling of the brain, often leading to death or long-term cognitive impairment. Although intravenous aciclovir is the standard treatment, mortality and morbidity remain high. Corticosteroids are sometimes used as adjunct therapy to reduce inflammation, but their clinical benefit in HSV encephalitis is uncertain. A recent study published in the Lancet evaluated the use of dexamethasone in this setting.
Funding Source(s): United Kingdom National Institute for Health and Care Research
The phase 3 clinical study was conducted in the United Kingdom and enrolled 94 patients with confirmed HSV encephalitis. Diagnosis was established by detecting HSV DNA in cerebrospinal fluid using PCR. All participants received standard antiviral therapy with intravenous aciclovir at a dose of 10 mg/kg three times daily. Patients were then assigned to receive adjunct dexamethasone or no additional treatment; the control group did not receive a placebo. Dexamethasone was administered at 10 mg four times daily for four days.
At 26 weeks of follow-up, there was no significant difference in verbal memory between patients treated with dexamethasone and those who received aciclovir alone. Further neuropsychological assessments showed no improvement in visual memory, immediate or delayed recall, working memory, or processing speed. Dexamethasone also did not reduce seizure frequency or shorten hospital stay. Importantly, the use of dexamethasone did not result in increased harm, addressing concerns that its immunosuppressive effects could worsen viral replication. Overall, the findings suggest that adjunct corticosteroid therapy does not provide meaningful clinical benefit in HSV encephalitis.
Funding Source(s): United Kingdom National Institute for Health and Care Research
The phase 3 clinical study was conducted in the United Kingdom and enrolled 94 patients with confirmed HSV encephalitis. Diagnosis was established by detecting HSV DNA in cerebrospinal fluid using PCR. All participants received standard antiviral therapy with intravenous aciclovir at a dose of 10 mg/kg three times daily. Patients were then assigned to receive adjunct dexamethasone or no additional treatment; the control group did not receive a placebo. Dexamethasone was administered at 10 mg four times daily for four days.
At 26 weeks of follow-up, there was no significant difference in verbal memory between patients treated with dexamethasone and those who received aciclovir alone. Further neuropsychological assessments showed no improvement in visual memory, immediate or delayed recall, working memory, or processing speed. Dexamethasone also did not reduce seizure frequency or shorten hospital stay. Importantly, the use of dexamethasone did not result in increased harm, addressing concerns that its immunosuppressive effects could worsen viral replication. Overall, the findings suggest that adjunct corticosteroid therapy does not provide meaningful clinical benefit in HSV encephalitis.