Lancet Neurol

Dexamethasone fails to improve verbal memory score in herpes simplex encephalitis

February 3, 2026

A UK multicenter trial of 94 adults with herpes simplex virus (HSV) encephalitis found that adjunct dexamethasone (10 mg/kg IV four times daily for 4 days) plus acyclovir didn’t improve verbal memory scores at 26 weeks compared with acyclovir alone. The primary outcome—verbal memory measured by the Wechsler Memory Scale-IV—showed no significant difference between groups (71 vs. 69; adjusted difference, 1.77; 95% confidence interval, -9.57 to 13.12; p=0.76). Dexamethasone demonstrated a satisfactory safety profile with similar adverse event rates between groups and no treatment-related deaths.

Clinical takeaway: Despite theoretical benefits of reducing brain inflammation, adjunct dexamethasone doesn’t enhance cognitive outcomes in HSV encephalitis. However, its safety profile suggests early corticosteroid use in suspected encephalitis is unlikely harmful while awaiting diagnostic confirmation.

Source:

Solomon T, et al. (2026, January 29). Lancet Neurol. Safety and efficacy of adjunct dexamethasone in adults with herpes simplex virus encephalitis in the UK (DexEnceph): a multicentre, observer-blind, randomised, phase 3, controlled trial. https://pubmed.ncbi.nlm.nih.gov/41579900/