HSV Encephalitis Pathophysiology

Viral Entry and Neural Invasion Mechanism

The American College of Physicians suggests that HSV-1 is responsible for 90-98% of cases, and primary infection occurs in only one-third of patients, while most cases arise from reactivation in already HSV-seropositive adults 1
Primary infection occurs more frequently in children and is associated with the initial entry of the virus into the body 1
HSV-2 reactivation is more common in immunosuppressed patients and transplant recipients, leading to disseminated infection 1
The disease exhibits a bimodal distribution in the elderly population and young children 1, 2

Temporal and inferior frontal lobe involvement is typical, with early changes seen in the singular gyrus and medial temporal lobe 3, 4, 1

The European Society of Clinical Microbiology and Infectious Diseases notes that 24.5% of patients with HSE have anti-NMDA antibodies detectable in cerebrospinal fluid within 3 months after HSV infection 2
41% of encephalitis cases in patients under 30 are due to anti-NMDA encephalitis, exceeding the combined incidence of HSV, West Nile virus, and varicella-zoster virus encephalitis 2

The Infectious Diseases Society of America recommends that treatment initiation timing is the most critical prognostic factor: starting acyclovir treatment within the first 4 days of symptom onset reduces mortality from 28% to 8% 5
Delaying treatment for more than 48 hours after hospital admission is independently associated with poor prognosis 3, 5
Untreated HSV encephalitis has a mortality rate of up to 70%, but early acyclovir treatment can reduce this rate to 25-28% 1

HSV-2 infection is more common in immunosuppressed patients and neonates 1
Prolonged intravenous acyclovir treatment may be necessary for VZV encephalitis in immunocompromised patients 6
Transplant recipients are at higher risk of HSV-2 reactivation, leading to disseminated infection 1