Abstract
Objectives: To describe the clinical and paraclinical characteristics and identify factors associated with treatment outcomes in patients with herpes simplex encephalitis treated at Bach Mai Hospital. Methods: A combined retrospective–prospective longitudinal case-series study was conducted in 31 adult patients with confirmed herpes simplex encephalitis, diagnosed according to the 2013 International Encephalitis Consortium criteria and a positive cerebrospinal fluid (CSF) herpes simplex virus polymerase chain reaction (HSV-PCR) result. The patients were treated at the Neurology Center and the Center for Tropical Diseases, Bach Mai Hospital, between January 2024 and June 2026. Clinical manifestations, laboratory findings, brain magnetic resonance imaging (MRI), electroencephalographic (EEG) findings, treatment characteristics, and clinical outcomes were collected using a standardized case report form and analyzed with IBM SPSS Statistics version 22.0. Functional outcome at hospital discharge was assessed using the modified Rankin Scale (mRS) and categorized as good (mRS 0–2) or poor (mRS 3–6). Results: The mean age was 56.7 ± 14.1 years, and 24/31 (77.4%) of the patients were male. The most common clinical manifestations were fever (31/31; 100%), headache (26/31; 83.9%), acute memory impairment (25/31; 80.6%), altered consciousness (24/31; 77.4%), behavioural or psychiatric disturbances (22/31; 71.0%), and seizures (17/31; 54.8%). Cerebrospinal fluid analysis demonstrated lymphocytic pleocytosis with mildly elevated protein levels. Brain MRI was abnormal in all patients, most commonly involving the temporal lobe (28/31; 90.3%) and the insular cortex (27/31; 87.1%), while 26/31 (83.9%) exhibited lesions affecting two or more brain regions. Electroencephalography was performed in 26/31 (83.9%) patients. The most frequent EEG abnormalities were focal or diffuse slowing (13/26; 50.0%), followed by lateralized periodic discharges (LPDs) (10/26; 38.5%). Epileptiform activity and non-convulsive status epilepticus were identified in 4/26 (15.4%) and 3/26 (11.5%) patients, respectively. After treatment, 30/31 (96.8%) patients had negative CSF HSV-PCR results. A good functional outcome was achieved in 17/31 (54.8%), whereas 14/31 (45.2%) remained moderately to severely disabled at hospital discharge. Poor treatment outcomes were significantly associated with involvement of two or more brain regions on MRI (p = 0.048), admission to the intensive care unit (p < 0.001), mechanical ventilation (p = 0.018), and hospital-acquired pneumonia (p = 0.024). Conclusions: Herpes simplex virus encephalitis presents with diverse clinical manifestations, typically characterized by an acute encephalitic syndrome accompanied by memory impairment and behavioural disturbances. Temporal lobe and insular cortex involvement are the most characteristic neuroimaging findings. Although virological clearance, as demonstrated by negative CSF HSV-PCR, was achieved in most patients following antiviral therapy, functional disability at hospital discharge remained common. Extensive MRI involvement, intensive care unit admission, mechanical ventilation, and hospital-acquired pneumonia were significantly associated with poor treatment outcomes.
