Asymptomatic Self-Limiting Diffuse White Matter Lesions in Subacute to Chronic Stage of Herpes Simplex Encephalitis

Abstract

This study evaluated white matter changes in the subacute and chronic stages of herpes simplex encephalitis (HSE). Subjects comprised 15 patients with HSE. All patients were examined using MRI at onset, and then at seven to ten days, three to five weeks and two to three months after onset. In addition, the six patients who displayed white matter signal abnormalities were examined at six months and >one year after onset. Cell count, protein levels, polymerase chain reaction (PCR) of herpes simplex virus in cerebrospinal fluid (CSF), and exacerbation of neurological symptoms as well as dose of acyclovir were compared between patients with and without white matter abnormalities. Diffuse white matter signal changes were identified at the subacute stage (3-5 weeks after onset) of HSE in six patients (6/15, 40%). No significant relationship was observed between the presence of white matter signal abnormalities and laboratory data, acyclovir dose or clinical symptoms. These signal abnormalities disappeared or improved by two years without any clinical treatment. Diffuse white matter signal abnormalities occur frequently in the subacute stage of HSE. Although the mechanisms underlying these white matter lesions have not been elucidated, subclinical immune-mediated processes may be considered. Repeat MRI studies over a long period are necessary for evaluating the clinical process of patients with HSE.