Clinical, epidemiological, and etiological studies of adult aseptic meningitis: a report of 12 cases of herpes simplex meningitis, and a comparison with cases of herpes simplex encephalitis

We treated 437 cases of adult aseptic meningitis and 12 cases (including 2 recurrent patients; age, 31.8 ± 8.9 years; 7 females) of herpes simplex meningitis from 2004 to 2016. The incidence rate of adult herpes simplex meningitis in the cases with aseptic meningitis was 2.7%. One patient was admitted during treatment of genital herpes, but no association was observed between genital herpes and herpes simplex meningitis in the other cases. The diagnoses were confirmed in all cases as the cerebrospinal fluid (CSF) was positive for herpes simplex virus (HSV)-DNA. For diagnosis confirmation, the DNA test was useful after 2-7 days following initial disease onset. Among other types of aseptic meningitis, the patients with herpes simplex meningitis showed relatively high white blood cell counts and relatively high CSF protein and high CSF cell counts. CSF cells showed mononuclear cell dominance from the initial stage of the disease. During same period, we also experienced 12 cases of herpes simplex encephalitis and 21 cases of non-hepatic acute limbic encephalitis. Notably, the patients with herpes simplex meningitis were younger and their CSF protein and cells counts were higher than those of the patients with herpes simplex encephalitis.