Varicella-zoster virus encephalitis localized to the bilateral medial temporal lobes

Case report. An immunocompetent 66-year-old man was admitted to a local hospital with fever and severe amnesia without a rash. T2-weighted MRI revealed symmetric hyperintense lesions in the bilateral medial temporal lobes. Magnetic resonance angiography showed no abnormalities. CSF analysis revealed 14 leukocytes/mm and protein and glucose concentrations of 34 mg/dL and 79 mg/dL, respectively. He was administered IV acyclovir (1,500 mg/day) for suspected herpes simplex virus (HSV) encephalitis. He did not recover and was transferred to our university hospital on day 11. On admission, his temperature was 37°C and he had no rash. A neurologic examination showed no focal signs except severe anterograde amnesia. He remembered nothing of the past few days. His MiniMental State Examination score was 21/30. His delayed recall was most impaired. Laboratory results showed increased antinuclear antibody (ANA, 104.4 index) and anti-SSA/Ro antibody (108.4 index). All antibodies to known neuronal antigens were negative, including NMDA receptor, leucine-rich gliomainactivated 1, and glutamic acid decarboxylase. Anti– varicella-zoster virus (VZV) IgG (40.9 enzyme immunoassay [EIA] units/mL) was elevated, but IgM (0.30 EIA units/mL) was not. CSF analysis revealed pleocytosis; normal glucose, protein, and myelin basic protein levels; and the absence of oligoclonal bands. The IgG index was 0.71. The antibody index to VZV (the ratio of CSF/serum-specific IgG antibodies to VZV compared with CSF/serum total IgG) was elevated at 2.8 (normal ,2.0). PCR for CSF was positive for VZV (13,000 copies/mL) and negative for HSV, human herpesvirus 6, Epstein-Barr virus, and cytomegalovirus. Diffusion-weighted (figure, A), T2-weighted (figure, B), and fluid-attenuated inversion recovery (figure, C) images from a brain MRI showed lesions more clearly than the images from the previous hospital. The lesions were not enhanced on gadolinium-enhanced T1-weighted images (figure, D). Contrast-enhanced CT of the chest, abdomen, and pelvis was normal. Based on PCR for VZV DNA in CSF and the elevated VZV antibody index reflecting intrathecal production of anti-VZV antibodies, the patient was diagnosed with limbic encephalitis (LE) caused by VZV without a rash. He was treated with IV acyclovir (1,500 mg/day for 19 days) and methylprednisolone pulse therapy followed by oral prednisolone (50 mg/day for 21 days and thereafter gradually decreased). A follow-up MRI showed improvements in abnormal signal intensity and atrophy in the same areas. PCR for VZV DNA became negative, and the VZV antibody index normalized. His amnesia slightly improved.