We described a 58-year-old woman with herpes simplex encephalitis (HSE), who initially had fever and developed impaired consciousness. Cerebrospinal fluid (CSF) examination showed mononuclear pleocytosis and the existence of herpes simplex virus (HSV) DNA. The first T1-weighted MR image showed symmetrical swelling and low signal intensity lesions in the medial temporal lobes and hippocampus. T2-weighted MR image showed high signal intensity lesions in the medial temporal lobes, the amygdala, the hippocampus, the insula and the cingulate gyri bilaterally. After the treatment with intravenous acyclovir and betamethasone, impaired consciousness and recent memory disturbance gradually improved. On the second T1-weighted MR image examination, eighteen days after the onset, high signal intensity lesions were demonstrated in the right medial temporal lobe, the right hippocampus, the left insula and the bilateral cingulate gyri. Although the clinical symptoms had improved significantly over three months, the high signal intense lesions on T1-weighted MR images were also detected in the left medial temporal lobe, the right insula, and the straight gyrus. Brain CT did not demonstrate any abnormalities. The repeated CSF examinations showed negative HSV DNA and a decreased number of WBC. However, oligoclonal IgG bands were continuously positive. Myelin basic protein level and IgG index increased in parallel with the expansion of the cerebral lesions on T1-weighted MR images. In the present case, the abnormality of T1-weighted MRI was thought to indicate hemorrhagic inflammatory lesions that could not be detected by CT. The increased level of myelin basic protein, the elevated IgG index and the continuous positive oligoclonal IgG indicated continuous immunologic response against HSV in these lesions.
Acyclovir Betamethasone