Viral encephalitis: Analysis of 10 cases based on clinical symptoms *
We clinically characterized ten cases of limbic encephalitis in which MRI abnormalities were seen in the limbic system. In nine cases, fever and consciousness disturbance commonly developed and convulsive seizures appeared in seven. Severe amnestic syndrome remained as a sequela in all cases. Cerebrospinal fluid（CSF）at the acute stage revealed mild lymphocytic pleocytosis and an elevated protein level. MRI revealed abnormal signal intensities in both hippocampi and amygdaloid bodies. Regarding etiologies, two cases were positive for herpes simplex virus（HSV）infection. Serum and CSF antibody titers determined by CF and ELISA for HSV were within normal range from the acute to convalescent stages except in one case. Neither the HSV type1 nor 2 DNA genome tested by a sensitive PCR-hybridization method was detected in CSF taken from the acute stage of nine cases. Paraneoplastic limbic encephalitis is known as a subacute encephalitis predominantly involving the limbic system. In our cases, this type of limbic encephalitis was excluded because of the acute onset and lack of malignancy. Accordingly, eight of our cases were regarded as non-herpetic limbic encephalitis of unknown etiology. Several similar cases have been reported in the Japanese population. Further etiological studies should be performed. (Accepted on January 25，2006)
