[Clinical characteristics of non-herpetic limbic encephalitis].

In Japan,the prevalence of non-herpetic acute limbic encephalitis (NHALE),characterized by a lack of evidence of the herpes simplex virus (HSV) genome or enzyme-linked immunosorbent assay (ELISA) antibody,has shown an upward trend. The causes of NHALE include several anti-neural antibodies related NHALE. Among them,NHALE that is characterized by the onset of abnormal behavior and presence of anti-glutamate receptor epsilon2 (GluRepsilon2) antibody is gaining attention. NHALE was identified in 1994 during a survey of herpes simplex encephalitis in Kyushu District. This disease has not been reported in individuals belonging to countries other than Japan. In this review article,3 cases of NHALE patients with positive GluRepsilon2 antibody titers and ovarian-teratoma-related anti-N-methyl-D-aspartate receptor (NMDAR) antibody-positive encephalitis are briefly described. In addition,the naming of this disease as well as its pathogenesis,clinical features, prognosis, and sequels are discussed in this report. Patients in the acute stage of NHALE frequently exhibited schizophrenic-like symptoms such as abnormal behavior, incoherence, delusions, and hallucinations followed by convulsive seizures, status epilepticus, and autonomic seizures. Mild signs of meningeal irritation were also detected. Magnetic resonance imaging (MRI) in these patients often revealed bilateral abnormalities in the limbic areas, including the hippocampus and amygdala. Examination of the cerebrospinal fluid (CSF) revealed mild pleocytosis, and sometimes, a lack of the pleocytosis. The CSF level of interferon-gamma remained unchanged, whereas that of interleukin-6 was increased. The prognostic outcome of the patients was rather favorable. Further, differential diagnosis for herpes simplex encephalitis is important in order to decide the initial treatment-antiviral drug therapy or immunological therapy. The most commonly described sequel of this condition is memory impairment; however,patients should be monitored for personality or emotional changes.