An autopsy case with non‐herpetic acute limbic encephalitis (NHALE)

Non‐herpetic acute limbic encephalitis (NHALE) is a cause‐unknown, inflammatory disease entity that affects the limbic system restrictedly. Neuropathological changes of NHALE have been described in only one report. A 53‐year‐old Japanese woman developed high fever, disturbance of consciousness and intractable generalized convulsions. Her symptoms were resistant to aggressive therapy including corticosteroid, acyclovir, γ‐globulin and anticonvulsants, and progressed acutely, leading to status epilepticus at 6 days after the onset. Brain MRI revealed inflammatory changes restricted to the limbic system. Herpes encephalitis was excluded by laboratory tests. Although paraneoplastic limbic encephalitis could not be excluded completely, no tumor lesions were detected on chest CT and abdominal ultrasonography. The patient died of multiple organ failure at 34 days after the onset of the disease. Histologically, there were neuronal loss and severe gliosis with an increase in hypertrophic astrocytes and with perivascular cuffings around several small blood vessels restricted to the hippocampus and the amygdala. Immunohistochemically, macrophages and activated astrocytes were distributed more widely over the limbic system, namely internal capsule, thalamus, caudate nucleus and substantia nigra. Herpes simplex virus I(1)and II(2) were negative immunohistochemically. The neuropathological findings of this case were similar to that of the previous report. NHALE is supposed to be a distinct disease entity neuropathologically and the fulminant form of NHALE exists.