We report two cases of non-herpetic acute
limbic encephalitis (NHALE) which showed elevation of
interleukin (IL)-6 in the cerebrospinal fluid (CSF). [Case 1] The patient was a 25-year-old woman who was admitted to another hospital because of
fever and severe
headache, following
common cold. After the admission, she developed severe disturbance of consciousness and suffered from generalized convulsions, and was then transferred to our hospital. The CSF examination revealed neither
pleocytosis nor elevation of total
protein. Her consciousness improved by
intravenous administration of high-dose
methylprednisolone, but mild
retrograde amnesia and symptomatic
epilepsy remained as sequelae. [Case 2] The patient was a 58-year-old man who was admitted to our hospital because of
fever, severe
headache, and mild disturbance of consciousness, following
common cold. After the admission, he exhibited marked psychiatric symptoms and severe amnestic syndrome. The CSF examination revealed mild lymphocytic
pleocytosis and mild elevation of total
protein. His clinical symptoms improved markedly by
intravenous administration of high-dose
methylprednisolone, but mild
retrograde amnesia and personality changes remained. Cranial MRI showed reversible high signal intensity lesions in bilateral hippocampi and amygdaloid bodies on diffusion weighted images (DWI) in both cases. No laboratory findings suggesting
herpes simplex virus infection or
malignancy were detected in either case. In the CSF analysis of
cytokines including
IL-1 beta,
IL-2,
IL-6,
IL-10,
tumor necrosis factor alpha, and interferony gamma, only
IL-6 was elevated in both cases. We recognized four clinical features in both cases as follows: 1. the episode of preceding
infection such as
common cold, 2. appearance of reversible high signal intensity lesions in bilateral hippocampi and amygdaloid bodies on DWI, 3. elevation of only
IL-6 in CSF, and 4. marked neurological improvement by
intravenous administration of high-dose
methylprednisolone. We speculate that the immune reaction of the host might play some significant roles in the pathogenesis of NHALE, based on these four clinical features.