[An adult case of acute cerebellitis after influenza A infection with a cerebellar corical lesion on MRI].

We report an adult case of acute cerebellitis associated with influenza A. A 25-year-old woman with fever and headache was diagnosed as having influenza A infection, because nasal swab extract was found positive in the influenza assay. She was treated with oseltamivir. After the treatment, she gradually developed gait and speech disturbance. Neurological examination revealed dysarthria with scanning slurred speech, and limb and truncal ataxia. Cerebrospinal fluid showed pleocytosis and a four-fold or greater change in the antibody titer to influenza virus A (H3N2) detected by HI. T2-weighted brain MRI demonstrated a high signal lesion in the cerebellar cortex. 123I-IMP-SPECT showed hypoperfusion in the cerebellum. Thus, acute cerebellitis associated with influenza A infection was diagnosed. Her symptoms partially improved after steroid pulse therapy, whereas the cerebellar cortical lesion observed on MRI, truncal ataxia and cerebrospinal fluid pleocytosis remained. The cerebellar cortical lesion observed on MRI disappeared 80 days after hospitalization, and the truncal ataxia and cerebrospinal fluid pleocytosis had normalized about three months later.