Acute cerebellar ataxia after influenza vaccination with recurrence and marked cerebellar atrophy.

A 5-year-old, previously healthy girl developed symptoms and signs of acute cerebellar ataxia (ACA) 8 days after having received an influenza vaccination. Brain CT was normal, but the CSF showed moderate pleocytosis. Symptoms almost disappeared within 4 months. Thirty-three months later, cerebellar symptoms recurred without apparent preceding episode, and persisted. Sixteen months after the recurrence of ataxia, CT and MRI revealed marked cerebellar atrophy. No further augmentation of ataxia or of cerebellar atrophy was observed during following 30 months. The patient appears to be the first documented case of ACA with recurrence of ataxia and severe atrophy of the cerebellum, though the etiology and pathogenesis are still to be determined. Clinical pictures and the course of the patient were compared with follow-up data on 8 cases of ACA.