Neurological complications after H1N1 influenza vaccination: magnetic resonance imaging findings

Objective: To report 4 different neurological complications of H1N1 virus vaccination. Method: Four patients (9,16, 37 and 69 years of age) had neurological symptoms (intracranial hypertension, ataxia, left peripheral facial palsy of abrupt onset, altered mental status, myelitis) starting 4-15 days after H1N1 vaccination. MRI was obtained during the acute period. Results: One patient with high T2 signal in the cerebellum interpreted as acute cerebellitis; another, with left facial palsy, showed contrast enhancement within both internal auditory canals was present, however it was more important in the right side; one patient showed gyriform hyperintensities on FLAIR with sulcal effacement in the right fronto-parietal region; and the last one showed findings compatible with thoracic myelitis. Conclusion: H1N1 vaccination can result in important neurological complications probably secondary to post-vaccination inflammation. MRI detected abnormalities in all patients.