Acute cerebellar ataxia with abnormal MRI lesions after varicella vaccination.

A 2-year-old boy, with the primary difficulties of nausea and vomiting, developed a staggering gait and dysarthria 10 days after varicella vaccination. Magnetic resonance imaging demonstrated multiple areas of high signal intensity in the white matter of the cerebellum, predominantly in the parieto-occipital white matter and both globus pallidi. He did not present any signs of myelitis or encephalitis and thus his cerebellar dysfunction was diagnosed as acute cerebellar ataxia, which is, generally speaking, not an etiologic entity but a clinical syndrome. Magnetic resonance imaging may reveal a variety of abnormalities of the central nervous system in acute cerebellar ataxia.