Patterns of intracranial signal intensity on magnetic resonance (MR) images were studied in nine patients undergoing long-term total parenteral nutrition therapy. The duration of therapy ranged from 5 months to 11 years (mean, 5.3 years). Symmetric increased signal intensity on T1-weighted MR images (hyperintense relative to white matter) was observed in the basal ganglia of all patients, without corresponding abnormality on T2-weighted images. Analysis of signal-intensity characteristics and distribution pattern suggests that the basis for these changes may be deposition of intravenously administered paramagnetic trace elements, especially manganese, and/or an astrogliotic reaction to such deposition.