MR anatomy of the substantia innominata and findings in Alzheimer disease: a preliminary report.

PURPOSE To demonstrate normal MR anatomy of the substantia innominata and its changes in Alzheimer disease on MR imaging. METHODS Using a 1.5-T superconductive MR unit, thickness of the substantia innominata was measured on coronal thin-section images obtained in 22 patients with Alzheimer disease and 14 age-matched control subjects. Comparison of these images with postmortem specimens of human brain was also performed. RESULTS On T2-weighted images through the anterior commissure, the substantia innominata was clearly identified between the globus pallidus and the anterior perforated substance. In Alzheimer disease, thinning of the substantia innominata was more frequently observed than in the age-matched controls. CONCLUSION Thin-section T2-weighted coronal MR images can demonstrate shrinkage of the substantia innominata, a finding that may aid in the diagnosis of Alzheimer disease.