MR Imaging of Nontraumatic Brachial Plexopathies: Frequency and Spectrum of Findings1

Magnetic resonance imaging is the method of choice for evaluating patients with a nontraumatic brachial plexopathy. Although there is a wide range of disease processes that may cause a brachial plexopathy, radiation fibrosis, primary and metastatic lung cancer, and metastatic breast cancer account for almost three-fourths of the causes. Radiation fibrosis, the most common cause in our series, may occur several months to years after the completion of therapy. Findings of radiation fibrosis include ( a ) thickening and diffuse enhancement of the brachial plexus without a focal mass and ( b ) soft-tissue changes with low signal intensity on both T1- and T2-weighted images. Lung cancer arising in the lung apex may invade the lower portion of the brachial plexus. Many tumors may metastasize to the brachial plexus, causing a brachial plexopathy. Breast cancer is the most likely to metastasize because major lymphatic drainage routes for the breast course through the apex of the axilla.