[Magnetic resonance imaging of the brachial plexus. Anatomy].

The brachial plexus is a difficult region to evaluate with radiological techniques. MR imaging has great potentials for the depiction of the various anatomical structures of the brachial plexus--i.e., spinal ganglion, ventral nerve rami root exit of the neural foramina, trunks and cords. Moreover, MR imaging, thanks to its direct multiplanarity, to its excellent soft-tissue contrast, and to its lack of motion artifacts, allows good evaluation of pathologic conditions in the brachial plexus, especially traumas and cancers. On the contrary CT, in spite of its high spatial resolution and good contrast, cannot demonstrate the anatomical structures of the brachial plexus. US detects superficial structures, and conventional radiographs depict only indirect changes in the adjacent lung apex and skeletal structures. From November 1989 to May 1990, 20 normal volunteers (15 males and 5 females; average age: 35 years) were studied with MR imaging. Multisection technique was employed with a dedicated coil and a primary coil. The anatomical structures of the brachial plexus were clearly demonstrated by T1-weighted sequences on the sagittal and the axial planes. T2-weighted pulse sequences on the coronal plane were useful for the anatomical definition of the brachial plexus and for eventual tissue characterization. The correct representation of the anatomical structures of the brachial plexus allowed by MR imaging with our standard technique makes MR imaging the most appropriate exam for the diagnosis of pathologic conditions in the brachial plexus, although its use must be suggested by specific clinical questions.