MR imaging of the treated brachial plexus.

Abstract

toms of these patients. MR imaging is the technique of choice for imaging the brachial plexus. MR imaging is superior to CT and sonography because of its multiplanar capabilities and excellent soft-tissue contrast that allows visualization of the branches of the brachial plexus from their origin at the cervical spinal cord to the trunks and cords as they traverse the axillary and supraclavicular regions. The normal and abnormal brachial plexus as seen by MR imaging have been described [3, 4]. We describe MR imaging findings in patients who have undergone surgery and radiation therapy and/or chemotherapy and who subsequently have brachial plexopathy or peripheral neuropathy. to help characterize these changes noninvasively. Normal Anatomy and Imaging Parameters The brachial plexus provides sensory and motor innervation to the upper extremity. The brachial plexus forms in the posterior triangle of the neck by the union of the anterior rami of the fifth, sixth, seventh, and eighth cervical spinal nerves and the first thoracic spinal nerve. The exiting roots pass between the anterior and middle scalene muscles to form three trunks. These trunks each divide into anterior and posterior divisions that are just superior to the subclavian artery. These divisions subsequently unite to form three cords that are named according to their relationship to the axillary artery (i.e., the posterior, the medial, and the lateral cords). At our institution, imaging parameters include TIand T2-weighted scans in coronal, axial, and sagittal planes to include the cervical spine. A neck or surface coil permits better visualization of the cervical spinal cord and exiting roots. The body coil is then used to image more distal features. including the axilla. Sagittal images are particularly helpful in following the course of the brachial plexus (Fig. 1). Metastatic Tumor Metastatic lymphadenopathy of the axillary or supraclavicular regions is a relatively frequent occurrence, especially with breast carcinoma. Lymph node masses may surround the neurovascular bundle, resulting in vascular or neural compromise. Lymphadenopathy as the cause of brachial plexopathy is generally easily shown as masses f3-5]. The nodes are usually isointense to muscle on TI-weighted images and hyperintense on T2-weighted images (Figs. 2 and 3). Treated nodes may show decreased signal intensity on all pulse sequences. The decreased signal intensity likely corresponds to fibrosis or scarring (Fig. 4). Infiltrative tumor (Fig. 5) may be more difficult to detect. Thickening and enhancement of the nerves may be seen; however, that is a nonspecific finding and may be seen after surgery or radiation therapy. Close follow-up may be necessary in these patients. It is important to image the entire brachial plexus, including the roots, trunks, and cords, because metastatic disease to the spine with epidural extension and spinal cord or nerve root compromise may be missed if images of the cervical spinal cord are not