Brachial and Lumbosacral Plexus and Peripheral Nerves

Interpreting imaging studies of peripheral nerve diseases and especially the brachial plexus (BP) and lumbosacral plexus (LSP) can be challenging. It requires a firm knowledge of the anatomy. It is just as important to be familiar with the end-organ innervations and the surrounding structures, the latter serving as important landmarks. Magnetic resonance imaging (MRI) is the main imaging modality of the BP and LSP. High resolution T1-weighted and homogeneous fat-saturated T2-weighted sequences are fundamental sequences in the MRI protocol. More advanced techniques with three-dimensional (3D) sequences such as T2-SPACE and SPACE-SPAIR with 3D maximum intensity projections can be used to visualize the BP and LSP in different planes. Contrast can help in identifying neoplastic processes and the extent of inflammatory processes. This chapter will review the anatomy of the BP and LSP and provide helpful clues to identify the normal and pathologic nerves on MRI. The imaging findings of different traumatic and non-traumatic pathologies (inflammatory, infectious, neoplastic processes) are presented.