Nerve entrapment syndromes of the upper limb: a pictorial review

Peripheral nerves of the upper limb may become entrapped at various points during their anatomical course. While physical examination and nerve conduction studies are the mainstay of diagnosis, there are multiple imaging options, specifically ultrasound and magnetic resonance imaging (MRI), which offer important information about the potential cause and location of nerve entrapment that can help guide management. This article overviews the anatomical course of various upper limb nerves, including the long thoracic, spinal accessory, axillary, suprascapular, radial, median, ulnar, and musculocutaneous nerves, and describes the common locations and causes of entrapments for each of the nerves. Common ultrasound and MRI findings of nerve entrapments, direct or indirect, are described, and various examples of the more commonly observed cases of upper limb nerve entrapments are provided.