Identification of pathology involving the brachial plexus requires a detailed understanding of the complex brachial plexus anatomy. Brachial plexopathies can be divided into traumatic and non-traumatic categories and further categorized by location of involvement. Diagnosis of brachial plexopathies requires detailed medical history and physical examination, however medical imaging such as CT, MRI and ultrasound can be utilized to confirm diagnosis, assist with prognostication and guide surgical planning.

Traumatic brachial plexus injuries can be described by injury mechanism (penetrating or blunt), location (preganglionic or postganglionic) and severity. Preganglionic and postganglionic injuries are based on whether the injury is proximal or distal to the dorsal root ganglia. Postganglionic injuries occur in the peripheral nervous system and most often manifest as nerve rupture in the upper nerve roots (C5-C7). These injuries carry a better prognosis, with more surgical options that include nerve repair or grafting and a higher likelihood for nerve regeneration. Preganglionic injuries in the central nervous system have a worse prognosis, most often manifesting as nerve root avulsions in the C8-T1 roots. Traumatic injuries can occur because of blunt trauma, penetrating trauma, traction, compression or vascular discontinuity. In newborns,  shoulder dystocia is considered the number one risk factor for traumatic brachial plexopathy. The most common clinical syndromes include Duchenne-Erb palsy (upper brachial plexus) and Klumpke palsy (lower brachial plexus palsy).

Nontraumatic brachial plexopathy includes inflammatory, compressive and neoplastic etiologies. Inflammatory causes for brachial plexopathy include radiation, infection, post-traumatic and metabolic abnormalities. Radiation induced brachial plexopathy mostly commonly occurs in the setting of radiation treatment for lung, breast, head and neck cancers and can present as early transient radiation induced plexopathy or classic progressive radiation plexopathy, which can have a latency period of 6 months to 30 years. Tumors affecting the brachial plexus are uncommon and include benign and malignant etiologies such as peripheral nerve sheath tumors, malignant peripheral nerve sheath tumors, and metastases.

Imaging modalities that may assist in the diagnosis of brachial plexopathy include ultrasound, CT and MR imaging. Ultrasonography is noninvasive, cost effective and can be used for dynamic assessment of the postganglionic brachial plexus, which is relatively superficial on examination. CT Myelography can use utilized to assess for preganglionic injury which on imaging may demonstrate avulsion pseudomeningocele, hematoma, or other sequelae of trauma. MRI is generally preferred over CT for evaluation of brachial plexus injury due to its higher soft tissue resolution and improved visualization of the structures of the plexus. MRI findings suggestive of brachial plexopathy include, edema, myelomalacia, root avulsion, pseuodomeningocele, cord edema, nerve transection and scarring which manifest as T2 hyperintense signal abnormality and post-contrast enhancement (Figure 4). 

Creating three-dimensional clay models as a hands-on educational tool can enhance medical student and resident understanding of the challenging anatomy of the brachial plexus. This active learning technique allows learners to manipulate and visualize the spatial relationships within the plexus which may ultimately improve comprehension and retention when compared to traditional learning methods.