A panorama of radial nerve pathologies- an imaging diagnosis: a step ahead

Abstract

The radial nerve has a long and tortuous course in the upper limb. Injury to the nerve can occur due to a multitude of causes at many potential sites along its course. The most common site of involvement is in the proximal forearm affecting the posterior interosseous branch while the main branch of the radial nerve is injured in fractures of the humeral shaft. Signs and symptoms of radial neuropathy depend upon the site of injury. Injury to the nerve distal to innervation of triceps brachii results in loss of extensor function with sparing of function of the triceps resulting in the characteristic ‘wrist drop’. Injury in the mid-arm is associated with loss of sensation in the dorsolateral aspect of the hand, the dorsal aspect of the radial three-and-a-half digits and in the first web space. Involvement of only the posterior interosseous nerve (PIN) results in weakness of the wrist and digit extensors. Diagnosis relies on clinical examination, electrodiagnostic studies and imaging findings. Plain radiographs are used to identify fracture sites, callus or tumours as cause of compression. Technological advances in ultrasonography have allowed direct visualisation of the involved nerve with assessment of the exact site, extent and type of injury. It yields unmatched information about anatomical details of the nerve. MR imaging adds to soft-tissue details and helps in characterising the lesion. This pictorial review aims to illustrate a wide spectrum of causes of radial neuropathy and emphasises the importance of imaging modalities in diagnosis of neuropathies.Teaching Points• Radial nerve injuries are assessed by clinical examination and diagnosed using electrodiagnostic and imaging studies.• Knowledge of anatomical relations and course of the nerve is necessary to identify the nerve at pre-determined anatomical locations.• Altered echogenicity and signal intensity, discontinuity of the nerve, focal thickening and cause of compression can be assessed by imaging modalities.• MR imaging helps in confirmation of the ultrasound findings, differentiating similar appearing lesions and provides additional soft-tissue details.

Can imaging be the new yardstick for diagnosing peripheral neuropathy?—a comparison between high resolution ultrasound and MR neurography with an approach to diagnosis

“…This grade VI injury is as a mixed type of injury which denotes various types of injuries across the cross section of the nerve [4–6]. The different types of injuries are illustrated in Table 1 along with their imaging findings [7].…”

Intermuscular Connections in Anterior Brachium: its Implications in Radial Nerve Entrapment Neuropathy

“…These observations will definitely have implications in clinical setting and radiologic interpretation including ultrasound diagnosis. The application of high-resolution ultrasound in peripheral nerve entrapment is becoming popular in western nations (22,23). The portable ultrasound machines are less expensive in comparison to MRI machine and can be performed by non-radiologists as well (24), hence the cost is very economical to the patient.…”

“…During the ultrasound, the nerve can be identified as honeycomb appearance, which differentiates it from the adjacent soft tissue. The nerve gives more echo to the adjacent muscle and less to the adjacent tendon (22). It is believed that if the radiologist has prior knowledge about the adjacent anomalous muscles and tendons, it will help in more accurate interpretation.…”

“…The further course of the radial nerve in relation to the supinator muscle is not studied. These details have implications in understanding the radial tunnel syndrome, where the nerve entrapment happens in the arcade of Frohse (22). The relation of radial nerve and supinator muscle is very important because the commonest structural entrapment neuropathy of radial nerve is compression by the superficial fibers of supinator.…”

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound – Part I: Extraarticular Pathologies

“…Expanding evidence has supported the use of US as a valuable imaging modality to investigate the peripheral nervous system [249][250][251][252]. In the short axis, normal peripheral nerves demonstrate a characteristic stippled (honeycomb-like) appearance (axons arranged in fascicles and multiple layers of connective tissue supporting and binding the fascicle bundles together) [253].…”