High‐resolution sonography of the peripheral nervous system – a review of the literature

Abstract

High-resolution sonography is capable of depicting peripheral nerves and the brachial plexus. In this study we review the literature on this subject. Normal peripheral nerves have a characteristic echotexture. Most nerves are readily visualized, although this is not always the case with the nerves of the lower extremity. The main pathological changes that can be demonstrated are nerve enlargement and increased hypoechogenicity. In order to demonstrate nerve enlargement, measurements should be performed and compared with a set of reference values. Several neuropathies have been studied by means of ultrasonography. However, many studies concern case reports and show methodological shortcomings. The best studied peripheral neuropathy is the carpal tunnel syndrome in which ultrasonography seems to have an additional value when combined with nerve conduction studies. Nerve enlargement has also been demonstrated in radial neuropathy at the humerus and in ulnar neuropathy at the elbow. The role of sonography in various hereditary and inflammatory neuropathies is uncertain although diffuse nerve thickening could be demonstrated. Further systematic studies are needed to determine the role of sonography in the diagnostic process of the various neuropathies. It would be important to study the subcategories of patients in whom electrodiagnostic studies are normal or show equivocal findings.

Ultrasonography of MADSAM neuropathy: Focal nerve enlargements at sites of existing and resolved conduction blocks

“…Ultrasonography measurements provide useful complementary information to electrodiagnostic data. 1 Sonographic diffuse or multifocal nerve enlargement were reported in various demyelinating polyneuropathies, such as chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN), and some hereditary polyneuropathies. [2][3][4][5][6] Previous studies described swelling of a single hypoechoic fascicle resulting in focal enlargement of nerve diameter at sites of concurrent conduction blocks in CIDP patients.…”

Ultrasound of the nerves of the knee region: Technique of examination and normal US appearance

“…The nerves of the knee region can be visualized clearly with US because of their relatively superficial location. In experienced hands, US can be a reliable, noninvasive tool for PN imaging that is also highly cost-efficient [2,6,10,11].…”

Imaging of peripheral nerve tumors

“…17 Similar to MR imaging, ultrasonography may be used to visualize the patterns associated with various tumor types. 1,19,23 For example, neurofibromas tend to enhance heterogeneously on ultrasonography and have a higher echogenicity in the center than on the periphery. This pattern on imaging, also called the target sign, has been correlated with the benign nature of a tumor.…”