Nerve Ultrasound Protocol to Detect Dysimmune Neuropathies.

Nerve ultrasound is increasingly used in the differential diagnosis of polyneuropathy as a complementary tool to nerve conduction studies. Morphological alterations of the peripheral nerves, such as increasing the cross-sectional area (CSA), have been described in various immune-mediated polyneuropathies. The most prominent morphological changes in nerve ultrasound have been described for the chronic inflammatory demyelinating polyneuropathy (CIDP)-spectrum disease. CIDP may be distinguished from hereditary and other polyneuropathies by measuring the extent and pattern of nerve swellings (CSA increase). Typical findings in demyelinating inflammatory neuropathies are multifocal nerve swellings with inhomogeneous fascicular structure, while CSA increase in demyelinating hereditary neuropathies occurs in a more generalized and homogenous manner. In other non-inflammatory axonal neuropathies, nerves can appear with normal or slight CSA increases, especially in typical entrapment sites. This article presents technical requirements for nerve ultrasound, an examination procedure using a standardized examination protocol, current reference values for the CSA, and typical sonographic pathological findings in patients with inflammatory neuropathies.