Progress in the nerve ultrasound of inflammatory peripheral neuropathies

Objective: In recent years, high-resolution nerve ultrasound has been increasingly used as a complementary tool to nerve conduction studies in the diagnosis of peripheral neuropathies. Inflammatory peripheral neuropathies include a heterogeneous group of neuropathies mainly including chronic inflammatory demyelinating polyneuropathies (CIDP), multifocal motor neuropathy (MMN), systemic vasculitic neuropathy (SVN), and Guillain-Barre syndrome (GBS). We describe the ultrasonic characteristics of different inflammatory neuropathies. Data sources and study selection: The MEDLINE database was searched to find studies on nerve sonography in inflammatory peripheral neuropathies. Reported studies up to December 2022 were included in this review. Results: In neuropathies, the changes in ultrasound include enlarged nerve size, nerve echo-intensity, fascicle diameter and vascularity. Most CIDP patients have moderately enlarged CSA, some have dramatically enlarged CSA, and few have CSA within the normal range. Since the enlargement patterns are different, ultrasound is useful to help differentiate CIDP from CMT1. In follow-ups after immune treatment, nerve CSAs in CIDP could decrease, increase, or remain unchanged. Regional enlargement next to normal segments predominated in MMN. Nerve enlargement and hyper vascularization were found in vasculitic neuropathy. In GBS patients, there were enlarged peripheral nerve and nerve roots, which became normal at follow-up. Conclusions: High-resolution nerve ultrasound is complementary to the diagnosis of inflammatory peripheral neuropathies. CSA enlargement and its distribution are the most useful and quantifiable parameters in the evaluation of peripheral nerves. For patients suspected to have inflammatory neuropathies, we advise measuring the CSA of several pre-determined sites in the median, ulnar nerve, C5-8 cervical roots, and brachial plexus.