Nerve Ultrasound Accurate for Detecting Chronic Inflammatory Neuropathy

A nerve ultrasound may be highly accurate for detecting chronic inflammatory neuropathy (CIN) and predicting response to treatment, according to study results published in Neurology.

Nerve conduction studies are the main diagnostic tool to differentiate between chronic inflammatory neuropathies (such as chronic inflammatory demyelinating polyneuropathy [CIDP], Lewis Sumner syndrome, and multifocal motor neuropathy [MMN]) and axonal polyneuropathies and amyotrophic lateral sclerosis.  While nerve ultrasound protocols have previously displayed high sensitivity and specificity for diagnosis of CINs, these studies lacked an unbiased approach.

The goal of the current study was to confirm the diagnostic accuracy of a previous short sonographic protocol for CINs, as well as to compare the ability to detect treatment responsive patients between nerve ultrasound and nerve conduction studies.

This prospective multicenter study included 100 consecutive patients (73 men; mean age, 60.7±12.6 years) with clinically suspected CIN who were enrolled in 3 hospitals in The Netherlands. All participants underwent a neurological examination, laboratory tests, nerve conduction studies, and nerve ultrasound. The sonographic protocol included 5 nerve sites: the median nerve at the forearm and arm and C5, C6, and C7 nerve roots.

Study researchers determined diagnostic accuracy according to the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria as reference standard. Additionally, they used an alternative reference standard based on the clinical findings of CIDP/MMN, abnormal ultrasound results, and response to treatment. They determined response to therapy based on the discretion of the treating physician.

Of the study participants, 39 were diagnosed with CIN according to the reference standard. Of these, 33 participants were diagnosed according to the nerve conduction study criteria of the EFNS/PNS. Sonographic protocol A had a pooled sensitivity and specificity for CIN diagnosis of 96.4 percent and 40 percent, respectively; those for sonographic protocol B were 87.4 percent and 67.3 percent, respectively. 

According to the alternative reference, the pooled sensitivity and specificity of nerve ultrasound for CIN diagnosis were 96.4 percent and 44.9 percent, respectively, for sonographic protocol A, and 84.6 percent and 72.8 percent, respectively, for sonographic protocol B. Regarding nerve conduction studies, the pooled sensitivity and specificity according to the alternative reference  were 76.1 percent and 93.4 percent, respectively

While nerve conduction studies supported CIN diagnosis in 33 participants, the addition of nerve ultrasound was able to identify 11 (11 of 44, 25%; 95% CI, 13.2-40.3%) additional patients with treatment-responsive CINs.

The study had several limitations, including logistic limitations that precluded blinding, variations between centers in nerve conduction study protocols, use of different sonography devices, and treatment response determined by discretion of the treating physician.

“We show that a short sonographic protocol has a high sensitivity, but a low specificity to identify patients with chronic inflammatory neuropathies in a multicenter study setting,” the study researchers concluded.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Herraets IJT, Goedee HS, Telleman JA, et al. Nerve ultrasound for diagnosing chronic inflammatory neuropathy: a multicenter validation study. Neurology. Published online July 16, 2020. doi: 10.1212/WNL.0000000000010369