Nerve Ultrasound Is an Accurate Diagnostic Tool for Chronic Inflammatory Neuropathies

January 29, 2020

New study data showed nerve ultrasound had a sensitivity of 97.4% and specificity of 78.9%, with an added value in the detection of treatment-responsive chronic inflammatory neuropathy of 21.1%.

Ludo Van der Pol, MD, PhD

New study data had provided Class IV evidence that nerve ultrasound can be an accurate diagnostic tool in the detection of chronic inflammatory neuropathies and could thus improve the identification of patients who may respond to treatment.

Led by Ludo Van der Pol, MD, PhD, associate professor of neurology, and head, the Netherlands Spinal Muscular Atrophy Center, University Medical Center Utrecht, the study assessed 100 consecutive incident patients with clinically suspected chronic inflammatory neuropathy, ultimately findings that nerve ultrasound was both sensitive and specific in identifying those with a diagnosis, working in a supplementary fashion to extensive standardized nerve conduction studies (NCS).

Ultimately, 38 patients had a clinically confirmed diagnosis of either chronic inflammatory demyelinating polyneuropathy (CIDP; n = 20), Lewis Sumner syndrome (LSS; n = 4), or multifocal motor neuropathy (MMN; n = 14). Nerve ultrasound and NCS had a sensitivity of 97.4% and 69.4%, respectively, and specificity of 78.9% and 93.5%, respectively. The added value of nerve ultrasound in the detection of treatment-responsive chronic inflammatory neuropathy was 21.1% compared to NCS alone.

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In total, nerve ultrasound had positive results for 37 of the 38 clinically diagnosed patients, compared to 30 for NCS. Of the 62 patients who were not clinically diagnosed, nerve ultrasound correctly identified 43 (69.4%), while NCS identified 58 (93.5%). The negative and positive predictive values calculated for nerve ultrasound and NCS were 97.7% and 87.9%, and 66.1% and 88.2%, respectively.

“Nerve ultrasound and NCS test characteristics differ, with superior sensitivity in the former and specificity in the latter,” Van der Pol and colleagues wrote. “These investigations are therefore complementary rather than comparable techniques in the diagnostic workup of chronic inflammatory neuropathy.”

Van der Pol and colleagues noted that while the sensitivity of NCS and nerve ultrasound were comparable, the specificity of nerve ultrasound was lower than prior reports, caused by a higher number of false-positive sonographic test results. “The use of nerve ultrasound allows the detection of additional patients who will respond to treatment at the expense of some false positives. This implies that nerve ultrasound and NCS can best be used as complementary techniques,” the authors noted.

The data were collected between February 2015 and July 2018, with all patients undergoing nerve ultrasound, extensive standardized NCS studies, and other relevant diagnostic investigations. The evaluation of treatment response was done using predefined criteria. Diagnoses of chronic inflammatory neuropathy were established when NCS was abnormal—meeting the European Federation of Neurological Societies/Peripheral Nerve Society criteria of demyelination—or when the degree of nerve enlargement detected by sonography was compatible with chronic inflammatory neuropathy in addition to treatment response.

There were some limitations to the work, including that not all of the 100-patient cohort received treatment. Additionally, the physicians who assessed treatment response were not blinded for the results of both nerve ultrasound and NCS due to the study design; and the treating physician was free in his or her treatment decisions, opening the door for small differences in treatment protocol between patients.

“[The] addition of nerve ultrasound significantly improves the detection of chronic inflammatory neuropathies,” Van der Pol and colleagues concluded. “Therefore, it deserves a prominent place in the diagnostic workup of chronic inflammatory neuropathies.”

REFERENCE

Herraets IJT, Goedee HS, Telleman JA, et al. Nerve ultrasound improves detection of treatment-responsive chronic inflammatory neuropathies. Neurology. Published online January 20, 2020. doi: 10.1212/WNL.0000000000008978.