Comparison of high-frequency and ultrahigh-frequency probes in chronic inflammatory demyelinating polyneuropathy

Objectives: High-frequency ultrasound (HFUS 18–20 MHz) performed on patients with chronic inflammatory demyelinating polyneuropathy (CIDP) shows a focal enlargement, particularly in the proximal segments of upper-arm motor nerves. Ultrahigh frequency ultrasound (UHFUS 30–70 MHz), having a higher spatial resolution, enables a better characterization of nerve structures. The aim of this study was to compare the two ultrasound probes in the evaluation of motor nerve characteristics in CIDP patients. Methods: Eleven patients with definite or probable CIDP underwent an ultrasound evaluation of median and ulnar nerves, bilaterally. Nerve and fascicle cross-sectional area (CSA), vascularization, and echogenicity were assessed. Results: Nerve and fascicle CSA were increased in the proximal segments, especially in the median nerve, in 9/11 patients and in 10/11 patients at the HFUS and UHFUS evaluations, respectively. A statistically significant difference between CSA values obtained with the two probes was found only for fascicle values. UHFUS allowed for a more precise estimation of fascicle size and number than the HFUS. We were able to identify nerve vascularization in 4/11 patients at UHFUS only. Conclusion: UHFUS gives more detailed information on the changes in the internal nerve structure in CIDP patients. In particular, it permits to better characterize fascicle size and morphology, and to have a precise estimation of their number. Its frequency range also allows to evaluate nerve vascularization. Significance: Ultrasound evaluation could become an adjunctive diagnostic tool for CIDP. Further studies are needed to validate the examined parameters as biomarkers for the evaluation and follow-up of CIDP patients.