High‐Resolution Ultrasound Evaluation of Nerves and Muscles at Multiple Sites in Charcot–Marie–Tooth Disease

Objectives To characterize nerve cross‐sectional area (CSA) and muscle thickness at multiple sites in Charcot–Marie–Tooth disease (CMT) using high‐resolution ultrasound (HRUS), with emphasis on CMT1A and comparisons with healthy controls. Methods Fifty‐nine genetically confirmed CMT patients (including CMT1A, CMT1B, CMTX1, and CMT2A) and 42 healthy controls underwent HRUS evaluation of 7 nerves (median, ulnar, radial, sciatic, tibial, common peroneal, and vagus) at 20 predefined anatomical sites, along with measurements of peroneus longus and tibialis anterior thickness. In CMT1A, we assessed correlations between CSA and clinical severity (Charcot–Marie–Tooth Examination Score [CMTES]), ankle strength, and 15‐month longitudinal changes in CSA. Results Median thicknesses of peroneus longus and tibialis anterior were reduced across CMT subtypes compared with controls (0.99–1.52 versus 1.70 cm and 0.94–1.95 versus 2.64 cm, respectively; all p < .05). CMT1A showed significantly larger CSA at all 20 sites compared with controls (all p < .001), whereas no significant CSA differences were observed in CMT1B, CMTX1, or CMT2A. In CMT1A, no site‐specific CSA correlated significantly with CMTES, muscle thickness, or ankle strength. Over 15 months, small but significant CSA increases were observed at selected nerve sites in CMT1A, with the largest increase (0.07 cm 2 ) at the upper‐arm segment of the median nerve ( p = .04). Short‐axis HRUS at superficial nerve segments revealed a beaded “fusion–separation–refusion” fascicular appearance in 16 of 42 CMT1A patients (38.1%). Conclusions HRUS demonstrates a diffuse nerve enlargement pattern in CMT1A and muscle atrophy across CMT subtypes. Short‐term CSA changes were minimal, suggesting HRUS CSA is more informative for subtype characterization than for short‐interval progression monitoring.