Distinctive patterns of sonographic nerve enlargement in Charcot-Marie-Tooth type 1A and hereditary neuropathy with pressure palsies

Objective: The extent of sonomorphologic differences of peripheral nerves between CMT and HNPP is unknown. Methods: We recruited 9 patients with CMT-1A and 9 with HNPP. Patients underwent a standardized sonographic protocol, which evaluated nerve size and vascularization. We quantitatively assessed fascicle size and echogenicity. Results: All 18 patients demonstrated nerve enlargement, but no increased vascularization. HNPP demonstrated larger nerves at sites of entrapment (median nerve at the carpal tunnel p = 0.049, ulnar nerve at the sulcus p < 0.001), greater swelling ratios of median (p < 0.001), ulnar (p = 0.017) and fibular nerve (p = 0.005) than CMT-1A. CMT-1A revealed larger nerves proximal to sites of entrapment (median and fibular nerve, brachial plexus p < 0.001). Nerve fascicles where larger (p < 0.001) and more hypo-echogenic in CMT-1A. Nerve, fascicle size nor echogenicity correlated with age, gender or MRC sum-score. Conclusions: Ultrasonography of nerves reveals specific phenotypes differentiating CMT-1A from HNPP. In CMT-1A enlargement of nerves and fascicles is multifocal among multiple nerves, whereas in HNPP nerve enlargement is restricted to sites of entrapment. Significance: Our findings of specific sonomorphological phenotypes, differentiating CMT-1A from HNPP, may help to improve our pathophysiological insights in CMT and HNPP. (C) 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.