The importance of peripheral nerve ultrasound in the assessment of hypertrophic neuropathies: How to differentiate leprosy from Charcot-Marie-Tooth 1A?

Objectives This study aims to evaluate the differences in the degree and the distribution of nerve enlargement at multiple sites along the peripheral nerves between patients with Charcot-Marie-Tooth 1A (CMT1A) and patients with primary neural leprosy (PNL). Methods This is an observational analysis of 79 patients with PNL and 20 with CMT1A who underwent ultrasound (US) of peripheral nerves for morphological evaluation and investigation of neural thickening. We evaluated the cross sectional areas (CSA) of the ulnar, median, peroneal, and tibial nerves at several points, through US. Results 72.1% of leprosy patients and 100.0% of CMT had at least one thickened nerve (p = 0.0075). Of the 280 nerves evaluated in CMT, 85.4% were thickened, while of the 1106 assessed in leprosy, 36.5% were altered (p < 0.0001). The average abnormality in CMT was 12.0 thickened nerves/patient and in leprosy 5.1 (p < 0.0001). Asymmetry of 2 or more nerves was observed in 15% in the CMT group and 53.2% in leprosy (p = 0.0022). The CSA averages were higher in CMT in all nerves evaluated (p < 0.0001): median wrist, median pre-wrist, ulnar in the cubital canal, ulnar proximal to the cubital canal, fibular in the head of the fibula, tibial ankle and tibialis in the distal leg. Conclusions Multi-segmental US is helpful for the differential diagnosis of leprosy neuropathy, but neural thickening is not a pathognomonic finding. In leprosy, thickening occurs with an asymmetrical and regional/non-uniform pattern.