Reference values for lower limb nerve ultrasound and its diagnostic sensitivity.

We aimed to establish the cross-sectional area (CSA) reference values for peripheral nerves of lower extremities in a healthy Chinese population, and to determine their diagnostic values for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and Charcot-Marie-Tooth disease type1A (CMT1A). One hundred eleven healthy subjects, 15-70 years of age, as well as 104 CIDP patients and 26 CMT1A patients were recruited. CSA at predetermined sites of the tibial, fibular, sciatic and sural nerves was measured. The CSA of the tibial nerve ranged from 10.2 ± 1.9 to 20.7 ± 3.6 mm2, and for fibular nerve from 8.4 ± 1.8 to 9.5 ± 1.9 mm2. 86% CIDP patients had upper limb nerve enlargement, while only 67% had lower limb nerve enlargement. In CIDP patients with normal upper limb ultrasound, 56% (5/9) would have lower limb nerve enlargement. All CMT1A patients had both upper and lower limb nerve enlargement. Addition of lower limb nerve ultrasound showed no added value in diagnosis of CMT1A, but could be supplementary for CIDP when upper limb ultrasound is normal.