Reference values for lower limb nerve ultrasound and its diagnostic sensitivity

Area of Science:

• Neuroscience
• Medical Imaging
• Clinical Neurology

Background:

• Establishing normative reference values for peripheral nerve cross-sectional area (CSA) is crucial for diagnosing neuropathies.
• Peripheral nerve ultrasound is a key diagnostic tool, but lower extremity reference values in healthy Chinese populations are not well-defined.
• Differentiating neuropathies like chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and Charcot-Marie-Tooth disease type 1A (CMT1A) requires accurate diagnostic criteria.

Purpose of the Study:

• To establish reference values for the cross-sectional area (CSA) of lower extremity peripheral nerves in a healthy Chinese population.
• To evaluate the diagnostic utility of lower extremity nerve ultrasound in identifying chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and Charcot-Marie-Tooth disease type 1A (CMT1A).
• To determine if lower limb nerve ultrasound provides supplementary diagnostic information for CIDP and CMT1A.

Main Methods:

• Recruited 111 healthy subjects (15-70 years), 104 CIDP patients, and 26 CMT1A patients.
• Measured CSA of tibial, fibular, sciatic, and sural nerves at predetermined sites using ultrasound.
• Analyzed CSA data to establish reference ranges and assess diagnostic value in patient cohorts.

Main Results:

• Tibial nerve CSA ranged from 10.2 ± 1.9 to 20.7 ± 3.6 mm², and fibular nerve CSA ranged from 8.4 ± 1.8 to 9.5 ± 1.9 mm².
• 86% of CIDP patients showed upper limb nerve enlargement, while 67% had lower limb enlargement; 56% of CIDP patients with normal upper limb scans had lower limb enlargement.
• All CMT1A patients exhibited both upper and lower limb nerve enlargement; lower limb ultrasound offered no added diagnostic value for CMT1A but was supplementary for CIDP.

Conclusions:

• Established reference values for lower extremity peripheral nerve CSA in a healthy Chinese population.
• Lower limb nerve ultrasound is valuable for diagnosing CIDP, particularly when upper limb ultrasound findings are normal.
• Lower limb nerve ultrasound does not significantly add to the diagnosis of CMT1A when upper limb findings are considered.