A recent meta-analysis provided pooled reference values of the cross-sectional area (CSA) of lower extremity nerves that could help standardize peripheral nerve ultrasound protocols. Findings from this study were published in the European Journal of Neurology.

The ultrasound-guided measurement of the CSA of peripheral nerves can evaluate focal lesions and diagnose entrapment syndromes and inflammatory polyneuropathies. Study investigators sought to perform a systematic review on published CSA reference values for lower extremity nerves.

Their meta-analysis included 16 studies with a total of 1001 healthy volunteers (mean age, 47.9 years) comprising 4023 examined nerve sites. These studies measured CSA for the fibular nerve at the fibular head and popliteal fossa, tibial nerve at the popliteal fossa and malleolus, and sural nerve at the level of the two heads of gastrocnemius muscle. The study investigators performed regression and correlation analysis adjusted for sex distribution, age, height, weight, and geographic location.


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The calculated mean pooled CSA of the fibular nerve at the fibular head was 8.4 mm2 [95% CI, 6.8-9.9mm2) and 7.9 mm2 (95% CI, 6.6-9.2 mm2) at the popliteal fossa. Additionally, the calculated mean pooled CSA of the tibial nerve at the popliteal fossa was 25.9mm2 (95% CI, 17.5-34.4 mm2) and 10.0 mm2 (95% CI, 7.7-12.4 mm2) at the malleolus. The study investigators also calculated a mean pooled CSA of 2.4 mm2 (95% CI, 1.7-3.1 mm2) at sural nerve at the level of the gastrocnemius muscle.

There was substantial heterogeneity across studies that reported average CSA values of the tibial nerve at the popliteal fossa (I2=84.48%). In subgroup analyses, the study investigators found a reduced CSA of the tibial nerve at the popliteal fossa and sural nerve in European, Asian, and African studies compared with studies conducted in America and New Zealand (P =.00). The CSA of sural nerve was also higher in New Zealand studies compared with studies conducted in Europe (P =.02).

Limitations of this meta-analysis included the substantial heterogeneity between the studies as well as the lack of assessment regarding the detected associations at the individual patient level vs the population level.

The study investigators concluded that their data may “facilitate the goal of an international standardized evaluation protocol.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Fisse AL, Katsanos AH, Gold R, Krogias C, Pitarokoili K. Cross-sectional area reference values for peripheral nerve ultrasound in adults: a systematic review and meta-analysis – part II: Lower extremity nerves. Eur J Neurol. Published online April 1, 2021. doi:10.1111/ene.14850