The cross-sectional area of the median nerve: An independent prognostic biomarker in amyotrophic lateral sclerosis

Abstract

IntroductionUltrasound changes in the cross-sectional area of the median nerve (CSAmn) could be of interest as biomarkers in patients with amyotrophic lateral sclerosis (ALS). MethodsEighty-four ALS patients (51 men [60.7%]; mean 62.0 [SD 11.46] years old) and forty-six controls (27 men [58.7%]; mean 59.9 [SD 8.08] years old) of two different cohorts were recruited between September 2013 and February 2018. The CSAmn was measured bilaterally in each cohort, by two different examiners with two different ultrasound machines (one in each cohort). Its association with clinical variables (disease duration, muscle strength, disability, progression rate and tracheostomy-free survival) was assessed. ResultsThe CSAmn was smaller in patients than in controls, and the study cohort did not influence its values. A mild correlation between the strength of the wrist flexor and the CSAmn was found. In the multivariable analysis, the probability of this association being true was 90%. In the cox regression, both a faster progression rate and a larger CSAmn independently predicted poor survival (HR=4.29, [Cr.I95%: 2.71–6.80], p<0.001; and HR=1.14, [Cr.I95%: 1.03–1.25], p=0.01), after adjusting by age, body mass index, bulbar onset, and diagnostic delay. ConclusionsThe CSAmn is an easy to assess biomarker that seems reliable and reproducible. Our data also suggest that it could act as a progression and prognostic biomarker in ALS patients. Longitudinal studies with repeated measures are warranted to confirm its usefulness in the clinical practice.