Compound muscle action potentials in the median/accessory nerves reflect disease severity in amyotrophic lateral sclerosis

The objective of this study is to assess the severity of amyotrophic lateral sclerosis (ALS) patients by comparing relevant nerve conduction study (NCS) indices between the accessory and limb nerves, with the aim of identifying distinctive electrophysiological markers that precede symptoms, to facilitate the early diagnosis of ALS and guide subsequent follow-up measures. A total of 54 patients with ALS were enrolled at Renmin Hospital of Wuhan University from 2018 to 2020. Patients were consecutively recruited, and their sex, age, time of referral, presenting symptoms, site of onset, modified ALS functional rating scale-revised (ALSFRS-R) score, and electrophysiological findings were retrospectively recorded and analyzed. A total of 54 patients with ALS were included, with a male-to-female ratio of 2.38. The ALSFRS-R scores of the 54 ALS patients ranged from 27 to 46, with mean (± standard deviation [SD]) of 39.26 ​± ​4.63, with no significant gender difference in scores ( t ​= ​0.438, P ​= ​0.663). In regards to electrophysiological indices, there were 19, 14, 2, 8, and 18 patients with distal motor latency (DML) prolongation and 36, 29, 7, 16, and 6 patients with decreased compound muscle action potential (CMAP) amplitudes of the median, ulnar, tibial, peroneal, and accessory nerves, respectively. Correlation and regression analysis revealed that ALSFRS-R score was negatively correlated with age ( r ​= ​−0.337, P ​= ​0.013) and DML of median nerve ( r ​= ​−0.340, P ​= ​0.012), and positively correlated with the CMAP amplitudes of median ( r ​= ​0.549, P ​<0.001), ulnar ( r ​= ​0.438, P ​= ​0.001), tibial ( r ​= ​0.428, P ​= ​0.001), peroneal ( r ​= ​0.426, P ​= ​0.001), and accessory ( r ​= ​0.326, P ​= ​0.016) nerves. The independent influencing factors of the ALSFRS-R score were the CMAP amplitudes of the median nerve ( B ​= ​1.023, P ​= ​0.002) and the accessory nerve ( B ​= ​0.460, P ​= ​0.0497). CMAP amplitudes in the median and accessory nerves are closely related to the ALSFRS-R score, which can be used as a crucial observational index to objectively reflect the severity of ALS.