Comparison between upper limb onset classic amyotrophic lateral sclerosis and flail-arm syndrome / 西安交通大学学报(医学版)

ABSTRACT

Objective: To investigate the clinical and electrophysiological characteristics of upper limb onset classic amyotrophic lateral sclerosis (ALS) and ALS variant flail-arm syndrome (FAS) so as to provide reference for differential diagnosis and prognosis. Methods: We recruited 120 upper limb onset classic ALS and 18 FAS patients from Neurology Department of The First Affiliated Hospital of Xi'an Jiaotong University between January 2013 and December 2018. The clinical and electrophysiological characteristics and survival were compared between the two groups. Results: Compared with those in upper limb onset classic ALS, FAS patients' diagnostic level was lower (P<0.001), diagnostic delay time was longer (15 mon vs. 11 mon; Z=-2.749, P=0.005), progression rate was slower (0.33 vs. 0.64; Z=-3.055, P=0.002), and time from the first region to the second was longer (33 mon vs. 8 mon; Z=-4.852, P<0.001). FAS patients were as likely to have single lateral upper limb onset as those with upper limb onset classic ALS, but the proportion of patients with bilateral upper limbs onset in FAS group was higher than that in the upper limb onset classic ALS group (33.3% vs. 8.3%; χ2=7.261, P=0.007), the proportion of proximal upper limb being more severely affected was higher in FAS group (55.6% vs. 18.3%; χ2=8.856, P=0.003). The proportion of FAS patients with high upper limb reflex or pathologic sign was lower (11.1% vs. 72.5%; χ2=25.759, P<0.001). Compared with upper limb onset classic ALS, FAS group's ratio of compound muscle action potential (CMAP)abductor pollicis brevis/CMAPabductor digiti minimi was higher, but without statistical significance; needle electrode electromyographic results were similar between the two groups. Survival time of FAS patients was longer than that of patients with upper limb onset classic ALS (53 mon vs. 22 mon; Z=-4.421, P<0.001), and FAS diagnosis itself was an independent prognostic factor of lower death risk compared with the diagnosis of upper limb onset classic ALS (HR=0.174, 95% CI 0.061-0.496, P=0.001). Conclusion: Although natural histories of FAS and upper limb onset classic ALS are different, their EMG performance is similar. Characteristics including bilateral arms onset, proximal symptoms being severer than distal ones, lower motor neuron findings being more prominent have some implications for diagnosis of FAS.