Rate-dependent depression is impaired in amyotrophic lateral sclerosis.

Abstract

We investigated rate-dependent depression (RDD) of the Hoffman reflex (H-reflex) in patients with amyotrophic lateral sclerosis (ALS), a degenerative disease with ventral horn involvement. In this case-control study, we enrolled 27 patients with ALS and 30 matched healthy control subjects. Clinical and electrophysiological assessments, as well as RDD in response to various stimulation frequencies (0.5Hz, 1Hz, 3Hz and 5Hz), were compared between groups. Multiple clinical and electrophysiological factors were also explored to determine any underlying associations with RDD. The ALS group showed a significant loss of RDD across all frequencies compared to the control group, most notably following 1Hz stimulation (19.1 ± 20.3 vs. 34.0 ± 13.7%, p = 0.003). Among factors that might influence RDD, the enlargement of the motor unit potential (MUP) showed a significant relationship with RDD following multifactor analysis of variance (p = 0.007) and Pearson correlation analysis (ρ = - 0.70, p < 0.001), while various upper motor neuron manifestations were not correlated with RDD values (p > 0.05). We report a loss of RDD in patients with ALS. The strong correlation detected between the RDD deficit and increased MUP suggests that RDD is a sensitive indicator of underlying spinal disinhibition in ALS. ChiCTR2000038848, 10/7/2020 (retrospectively registered), http://www.chictr.org.cn/ .