Differential Changed Excitability of Spinal Motor Neurons Innervating Tibialis Anterior and Peroneus Muscles Cause Foot Inversion After Stroke.

Gang Liu,Shan Tian,Yue Cao,Xue-Yan Shen,Yi Wu,Xin-Wei Tang,Rong-Rong Lu,Jun-Fa Wu,Ying Chen,Chin-Hsuan Chia

doi:10.3389/fneur.2020.544912

Gang Liu, Shan Tian + Show 8 more

Open Access

https://doi.org/10.3389/fneur.2020.544912

Copy DOI

Abstract

Objective: To study differential post-stroke changes of excitability of spinal motor neurons innervating a group of antagonist muscles of ankle and their effects on foot inversion.Methods: F waves in tibialis anterior (TA) and peroneus muscles (PN) were recorded. The condition of spasticity and foot inversion in stroke patients were also evaluated. The differences of F wave parameters between patients and healthy controls (HC), as well as TA and PN, were investigated.Results: There were natural differences in the persistence of the F waves (Fp) and F/M amplitude ratio (F/M) between TA and PN in HC. Stroke patients showed significantly higher F/M in TA and PN, while there was no difference in Fp comparing to HC. The natural differences in F wave parameters between TA and PN were differentially retained after stroke. The natural difference of the two muscles in Fp remained unchanged and the F/M difference disappeared in those without spasticity or foot inversion, while the Fp difference disappeared and the F/M difference remained in those with spasticity or foot inversion.Conclusion: Based on the natural difference of the number and size of spinal motor neurons innervating TA and PN, their excitability may change differently according to the severity of the stroke, which may be the reason of foot inversion.

Highlights

Motor dysfunction after stroke is the main cause of disability, and still a major challenge to neurological rehabilitation [1]
Both the F/M of the the healthy group (TA) and PN in the stroke patients were significantly higher than the healthy controls (TA patients: 0.0710 ± 0.0073, Z = −4.065, p < 0.0001; PN patients: 0.0369 ± 0.0037, Z = −2.135, p = 0.0474 < 0.05) (Figure 2B)
There was no difference between the stroke patients and the healthy controls’ Fp of the TA and PN (TA patients: 0.4030 ± 0.0456, Z = −0.422, p = 0.6425; PN patients: 0.5848 ± 0.0485, Z = −0.936, p = 0.3796) (Figure 2D)

Summary

Introduction

Motor dysfunction after stroke is the main cause of disability, and still a major challenge to neurological rehabilitation [1]. There is an obvious disparity in velocity and extent of recovery among different paralyzed muscles after stroke [2, 3]. Some muscles, such as the elbow flexor, are able to recover even in severe stroke; while other muscles, such as the peroneus, often show persistent weakness. The reason for this phenomenon remains elusive, deserving further researches on its pathophysiological mechanism. We hypothesized that the excitability of spinal motoneurons dominating different muscles will change differently after stroke

Methods

Results

Discussion

Conclusion