Relationship between spasticity and spinal neural circuits in patients with chronic hemiparetic stroke

Abstract

Spasticity is a common problem in patients with stroke that contributes to motor dysfunction. However, the pathophysiological mechanisms underlying spasticity are not fully understood. The purpose of the present study was to explain the relationship between features of spinal neural circuits assessed using electrophysiological techniques and the clinical manifestations of stroke. The participants were 71 patients with chronic hemiparetic stroke. To assess spinal neural circuits, Hmax/Mmax of the forearm flexor muscles and reciprocal inhibition (RI) between forearm extensor and flexor muscles with the H reflex conditioning-test paradigm were measured. The relationships between electrophysiological parameters and clinical variables (age, time from stroke onset, upper extremity functional scores, and spasticity) were then analyzed. It was found that the third phase of RI (RI-3) correlated with the modified Ashworth scores of the wrist and finger flexors. No other correlations were found between electrophysiological and clinical measures. These results suggest that RI-3 is associated with spasticity and may be helpful to understand the basis of post-stroke spasticity.

Cerebellar Intermittent Theta-Burst Stimulation Reduces Upper Limb Spasticity After Subacute Stroke: A Randomized Controlled Trial

“…The H-reflex is commonly used to quantify the level of spinal alpha motor neuron excitability (Pizzi et al, 2005). The H max /M max ratio is proposed as a measure of the percentage of motoneurons activated by eliciting the monosynaptic H-reflex compared with those directly activated (Okuyama et al, 2018), which presents high reliability and good sensitivity in detecting changes in spasticity (Levin and Hui-Chan, 1993). In this study, no significant improvements in the H max /M max ratio were found between groups.…”

Effect of the combination of motor imagery and electrical stimulation on upper extremity motor function in patients with chronic stroke: preliminary results

“…A previous report showed that RI at 100 ms was correlated with the MAS scores of the wrist and finger flexors. 38 Moreover, a change in RI at 100 ms and a change in the MAS scores of the wrist were also correlated after an intervention using integrated volitional control electrical stimulation with a wrist splint. 6 We cannot consider the relationship of clinical change and neurophysiological change because of small sample in this study.…”

“…However, the third inhibitory phase may be responsible for descending control of spinal interneurons possibly by the brain stem or cerebral cortex. 34 , 36 , 38 The size of the conditioned H reflex was expressed as a percentage of the size of the unconditioned H reflex at each interval (e.g. RI 0 ms = conditioned H reflex amplitude of the ISI at 0 ms/test H reflex amplitude).…”

Change in Reciprocal Inhibition of the Forearm with Motor Imagery among Patients with Chronic Stroke

“…Stimulus intensity of the conditioning stimulation was 1.0 motor threshold, which was defined as a 100 μ V response of the ECR muscle. The conditioning test interstimulus interval (ISI) was set at two intervals of 0 and 20 ms based on previous reports [ 41 – 46 ]. The first phase, that is, ISI of 0 ms, is related to the Ia disynaptic pathway [ 23 ].…”