Evaluation of post-stroke spasticity from the subacute to chronic stages: A clinical and neurophysiologic study of motoneuron pool excitability

Abstract

Spasticity measured using clinical scales, such as the modified Ashworth scale (MAS), may not sufficiently evaluate the effectiveness of therapeutic interventions and predict prognosis. This study aimed to compare changes in H-reflex excitability in the spastic and unimpaired upper and lower limbs of patients with acute and chronic stroke. We also investigated the relationship between the degree of spasticity as assessed by the MAS and motor neuron pool excitability with by analyzing H-reflex excitability. Sixty adult patients with a first-ever stroke were recruited for this study. MAS scores were recorded in the post-stroke upper and lower limb muscles. H-reflexes and M-responses of the bilateral flexor carpi radialis and soleus were tested by stimulating the median and tibial nerves. The results showed that both the ratio of the maximal size of the H-reflex (Hmax) to the maximal size of the M-response (Mmax) and the ratio of the developmental slope of H-reflex (Hslp) to that of the M-responses (Mslp) were significantly higher on the spastic side than on the unimpaired side for the upper and lower limbs. In contrast, the ratio of the threshold of the H-reflex (Hth) to the threshold of the M-response (Mth) only showed significant differences between the two sides in the upper limbs. The Hslp/Mslp paretic/non-paretic ratio was increased in patients with MAS scores of 2 or 3 compared to MAS scores of 1 for both the upper and lower limbs, whereas the Hmax/Mmax paretic/non-paretic ratio showed significant differences between MAS scores of 2 or 3 and 1 only in the upper limbs. Moreover, in either the spastic or unimpaired sides, there were no significant differences in any of the three motoneuron pool excitability parameters, Hmax/Mmax, Hslp/Mslp, and Hth/Mth, between the shorter chronicity (time post-stroke ≤6 months) and longer chronicity groups (time post-stroke >6 months) for both the upper and lower limbs. These results suggest that Hslp/Mslp could be a potential neurophysiological indicator for evaluating the degree of spasticity in both the upper and lower limbs of patients with hemiplegia. The MAS and Hslp/Mslp characterize clinical and neurophysiologic spasticity, respectively, and could be used as an integrated approach to evaluate and follow up post-stroke spasticity.

Keywords

• h-reflex
• modified ashworth scale
• m-wave
• spasticity
• stroke