Is there any relationship between the Modified Ashworth Scale scores and alpha motoneuron excitability indicators?

The purpose of this study was to investigate the relationship between the modified Ashworth scale (MAS) scores and alpha motoneuron excitability indicators. Thirty-one post-stroke patients were assessed for this object. The main outcome measures were the MAS and electro physiologic assessments. The latter was performed using both conventional (Hmax/Mmax) and new (Hslope/Mslope) measures of spinal excitability. Data on thirty-one adult subjects with hemiplegia (twenty-five men and six women) were analysed. The soleus Hmax/Mmax ratio appeared to correlate directly with the MAS scores (r = 0.36; P < 0.05). Correlation between the MAS scores and either Hslope/Mslope ratio or H-reflex latency was not significant (P > 0.05). In seventeen patients whose H-reflex could be evoked bilaterally, spinal excitability indicators showed significant difference between the affected and non-affected sides (P < 0.05). Based on the results of this study, there is no relationship between the MAS scores and the preferred measure of alpha motoneuron excitability. This research suggests that the MAS could not distinguish between the reflexive and non-reflexive components of the hypertonicity in ankle plantar flexors.