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Is there any relationship between the Modified Ashworth Scale scores and alpha motoneuron excitability indicators?
G. R. Olyaei, N, Ghotbi, M. R. Hadian, N. N. Ansari and H. Bagheri
Rehabilitation Faculty, Tehran University of Medical Sciences, Tehran, Iran

Background: The modified Ashworth scale (MAS) is the most widely used test for assessing muscle spasticity in research and clinical practice. Many researchers investigated its validity with different methods and questioned its accuracy in the recent years. The purpose of this study was to investigate the relationship between the modified Ashworth scale (MAS) scores and both conventional (Hmax/Mmax) and new (Hslope/Mslope) measures of motoneuron excitability.

Method: This research was a correlational study, which performed on 31 post-stroke patients. The main outcome measures were the MAS and electro physiologic assessments. The latter was performed using Hoffmann reflex.

Results: Data on 31 adult subjects with hemiplegia (25 men and six women) were analyzed. 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).

Conclusions: 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.