The Investigation of Criterion Validity of the Modified Ashworth Scale Using the Alpha Motoneuron Excitability Indicators

The purpose of this study was to investigate the validity of the modified Ashworth Scale (MAS) by using both the conventional (Hmax/Mmax ratio) and the new indicators (Hslp/Mslp) of motoneuron excitability. This research was a correlational study on twenty post-stroke patients. Main outcome measures were the MAS and electrophysiologic assessments. The latter was performed using both conventional and new indicators of alpha motoneuron excitability. Data on 20 hemiplegic patients (seventeen men and three women) were analyzed. Correlation between the MAS and either soleus Hmax/Mmax or soleus Hslope/Mslope was not significant (P >0.05). In ten patients whose H-reflex could be evoked bilaterally, only new spinal excitability indicator 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 and the indicators of alpha motoneuron excitability. This research suggests that the MAS is not a valid measure for the assessment of spasticity in ankle plantar flexors. © 2006 Tehran University of Medical Sciences. All rights reserved. Acta Medica Iranica, 45(4): 290-294; 2007