The relation between Ashworth scale scores and the excitability of the α motor neurones in patients with post-stroke muscle spasticity

Abstract

Objectives: To compare the MAS with objective neurophysiological tests of spasticity.

Methods: The MAS was recorded in patients with post-stroke lower limb muscle spasticity and correlated with the excitability of the α motor neurones. The latter was evaluated by measuring the latency of the Hoffmann reflex (H reflex) and the ratio of the amplitude of the maximum H reflex (H_max) to that of the compound action motor potential of the soleus muscle (M_max).

Results: Data on 24 randomly recruited patients were analysed. Patients were divided into two groups according to their MAS score: 14 had a MAS score of 1 (group A) and 10 scored 2 (group B). The two groups were comparable with respect to age and sex, but in group A there was a longer period since the stroke. The H reflex latency was reduced and the H_max:M_max ratio was increased in both groups. The H_max:M_max ratio values were higher for group B but the differences were not statistically significant.

Conclusions: There is a relation between the MAS scores and α motor neurone excitability, although it is not linear. This suggests that the MAS measures muscle hypertonia rather than spasticity.

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