The relation between Ashworth scale scores and the excitability of the alpha motor neurones in patients with post-stroke muscle spasticity.
BACKGROUND
The modified Ashworth scale (MAS) is the most widely used method for assessing muscle spasticity in clinical practice and research. However, the validity of this scale has been challenged.


OBJECTIVE
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 alpha 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 alpha motor neurone excitability, although it is not linear. This suggests that the MAS measures muscle hypertonia rather than spasticity.
Bakheit
A M O
AM
Peninsula Medical School and Plymouth Primary Care Trust, Plymouth, UK. magid.bakheit@pcs-tr.swest.nhs.uk
Maynard
V A
VA
Curnow
J
J
Hudson
N
N
Kodapala
S
S
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009128:Muscle Spasticity / Q000209:etiology* / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D020521:Stroke / Q000150:complications* / Q000503:physiopathology*