Association of spasticity and motor dysfunction in chronic stroke.

BACKGROUND: The prevalence of increased muscle tone after stroke is frequently reported as 30% to 40%, and the condition is often concurrent with motor control deficits, manifesting as an inability to isolate paretic-limb joint movements.

OBJECTIVE: The objectives of this retrospective analysis were to 1) report the prevalence of increased muscle tone in a convenience sample of 128 chronic stroke survivors with moderate/severe motor deficits and 2) quantify the relation between tone and motor impairment in chronic stroke survivors.

METHODS: Analyses included descriptive statistics and multiple regression modeling, with the modified Ashworth Scale score (MAS; tone) as a predictor of isolated joint movement control (Fugl-Meyer score [FM]; motor impairment).

RESULTS: Increased muscle tone was present in 97% of subjects. Increased muscle tone was associated with impaired motor control (FM; upper extremity, P=0.008; lower extremity, P=0.03) after adjusting for age, time since stroke and sex. We found a significant difference between flexor and extensor strength for finger, elbow, hip and knee joints (P<0.002). Participants were classified in high and low MAS score groups. With high MAS score and for muscles of finger flexion and forearm pronation, we found a trend toward impaired strength of antagonist muscles (finger extensors and forearm supinators, respectively) as compared with low MAS score for these same muscle pairings.

CONCLUSIONS: The prevalence of increased tone was higher in this study than in previous reports. Increased muscle tone in chronic stroke survivors with persistent motor dysfunction could be associated with impaired motor control and differential muscle strength of antagonistic muscles.