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W Vattanasilp

Publications and source records attributed to W Vattanasilp.

2 recordsLinked to original sources
PubMed2000

Contribution of thixotropy, spasticity, and contracture to ankle stiffness after stroke.

OBJECTIVES: Increased resistance to stretch of muscles after stroke may be the result of centrally mediated neural factors such as spasticity or local, peripheral factors such as muscle contracture or thixotropy. The aim was to investigate evidence for an abnormal thixotropic response and compare this with two other factors-contracture and spasticity-which could potentially contribute to muscle stiffness after stroke. METHODS: Thirty patients with stroke whose calf muscles were assessed clinically as stiff and 10 neurologically normal subjects were recruited. To measure thixotropy, their calf muscles were stretched through two cycles after two prestretch conditions: one in which the muscles were maintained in a shortened position and one in which they were maintained in a lengthened position. Spasticity was defined as the presence of tonic stretch reflexes in relaxed muscles. Contracture was defined as being present when maximum passive ankle dorsiflexion fell at least 2 SD below the mean value of the control subjects. RESULTS: Both controls and patients with stroke exhibited a thixotropic response but this was no greater in the patients than the controls. About one third of the patients displayed muscle contracture and most exhibited spasticity. Contracture made a significant contribution (p=0.006) to the clinical measure of calf muscle stiffness while spasticity made a significant contribution (p=0.004) to the laboratory measure of calf muscle stiffness. CONCLUSIONS: Measuring thixotropy at the level of joint movement was sufficiently sensitive to determine the thixotropic response in both neurologically normal subjects and patients impaired after stroke. The thixotropic response was not higher than normal after stroke, suggesting that whereas thixotropy may produce enough immediate resistance to impede movement in those who are very weak, it is not a substantial contributor to long term muscle stiffness. Contracture did significantly contribute to muscle stiffness, supporting the importance of prevention of contracture after stroke. Spasticity contributed to muscle stiffness only when the limb was moved quickly.

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PubMed1998

Does spasticity contribute to walking dysfunction after stroke?

OBJECTIVES: Clinically, it is assumed that spasticity of the calf muscles interferes with walking after stroke. The aim was to examine this assumption by evaluating the contribution of spasticity in the gastrocnemius muscle to walking dysfunction in an ambulant stroke population several months after stroke. METHODS: Fourteen stroke patients who were able to walk independently and 15 neurologically normal control subjects were recruited. Both resting and action stretch reflexes of the gastrocnemius muscle were investigated under conditions that simulated walking. Resting tonic stretch reflexes were measured to assess spasticity whereas action tonic stretch reflexes were measured to assess the possible contribution of spasticity to gait dysfunction. RESULTS: Two thirds of the stroke patients exhibited resting tonic stretch reflexes which indicate spasticity, whereas none of the control subjects did. However, the stroke patients exhibited action tonic stretch reflexes that were of similar magnitude to the control subjects, suggesting that their reflex activity during walking was not different from that of control subjects. Furthermore, there was no evidence that the action stretch reflex in the stroke patients contributed a higher resistance to stretch than the control subjects. CONCLUSIONS: Whereas most of the stroke patients exhibited spasticity when measured both clinically and physiologically, they did not exhibit an increase in resistance to dorsiflexion due to exaggerated action tonic stretch reflexes. It is concluded that it is unlikely that spasticity causes problems in walking after stroke in ambulant patients. Therefore, it seems inappropriate to routinely reduce or inhibit the reflex response to improve functional movement in stroke rehabilitation. Factors other than spasticity should be considered when analysing walking after stroke, so that appropriate treatment is provided to patients.

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