Objectives: To determine the validity of the Modified Ashworth Scale as a measure of spasticity by determining its relationship to surface electromyography activity and contracture.
Design: A controlled study of hemiparetic stroke patients with spasticity.
Setting: A physiotherapy department in a secondary care hospital.
Subjects: Thirty-one stroke patients and 20 healthy volunteers.
Main measures: The resistance to passive movement around the knee and ankle of the affected and unaffected legs was rated using the Modified Ashworth Scale. Passive range of movement was measured with a goniometer. Surface electromyography recordings of four lower limb muscles were taken during passive stretches of the knee and ankle.
Results: Hemiparetic patients produced surface electromyography responses to stretch that were of greater amplitude (unaffected limbs: mean = 25.82 mV (43.85), affected limbs: mean = 24.77 mV (35.46)) than those of healthy volunteers (mean = 15.85 (29.96)). The affected muscles of hemiparetic patients were more likely to produce surface electromyography responses to stretch of a sustained duration (45% of cases) compared with unaffected limbs (24% of cases) and those of healthy volunteers (16% of cases). The Modified Ashworth Scale showed a positive correlation with the magnitude (p < 0.05) and duration (p < 0.001) of the surface electromyography response. High scores on the Modified Ashworth Scale were associated with contracture (p < 0.001). Contracted muscles produced significantly greater surface electromyography reflex responses compared with noncontracted muscles (p < 0.05).
Conclusion: The Modified Ashworth Scale reflects spasticity in terms of surface electromyography stretch responses produced by passive movement, but the relationship of spasticity to contracture remains unclear.
Get full access to this article
View all access options for this article.
References
1.
1 Ashworth B. Preliminary trial of carisoprodal in multiple sclerosis. Practitioner1964; 192: 540-542.
2.
2 Bohannon RW, Smith MB. Interrater reliability of a modified Ashworth scale of muscle spasticity.Phys Ther1987; 67: 206-207.
3.
3 Pandyan AD, Johnson GR, Price CI et al. A review of the properties and limitations of the Ashworth and modified Ashworth Scales as measures of spasticity. Clin Rehabil1999; 13: 373-383.
4.
4 Bakheit AM, Maynard VA, Curnow J et al. The relation between Ashworth scale scores and the excitability of the alpha motor neurones in patients with post-stroke muscle spasticity. J Neurol Neurosurg Psychiatry2003; 74: 646-648.
5.
5 Lance JW. Symposium synopsis. In: Feldman RG, Young RR, Koella WP eds. Spasticity: disordered motor control. Chicago: Year Book Medical Publishers, 1980.
6.
6 Dietz V, Quintern J, Berger W. Electrophysiological studies of gait in spasticity and rigidity. Evidence that altered mechanical properties of muscle contribute to hypertonia. Brain1981; 104: 431-449.
7.
7 Berger W, Horstmann G, Dietz V. Tension development and muscle activation in the leg during gait in spastic hemiparesis: Independence of muscle hypertonia and exaggerated stretch reflexes. J Neurol Neurosurg Psychiatry1984; 47: 1029-1033.
8.
8 Hufschmidt A, Mauritz KH. Chronic transformation of muscle in spasticity: a peripheral contribution to increased tone. J Neurol Neurosurg Psychiatry1985; 48: 676-685.
9.
9 Ibrahim IK, Berger W, Trippel M et al. Stretchinduced electromyographic activity and torque in spastic elbow muscles. Brain1993; 116: 971-989.
10.
10 Malouin F, Bonneau C, Pichard L et al. Non-reflex mediated changes in plantarflexor muscles early after stroke. Scand J Rehabil Med1997; 29: 147-153.
11.
11 Skold C, Harms-Ringdahl K, Hultling C et al. Simultaneous Ashworth measurements and electromyographic recordings in tetraplegic patients. Arch Phys Med Rehabil1998; 79: 959-965.
12.
12 O'Dwyer NJ, Ada L, Neilson PD. Spasticity and muscle contracture following stroke. Brain1996; 119(Pt 5): 1737-1749.
13.
13 O'Dwyer NJ, Ada L. Reflex hyperexcitability and muscle contracture in relation to spastic hypertonia. Curr Opin Neurol1996; 9: 451-455.
14.
14 SENIAM, European Recommendations for Surface Electromyography: Roessingh Research and Development, 1999.
15.
15 Basmajian J, Blumenstein R. Electrode placement in EMG biofeedback. Baltimore: Williams and Wilkins. 1980.
16.
16 Thilmann AF, Fellows SJ, Garms E. The mechanism of spastic muscle hypertonus. Variation in reflex gain over the time course of spasticity. Brain1991; 114(Pt 1A): 233-244.
17.
17 Sheean G. Neurophysiology of spasticity. In: Barnes MP, Johnson GR eds. Upper motor neurone syndrome and spasticity. Cambridge: Cambridge University Press, 2001: 12-78.
