Modified Ashworth Scale
Original Editor - Habibu Salisu Badamasi
Top Contributors - Habibu Salisu Badamasi, Kim Jackson and Shreya Pavaskar
Objective
The Modified Ashworth Scale (MAS) is used to assess spasticity.[1]
Intended Population
The Modified Ashworth Scale (MAS) has been utilised in the following populations: stroke, spinal cord injury, multiple sclerosis, cerebral palsy, traumatic brain injury, paediatric hypertonia and central nervous system lesions[2]
Method of Use
The test is performed by extending the patients limb's first from a position of maximal possible flexion to maximal possible extension (the point at which the first soft resistance is met). Afterwards, the modified Ashworth scale is assessed while moving from extension to flexion[3]
| 0 | No Increased in tone |
|---|---|
| 1 | Slight increase in tone giving a catch when the limb is moved in flexion or extension |
| 1+ | Slight increase in muscle tone, indicated by a catch followed by minimal resistance throughout range of motion (ROM) |
| 2 | More marked increase in tone through most of the ROM, but the limb easily flexed |
| 3 | Considerable increase in tone, passive movement difficult |
| 4 | Limb rigid in flexion or extension |
Evidence
Below are some studies that have investigated the reliability of the modified Ashworth Scale as a measure of spasticity[4]
| Reference | Study details | Relevant results |
|---|---|---|
| Bohannon and Smith (1987)13 | Inter-rater reliability of the MAS. Muscles tested: elbow flexors in the impaired arm. Ns = 30 [MS (1), HI (5), CVA (24) ] Na = 2 [physiotherapist] The assessors independently assessed each subject once | 86.7% agreement between assessors (Kendall’s τ = 0.847; p <0.001) Cohen’s κ was calculated as 0.826a |
| Bodin and Morris (1991)48 | Inter-rater reliability of the MAS. Muscle tested: wrist flexors. Ns = 18 [CVA] Na = 2 [physiotherapist] The assessors independently assessed each subject under three different conditions (immediately after positioning, after a 90 s stretch of the flexors and after a 90 s stretch of the extensors). | 76% agreement between assessors (Kendall’s τ of 0.857) Cohen’s κ was calculated as 0.745a |
| Sloan et al. (1992)49 | Inter-rater reliability of the MAS. Muscles tested: elbow flexors and extensors, and knee flexors. Measurements taken bilaterally. Ns = 34 [hemiplegia] Na = 4 [physiotherapist (2), doctor (2) ] The assessors serially assessed each subject | Spearman’s ρ varied from 0.56 and 0.90 at the elbow and between 0.26 and 0.62 at the knee |
| Allison et al. (1996)50 | Inter- and Intra-rater reliability of the MAS. Muscles tested: ankle plantar flexors. Measurements were taken bilaterally. Day-1 of testing Ns = 30 [HI] Na = 2 [physiotherapist] Both testers assessed all subjects independently. Day-2 of testing Tester 1 assessed Ns = 21 subjects. | Day-1 Inter-rater reliability tester 1 and tester 2: 55% agreement (ρ = 0.727; τ = 0.647; κ = 0.397) Intra-rater reliability of tester 1: 53% agreement (ρ = 0.741; τ = 0.674; κ = 0.694) Intra-rater reliability of tester 2: 48% agreement (ρ = 0.550; τ = 0.478; κ = 0.286) Day-2 Intra-rater reliability of tester 1: 58% agreement (ρ = 0.821; τ = 0.739; κ 0.422) |
Reliability
The reliability of the Modified Ashworth Scale has been extensively studied to ensure its accuracy and consistency when used by different assessors and across multiple testing occasions. Below are some key studies that have investigated both inter-rater and intra-rater reliability of the MAS.
Interrater/Intrarater Reliability
Interrater reliability refers to the degree of agreement among different assessors, while intrarater reliability measures the consistency of assessments conducted by the same assessor over time. These reliability metrics are crucial for validating the use of the Modified Ashworth Scale in clinical and research settings.
In daily practice the use of the Modified Ashworth Scale procedure is quick and easy and is a common tool in the measurement of spasticity. Additionally, the Modified Ashworth Scale is widely used in research. In different patient groups such as stroke, multiple sclerosis and spinal cord injury, moderate to good intra-rater reliability and poor to moderate inter-rater reliability of the scale was found.[5]
Muscles tested; Elbow flexor and extensor and knee flexor in hemiplegia patients
- 49 Measurements taken bilaterally. Ns = 34 [hemiplegia] Na = 4 [physiotherapist (2), doctor (2) ] The assessors serially assessed each subject)[6]
- Spearman’s ρ varied from 0.56 and 0.90 at the elbow and between 0.26 and 0.62 at the knee
Validity
Validity refers to the extent to which the Modified Ashworth Scale measures what it is intended to measure, in this case, spasticity. Validity can be assessed through various methods, including criterion validity, construct validity, and content validity. The following sections provide evidence for the validity of the MAS:
Criterion Validity
Criterion validity examines the correlation between the MAS scores and other established measures of spasticity, such as EMG parameters. Some studies have shown good correlations between the modified Ashworth scores and EMG parameters derived from simultaneous surface EMG recordings from the muscles tested.[7]
However, it is not possible to draw unequivocal support for the modified Ashworth score being a valid and ordinal measure of spasticity due to one key methodological inconsistency. The actual time to grade spasticity (by passively moving the limb) was reported to be between 0.25 and 0.33 s, however, many of the derived EMG parameters were poorly referenced to this time window[4]
Construct Validity
Construct validity assesses whether the MAS accurately measures the concept of spasticity by comparing it with other measures that theoretically should relate to it.
Some studies modified the original scale by adding an additional category, a 1+ falling between 1 and 2, with the aim of increasing its sensitivity. Both scales have since been used as measures of spasticity for clinical and research purposes. A clinical rating of spasticity on the Ashworth Scales is made after an assessor tests the resistance to passive movement about a joint.Both scales describe the resistance perceived while moving a joint through its full range of movement – except in grade ‘4'.[8]
Content Validity
Content validity evaluates whether the MAS includes all the components necessary to measure spasticity.
The Ashworth Scale was initially developed as a simple clinical tool to test the efficacy of an anti-spastic drug in patients with multiple sclerosis. Over time, the scale has been adapted and validated for use in various clinical populations to measure spasticity.
Links
References
- ↑ Charalambous CP. Interrater reliability of a modified Ashworth scale of muscle spasticity. InClassic papers in orthopaedics 2014 (pp. 415-417). Springer, London.
- ↑ Morris S. Ashworth and Tardieu Scales: Their clinical relevance for measuring spasticity in adult and paediatric neurological populations. Physical Therapy Reviews. 2002 Mar 1;7(1):53-62.
- ↑ Rw B, Smith MB. Interrater reliability of a modified Ashworth scale of muscle spasticity. Phys ther. 1987;67(2):206-7.
- ↑ 4.0 4.1 Ad P, Johnson GR. Price CiM, Curless RH, Barnes MP, Rodgers H. A review of the properties and limitations of the Ashworth and modified Ashworth Scales as measures of spasticity. Clin Rehabil. 1999;13(5):373-83.
- ↑ Mehrholz J, Wagner K, Meißner D, Grundmann K, Zange C, Koch R, Pohl M. Reliability of the Modified Tardieu Scale and the Modified Ashworth Scale in adult patients with severe brain injury: a comparison study. Clinical rehabilitation. 2005 Nov;19(7):751-9.
- ↑ Pandyan AD, Johnson GR, Price CI, Curless RH, Barnes MP, Rodgers H. A review of the properties and limitations of the Ashworth and modified Ashworth Scales as measures of spasticity. Clinical rehabilitation. 1999 Oct;13(5):373-83.
- ↑ Ansari NN, Naghdi S, Younesian P, Shayeghan M. Inter-and intrarater reliability of the Modified Modified Ashworth Scale in patients with knee extensor poststroke spasticity. Physiotherapy theory and practice. 2008 Jan 1;24(3):205-13.
- ↑ Bohannon RW, Smith MB. Assessment of strength deficits in eight paretic upper extremity muscle groups of stroke patients with hemiplegia. Physical therapy. 1987 Apr 1;67(4):522-5.
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