A review of the properties and limitations of the Ashworth and modified Ashworth Scales as measures of spasticity

Abstract

Background: The Ashworth Scale and the modified Ashworth Scale are the primary clinical measures of spasticity. A prerequisite for using any scale is a knowledge of its characteristics and limitations, as these will play a part in analysing and interpreting the data. Despite the current emphasis on treating spasticity, clinicians rarely measure it. Objectives: To determine the validity and the reliability of the Ashworth and modified Ashworth Scales. Study design: A theoretical analysis following a structured literature review (key words: Ashworth; Spasticity; Measurement) of 40 papers selected from the BIDS-EMBASE, First Search and Medline databases. Conclusions: The application of both scales would suggest that confusion exists on their characteristics and limitations as measures of spasticity. Resistance to passive movement is a complex measure that will be influenced by many factors, only one of which could be spasticity. The Ashworth Scale (AS) can be used as an ordinal level measure of resistance to passive movement, but not spasticity. The modified Ashworth Scale (MAS) will need to be treated as a nominal level measure of resistance to passive movement until the ambiguity between the ‘1’ and ‘1+’ grades is resolved. The reliability of the scales is better in the upper limb. The AS may be more reliable than the MAS. There is a need to standardize methods to apply these scales in clinical practice and research.