Quantification of a single score (1+) in the Modified Ashworth Scale (MAS), a clinical assessment of spasticity

The Modified Ashworth Scale (MAS) is an assessment that is often used by clinicians to grade spasticity in the affected limbs of stroke survivors. The MAS is a function of the angle at which the clinician perceives a resistance to stretch and/or a `catch' during a passive joint rotation. The qualitative nature of the assessment in combination with the low resolution of the scale could result in varied grouping of spastic patients, even for a single score. The objective of this pilot study was to develop a method for the quantification of the MAS, which could provide greater resolution and could eventually guide better informed therapeutic interventions. The MAS assessment at the elbow joint for four stroke survivors with the same clinical MAS score of 1+ was performed by a clinician and quantified using signals from surface electromyography (EMG) and an electrogoniometer. The subjects were tested on both the affected and contralateral upper limbs. The findings from this study show a varied set of signal outputs across four stroke survivors, all graded at 1+. The quantification provides insight as to the mechanisms underlying the passive resistance.