Scale Description

The Ashworth Scale (AS) is used to assess muscle spasticity, which is the increased resistance during passive movement of a joint. It is primarily applied to patients with neurological impairments such as stroke or multiple sclerosis. The original Ashworth Scale rates resistance on a scale from 0 (no resistance) to 4 (severe rigidity).
The Modified Ashworth Scale (MAS) includes an additional 1+ category to capture resistance through less than half of the range of motion. This modification was introduced to provide a more detailed assessment of spasticity.

Analysis and Use of Data

Category 0: No increase in muscle tone (normal range of motion).
Category 1: Slight increase in muscle tone, manifested by a catch and release or minimal resistance at the end of the range of motion.
Category 1+: Slight increase in muscle tone, manifested by a catch followed by minimal resistance through less than half of the range of motion.
Category 2: More marked increase in muscle tone through most of the range of motion, but the affected part(s) can be moved easily.
Category 3: Considerable increase in muscle tone, making passive movement difficult.
Category 4: Affected part(s) rigid in flexion or extension.
The scale is used to evaluate the severity of spasticity and is useful for monitoring patient progress in therapeutic programs or assessing the effectiveness of medications.

Purpose

The primary goal of the Ashworth Scale and the Modified Ashworth Scale is to quantitatively assess spasticity. The modification aimed to enhance the accuracy of spasticity measurement by providing more detailed information about the resistance encountered during movement.

Calibration

The Modified Ashworth Scale has undergone psychometric evaluation and is recognized for its diagnostic reliability. Key references for its calibration include:
Blackburn, M., van Vliet, P., et al. (2002). “Reliability of measurements obtained with the modified Ashworth scale in the lower extremities of people with stroke.” Physical Therapy, 82(1): 25.
Bohannon, R. and Smith, M. (1987). “Interrater reliability of a modified Ashworth scale of muscle spasticity.” Physical Therapy, 67(2): 206.
Gregson, J., Leathley, M., et al. (1999). “Reliability of the Tone Assessment Scale and the modified Ashworth scale as clinical tools for assessing poststroke spasticity.” Archives of Physical Medicine and Rehabilitation, 80(9): 1013-1016.
Gregson, J., Leathley, M., et al. (2000). “Reliability of measurement of muscle tone and muscle power in stroke patients.” Age and Ageing, 29(3): 223.

References

Blackburn, M., van Vliet, P., et al. (2002). “Reliability of measurements obtained with the modified Ashworth scale in the lower extremities of people with stroke.” Physical Therapy, 82(1): 25.
Bohannon, R. and Smith, M. (1987). “Interrater reliability of a modified Ashworth scale of muscle spasticity.” Physical Therapy, 67(2): 206.
Brashear, A., Zafonte, R., et al. (2002). “Inter-and intrarater reliability of the Ashworth Scale and the Disability Assessment Scale in patients with upper-limb poststroke spasticity.” Archives of Physical Medicine and Rehabilitation, 83(10): 1349-1354.
Gregson, J., Leathley, M., et al. (1999). “Reliability of the Tone Assessment Scale and the modified Ashworth scale as clinical tools for assessing poststroke spasticity.” Archives of Physical Medicine and Rehabilitation, 80(9): 1013-1016. PubMed
Gregson, J., Leathley, M., et al. (2000). “Reliability of measurement of muscle tone and muscle power in stroke patients.” Age and Ageing, 29(3): 223.
Haas, B., Bergström, E., et al. (1996). “The inter-rater reliability of the original and of the modified Ashworth scale for the assessment of spasticity in patients with spinal cord injury.” Spinal Cord, 34(9): 560-564.