The modified Ashworth scale is the most universally accepted clinical tool used to measure the increase of muscle tone. Spasticity was defined by Jim Lance in 1980, as a velocity-dependent increase in muscle stretch reflexes associated with increased muscle tone as a component of upper motor neuron syndrome. Spasticity has a wide range of etiologies, including brain injury, stroke, cerebral palsy, multiple sclerosis, trauma, and spinal cord injury. In a study looking at the prevalence of spasticity in stroke populations, 42.6% of stroke patients developed spasticity, and severe spasticity occurred in 15.6% of patients. Another study looking at the prevalence of spasticity in cerebral palsy found spastic subtypes in 90% of the patients studied. The impact of severe spasticity on a patient’s life is far-reaching, affecting everything from activities of daily living to mental health and even income. On the other hand, spasticity can be helpful in patients with weak limbs, especially in the lower extremities, by enabling the patient to transfer or ambulate with less assistance. For these reasons, the assessment of spasticity is important so that practitioners can determine if their treatment therapies are effective.
In 1964, Bryan Ashworth published the Ashworth Scale as a method of grading spasticity while working with multiple sclerosis patients. The original Ashworth scale was a 5 point numerical scale that graded spasticity from 0 to 4, with 0 being no resistance and 4 being a limb rigid in flexion or extension. In 1987, while performing a study to exam interrater reliability of manual tests of elbow flexor muscle spasticity, Bohannon and Smith modified the Ashworth scale by adding 1+ to the scale to increase sensitivity. Since its modification, the modified Ashworth scale (MAS), has been applied in clinical practice and research as a measure of spasticity. The modified Ashworth scale purpose is to grade muscle spasticity. The scale is as follows:
- 0: No increase in muscle tone
- 1: Slight increase in muscle tone, with a catch and release or minimal resistance at the end of the range of motion when an affected part(s) is moved in flexion or extension
- 1+: Slight increase in muscle tone, manifested as a catch, followed by minimal resistance through the remainder (less than half) of the range of motion
- 2: A marked increase in muscle tone throughout most of the range of motion, but affected part(s) are still easily moved
- 3: Considerable increase in muscle tone, passive movement difficult
- 4: Affected part(s) rigid in flexion or extension