ASHWORTH SCALE: ITEMS AND STATISTICAL PROPERTIES - NEUROPSYCHOLOGY - 2025

The Ashworth scale or Ashworth spasticity scale is an instrument used to assess muscle spasticity in people. This scale was created in 1964 by Ashworth and later modified by Bahannon and Smith in 1987.

It consists of a clinical subjective assessment scale. Its main value is that it allows direct measurement of spasticity, graduating the tone from 0 (without increasing the volume) to 4 (rigid limb in flexion or extension).

This instrument has been shown to be highly reliable through its modified version both in the evaluation of elbow flexor spasticity and in the evaluation of plantar flexor spasticity.

characteristics

The Ashworth scale is a psychometric instrument used to assess muscle spasticity in people. It was made in 1964 by Ashworth, however, currently only the modified Ashworth scale made by Bohannon and Smith in 1987 is used.

This scale is characterized by evaluating spasticity in five main categories (from 0 to 4). The value 0 indicates a total deficit of increased muscle tone, while the value 4 specifies that the affected parts are stiff in both flexion and extension when they move passively.

The classic Ashworth scale (developed by Ashworth) presented only two items (upper limbs and lower limbs), which is why it was an instrument with low reliability.

In contrast, the modified Ashworth scale includes a total of five items, plus a sub-item for the second scale of the instrument, thus resulting in a much more reliable tool.

At present, the Ashworth scale stands out as one of the most widely used instruments to assess muscle spasticity and is a highly used tool in the field of medicine and physiotherapy.

Scale items

The Ashworth scale has five main items ranging from 0 to four, including an additional item on scale 1.

The determination of each of the items on the scale is subjective, so it depends on the personal appreciation of the professional who applies it.

For this reason, it is a hetero-administered scale that cannot be self-administered by the subject himself or by personnel not qualified for its use.

The items on the Ashworth scale are as follows:

0. Normal muscle tone

The first item on the scale is used to establish the presence of a totally normal muscle tone in the person. This item implies the total absence of increased tone in the muscles.

1. Mild hypertonia

The second item on the scale indicates a slight increase in the muscle's response to movement, either by flexion or by extension.

This increased muscle response is visible on palpation or relaxation, and involves minimal resistance at the end of the range of motion.

It is an increase in muscle tone with "arrest" in passive limb movement and minimal resistance in less than half the limb's range of motion.

1+. Slight increase in muscle resistance to movement

This item serves to complement the previous item. Specifies a slight increase in muscle resistance to flexion or extension movement, followed by minimal resistance throughout the remainder of the range of motion.

2. Moderate hypertonia

This fourth item specifies a notable increase in muscle resistance during most of the joint range of motion. However, the joint remains moving easily.

Increased muscle tone is seen throughout most of the range of motion, although it does not excessively limit joint motion.

3. Severe hypertonia

For the determination of item three on the scale, a marked increase in muscle resistance must be witnessed. There is a prominent increase in muscle tone, with difficulty in passive movements.

4. Extreme hypertonia

Finally, in this last item, the affected parts present a totally rigid state in flexion or extension, and even when they move passively.

Psychometric properties

The Modified Ashworth Scale has several psychometric studies that have tested its efficacy and reliability properties to measure spasticity. In this sense, the main characteristics of the scale are:

1-It is a reliable, useful and valid instrument since it responds to the passive movement made by the evaluator to a specific joint.

2-It consists of an evaluative tool that can lead to the best assessment by requiring a quantitative clinical measure of the compromise of spasticity in each patient.

3-The modified Ashworth scale has a greater variety of items than the traditional Ashworth scale when evaluating by joints and by each person's hemibody. Likewise, both scales differ in the evaluation procedure.

4-It allows measuring spasticity over time, making it a good tool for monitoring patients with this type of problem.

5-It is an instrument that is free of random errors as far as the differences are close to zero, since diagnoses two and three have been stable in the different evaluations carried out.

6-The modified Ashworth scale, unlike the traditional scale, is a reliable evaluative instrument in both upper and lower limbs.

7-Certain studies have reported that the scale does not detect significant changes in sensitivity when there is little variability in the degree of spasticity of patients.

8-The modified Ashworth scale is an instrument validated by the sectional organization MSF Cali.

9-The main limitations of the scale are related to the characteristics of each evaluator, since it consists of a subjective instrument.

References

1. Ashworth, B. (1964).sepeap.org.
2. Bohannon RW, Smith MB. (1987). sepeap.org.
3. Collazos, Larry; Garcia, Gloria. Physiotherapeutic intervention in patients with Guillan Barre syndrome in each of its stages. THESIS. Valley University 2000.
4. Vattanasilp W, Ada L. Comparison of the Ashworth scale and clinical laboratory measures to assess spasticity. Aust J. Physiother 1999; 45: 135-139.