Ashworth scale: what is it and what is it for?

The Ashworth scale is an instrument that measures the degree of spasticity or increased muscle tone., a problem that causes stiffness in the patient and a loss of balance between the contraction and relaxation of the muscles. It is a scale that must be applied and completed by the professional, with the help of the patient.

In the article we explain what the Ashworth scale and its modified version consist of, what are the items that make it up, how it is applied and what are its psychometric properties.

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What is the Ashworth scale?

The Ashworth scale, also called the Ashworth spasticity scale, is a diagnostic instrument used to measure muscle tone and spasticity, that is, the ability of muscles to hold slightly contracted.

This scale was originally created by Ashworth in 1964 and later modified by Bahannon and Smith in 1989. on what is now known as the modified Ashworth scale. This new version better measures muscle hypertonus.

This instrument consists of a clinical subjective assessment scale that allows a direct assessment of the muscle spasticity from no increase in muscle tone to extreme rigidity when flexing or extending the muscles.

The Ashworth scale was validated with neurological patients with different degrees of spasticity and has shown great reliability. interobserver, both in the evaluation of elbow flexor spasticity and in the measurement of flexor spasticity plantars.

The modified scaling adds items including the angle at which resistance appears, controlling passive movement speed with a 1 second count. This improved version is easy to use and works on all joints (although it works better with the upper extremities). However, it still has points to improve, in the degree of discrimination (between degrees +1 and -1) or sensitivity.

Items and application of the scale

The modified Ashworth scale contains five main items, ranging from 0 to 4, including an additional item on scale 1.

Being a subjective assessment scale, the score depends on the personal appreciation of the health professional who applies it. It is important to know that this scale is hetero-administered, since neither the patient nor the unqualified personnel is suitable for its application.

After observing the patient, the professional must assign values ​​from 0 to 4, with the following meaning:

• 0: normal muscle tone, total absence of increase in muscle tone.

• 1: Mild hypertonia: consists of an increase in muscle tone, either through flexion or extension. It can be observed through palpation or relaxation and involves some resistance at the end of the arc of muscle movement.

• 1+: Mild increase in muscle response resistance to movement in flexion or extension, followed by minimal resistance throughout the remainder of the arc of travel (less than half). This item complements the previous one,

• 2: moderate hypertonia: This item implies a notable increase in the resistance of the muscle during most of the arc of the joint movement, even though the joint moves easily and does not excessively limit its motion.

• 3: Intense hypertonia: consists of a marked increase in muscular resistance and implies that the passive movement is executed with difficulty.

• 4: extreme hypertonia: This last item implies that the affected parts are completely rigid, in flexion or extension, even when they move passively.

Psychometric properties

The psychometric properties of an instrument or a rating scale include properties such as validity or reliability, aspects that take into account how effective and Reliable is an instrument to evaluate what it claims to measure, or the degree to which each of the elements that compose it contribute to give stability to the measure of each characteristic.

The modified Ashworth scale has several psychometric studies that have assessed its properties. psychometrics in order to test the efficacy and reliability to measure and evaluate spasticity and hypertonia muscular.

The main conclusions reached are the following:

• Lto the Ashworth scale is reliable, useful and valid., since it responds correctly to the passive movement carried out by the health professional in a specific joint.

• The modified scale has a greater variety of items than its predecessor, because the evaluation is carried out by joints and in each hemibody of the subject. There are also certain differences in the evaluation process.

• The diagnostic instrument is an evaluative tool that promotes an appropriate assessment by requiring quantitative clinical measurements of the spasticity commitment of each subject.

• It is an appropriate tool to assess spasticity over time and thus be able to monitor the patient's improvement.

• The reliability coefficient of the test tends to its maximum expressionTherefore, the scale seems to be an instrument free of random errors, when observing that the scores of successive diagnoses have been stable in the different evaluations.

• The modified Ashworth scale has turned out to be a reliable instrument, both for the evaluation of spasticity in the upper and lower limbs.

• One of the negative aspects of the scale is that it seems to have low levels of sensitivity when there is little variability in the degree of spasticity of the subjects.

• Being a subjective instrument, there are limitations related to the profile of each evaluator professional.

Other tests that evaluate spasticity

Beyond the Ashworth scale, there is another series of tests capable of measuring spasticity. Some of the best known include:

1. Count clone keystrokes

In this test, the examining professional looks for the presence and amount of muscle contractions and relaxations. (pulses) that make movements, above and below the ankle, wrist, and other joints.

The scale is graduated from 0 to 3: 0 being the absence of pulses; 1, no sustained or few pulses; 2, sustained or continuous pulses; and 3, spontaneous or provoked by a light or sustained touch.

2. Tardieu scale

The Tardieu scale is an instrument in which the professional assessor moves the patient's muscles at different speeds., quickly and slowly, to observe if the resistance changes depending on the speed of movement.

The scale is graduated from 0 to 4, with 0 being no resistance throughout the course of stretching; 1, little resistance to a specific angle throughout the course of the stretch, with unclear muscle engagement; 2, clear engagement at a specific angle, stopping the stretch, followed by relaxation; 3, cloning appearing at a specific angle that lasts less than 10 seconds while the tester maintains pressure; and 4, the same as the item, except for the duration, which must be greater than 10 seconds.

3. Penn scale of spasm frequency

This scale aims to report how often muscle spasms occur. It is graduated from 0 to 4 as follows: 0, no spasms; 1, spasms induced by stimuli only; 2, spasms that occur less than once an hour; 3, spasms that occur more than once an hour; and 4, spasms that occur more than 10 times an hour.

Bibliographic references:

• Agredo, C. A., & Bedoya, J. m. (2005). Validation of the modified ashworth scale. Arq Neuropsiquiatr, 3, 847-51.

• Calderon-Sepulveda, R. F. (2002). Measurement scales of motor function and spasticity in cerebral palsy. Rev Mex Neuroci, 3(5), 285-89.

• Vattanasilp W, Ada L. Comparison of the Ashworth scale and clinical laboratory measures to assess spasticity. Aust J. Physiother 1999; 45: 135-139.