Modified Ashworth Scale

Use the Modified Ashworth Scale to measure the muscle tone of your patients with neurological problems, and you'll get an idea of how far their spasticity is progressing.

By Matt Olivares on Jul 15, 2024.

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What is a Modified Ashworth Scale?

The Ashworth Scale was devised in 1964 by Bryan Ashworth to gauge muscle tone in multiple sclerosis patients (Harb & Kishner, 2020). It was later modified in 1987 by Bohannon and Smith to increase sensitivity, resulting in the widely adopted Modified Ashworth Scale (MAS) for assessing muscle spasticity.

The inter-rater reliability of grading elbow flexor muscle spasticity with the Modified Ashworth Scale was evaluated. Results showed an 86.7% agreement between raters, suggesting good reliability and supporting further trials of the scale for grading spasticity (Bohannon & Smith, 1987).

The MAS evaluates the resistance encountered during a quick stretch, with scores indicating everything from a slight increase in muscle tone to a marked increase. Other scales used in conjunction with the MAS include the Modified Tardieu Scale or the Tardieu Scale, providing a more comprehensive assessment for stroke patients and those with severe brain injury.

How to use the Modified Ashworth Scale

Physical therapists and clinicians worldwide employ the scale, and despite some critiques on its reliability, it remains a staple in measuring spasticity and treating upper limb spasticity. Here are the steps in using the scale:

Step 1: Prepare the environment

Before beginning the assessment, ensure access to a flat surface, preferably an examination table. The Modified Ashworth Scale requires the patient to be in a supine position, so assist them in lying face up if necessary, as this test is designed to monitor spasticity.

Step 2: Observe muscle tone

Once the patient is in a supine position, proceed to observe their limbs to assess muscle tone. There are two types of muscles to monitor:

  • Muscles that primarily flex joints: If you are testing a muscle that especially flexes a joint, you must place a joint in a maximally flexed position and move it to a position of maximal extension in just one second. If you need to measure the second, say "one thousand-one" out loud. Saying that should count as a second.
  • Muscles that primarily extend joints: If you are testing a muscle that primarily extends a joint, you must extend a joint in a maximally extended position and then move it to a position of maximal flexion in just one second. Make sure to count one second as you move the limb.

Step 3: Record observations

Take careful note of your observations as you assess each muscle. It is recommended that you assign a score immediately after examining each muscle before moving on to the next one.

How do you score the Modified Ashworth Scale?

The original Ashworth scale was a 5-point numerical system for grading spasticity, ranging from 0 (no resistance) to 4 (limb rigid in flexion or extension). Meanwhile, the MAS is a six-point scale, with scores ranging from 0 to 4. The scoring system is as follows (Harb & Kishner, 2023):

  • 0 means that there is no increase in muscle tone.
  • 1 means that there is a slight increase in muscle tone. This is manifested by a catch-and-release movement or minimal resistance at the end of the range of motion when the affected part(s) is moved in flexion or extension."
  • 1+ means a slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less than half) of the range of motion (ROM).
  • 2 means more marked increases in muscle tone through most of the range of motion (ROM), but the affected parts are easily moved.
  • 3 means there is a considerable increase in muscle tone and that passive movement is difficult.
  • 4 means the affected parts are rigid in flexion or extension.

The MAS is typically used to evaluate spasticity in specific muscle groups, such as the elbow flexors or wrist extensors. The examiner applies a quick, passive stretch to the joint and notes any resistance encountered. The scale can be repeated multiple times for reliability.

When does one typically use the Modified Ashworth Scale?

Healthcare professionals often use the Modified Ashworth Scale to monitor patients with neurological disorders as part of routine evaluations. This scale measures spasticity, a common issue in these patients. Here are the instances one can use the Modified Ashworth Scale:

  • Monitoring the effectiveness of treatment plans: The scale evaluates muscle tone to determine the efficacy of current treatment plans. By observing a patient's muscle tone during an examination, professionals can decide whether to maintain, adjust, or overhaul treatment plans based on changes in scores.
  • Assessing improvement or worsening of spasticity: Lower scores on the scale indicate improvement in spasticity, while higher scores indicate worsening spasticity. This helps track the progression of the condition over time.
  • Determining treatment plan components: The scale helps healthcare providers decide if physical therapy exercises should be included in the treatment plan. Additionally, it assists in determining the need for muscle relaxants, such as botulinum toxin injections, based on changes in scores for each muscle observed.

By monitoring changes in muscle tone, healthcare providers can tailor treatment plans better to address the needs of patients with neurological disorders.

Benefits and limitations

The MAS provides an objective measure of muscle tone, allowing for better tracking of progress over time and comparison between different treatment methods (Harb & Kishner, 2023).

It also helps identify specific muscles that may require more targeted interventions. In spinal cord injury and traumatic brain injury patients, the MAS can be used to monitor changes in muscle spasticity over time. For patients with multiple sclerosis or cerebral palsy, the MAS assesses the effectiveness of physical therapy interventions.

The Modified Ashworth Scale reliability seems to vary depending on the muscle group. Generally, the elbow and wrist assessments are more reliable than those of the knee and ankle plantar muscles (Figueiredo & Zeltzer, 2011).  In addition, the scale only captures a limited range of motion and does not account for variability in different muscles within a specific muscle group.

References

Bohannon, R. W., & Smith, M. B. (1987). Interrater reliability of a Modified Ashworth Scale of muscle spasticity. Physical Therapy, 67(2), 206–207. https://doi.org/10.1093/ptj/67.2.206

Figueiredo, S., & Zeltzer, L. (2011). Modified Ashworth Scale. https://strokengine.ca/en/assessments/modified-ashworth-scale/

Harb, A., & Kishner, S. (2020). Modified Ashworth Scale. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK554572/

References

Akpinar, P., Atici, A., Ozkan, F., et al. (2017). Reliability of the Modified Ashworth Scale and Modified Tardieu Scale in patients with spinal cord injuries. Spinal Cord, 55(10), 944–949. https://doi.org/10.1038/sc.2017.48

Harb, A., & Kishner, S. (2023, May 1). Modified Ashworth Scale. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK554572/

Shirley Ryan AbilityLab. (n.d.). Modified Ashworth Scale. Rehabilitation Measures Database. https://www.sralab.org/rehabilitation-measures/ashworth-scale-modified-ashworth-scale

Who uses the Modified Ashworth Scale?
Who uses the Modified Ashworth Scale?

Commonly asked questions

Who uses the Modified Ashworth Scale?

Healthcare professionals, particularly neurologists and physical therapists, use the Modified Ashworth Scale to assess muscle spasticity in patients.

How long does conducting an assessment using the Modified Ashworth Scale take?

An assessment using the Modified Ashworth Scale typically takes a few minutes or longer, depending on the muscle group evaluated.

How is the Modified Ashworth Scale administered?

The examiner passively moves the patient's limb through its range of motion and grades the resistance felt during this movement. The perceived resistance is then scored according to the Modified Ashworth scale, with a score of 0 representing no increase in muscle tone and a score of 4 indicating that the limb is rigid in flexion or extension.

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