The Modified Ashworth Scale (MAS) is a clinical tool used to assess spasticity by measuring resistance to passive muscle stretch. It is widely used in children with cerebral palsy (CP) and other neurological conditions affecting muscle tone.
Scoring System:
The MAS rates spasticity on a 0 to 4 scale, with higher scores indicating greater muscle stiffness:
- 0 – No increase in muscle tone.
- 1 – Slight increase in tone, with a catch-and-release or minimal resistance at the end of the range.
- 1+ – Slight increase in tone with a catch, followed by minimal resistance through the rest of the range.
- 2 – More marked increase in tone throughout most of the range, but limb moves easily.
- 3 – Considerable increase in tone; passive movement is difficult.
- 4 – Rigid limb in flexion or extension.
Accessing the MAS:
Detailed instructions for administering the MAS, including scoring criteria and testing forms, are available from the Shirley Ryan AbilityLab:
Pros of the MAS:
- Ease of Use: The MAS is quick to administer and does not require specialized equipment, making it practical for various clinical settings.
- Standardized Assessment: Provides a uniform method to evaluate muscle tone, facilitating consistent documentation and communication among healthcare professionals.
- Clinical Utility: Widely adopted in both practice and research to assess the effectiveness of interventions aimed at reducing spasticity.
Cons of the MAS:
- Subjectivity: The assessment relies on the examiner’s perception of resistance, which can introduce variability and affect inter-rater reliability.
- Limited Sensitivity: The scale may not detect subtle changes in spasticity, potentially limiting its responsiveness to minor improvements or deteriorations. Does not distinguish between spasticity and contractures.
- Focus on Passive Movement: Evaluates resistance during passive movement only, not accounting for spasticity’s impact during active functional activities.
For accurate application, clinicians should familiarize themselves with the MAS protocol and consider supplementing it with additional assessments to obtain a comprehensive understanding of a patient’s spasticity and functional abilities.
Comparison of SCALE, MAS, and MTS in Cerebral Palsy Assessment
| Feature | Selective Control Assessment of the Lower Extremity (SCALE) | Modified Ashworth Scale (MAS) | Modified Tardieu Scale (MTS) |
|---|---|---|---|
| Purpose | Assesses selective voluntary motor control (SVMC) and ability to move joints independently. | Measures muscle tone and resistance to passive movement. | Evaluates spasticity at different speeds to differentiate it from contractures. |
| Key Focus | Voluntary movement control and synergy patterns. | Muscle stiffness and hypertonia. | Spasticity dynamics and range of motion limitations. |
| Measurement Method | Child performs active movements at hip, knee, ankle, subtalar, and toe joints. | Passive limb movement at a single speed. | Passive movement at slow (V1) and fast (V3) speeds. |
| Scoring Scale | 0-2 per joint (higher score = better selective control). | 0-4 scale (higher score = more tone/stiffness). | 0-5 scale (higher score = more spasticity/clonus). |
| Spasticity vs. Contractures | Not assessed. Focuses on movement control. | Cannot differentiate between spasticity and contractures. | Can differentiate (if R1 and R2 differ, spasticity is present). |
| Velocity Dependency | No (assesses voluntary movement control). | No (measures resistance at a single speed). | Yes (tests response to different movement speeds). |
| Best For | Identifying motor control issues and synergistic movement patterns. | Quick spasticity screening, simple to use. | More detailed spasticity assessment, guiding interventions. |
| Limitations | Requires cognitive ability to follow movement instructions; may not work for children with severe motor impairments. | Subjective, does not account for velocity-dependent spasticity. | More complex, requires trained assessors for accuracy. |
Which One to Use?
Use MTS when a detailed spasticity evaluation is needed, especially for treatment planning (e.g., botulinum toxin, surgery).
Use SCALE to evaluate voluntary movement control and detect abnormal motor synergies.
Use MAS for a quick muscle tone assessment when screening for spasticity.