The Selective Control Assessment of the Lower Extremity (SCALE) is a clinical tool used to evaluate selective voluntary motor control (SVMC) in children with cerebral palsy (CP) and other neuromotor disorders. SVMC refers to the ability to activate specific muscles independently, without unintentional movement in other muscles (synergies).
Assessment Method:
- The child is asked to perform isolated movements at the hip, knee, ankle, subtalar, and toe joints while seated.
- The evaluator observes movement control, speed, and presence of involuntary synergies (e.g., unintended movements in other joints).
Scoring System (0–2 Scale per Joint):
- 2 – Normal selective movement, full isolation, and control.
- 1 – Impaired selective movement with some synergy or compensation.
- 0 – No isolated movement; only synergy-based or no movement.
Clinical Importance:
- Identifies movement limitations affecting walking, balance, and function.
- Helps guide treatment decisions, including therapy, orthotics, and surgical interventions (e.g., selective dorsal rhizotomy, tendon lengthening).
- Assists in tracking motor improvement over time.
Limitations:
- Requires cooperation and cognitive ability to follow movement commands.
- Less effective in children with severe motor impairments.
The SCALE test is particularly useful for evaluating motor control in children with spastic CP, especially those being considered for functional treatments or surgeries.
Accessing the SCALE:
The official SCALE score sheet and detailed administration guidelines are available through the International Alliance of Academies of Childhood Disability (IAACD):
Additionally, the UCLA Health website provides information about SCALE:
Pros of the SCALE:
- Standardized Assessment: SCALE offers a uniform method to quantify SVMC, facilitating consistent evaluations across different clinicians and settings.
- Reliability and Validity: Studies have demonstrated that SCALE is a reliable and valid tool for assessing SVMC in patients with cerebral palsy. onlinelibrary.wiley.com
- Clinical Utility: The assessment aids in identifying specific motor control deficits, informing targeted intervention strategies and tracking progress over time.
Cons of the SCALE:
- Training Requirements: Accurate administration and scoring of SCALE require proper training to ensure consistency and reliability.
- Time-Consuming: The assessment involves evaluating multiple joints individually, which can be time-intensive, especially in patients with significant motor impairments.
- Subjectivity: Despite standardized guidelines, some degree of subjective judgment is involved in scoring, which may affect inter-rater reliability.
For clinicians interested in implementing SCALE, it is advisable to review the official guidelines and consider training sessions to ensure accurate and reliable assessments.
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 SCALE to evaluate voluntary movement control and detect abnormal motor synergies.
- Use MAS for a quick muscle tone assessment when screening for spasticity.
- Use MTS when a detailed spasticity evaluation is needed, especially for treatment planning (e.g., botulinum toxin, surgery).