Cerebral palsy (CP) is one of the most common reasons people use AAC. The condition affects motor control, which can impact speech production even when language understanding and cognitive ability are intact. Many people with CP have a lot to say but lack the motor control to say it through speech alone.
Choosing the right AAC system for someone with CP requires careful attention to motor abilities, positioning, fatigue, and how these factors change over the course of a day. A system that works perfectly at a desk may be unusable in a wheelchair. An access method that works in the morning may fail when fatigue sets in by afternoon.
This guide covers the key considerations for selecting and setting up AAC for people with cerebral palsy.
Communication Challenges in Cerebral Palsy
CP affects motor control, but it affects people in widely different ways. Some individuals have mild difficulty with fine motor tasks but speak clearly. Others have significant involvement affecting all four limbs, trunk control, and the muscles used for speech.
The speech-related challenges in CP typically involve dysarthria, a motor speech disorder caused by impaired control of the muscles used for speaking. Dysarthria in CP can affect:
- Breath support for voicing
- Vocal cord coordination
- Movement of the tongue, lips, and jaw
- Speed and rhythm of speech
- Volume control
The severity ranges from mild (speech is intelligible but effortful) to severe (speech is not a functional communication method). Many people with CP fall somewhere in between, able to communicate with familiar listeners but not with strangers, or able to speak in quiet settings but not in noisy environments.
Motor Access Methods
The most critical decision in AAC for CP is choosing the right access method. This determines how the person physically selects symbols or letters on the device.
Direct Selection
Direct selection means the person touches or points to what they want. This is the fastest access method and allows the most independence. For people with CP, direct selection may involve:
- Finger touch on a touchscreen (with or without a keyguard)
- Stylus or head pointer for people with better head control than hand control
- Fist or knuckle touch for those who can't isolate a finger but can target an area
Direct selection works when the person can reliably reach and activate a target. The key question is accuracy. If someone can touch within a 2 cm target area, that determines how large the buttons on their AAC system need to be.
Keyguards are physical overlays with holes cut for each button. They provide a physical barrier that prevents accidental touches and give the user something to rest against while targeting. For many people with CP, a keyguard is the difference between direct selection working and not working.
| Access Factor | Consideration for CP |
|---|---|
| Target size | Larger targets are easier but reduce vocabulary per page |
| Target spacing | More space between buttons reduces accidental activations |
| Keyguard | Prevents accidental touches, provides physical support |
| Screen position | Angled screens may be easier to reach than flat ones |
| Activation method | Touch vs. release vs. dwell time |
Scanning
Scanning is used when direct selection is not reliable. In scanning, items are highlighted one at a time (or in groups), and the user activates a switch when the desired item is highlighted.
For CP, common scanning setups include:
- Single switch scanning. Items are highlighted automatically at a set speed. The user presses one switch to select. Simple to operate, but slow.
- Two-switch scanning. One switch advances the highlight, the other selects. Faster than single switch because the user controls the pace.
- Row-column scanning. Items are grouped in rows. The user first selects a row, then scans within that row to find the specific item. This is faster than scanning every item individually.
The switch itself needs to match the person's most reliable motor movement. Common switch sites for people with CP include:
- Hand or thumb (most common, if fine motor control allows)
- Head (using a head-rest mounted switch)
- Knee or foot
- Elbow
- Cheek or eyebrow (for individuals with very limited movement)
Eye Gaze
Eye gaze technology tracks where a person is looking on a screen and uses that to select items. For people with severe CP who cannot reliably use their hands or a switch, eye gaze may be the best option.
Modern eye gaze systems use infrared cameras mounted on or near the screen. The technology has improved dramatically in the last decade. Current systems can work with glasses, in varying lighting conditions, and with some head movement.
Considerations for eye gaze with CP:
- Head stability. Significant involuntary head movement can disrupt tracking. Proper positioning is essential.
- Vision. Some people with CP have visual impairments (cortical visual impairment, strabismus) that affect eye gaze accuracy.
- Fatigue. Eye gaze requires sustained visual attention. Some users find it tiring over long periods.
- Calibration. The system needs to be calibrated to the individual. Recalibration may be needed if positioning changes.
- Cost. Eye gaze hardware adds $3,000 to $7,000 to the cost of an AAC system.
Vocabulary Organization for Motor Difficulties
How vocabulary is organized on the screen directly affects how efficiently someone with motor challenges can communicate.
Motor planning and consistency
For people with CP, motor planning (learning the physical movements to reach targets) is a critical consideration. Vocabulary should be organized so that frequently used words are always in the same location. This allows the user to develop motor plans for common words, making access faster and less effortful over time.
This is why grid-based systems with consistent layouts work well for many AAC users with CP. Once someone learns that "want" is always in the top-left corner, they can navigate there without searching. That motor memory becomes automatic, like typing on a keyboard.
Grid size trade-offs
Larger grids (more buttons per page) mean more vocabulary is accessible without page navigation, but the individual buttons are smaller. Smaller grids (fewer buttons per page) have larger buttons that are easier to hit, but require more page navigation to find vocabulary.
| Grid Size | Button Size | Vocabulary Per Page | Navigation Needed | Best For |
|---|---|---|---|---|
| 4 x 4 | Large | 16 items | High | Significant motor limitations, early communicators |
| 5 x 7 | Medium | 35 items | Moderate | Moderate motor limitations |
| 7 x 10 | Small | 70 items | Low | Good fine motor, experienced users |
| 9 x 12 | Very small | 108 items | Minimal | Precise motor control, advanced users |
The right grid size depends on the individual's motor accuracy, but also on their language level. A person who is combining multiple words per message needs quick access to a lot of vocabulary, which argues for a larger grid. A person who is building single-word communication may do better with a smaller grid and larger targets.
Core word placement
Core words (the 50 to 100 most frequently used words in any language) should occupy the prime real estate on the screen. These words, like "want," "go," "more," "help," "not," "like," and "that," are used across every context and make up the vast majority of what we say (Banajee, DiCarlo, & Stricklin, 2003).
Placing core words in consistent, easy-to-reach locations reduces the motor demands of everyday communication. Fringe vocabulary (specific nouns like "pizza" or "playground") can be organized in category pages that are accessed less frequently.
Positioning and Mounting
The physical setup of an AAC device is as important as the device itself. Poor positioning leads to fatigue, reduced accuracy, and eventually abandonment of the system.
Key Positioning Principles
The device should be at a comfortable viewing angle. For most people, this means the screen is slightly below eye level and tilted toward the user. Flat surfaces require the user to look straight down, which strains the neck.
The user should not have to reach far. If the device is mounted too far away, every selection requires a large arm movement. This increases fatigue and reduces accuracy. The device should be positioned within comfortable arm's reach, which for most people is within 30 to 40 cm of the body.
Support the trunk first. Stable seating and trunk support improve upper extremity function. A person who is struggling to stay upright in their chair will have worse hand control than the same person in well-fitted seating. Seating should be optimized before fine-tuning device positioning.
Consider different positions throughout the day. A person may use their wheelchair, a classroom chair, a stander, and a bed throughout the day. The AAC system needs to be accessible in each position. This may require multiple mounts or a device that is easily repositioned.
Mounting Systems
For wheelchair users, a mount attaches the AAC device to the wheelchair frame. Key features to evaluate:
- Adjustability. Can the mount be swung out of the way for transfers and activities?
- Stability. Does it hold the device firmly without wobbling when the user touches the screen?
- Reach. Does it position the device within the user's comfortable reach zone?
- Weight capacity. Can it support the device plus any accessories (keyguard, case)?
Research on AAC Outcomes in Cerebral Palsy
Clarke, Price, and Jolleff (2001)
Clarke and colleagues studied the communication outcomes of individuals with CP who used AAC and found that those who received AAC intervention early and consistently showed better communication outcomes than those who started later. They also found that the degree of motor impairment was less predictive of AAC success than the quality of the AAC intervention and the support from communication partners.
Pennington, Goldbart, and Marshall (2004)
This systematic review examined speech and language therapy interventions for children with CP and found that AAC interventions, including both aided (device-based) and unaided (sign and gesture) approaches, were associated with improvements in communication for children across the motor severity spectrum.
They noted that the evidence base, while growing, still needed larger studies with stronger designs. But the direction of findings was consistently positive: AAC helps people with CP communicate more effectively.
Hustad, Gorton, and Lee (2010)
Hustad and colleagues studied speech intelligibility in children with CP and found that many children classified as having "functional speech" were actually intelligible less than 50% of the time to unfamiliar listeners. This finding highlighted the gap between how well a child communicates with familiar people versus strangers, and it supported the use of AAC even for children whose speech is sometimes understood.
Getting Started
If you're exploring AAC for someone with cerebral palsy, here are the first steps:
1. Get an AAC evaluation
Request a comprehensive AAC evaluation from an SLP who specializes in AAC. This evaluation should assess:
- Current communication abilities (speech, gesture, vocalizations)
- Motor abilities for different access methods
- Language and literacy levels
- Communication needs across settings
- Seating and positioning
2. Trial multiple access methods
Don't commit to an access method without trying alternatives. A good evaluation includes trials with direct selection (various target sizes), scanning (various switch types and sites), and possibly eye gaze. What works best may surprise you.
3. Get seating and positioning right first
Work with an occupational therapist or seating specialist to optimize the person's physical setup before fine-tuning the AAC system. Better seating means better motor control means better AAC access.
4. Start communicating immediately
Don't wait for the "perfect" system. Use a free AAC app on a tablet to start building communication skills while the formal evaluation and funding processes proceed. The vocabulary, language, and social skills a person develops on a starter system transfer directly to whatever system they use long-term.
5. Plan for change
CP is a lifelong condition, and motor abilities can change over time. The access method that works at age 5 may not work at age 15. Build in regular reassessment, at least annually, and be prepared to adapt the system as the person's needs change.
Download SabiKo free and start exploring AAC today.
References
- Banajee, M., DiCarlo, C., & Stricklin, S.B. (2003). Core vocabulary determination for toddlers. Augmentative and Alternative Communication, 19(2), 67-73.
- Clarke, M., Price, K., & Jolleff, N. (2001). Augmentative and alternative communication for children with cerebral palsy. Paediatric Rehabilitation, 4(2), 87-96.
- Pennington, L., Goldbart, J., & Marshall, J. (2004). Speech and language therapy to improve the communication skills of children with cerebral palsy. Cochrane Database of Systematic Reviews, (2).
- Hustad, K.C., Gorton, K., & Lee, J. (2010). Classification of speech and language profiles in 4-year-old children with cerebral palsy: A prospective preliminary study. Journal of Speech, Language, and Hearing Research, 53(6), 1496-1513.
- Beukelman, D.R., & Light, J.C. (2020). Augmentative and Alternative Communication: Supporting Children and Adults with Complex Communication Needs (5th ed.). Paul H. Brookes Publishing.
- Geytenbeek, J.J., Harlaar, L., Stam, M., Ket, H., Becher, J.G., & Vermeulen, R.J. (2010). Utility of language comprehension tests for unintelligible or non-speaking children with cerebral palsy: A systematic review. Developmental Medicine & Child Neurology, 52(12), 1098-1109.