Assessing Student's Needs for Assistive Technology (ASNAT)

Chapter 7 – Assistive Technology for Positioning, Seating, and Mobility
Once the most neutral head position is achieved, adaptations for the trunk can be determined. Head
supports have to be evaluated to determine their effect. Neck collars and occipital supports can provide
the necessary support to maintain the best head position. Some head supports or restraints force the head
forward, moving it from an optimal position to one that limits vision and function. Other head supports
impair lateral and posterior vision simply because they are in the way.
After hip, pelvis, and head positions are optimized, the trunk must be considered. Typically a
straight, firm, padded chair back is best however students with severe physical deformities may require
more support of their trunk in order to maintain proper positioning of other body parts. Attempting to
correct a deformity through trunk supports will only cause reduced function in other areas. Whatever
final supports are needed, it should allow the student to perform a function without requiring mental
effort to maintain the desired position.
The final rules apply to arm position and the use of a tray. Individuals with cerebral palsy often
have arm flexion and abduction with shoulder retraction that makes it difficult to bring their hands
forward and together. To successfully use their hands, they must lean forward and their chair must be
designed to facilitate this position. Through the use of humeral blocks, tray dowels to grip, and wrist
weights, a more functional position may be acquired. The height of the tray is also important. If it is too
low it may result in additional head and neck flexion and items on the tray may not be within reach. If it
is too high the student may not be able to see what is placed on the tray and it may inhibit arm use. A
tray a bit higher than normal desk height has been found to be successful for many as it encourages
trunk extension and arm elevation while inhibiting other flexor patterns. The best way to determine the
right height is to try it out.
With the body in a good position and amply supported to allow optimal function, the placement
of a communication device or switch that will control the device must be considered. Improper
placement can void all of the work already done to achieve the optimal body position. Again,
experimentation is the best way to determine appropriate placement. Generally you should consider
abnormal patterns of movement so that they are not inadvertently “triggered” during positioning. Switch
placement that requires the head to remain upright and in a neutral position are preferable to those that
allow too much head movement or those which might trigger an extension reflex.
In summary, positioning and seating are critical to the successful use of an AAC device.
Considering placement and support starting with the hips and pelvis, then the head, trunk, and arms is
imperative to achieve the best position. Tray height for the individual and task are crucial, as well.
Assessing Students’ Needs for Assistive Technology (2004) 186