Why Dysgraphia (along with other forms of poor handwriting) is a Sensorimotor Problem

by Dr. Jamie Chaves, OTD, OTR/L, SWC

It is amazing that we can even write at all. Handwriting requires the integration of almost every sensory system in order to create a legible, organized product. When a breakdown occurs in any or several sensory systems, handwriting is generally negatively impacted. It is therefore important that when exploring the best therapeutic options for a child with dysgraphia or poor handwriting that a comprehensive sensorimotor occupational therapy evaluation be conducted. This includes exploring how a child responds to vestibular, proprioceptive, tactile, and visual inputs, as well as the child’s postural stability and praxis. (NOTE: postural stability and praxis essentially require the integration of the vestibular, proprioceptive, and tactile systems.) Here’s a glimpse at what needs to happen in order for handwriting to be successful.

Sitting upright in a chair: requires the integration of the vestibular, proprioceptive, and tactile systems in order to maintain postural stability and modulation of tactile input from the seat of the chair. “Proximal stability equals distal mobility” is a commonly used, and very foundational, catch phrase. This means that in order for us to effectively move our wrists and fingers we must first establish stability in our shoulders and core muscles. Children with poor postural stability (those who lean on other people or objects, prefer to lie down, have difficulty sitting in a chair) notoriously have poor handwriting. It is integral to all other aspects of handwriting, so I won’t continue to list it. Also, if a child is sensitive to tactile input and is sitting on a wooden chair or a chair with a textured seat, he or she may be too distracted by that feeling to stay attentive to writing.

Holding a pencil: requires modulation of tactile input from the writing tool on the fingers, discrimination of proprioceptive input to use the right amount of force, tactile discrimination and praxis to move each finger in a distinct position on the pencil, and vestibular discrimination to hold the pencil up against gravity. For children who don’t like the feeling of the pencil, grip the pencil too tightly (or loosely), position their fingers incorrectly on the pencil, or fatigue easily when holding a pencil, it is important to further investigate the corresponding sensory systems.

Manipulating a pencil: requires praxis to move the fingers apart from the rest of the hand and arm, discrimination of proprioceptive input to know how much pressure to use on the paper, and vestibular discrimination to know which direction to move the pencil. When we write our fingers do the majority of the work and must move on their own to be more efficient. Children who tire easily with handwriting may be engaging too many muscles to complete the task or may be pushing too hard on the paper. Or they may be using so much effort to isolate the movement of their fingers because their motor planning is off. Detecting up, down, forward, and backward is really important for moving the pencil in the direction needed to form shapes and letters.

Forming shapes and letters: requires praxis to remember the necessary motor pattern, body awareness (proprioceptive and vestibular integration) to understand laterality, visuo-vestibular integration so the eyes and hand can move in a coordinated manner, and visual modulation as to not get overwhelmed (or underwhelmed) with the visual input on the paper. As we progress in our handwriting skills we don’t even need to think about how to form each letter - it just happens because of praxis. When we learn a new symbol or form of writing we must concentrate more because our praxis is not yet automatic (this is what some children must do every time they write!). At the same time, being well acquainted with our body in relationship to itself must occur so we can understand our body in relationship to the writing tool being manipulated. This means we must consistently differentiate our right from our left (i.e., laterality) so we can differentiate letters facing right versus left. The visual and vestibular systems work very closely together to inform each other of where to keep our eyes oriented on the paper and where to form the letters. If these two systems are out of sync, which happens quite often in children with sensory processing disorder, then the head and eyes can have a difficult time remaining stable while the hand is moving. For children who get overwhelmed by visual input, the lines on the paper, amount of writing, or colors on the paper may be too much. Many children nowadays, however, have the opposite problem and are so underwhelmed with the mundane nature of gray pencil on white paper in contrast to fast-paced, colorful video screens.

It is important to mention several areas of visual-perceptual that also influence handwriting, such as visual attention, visual memory, visual spatial skills, and visual form. These are higher level cognitive processes that interpret visual information. While they can be assessed and addressed by an occupational therapist, they are not in and of themselves a sensory processing disorder. Similarly, occulomotor skills, such as visual tracking, visual saccades, and visual convergence can be screened by an occupational therapist to determine if a full evaluation by a developmental optometrist is warranted.  

There you have it. Now you can see why handwriting is such a complex process, and why dysgraphia cannot effectively be remediated by simply practicing writing over and over (although some practice is necessary). Educators, parents, and other professionals can have a profound role in recognizing handwriting problems early and recommending a comprehensive sensorimotor evaluation by an occupational therapist to get at the root of the issue.