At first blush, this might seem like a logical impossibility. If you can’t move your oral structures for non-speech, how could you do so for speech? The key here is to differentiate between automatic and volitional (deliberate) oral activities. We often see children who can do all of the appropriate oral movements for eating with few problems (although they may have a history of being slow or awkward feeders); yet they cannot do the same movements in pretend or completely out of context. That is because eating movements have become automatic, while pretending to eat or following oral directions out of context takes the motions out of the realm of automaticity. For this reason, we do sometimes see children with speech apraxia only — i.e., other oral movements are not affected because they are less volitional.
Certainly, many people who have acquired apraxia due to stroke or other neurological damage in adulthood may have a great deal of automatic speech, which they produce with no trouble at all. Thus, they may seem to be more impaired in terms of volitional (nonspeech, nonfunctional) oral movements than in speech until they try to produce an unfamiliar word or a novel sentence. This makes sense: over a lifetime, speech becomes more and more automatic and therefore less and less planning is required. But a child born with apraxia hasn’t had the opportunity to develop automatic speech; many of them don’t even babble very much or very well, so they can’t benefit from that prelinguistic practice period. Therefore, I don’t think I have seen any young children whom I would describe as having oral apraxia alone. Older children, of course, could be approaching the adult case of having mastered a great deal of automatic speech over time, so that is appears that volitional oral movements that they havent practiced are harder for them than everyday speech.
On the other hand, what diagnosis could be given for a young child who speaks well but cannot plan other oral movements? It couldn’t be dysarthria. In dysarthria, the muscles themselves have reduced strength, reduced or increased muscle tone, and decreased range of movement. Since the muscles themselves are impaired, the symptoms of dysarthria must be present all the time, regardless of the situation. Thus, dysarthria affects all oral movements about equally automatic or volitional, speech or non-speech. The only possible source that I can think of for apparent oral apraxia alone would be some sort of sensory integration disorder, e.g., extreme oral hyper- or hypo-sensitivity that, for some reason, the child was able to overcome for the production of speech.
In short, I can say that oral apraxia without speech apraxia is, at the very least, very uncommon (in my opinion).
[Shelly Velleman, Ph.D., CCC-SLP is an associate professor in the Department of Communication Disorders at the University of Massachusetts – Amherst. Dr. Velleman’s research interests focus on normal and disordered child phonology, including childhood apraxia of speech. Dr. Velleman is the author of numerous articles on phonology as well as the book, “Making Phonology Functional: What Do I Do First?” and “Childhood Apraxia of Speech Resource Guide”. Dr. Velleman serves on the Professional Advisory Board of the Childhood Apraxia of Speech Association.]