Apraxia of speech (AOS) is a motor disorder of speech. In the case of AOS, the difficulty producing speech lies in the inability to correctly form and coordinate lips, tongue, and mouth appropriately to produce language. The muscles needed to talk develop normally, however, their control is affected, which results in difficulty moving or transitioning smoothly from one sound, syllable, or word to another.
AOS is a motor speech disorder.
There are two types of AOS: childhood and acquired.
The primary treatment for AOS is speech therapy.
Children can outgrow AOS.
Acquired AOS is can by brain pathology or trauma.
AOS is a rare disorder, broadly categorized into two main types: childhood and acquired AOS. The prevalence of AOS in children is low, with reported cases of less than 1%. Given that acquired AOS is related to traumatic brain injury, stroke, brain tumor, and other causes, the prevalence rates are slightly higher but not reported. Both types of AOS can manifest in males and females without a noticeable difference in prevalence rates.
Childhood AOS, as it suggests, manifests in children. Because the language’s developmental period occurs between 2 and 3 years of age, it is extremely difficult to diagnose AOS in young children who are still learning to speak. Signs of AOS in children often present as “speech, language, or words that are difficult to understand” and appear when a child wants to say something but has trouble “getting it out”.
Causes for childhood AOS are largely unknown. Scientists believe that AOS in children results from functional deficits, meaning that the communication between the brain and muscles involved in speech production is not functioning as they are supposed to. However, clinicians do not report observable changes in the brain of children with AOS.
Acquired AOS can appear at any age and is primarily related to brain damage or trauma. The most common cause is vascular lesions, especially left hemisphere stroke. In addition, other types of neurological conditions and/or injuries can result in AOS.
AOS severity varies highly. In the most extreme cases, it can cause almost a complete loss of speech, whereas, in others, it can be very mild. The main characteristic of AOS is incorrect articulation caused by disrupted motor movements involved in producing speech. People with AOS know what they want to convey and can select the correct word phonemes; however, they are unable to say them correctly.
In addition, in children, AOS symptoms may include:
- Less than normal babbling and/or vocal sounds between 7 and 12 months of age.
- Late onset of speech in general (saying first words late).
- Using a limited number of sounds, syllables.
- Speech is difficult for others to understand.
Individuals with acquired AOS may exhibit one or more of the following symptoms:
- Abnormal speech rhythm.
- Incorrectly stressing words.
- Abnormal intonation.
- Difficulties initiating utterances.
- Repetition of particular utterances.
- Incorrect utterance articulation.
- Struggle with noticing/correcting errors in speech.
- Leaving out particular phonemes, sounds.
Examples of symptomatology
Most frequently, the place of articulation in one word or intonation in a sentence is affected. Studies indicate that affricate phonemes, for example, “ch” in the word church or “j” in the word “jar”, are extremely difficult for AOS patients. Fricative phoneme mistakes are also very common. They require friction of breath with a narrow opening of the mouth, for example, consonants “f” and “th”. Experts believe that consonant clusters are more challenging for individuals with AOS since they require a finer motor execution, for example, words such as “strict”. In addition, individuals will struggle to repeat nonsense words compared to healthy individuals.
In sentences, patients with AOS may attribute the same stress to each word, which sounds unnatural. Overall, they will have a slower rate of speech than normal, with long pauses between words. The following is an example of recorded speech of an individual with AOS who was attempting to say the word “cushion”:
“Oh, uh, uh chookun, uh, uh, uh, dook, I know what it's called, it's c-u, uh, not it's chookun, no …”
Children can outgrow AOS naturally. However, in the cases where childhood AOS persists, therapy is highly recommended. If you have concerns about your child's speech, or its delayed onset, discuss those concerns with your primary physician.
In the case of acquired AOS, given that it is primarily caused by a pathological condition or trauma, medical staff or close relations will notice changes in speech.
Speech therapy is the primary treatment for both types of AOS. Given that AOS symptoms and severity can vary greatly between individuals, a dedicated speech pathologist will offer the most suitable approach.
Research indicates that one type of therapeutic approach will not suit all AOS patients. However, most commonly, therapy focuses on increasing communicative effectiveness. For mild AOS, therapy focuses on speech rhythm and intonation. In more severe cases, therapy also includes relearning oral postures (mouth, tongue, and lip formation) and particular speech sounds.
Speech therapists may suggest exercises that could be done at home to improve the rate of recovery for both, childhood and acquired AOS. Unfortunately, there are no studies summarizing the prognosis of AOS, primarily due to very vast individual differences and causes of this disorder. In the case of childhood AOS, most children eventually develop normal speech patterns. In the case of acquired AOS, the outcome heavily depends on the extent of brain damage. Your clinician will be able to provide you with an individual assessment of recovery.