Apraxia of speech (AOS) is a motor speech disorder that makes it difficult for children to speak clearly and be understood. AOS is characterized by difficulties planning and producing the precise movements of the tongue, lips, jaw and other speech muscles needed for intelligible speech.
AOS can occur on its own or alongside other conditions like autism spectrum disorder (ASD). There has been much debate over whether AOS can occur in isolation without autism. This article will examine the latest research on AOS and whether it is possible for a child to have apraxia without autism.
Key Features of Childhood Apraxia of Speech
Some key features of childhood AOS include:
- Difficulty sequencing sounds and syllables accurately and consistently
- Frequent speech sound errors and distortions
- Groping movements of the articulators (lips, tongue, jaw) to make sounds
- Vowel and consonant distortions
- Abnormal prosody – inappropriate silencing, prolonging or stressing syllables and words
- Difficulty transitioning between sounds and syllables
- Better comprehension than speech production abilities
These core features can occur in AOS whether autism is present or not. However, in ASD there are wider communication challenges including problems with semantics, pragmatics and social interaction.
Overlap Between AOS and ASD
There is considerable overlap between symptoms of AOS and autism spectrum disorders during early childhood which can make differential diagnosis challenging.
Some shared characteristics include:
- Delayed language development
- Reduced babbling as infants
- Abnormal prosody
- Repetitive speech
- Poor speech intelligibility
Around 30% of children with ASD have comorbid childhood AOS. The considerable symptom overlap means that AOS can be mistaken for more general communication deficits related to ASD.
Detailed assessment by a speech-language pathologist is needed to tease apart a diagnosis of pure AOS versus ASD with AOS. Making the right diagnosis ensures the child receives appropriate interventions tailored to their needs.
Evidence that AOS can Occur Without ASD
So does the research show that childhood AOS can occur in the absence of autism spectrum disorder?
Several studies provide evidence that AOS can occur as an isolated condition without ASD:
Genetic Studies
Genetic studies show distinct genetic markers between AOS and ASD:
- FOXP2 gene mutations associated with AOS but not ASD
- CNTNAP2 gene associated with ASD but not pure AOS
This indicates independent genetic influences on AOS versus ASD.
Neuroimaging Studies
Neuroimaging studies reveal some differences in brain structure and function between AOS and ASD:
- More left hemisphere abnormalities in AOS
- More right hemisphere and diffuse abnormalities in ASD
- Some unique neural markers for AOS versus ASD
Intervention Response
Children with isolated AOS tend to respond better to speech therapy targeting motor planning and programming skills compared to children with AOS+ASD.
Case Studies
There are published case studies of children with well-documented developmental AOS without autism. These provide proof that pure AOS does occur.
Key Differences Between AOS and ASD
There are some key ways symptoms of AOS differ from the communication deficits seen in ASD:
| AOS | ASD |
|---|---|
| Core deficit in planning/programming speech movements | Core deficits in social communication and interaction |
| Speech is main impairment | Wide ranging language, social and behavioral impairments |
| No delay in language comprehension | Delayed language comprehension common |
| No repetitive/restrictive behaviors | Repetitive/restrictive behaviors and interests common |
| No significant nonverbal communication deficits | Impaired nonverbal communication e.g. gestures, facial expressions |
These key differences in symptoms help distinguish isolated AOS from ASD with accompanying apraxia traits.
Conclusion
In summary, while AOS and ASD have overlapping characteristics, research indicates childhood apraxia of speech can and does occur as a stand-alone motor speech disorder without autism:
- Genetic studies reveal distinct gene markers for AOS vs ASD
- Neuroimaging points to unique neural correlates of pure AOS
- Children with isolated AOS respond better to targeted speech therapy
- There are documented case studies of AOS without ASD
- There are key symptom differences between AOS and social communication deficits in ASD
However, given the high rate of co-occurrence, any child diagnosed with AOS should also be evaluated for autism spectrum disorder by an experienced professional. Early intensive interventions tailored to the child’s profile gives them the best chance of improving communication abilities and outcomes.
References
American Speech-Language-Hearing Association. (2007). Childhood apraxia of speech [Position Statement]. Available from www.asha.org/policy.
Grigos, M. I., Moss, A., & Lu, Y. (2015). Oral articulatory control in childhood apraxia of speech. Seminars in Speech and Language, 36(1), 29–43.
Lewis, B. A., Freebairn, L. A., Hansen, A. J., Iyengar, S. K., & Taylor, H. G. (2004). School-age follow-up of children with childhood apraxia of speech. Language, Speech, and Hearing Services in Schools, 35(2), 122–140.
Preston, J. L., Molfese, P. J., Mencl, W. E., Frost, S. J., Hoeft, F., Fulbright, R. K., Landi, N., Grigorenko, E. L., Seki, A., Felsenfeld, S., & Pugh, K. R. (2014). Structural brain predictors of late speech development. Cerebral Cortex, 24(10), 2705–2715.