08 Mar Childhood Speech Disorder Apraxia: Underlying Brain Pathway Identified
MedicalResearch.com Interview with:
Prof. Angela Morgan PhD
NHMRC Practitioner Fellow and
Leads the Speech and Language Group
Murdoch Children’s Research Institute
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Approximately 5% of school-aged children have a communication impairment that affects speech, language, or both. There are many subtypes of speech sound disorders, but the most severe is (CAS), which impacts sequencing of speech movements. Childhood apraxia of speech occurs in around 1 in 1000 children. In persistent cases of CAS, speech cannot easily be understood throughout life. Although CAS is rare, unravelling its neurobiological causes is likely to identify brain networks crucial to more common and less severe forms of speech disorders.
Here we provide comprehensive speech and neuroimaging data on a large novel family where one parent and 11 children presented with features of childhood apraxia of speech. Brain MRI scanning revealed changes in core parts of the brain responsible for speech production. Even though CAS manifests as a problem with talking, we found disruptions in an underlying pathway of the brain normally associated with language (the meaning and grammar of what we say), rather than speech production. Our findings identify disruption of the dorsal language stream as a novel finding in developmental speech disorders. Overall, our data confirm the early role of this stream in auditory-to-articulation transformations.
MedicalResearch.com: What should readers take away from your report?
Response: As suspected, it appears that different sub-types of speech sound disorder are, in turn, subserved by different brain pathways and brain changes. This calls into question a one size fits all approach to speech disorder treatment, which is the current approach.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: It would be helpful for future research to examine the neural bases of severe speech disorder sub-types in other families and individuals in order to confirm and expand on our findings. Future genetic research is also critical, to pinpoint the specific biological pathways associated with these speech conditions. It is likely that genetic changes alter the development of the brain pathways subserving speech and this leads to the speech disorder. There is some early evidence for this already in the literature, in a study lead by Simon Fisher and colleagues at the Max Planck Institute for Psycholinguistics.
MedicalResearch.com: If a family has a child with apraxia what are the signs/symptoms they will notice and at what age?
Response: By age 3, children should be easily understood by family and friends when speaking. If your child is not able to be understood by these familiar listeners, it suggests they could have a speech disorder. Signs and symptoms start early. Apraxia is often associated with a history of early feeding difficulties and limited babbling in the first year of life. From 12 months onwards, children have delayed first words and they also pick up new words very slowly. It may be reported that they have used a word but then seem to ‘lose’ that word, or that they don’t say the word in the same way each time. Children find speaking so difficult that they often rely on pointing or gestures to get their message across. Children with apraxia may appear to really struggle to ‘get the words out’. It is clear that talking is really not an easy task for them.
MedicalResearch.com: Apraxia is one in 1000, but other speech disorders in children are more common. What should parents be looking for if they suspect their child has a speech disorder? What kinds of speech disorders do children tend to grow out of? Who should parents consult if they are concerned?
Response: Most speech challenges are overcome in the preschool years. The most common forms of speech sound disorder are articulation and phonological delay or disorder. An articulation disorder is best described when we think about a lisp on the sound ‘s’. In an articulation disorder, the child is making an approximation of the correct sound, but the sound is slightly distorted as it is not made in exactly the right way. Whereas a phonological disorder is best described as when children do not understand which sounds to use in which positions in words. Children with phonological disorders tend to ‘swap’ sounds around, e.g., ‘tup’ for ‘cup’, or even omit sounds from the beginning or ends of words, e.g. ‘do’ for ‘dog’. Some of these errors are typical in all young children under 4 years of age, and hence most children simply grow out of these error patterns. Where a speech problem is more persistent, or if parents and family are unable to understand the child at age 3, perhaps they should seek help from a speech pathologist if they are concerned.
MedicalResearch.com: How is apraxia diagnosed?
Response: Apraxia is diagnosed by a speech pathologist. The speech pathologist conducts a series of speech tasks that probe whether the child has developed all of the sounds of their language, and whether they can use these sounds in the correct manner. They are also looking to see whether the child has more common forms of speech disorder, such as articulation and phonological disorder discussed above, or whether the child has more significant error patterns as seen in apraxia. It is challenging to diagnose apraxia in younger children who may not have as much language. In these instances, a watch and wait approach is often used, until the therapist is certain that the child does have ‘praxis’ issues (problems planning and implementing speech), rather than just delayed language development or other concerns.
MedicalResearch.com: What is the prognosis for these children? i.e. Do they go on to have regular schooling. What does life look like for a child with apraxia?
Response: Apraxia often co-occurs with other developmental challenges, such as body movement problems, learning challenges or ADHD. When apraxia occurs largely on its own, the prognosis is more positive. Children with apraxia typically attend mainstream schools. They need a lot of intensive speech therapy in the early to mid school years. Most children are largely intelligible by the teenage years but may have the persistence of some error patterns or may struggle with more complex words and phrases. Children with apraxia may also experience written (eg literacy) and spoken language problems, which have further impacts in the school environment.
MedicalResearch.com: What are the current treatments?
Response: Current therapies are only based on treating the speech errors, which we can think of as symptoms on the surface of the body. We have some therapies that work well, when applied intensively by the family and therapist working together.
MedicalResearch.com: What could possible future treatments look like and what kind of outcomes could that have for these children?
Response: Our research examines the underlying cause of apraxia. Why does apraxia occur? Changes, or mutations, in a number of genes have been linked to apraxia. Changes in genes are thought to lead to altered brain development of the brain pathways supporting speech. In our study, we found differences in the development of a particular language pathway in the brain that seems to have led to apraxia. This pathway is understood to link auditory (what we hear) information with movement information (how we move our articulators to produce speech). Into the future, pairing genetic and brain information will help develop more targeted therapies, eg., drug therapies to target the biological pathways disrupted by specific gene changes, trying to mitigate changes in brain development to prevent speech disorder.
Frédérique J Liégeois, Samantha J Turner, Angela Mayes, Alexandra F Bonthrone, Amber Boys, Libby Smith, Bronwyn Parry-Fielder, Simone Mandelstam, Megan Spencer-Smith, Melanie Bahlo, Tom S Scerri, Michael S Hildebrand, Ingrid E Scheffer, Alan Connelly, Angela T Morgan. Dorsal language stream anomalies in an inherited speech disorder. Brain, 2019; DOI: 10.1093/brain/awz018
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