Childhood apraxia of speech: when the brain can’t plan the words
Talking is one of the most complex actions the human body performs, yet the process of turning thoughts into speech is coordinated on millisecond timescales. For some children, the brain struggles to plan the movements needed for speech, turning everyday conversation into hard work. Even forming a single word can affect learning, friendships and confidence.
UK guidance suggests around one in ten children experience some form of speech, language or communication difficulty, including speech sound disorders. These conditions can influence educational progress, emotional wellbeing and social development. Communication underpins not only learning, but also how children express feelings and connect with others.
As a speech scientist specialising in clinical phonetics and speech acquisition, I am currently researching a less common speech motor disorder: childhood apraxia of speech (CAS). This is a speech motor disorder, meaning the difficulty lies in the brain’s ability to plan and coordinate the movements needed to produce speech.
CAS is estimated to affect roughly one in 1,000 children, though figures vary. Many children improve with specialist speech and language therapy and regular practice. Without this support, speech difficulties are more likely to persist and some children may remain difficult to understand, even to close family members. Families and teachers also play an important role in reinforcing therapy and supporting everyday communication.
Understanding how speech is produced helps explain why these conditions occur and how they can be treated. Speech and language therapists receive extensive training in phonetics, the science of how speech sounds are created, transmitted and heard. Caregivers and teachers can also benefit from a basic understanding of just how complex speech production really is.
Moving parts
Producing even a single sound involves a carefully timed sequence of movements known as a speech motor plan, which the brain must assemble before the sound is spoken. For English speech, the lungs first generate a steady stream of air, usually by exhaling more slowly than during normal breathing.
As this air passes through the voice box, also called the larynx, it moves across the vocal folds. These small folds of tissue can behave in several ways. They can close tightly and release to produce a glottal stop, the brief catch in the throat heard in the middle of “uh-oh”. They can remain open so air flows through freely, creating voiceless sounds such as “s”. Or they can vibrate to produce “voicing”, the low buzzing sound you can feel in your throat when saying sounds like “z” or “b”. Each option depends on fine control of vocal fold position and tension.
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After leaving the larynx, air travels either through the mouth alone or through both the mouth and nose. This pathway is controlled by the velum, the soft part at the back of the roof of the mouth. The velum lifts to block the nasal passage when air needs to stay in the mouth. When air reaches the mouth, the articulators, including the tongue, lips and teeth, shape it into recognisable speech sounds by creating narrow gaps or brief closures.
Take the first sound in the word “sat”, the /s/ sound. The tip of the tongue moves close to the roof of the mouth just behind the upper teeth, forming a narrow channel. Air rushing through this gap creates friction, producing the familiar hissing sound. At the same time, the velum lifts to stop air entering the nose and the vocal folds stay open so the sound remains voiceless.
Small changes in timing or position can create entirely different sounds. If the vocal folds vibrate, the /z/ sound in “zoo” is produced instead of /s/. If the tongue presses fully against the roof of the mouth, the sound becomes /t/, as in “two”.
Speech becomes even more complex in words and sentences, where sounds overlap and influence each other. The shape of the lips for one sound may be adjusted in advance for the next. When saying “seat”, the lips spread wide, but in “soup” they round in anticipation of the following vowel. Real-time imaging of the vocal tract during speech, including MRI and ultrasound studies, shows how intricate and rapid these adjustments are.
Therapy can help
Because speech relies on so many coordinated actions, the brain must assemble detailed movement plans and send them to the muscles with precise timing. In speech motor disorders such as CAS, this planning process is disrupted. The result is speech that may sound inconsistent, effortful and difficult to understand, with words sometimes produced differently each time, even for people who know the child well.
Therapy grounded in motor skill learning principles has been shown to help some children practise and stabilise these movement patterns. Support may also include augmentative and alternative communication, which refers to tools and strategies that help children communicate while their speech skills develop. These can range from picture boards to speech generating devices.
No single approach fits every child, but progress is possible. Specialist therapy, classroom support and tools such as augmentative and alternative communication can all help. The goal is not perfection, but participation. Being able to share ideas, ask for help and connect with others is what matters most for a child’s development.
Nicole Whitworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.