Dysarthria and Apraxia: Motor Speech Disorders Explained

Updated: Jul 31, 2020

What are motor speech disorders?

There are two primary motor speech disorders: apraxia and dysarthria of speech. Both conditions can occur in children and adults, and people with motor speech disorders can have both apraxia and dysarthria at the same time. Speech therapy can help.

Motor speech disorders involve a disconnection between the brain and physical speech mechanisms. People with motor speech disorders have difficulty controlling or coordinating the muscles that are used for speaking. These muscles are located in the face, larynx and tongue. Both dysarthria and apraxia may be associated with a variety of conditions including:

  • Cerebral palsy

  • Muscular dystrophy

  • Multiple sclerosis

  • Parkinson's disease

  • Myasthenia gravis

  • Huntington's disease

  • Brain tumors

  • Dementia

  • Traumatic brain injury

  • Stroke

What is dysarthria?

Dysarthria is a type of motor speech disorder that is caused by muscle weakness. People with dysarthria often find it physically difficult to speak, and their speech may be difficult for others to understand.

Dysarthria is typically associated with muscle weakness caused by brain damage. It may be mild or severe.

Other speech and language problems may also involve dysarthria. An SLP or speech pathologist can provide helpful treatment for dysarthria.

What is apraxia?

Apraxia is a motor speech disorder that is caused by brain damage. To understand apraxia, you must first understand the connection between the brain and speech.

Whenever you speak, messages are transmitted from your brain to your mouth. These messages signal each muscle involved in speech formation, telling the muscles when and how to move in order to form specific sounds. When someone has apraxia, those messages are not clear. There are two main types of apraxia:

  • Acquired apraxia involves the impairment or loss of existing speech skills.

  • Developmental apraxia, which is also known as childhood apraxia of speech is present at birth.

There are different levels of severity, too. Some people with apraxia cannot speak it all; others have difficulty moving their tongue and/or lips to form specific sounds. A speech pathologist can help.

Related: 10 Repetitive Books for Children with Apraxia of Speech

What causes motor speech disorders?

Motor speech disorders are caused when neurologic damage affects the mechanisms that allow a person to speak. It's very important to note here that motor speech disorders do not affect cognition which is the ability to come up with thoughts to share with the world.

Motor speech disorders are specific in that they affect the ability of speech generating organs including the lips, tongue, and throat to work together.

According to the Mayo Clinic, 54% of people with motor speech disorders have dysarthria caused by a breakdown in communication between the brain and muscles associated with speech.

  • Another 25% of people with motor speech disorders have aphasia, which is a language disorder that often goes hand in hand with motor speech disorders.

  • Cognitive-language disorders including amnesia, dementia, and traumatic brain injury make up another 16%.

  • A relatively small 4% of motor speech disorders involve apraxia caused by difficulty with programming and motor planning. This can lead to the wrong sounds or words coming out, or to speech that sounds flat and robotic.

  • The final 1% of people with motor speech disorders are also affected by other neurogenic speech issues including stuttering, mutism, and others.

Different forms of dysarthria

The type of dysarthria a person has depends on the type of neurologic damage.

Flaccid type dysarthria is associated with muscle weakness. The person's speech may sound breathy or nasally. The volume and pitch of their speech often does not change, and they may have a tendency to speak in short phrases. Due to the muscle weakness involved in this type of dysarthria, the person is likely to tire quickly after speaking.

Spastic type dysarthria involves muscles that are too tight. The person's voice might sound harsh, and they may be nasally as well. Speech may be slow or strained, and the person may speak at a low pitch that does not change much.

Apraxia of speech occurs when a person has difficulty coordinating the sounds that make up speech. In apraxia, people may sometimes form words correctly and then later have difficulty forming those same words the right way. There is often no rhyme or reason to apraxia, however speech might sound slurred or robotic even when the correct speech sounds are made.

How do you diagnose motor speech disorders?

Motor speech disorders may be diagnosed by a doctor or by a speech language pathologist who can test speech and language to determine why the individual is having trouble speaking.

During testing, the SLP will listen to the way you speak and watch the mouth, lips, and tongue as they form the sounds that make up speech.

The testing process covers individual words and sentences, as well as conversation. In addition, speech language pathologists test the individual's ability to put their thoughts into words and understand what others are saying.

Diagnosing motor speech disorders in children

Childhood motor speech disorders are sometimes diagnosed between the ages of 18 months into years of age, although later diagnoses are common. Children with motor speech disorders might be able to form only a few different sounds or words, and they might have difficulty separating syllables or words. Many children with motor speech disorders have difficulty imitating words as well.

Childhood motor speech disorders

Also known as CAS, childhood apraxia of speech is a motor speech disorder in which a child's brain has difficulty directing or coordinating speech movement. This leads to inaccurate movements when speaking.

CAS occurs for different reasons. Sometimes it is the results of a brain condition or injury such as an infection, traumatic brain injury, or stroke. Sometimes childhood apraxia of speech is associated with a metabolic condition or genetic disorder. CAS often occurs in children with galactosemia. Children with speech apraxia often do not have the same muscle weakness exhibited by adults; even so, the muscles do not perform normally.

CAS can be treated with speech therapy. During treatment, the focus is on teaching the child's brain to plan for moving speech muscles in the jaw, lips, and tongue.

How do you treat motor speech disorders?

The treatment for motor speech disorders varies depending on whether dysarthria or apraxia is involved. Individuals with dysarthria and apraxia may receive a variety of different treatments for their motor speech disorders, usually with the help of a speech pathologist.

Treatments for apraxia focus on improving sound sequencing and coordination. People with apraxia can also benefit from sensory treatments aimed at improving awareness of how it looks and feels to produce different sounds.

Treatments for dysarthria focus on strengthening muscles used to produce speech. Dysarthria treatments might also involve exercises aimed at increasing vocal and respiratory support for the production of speech as well as exercises designed to make speech more precise. Some dysarthria treatments help people change their rate of speech.

If you are treated for dysarthria, you might focus on:

  • Slowing your rate of speech

  • Strengthening your mouth muscles

  • Increasing the amount of breath you use when you speak, which can help you speak louder

  • Making sounds clearly as you say different words

  • Moving the muscles that control your tongue and lips more

  • Using other forms of communication, also known as augmentative and alternative communication or AAC

Treating motor speech disorders in children involves speech therapy as well. A child with CAS typically works alongside a speech language pathologist, learning and practicing the correct way to say different syllables, words, and phrases, as well as practicing movements that form accurate sounds and words.

In children and adults alike, treatment for motor speech disorders often focuses on speaking at a normal speed, using a normal rhythm that is easier for listeners to understand.

Tips for interacting with people who have motor speech disorders   

Because it can be difficult to understand people who have motor speech disorders, it is important to pay careful attention when they are speaking. Here are some additional tips for interacting with people who have dyspraxia and/or apraxia.

  • If possible, choose a quiet setting where you can hear what is being said.

  • Watch as the person is speaking. Having good lighting can help.

  • Do not pretend to understand what is being said if you don't understand. Let the person know if you're having difficulty understanding, so that they can make themselves clear.

  • If you understood part of what was being said, repeat the part you understood and ask for clarification on the part you didn't understand. This way, the person is not forced to repeat themselves completely.

  • When you still have trouble understanding, consider asking yes or no questions that can help clarify the person's message. You might also ask the person to clarify by writing or pointing. Some people with dysarthria are able to communicate using gestures or computers as well.

Find speech therapy near me!

Consistent therapy with a speech pathologist can make all the difference for people with motor speech disorders. It is often possible to re-learn speech skills after the brain has been damaged. In addition, children with CAS can often learn better speech and language skills, resulting in improved communication.

Speech language pathology experts might be available through referral from your doctor. There is another option, however, which is particularly convenient when local help is difficult to find. Online speech therapy is available everywhere through Better Speech.

Ready to learn more about online speech therapy? Offering licensed, accredited, experienced, speech therapists on your schedule, Better Speech offers professional help for people with motor speech disorders and more. Contact us today to see how we can help.

FAQ on motor speech disorders

What are some causes of neurogenic motor speech disorders?

There are many causes of neurogenic motor speech disorders including:

  • Muscle weakness

  • Muscles that are too tight

  • Difficulty with motor planning

  • Dementia

  • Traumatic brain injury

  • Stroke

  • Other neurologic traumas and diseases such as Parkinson's, Myasthenia gravis, and Multiple sclerosis.

What are acquired motor speech disorders?

Acquired motor speech disorders are voice and speech changes that are directly associated with damage to the central nervous system and/or the peripheral nervous system. Acquired motor speech disorders may happen suddenly – for example, after a stroke – or gradually. They may be minor or so severe that the affected person loses their ability to speak completely.

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