Dysarthria is a motor speech disorder caused by weakness, slowness, paralysis, or poor coordination of the muscles used for speaking. These include the muscles of the lips, tongue, jaw, throat, vocal folds, and the muscles that control breathing. Dysarthria happens when a neurological problem, such as damage to the brain or nerves, affects how the body controls these muscles. As a result, a child's speech may sound slurred, mumbled, slow, too soft, nasal, or hard to understand, even though the child knows exactly what they want to say. Dysarthria is a problem with the physical production of speech, not with language or intelligence.
What is dysarthria?
Talking is a complex motor task. To produce speech, the brain sends signals through the nervous system to dozens of muscles that must move with the right strength, speed, range of movement, and timing. In dysarthria, something interrupts this system. The muscles may be weak, stiff, floppy, or uncoordinated, so speech movements are slow, effortful, or imprecise. Put simply, dysarthria is a speech disorder caused by weakness or poor muscular control, not by a problem with thinking or language.
Dysarthria can affect every part of the speech system:
- Breathing (respiration): weak breath support can make the voice soft or cause a child to speak only a few words per breath.
- Voice (phonation): the voice may sound hoarse, breathy, strained, or monotone.
- Resonance: speech may sound too nasal because the soft palate does not close fully.
- Articulation: the lips, tongue, and jaw may not move precisely, so sounds come out blurred or distorted.
- Prosody: the rhythm, stress, and melody of speech may sound unusual, flat, or choppy.
Dysarthria can range from mild, where speech is a little unclear, to severe, where speech is very difficult for others to understand. The severity of dysarthria can also change with fatigue or illness.
Types of dysarthria
Speech-language pathologists often describe dysarthria by type, based on which part of the nervous system is affected and how speech sounds. Common types include:
- Spastic dysarthria: linked to damage in the upper motor neurons; speech may sound slow, strained, and effortful.
- Flaccid dysarthria: linked to damage in the lower motor neurons or cranial nerves; speech may sound breathy and nasal, with weak consonants.
- Ataxic dysarthria: linked to the cerebellum, which coordinates movement; speech may sound irregular, "scanning," or similar to slurred speech.
- Hypokinetic and hyperkinetic dysarthria: linked to the basal ganglia; hypokinetic dysarthria is the type most often associated with Parkinson's disease.
- Mixed dysarthria: a combination of two or more types, which is common in children with cerebral palsy or brain injury.
Causes of dysarthria in children
Dysarthria in children is caused by conditions that affect the brain, nerves, or muscles. It may be present from birth or early childhood (developmental) or appear after an injury or illness (acquired). Possible causes include:
- Cerebral palsy, one of the most common causes of dysarthria in children.
- Brain injury, including traumatic brain injury (TBI) from a fall, accident, or sports injury.
- Stroke, which can also happen in infants and children.
- Brain tumors or the effects of their treatment.
- Neuromuscular and genetic conditions, such as muscular dystrophy or some genetic syndromes.
In adults, dysarthria is often linked to stroke, Parkinson's disease, multiple sclerosis, ALS, and other neurological diseases. Only a doctor or medical team can determine the underlying cause for a specific child. Many children also have other needs, such as challenges with fine and gross motor skills or swallowing difficulties.
Dysarthria symptoms and signs
Dysarthria symptoms vary depending on the cause and type. Parents and teachers may notice that a child:
- has slurred or mumbled speech that sounds "blurry"
- speaks very slowly, or rapidly in short rushes
- has a very soft voice, or a voice that is too loud
- sounds nasal, hoarse, breathy, or strained
- runs out of breath while talking or pauses often
- drools or has trouble chewing and swallowing (called dysphagia)
- is understood by family but not by teachers or classmates
Speech errors in dysarthria tend to be fairly consistent, because the same muscle weakness affects speech every time. Speech is often harder to understand when the child is tired or in a noisy room.
Dysarthria vs apraxia vs dyspraxia
Dysarthria is often confused with apraxia of speech, but they are different motor speech disorders. In dysarthria, the muscles themselves are weak, slow, or poorly controlled. In childhood apraxia of speech (CAS), the muscles are not weak. Instead, the brain has trouble planning and sequencing the movements needed to say sounds and words. Children with apraxia often make inconsistent errors and have more trouble with longer words.
A simple way to remember the difference: dysarthria is a problem with muscle control, while apraxia is a problem with motor planning. A child can have both.
Dyspraxia, also called developmental coordination disorder, affects the planning and coordination of body movements more broadly, such as handwriting, sports, or getting dressed. The term "verbal dyspraxia" is sometimes used for apraxia of speech. Dysarthria is also different from dysphasia (aphasia) and other language disorders, such as an expressive language disorder, which affect choosing words and forming sentences rather than the physical act of speaking.
How dysarthria is diagnosed
A speech-language pathologist (SLP), sometimes called a speech therapist, evaluates dysarthria. The SLP looks at how the lips, tongue, and jaw move, listens to breathing, voice, and speech clarity, and checks how well others understand the child (called intelligibility). A doctor in neurology may be involved to find the medical cause.
Speech therapy for dysarthria and treatment options
Treatment options depend on the cause, type, and severity of dysarthria. Dysarthria speech therapy aims to improve speech clarity and communication and may focus on:
- slowing the rate of speech so words are clearer
- improving breath support for a louder, steadier voice
- making bigger, more precise mouth movements to speak more clearly
- exercises to strengthen muscles or improve coordination, when appropriate
- using strategies such as pausing between phrases
- teaching communication partners to reduce background noise, watch the speaker's face, and ask the child to repeat or rephrase
Some children also benefit from physical therapy or occupational therapy for posture, seating, and motor skills that affect breathing and speech. The SLP chooses specific therapy approaches based on evidence and on the child's needs.
AAC for children with dysarthria
When speech is very hard to understand, augmentative and alternative communication (AAC) can help. AAC includes gestures, sign language, picture boards, alphabet boards, and speech-generating devices. AAC does not stop a child from talking. It gives the child a reliable way to communicate while speech therapy continues, and according to ASHA, using AAC does not keep children from developing speech. AAC tools and devices can be written into a student's plan as assistive technology.
Dysarthria and school support
Under the Individuals with Disabilities Education Act (IDEA), a child with dysarthria may qualify for special education under the category speech or language impairment. IDEA defines this as a communication disorder, such as impaired articulation or a voice impairment, that adversely affects a child's educational performance (34 CFR 300.8(c)(11)). Depending on the cause, a child may instead qualify under another category, such as traumatic brain injury, orthopedic impairment, or multiple disabilities.
If a child qualifies, the team writes an IEP with speech therapy as a related service and goals for communication. Helpful supports may include:
- extra time to answer questions and give oral presentations
- preferential seating in a quieter part of the room
- access to AAC or a speech-generating device in all settings
A child who does not qualify under IDEA may still receive accommodations through a Section 504 plan.
Frequently asked questions about dysarthria
What is the main cause of dysarthria?
Dysarthria is caused by damage to the parts of the nervous system that control the speech muscles. In children, cerebral palsy and brain injury are common causes. In adults, stroke and conditions such as Parkinson's disease are common causes.
Will dysarthria go away?
It depends on the cause. Dysarthria after a brain injury may improve as the brain heals, while dysarthria linked to cerebral palsy is usually long-term. Speech therapy can still help many children communicate more effectively.
What is the difference between dysarthria and apraxia?
Dysarthria is caused by weak or poorly controlled speech muscles. Apraxia of speech is a problem with planning the movements for speech, while the muscles themselves are not weak. Errors in dysarthria tend to be consistent, while errors in apraxia are often inconsistent.
Does dysarthria affect intelligence?
No. Dysarthria affects how clearly a person can speak, not how well they think or understand. Some children with dysarthria have other learning needs, but unclear speech alone says nothing about a child's intelligence.
Is dysarthria a disability under IDEA?
Dysarthria can qualify a child for special education under the IDEA category of speech or language impairment if it adversely affects the child's educational performance and the child needs special education. The school evaluation team makes this decision.
