What Is Dysarthria?
Dysarthria is a motor speech disorder resulting from brain or nerve damage that impacts the muscles in the face, tongue, voice box (larynx), and jaw. This can result in speech that is slurred, soft, strained, or difficult for others to understand ¹. While people with dysarthria fully comprehend language and know what they want to say, muscle weakness or incoordination makes producing clear speech difficult ².
Dysarthria affects both children and adults and falls into two main categories:
- Developmental dysarthria Occurs due to brain damage prior to or during birth, such as from cerebral palsy ². While typically diagnosed in childhood, it continues into adulthood.
- Acquired dysarthria : Occurs due to neurological damage later in life caused by events like stroke, traumatic brain injury (TBI), brain tumors, or progressive conditions like Parkinson’s disease ³. This is more commonly seen in adults, but can occur in children.
Types of Dysarthria
There are six primary types of dysarthria, classified by how the speech sounds and the underlying neurological cause:
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Flaccid
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Spastic
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Ataxic
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Hypokinetic
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Hyperkinetic
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Mixed
Other forms include unilateral upper motor-neuron dysarthria and undetermined dysarthria (when symptoms fit dysarthria but do not cleanly match a single category)¹.
Common Causes of Dysarthria
Dysarthria arises from damage to the brain or nervous system, and commonly occurs in certain neurological conditions. Because these conditions often affect broader brain function, dysarthria can occur alongside language disorders like aphasia (difficulty processing language) or apraxia (difficulty planning motor movements for speech).
Some common causes of dysarthria include:
- Stroke: A leading cause that affects the brain’s ability to direct speech muscles. Read more about speech problems after a stroke.
- Neurological Diseases: Conditions like Parkinson’s disease, Motor Neuron Disease (MND/ALS), Multiple Sclerosis (MS), and cerebral palsy ¹,³.
- Brain Injury: Physical trauma that disrupts speech control pathways.
- Tumors or Infections: Lesions or inflammation affecting key neurological speech centers.
Symptoms of Dysarthria
The primary symptom of dysarthria is difficulty speaking clearly. Other symptoms may include:
- Slurred speech or mumbling
- Speaking too fast or too slowly
- Voice issues such as hoarseness, harshness, or breathiness
- Inconsistent pitch or volume ⁴
- Short, choppy sentences instead of fluent speech
Additionally, muscle control issues may affect swallowing (dysphagia) ², making it difficult to chew or swallow food properly.
How Dysarthria Is Diagnosed
Diagnosis requires a formal medical and speech evaluation, typically involving:
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Case History: Reviewing medical history to uncover the underlying cause.
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Diagnostic Imaging: MRIs, CT scans, or EEGs to pinpoint areas of brain or nerve damage.
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Physical & Neurological Exams: Assessing overall muscle tone and cranial nerve function.
- Speech-language Assessments by a speech pathologist to determine the severity, impacted nerves and muscles, and type of dysarthria ⁵.
