Dysarthria is a motor speech disorder caused by problems with the muscles involved with speaking. These muscle problems typically arise from direct damage to the muscles or the central or peripheral nervous system that controls them. Dysarthria is characterized by difficulty speaking that results in slow or slurred speech. This leads to impairments in audibility, naturalness, intelligibility, and an individual’s efficiency of vocal communication.
Causes of Dysarthria
There are several underlying causes of dysarthria. Dysarthria can affect any of the subsystems of speech, including respiration, resonance, and articulation. The main causes of dysarthria include pathological diseases and traumatic injury. Dysarthria can also be caused by medications that involve the central nervous system. These medications include narcotics or sedatives such as phenytoin and carbamazepine.
Conditions that contribute to dysarthria include:
- Cerebral palsy
- Lyme disease
- Parkinson’s disease
- Huntington’s disease
- Neimann Pick disease
- Lou Gehrig’s disease
- Guillain-Barre syndrome
- Muscular dystrophy
- Myasthenia gravis
- Multiple sclerosis
- Wilson’s disease
- Brain tumors
- Tay-Sachs and Late Onset Tay-Sachs disease
- Alcohol or drug abuse
- Traumatic head or brain injury
- Intracranial hypertension
- Embolic or thrombotic stroke
Signs and Symptoms
Symptoms of dysarthria vary depending on the cause, and may involve:
- Monotone speech
- Slow or slurred speech
- Speaking at a whisper volume
- Rapid speech that may be difficult to understand
- Uneven speech rhythm or volume
- Raspy, nasal, or strained speech
- Difficulty moving the facial muscles or tongue
- Difficulty swallowing or chewing
Misdiagnosis of Dysarthria
Further damage can occur if the underlying dysarthria cause is undiagnosed, misdiagnosed, or improperly treated. Occasionally, dysarthria caused by an infection or reversible inflammatory disease can be treated successfully. If the condition is treated, the symptoms of dysarthria may resolve with no permanent muscular or neural damage. However, failure to promptly diagnose and treat the cause can lead to permanent dysarthria.
Diagnosis and Treatment
If a patient experiences any symptoms of dysarthria, testing should be performed immediately to diagnose the underlying cause. A medical professional may perform an MRI scan or CT scan to examine the brain via magnetic waves or computerized recordings. A PET scan may be used to determine the brain’s functional activity levels. A single-photon emission computed tomography (SPECT) scan can be used to reveal the amount of blood flow in the brain.
Blood and urine tests can also determine the cause of dysarthria. Blood and urine tests reveal infection or inflammatory disease. If necessary, a lumbar puncture, or spinal tap can be used to remove a sample of the cerebrospinal fluid for laboratory examination and testing. A spinal tap helps to diagnose central nervous system disorders, serious infections, and certain cancers.
Once the condition is diagnosed, appropriate treatment can begin. In some cases, dysarthria can be reversed or healed over time. Speech language pathology is the primary form of treatment for dysarthria. Speech language pathology involves exercises that strengthen the muscles to improve motor control. However, dysarthria caused by degenerative diseases such as multiple sclerosis or Lou Gehrig’s disease is typically incurable. This type of dysarthria worsens with time.