Dysarthria: causes, symptoms, types and treatment

Communication disorders include disorders such as dyslalia, stuttering and phonological disorder, better known as dysarthria. The basic sign that leads to the diagnosis of dysarthria is the presence of marked difficulty in articulating phonemes properly due to muscle problems.

In this article we will describe the causes and symptoms of the main types of dysarthria. We will also explain in a synthetic way what the most common treatments for this disorder consist of.

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What is dysarthria?

Dysarthria is a disorder that affects speech muscles: the lips, the tongue, the vocal cords and / or the diaphragm. Difficulty controlling these muscles or their weakness makes people with dysarthria unable to articulate phonemes correctly, so they have pronunciation problems or speak more slowly than usual. normal. Unlike the motor aphasia, is an alteration of the pronunciation and not of the language.

The term "dysarthria" comes from the Greek and can be literally translated "articulatory malfunction." It is a speech disorder and not a language disorder; this means that the problem does not occur at the cognitive level but in later stages of sound production. When the person is completely unable to articulate sounds, we speak of anarthria.

The DSM-IV lists dysarthria under the label "Phonological disorder", whereas in the DSM-5 it is called "Disorder of the sounds of the speech". The basic criterion for the diagnosis according to these classifications is that the person is incapable of emitting phonemes that it would be expected that they would have learned to articulate at a certain age.

Causes of this disorder

Dysarthria can have many different causes. Among the most common are alterations of the nervous system, such as lesions and tumors in the brain or emboli that paralyze the face or tongue. When it occurs from birth, it is usually a consequence of cerebral palsy or muscular dystrophy.

Certain alterations favor the appearance of symptoms of dysarthria in adulthood, such as amyotrophic lateral sclerosis or diseases of the Parkinson's, Huntington and Wilson. Some drugs can also cause dysarthria, especially strong sedatives and narcotics; in these cases the interruption of the consumption alleviates the disorder.

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Symptoms and signs

The symptoms and signs of this disorder can vary depending on the cause and type of dysarthria. Among the most common we find the following:

• Difficulty moving the muscles of the face, lips, and tongue.
• Bad pronunciation.
• Monotonous prosody.
• Altered timbre.
• Speak too slow or fast.
• Nasal or hoarse voice.
• Excessively high or low volume.
• Irregular rhythm (for example, broken speech).
• Associated breathing difficulties.

In relation to pronunciation difficulties, four main types of errors are usually detected: substitution, omission, insertion and distortion. Substitution, consisting of replacing the correct phoneme with an incorrect one, is the most frequent, especially when pronouncing “d” or “g” instead of “r”.

While consonant articulation is affected in all cases of dysarthria, improper vowel pronunciation is considered an indicator of severity.

Types of dysarthria

The types of dysarthria that we will see in this section differ between them mainly in the location of the lesion at the level of the central nervous system.

1. Spastic

Spastic dysarthria is due to lesions in the pyramidal tracts, related to fine motor control of the muscles of the face and neck.

In this type of dysphasia, hypernasality and sudden increases in the volume of speech occur. Vocalization tends to be strained and strained.

2. Ataxic

Injuries to the cerebellum cause ataxic dysarthria, the most characteristic signs of which are presence of flat, monotonous prosody and slow vocalization and uncoordinated, similar to that which occurs in a drunken state. The typical speech of this type of dysarthria has sometimes been described as "explosive".

3. Flaccid

In this type of dysarthria the vagus nerve is affected, which allows movement of the larynx and therefore of the vocal cords. Dysfunctions also occur in other facial muscles.

In flaccid dysarthria the muscles can atrophy or partially paralyze, causing spasms, drooling and muscle tension.

• Related article: "Cranial Nerves: The 12 Nerves Leaving the Brain"

4. Hyperkinetics

Hyperkinetic dysarthria is usually caused by lesions in the basal ganglia, subcortical structures involved in involuntary movements.

The symptoms of this type of dysarthria are similar to those of spasticity: the voice tends to have a harsh quality and hypernasality also occurs.

5. Hypokinetic

Hypokinetic dysarthria in general appears as a consequence of Parkinson's disease, although it is also common for the cause to be the continued use of medications antipsychotics.

In this case the volume is usually very low, the timbre flat and the prosody monotonous. The reduction in the speed of movements caused by damage in the region known as the substantia nigra explains these symptoms.

6. Mixed

This category is used when the clinical features are a combination of more than one of the types of dysarthria that we have described. Mixed dysarthria are due to affectations in different motor systems.

Treatment and intervention

The treatment of dysarthria depends to a large extent on the alteration that causes the disorder since, when possible, correcting the ultimate cause eliminates the symptoms. However, there are interventions to improve speech in cases where the underlying problem cannot be changed.

The main objectives of the speech therapy and speech therapy in cases of dysarthria are to strengthen the muscles involved in speech, improve breathing, achieve proper pronunciation and facilitate communication between the affected person and their loved ones close.

In cases where speech impairment is severe, external aids, such as voice synthesizers and alphabet boards, are very useful. Learning gestures and even sign language It can also serve to some extent to make up for the communication deficits typical of dysarthria.