Dysarthria: causes, symptoms, types and treatment
Communication disorders include disorders such as dyslalia, stuttering and the phonological disorder, better known as dysarthria . The basic sign that leads to the diagnosis of dysarthria is the presence of a marked difficulty to articulate phonemes adequately because of muscular problems.
In this article we will describe the causes and symptoms of the main types of dysarthria . In addition we will explain in a synthetic way what are the most common treatments of this disorder.
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What is dysarthria?
Dysarthria is a disorder that affects the speech muscles : the lips, the tongue, the vocal cords and / or the diaphragm. The difficulty in controlling these muscles or their weakness means that people with dysarthria can not articulate the phonemes correctly, so they have problems with pronunciation or speak more slowly than normal. Unlike motor aphasia, it is an alteration of pronunciation and not language.
The term "dysarthria" comes from the Greek and can be translated literally "articulatory malfunction". It is a speech disorder and not language; This means that the problem does not take place at the cognitive level but in later phases of the production of sound. When the person is completely incapable of articulating sounds we speak of anartria.
The DSM-IV collects dysarthria under the label "Phonological disorder" , while in the DSM-5 it is called "Speech sounds disorder". The basic criterion for diagnosis according to these classifications is that the person is unable to emit phonemes that would be expected to 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, as lesions and tumors in the brain or embolisms that paralyze the face or tongue. When it occurs from birth is usually the result 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 Parkinson, Huntington and Wilson. Some drugs can also cause dysarthria, especially sedatives and potent narcotics ; in these cases the interruption of consumption alleviates the disorder.
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Symptoms and signs
The symptoms and signs of this disorder may 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.
- Disturbed timbre.
- Speak too slow or fast.
- Nasal or raspy voice .
- Excessively high or low volume.
- Irregular rhythm (for example, choppy speech).
- Associated respiratory difficulties.
In relation to pronunciation difficulties, four types of main errors are usually detected: substitution, omission, insertion and distortion . The substitution, consisting of replacing the correct phoneme with another wrong one, is the most frequent, especially when pronouncing "d" or "g" instead of "r".
While the consonant articulation is affected in all cases of dysarthria, the inadequate pronunciation of vowels is considered an indicator of seriousness .
Types of dysarthria
The types of dysarthria that we will see in this section differ among them mainly in the location of the lesion at the level of the central nervous system.
Spastic dysarthria is due to injuries 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 speech volume occur. Vocalization tends to be tense and forced.
Lesions in the cerebellum cause ataxic dysarthria, whose most characteristic signs are presence of flat, monotonous prosody and slow vocalization and uncoordinated, similar to that which occurs in the state of intoxication. The typical speech of this type of dysarthria has sometimes been described as "explosive".
In this type of dysarthria the vagus nerve is affected , which allows the movement of the larynx and therefore the vocal cords. There are also dysfunctions in other facial muscles.
In cases of flaccid dysarthria the muscles may atrophy or become partially paralyzed, causing spasms, drooling and muscle tension.
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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 the spastic: the voice tends to present a rough quality and Hypernasality also occurs .
In general, hypokinetic dysarthria appears as a result of Parkinson's disease , although it is also common for the cause to be the continued use of antipsychotic medications.
In this case the volume is usually very low, the timbre flat and monotonous prosody. The reduction in the speed of movements caused by damage in the region known as substantia nigra explains these symptoms.
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 they are due to affectations in different motor systems .
Treatment and intervention
The treatment of dysarthria depends to a large extent on the alteration caused by the disorder since, when possible, correct the ultimate cause eliminates the symptoms . However, there are interventions to improve speech in cases where the underlying problem can not be modified.
The main objectives of the speech therapy and language therapy In cases of dysarthria, they are to strengthen the muscles involved in speech, improve breathing, achieve adequate pronunciation and facilitate communication between the affected person and their close relatives.
In cases where speech impairment is severe, external supports such as voice synthesizers and alphabetic boards are very useful. Learning gestures and even sign language it can also serve to a certain extent to supply the communicative deficits of dysarthria.