Dysarthria (articulation disorder): causes, symptoms, diagnosis

With dysarthria, unlike aphasia, the "technique" of speech suffers, and not its higher (practical) functions. With dysarthria, despite pronunciation defects, the patient understands what is heard and written, and logically expresses his thoughts.

Thus, dysarthria is a disorder of the articulation process, the causes of which may be the following disorders of the speech muscles:

1. Paresis (peripheral and/or central);
2. Spasm or increased tone (tetany, rigidity, spasticity, stiffness);
3. Hyperkinesis;
4. Ataxia;
5. Hypokinesia (akinesia);
6. A combination of several of the above reasons;
7. Pseudoparesis.

In this regard, the following syndromic forms of dysarthria are distinguished: bulbar and pseudobulbar, extrapyramidal (hypokinetic and hyperkinetic), cerebellar, cortical and dysarthria associated with pathology at the muscular level. There is also psychogenic dysarthria.

There are diseases in which dysarthria may be caused by several of the above-mentioned reasons (for example, olivo-ponto-cerebellar atrophy, multiple sclerosis and other diseases).

"Paretic" dysarthria develops with damage to the lower motor neuron and is observed in the picture of bulbar paralysis. This dysarthria is caused by damage to the motor neurons of the medulla oblongata and the lower parts of the pons, as well as their intracerebral and peripheral axons. A characteristic "slurring" of speech ("mush in the mouth") develops, the pronunciation of the vibrating sound "R" is impaired, as well as lingual and labial sounds. With bilateral weakness of the soft palate, a nasal tone of the voice appears. The voice may also suffer due to paresis of the vocal cords.

Diplegia of the facial nerves in some polyneuropathies leads to weakness of the labial muscles and impaired pronunciation of labial sounds (“B”, “M”, “P”).

The neurological status reveals atrophy and fasciculations in the tongue, weakness of the soft palate and facial muscles.

The main causes of dysarthria (articulation disorders):polyneuropathy (diphtheria, AIDP, hyperthyroidism, porphyria, paraneoplastic polyneuropathy), amyotrophic lateral sclerosis, syringobulbia. Dysarthria in other motor neuron diseases, myasthenia, and rare forms of myopathy can also be included in this group. Transient dysarthria of this type is possible in the picture of transient ischemic attacks or as an early symptom of brainstem ischemia in stenosis of the basilar or vertebral arteries. All these diseases are accompanied by other neurological symptoms that facilitate diagnosis.

"Spastic" dysarthria develops with damage to the upper motor neuron and is part of the picture of pseudobulbar paralysis (with bilateral damage to the corticobulbar tracts). The most common cause: bilateral cerebral infarctions, high form of lateral amyotrophic syndrome.

"Atactic" dysarthria can be observed in acute and chronic diseases of the nervous system, accompanied by damage to the cerebellum (multiple sclerosis, traumatic brain injury, etc.) or its connections (spinocerebellar degeneration).

“Hypokinetic” dysarthria is characteristic of parkinsonism and, above all, of Parkinson’s disease, as its most common form.

“Hyperkinetic” dysarthria is typical for diseases that manifest as hyperkinesias (especially in the presence of choreic or dystonic syndromes, less often - tremor and other dyskinesias).

The “mixed” type of dysarthria develops when several brain systems involved in the regulation of motor (speech) functions are involved in the pathological process: multiple sclerosis, Wilson-Konovalov disease, ALS and other diseases.

Above is a purely clinical classification of dysarthria, based on the identification of the leading neurological syndrome underlying dysarthria. Below is another rubrication of the same variants of dysarthria, based on the distinction of all dysarthria into "peripheral" and "central" forms.

Dysarthria - as a symptom of damage to different levels of the nervous system

I. Peripheral dysarthria

1. “Diffuse”: polyneuropathy, myopathy, myasthenia gravis
2. "Focal" (with isolated damage to individual caudal cranial nerves)

II. Central dysarthria

A. Associated with damage to individual brain systems

1. Spastic (Pseudobulbar syndrome)
2. Ataxic (Cerebellar system damage)
3. Hypokinetic (Parkinsonism syndrome)
4. Hyperkinetic (chorea, dystonia, tremor, myoclonus)

B. Associated with combined damage to several brain systems

1. Spastic-paretic (ALS)
2. Spastic-ataxic (multiple sclerosis)
3. Other combinations

III. Psychogenic dysarthria. This form most often manifests itself in the form of pseudo-stuttering and is accompanied by other psychogenic motor, sensory and psycho-vegetative disorders.

Dysarthria as an early symptom of neurological diseases

• Brainstem ischemia due to stenosis of the basilar or vertebral artery
• Amyotrophic lateral sclerosis
• Multiple sclerosis
• Myasthenia
• Spinocerebellar degenerations
• Syringobulbia
• Progressive paralysis
• Wilson-Konovalov disease.

Dysarthria as a side effect of drugs (iatrogenic):

• androgens, anabolics
• neuroleptics
• barbiturates
• lithium
• L-dopa
• diphenin
• hexamidine
• Cytarabine (a drug used to treat cancer)
• cerucal
• kanamycin (antibacterial substance)

The cause of dysarthria is identified mainly taking into account its clinical features and based on the analysis of the accompanying subjective (patient complaints) and objective neurological symptoms ("syndromic environment"). Tests are used to detect myasthenia, hypokinesia, dystonia; EMG, EP, neuroimaging and other methods are used as indicated.

Paroxysmal dysarthria may sometimes be seen in multiple sclerosis.

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