The main clinical forms of dysarthria: comparative characterization

Depending on the types of movement disorders of the muscles of the articulatory apparatus that ensure the pronunciation of sounds, various forms of dysarthria are determined - a neurogenic speech disorder.

This neurological condition occurs due to insufficient innervation of the speech apparatus due to organic lesions of the premotor cortex, cerebellum or limbic-reticular structures of the brain, as well as diseases of the central nervous system and peripheral nervous system of cerebrovascular or neurodegenerative etiology.

Characteristics of forms of dysarthria

Each type of dysarthria - bulbar, pseudobulbar, cerebellar, cortical, extrapyramidal (subcortical) - leads to different forms of disruption of the muscular mechanism of speech and negatively affects the articulation of consonants, making speech inarticulate. And a severe form of dysarthria is manifested in the distortion of the pronunciation of vowels. In this case, speech intelligibility varies greatly depending on the degree of damage to the nervous system.

Regardless of the pathogenesis of speech neuromotor disorders, the characteristics of dysarthria forms take into account the anthropophonic features of speech, that is, the integration and coordination of the main physiological subsystems of sound reproduction. This is the conjugation of the movements of the muscles of the parts of the articulatory apparatus (tongue, lips, soft palate, jaws), that is, articulatory motor skills or articulatory patterns of sound reproduction; the nature of speech breathing; voice formation (the sound part of speech or phonation), which depends on the innervation of the muscles of the larynx and vibrations of the vocal folds.

Prosody (tempo, rhythm, intonation and volume of speech) is necessarily assessed, as well as resonance – the passage of the air stream through resonating cavities (oral, nasal and pharyngeal). Most clinical forms of dysarthria are characterized by nasality and hypernasality of speech (nasality), which are associated with a violation of the lowering/raising of the soft palate – the palatine-pharyngeal fibromuscular plate (velum palatinum) and the redirection of part of the air flow through the nasal cavity.

In domestic neurological practice, based on key symptoms, the following forms of dysarthria are distinguished:

• spastic form of dysarthria,
• spastic-paretic form of dysarthria (spastic-hyperkinetic),
• spastic-rigid form of dysarthria,
• ataxic form of dysarthria (or spastic-ataxic),
• mixed form of dysarthria,
• latent form of dysarthria.

When diagnosing speech disorders of a motor nature, Western specialists distinguish between spastic, flaccid, ataxic, hyperkinetic and hypokinetic forms of dysarthria.

For a better understanding of the terminology, it is worth recalling that spasticity means

Increased muscle tone with involuntary contraction; with muscle rigidity, the muscles are clamped and immobile; paresis is a partial paralysis, that is, a significant decrease in muscle strength due to pathologies in the transmission of nerve impulses; lack of coordination of movements of different muscles is called ataxia. If a person experiences unintentional movements for no apparent reason, then we are talking about hyperkinesis, and hypokinesia is characterized by a decrease in the speed of movements and their amplitude.

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Main disorders in various forms of dysarthria

Since speech impairment is part of the symptom complex of many neurogenic pathologies, the most important role is played by the differential characteristics of clinical forms of dysarthria, including the most complete assessment of such factors as the severity of decreased muscle tone and the degree of general and local manifestations.

Let's consider what are the main disorders in various forms of dysarthria

By neurologists and speech therapists during diagnostics.

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Spastic form of dysarthria

Spastic dysarthria, which occurs as a result of bilateral damage to the upper motor neurons, as well as damage to the corticobulbar pathways for transmitting nerve impulses, manifests itself as:

• weakness of the facial muscles and a decrease in the range of motion of the articulatory apparatus;
• spasticity and increased tone of facial muscles;
• protrusion (falling out) of the tongue;
• hyperactive gag reflex;
• slowing down the rate of speech;
• tension in the voice with an increase or decrease in its volume with a general monotony of speech;
• intermittent breathing when talking;
• hypernasality of pronunciation.

People with spastic dysarthria produce slurred sounds and usually speak in short sentences; they often have difficulty swallowing (dysphagia).

The most common causes of spastic dysarthria are spastic paralysis, multiple sclerosis, amyotrophic lateral sclerosis (Charcot's disease or Lou Gehrig's disease), and closed craniocerebral injuries.

Spastic-rigid form of dysarthria

Damage to the basal ganglia results in a spastic-rigid form of dysarthria, usually associated with Parkinson's disease.

Speech problems with this form of dysarthria arise from tremors and lack of coordination of the speech muscles and include:

• impaired voice production (hoarseness, decreased volume);
• resonance in the nose (nasality);
• variable speech rate (sometimes slow, sometimes fast);
• violation of voice modulation and monotony of speech (dysprosody);
• stretching out syllables, compulsively repeating syllables and words (palilalia), or repeating heard sounds or words (echolalia);
• long pauses and difficulty starting a conversation.

In general, experts call the inaccuracy of pronunciation of sounds in this form of dysarthria “articulatory undershoot.”

Spastic-paretic form of dysarthria

With weakness of some muscles of the speech apparatus, associated with a disruption in the conduction of nerve impulses from the basal nuclei of the extrapyramidal system and paresis of muscle fibers, the spastic-paretic form of dysarthria (and the identical hyperkinetic form) is characterized by a general increased muscle tone, which is often accompanied by involuntary muscle movements, including facial movements.

The main disorders in this form of dysarthria are:

• tension, intermittency and vibration of the voice;
• dyskinesia at the level of the vocal cords and convulsive dysphonia (suppressed voice due to incomplete closure of the cords);
• frequent and noisy speech breathing;
• spasticity of the tongue (“the tongue does not move well in the mouth”);
• difficulty closing the lips, causing the mouth to remain open (with drooling);
• change in the tempo and rhythmic features of speech (significant slowing);
• pronounced nasal quality;
• absence of changes in the tone of speech (due to increased tension of the pharyngeal-laryngeal muscles).

Ataxic form of dysarthria (spastic-ataxic)

The pathogenesis of ataxic dysarthria is associated with damage to the cerebellum or its connection to the cortex and/or brainstem. Among the differential characteristics of this form of dysarthria, prosody and articulation disorders are particularly noted.

Thus, the volume of speech is sometimes described as explosive, despite its slow tempo, the stretching of syllables and individual sounds, and pauses after almost every word. Patients with ataxic dysarthria - with inaccuracy in the range, force, and direction of articulatory movements even when producing vowel sounds - speak especially indistinctly.

Given the unstable position of the head and the general lack of coordination of movements, a person suffering from ataxia can easily be mistaken for being drunk.

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Mixed form of dysarthria

In cases of paresis or paralysis of the muscles of the articulatory apparatus due to simultaneous damage to two or more motor neurons of the central nervous system - as occurs in multiple and lateral amyotrophic sclerosis or severe brain injuries - a mixed form of dysarthria is diagnosed. In essence, this is a combination of various symptoms of the erased form of spastic dysarthria and ataxic.

The characteristics of speech pathology will vary depending on which motor neurons are less affected – upper (located in the lower quarter of the premotor cortex of the cerebral hemispheres) or lower (their location is the anterior horns of the spinal cord). For example, if the upper motor neurons are most damaged, the voice formation disorder will be expressed in a decrease in timbre, and when the lower motor neurons are more affected, the voice will be hoarse with stridor during breathing.

Absent form of dysarthria

A flaccid or erased form of dysarthria or flaccid is caused by the degree of damage to the trigeminal, facial, vagus and hypoglossal cranial nerves (respectively - V, VII, X and XII), since they are responsible for the innervation of the muscles of the tongue, lips, palate, lower jaw, larynx, vocal cords and folds. If the local lesion affected only cranial nerve VII, then the orbicularis oris muscle will weaken, and if, in addition, the V pair of nerves is damaged, the muscle that raises the upper lip will be paralyzed.

Forms of dysarthria in cerebral palsy

Speech dysfunction in children occurs with a fairly large number of congenital anomalies of the brain and neurocognitive disabilities of various genesis. And cerebral palsy is the most common cause of speech disorders, which are characterized by the lack of stability, coordination and precision of movements of the muscles of the speech apparatus with varying degrees of narrowing of their range.

The following main forms of dysarthria in cerebral palsy are noted: spastic and its varieties - spastic-paretic and spastic-rigid, as well as a mixed form of dysarthria (which, along with spastic, is the most common).

Swallowing disorder (dysphagia) is a direct indication of a disturbance in the conduction of signals along the trigeminal nerve, which is also manifested by a decrease in the tone of the muscles of the entire face and lips with characteristic signs: an open mouth and salivation. And due to paralysis of the hypoglossal nerve in cerebral palsy, deviation of the tongue (deviation of its tip) occurs on the side of the body opposite the cerebral lesion.

Spastic dysarthria in cerebral palsy with spastic hemiplegia (unilateral paralysis) is associated with partial dysfunction of the hypoglossal cranial nerve, which is expressed in decreased tone of the facial (chewing and facial) muscles. In such cases, a latent form of dysarthria of the spastic-paretic type is diagnosed with an increased range of motion of the lower jaw, retrusion of the lower lip, tremor of the tongue, flaccidity of the vocal cords and weakness of the palate and pharynx. Together, this causes a persistent violation of the articulatory patterns of most consonants and inarticulate speech. Moreover, with left-sided hemiplegia, a milder form of dysarthria is noted than with right-sided hemiplegia.

Most patients with cerebral palsy are characterized by monotony and nasality of speech with stridor. The respiratory muscles may be affected, which leads to limited respiratory support of speech and phonation disorders. Due to the weakness of the chest muscles in the athetoid type of cerebral palsy, there is a forced contraction of the diaphragm, so it is difficult for the patient to regulate the strength and volume of the voice, and often all voiced consonants are deafened.

Articulatory dysfunctions of this form of dysarthria in cerebral palsy, such as spastic-rigid, are determined by the tense state of all facial muscles, sensory insufficiency of the chin and lips, and significant limitation of the mobility of the tongue and vocal folds.

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