DYSARTHRIA

Dysarthria pertains to a category of neurogenic speech disorders distinguished by an anomaly in the strength, speed, availability, stableness, tone, or accuracy of movements necessary for breathing, phonatory, resonatory, articulatory, or prosodic features of speech creation.

These anomalies are the result of one or several sensorimotor issues, including weakness or paralysis, incoordination, involuntary movements, or immoderate, declined, or inconstant muscle tone. Dysarthria can negatively impact the comprehensibility of speech, realism of speech, or both. It is necessary to be aware that intelligence can be normal in some speakers with dysarthria. Dysarthria might co-exist with other neurogenic language, cognitive, and swallowing disorders.

Dysarthria is caused by muscle weakness or the inability to control the muscles related to speech. Speech appears slurred or unintelligible to the listener. Dysarthria can mildly affect the way speech is understood or it can be quite severe, making it difficult to understand one’s speech.

Dysarthria can also impact the coordination of movement that involves respiration, phonation, resonance, and prosody. These are all components that contribute to the way that one speaks and communicates oral messages.

· Respiration - the air we breathe in and out; the power for speech production

· Phonation - the air we produce that vibrates the vocal cords

· Resonance - the air shaped by the oral and nasal cavities

· Prosody - the rhythm and intonation of speech

Mechanism of Injury / Pathological Process

Damage to the nervous system causes hypotonicity in the muscles that create speech sounds. This may impact the muscles in one or several of the following areas:

· Face

· Lips

· Tongue

· Throat

· Upper respiratory tract

Types of Dysarthria

Depending on the location of the neurological damage different types of dysarthria have been described;

· Flaccid: affiliated with conditions of the lower motor neuron system and/or muscle, for instance damage to the peripheral nervous system (PNS). Hallmarked by difficulty pronouncing consonants.

· Spastic: affiliated with bilateral illnesses of the upper motor neuron system. Patients may have speech issues alongside muscle weakness and abnormal reflexes.

· Ataxic: affiliated with conditions of the cerebellar control unit. Symptoms of slurred speech and lack of coordination.

· Hypokinetic: affiliated with infirmity of the basal ganglia control unit, such as insult caused by neurodegenerative diseases, such as Parkinson’s and Huntington’s. Presents as quiet, breathy, or monotone voice, difficulty initiating sentences, a stutter or slurred speech, struggles pronouncing consonants, rigidity or lacked movement in the face and neck, swallow difficulty that can result in drooling and tremors or muscle spasms.

· Hyperkinetic: affiliated with ailment of the basal ganglia control unit. Symptoms include slurred or slow speech, shaky voice, shortness of breath or fatigue while speaking, muscle spasms and tremors, involuntary twitchy or flailing movements or atypical muscle tone.

· Unilateral upper motor neuron: affiliated with unilateral disorders of the upper motor neuron system

· Mixed: variety blend of dysarthria types (for example spastic-ataxic; flaccid-spastic)

· Undetermined: observed features are in line with a dysarthria but do not clearly place into any of the identified dysarthria types.

Signs of Dysarthria

If you have dysarthria you may:

• Have "slurred" or "mumbled" speech that can be hard to understand.
• Speak slowly.
• Talk too fast.
• Speak softly.
• Not be able to move your tongue, lips, and jaw very well.
• Sound robotic or choppy.
• Have changes in your voice. You may sound hoarse or breathy. Or, you may sound like you have a stuffy nose or are talking out of your nose.

Causes of Dysarthria

Dysarthria may be caused by damage to the following:

· Parts of the brain that control muscle movement.

· Cerebellum: The cerebellum, which is located between the cerebrum and brain stem, coordinates the body’s movements.

· Basal ganglia: These large collections of nerve cells help coordinate and smooth out movements.

· Brain stem: The brain stem controls the muscles that are used in breathing and those used to help make sounds.

· The nerve fibers that connect the outer layer of the cerebrum (cerebral cortex) to the brain stem: These nerve fibers relay information needed to control and coordinate the muscles used to produce speech, including muscles of the lips, tongue, palate, and vocal cords.

· Neuromuscular junction: Nerves connect with muscles at the neuromuscular junction.

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These structures can be damaged by degenerative disorders (such as amyotrophic lateral sclerosis, Parkinson disease, and Huntington disease), multiple sclerosis, head injuries, brain tumors, strokes, or infections such as Lyme disease.