Dysarthria

A motor speech disorder resulting from neurological injury of the motor component of the motor–speech system

 

It is characterized by poor articulation of speech.

 

Problems occur with the muscles that help produce speech, making it difficult to pronounce words. 

 

Muscles included are those of the head and neck, the dysfunction of which characterizes dysarthria.

 

With dysarthria the speech subsystems of respiration, phonation, resonance, and articulation can be affected.

 

When speech subsystems are impaired it leads to abnormal vocal communication

 

Dysarthria that has progressed to a total loss of speech is referred to as anarthria. 

 

Neurological injury due to damage in the central or peripheral nervous system may result in weakness, paralysis, or a lack of coordination of the motor–speech system, producing dysarthria.

 

Causes of dysarthria include: toxic, metabolic, degenerative diseases, traumatic brain injury, or thrombotic or embolic stroke, degenerative diseases include parkinsonism, amyotrophic lateral sclerosis (ALS), multiple sclerosis, Huntington’s disease, Niemann-Pick disease, Friedreich’s ataxia, Wilson’s disease, hypoxic encephalopathy and central pontine myelinolysis.

 

Neurological injury effects control over the tongue, throat, lips or lungs.

 

Swallowing problems are also often present in those with dysarthria. 

 

Cranial nerves involved in control of the muscles relevant to dysarthria include: 

 

trigeminal nerve’s motor branch (V), 

 

the facial nerve (VII), 

 

glossopharyngeal nerve (IX), 

 

the vagus nerve (X), 

 

and the hypoglossal nerve (XII).

 

Dysarthria does not include speech disorders from structural abnormalities.

 

Areas of the brain involved in planning, executing, or regulating motor operations in skeletal muscles occur.

 

Dysfunction of muscles function is a result  of failure: the motor or somatosensory cortex of the brain, corticobulbar pathways, the cerebellum, basal nuclei, brainstem or the neuro-muscular junction,with diseases such as myasthenia gravis, which block the nervous system’s ability to activate motor units and effect correct range and strength of movements.

 

Causes of dysarthria: 

 

Brain tumor

 

Cerebral palsy

 

Guillain–Barré syndrome

 

Hypothermia

 

Lyme disease

 

Stroke

 

Intracranial hypertension 

 

Tay–Sachs disease,

 

Dysarthrias are classified based on the presentation of symptoms:

 

spastic

 

flaccid

 

ataxic

 

Unilateral upper motor neuron 

 

Hyperkinetic and hypokinetic

 

Mixed 

 

Spastic dysarthria results from bilateral damage to the upper motor neuron.

 

Flaccid dysarthria results from bilateral or unilateral damage to the lower motor neuron

 

Ataxic dysarthria results from damage to the cerebellum, and is an acquired neurological and sensorimotor speech deficit.

 

Damage to the superior cerebellum and the superior cerebellar peduncle is believed to produce dysarthria in ataxic patients.

 

The likelihood of cerebellar involvement specifically affecting speech motor programming and execution pathways, produce features associated with ataxic dysarthria. 

 

It is a common diagnosis among the clinical spectrum of ataxic disorders.

 

Unilateral upper motor neuron has milder symptoms than bilateral upper neuron damage.

 

Hyperkinetic and hypokinetic dysarthria  results  from damage to parts of the basal ganglia, such as in Huntington’s disease or Parkinsonism).

 

The majority of dysarthric patients experience mixed dysarthria, as neural damage resulting in dysarthria is rarely contained to one part of the nervous system.

 

Speech motor control is linked to abnormalities in articulation and prosody, which are hallmarks of this disorder.

 

Ataxia dysarthria is associated with alterations of the normal timing pattern, with prolongation of certain segments and a tendency to equalize the duration of syllables when speaking. 

 

As the severity of the process worsens  segments lengthen.

 

Ataxic dysarthria symptoms include:  abnormalities in speech modulation, rate of speech, explosive or scanning speech, slurred speech, irregular stress patterns, and vocalic and consonantal misarticulations.

 

Ataxic dysarthria is associated with damage to the left cerebellar hemisphere in right-handed patients.

 

Dysarthria severity ranges from occasional articulation difficulties to verbal speech that is completely unintelligible.

 

Dysarthria may manifest as speech altered by: 

 

Timing

 

Vocal quality

 

Pitch

 

Volume

 

Breath control

 

Speed

 

Strength

 

Steadiness

 

Range

 

Tone

 

Dysarthria is treated by speech language pathologists.

 

Treatment targets the correction of articulation. prosody, the appropriate emphasis and inflection, resonance and phonation.

 

Treatments  involve exercises to increase strength and control over articulator muscles and using alternate speaking techniques to increase speaker intelligibility.

 

Communication devices that make coping with a dysarthria easier include speech synthesis and text-based telephones.