1. Definition: A group of speech disorders resulting from disturbances in muscular control-weakness, slowness, or incoordination- of the speech mechanism due to damage to the central or peripheral nervous system or both. The term encompasses coexisting neurogenic disorders of several or all the basic processes of speech: respiration, phonation, resonance, articulation, and prosody (Darley, 1969).
    1. Medical dictionary definition: imperfect articulation in speech.
    2. Dysarthria refers to a group of disorders rather than a single disorder. It is more appropriate to refer the plural form "dysarthrias" rather than the singular form "dysarthria".
    3. Dysarthrias are speech disorders. They should not be confused with language disorders such as aphasia, language of confusion, or language of generalized intellectual impairment. The clinical relevance of this distinction is in patient management. Treatment for dysarthria differs from that employed for language disorders.
    4. Dysarthrias result from disruption of muscular control. Due to damage of the CNS or PNS or both. There is some involvement of the basic motor processes used in speech and this results in a movement disorder.
  2. Possible disruption of all basic motor processes of speech (Figure 12.4 in Text). Involvement of several processes may contribute more to overall severity than does disrupted articulation.
    1. Respiration: slow, restricted, weak, or uncoordinated muscles activity used in breathing for speech.
    2. Phonation: producing sound in the larynx.
    3. Resonance: Selectively amplifying sound by changing the size, shape, and number of cavities through which it must pass.
    4. Articulation: is considered the movement of speech structures employed in producing the sounds of speech.
    5. Prosody: varying intonation, stress, and rhythm during speech.
  3. Localization: neuroanatomical area or system involved. Dysarthria, depending on the type, can result from impairment of the upper motor neuron system, the lower motor neuron system, the cerebellum, the extrapyramidal system, or combinations of these areas.
  4. Classification System used with dysarthrias is based on the site of lesion and common speech perceptual characteristics. Dysarthrias are neuromuscular speech disorders arising from motor pathway damage at singular or multiple sites from the cortex to muscle. They may affect the entire speech production mechanism, including respiratory, phonatory, and articulatory processes. The type of dysarthria demonstrated will depend upon the site of lesion within the motor pathway.
    1. Perceptual characteristics (Table 12.4 in Text) - Darley, Aronson, & Brown (1975, 1969) have developed a perceptual classification system of dysarthrias. Their work has come to be known as the Mayo Clinic Study. They collected speech sample from 2000 dysarthric clients with diagnosed neurologic lesions or disease. They concluded that dysarthrias resulting from damage in different parts of the nervous system sound different and can be differentiated according to specific perceptual dimensions.
      1. Pitch
      2. Loudness
      3. Voice quality
      4. Respiration
      5. Prosody
      6. Articulation
    2. Neuroanatomic areas involved
      1. Flaccid Dysarthria
        1. Site of Lesion - Peripheral nervous system or lower motor neuron system.
        2. Neuromuscular Symptoms
          1. Weakness
          2. Lack of normal muscle tone
        3. Perceptual Characteristics
          1. Hypernasality
          2. Imprecise consonant productions
          3. Breathiness of voice
          4. Nasal emission
      2. Spastic Dysarthria
        1. Site of lesion - Pyramidal and extrapyramidal systems
        2. Neuromuscular Symptoms
          1. Muscular weakness
          2. Greater than normal muscular tone
        3. Perceptual Characteristics
          1. Imprecise consonants
          2. Harsh voice quality
          3. Hypernasality
          4. Strained-strangled voice quality
      3. Ataxic Dysarthria
        1. Site of lesion - Cerebellum
        2. Neuromuscular Symptoms
          1. Inaccuracy of movement and Slowness of movement.
        3. Perceptual Characteristics
          1. Imprecise consonants
          2. Irregular articulatory breakdowns
          3. Prolonged phonemes
          4. Prolonged intervals
          5. Slow rate
      4. Hypokinetic Dysarthria
        1. Site of Lesion - Subcortical Structures involving Basal Ganglia
        2. Neuromuscular Symptoms
          1. Slow movements
          2. Movements limited in extent (limited range of movement)
        3. Perceptual Characteristics
          1. Articulatory mechanism - Impaired because of reduced range of motion involving the lips, tongue, and jaw. Disturbance may range from mildly imprecise to total unintelligibility.
      5. Hyperkinetic Dysarthrias
        1. Site of Lesion - Subcortical Structures involving Basal Ganglia
        2. Neuromuscular Symptoms
          1. Quick, unsustained, involuntary movements
        3. Perceptual Characteristics associated with Gilles de la Tourette's syndrome
          1. Emission of grunts as a result spontaneous contractions of the respiratory and phonatory muscles
          2. Barking noises
          3. Echolalia
          4. Coprolalia: obscene language without provocation or reason.
      6. Mixed Dysarthrias
        1. Amyotrophic Lateral Sclerosis
          1. Site of Lesion - Progressive degeneration of the upper & lower neuron system. Most cases appears without a known cause
          2. Neuromuscular Symptom
            1. Impairs the function (weakness and paralysis) of all the muscles used in speech production
          3. Perceptual Characteristics
            1. Slow rate
            2. Shortness of phrase
            3. Imprecision of consonants
            4. Hypernasality
            5. Harshness

Apraxia of Speech

  1. Description - Apraxia is a problem in assembling the appropriate sequence of movements for speech production or the executing the appropriate serial ordering of sounds for speech. Primary disorder is an inability to program articulatory movements. Since these problems cannot be explained by significant slowness, weakness, restricted range of movement or incoordination of the articulators, apraxia is not dysarthria and no significant muscle involvement exists. Prosodic alterations may be associated with the articulatory problem, perhaps in compensation for it.
  2. Localization - Apraxia results from a unilateral, left hemisphere lesion involving the third frontal convolution, Broca's area. There is a possibility of apraxia following more posterior, probably parietal lesions.
  3. Speech Characteristics
    1. Articulation Process
      1. Common characteristic is the patient's groping to find the correct articulatory postures and sequences.
      2. Facial grimaces, moments of silence, and phonated movements of articulators are common occurrences.
      3. Consonant phonemes are involved more often than vowel phonemes
      4. Articulation errors are inconsistent and highly variable, not referable to specific muscle dysfunction
      5. Articulatory errors are primarily substitutions, additions, repetitions, and prolongations-essentially complications of the act of articulation.
    2. Prosody Process
      1. Durational relationships of vowels and consonants are distorted
      2. Rate of production is slow
      3. Alterations of the intonation



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