SPA 127 - Ch. 9: Motor Speech Disorders

Two Types of Motor Speech Disorders

• Dysarthria

  • Results from weakness, paralysis, or incoordination in muscles used to produce speech

• Apraxia

  • Results from damage to the parts of nervous system responsible for planning and programming movements for speech

Dysarthria

• Damage to central and/or peripheral motor systems

• Damage to the cerebellum

Human Nervous System

• Central Nervous System

  • Brain

  • Spinal Cord

• Peripheral Nervous System

  • Cranial nerves

  • Spinal nerves

Cerebellum

• “Small brain”

• Coordination and precise control of motor movements

  • Includes timing and fluidity of speech

Cerebral Palsy

• Non-progressive, permanent disorders of movement and postural development

• Incidence: about 1.5 to 4 infants per 1,000 live births

• Caused by brain damage before (pre-natal), during (perinatal), or soon after birth (postnatal)

  • Restricted oxygen supply (anoxia)

  • Trauma

Classification of Cerebral Palsy

• By neuromuscular characteristics

  • Spastic

  • Atheotoid/dyskinetic

  • Ataxic

Spastic CP

• Damage to motor cortex

• Spasticity (resistance to passive stretch)

• Increased muscle tone

• Jerky, stiff, labored movements

Dyskinetic CP

• Subcortical damage (e.g. basal ganglia)

• Slow, involuntary movements

• Writhing movements common during purposeful/volitional movements

Ataxic CP

• Damage to the cerebellum

• Uncoordinated movements (clumsy)

• Difficulty achieving a motor target

• Difficulty maintaining rhythm

Levels of Severity in Cerebral Palsy

• Mild: Self-help skills are adequate to care for personal needs, no significant speech problems, ambulates without appliances, no treatment necessary

• Moderate: Speech is impaired and special equipment may be needed for ambulation. Self-help skills are insufficient to meet daily care needs. Habilitation therapy is needed

• Severe: Poor prognosis for developing self-help skills, ambulation, and functional speech even with treatment and the use of adaptive equipment

Developmental Characteristics

• Developmental delay in sitting, walking, and speech development

• All aspects of speech production are impaired (articulation, resonance, etc.)

Cerebral Palsy: Speech Characteristics

• Respiration:

  • Reduced vital capacity

  • Impaired ability to generate and maintain pressure below vocal folds

• Phonation:

  • Intermittent breathiness/strangled harshness of voice

• Resonance:

  • Hyper nasality and nasal emission

• Articulation:

  • Speech sounds involving the tip of the tongue are most challenging (/s/, /z/, /l/, /r/)

• Prosody:

  • Poor respiratory control

    • One of two utterances per breath

  • Poor laryngeal tension control

    • Hard to manipulate changes in pitch

Childhood Apraxia of Speech

• 1 or 2 children per 1,000

• Causes have not yet been identified

• Severe speech delays

  • Vowel errors

  • Inconsistent production over repeated attempts

  • Altered intonation and word stress

Acquired Causes of Dysarthria (Adults)

• Stroke (blood flow to the brain is cut off)

• Degenerative Disorders (loss of neurons)

• Autoimmune disorders

• Tumors

• Traumatic Brain Injury

• Toxins

Types of Dysarthria

• 5 types

  • Spastic

  • Flaccid

  • Ataxic

  • Hypokinetic

  • Hyperkinetic

• This classification based on:

  • Impaired neuromuscular processes

Spastic Dysarthria

• Site of Damage: Upper motor neurons (in the cortex)

• Neuromuscular Impairment

  • Spasticity = Increased muscle tone and weakness

  • Hyperactive reflexes

  • Ex. CP, TBI, multiple strokes

• Speech Characteristics

  • Shallow breathing

  • Strained/strangled voice

  • Imprecise consonants

  • Hypernasality

  • Slow speech rate

  • Pitch and loudness variations reduced

Flaccid Dysarthria

• Site of Damage: Lower motor neurons (in cranial nerves)

• Neuromuscular Impairment

  • Reduced muscle tone and weakness

  • Flaccidity (lowered resistance to passive stretch)

  • Twitching and wasting of muscles

  • Hypoactive reflexes

• Speech Characteristics

  • Poor speech breathing

  • Breathy voice

  • Imprecise articulation

  • Hypernasality

  • Reduced rate of speech

  • Ex. Bell’s Palsy, Myasthenia Gravis, Brainstem Stroke

Ataxic Dysarthria

• Site of Damage: Cerebellum

• Neuromuscular Impairment

  • Incoordination

  • Impaired accuracy and timing of movements

  • Minimal muscle weakness

  • Normal reflexes

• Speech Characteristics

  • Irregular breathing

  • Irregular and explosive changes in pitch and loudness

  • Irregular breakdown in articulation resulting in distorted vowels and consonants

  • Prosodic abnormalities (prolonged pauses)

  • Ex. Friedreich’s Ataxia

Hypokinetic Dysarthria

• Site of Damage: Extrapyramidal Pathways

• Neuromuscular Impairment

  • Slow movements (bradykinesia)

  • Rigidity

  • Difficulty initiating & stopping movement

  • Resting tremors

• Speech Characteristics

  • Reduced loudness

  • Imprecise articulation due to reduced range of movement of articulators

  • Pitch and loudness variation reduced

  • Perceived rapid speech rate

  • Ex. Parkinson’s Disease

Hyperkinetic Dysarthria

• Site of Damage: Extrapyramidal pathways

• Neuromuscular Impairment

  • Involuntary uncontrollable movements (slow or quick)

• Speech Characteristics

  • Speech breathing disrupted by involuntary movements

  • Imprecise articulation

  • Variable speech rate

  • Prosodic abnormalities (prolonged pauses)

  • Ex. Huntington’s Tourette’s

Mixed Dysarthria

• Two or more types of dysarthria in an individual

• Ex. Amyotrophic Lateral Sclerosis (ALS)

  • Flaccid-spastic dysarthria