7A: Neurogenic Communication disorders

Central nervous system

Brain and spinal cord

Peripheral nervous system

Nerves that connect body to brain and spinal cord

Central Nervous System

Brain enables high-level functions

• Damage can lead to many types of communication disorders

Brainstem and spinal cord provide sensory and motor pathways between body and brain

• Damage can disrupt biological support for speech

Brain: Cerebrum

• Majority of brain

• Right and left hemispheres

Left hemisphere

• controls right side of the body

• tasks linked to language and logic

Right hemisphere

• controls left side of the body

• Tasks linked to creativity, cognition

Brain: Cerebellum

• Below cerebrum, behind brainstem

• Helps coordinate and regulate neural impulses

• Regulates balance, posture, and fine motor movements

Cerebrum: Lobes

• Frontal

• Parietal

• occipital

• Temporal

Frontal lobe

• Primary motor cortex

• Executive functions

Parietal lobe

• primary sensory cortex

• cognitive functions

Occipital

• visual processing

Temporal

• primary auditory cortex

• language comprehension

Cortical regions of interest (and know where they are)

1. Primary auditory cortex

2. Primary motor cortex

3. Broca’s area

4. Wernicke’s area

Primary auditory cortex

• In temporal lobe

• bilateral

• includes Heschl’s gyrus

  • the first area of cortex to process auditory information

  • awareness or perception of sound

Primary Motor cortex

• In frontal lobe along precentral gyrus

• Bilateral

• Controls muscles (including for speech)

Brocas area

• In frontal lobe

• Involved in speech production and expressive language

  • Also plays a role in language comprehension

• Unilateral

  • In left hemisphere in most people

Wernicke’s area

• Temporal lobe, beside primary auditory cortex

• Involved in language comprehension

  • Also plays a role in language production

• Unilateral

  • In left hemisphere in most people

Subcortical regions of interest

1. Basal Ganglia

2. Thalamus

Basal Ganglia

• Involved in movement

• Connected to cerebellum and cortex

Thalamus

• Relay area between parts of cortex

• Many functions, including motor and sensory

Peripheral Nervous System

• Helps the CNS communicate with the body

made of:

1. Cranial Nerves

2. Spinal nerves

Cranial nerves

• 12 pairs of nerves

• Enter/exit brain and brainstem

Spinal nerves

• 31 pairs of nerves

• Enter/exit spinal cord

1. Ascending nerve tract

2. Descending nerve tracts

Ascending nerve tract

• Sensory

  • From glands, tissues, joints, etc.

• Posterior (exit back portion of spinal cord)

Descending nerve tracts

• Motor

• Innervate muscles of chest, abdomen, limbs

• Anterior (exit front portion of spinal cord)

Neurogenic communication disorders are usually…

brain-based, acquired disorders

Types of Neurogenic communication disorders

1. Acquired motor speech disorders

   • Dysarthria

   • Apraxia

2. Acquired language disorders

   • Aphasia

3. Cognitive-communication disorders

Distribution of neurogenic communication disorders

Dysarthria

• Caused by weakness, paralysis, slowness, or incoordination of muscles responsible for speech

• Impairment in speed, force, range, direction, or timing of motor control for speech

• May also have involuntary movements or alterations in muscle tone

• Different types based on lesion location within CNS/PNS

• Common causes: stroke, Parkinson’s Huntington’s, ALS, cerebellar disease

6 types of Dysarthria

1. Hyperkinetic Dysarthria

• Involuntary movements

• Several subtypes

  • Chorea

  • Oromandibular Dystonia

  • Spasmodic Dysphonia

  • Essential voice tremor

Chorea

• Fast, unpredictable, random and arrhythmic involuntary movements

• Some common causes: Huntington's disease, stroke, HIV infection

• Distinctive speech characteristics: variable speech rate, excess loudness variation, rapid and unpredictable consonant and vowel distortions

Oromandibular Dystonia

• Slow, sustained involuntary movements and spasms of face, lips, jaw, tongue, and velum

• Some common causes: unknown (idiopathic), drugs, head trauma

• Distinctive speech characteristics: voice stoppages, voice tremor, prolonged consonant and vowel distortion

Spasmodic Dysphonia

• Strained, effortful phonation or irregular voice stoppage due to hyperadduction or hyperabduction of vocal folds

• Cause: Unknown

Essential voice tremor

• Rhythmic tremor in voice intensity or voice pitch, regular voice stoppages

• Cause: Unknown, 30% have family history

Hypokinetic Dysarthria

• Hypokinetic: reduced ability to move, rigidity, reduced range of motion, slowness

• Most common cause: Parkinson’s disease and related Parkinson-like disorders

• Distinctive speech characteristics

  • Hypophonia (soft speech)

  • Imprecise consonant articulation

  • Short rushes and rapid rate of speech

  • Monotone pitch and monoloudness

Spastic Dysarthria

• Increased tone (stiffness, tightness) in muscles with reduced fine motor control, weakness, and slowness of movement

• Some common causes: stroke, ALS, TBI, MS

• Distinctive speech characteristics

  • Slow rate

  • Low pitch

  • Harsh and strained-strangled vocal quality

  • Imprecise production and distortion of consonants and vowels

Flaccid Dysarthria

• Flaccid: Muscle weakness, reduced muscle tone

• Some common causes: trauma, neurosurgery, ALS, muscular dystrophy, tumour, stroke

• Distinctive speech characteristics

  • Hypernasality

  • Breathiness

  • Nasal emission

  • Audible inspiration

Ataxic Dysarthria

• Impaired coordination of movement

• Some common causes: stroke, TBI, MS, brain tumours

• Distinctive speech characteristics

  • Sounds “slurred,” “intoxicated”

  • Imprecise consonant and vowel production

  • Irregular breakdown in articulation accuracy

  • Excess and equal stress (metering out syllables)

Mixed Dysarthria

• Most common dysarthria type •

• Two or more pure dysarthria types •

• Causes –

  • More diffuse damage than other dysarthrias

  • Commonly associated with degenerative disorders (e.g., ALS, MS)

    • E.g., ALS commonly presents with spastic flaccid dysarthria)

Dysarthria Summary

Apraxia

• Acquired neurological impairment in motor speech planning and programming

• Inability to voluntarily select and program skilled motor movements for speech

• Unrelated to weakness, slowness, paralysis

• Speech characteristics

  • Groping attempts and great variability

  • Repeated attempts to correct errors

  • Complex, long words are difficult

Distribution of acquired motor speech disorders