Hypokinetic Dysarthria Notes

Hypokinetic Dysarthria

Definition

• Defined by J. Duffy, 2020, as a perceptually distinct motor disorder associated with basal ganglia control circuit pathology.
• Manifests in respiratory, phonatory, resonatory, articulatory, and prosodic levels of speech.
• Most evident in disturbances of voice, articulation, and prosody.
• Characterized by:
  • Rigidity
  • Reduced force and range of movement
  • Slow individual movements
  • Sometimes fast repetitive movements in speech
• Decreased range of movement is the main contributor, hence "HYPOkinetic" dysarthria.
• Parkinson's disease is the prototype, but other conditions also exist.

Incidence

• Mayo Clinic: 15.3% of all dysarthrias and 14.4% of all MSDs.

Etiologies

• Degenerative diseases:
  • Parkinson's disease
  • Parkinsonism
  • Progressive supranuclear palsy (PSP)
  • Multiple system atrophy (MSA)
  • Shy-Drager syndrome
  • Some Alzheimer's disease patients
• Trauma:
  • Example: Muhammad Ali
• Vascular:
  • Multiple or bilateral strokes affecting the basal ganglia
• Toxic/metabolic:
  • Antipsychotic medications
  • Possibly pesticides
• Infectious causes:
  • Viral encephalitis
• Other causes:
  • Normal pressure hydrocephalus
  • Obstructive hydrocephalus
• May be a component of inherited diseases:
  • Juvenile-onset PD
  • Wilson's disease
  • Huntington's disease

Distribution of Etiologies

• 89% Degenerative disease
• 5% Undetermined
• 3% Vascular
• 3% Other (drug-induced, normal pressure hydrocephalus)

Module 4 Overview (parkinsonvoiceproject.org)

• Extrapyramidal Motor System:
  • Responsible for automatic movements (talking, swallowing, arm swinging).
  • Performed without conscious effort.
  • Highly dependent on dopamine.
• Pyramidal Motor System:
  • Responsible for intentional and deliberate movements (putting on makeup, driving in the rain, learning piano).
  • Less dependent on dopamine.
  • Functions better for people with Parkinson's.
• Intent: activating the intentional motor system can bypass the automatic motor system.

Basal Ganglia & Extrapyramidal System

• Basal ganglia major structures:
  • Sensorimotor cortex
  • Putamen
  • Internal capsule
  • Caudate nucleus
  • Thalamus
  • Globus pallidus
  • Subthalamic nucleus
  • Substantia nigra
• Extrapyramidal motor system includes:
  • Corpus striatum
  • Subthalamic nucleus
  • Substantia nigra
  • Red nucleus
  • Brain stem reticular formation
  • Descending spinal cord tract other than corticospinal tract

Basal Ganglia

• Located deep within the cerebral hemispheres.
• Include:
  • Striatum (caudate nucleus and putamen)
  • Lentiform nucleus (putamen and globus pallidus).
• Substantia nigra and subthalamic nuclei in the midbrain are closely related anatomically and functionally.
• Activities are strongly associated with the extrapyramidal or indirect activation pathway.
• Functions:
  • Regulate muscle tone.
  • Control postural adjustments during skilled movements.
  • Regulate movements (arm swing).
  • Scale the force, amplitude, and duration of movements.
  • Adjust movements to the environment.
  • Assist in the learning, preparation, and initiation of movements.
• Damage either reduces movement (hypokinetic) or fails to inhibit involuntary movement.

Basal Ganglia Connections

• Deficits in speech are mostly associated with reduced movement.
• Imbalances of neurotransmitters (primarily dopamine) are associated with basal ganglia circuit malfunction.
• Low dopamine levels cause an imbalance with acetylcholine.
• Dopamine inhibits neural firing, while acetylcholine facilitates it.
• When substantia nigra neurons are destroyed, dopamine supply to the striatum is reduced.

Basal Ganglia Connection with Speech Production

• Influences speech via connections with motor areas of the cerebral cortex.
• Damps or modulates cortical output that would otherwise be in excess.
• In hypokinetic dysarthria, damping of movement is excessive due to imbalances of dopamine and acetylcholine.
• Damage to substantia nigra neurons reduces dopamine supply to striatum.

Swigert, continued

• Stuttering: Repeated or prolonged phonemes or syllables, more at the beginning of utterances.
• Palilalia: Compulsive reiteration of utterances with increasing rate and loudness; repetitions are usually words and/or phrases.
• Inappropriate silences.
• Difficulty judging their own deficit in loudness and intelligibility.
• May see depression.

Hypokinetic Dysarthria: Speech Subsystems

• Respiration:
  • Decreased support, resulting in monoloudness, short rushes, and decreased loudness.
• Phonation:
  • Hoarseness, breathiness, tremulous voice, decreased loudness, monoloudness, monopitch.
• Resonance:
  • Some hypernasality in 10-25% of PD cases.
• Articulation:
  • Changes in manner of production with undershooting on articulatory targets (stops, fricatives, and affricates).
• Prosody:
  • Increased rate, monotone, short rushes of speech, phrase or syllable repetitions, reduced stress, palilalia with excessive pauses, reduced stress, variable rate.

Associated Clinical Characteristics

• Decreased mobility or range of motion
• Excessive tone
• Shuffling gait (festinating gait)
• Resting tremor (most often seen in head, jaw, tongue, and lips)
• Rigidity
• Bradykinesia
• Masked-faces or hypomimia
• Drooling
• Balance issues; may fall backwards more easily

Non-speech Characteristics of Parkinsonism

• Resting or static tremor (most noted during rest)
• Pill-rolling: between thumb and forefinger
• Rigidity: resistance throughout the range during passive stretch.
• Cog-wheel rigidity: jerky resistance throughout the range of movement.
• Posture: involuntary flexion of head, trunk, and arms.
• Poor postural reflexes making turning in bed, sit to stand, and postural adjustments difficult.
• Bradykinesia: reduced speed, delays or false starts in movement, slowness of movement once begun, reduced ROM.
• Freezing or akinesia may occur when meds are in Off state.
• Micrographic writing
• Autonomic failure: orthostatic bp, sweating, sphincter and erectile dysfunction
• Cognitive decline.

Salient Features

• Phonatory-Respiratory:
  • Reduced loudness
  • Reduced utterance length
• Articulation:
  • Repeated phonemes
  • Palilalia
  • Rapid or blurred AMRs
• Prosody:
  • Reduced stress
  • Monopitch
  • Monoloudness
  • Inappropriate silences
  • Short rushes of speech
  • Variable rate
  • Increased rate in segments
  • Increased overall rate
• Physical:
  • Masked faces
  • Tremulous jaw, tongue, lips
  • Reduced ROM on AMRs
  • Head tremor
• Patient complaints:
  • Loudness
  • Rapid rate (mumbling)
  • Difficulty initiating speech
  • Stiff lips

Hypokinetic Dysarthria: Summary of Distinguishing Characteristics

• Speech:
  • Rapid rate
  • Short rushes of speech
  • Reduced loudness
  • Tight breathiness
  • Monopitch/monoloudness
  • Imprecise articulation
  • Rapid and blurred AMRs
  • Flutter during sustained phonation
• Nonspeech:
  • Hypomimia
  • Tremulous jaw, tongue
  • Reduced ROM during AMR tasks
  • Mild weakness

Differential Diagnostic Tools

• Conversational speech, oral reading, AMRs, and vowel prolongation.
• Connected speech identifies prosodic and loudness abnormalities.
• Speech AMRs indicate reductions in ROM and rate abnormalities.
• May sometimes have rapid, accelerating speech with indistinct articulation.
• Vowel prolongation to assess loudness and quality.
• LSVT and SPEAKOUT! have excellent protocols for assessment.

Patients' Description of Their Speech

• Voice cannot be heard in loud situations, conversations with more than one person.
• Speech is too fast.
• Voice lacks emotions.
• Sometimes stutter.
• Lips feel rigid and stiff.
• Can't start my voice.
• Family or significant others typically complain about the patient's weak voice, not the patient.

Treatment Options

• Prioritize speech subsystems that have the greatest effect on overall functionality/intelligibility.
• Speech Vive
• Lee Silverman Voice Treatment Program (LSVT)
• SPEAK OUT!
• Deep Brain Stimulation
• Traditional artic/respiration/phonation tx vs. High effort/high intensity treatments.