SPASTIC DYSARTHRIA NOTES (UMN Bilateral)

Overview

  • Spastic dysarthria: bilateral upper motor neuron (UMN) involvement affecting direct and indirect activation pathways.
  • Affects all speech subsystems; intelligibility often reduced.
  • UMN signs: hypertonia/spasticity; hyperreflexia; Babinski signs; "− signs" include loss of fine motor control, reduced range, weakness.

Causes

  • Etiology distribution (Duffy, 2020):

    • Degenerative: 60%60\%
    • Vascular: 17%17\%
    • Undetermined: 10%10\%
    • Congenital: 8%8\%
    • Traumatic: 4%4\%
    • Demyelinating: 1%1\%

  • Amyotrophic Lateral Sclerosis (ALS): degenerative motor neuron disease; unknown cause; progressive loss of UMN and LMN; terminal; dysphagia often co-occurs.

  • Stroke: bilateral damage patterns involving internal carotid/MCA/PCA; various stroke configurations can add to previous injuries.

  • Traumatic Head Injury: widespread cortical/subcortical/brainstem injury; spastic dysarthria possible; mixed dysarthria common.

Speech Characteristics

  • All components of speech can be affected: respiration, phonation, resonance, articulation, prosody.
  • Typical speech features:
    • Imprecise consonants and distorted vowels (articulation).
    • Monopitch and monoloudness (prosody/phonation).
    • Slow rate; short phrases (prosody).
    • Harsh/strained–strangled voice quality (phonation).
    • Hypernasality (resonance).
    • Low pitch and occasionally pitch breaks.
    • Short phrases with reduced stress; excess and equal stress can occur.

Non-speech Clinical Signs

  • Dysphagia (swallowing problems)
  • Drooling
  • Pseudobulbar affect (emotional lability)
  • Pathologic oral reflexes (e.g., suck, snout, palmomental, jaw jerk, bite)

Speech Mechanism Examination

  • Assess: Face, jaw, tongue, velopharynx, larynx (phonation), respiration.
  • Conditions of examination: at rest, during movement, sustained postures, reflexes

Assessment of Spastic Dysarthria

  • 3 key tasks (in addition to oromotor exam):
    1. Conversational speech and/or reading → observe resonance, articulation, prosody
    2. Speech AMRs (e.g., puh-puh-puh / tuh-tuh-tuh / kuh-kuh-kuh) → observe rate (often slow)
    3. Vowel prolongation → observe phonation; harsh voice quality

Summary

  • Spastic dysarthria arises from bilateral UMN damage (Direct and indirect activation pathways).
  • UMN signs: hypertonia, spasticity, hyperreflexia, Babinski (+); negative signs include reduced ROM, weakness.
  • Distinctive speech features: impaired articulation (imprecise consonants, distorted vowels); harsh/strained phonation; hypernasality; monopitch/monoloudness; slow rate; short phrases.