Flaccid Dysarthria (Lower Motor Neuron Lesion)

• Clinical Features:
  • Lax open mouth
  • Atonia
  • Weakness
  • Wasting
  • Drooling
  • Feeding difficulties
  • Absent jaw, gag, and cough reflexes
• Causes:
  • Dystrophia myotonica
  • Prader-Willi Syndrome
  • Myasthenia gravis
  • Facio-scapulo-humeral dystrophy
  • Congenital dysplasia of the brainstem (e.g., Moebius)
  • Pontine gliomas
  • Progressive motor neurone diseases (e.g., Fazio-Londe)
  • Vascular lesions of the brainstem
  • Posterior fossa tumour resection

Spastic Dysarthria (Upper Motor Neuron Lesion)

• Clinical Features:
  • Release of brainstem reflexes
  • Stiff jaw
  • Difficulty opening mouth
  • Brisk jaw jerk with clonus
  • Small bunched tongue
  • Rapid tongue movements are difficult
  • Gag and cough reflexes present
  • No wasting
• Causes:
  • Cerebral palsy
  • Degenerative brain diseases (e.g., Batten disease, Metachromatic leukodystrophy)
  • Acquired traumatic brain injury

Dysarthria Associated with Cerebral Palsy

• Clinical Features:
  • Unwanted movements interfering with normal articulation
  • Retention of obligatory feeding reflexes
  • Gag and cough reflex retained
• Causes:
  • Kernicterus
  • Hypoxic-ischemic brain injury
  • Degenerative diseases of the basal ganglia

Ataxic Dysarthria (Cerebellum)

• Clinical Features:
  • Gag and cough reflex retained
  • Disrupted rhythm and volume control
  • Features of verbal dyspraxia
  • Slow development of speech articulation
• Causes:
  • Congenital abnormalities of the cerebellum
  • Posterior fossa resections
  • Syndromic examples (e.g., Joubert syndrome)
  • Post-acquired cerebellar disorders