Aetiology

Dysarthria is caused by upper motor neurone lesions of the cerebral hemispheres or lower motor neurone lesions of the brain stem. It also results from disruption to the integrated action of upper motor neurones, basal ganglia and cerebellum. The most common cause of dysarthria is alcohol intoxication.

Other causes include:

• cerebellar disease: causing a scanning dysarthria
• extrapyramidal disease: causes monotonous speech since it causes bradykinesia and muscular rigidity
• bulbar or pseudobulbar palsy
  • bilateral lower cranial nerve lesions of cranial nerves IX, X or XII cause a nasal speech, e.g. motor neurone disease, bulbar polio, syringobulbia, medullary tumour, Guillain-Barre syndrome
  • bilateral upper motor neurone of cranial nerves IX, X or XII causes a spastic dysarthria, e.g. cerebral ischaemia, motor neurone disease, multiple sclerosis
• paralysis or weakness of facial muscles: causes slurred speech
• oral lesions, e.g. mouth ulceration, loose dentures