Nuclear and supranuclear lesions

• Nuclear lesion (bulbar palsy)
  • = bilateral lesion of the motor nucleus of a cranial nerve, its axon, or its NMJ
  • Pathophysiology
    • Cranial nerves IX, X, XI, and XII are affected
    • Equals a “lower motor neuron” lesion, with typical peripheral motor lesion symptoms like atrophy and flaccidity
  • Clinical features
    • Normal facial expressions (because VII is unaffected)
    • Nasal speech
    • Dysphagia of fluids
    • Atrophic and fasciculating tongue
    • Absent gag reflex
• Supranuclear lesion (pseudobulbar palsy)
  • = bilateral lesion of the corticobulbar tracts
  • Pathophysiology
    • Cranial nerves V, VII, IX, X, XI, XII are affected
    • Equals an “upper motor neuron” lesion, with typical central motor lesion symptoms like spasticity and hyperreflexia
  • Clinical features
    • Stiff, spastic facial muscles -> no facial expressions
    • Spastic dysarthria (Donald Duck voice)
    • Dysphagia
    • Spastic tongue
    • Pseudobulbar affect/emotional incontinence
      • Uncontrollable laughing or crying
      • Think Joaquin Phoenix in the Joker
    • CN V palsy -> exaggerated jaw jerk reflex
    • Brisk gag reflex