Olfactory Disturbances (4 Types):

Quantitative Abnormalities

  • Loss or reduction of sense of smell (anosmia or hyposmia)
    • Can be from the nasal, neuroepithelial, or central level
    • if bilateral, patient usually complains of ageusia (loss of taste)
  • Increased olfactory acuity (hyperosmia)
    • very rare, if exists

Qualitative Abnormalities

  • distortions or illusions of smell (dysosmia or parosmia)
  • May be associated with depressive illness

Olfactory Hallucinations/Delusions

  • Always of central origin
  • Most often due to temporal lobe seizures (uncinate fits)

Higher-order loss of discrimination (Olfactory Agnosia)

  • Perceptual aspects intact, but deficits in recognition