General
- Lesions of the olfactory nerve result from head trauma, tumors, tobacco smoking, and the common cold.
Bilateral anosmia
- Neither nostril can smell anything.
- Due to
- Both the nostrils are damaged or blocked
- Trauma
- Tumour
- Sinusitis/rhinitis
- Both the cribriform plates are destroyed
- Trauma
- Tumour
- Meningitis
- Both the olfactory bubs are destroyed
- Trauma
- Tumour
- Meningitis
- Neither of the olfactory bulbs had ever worked in the first place
- Congenital anosmia eg. Kallmann's syndrome
- The cellular sensory apparatus has been rendered insensitive
- Smoking
- Chemotherapy or radiotherapy
Unilateral anosmia
- One nostril is affected.
- Due to
- One of the nostrils is damaged or blocked
- Trauma
- Tumour
- Sinusitis/rhinitis
- One of the cribriform plates are destroyed
- Trauma
- Tumour
- One of the olfactory bubs are destroyed
- Trauma
- Tumour - particularly, olfactory groove meningioma
Hypoosmia
- The sense of smell is present but its sensitivity is decreased.
- Due to
- Local processes
- Sinusitis/rhinitis
- Nasal polyps
- Global processes
- Smoking
- Chemotherapy
- Chronic industrial solvent exposure
- Characteristic associated conditions
- Vitamin A deficiency
- Pernicious anaemia
- NIDDM (where it is a part of the spectrum of neuropathy)
Hyperosmia
- "Osmophobia": the perception of smells is pathologically exaggerated.
- Due to
- Addison's disease
- Cystic fibrosis
- Pituitary tumours
Dysosmia
- The sense of smell works, but is distorted.
- Due to
- Alzheimer's disease
- Korsakoff's psychosis
- Huntington's chorea
- Parkinson's disease.
Olfactory hallucinations
- "Eew! Can anybody else smell that? ... ...no?..."
- Due to
- Migraine
- Schizophrenia
- Temporal lobe epilepsy
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