Chemosensation / Disorders
Disturbances of olfaction and/or gustation
| The perception of flavour is a combination of smell, taste and texture, which results in considerable overlap between gustatory and olfactory disorders. Patients with anosmia typically complain of ageusia as well. |  |
Classification Systems
Description
| OLFACTION | GUSTATION | |
|---|---|---|
| Complete absence of sensation | anosmia | ageusia |
| Reduced sensation | hyposmia | hypogeusia |
| Increased perception | hyperosmia | |
| Distortion or perversion | dysosmia parosmia (= perception when not present) |
dysgeusia |
| Extremely unpleasant perception (revolting) | cacosmia | cacogeusia |
| Inability to identify/name the sensation: agnosia |
- anosmia/ageusia typically results in anorexia and severe weight loss, which can be fatal
Location
- PERIPHERAL: chemicals can't reach the receptors, or are altered on the way to the receptor
- olfaction: smoking, anything that causes swelling of the nasal mucosa (rhinitis)
- gustation: smoking, dry mouth, hyperviscosity of saliva (cystic fibrosis)
- NEUROEPITHELIAL: damage or absence of receptor cells, or damage to their processes or any aspect of the transduction mechanism
- olfaction: congenital deficits, metabolic and nutritional deficiencies, head injury (severing of axons as they pass through the cribriform plate), many drugs, aging
- gustation: radiation (cancer treatment), many drugs, aging
- CENTRAL:
- hallucinations and loss of discrimination are usually of central origin
- tumors, epilepsy, psychiatric disorders (depression, schizophrenia)
- gustatory hallucinations are much less common than olfactory
- unilateral defects are typically not recognized by the patient