These dysfunctions can present in a variety of ways, such as the stimuli not activating the olfactory bulb, some odors being interpreted as other odors, or hallucinations of smells. These subsets are called anosmia, parosmia, and phantosmia respectively. Anosmia and hyposmia (a less severe form of anosmia with a decreased sensitivity to smell but not the complete lack of it) are more quantitative disabilities typified by degrees in which the odor is sensed. Parosmia and phantosmia are more qualitative disabilities that are denoted by the impromptu introduction of odors without the proper stimulus.
Phantosmia is very similar to parosmia. Both usually result in unpleasant odors in the absence of the corresponding stimulus. Their difference is that parosmia is triggered by other odors; phantosmia is seemingly random. Phantosmia’s etymology is relatively straightforward, a phantom odor; it can be thought of as essentially an olfactory hallucination.
Anosmia is characterized by the inability to detect odors. This particular dysfunction can be acute or chronic, and can also be odor specific. The several different types of anosmia suggest several different causes for the symptoms. While anosmia can occur due to a physical obstruction or infection, it can also be attributed to neurological damage. Acute anosmia tends to be associated with a blockage or infection; specific types of neurological damage are more closely associated with chronic anosmia. There are also cases of people born without the ability to detect odors; they are called anosmics.
Parosmia, or troposmia, is defined by patients incorrectly identifying odors, often mistaking pleasant or neutral odors for unpleasant ones. In order to effectively diagnose parosmia, as well as related diseases such as anosmia, diagnostic tool kits or “Sniffin’ Sticks” can be used to gauge a graded stimulus and measure the response of the patient. One example of parosmia involved using a peppermint “Sniffin’ Stick” by placing it in front of a patient’s nose, then the patient reporting a foul or rotten smell. As with anosmia, some cases of parosmia seemed to be odor specific, whereas other parosmias were more general and several smells were misinterpreted.
- Koo, FS; AK Arya, AC Swift (2007-May). "Smell disorders and dysosmia". BRITISH JOURNAL OF HOSPITAL MEDICINE (PDF) 68 (5): 234–6.
- "Smell and Taste Disorders: Ear, Nose, and Throat Disorders: Merck Manual Home Health Handbook".
- "Dorlands Medical Dictionary:dysosmia".
- Franselli, J; B.N. Landis, S. Heilmann, B. Hauswald, K.B. Huttenbrink, J.S. Lacroix, D.A. Leopold, T. Hummel (2004). "Clinical presentation of qualitative olfactory dysfunction". Eur Arch Otohinolaryngol (PDF) 261: 411–5.
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