Defining Olfactory Disorders
Anosmia describes a complete loss of smell; the term "specific anosmia" refers to someone's inability to perceive a certain odor 34. Hyposmia describes a diminished olfactory sensitivity, hyperosmia an enhanced odor sensitivity (compare 35). Among qualitative olfactory dysfunctions 36, 37 are parosmia (also called "troposmia") which occurs in the presence of an odor, and phantosmia which refers to an olfactory perception when no odor source is present (olfactory hallucination); they may occur intermittent or constant. Parosmia is typically associated with reduced olfactory sensitivity 11. Interestingly, almost none of parosmic patients report to perceive pleasant odors; the large majority, if not all, of these patients finds these sensations to be unpleasant, sometimes even faecal. Accordingly, signs of depression have been reported to be present in approximately two thirds of patients reporting qualitative olfactory dysfunction 11.
Approximately two thirds of patients with olfactory loss not only complain of decreased olfactory function, but also of taste loss, and approximately 10% of patients with olfactory disorders complain of gustatory loss only 10. However, a major decrease in gustatory function is only present in less than 5% of patients with chemosensory disorders 10. More recent data, however, indicate that olfactory loss is also accompanied by a gradual loss of both trigeminal 38, 39 and gustatory function 40. While the reason for this is unclear, it has been shown that the chemical senses exhibit mutual interactions, both at peripheral and central nervous levels 41-45.
continue >> |
printable version > 
