Disorders of Smell
Disorders of olfaction are infrequent but a complete loss of smell reduces the quality of life significantly. The perceptions of smell and taste are often combined. Taste only differentiates four qualities: sweet, sour, salty, and bitter. Olfaction is the sense that brings you all those wonderful flavors in between that you find in food and drink. Without smell you wouldn't be able to tell the difference between a piece of strawberry candy and grape candy; it would only be sweet with no distinction of actual flavor.
Losing your sense of smell can be dangerous as well as just inconvenient. Without smell, you would not be able to distinguish toxic substances, you would be unaware of smoke from a fire, and you would not be able to recognize the odor of spoiled food.
Disorders of smell can be classified as either hyposmia (a decrease in sensitivity) or anosmia (the complete absence of smell). There are many causes for smell malfunctioning.
Disturbances of olfaction can be due to respiratory disorders such as nasal polyps, a deviation of the nasal septum or chronic sinusitis. The conditions can reduce airflow through the olfactory cleft at the roof of the nasal cavity. They can be corrected by modern endoscopic surgery of the nose (Huttenbrink 1995).
Epithelial disorders involving the sensory cells are most often caused by viral infections or toxic destruction of the sensory epithelium (solvents or gases). Heavy metals, benzene and various kinds of industrial dusts are also damaging to these areas. Epithelial disorders are cured only rarely. Corticosteroids, zinc, and vitamin A are tried frequently (Huttenbrink 1995).
When someone has a cold, the nasal membranes swell and the amount of mucus produced increases. This results in a decrease in odor sensitivity. Allergies and rhinitis, an infection in the olfactory membrane, also may cause a loss of smell. Impairments in smell can also be caused by head trauma. In fact, in 5-10% of all head trauma cases some sort of smell dysfunction occurs. The incidence increases with the severity of the trauma and with the presence of amnesia (Gordon 1982).
Disorders of olfaction can also be an early sign of certain neurological diseases such as Parkinson's or Alzheimer's. In-depth examination of olfaction can contribute to their early diagnosis. However no specific treatments have yet been identified (Huttenbrink 1995).
Disorders of olfaction can also be congenital (people are born with it). In these cases, people can't smell or taste beyond the 4 basic tastes, but they never really knew what it was like to begin with.
In people who have anosmia, the damage is usually permanent. However with hyposmia, the sense of smell can be either entirely or partially recovered.
Altered Perceptions of Smell
Many pregnant women report an altered sensitivity to smell. Once pleasant scents suddenly seem unpleasant. The reason behind this is unknown, but it has been discovered that the olfactory membrane does swell during pregnancy. Altered smell perception has also been associated with epilepsy. Some have reported that right before an epileptic seizure, they experienced an olfactory hallucination. Some have even had hallucinations days before an epileptic event. It is usually an unpleasant odor that they perceive, either organic, such as decay, or chemical such as petroleum. Interestingly, certain odors have also been known to stop a seizure (Stoddart & Whitfield 1984).
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