By Russell J Otto, MD, FACS
The sense of smell is one of the four human special senses. The special senses determine, in many ways, how we interact with our environment in our daily lives. While the sense of smell typically is ranked behind sight, hearing and taste in importance, problems with smell can adversely impact one’s quality of life. Anosmia is the lack of an ability to smell or detect odors. The quality of smell can also be reduced, heightened, or distorted.
Anosmia can be caused by a variety of conditions. Depending on the condition, the duration of anosmia may be temporary or permanent. Only a small area on either side in the roof of the nasal cavity, about the size of a folded postage stamp, is involved in the detection of odors. A nerve from the brain, one for each side of the nose, pokes its fibers through the porous bone of the skull base to place smell sensory receptors in the roof of the nose.
Conditions that lead to blockage of airflow to this portion of the nose typically result in temporary anosmia. The most prevalent is the common cold. The nasal congestion diminishes the sense of smell that we have all experienced. Another common cause is nasal polyps due to allergy, and sinusitis. When properly treated, the polyps and inflammation can be reduced to help restore smell perception.
Conditions associated with degeneration or damage to the nerve fibers in the roof of the nose lead to permanent anosmia. Head trauma, exposure to toxic vapors such as glues and tobacco, and overzealous use of over-the-counter vasoconstrictor nasal sprays are examples of conditions that damage the nerve fibers. Degeneration of the fibers occurs with normal aging, but can signal conditions such as Parkinson’s and Alzheimer’s diseases or a tumor.
Anosmia can lead to secondary effects like depression or weight loss. It can also become dangerous if you are unable to detect the presence of smoke, a gas leak, or rotten food. A thorough evaluation by your physician can help you sort through many of these issues.