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Nasal Dysfunction

About the Sense of Smell

Anatomy of the Nasal Cavity

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Physiology of the Nose

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Types of Nasal Dysfunction

Vocabulary of Smell Loss

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• Osme - This is the Greek word meaning odor, and is the stem word for many medical definitions relating to smell.
  
• Normosmia - means a normal sense of smell.
  
• Anosmia - means complete loss of the sense of smell.
  
• Hyposmia - is the partial loss of the sense of smell.
  
• Parosmia - means a perversion or distortion of the sense of smell. An example of this would be an individual who sniffed one odor but felt they smelled another, very often an unpleasant odor, such as the smell of something decaying. Phantosmia is a situation in which one smells an odor for which there is no stimulus; hence it is a phantom smell.
  
• Dysosmia - is any defect or impairment in the sense of smell, and therefore is a collective term which would include hyposmia, anosmia, parosmia, and phantosmia. We will sometimes use it at the Nasal Dysfunction Clinic to describe unpleasant odors, i.e. parosmia and phantosmia.
• Presbyosmia - is a decrease in the sense of smell associated with aging.
• Smell Loss -
• Post traumatic anosmia is a very common condition. It occurs in as many as 30% of individuals who suffer head trauma. It is more common when the head is hit either from the front or the back but it does occur occasionally when the head is struck from the side. There is scientific controversy as to the exact cause of post traumatic anosmia. The prevailing theory is that when one strikes one's head, the brain moves within the skull. The olfactory nerves are very delicate and very short. They course from the top of the nose to the top of the brain and are easily stretched or torn. Injury to this nerve, also known as the first cranial nerve or the olfactory nerve, will cause a loss of the sense of smell. If the nerves are stretched, olfaction will return and this it does in 30% of post traumatic anosmias. If the nerves are torn, the anosmia is permanent and will not return. In those cases in which the loss is temporary, recovery is experienced in the majority of patients by one year. If at one year there is no recovery, then recovery becomes highly unlikely. Phantosmia, which means phantom smells, is common in post traumatic anosmia. While troublesome at first, it dissipates with time and ultimately disappears completely.
• Viral induced anosmia is another common cause of smell loss. This occurs when a viral infection, like the flu or a cold, involves the cells of the olfactory epithelium. For unknown reasons, the viral particles destroy the normal functioning of the nasal olfactory cells and there may be a total or partial loss of the sense of smell. In some cases this resolves over time and others the loss is more severe and the recovery substantially less or even none. Post viral anosmias are often associated with paraosmias. Paraosmia is a condition in which in the presence of one odor, like perfume, garlic or any of the other thousands of odors we smell on a daily basis, causes the brain to think it has smelled something different, unfortunately generally an unpleasant odor. Paraosmias can be very disturbing at first. Fortunately they virtually always dissipate with time. It is not really known how much post viral anosmics recover. If you speak with them many years later they will tell you they are doing fine, they are tasting food, and while things aren’t really the way they once were, life and the general balance of things seems satisfactory. We suspect that some of this is recovery and some of it is accommodation to the new olfactory level.
• Inflammatory anosmia is the third common cause of smell loss. Inflammation in the nose, such as caused by chronic sinusitis, allergic rhinitis, and a host of other problems, impairs the body’s ability to smell. Some believe this is an obstruction to air flow so that odorants do not reach the olfactory epithelium. Others believe that there are in fact chemical changes associated with the inflammation that alter the olfactory epithalamiums response to odorants. Inflammatory induced anosmia improves with treatment. It certainly improves with large doses of steroids. Unfortunately these are not healthy to take on the long term but are a very good test to confirm that the smell loss is inflammatory in origin and therefore potentially reversible. There is often discussion whether a deviated septum or some other anatomic abnormality will cause smell impairment. Our feeling is that it does not. Having a septoplasty or other nasal surgery with the hope that it will improve olfaction is probably not wise. In some people there are small growths that occur in the nose, these are called polyps. Once they fill the upper regions of the nose in the olfactory cleft, then air does not reach the olfactory epithelium and olfaction will diminish. Whether this is anatomic or whether this is chemical or inflammatory is not known.
• Congenital anosmia is often familial, meaning that it can be transmitted genetically. People with congenital anosmia have no ability to smell. They do fine with life and with foods. They mostly miss the danger warnings of nasal olfaction.
• Toxic induced anosmia. There are a number of toxins which will cause smell impairment. In the past and long before OSHA protected workers, long time exposure to solvents, photographic developing chemicals, and formaldehyde were known to cause smell impairment. Today this type of long term chronic exposure is rarely seen, at least in the western world. Short term exposures such as chemical burns from ammonia or gasoline or certain zinc compounds still do occur. When these exposures are substantial, smell loss, partial or total, temporary or permanent, do occur.
• Psychological Issues - A variety of psychiatric conditions can also adversely affect one’s smell perceptions. The most common conditions are depression, hysteria, and schizophrenia. Many of the dementias are associated with olfactory loss. Alzheimer’s is the most common and the best known. Fortunately, the Alzheimer patient doesn’t seem to be aware of or mind the olfactory loss, so that while the loss is substantial it is not a problem for the patient. Lastly, there is great discussion about the differences between men and women and the different ages. It does seem that olfaction diminishes with time, however, the loss is generally not substantial. There are many octogenarians with an excellent sense of smell. Those who smoke may lose it faster. Generally speaking, women have a better sense of smell than do men; they use it more frequently and ar emore upset with its loss.