Treatment of Parosmia

    On the morning of the 9th of October, 2002, I had a most pleasant and interesting conversation with Dr. Dimitri Pitovski, who was then the director of the Taste and Smell Center at Wake Forest University.  I have since lost contact with Dr. Pitovski, and the Taste and Smell Center appears to have disappeared as well.  I have found web documents identifying him as the CEO of Allergy Centers of America.  Our conversation included a discussion of the treatment of Parosmia. Although I have never been a victim of parosmia, and hope I never am, I have corresponded with many persons who have suffered this condition, and I found Dr. Pitovski's discussion of the topic fascinating -- so fascinating that I cannot resist sharing parts of it with you.

    The traditional wisdom is that parosmia results from an abnormality within the brain. Accordingly, the most common treatments for parosmia are directed towards brain function. A rather radical surgical approach is destruction of the olfactory bulb, which, of course, renders the patient anosmic. Some medical treatments involve drugs that are known to have effects on the brain. When these drugs are somewhat effective, that is often interpreted as evidence supporting the contention that parosmia is caused by brain dysfunction. However, these drugs generally do have peripheral effects as well (effects on neurons outside of the brain), and it is possible that their effectiveness is due, in part or in full, to those peripheral effects. Also, one should consider the possibility that a condition which is caused by a peripheral abnormality could be effectively treated with manipulation of brain function (and vice versa).

    There is some evidence that parosmia may, at least in some patients, be caused by dysfunction of olfactory neurons whose axons run from the olfactory mucosa (high in the nasal cavity) to and through the cribriform plate (into the brain). If dysfunction of these neurons is, in fact, responsible for parosmia, then one interesting potential treatment is simply to remove them surgically. Research on the effectiveness of this potentially useful treatment is taking place in at least two medical centers in the United States. The surgery is described as "minimally invasive," with the patient being discharged from the hospital the day after the surgery. As with any surgery, there are some risks -- for example, there is a risk of causing a leak of cerebrospinal fluid. Once detected, such leaks can be surgically patched. Every time I have sinus surgery I face this risk too.

    So, what should one expect to be the result of removal of the diseased olfactory axons from the nose of a person with parosmia. The immediate effect to be expected is that the person will no longer have parosmia, but will have anosmia. This may not seem like much of an improvement, but for the patient with a long-standing case of disabling parosmia and little hope for ever having normal olfaction restored, trading parosmia to anosmia may well be a blessing. However, there is the possibility that the olfactory connections between the nose and the brain will, in time, be restored following such surgery.

    The most obvious candidate for the surgical treatment just described would seem to be the person whose parosmia arises from dysfunction in only one side of the nose. For such a person, even if the surgery permanently destroyed the sense of smell on that side of the nose, relatively normal olfactory function should result from the intact olfactory mechanism in the other side of the nose. The person who has smell distortions in both nostrils is more problematic. Should one consider such a patient a candidate for this surgery? Conducting the surgery on just one side would be little help, and conducting it on both sides could lead to permanent anosmia (or could lead to temporary anosmia followed by restoration of normal olfaction). IMHO, when the patient's physical and mental health is seriously affected by such bilateral parosmia, this surgery might be considered, especially when the prognosis for spontaneous recovery or effective treatment by other means is very poor.

    The minimally invasive surgical procedure described above has also been performed at the University of Nebraska Medical Center. With the help of one of my correspondents, I located an article by Dr. Donald A. Leopold (at the Nebraska Medical Center) and others. Here is a summary of that article:

    The subjects of the study were 8 patients with parosmia for whom blocking the affected nostril(s) would stop the unpleasant odor (some individuals with parosmia/phantosmia experience the unpleasant odor whether or not there is air flowing through their nostrils). Each of these patients had experienced parosmia for at least 4 straight years. The surgery involved removing the olfactory mucosa (right up against the cribriform plate, on the other side of which is the brain), taking care not to create a CSF leak (patching it if necessary) and not to disturb the olfactory neurons within the brain. Apparently the olfactory tissue is tough, not easily cut. Although the surgery was intended to relieve parosmia by eliminating all possibility of olfactory reception within the affected nostril, these patients recovered their ability to smell things -- apparently either some of the olfactory neurons were spared or there was regeneration of olfactory nerves. Amazing!

    There is a link to an abstract of the article below, but I recommend that you find the full text article and read it. It is a good read. The reference is: Leopold, D. A., Loehrl, T. A., & Schwob, J. E. (2002). Long term follow-up of surgically treated phantosmia. Archives of Otolaryngology - Head & Neck Surgery, 128, 642 - 647.

    I received a letter from a woman whose Mom suffered from phantosmia for over twenty years and was able to get no relief from any of the doctors she saw. Her daughter found this page and passed it on to her Mom, who had the surgery at Wake Forest in the summer of 2003. Her daughter reported to me that Mom is now finally free of the phantom smells.

    In March of 2011 a correspondent suggested that intranasal zinc solutions might be an alternative treatment for hyperosmia or parosmia.  Although that is an interesting suggestion, I have never heard of zinc being used in that way.

 


 

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This page most recently revised on the 22nd of November, 2013.