日鼻誌４７!：５１～５２，２００８

特別講演２

TREATING DYSOSMIA, FROM SALINE TO SURGERY

Donald A. Leopold, MD, FACS

University of Nebraska Medical Center, Omaha, Nebraska, United States of America

The sense of smell begins with airflow through the nose. The exact path of this airflow has only recently been investigated. Some of this data comes from models, both life size and enlarged models using measurements of airflow. Additional information comes from computerized airflow models of the nasal cavities.

The neural pathways of olfaction begin with the olfactory receptors high in the nasal cavity. After transduction from the chemical to the electrical information, this information is transferred through the olfactory bulb and into the central brain.

Patients typically present with one of three different types of dysosmia. The first is simply a decreased ability to perceive smells（hyposmia and anosmia）. The two remaining types of dysosmia relate to distortions of perceived smells. One of these（parosmia）is a distortion of smell odorants that are actually in the environment. The third type is theperceptionofanodorwhenthereisnoodorantintheenvironment（phantosmia or hallucination）.

The clinical task of the physician seeing these patients is to decide on the etiology of the problem and to recom- mend therapy if possible. The clinical history is one of the best tools the clinician has, but the physical examination, sensory testing and imaging can also be helpful. Diagnostic categories for these patients are many, but the most com- mon include nasal inflammatory disease for about a third of these patients, the losses that occur after an upper respira- tory infection in about 25 percent of the patients and head trauma in about 15 percent of patients. Depending on the types of patient groups being examined, aging can also be a major concern. Loss of smell due to congenital or toxic causes typically is less than 5 percent.

The history for people who have lost their sense of smell includes age, timing, gender, diet and medication use. The age of the patient will help to determine if there is an age―related olfactory loss. Those individuals who lose their sense of smell after an upper respiratory infection tend to be almost three quarters female. Timing can be important, such as losing sense of smell after head trauma or the short one weekend loss of smell associated with post URI olfactory loss. Changes in diet, such as the inability to perceive tastes in addition to smells, can also be useful.

Sinonasal inflammatory disease can cause a “conductive” loss whereby odorants are unable to reach the olfactory receptors due to mechanical blockage. There may also be some inflammatory disease of the olfactory neuroepithelium with this condition.

The loss seen after an upper respiratory infection typically has a sudden onset over several days and has about a 25 percent recovery rate. The loss of smell seen after head trauma may be due to tearing of olfactory filaments as they travel from the nose into the cranial cavity, and recent data suggests there may be frontal brain trauma. There is typi- cally only about a 10 percent recovery of smell after head trauma loss.

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The loss of smell associate with aging typically occurs in the sixth or seventh decade, and can result in an individ- ual having almost 50 percent loss compared to what they had in the prime of their adulthood.

Distorted perceptions of smell can be quite annoying to patients, and typically generate more symptoms than those patients who have simply lost their smelling ability. These distortions can take a number of characters, but are often described by patients with similar words such as burned rubber, foul meat, burned toast. It is helpful to know whether other smells are masked by these unpleasant smells, and whether it affects one or both nostrils.

The physical examination on someone for an olfactory problem should include nasal endoscopy, examination of the tongue, trigeminal nerve evaluation and a general psychiatric status evaluation. Clinical testing of these individuals must include olfactory and, if needed, taste tests. Imaging with either CT or MRI scanning may be helpful, especially in those individuals whose olfactory loss did not seem to fit a clinical pattern. Unilateral testing of smelling ability can also aid in the diagnosis and treatment. Electrophysiologic testing has been developed with the evoked potentials or electrodes placed on to the olfactory epithelium, but these techniques are still limited largely to research.

Treatment of individuals who have lost their sense of smell should include psychological support for them since they often have not been able to receive good information. They should also receive information on how to protect themselves, such as with a smoke detector and avoidance of explosive gases. For those individuals who have a decreased olfactory ability, treatment can be effective if they have nasal disease and using the many therapies available, including antibiotics, topicals, steroids, surgery, etc. can be useful. All others who have lost their sense of smell for neural reasons, such as after an upper respiratory infection, head trauma or aging, cannot currently be helped. One recent report suggests that systemic steroid therapy may be helpful, but this has not been confirmed with other studies. Therapies that have been shown not to improve olfaction include administration of zinc, Vitamins B6 and B12, Vitamin A and alpha lipoic acid.

Individuals who have a distortion of their sense of smell can be reassured since the majority of them will improve typically within a year. In those individuals whose olfactory condition can be improved by blocking their nasal airways, nasal saline or decongestant drops can be useful. For those rare individuals who cannot be helped with any other techniques, I have designed a surgery to remove the olfactory epithelium using endoscopic techniques. This is an approach that is quite difficult and should only be performed by experienced surgeons. I only will operate on one side at a time and will cut as many as the fila olfactoria as possible. A mucosal graft is placed after this incision because a third of them will have a cerebral spinal fluid leak.

Using these surgical techniques, we have been able to treat 22 patients with phantosmia and one with parosmia distortion. All but three of these have been relieved of their bad smell. In half of these patients, the smelling ability has remained unchanged or has improved after the surgery in spite of the attempts to completely destroy the smelling ability.

In summary, it is important to consider the complaints of each patient individually and to listen well to their concerns. With surgical and medical therapies, it is possible to treat olfactory distortions and patients should be given hope that this is a treatable condition.

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