February 2002
Have you ever wondered what your life would be like if you did not have one of your five senses? At some point in our lives we have all seen a blind or deaf person but how often do we wonder what it would be like if we were in their shoes? Many people take their senses for granted, not giving much thought to the fact that something as simple as bumping your head the wrong way or getting a cold could take away your sense of smell forever. Anosmia is the total loss of the sense of smell and affects approximately two million Americans (Wuensch, 2001). Of all the five senses, smell seems to be the least appreciated due to our society's beliefs that sight and hearing are more important for survival (Gillyatt, 1997). For most people, once they start to notice a decrease in their hearing or sight they go to the doctor almost immediately to fix the problem. However, because the sense of taste and smell are so closely related, many people attribute the problem to a lack of taste and do not see their doctor until the damage is irreversible (Thomson, 2001). Anosmia is a condition in which although there are mild cases, more serious cases do exist which may jeopardize the victim's life. This disorder not only affects the person's life and safety, but also has psychological effects as well . In any case, anosmia should not only be taken seriously, but resaerch should be continued in the hopes of finding better treatments.
Lacking a sense of smell has similar psychological effects as those related to losing one's sight or hearing. For example, many blind people feel cut off from the world and isolated. This case is also seen in many people with anosmia. Some people with anosmia feel physically and socially vulnerable as well as victimized (Toller, 1999). Others feel unhappy with the inability to detect pleasurable food smells, and as a result many anosmics develop eating problems and even lose interest in eating (Toller, 1999). On the other hand, some people will constantly eat trying to satisfy their need for taste and put on an excess of unhealthy weight. Another issue to consider when discussing anosmia is safety. Probably one of the most important safety aspects of all people is the ability to smell fire. Anosmics may be in greater danger with these situations. They should be encouraged to check the batteries in their smoke detectors often, and consider having their natural gas checked by a professional monthly, since people with anosmia would not be able to detect the smell of a gas leak (Gillyatt, 1997). When using cleaning products and paint supplies, they should be reminded to keep the room adequately ventilated to prevent becoming woozy or nauseated, which could lead to another dangerous situation. Some other less serious aspects to take into consideration are their daily routines, such as personal hygiene or preventing food from spoiling (Thomson, 2001). One way to prevent food poisoning is to write the dates on leftover food or to throw it away if they are not sure.
Anosmia has many causes ranging from a minor head injury or cold to more serious illnesses like Alzheimer's disease. The following are examples that fall on the less serious side of the spectrum. Age is one factor that not only affects your sense of smell but the other four senses as well. It has been estimated that "half of everyone age 60 and over has some loss of smell" (Thomson, 2001). While age plays a role in anosmia it is also normal to notice a lack of smell due to a cold, allergies, or other minor viral infections. In some cases, cold viruses can damage the olfactory system causing the loss of smell to last even after the cold is over (Thomson, 2001). In this instance, since there are no proven treatments for reversing olfactory nerve damage, the patient's best hope may be spontaneous recovery (Thomson, 2001). Jobs are also risk factors for anosmia. For example, many fire fighters experience a loss of smell due to constant exposure to toxic chemicals and smoke. This example holds true for anyone in a profession who works with harsh chemicals on a regular basis.
While the risk factors above may not seem very serious, there are other issues that in some cases are life threatening. For example, one of the first things most doctors eliminate is the occurrence of head trauma due to the fact that "about 10% of people with a head injury experience some loss of smell" (Thomson, 2001). Head injuries can cause the brain to jolt which thins out the delicate axons that run from the olfactory neurons to the brain (Wuensch, 2001). In many cases, not only the location of the injury, but also the degree of the trauma is important. The loss of smell is more likely to occur if the person lost consciousness or fractured their skull during the accident (Ogawa and Rutka, 1999). Many times people will regain their sense of smell after the axons regenerate; however, the condition can also be permanent. Obstructions and inflammation in the nasal cavity also effect one's sense of smell. One type of obstruction in the nasal cavity is called nasal polyps. This obstruction can occur when the lining of the sinuses swells up and protrudes into the nasal cavity (Thomson, 2001). More serious causes of anosmia are certain brain pathologies like Alzheimer's disease. Morgan (2000) states that patients diagnosed with Alzheimer's disease have plaques, tangles, and cell loss in the areas of the brain associated with olfactory function. In the case of Alzheimer's disease, researchers have used fMRI's to observe the extent of activity when specific brain regions are activated by olfactory stimuli (Andrew et al., 2001). Their findings have suggested that, compared to younger people, elderly people with Alzheimer's have decreased activation in the olfactory cortex located in the right side of the brain (Andrew et al., 2001). However, the left side of the brain reached significant levels of activation(Andrew et al., 2001). These results have also been seen in other research cases. For example, researchers in New York used smell tests and fMRI's to locate the areas which were affected by odors (Thomson, 2001). They found that while Alzheimer's patients had difficulty identifying odors and they also had damage on the right side of their brain (Thomson, 2001).
The amount of research being done in the area of anosmia and other olfactory disorders is very small. In the past, researchers have used such brain imaging technologies as fMRI's, PET scans and CT scans to observe different areas affected by olfactory dysfunctions. As pointed out above, the use of fMRI's is useful in detecting anosmia in such disorders as Alzheimer's disease. By using the paired-subtraction technique researchers are able to identify the areas related to olfactory functions and how these areas are affected by Alzheimer's and even Parkinson's disease. Such researching groups as Andrew et al. used fMRI's to observe areas of the brain in twelve Alzheimer's patients (Andrew et al., 2001). In the present, researchers are still exploring how anosmia is related to the brain pathologies of Alzheimer's and Parkinson's disease. "Their work could lead to smell-based diagnostic tests for these diseases, as well as fresh insights into how they develop" (Thomson, 2001).
Anosmia is a difficult disorder to treat due to the lack of informative research. The less serious cases have a higher chance of being treated and cured. For example, antihistamines will help clear a stuffy nose during allergy season and most cold medicines also clear the nasal passages. For certain infections, such as sinusitis and upper respiratory infections, prescription drugs usually result in the best treatment. However, although people can regain smell, permanent damage can still result even in these light cases. When moving on to the more serious cases of anosmia, like Alzheimer's or Parkinson's disease; treatments become less and less reliable due to the minimal amount of research in this area. In one research study, it was found that both Parkinson's and a loss of smell had been traced to low levels of dopamine (Thomson, 2001). However, they also found that when patients were given levodopa, a substance that increases dopamine levels, the sense of smell did not improve. Although trial and error research studies usually provide negative results, they still aid in the study of anosmia and move researchers closer to a cure.
The MRI studies performed by the researchers above provide useful information about the effects of anosmia, especially in Alzheimer's disease. For this reason, looking further into other diseases such a schizophrenia, epilepsy, or even cancer may provide further evidence of damaged olfactory functioning. While antihistamines and prescription drugs provide relief of temporary symptoms, anosmia is a serious disorder that should continue to be researched to foresee treatments in the serious conditions as well. Finding treatments for anosmics who have more serious damage could not only save lives, but also help them regain a sense of worth and relieve the depression that accompanies this disorder.
Andrew, Bryant, Critchley, Fukuda, Howard, Jackson, Ouldred, Suckling, Suzuki, Swift, & Williams (2001). Functional magnetic resonance imaging of odor indentification: The effect of aging. Journals of Gerontology, 56A(12), M756-760.
Gillyatt, P., (1997). Loss of smell: when the nose doesn't know. Harvard Health Letter, 22, 6-8.
Morgan (2000). Olfactory event-related potentials in Alzheimer's disease. Dissertation Abstracts International, 61(5-B), 2773.
Ogawa & Rutka (1999). Olfactory dysfunction in head ingured workers. Acta Oto-Laryngologica, 119(540), 50-57.
Thomson, Corp. (2001). Senses- Loss of Smell: How it happens and what it means. Harvard College.
Toller, Van (1999). Assessing the impact of anosmia: review of a questionnaire's findings. Chemical Senses, 24(6), 705-712.
Wuensch, L. (2001, November 10). How frequent is anosmia? [Online]. Available: http://www.personal.ecu.edu/wuenschk/anos-freq.htm