The Consequences of Losing Sense of Smell and Taste following a Traumatic Brain Injury
by Barry L. Beyerstein Ph.D.
Head injuries may cause problems with ones sense of smell. As the British smell researcher, Steve Van Toller put it in a recent article documenting the difficulties anosmic patients face:
The inability to detect odours, anosmia, can cause profound psychological effects resulting in feelings of physical and social vulnerability and victimization. In addition, there may be unhappiness related to the loss of the ability to detect pleasurable food smells and, as a consequence, anosmics may develop problems relating to eating. These profound effects arise from a condition which can have rapid onset and a very poor prognosis for recovery, and are largely treated with a lack of sympathy and indifference by people with normal olfactory ability.
As Van Toller concluded, Smell is a sense whose value seems to be only really appreciated after it is lost.
A particularly articulate patient of the neurologist Oliver Sacks described the impact of a head injury that rendered him suddenly anosmic in the following way:
"Sense of smell?...I never gave it a thought, You dont normally give it a thought. But when I lost it-it was like being struck blind. Life lost a lot of its savour-one doesnt realize how much savour is smell. You smell people, you smell books, you smell the city, you smell the spring-maybe not consciously, but as a rich unconscious background to everything else. My whole world was suddenly radically poorer...
Research has shown that this kind of olfactory malfunction can have negative implications for the personal safety of those with diminished ability to smell. It can affect ones ability to recognize and avoid tainted food. It can affect ones ability to correctly identify early warning signs such as smoke and or the presence of overheating appliances , toxic chemical spills, or escaping natural gas or motor fuel, for instance, would be compromised if one were to misidentify these odours. Anosmia may also affect one socially such as, for instance, if one fails to remedy odours on his person, shoes or clothing, or in his dwelling, that might be offensive to others.
Furthermore, there is growing evidence that the sense of smell in humans, once thought to be largely vestigial, is involved in a number of important physiological and social processes. In my course on olfaction at Simon Fraser University, I spend a considerable amount of time discussing other disruptions of normal living experienced by those who are suddenly rendered wholly or partially anosmic by accidents or disease. Because of the information from the sense of smell goes to the older, deeper parts of the brain (the limbic system ) whose activities we are not consciously aware of, people are rarely cognizant of all the important vegetative, motivational, and emotional functions affected by smell - until they lose it, that is.
It is now well documented that smell is an important regulator of sexual behaviour. Olfactory deficits can adversely affect sexuality in a number of ways. Smell also has significant effects on mood and general arousal, and olfaction has also been found to be involved in the regulation of many processes related to bodily homeostasis and overall health. For instance, smell is an integral component of the systems that regulate appetite, energy balance, hormonal cycles, and body weight. Changes in hedonic value of smell of food are an important way the body signals hunger and diminishing pleasurableness of the smell of food is one of the first cues to satiety. If we were to continue to eat until the food was digested and the nutrients distributed to the cells of the body, we would grossly overeat each time we started. It is largely due to the fact that food starts to have a negative hedonic value as we fill up, that we terminate each eating episode.
In addition, smell has been shown to play a much bigger role in certain kinds of learning and social behaviour that scientists had previously suspected. It has also been found to be involved in various aspects of kin-recognition that may be socially important, such as parent-offspring bonding. The result of the new research is a growing recognition that loss of the sense of smell is far more than a trivial inconvenience. A person with a malfunctioning olfactory system could thus be at a disadvantage in many aspects of life, over and above those obviously related to the esthetic values of smell, its overt social consequences, or its important alarm functions.
1 S. Van Toller (1999) Assessing the Impact of Anosmia: Review of a Questionnaires Findings. Chem. Senses. 24: 705-712. 2 O. Sacks (1985) The dog beneath the skin. In: The man who mistook his wife for a hat. New York: Summit Books/Schuster & Schuster Inc.
Dr. Barry Lane Beyerstein is a professor with the Faculty of Psychology at Simon Fraser University, Burnaby, B.C., Canada. He conducts clinical olfactory assessments of persons with complaints surrounding taste and smell. Dr. Beyerstein is accomplished in many areas of specialization including brain behaviour relationships and the psychophysiology of olfaction, pain and vision.
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