Disorders of Taste and Smell, Part 2: Impaired Smell

Impairment of the senses of taste and smell are much more common that most people realize. The National Institutes of Health reports that over 200,000 doctor visits each year are for a sensory problem such as a taste or smell disorder. Their statistics also indicate that approximately 25 percent of Americans have lost the ability to taste and 1-2 percent of Americans younger than 65 have lost their sense of smell to a significant degree. This percentage goes up even higher in the older population with nearly half of individuals 65 to 80 years old losing their sense of smell. The two senses, taste and smell, share certain attributes. For example, flavors are recognized mainly through the sense of smell rather than taste. Also, taste and smell receptors are the only two types of sensory cells that are replaced regularly throughout a person's life. Sometimes the underlying cause for the loss of one or the other of these senses is the same.


How does our sense of smell work? Smell, like taste, is part of our chemosensory system. That is, sensory cells concentrated in an area high inside the nose are able to detect the odors from tiny molecules that are released from foods, flowers, and other substances. These sensory cells are actually specialized nerve endings that connect to the area of the brain responsible for identifying smells. Many of us have noticed how the taste of food is diminished when we have a cold. This is actually due to a temporary loss of the ability to smell because the odor of the food cannot reach the sensory cells in the nose.

What are smell disorders? Smell (or olfactory) disorders are those that involve loss of the ability to smell or an alteration in the way odors are perceived. Recent surveys indicate that up to 2.7 million Americans have some type of problem with their ability to smell. These disorders include hyposmia, a decreased ability to smell, anosmia, an inability to smell, parosmia, a distorted perception of smell, and phantosmia, the perception of a smell that isn't present at all. Smell disorders, although seemingly benign, can have serious repercussions. Without the sense of smell we lose an early warning signal for dangers, such as spoiled food, toxic fumes, or the smoke from a fire.

What causes impairment in the ability to smell? The four main causes of smell disorders are: (1) head injuries, (2) viral upper respiratory tract infections, (3) conditions affecting the nasal passages, including nasal polyps and sinusitis, and (4) smell disorders associated with aging or neurological illnesses such as Parkinson's disease or Alzheimer's disease. Less common causes include cigarette smoking, radiation therapy for head and neck cancer, hormone disturbances (especially from estrogen deficiency associated with menopause), certain medications, and rarely, brain tumors.

How are smell disorders diagnosed? The first step in determining the cause of a smell disorder involves taking a thorough history that includes smoking habits, accidents, medications being taken, recent infection, and specific nasal complaints (obstruction, runny nose, facial pain, etc.). A careful examination of ears, nose and throat with special attention to the nasal passages for evidence of polyps or other obstructions that could block odors from reaching the olfactory receptors is the next step. In situations with no apparent cause, an Otolaryngologist, specializing in diseases of the ear, nose and throat, may need to be involved in order to make the diagnosis. Special tests to diagnose smell disorders include "smell tests" and imaging studies (CT, MRI, etc.) to evaluate the brain or nasal cavities. Special attention is appropriate with the complaint of "phantosmia", also known as an olfactory hallucination. This is a smell disorder characterized by detecting smells that are not actually present. Although rare, phantosmia can be associated with several serious problems, including temporal lobe seizures, brain tumors, migraine, Parkinson's disease and stroke.

Can impaired smell disorders be treated? Treatment options for smell disorders are limited. No effective treatment is yet available for aging-related causes. With trauma-related loss of smell, only 10-20 % of people affected will spontaneously regain some ability to smell. Fortunately, smell receptors do possess some ability to regenerate themselves if they are damaged. The best results of treatment apply to those with nasal-related causes. Use of antihistamines or intranasal steroids (Flonase, Nasonex, others) may help in inflammatory conditions of the nose, such as allergic rhinitis. Impaired smell from sinus or upper respiratory tract infections generally improves when the infection resolves. When responsible for the loss of ability to smell, surgical removal of nasal polyps can be curative. Stopping or substituting a medication that is responsible for the impairment can restore the ability to smell as can stopping cigarette smoking.

Smell and taste disorders can markedly affect the quality of life. Since most of these disorders can be attributed to a specific cause, and with treatment options available in many cases, these are not problems that necessarily have to just be "lived with".

Disorders of Taste and Smell: Part 1

Impairment of the senses of taste and smell are much more common than most people realize. The National Institutes of Health reports that over 200,000 doctor visits each year are for a sensory problem such as a taste or smell disorder. Their statistics also indicate that approximately 25 percent of Americans have lost the ability to taste and 1-2 percent of Americans younger than 65 have lost their sense of smell to a significant degree. This percentage goes up even higher in the older population with nearly half of individuals 65 to 80 years old losing their sense of smell. The two senses, taste and smell, share certain attributes. For example, flavors are recognized mainly through the sense of smell rather than taste. Also, taste and smell receptors are the only two types of sensory cells that are replaced regularly throughout a person's life. Sometimes the underlying cause for the loss of one or the other of these senses is the same.

How does our sense of taste work? As everyone knows, taste starts at the tongue. Contrary to popular belief, however, there are not specific areas of the tongue assigned to certain tastes. Rather, the entire tongue has receptors in the taste buds capable of tasting the 5 recognized tastes. These are: sweet, sour, salty, bitter, and the newest defined taste of umami (savory). Taste occurs when the sensory cells in taste buds detect certain chemical substances that are released from the foods or beverages that we consume. These receptors send signals via specialized nerves to the area of the brain that is responsible for identifying particular tastes. In addition to the receptors on the tongue, there are also nerve endings in the nose, mouth, and throat that contribute to our sense of taste. These play a role in detecting the 'coolness' of mint, the 'heat' of chili peppers, and the texture of foods.

What is a taste disorder? Taste disorders are conditions in which the perception of taste is altered or lost. 'Dysgeusia' is a taste disorder in which taste is distorted or an unpleasant taste persists for no apparent reason. Another taste disorder is called 'hypogeusia' in which perception of one or more of the 5 tastes is diminished. Complete absence of taste (ageusia) is rare. Because of the important role that the sense of smell assumes in detecting flavors, many times when people think that they have lost the ability to taste, their sense of smell has actually been affected.

What causes taste disorders? Most taste disorders develop after an injury or illness. Some of the common causes of impaired taste are:

• Upper respiratory tract infections, primarily due to the effect on the nasal passages impairing the ability to smell and detect flavors
  
  
• Chemotherapy induced damage to the sensory cells in the oral cavity and tongue
  
  
• Radiation therapy for cancers of the head and neck
  
  
• Vitamin/mineral deficiencies, especially Vitamin B-12 and Zinc
  
  
• Head injury with damage to the area of the brain responsible for taste
  
  
• Medications including lithium, certain antibiotics, blood pressure drugs (captopril, ACE inhibitors, diuretics), and seizure medications (carbamazepine, phenytoin)
  
  
• Poor oral hygiene and dental problems
  
  
• Cigarette smoking
  
  
• Normal aging due to the inevitable loss of taste buds. or MRI) can be done in selected cases
  

Can taste disorders be treated?? Some taste disorders, particularly those that are caused by a self-limited upper respiratory tract infection, go away on their own. In many cases addressing the underlying cause for the taste disorder is often curative. For example, smokers who quit smoking often find that their sense of taste returns. Or, with physician guidance, stopping or substituting a medication that is responsible for the loss of taste may also restore the sense of taste. In some cases, however, such as when the taste disorder is related to degenerative disease, such as Alzheimer's, or to aging, there is little that can be done to improve the sense of taste. In these cases, measures to improve the appeal of food through the use of herbs, spices, or a variety of colored foods may make eating more pleasurable.

Why do I stay (hot/cold) all the time?

Many people feel uncomfortable at either end of the temperature range. In most cases, this is due to a normal variation in comfort levels at various temperatures and is no cause for concern. An extreme intolerance to heat or cold, however, may signal the presence of a condition that deserves medical attention.

Heat Intolerance. People commonly complain about the heat, but someone with heat intolerance finds it almost impossible to stay comfortable when the temperature rises. Heat intolerance occurs when the body's mechanisms for reducing heat---sweating and increasing blood flow to the skin---are impaired. Some of the potential causes for heat intolerance are:

• Medication side effect: Blood pressure medications, decongestants, and allergy medications are some of the most common drugs with the side effect of heat intolerance. A class of high blood pressure drugs known as beta blockers decrease blood flow to the skin, preventing heat from escaping from the body. Antihistamines, such as loratadine (Claritin) can lead to heat intolerance by inhibiting sweating. Decongestants, such as Sudafed, and stimulants used to treat Attention-Deficit Hyperactivity Disorder (ADHD) can cause heat intolerance because they increase muscle movement which raises body temperature.
                        
  
• Caffeine consumption: Caffeine, found in coffee, tea, and colas is a stimulant that can increase body metabolism which in turn causes a rise in body temperature.
  
  
• Excessive thyroid hormone production: Hyperthyroidism is caused by overactivity of the thyroid gland with the production of too much of the hormone thyroxin. This causes the body's metabolism to increase along with rising body temperature.
  
  
• Menopause: Hot flashes are sudden sensations of heat, most intense over the face, neck and chest, caused by a transient dilation of the blood vessels of the skin. Hot flashes are thought to occur in association with a reduction in estrogen that occurs around the time of menopause which upsets the body's thermostat that is located in the hypothalamus of the brain.

In most cases, addressing the underlying cause for heat intolerance will alleviate the problem. Changing medications to one less likely to cause heat intolerance or reducing caffeine consumption will help restore heat dissipating mechanisms. Hyperthyroidism can be addressed by treatment with radioactive iodine to destroy a portion of the thyroid gland, medications to reduce thyroxin production, or surgery. In the case of menopause, estrogen replacement therapy or waiting until estrogen levels have stabilized helps with heat intolerance symptoms.

Cold intolerance: People with cold intolerance commonly complain of being cold when everyone else is comfortable. It can be defined as an abnormal sensitivity to a cold environment or cold temperatures. In many cases, cold intolerance is simply due to being thin and having little fat to insulate the body. In other instances, cold intolerance can be a sign of a metabolic problem or chronic illness. Some of the most common causes for cold intolerance are:

• Hypothyroidism: The opposite of hyperthyroidism described in the previous section, someone with hypothyroidism does not produce enough thyroid hormone to maintain a normal metabolism level. A lowered metabolism results in less heat production by the body.
  
  
•  Disease affecting the hypothalamus: The hypothalamus is a portion of the brain which, among other functions, maintains body temperature. It can be seen as a type of thermostat for the human body. A number of conditions, including malnutrition, anorexia, head injury, and brain tumors can alter normal hypothalamic function, leading to cold intolerance.
  
  
• Anemia: A reduction in the normal amount of blood cells, such as can occur with iron deficiency, can lead to cold intolerance. In addition to making someone intolerant of the cold, people with anemia may also complain of having low energy, dizziness, a pounding heart during exertion, and pale skin.
  
  
• Chronic severe illness: Addison's disease, also known as adrenal insufficiency, results from damage to the adrenal glands with lowered production of the adrenal hormones---cortisol and aldosterone. In addition to cold intolerance, features of Addison's disease include low blood pressure, fatigue, weight loss, and pigmentation of the skin in certain areas of the body. Cold intolerance can also be a symptom with certain types of cancer.

Other illnesses that have been linked to cold intolerance include fibromyalgia, depression, and sleep deprivation. Since cold intolerance is not a disease but a symptom of an underlying medical condition, treatment hinges on managing that condition. In the case of an anemia cause by insufficient iron consumption, taking supplemental iron will restore blood production with improvement of cold intolerance. Hypothyroidism is usually treated with life-long administration of thyroid hormone replacements. By taking hormone replacements, most people with Addison's disease are able to lead normal lives.

Hepatitis C and Baby Boomers

Americans born between 1945 and 1965 are popularly referred to as "baby boomers". This population of people, now in their 50's and 60's, were part of an explosion of babies born following World War II. Recently, the US Preventive Services Task Force (USPSTF) issued a recommendation that in addition to screening individuals who are at high risk for hepatitis C, all adults born between 1945 and 1965 should receive a one-time screen for the hepatitis C virus (HCV). In May of 2012, a similar recommendation had been issued by the Centers for Disease Control. What exactly is Hepatitis C and why the concern regarding baby boomers?

What is Hepatitis C? Hepatitis C is an infection caused by the hepatitis C virus (HCV) that attacks the liver and can lead to the development of cirrhosis and liver failure. The USPSTF panel has noted that "HCV is the most common chronic bloodborne pathogen in the United States and a leading cause of complications from chronic liver disease."

How does someone contract Hepatitis C? Hepatitis C is transmitted via blood that is contaminated with the hepatitis C virus. The most important risk factor for HCV infection is past or current injection drug use. Other people at risk include health care workers who have been exposed to blood or accidental needle sticks, sexual partners of anyone with a HCV infection, and someone who received a transfusion or blood products prior to the time that reliable testing for HCV was performed.

Wouldn't someone with HCV have symptoms? During its earliest stages, most people with HCV infection have no symptoms. When symptoms are present, they are usually mild, consisting of yellowing of the whites of the eyes (jaundice), fatigue, nausea, and muscle aches. Until the point that liver cells are damaged and replaced by scar tissue (cirrhosis) even people with long-term HCV have very few symptoms. Severe liver damage typically occurs after carrying the virus for 20 to 30 years. With the development of cirrhosis, a number of symptoms can occur including bleeding easily, jaundice, fluid accumulation in the abdomen, loss of appetite, swelling in the legs, and weight loss.

Why are baby boomers at particular risk? Current statistics indicate that about three fourths of Americans living with HCV infection were born between 1945 and 1965. In their recent report, the USPSTF noted that "persons born between 1945 and 1965 are more likely to be diagnosed with HCV infection, possibly because they received blood transfusions before the introduction of screening in 1992 or have a history of other risk factors for exposure decades earlier."

What are some of the long term complications of HCV infection? HCV-related liver failure is the most common reason for liver transplants among adults in the U.S. Additionally, chronic HCV infection imposes a higher risk for the development of liver cancer.

Can Hepatitis C be treated? Not everyone with a HCV infection requires treatment. When liver functions are normal and the disease appears to be benign, monitoring for liver problems may be all that is necessary. When liver function testing indicates active disease and liver biopsy confirms the presence of chronic hepatitis, standard treatment involves a combination of an anti-viral medication (ribavirin) and pegylated interferon (alfa-2a or alfa-2b). Interferons are proteins released by the body, usually in response to the entry of a virus that are capable of inhibiting virus replication.

How do you screen for Hepatitis C? Initial screening is done via a simple blood test to look for the presence of antibodies against HCV (anti–HCV antibody). When this test is positive, the diagnosis is confirmed by a second blood test that uses a technique called polymerase chain reaction.

What are the benefits of detecting HCV if someone does not have symptoms? Since HCV can remain asymptomatic for decades, it has been estimated that as many as 2 million baby boomers are unaware that they have a chronic HCV infection. The USPSTF has acknowledged that "there is no direct evidence of the benefit of screening for HCV infection in asymptomatic adults in reducing morbidity or mortality." Nevertheless, they believe that screening is justified since more effective treatment regimens are currently available that can improve the long-term outlook for those who have a chronic infection.