anosmia

Anosmia (pronounced /ænˈɒzmiə/) is a lack of functioning olfaction, or in other words, an inability to perceive odors. Anosmia may be temporary but traumatic anosmia can be permanent. Anosmia is not due to any inflammation of the nasal mucosa; blockage of nasal passages or a destruction of one temporal lobe. It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time.^[1] Many patients may experience unilateral anosmia, often as a result of minor head trauma. This type of anosmia is normally only detected if both of the nostrils are tested separately. Using this method of testing each nostril separately will often show a reduced or even completely absent sense of smell in either one nostril or both, something which is often not revealed if both nostrils are simultaneously tested. ^[2]

A related term, hyposmia, refers to a decreased ability to smell, while hyperosmia refers to an increased ability to smell. Some people may be anosmic for one particular odor. This is known as "specific anosmia". The absence of the sense of smell from birth is called Congenital Anosmia.

Diagnosis

Anosmia can be diagnosed by doctors by using acetylcysteine tests. Doctors will begin with a detailed elicitation of history. Then the doctor will ask for any related injuries in relation to Anosmia which could include upper respiratory infections or head injury. Psychophysical Assessment of order and taste identification can be used to identity anosmia. A nervous system examination is performed to see if the cranial nerves are damaged.^[3] The diagnosis as well as the degree of impairment can now be tested much more efficiently and effectively than ever before thanks to "smell testing kits" that have been made available as well as screening tests which use materials that most clinics would readily have.^[4] Occasionally, after accidents, there is a change in a patient's sense of smell. Particular smells that were present before are no longer present. On occasion, after head traumas, there are patients who have unilateral anosmia. The sense of smell should be tested individually in each nostril. ^[5]

Presentation

Anosmia can have a number of harmful effects. Patients with sudden onset anosmia may find food less appetizing, though congenital anosmics rarely complain about this. Loss of smell can also be dangerous because it hinders the detection of gas leaks, fire, and spoiled food. The common view of anosmia as trivial can make it more difficult for a patient to receive the same types of medical aid as someone who has lost other senses, such as hearing or sight.

Losing an established and sentimental smell memory (e.g. the smell of grass, of the grandparents' attic, of a particular book, of loved ones, or of oneself) has been known to cause feelings of depression.^[6]

Loss of olfaction may lead to the loss of libido, though this usually does not apply to congenital anosmics.^[6]

Often people who have congenital anosmia report that they pretended to be able to smell as children because they thought that smelling was something that older/mature people could do, or did not understand the concept of smelling but did not want to appear different from others. When children get older, they often realize and report to their parents that they do not actually possess a sense of smell, often to the surprise of their parents. ^[6]

A study done on patients suffering from anosmia found that when testing both nostrils, there was no anosmia revealed, however when testing each nostril individually, tests showed that that the sense of smell was usually affected in only one of the nostrils as opposed to both. This demonstrated that unilateral anosmia is not uncommon in anosmia patients. ^[7]

Causes

A temporary loss of smell can be caused by a blocked nose or infection. In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the olfactory nerve or damage to brain areas that process smell (see olfactory system). The lack of the sense of smell at birth, usually due to genetic factors, is referred to as congenital anosmia. Anosmia may very occasionally be an early sign of a degenerative brain disease such as Parkinson's disease and Alzheimer's disease. Another specific cause of permanent loss could be from damage to olfactory receptor neurons because of use of certain types of nasal spray; i.e., those that cause vasoconstriction of the nasal microcirculation. To avoid such damage and the subsequent risk of loss of smell, vasoconstricting nasal sprays should be used only when absolutely necessary and then for only a short amount of time. Non-vasoconstricting sprays, such as those used to treat allergy related congestion, are safe to use for prescribed periods of time.^[8] Anosmia can also be caused by nasal polyps. These polyps are found in people with allergies, histories of sinusitis & family history. Individuals with cystic fibrosis often develop nasal polyps.

Amiodarone is a drug used in the treatment of arrhythmias of the heart. A clinical study performed demonstrated that the use of this drug induced anosmia in some patients. Although rare, there was a case in which a 66-year-old male was treated with Amiodarone for ventricular tachycardia. After the use of the drug he began experiencing olfactory disturbance, however after decreasing the dosage of Amiodarone, the severity of the anosmia decreased accordingly hence correlating the use of Amiodarone to the development of anosmia. ^[9]

Causes of anosmia include:

• Upper respiratory tract infection (e.g., sinusitis or the common cold)^[10]
• Nasal polyps
• Idiopathic hypogonadotropic hypogonadism
• Hypothyroidism
• Head trauma, damage to the ethmoid bone^[11]
• Dementia with Lewy bodies
• Tumors of the frontal lobe
• Parkinson's disease^[12]
• Alzheimer's disease^[13]
• Toxins (especially acrylates, methacrylates^[14] and cadmium^[15][16])
• Old age^[17]
• Kallmann syndrome
• Post-perfusion syndrome
• Laryngectomy with permanent tracheostomy
• Esthesioneuroblastoma is an exceedingly rare cancerous tumor that originates in or near the olfactory nerve. Symptoms are anosmia (loss of sense of smell) often accompanied by chronic sinusitis.^[18]
• Intranasal drug use
• Samter's triad
• Foster Kennedy syndrome
• Cadmium poisoning
• Smoking
• Neurotropic virus^[19]
• Schizophrenia^[20]
• Pernicious anemia
• Zinc deficiency
• Idiopathic intracranial hypertension
• Suprasellar meningioma
• Refsum's disease
• Adrenergic agonists or withdrawal from alpha blockers (vasoconstriction)
• Sarcoidosis^[21]
• Zinc-based intranasal cold products
• Chronic atrophic rhinitis
• Paget's disease of bone^[22]
• Cerebral Aneurysm^[23]

This list is incomplete; you can help by expanding it.

Treatment

Though anosmia caused by brain damage cannot be treated, anosmia caused by inflammatory changes in the mucosa may be treated with glucocorticoids. Reduction of inflammation through the use of oral glucocorticoids such as, prednisone, followed by long term topical glucocorticoid nasal spray would easily and safely treat the anosmia. However, the treatment is not permanent and may have to be repeated after a short while. ^[24]

Zicam controversy

On June 16, 2009, the U.S. Food and Drug Administration sent a warning letter to Matrixx Initiatives, manufacturer of an over-the-counter nasal spray for the common cold, Zicam. The FDA cited complaints that the product caused anosmia. The manufacturer strongly denies these allegations, but has recalled the product and has stopped selling it.^[25]

Associated conditions

• Dysosmia
• Kallmann syndrome
• Zinc deficiency
• Cadmium Poisoning
• Holoprosencephaly
• Primary amoebic meningoencephalitis caused by Naegleria fowleri
• Refsum disease
• CHARGE syndrome
• Ageusia

This list is incomplete; you can help by expanding it.

Notable anosmic individuals

• Don Powell (drummer for the legendary band Slade)
• Arjen Lucassen
• Selma Bouvier (Fictional Character)
• Dennis Brain
• Ben Cohen
• Dewey Cox (Fictional Character)
• Mary Baker Eddy
• Michael Hutchence
• Justin Hayward (for a period in the 1990s)^[26]
• Simon Katich
• Scott Kurtz (author of webcomic PvP)^[27]
• Cynthia Nixon
• Bill Pullman
• Harry Redknapp^[28]
• Simon Tatham
• Benjamin Urrutia
• Davis Quinton (Fictional Character)
• Stevie Wonder
• William Wordsworth
• Holly Haycock

See also

• Hyperosmia
• Hyposmia
• Parosmia
• Richard Doty, Ph.D (researcher in the field of olfactory functioning and dysfunction)

References

Further reading

This article lacks ISBNs for the books listed in it. Please make it easier to conduct research by listing ISBNs. If the {{Cite book}} or {{citation}} templates are in use, you may add ISBNs automatically, or discuss this issue on the talk page. (December 2011)

• Blodgett, Bonnie (2010). Remembering Smell: A Memoir of Losing - and Discovering - the Primal Sense. Houghton Mifflin Harcourt. 
• Tafalla, Marta (2010) (in Spanish). Nunca sabrás a qué huele Bagdad (You will never know the smell of Bagdad). Autonomous University of Barcelona.  - Novel dealing with congenital anosmia.

External links

• An online survey for people with acquired anosmia, i. e. who lost their sense of smell throughout their lives
• What does the lack of a sense of smell do to flavour perception? Guardian.co.uk
• Cardiff University Anosmia resource site