Smell, loss of (Anosmia)

Anosmia is a lack of functioning olfaction, or in other words, an inability to perceive odors. Anosmia may be either temporary or permanent. 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 called "specific anosmia" and may be genetically based.

Diagnosis

Anosmia can be diagnosed by doctors by using scratch-n-sniff odor tests or by using commonly available odors such as peanut butter, coffee, lemon, grape, garlic, vanilla and cinnamon.

Presentation

Anosmia can have a number of detrimental 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.

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

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.

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 degenerative brain diseases such as Parkinson's disease and Alzheimer's disease. Another specific cause of permanent loss could be from damage to olfactory receptor neurons due to use of certain types of nasal spray, i.e. those that cause vasoconstriction of the nasal microcirculation. To avoid such damage and subsequent risk of loss of smell from vasoconstricting nasal sprays, they should be used for only a short amount of time and only when absolutely necessary. Non-vasoconstricting sprays, such as those used to treat allergy related congestion are safe to use for extended periods of time. 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.

Causes of anosmia include:

• Upper respiratory tract infection (e.g., sinusitis or the common cold)
• Nasal polyps
• Hypothyroidism
• Head trauma, damage to the ethmoid bone
• Dementia with Lewy bodies
• Tumors of the frontal lobe
• Parkinson's Disease
• Alzheimer's Disease
• Toxins (especially acrylates, methacrylates and cadmium)
• Old age
• Kallmann syndrome
• Post-Profusion 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.
• Intranasal drug use
• Samter's triad
• Foster Kennedy syndrome
• Cadmium poisoning
• Smoking
• Neurotropic virus
• Schizophrenia
• Pernicious Anemia
• Zinc deficiency
• Idiopathic intracranial hypertension (IIH)
• Suprasellar Meningioma
• Refsum's disease

This list is incomplete.

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.

Associated conditions

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

This list is incomplete