anosmia


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Anosmia

 

Definition

The term anosmia means lack of the sense of smell. It may also refer to a decreased sense of smell. Ageusia, a companion word, refers to a lack of taste sensation. Patients who actually have anosmia may complain wrongly of ageusia, although they retain the ability to distinguish salt, sweet, sour, and bitter—humans' only taste sensations.

Description

Of the five senses, smell ranks fourth in importance for humans, although it is much more pronounced in other animals. Bloodhounds, for example, can smell an odor a thousand times weaker than humans. Taste, considered the fifth sense, is mostly the smell of food in the mouth. The sense of smell originates from the first cranial nerves (the olfactory nerves), which sit at the base of the brain's frontal lobes, right behind the eyes and above the nose. Inhaled airborne chemicals stimulate these nerves.
There are other aberrations of smell beside a decrease. Smells can be distorted, intensified, or hallucinated. These changes usually indicate a malfunction of the brain.

Causes and symptoms

The most common cause of anosmia is nasal occlusion caused by rhinitis (inflammation of the nasal membranes). If no air gets to the olfactory nerves, smell will not happen. In turn, rhinitis and nasal polyps (growths on nasal membranes) are caused by irritants such as allergens, infections, cigarette smoke, and other air pollutants. Tumors such as nasal polyps can also block the nasal passages and the olfactory nerves and cause anosmia. Head injury or, rarely, certain viral infections can damage or destroy the olfactory nerves.

Diagnosis

It is difficult to measure a loss of smell, and no one complains of loss of smell in just one nostril. So a physician usually begins by testing each nostril separately with a common, non-irritating odor such as perfume, lemon, vanilla, or coffee. Polyps and rhinitis are obvious causal agents a physician looks for. Imaging studies of the head may be necessary in order to detect brain injury, sinus infection, or tumor.

Treatment

Cessation of smoking is the first step. Many smokers who quit discover new tastes so enthusiastically that they immediately gain weight. Attention to reducing exposure to other nasal irritants and treatment of respiratory allergies or chronic upper respiratory infections will be beneficial. Corticosteroids are particularly helpful.

Alternative treatment

Finding and treating the cause of the loss of smell is the first approach in naturopathic medicine. If rhinitis is the cause, treating acute rhinitis with herbal mast cell stabilizers and herbal decongestants can offer some relief as the body heals. If chronic rhinitis is present, this is often related to an environmental irritant or to food allergies. Removal of the causative factors is the first step to healing. Nasal steams with essential oils offer relief of the blockage and tonification of the membranes. Blockages can sometimes be resolved through naso-specific therapy-a way of realigning the nasal cavities. Polyp blockage can be addressed through botanical medicine treatment as well as hydrotherapy. Olfactory nerve damage may not be regenerable. Some olfactory aberrations, like intensified sense of smell, can be resolved using homeopathic medicine.

Prognosis

If nasal inflammation is the cause of anosmia, the chances of recovery are excellent. However, if nerve damage is the cause of the problem, the recovery of smell is much more difficult.

Resources

Books

Fauci, Anthony S., et al., editors. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 1997.

Key terms

Allergen — Any substance that irritates only those who are sensitive (allergic) to it.
Corticosteroids — Cortisone, prednisone, and related drugs that reduce inflammation.
Nasal polyps — Drop-shaped overgrowths of the nasal membranes.
Rhinitis — Inflammation and swelling of the nasal membranes.

anosmia

 [an-oz´me-ah]
absence of the sense of smell. adj., adj anosmat´ic, anos´mic.

an·os·mi·a

(an-oz'mē-ă), [MIM*301700]
Loss or absence of the sense of smell. It may be: general to all odorants (total), partial to some odorants, or specific to one or more odorants; due to transport disorders (in nasal obstruction) or sensorineural disorders (affecting the olfactory neuroepithelium or the central olfactory neural pathways); or hereditary or acquired. Recent studies indicate it is often the first sensory loss directly related to Alzheimer disease.
[G. an- priv. + osmē, sense of smell]

anosmia

/an·os·mia/ (an-oz´me-ah) lack of sense of smell.anos´micanosmat´ic

anosmia

(ăn-ŏz′mē-ə)
n.
Loss of the sense of smell.

an·os′mic adj.

anosmia

[anoz′mē·ə]
Etymology: Gk, a + osme, without smell
a loss or an impairment of the sense of smell. It can occur as a temporary condition when a person has a head cold or respiratory infection or when intranasal swelling or other obstruction prevents odors from reaching the olfactory region. It becomes permanent when the olfactory neuroepithelium or any part of the olfactory nerve is destroyed as a result of intracranial trauma, neoplasms, or disease, such as atrophic rhinitis or the chronic rhinitis associated with the granulomatous diseases. In some instances, the condition may be caused by psychological factors, such as a phobia or fear associated with a particular smell. Kinds of anosmia include anosmia gustatoria and preferential anosmia.Also called anosphresia,olfactory anesthesia. anosmatic, anosmic, adj.

anosmia

Absence of the sense of smell, a symptom typical of frontal lobe brain tumours.

Anosmia types 
▪ Nasal—Odorants do not reach the olfactory receptors. 
▪ Olfactory —Destruction of receptors or axons.  
▪ Central—Olfactory pathway problems.

anosmia

Anosphrasia, olfactory anaesthesia Absence of the sense of smell, a symptom typical of frontal lobe brain tumors

an·os·mi·a

(an-oz'mē-ă)
Loss of the sense of smell. It may be due to lesion of the olfactory nerve, obstruction of the nasal fossae, or functional, without any apparent causative lesion.
[G. an- priv. + osmē, sense of smell]

anosmia

Loss of the sense of smell. This often results from injury to the delicate fibres of the OLFACTORY NERVE as they pass through the bone above the nose (the cribriform plate).

anosmia,

n the inability to smell; may be short-term, selective (only affecting certain aromas), or total and permanent.

an·os·mi·a

(an-oz'mē-ă) [MIM*301700]
Loss or absence of the sense of smell.
[G. an- priv. + osmē, sense of smell]

anosmia

absence of the sense of smell; characteristic of lesions of the olfactory lobe, peduncle or mucosa. Such deficiencies are difficult to assess in animals.
References in periodicals archive ?
People who are born with congenital anosmia, may lack such nerves too.
Anosmia can be temporary, caused by a stuffed nose or infection, or it can be more permanent due to the death of the olfactory receptors or damage to other parts of the olfactory system.
Ultimately, FDA determined there was a safety risk (of anosmia) associated with Zicam, and that therefore the product must have new drug approval and be labeled with adequate warnings regarding the risk of anosmia.
Endoscopic sinus surgery (ESS) gives good symptomatic relief, especially when the main symptoms are nasal obstruction, anosmia and headaches.
The warning letter cited consumer reports that the use of these products could cause a temporary or permanent loss of smell, known as anosmia.
During the annual shareholders' meeting, company executives will discuss the most recent attacks, which began with a poster presentation by Bruce Jafek, MD, Rocky Mountain Taste and Smell Center at the University of Colorado Medical Center, attempting to link intranasal zinc gluconate gel--the active ingredient in Zicam Cold Remedy nasal gels--to anosmia (loss of smell).
5,6) Other manifestations, which are usually related to the degree of tumor extension, can include headache, dizziness, focal neurologic deficits secondary to direct tumor extension, eye and/ or facial pain, expectoration of tissue, epiphora, vision loss, exophthalmos, and anosmia.
The FDA referred to numerous complaints it has received of anosmia associated with the use of these products.
In fact, in neither study were there any reports of anosmia related to the use of this compound.
Classically, a patient with AFRS will be an adolescent or young adult with manifestations of chronic sinusitis, including nasal obstruction, congestion, purulent or clear rhinorrhea, anosmia, and headache.
In addition to concerns regarding the efficacy of intranasal zinc therapy, increasing evidence indicates that this medication may be linked to severe, potentially permanent hyposmia (reduced sense of smell) and anosmia (loss of smell)," the authors said.
Only intra-nasal products have shown any association with anosmia.