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

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

an·os′mic 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).

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]
References in periodicals archive ?
Novel fibroblast growth factor receptor 1 mutations in patients with congenital hypogonadotropic hypogonadism with and without anosmia. J Clin Endocrinol Metab 2006;91:4006-4012.
The immediate implications of the work are limited to animal models, which provide the necessary foundation for eventually addressing human anosmias.
When the exposure groups were taken into account (Table 4), the SROI (OR = 4.71; 95% CI: 1.08-20.63) were more frequently complained about by workers from the mixing plant, exhibited more frequently, in particular in terms of the anosmia (7/15, OR = 15.75; 95% CI: 1.65-150.14).
The prevalence of hyposmia or anosmia in PD has been reported to range from 70% to 90% [17].
Para avaliacao dos fatores associados a anosmia (desfecho) foi realizada regressao logistica univariada por meio da odds ratio.
The common risks involved with endoscopic sinus surgery including bleeding, infection, injury to the eye and its adnexa, cerebrospinal fluid (CSF) leak, and anosmia. (8) We encountered anosmia and CSF leak in two cases each.
(27.) Available at: http://george-eby-research.com/anosmia/ anosmia. html.
The studies used the 40-item University of Pennsylvania Smell Identification Test (UPSIT), a scratch-and-sniff test that measures anosmia of mild, moderate, or severe levels, and costs about $25.
The mechanisms of smell are discussed next in great detail, including animal research, G protein-coupled receptors, interpretation in the brain, and what we've learned from human anosmia. The interactions between chemistry and biology in the characterization of scents are covered, followed by the sense of smell over the lifespan and natural sources of fragrance compounds.
Inhaled zinc can cause permanent anosmia, and so this delivery route was not investigated.
Only patients diagnosed with anosmia, the complete loss of olfactory function, were included in this study [18].
Headache or facial pain resolve within 7 days after remission or successful treatment of acute or acute-on-chronic rhinosinusitis * Clinical evidence may include purulence in the nasal cavity, nasal obstruction, hyposmia or anosmia, and fever; chronic sinusitis is not validated as a cause of headache or facial pain unless it relapses into an acute stage.