Anosmia | |
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Other names | Loss of smell, smell blindness, [1] odor blindness |
Inflamed nasal mucosa causing anosmia | |
Pronunciation | |
Specialty | Otorhinolaryngology |
Types | Partial, total [2] |
Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells. [1] [2] Anosmia may be temporary or permanent. [3] It differs from hyposmia, which is a decreased sensitivity to some or all smells. [2]
Anosmia can be categorized into acquired anosmia and congenital anosmia. Acquired anosmia develops later in life due to various causes, such as upper respiratory infections, head trauma, or neurodegenerative diseases. [4] In contrast, congenital anosmia is present from birth and is typically caused by genetic factors or developmental abnormalities of the olfactory system. [5] While acquired anosmia may have potential treatments depending on the underlying cause, such as medications or surgery, congenital anosmia currently has no known cure, and management focuses on safety precautions and coping strategies. [6]
Anosmia can be due to a number of factors, including inflammation of the nasal mucosa, blockage of nasal passages, or destruction of temporal lobular tissue. [7] Anosmia stemming from sinus inflammation is due to chronic mucosal changes in the lining of the paranasal sinus and in the middle and superior turbinates. [8] [9]
When anosmia is caused by inflammatory changes in the nasal passageways, it is treated simply by reducing inflammation. [10] [11] It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time, [12] and, in some cases, by ciliopathy, [13] including ciliopathy due to primary ciliary dyskinesia. [14]
The term derives from the Neo-Latin anosmia, based on Ancient Greek ἀν- (an-) + ὀσμή (osmḗ 'smell'; another related term, hyperosmia, refers to an increased ability to smell). Some people may be anosmic for one particular odor, a condition known as "specific anosmia". The absence of the sense of smell from birth is known as congenital anosmia. [15]
In the United States, 3% of people aged over 40 are affected by anosmia. [3]
Anosmia is a common symptom of COVID-19 and can persist as long COVID. [16]
Anosmia is the inability to smell. [1] It may be partial or total, and can be specific to certain smells. [2] Reduced sensitivity to some or all smells is hyposmia. [2]
Anosmia can have a number of harmful effects. [17] People with sudden onset anosmia may find food less appetizing, though congenital anosmics rarely complain about this, and none report a loss in weight. Loss of smell can also be dangerous because it hinders the detection of gas leaks, fire, and spoiled food. Misconceptions 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.[ citation needed ]
Many experience one sided loss of smell, 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. [18]
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. [19] [ better source needed ]
Loss of the ability to smell may lead to the loss of libido, but this usually does not apply to those with olfactory dysfunction at birth. [19] [20]
Often people who have loss of smell at birth 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.[ citation needed ]
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. Family members of the patient with congenital anosmia are often found with similar histories; this suggests that the anosmia may follow an autosomal dominant pattern. [21] Anosmia may very occasionally be an early sign of a degenerative brain disease such as Parkinson's disease and Alzheimer's disease.[ citation needed ]
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. [22] Anosmia can also be caused by nasal polyps. These polyps are found in people with allergies, histories of sinusitis, and family history. Individuals with cystic fibrosis often develop nasal polyps.[ citation needed ]
Amiodarone is a drug used in the treatment of arrhythmias of the heart. A clinical study 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, suggesting a relationship between use of amiodarone to the development of anosmia. [23]
Chemosensory disturbances, including loss of smell or taste, are the predominant neurological symptom of COVID-19. [24] [25] As many as 80% of COVID-19 patients exhibit some change in chemesthesis, including smell. Loss of smell has also been found to be more predictive of COVID-19 than all other symptoms, including fever, cough, or fatigue, based on a survey of 2 million participants in the UK and US. [26] Google searches for "smell", "loss of smell", "anosmia", and other similar terms increased since the early months of the pandemic, and strongly correlated with increases in daily cases and deaths. [27] Research into the mechanisms underlying these symptoms is currently ongoing. [28] [29]
Many countries list anosmia as an official COVID-19 symptom, and some have developed "smell tests" as potential screening tools. [30] [31]
In 2020, the Global Consortium for Chemosensory Research, a collaborative research organization of international smell and taste researchers, formed to investigate loss of smell and related chemosensory symptoms. [32]
Studies have indicated that patients who presented with anosmia during the acute phase of COVID-19 are more likely to develop changes in decision-making, exhibiting more impulsive responses, which are associated with functional and structural brain changes. [33]
Diagnosis begins with a detailed history, including possible related injuries, such as upper respiratory infections or head injury. The examination may involve nasal endoscopy for obstructive factors such as polyps or swelling. [7] A nervous system examination is performed to see if the cranial nerves are affected. [7] On occasion, after head traumas, there are people who have unilateral anosmia. The sense of smell should be tested individually in each nostril. [18]
Many cases of congenital anosmia remain unreported and undiagnosed. Since the disorder is present from birth the individual may have little or no understanding of the sense of smell, hence is unaware of the deficit. [55] It may also lead to reduction of appetite. [56]
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. A prednisone regimen is adjusted based on the degree of the thickness of mucosa, the discharge of oedema and the presence or absence of nasal polyps. [10] However, the treatment is not permanent and may have to be repeated after a short while. [10] Together with medication, pressure of the upper area of the nose must be mitigated through aeration and drainage. [57]
Anosmia caused by a nasal polyp may be treated by steroidal treatment or removal of the polyp. [58]
Although very early in development, gene therapy has restored a sense of smell in mice with congenital anosmia when caused by ciliopathy. In this case, a genetic condition had affected cilia in their bodies which normally enabled them to detect air-borne chemicals, and an adenovirus was used to implant a working version of the IFT88 gene into defective cells in the nose, which restored the cilia and allowed a sense of smell. [59] [60]
In the United States, 3% of people aged over 40 are affected by anosmia. [3]
In 2012, smell was assessed in persons aged 40 years and older with rates of anosmia/severe hyposmia of 0.3% at age 40–49 rising to 14.1% at age 80+. Rates of hyposmia were much higher: 3.7% at age 40–49 and 25.9% at 80+. [61]
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Dysgeusia, also known as parageusia, is a distortion of the sense of taste. Dysgeusia is also often associated with ageusia, which is the complete lack of taste, and hypogeusia, which is a decrease in taste sensitivity. An alteration in taste or smell may be a secondary process in various disease states, or it may be the primary symptom. The distortion in the sense of taste is the only symptom, and diagnosis is usually complicated since the sense of taste is tied together with other sensory systems. Common causes of dysgeusia include chemotherapy, asthma treatment with albuterol, and zinc deficiency. Liver disease, hypothyroidism, and rarely, certain types of seizures can also lead to dysgeusia. Different drugs can also be responsible for altering taste and resulting in dysgeusia. Due to the variety of causes of dysgeusia, there are many possible treatments that are effective in alleviating or terminating the symptoms. These include artificial saliva, pilocarpine, zinc supplementation, alterations in drug therapy, and alpha lipoic acid.
The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal cavity is the uppermost part of the respiratory system and provides the nasal passage for inhaled air from the nostrils to the nasopharynx and rest of the respiratory tract.
The olfactory system, or sense of smell, is the sensory system used for olfaction. Olfaction is one of the special senses directly associated with specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli.
Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty. Kallmann syndrome is a form of a group of conditions termed hypogonadotropic hypogonadism. To distinguish it from other forms of hypogonadotropic hypogonadism, Kallmann syndrome has the additional symptom of a total lack of sense of smell (anosmia) or a reduced sense of smell. If left untreated, people will have poorly defined secondary sexual characteristics, show signs of hypogonadism, almost invariably are infertile and are at increased risk of developing osteoporosis. A range of other physical symptoms affecting the face, hands and skeletal system can also occur.
Aspirin-exacerbated respiratory disease (AERD), also called NSAID-exacerbated respiratory disease (N-ERD) or historically aspirin-induced asthma and Samter's Triad, is a long-term disease defined by three simultaneous symptoms: asthma, chronic rhinosinusitis with nasal polyps, and intolerance of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). Compared to aspirin tolerant patients, AERD patients' asthma and nasal polyps are generally more severe. Reduction or loss of the ability to smell is extremely common, occurring in more than 90% of people with the disease. AERD most commonly begins in early- to mid-adulthood and has no known cure. While NSAID intolerance is a defining feature of AERD, avoidance of NSAIDs does not affect the onset, development or perennial nature of the disease.
Ageusia is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami. It is sometimes confused with anosmia – a loss of the sense of smell. True ageusia is relatively rare compared to hypogeusia – a partial loss of taste – and dysgeusia – a distortion or alteration of taste.
Parosmia is a dysfunctional smell detection characterized by the inability of the brain to correctly identify an odor's "natural" smell. Instead, the natural odor is usually transformed into an unpleasant aroma, typically a "burned", "rotting", "fecal", or "chemical" smell. There can also be rare instances of a pleasant odor called euosmia. The condition was rare and little-researched until it became relatively more widespread since 2020 as a side effect of COVID-19.
Phantosmia, also called an olfactory hallucination or a phantom odor, is smelling an odor that is not actually there. This is intrinsically suspicious as the formal evaluation and detection of relatively low levels of odour particles is itself a very tricky task in air epistemology. It can occur in one nostril or both. Unpleasant phantosmia, cacosmia, is more common and is often described as smelling something that is burned, foul, spoiled, or rotten. Experiencing occasional phantom smells is normal and usually goes away on its own in time. When hallucinations of this type do not seem to go away or when they keep coming back, it can be very upsetting and can disrupt an individual's quality of life.
Hyposmia, or microsmia, is a reduced ability to smell and to detect odors. A related condition is anosmia, in which no odors can be detected. Some of the causes of olfaction problems are allergies, nasal polyps, viral infections and head trauma. In 2012 an estimated 9.8 million people aged 40 and older in the United States had hyposmia and an additional 3.4 million had anosmia/severe hyposmia.
Hypogeusia can be defined as the reduced ability to taste things. Due to a lack of stratification, the prevalence of hypogeusia, as well as hyposmia, may not be accurately known. Additionally, reviews do not always make distinctions between ageusia and hypogeusia, often classifying them as the same in certain circumstances and studies. The severity of the loss of taste from hypogeusia is not clearly outlined in current research due to these reasons.
Dysosmia is a disorder described as any qualitative alteration or distortion of the perception of smell. Qualitative alterations differ from quantitative alterations, which include anosmia and hyposmia. Dysosmia can be classified as either parosmia or phantosmia. Parosmia is a distortion in the perception of an odorant. Odorants smell different from what one remembers. Phantosmia is the perception of an odor when no odorant is present. The cause of dysosmia still remains a theory. It is typically considered a neurological disorder and clinical associations with the disorder have been made. Most cases are described as idiopathic and the main antecedents related to parosmia are URTIs, head trauma, and nasal and paranasal sinus disease. Dysosmia tends to go away on its own but there are options for treatment for patients that want immediate relief.
The sense of smell, or olfaction, is the special sense through which smells are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste.
Many types of sense loss occur due to a dysfunctional sensation process, whether it be ineffective receptors, nerve damage, or cerebral impairment. Unlike agnosia, these impairments are due to damages prior to the perception process.
The University of Pennsylvania Smell Identification Test (UPSIT) is a test that is commercially available for smell identification to test the function of an individual's olfactory system.
Anosmia Awareness Day is a day to spread awareness about anosmia (an-OHZ-me-uh), the loss of the sense of smell. It takes place each year on February 27.
The symptoms of COVID-19 are variable depending on the type of variant contracted, ranging from mild symptoms to a potentially fatal illness. Common symptoms include coughing, fever, loss of smell (anosmia) and taste (ageusia), with less common ones including headaches, nasal congestion and runny nose, muscle pain, sore throat, diarrhea, eye irritation, and toes swelling or turning purple, and in moderate to severe cases, breathing difficulties. People with the COVID-19 infection may have different symptoms, and their symptoms may change over time. Three common clusters of symptoms have been identified: one respiratory symptom cluster with cough, sputum, shortness of breath, and fever; a musculoskeletal symptom cluster with muscle and joint pain, headache, and fatigue; and a cluster of digestive symptoms with abdominal pain, vomiting, and diarrhea. In people without prior ear, nose, or throat disorders, loss of taste combined with loss of smell is associated with COVID-19 and is reported in as many as 88% of symptomatic cases.
Claire Hopkins is a British Ear, Nose & Throat (ENT) surgeon at Guy's Hospital and Professor of Rhinology at King's College London. She is the President of the British Rhinological Society. During the COVID-19 pandemic, Hopkins successfully campaigned to have anosmia recognised as a symptom of COVID-19 in the United Kingdom.
There is increasing evidence suggesting that COVID-19 causes both acute and chronic neurologicalor psychological symptoms. Caregivers of COVID-19 patients also show a higher than average prevalence of mental health concerns. These symptoms result from multiple different factors.
Smell training or olfactory training is the act of regularly sniffing or exposing oneself to robust aromas with the intention of regaining a sense of smell. The stimulating smells used are often selected from major smell categories, such as aromatic, flowery, fruity, and resinous. Using strong scents, the patient is asked to sniff each different smell for a minimum of 20 seconds, no less than two times per day, for three to six months or more. It is used as a rehabilitative therapy to help people who have anosmia or post-viral olfactory dysfunction, a symptom of COVID-19. It was considered a promising experimental treatment in a 2017 meta-analysis.
Congenital anosmia is a rare condition characterized by the complete inability to perceive smell from birth. It affects approximately 1 in 10,000 individuals and is often diagnosed later in life due to its subtle presentation and lack of associated symptoms.
My fiancé [Jason Sudeikis] has no sense of smell — he was born without it....