Question

    Anosmia (Loss of Smell)

    Anosmia is a condition, characterized by loss of smell, which can be either complete or partial in nature. The condition is seldom serious; however, loss of sensation of smell can cause disinterest while eating food, which can eventually lead to development of weight loss and malnutrition.

    Presentation

    Loss of sensation of smell is the main clinical presentation of anosmia. In addition, individuals may also experience symptoms associated with underlying conditions causing anosmia. Individuals with anosmia also experience loss of appetite. This is so because, 80% of the flavors of food comes through sensation of smell [6]. Affected individuals also suffer from depression and isolation because they are devoid of some of the basic pleasures of life such as smelling a flower, scent of a loved one and or fragrance of perfume [7].

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  • Workup

    A preliminary medical history about illnesses will be gathered. Following this, a complete internal examination of the nose will be done. Blood tests would be carried out for evaluating the presence of underlying disease conditions. Imaging studies such as CT scan detect development of tumors in the olfactory system and MRI would also be required to study any anomalies of the brain. In addition, nasal endoscopy and anterior rhinoscopy will also be carried out to detect conditions of nasal polyps as well as inflammation of neuronal membrane. Neurological system examination also provides useful insight about the cranial nerves, sensorimotor functions and cerebellar functions [8].

    Treatment

    Treatment of anosmia depends on the underlying cause of the condition. If individuals suffer from congenital anosmia, then the condition cannot be cured. This is so because, such a kind of condition is linked to genetic predisposition and treatment methods to correct the genetic defects have not yet been designed.

    The other forms of anosmia can be treated to a significant extent if the underlying disease condition can be effectively managed. The following treatment methods would be of help:

    • Nasal decongestant would be of help if nasal congestion is causing temporary loss of smell.
    • Antistamines are prescribed when allergic reactions are the cause of anosmia.
    • Vaporizer or a humidifier may be recommended to loosen the mucus.
    • Surgical procedures would be required to remove the nasal polyps or to strengthen the nasal septum, if it is interfering with the sense of smell [9].
    • Sinus surgery would be employed in cases, when sinusitis gets severe and dramatically affects the sense of smell [10].

    Prognosis

    Certain forms of anosmia that are induced by use of nasal decongestants or common cold infections have a good prognosis rate. However, there are cases, when complete recovery of smell sensation cannot be achieved. This so because, in cases when there are conditions of sinusitis or degenerative diseases of the brain develop, they can significantly cause nerve damage; and then recovery of sensation of smell would be a difficult affair.

    Etiology

    The following factors give rise to the condition of anosmia:

    • Several medications such as estrogen, reserpine, nasal decongestants when used for longer duration, naphazoline, amphetamines and phenothiazines significantly influence the ability to detect odors.
    • Obstruction in the nasal passage due to development of polyps, nasal tumors and septal deformities in the nasal cavity [2]
    • Endocrine disorders, allergic reactions and respiratory infections
    • Injury or trauma to the head
    • Treatment methods such as radiation therapy
    • Nutritional deficiencies 
    • Conditions that irritate the inner lining of the nose include allergic sinusitis, hay fever, common cold, nonallergic rhinitis and influenza [3]

    Epidemiology

    Anosmia can be of various types depending on the nature of the condition. For example, many individuals develop loss of sensation of smell to one particular odor; such a condition is termed as specific anosmia. In yet another form, the sense of smell would be absent from birth, this is called congenital anosmia [4].

    In UK, it has been estimated that about 6,000 individuals are born with congenital anosmia. Statistics have also revealed that, anosmia affects more than 6 million individuals of the US.

    Sex distribution
    Age distribution

    Pathophysiology

    Temporary loss of smell sensation can be attributed to common cold or infections affecting the nasal cavity. Damage to the olfactory nerves contained in the nose or olfactory system can cause permanent loss of sensation of smell. Death of olfactory receptor neurons present in the nose due to brain injury or trauma can also result in development of anosmia. In individuals with congenital anosmia, there is a certain kind of genetic defect that does not activate the sense of smell at birth. It has been seen that such a type of condition is heredity in nature and runs in families.

    In some cases the condition of anosmia can indicate the onset of certain degenerative diseases such as Alzheimer disease and or Parkinson's disease. Development of nasal polyps or use of nasal sprays for prolonged duration can also cause anosmia [5].

    Prevention

    The condition of anosmia cannot be prevented. However, several steps can be taken to ensure safety of the affected individual.

    • Individuals are advised to install smoke alarms in all rooms.
    • Appliances that work on natural gas should be avoided.
    • All foods should be marked with expiry date with special caution for leftover foods.
    • All the labels on kitchen cleaners as well as pesticides should be carefully read before use.

    Summary

    Loss of sensation of smell is often a temporary condition that can occur during conditions of common cough and cold. Anosmia primarily occurs due to inflammation of the nasal passage which consists of the paranasal sinus lining and the superior as well as the middle turbinates. Sometimes, anosmia can indicate onset of underlying conditions such as meningitis, ciliopathy and neurosyphillis. Injury or trauma concerning the head can also lead to loss of sensation of smell [1].

    Patient Information

    Definition: Anosmia refers to loss of sensation of smell due to various factors. The condition can either be present at birth or can be acquired due to underlying disease conditions. Loss of smell can either be partial or complete in nature.

    Cause: Allergies, infections, development of nasal polyps, degenerative disease of the brain, injury or trauma to the head, brain tumor, underactive thyroid, kidney or liver diseases, and certain medications can all cause anosmia.

    Symptoms: Anosmia presents with loss of sensation of smell. Affected individuals also experience loss of appetite which can occur due to inability to sense the flavors of food.

    Diagnosis: Diagnosis begins with a preliminary internal examination of the nose. Simultaneously blood tests are done to determine disease condition. In addition, imaging studies such as CT scan and MRI are also done. Neurological examination is also required to test for abnormalities if any.

    Treatment: Treatment involves managing the underlying disease condition to restore the smell sensation. If infections or common cold is causing a stuffy nose then nasal decongestant should do the trick. If nasal polyps are the cause then surgery to remove them would be required. In many cases, surgical procedures would also be opted for straightening the nasal septum.

    Self-assessment

    References

    1. Sumner D. Post-traumatic anosmia. Brain 1964; 87:107.
    2. Norlander T, Bronnegard M, Stierna P. The relationship of nasal polyps, infection, and inflammation. Am J Rhinol. Sep-oct 1999;13(5):349-55.
    3. Apter AJ, Mott AE, Frank ME, Clive JM. Allergic rhinitis and olfactory loss.Ann allergy asthma immunol 1995; 75:311.
    4. Smith DV, Duncan HJ. Primary olfactory disorders: anosmia, hyposmia and dysosmia. In: science of olfaction, serbymj, chobor kl (eds), springer-verlag, new york 1992. P.439.
    5. Semmes J, Weinstein S, Ghent L, Tanber HL. Normative study. In: somatosensory changes after penetrating brain injuries in man, semmes j (ed), harvard university press, cambridge 1960. P.4.
    6. Rusiniak KW, Hankins WG, Garcia J, Brett LP. Flavor-illness aversions: potentiation of odor by taste in rats. Behav neural biol 1979; 25:1.
    7. Radenne F, Lamblin C, Vandezande LM, et al. Quality of life in nasal polyposis. J Allergy Clinimmunol. Jul 1999;104(1):79-84.
    8. Andrews AE, Bryson JM, Rowe-Jones JM. Site of origin of nasal polyps: relevance to pathogenesis and management. Rhinology. Sep 2005;43(3):180-4
    9. Blaiss MS. Expanding the evidence base for the medical treatment of nasal polyposis. J Allergy Clinimmunol. Dec 2005;116(6):1272-4.
    10. Lund VJ. The effect of sinonasal surgery on asthma. Allergy. 1999;54 suppl 57:141-5.



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