Smell And Taste Disorders

Introduction:

Smell and taste are two of the important senses of human beings. Loss of these sensations has been associated with various causes. It can be life-threatening in some situations as it may prevent the detection of the smell of smoke during a fire accident, spoiled food, etc.

How Is It Classified?

The basic terminology for smell disorders is "osmia," and taste disorders are called "geusia." Following are the basic terminologies of disorders:

1. Anosmia - Inability to detect smell.

2. Hyposmia - Decreased ability to detect any type of smell.

3. Dysosmia - Any alteration in smell.

• Parosmia - Alteration in the perception of smell, even in the presence of a smell. It is usually unpleasant.

• Phantosmia - Experience of smell even without the presence of smell.

• Agnosia - Difficulty in differentiating between types of smell, although smell can be detected.

4. Ageusia - Inability to taste anything.

5. Hypogeusia - Decrease in the ability to taste.

6. Dysgeusia - Distortion in the ability to taste.

The disorders of smell and taste can be total, partial, or specific.

How Are These Disorders Caused?

1. Olfactory Dysfunction:

A change in smell or olfactory can be due to some pathology affecting any level of the smell pathway. It can be classified into the following:

• Conductive (Transport) Defects: There is a disruption in transmitting an odorant stimulus to the olfactory neuroepithelium.

• Sensorineural Defects: These involve the more central nervous system structures. More commonly, aging, nasal and/or sinus disease, head trauma, upper respiratory tract infections can cause these effects.

Conductive Defects:

1. Inflammatory conditions like rhinitis due to allergy, acute or toxic (Cocaine use), chronic rhinosinusitis, etc., can cause conductive defects.

2. Presence of any mass can lead to blockage of the nasal cavity, leading to obstruction in the flow of odorants to the olfactory epithelium, for example, nasal polyps (most common), inverting papilloma, or any nasal tumor.

3. Developmental abnormalities like encephaloceles and dermoid cysts may also cause obstructions.

4. Patients who have undergone laryngectomies (removal of the larynx or voice box) or tracheostomies (removal of the trachea or windpipe) may experience hyposmia due to a reduction in or absence of nasal flow.

Central or Sensorineural Defects:

1. Infectious and inflammatory diseases like upper respiratory tract infections due to viruses, sarcoidosis, etc.

2. Trauma to head, any surgery of brain or subarachnoid hemorrhage may lead to a stretch, damage, or transaction of fila olfactoria or cause any damage to the brain parenchyma resulting in anosmia.

3. Age Changes: Elderly may have a loss of smell sensation.

4. Congenital syndromes like Kallmann syndrome.

5. Endocrine disturbances like hypothyroidism, hypoadrenalism, diabetes mellitus can also affect the smell sensation.

6. Systemic toxicity or inhalation of drugs like aminoglycosides, formaldehyde, etc.

7. Usage of over-the-counter zinc nasal sprays.

8. Neuropsychiatric disorders like depression.

9. Degenerative processes of the central nervous system like Parkinson's disease (PD), Alzheimer's disease, etc.

2. Gustatory Dysfunction:

1. Loss of taste sensation is related to loss of smell sensation. Apart from that, upper respiratory tract infections, head injury, and idiopathic causes may also contribute to loss of taste sensation.

2. Presence of lesions at any site ranging from the mucosa, taste buds, unmyelinated nerves, or cranial nerves to the brain stem.

3. Disorders of oral cavity and mucosa, including radiotherapy damage.

4. Poor oral hygiene maintenance.

5. Increase in age.

6. Certain medication usage.

7. Malignancies involving the head and neck.

8. Usage of dentures or any other palatal prosthesis.

9. Gastric bypass surgery.

10. Nutritional deficiencies (zinc, copper, etc.).

11. Endocrine disorders like diabetes mellitus, hypogonadism, Sjögren syndrome, pseudohypoparathyroidism, etc.

12. AIDS patients.

13. Genetic or hereditary.

14. Direct injury to the nerve or CNS (central nervous system) like in cases of multiple sclerosis, facial paralysis, etc.

COVID-19

These symptoms can also be experienced in patients suffering from COVID-19.

How Can These Disorders Be Diagnosed?

Initially, your physician will take a complete medical history and personal history regarding the signs and symptoms you are facing. Following that, a physical examination will be done, and various other tests will be performed as follows:

1. CT (computed tomography) scan.

2. MRI (magnetic resonance imaging).

3. Allergy evaluation.

4. Tests for diabetes mellitus.

5. Thyroid functions.

6. Renal and liver function.

7. Endocrine function.

8. Nutritional deficiencies.

9. Olfactory epithelium biopsy.

10. Clinical measurement of olfaction.

Clinical measurement of olfaction can be done using the following:

1. Butanol threshold test.

2. The University of Pennsylvania Smell Identification Test (UPSIT).

3. The Sniffin' Sticks test (Burghart Messtechnik GmbH).

4. Measurements of brain electric potentials.

Clinical measurement of taste can be done using the following:

1. Threshold detection.

2. Magnitude matching.

3. Spatial test.

How Can These Disorders Be Treated?

1. Treatment of Olfactory Dysfunction:

The treatment is first aimed to manage the cause of the condition and depends on the diagnosis made after the examination.

• Local nasal and/or sinus conditions can be managed using saline lavage, antibiotics, and/or nasal and systemic steroids if required, decongestants, and antihistamines.

• Nasal or any other polyps and sinus disease that could not be managed using medicines should be treated surgically.

• For endocrine disorders, administration of the deficient hormone can be done.

2. Treatment of Gustatory Dysfunction:

1. Treat the cause initially.

2. Manage the nasal pathology, which in turn can improve the taste sensation.

3. Management of mucosal disorders like candidiasis, glossitis, etc., using medicines.

4. Provision of mouthwashes.

5. Correct the ill-fitting dentures, if applicable.

6. In mucositis or dry mouth, due to radiation therapy, artificial saliva or salivary stimulants and local anti-inflammatory medications can be prescribed to improve the taste sensations.

7. Treating the underlying endocrine disorders.

Conclusion:

Loss of taste and smell can be very disturbing and may affect the quality of life. It can be caused due to various causes, and there are many options available to manage it. If diagnosed early, it can be managed on time and thus, improve the prognosis. Consult a specialist online to know more about this condition using the online medical platforms.