Loss of Smell

Aka: Loss of Smell, Smell Dysfunction, Anosmia, Hyposmia, Parosmia, Olfactory Dysfunction

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II. Physiology

  1. See Smell Sensation
  2. See Taste Sensation

III. Definition

  1. Anosmia
    1. Sense of Smell lost completely
  2. Hyposmia
    1. Reduced Sense of Smell
  3. Parosmia
    1. Distorted Sense of Smell
  4. Phantosmia
    1. Olfactory Hallucination (without external odor stimulus)

IV. Risk Factors

  1. Advancing age
  2. Male gender
  3. Tobacco Abuse

V. Exam: General

  1. Nasopharynx (Anterior rhinoscopy)
    1. Allergic Rhinitis
    2. Sinusitis
    3. Nasal Polyposis
  2. Oral pharynx
    1. Xerostomia
    2. Oral Candidiasis
    3. Gingivitis or Periodontal Disease
    4. Glossitis
  3. Neurologic Exam
    1. Test Cranial Nerve 7, Cranial Nerve 9 and Cranial Nerve 10
    2. Cognitive Exam
    3. Motor Exam

VI. Exam: Screening for Olfactory Dysfunction (Cranial Nerve I)

  1. Confirm that nares are patent prior to testing
  2. Patient closes eyes and occludes one nare
    1. Test for recognition of common substances
    2. Examples: Cloves, coffee, soap, vanilla, rose
    3. Various prepared items are available that give off odor (Quick Sticks, q-Sticks, Sniffin' Sticks)

VII. Imaging

  1. Nasolaryngoscopy
  2. Maxillofacial Sinus CT
  3. Consider Head CT or Brain MRI

VIII. Causes: Loss of Smell due to local nasal causes (most common)

  1. Allergic Rhinitis
  2. Upper Respiratory Infection
  3. Nasal Polyposis
  4. Sinusitis
  5. Less common local causes
    1. Nasal surgery (e.g. septoplasty, Sinus Surgery)
    2. Tonsillectomy
    3. Head and neck radiation

IX. Causes: Loss of Smell due to Neurologic Conditions (common)

  1. Head Trauma
    1. Injury to Cribiform Plate (especially shearing force)
    2. Maxillofacial Trauma
  2. Neurodegenerative disorders
    1. Multiple Sclerosis
    2. Parkinson's Disease
    3. Alzheimer's Disease
  3. Other less common neurologic causes
    1. Frontal tumor
    2. Korsakoff's Psychosis
    3. Cerebrovascular Accident
    4. Intracranial Hemorrhage

X. Causes: Loss of Smell due to Systemic Conditions (less common causes)

  1. Organ failure
    1. Renal Failure
    2. Hepatic failure
  2. Infectious Disease
    1. Viral Hepatitis
    2. Influenza
    3. HIV Infection
    4. Herpes Encephalitis
  3. Endocrine disorders
    1. Cushing's Syndrome
    2. Hypothyroidism
    3. Diabetes Mellitus
  4. Rheumatologic Conditions
    1. Sjogren Syndrome
    2. Systemic Lupus Erythematosus
    3. Sarcoidosis
  5. Malnutrition or Vitamin Deficiency
    1. Vitamin B12 Deficiency
    2. Vitamin B6 Deficiency
    3. Zinc Deficiency
    4. Copper Deficiency
  6. Genetic disorders
    1. Kallmann's Syndrome
  7. Psychiatric Disorders
    1. Anorexia Nervosa
    2. Major Depression
    3. Bipolar Disorder
    4. Schizophrenia
  8. Substances of abuse
    1. Tobacco smoke
    2. Alcohol Abuse
    3. Amphetamines
    4. Topical Cocaine
  9. Medications
    1. See Drug-Induced Olfactory Dysfunction
  10. Toxins
    1. Hydrocarbons
      1. Benzene
      2. Gasoline
      3. Paint solvents
      4. Formaldehyde
    2. Heavy Metals
      1. Iron
      2. Cadmium
      3. Chromium
      4. Lead
      5. Mercury
      6. Welding agents
    3. Miscellaneous chemicals
      1. Acrylates
      2. Ammonia
      3. Salon chemicals (hair dressing)

XI. Management: Approach

  1. Distinguish Gustatory Dysfunction from Olfactory Dysfunction
    1. Olfactory Dysfunction in 95% of cases
  2. Evaluate for specific cause
    1. Consider olfactory testing (see exam above) if available
    2. Eliminate reversible causes (see above)
    3. See Drug-Induced Olfactory Dysfunction
  3. Evaluate and treat nasal and sinus disorders
    1. Consider Nasal Corticosteroid trial for 8 weeks
      1. Indicated for suspected Allergic Rhinitis, Chronic Sinusitis or Nasal Polyposis
    2. Consider otolarygology Consultation
    3. Consider Sinus CT
  4. Evaluate for neurodegenerative disease
    1. Consider neurology Consultation
    2. Consider Brain MRI
  5. Symptomatic management
    1. Consider olfactory training twice daily for 12 weeks
    2. Involves smelling 4 odors (phenyethyl Alcohol, eucalyptol, citronellal, eugenol)
    3. Hummel (2009) Laryngoscope 119(3) 496-9 [PubMed]

XII. References

  1. Baloh in Goldman (2000) Cecil Medicine, p. 2249-50
  2. Snow in Wilson (1991) Harrison's Internal Med, p. 152
  3. Malaty (2013) Am Fam Physician 88(1): 852-9 [PubMed]

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