What is the diagnostic workup for a patient presenting with changes in olfactory (smell) senses?

Diagnostic Workup for Olfactory Sense Changes

A comprehensive diagnostic workup for olfactory dysfunction should include objective smell testing, nasal endoscopy, and imaging when indicated, with particular attention to ruling out inflammatory conditions, structural abnormalities, and neurological causes. 1

Initial Clinical Assessment

• Detailed history focusing on:

  • Onset (sudden vs. gradual)
  • Pattern (fluctuating vs. constant)
  • Associated symptoms (nasal obstruction, rhinorrhea)
  • History of trauma, upper respiratory infections, COVID-19
  • Medication use
  • Exposure to toxins
  • Neurological symptoms

• Nasal endoscopy is essential as anterior rhinoscopy alone misses pathology in 51% of cases 2

  • Evaluate for:
    • Sinonasal inflammatory disease
    • Nasal polyps
    • Tumors affecting the cribriform plate
    • Structural abnormalities

Objective Olfactory Testing

• Standardized psychophysical testing is mandatory as patients often cannot accurately assess their degree of impairment 3, 1

• Recommended validated tests:

  • North American UPSIT (University of Pennsylvania Smell Identification Test)
  • Sniffin' Sticks (European standard)
  • Brief versions: SIT, B-SIT for screening 3, 1

• Tests should include assessment of:

  • Odor threshold (minimum concentration detection)
  • Odor discrimination (differentiating between odors)
  • Odor identification (naming or recognizing odors) 3

Imaging Studies

• CT Maxillofacial is indicated when:

  • Endoscopy reveals structural abnormalities
  • Suspicion of inflammatory sinonasal disease
  • History of trauma
  • No improvement with initial treatment 3, 1

  CT protocols should specifically include the olfactory cleft and cribriform plate 1

• MRI Brain/Olfactory Bulbs is indicated when:

  • Suspicion of intracranial or skull base pathology
  • Congenital anosmia is suspected
  • Olfactory bulb volume assessment is needed
  • No obvious cause is found on endoscopy and CT 3, 1
  • Neurodegenerative disorders are suspected (Parkinson's, Alzheimer's) 3

Diagnostic Challenge Testing

• Systemic corticosteroid trial can be diagnostic for inflammatory causes
  • Temporary reversal of conductive olfactory loss occurs in 83% of patients with inflammatory etiology 2
  • Response confirms conductive/inflammatory nature of dysfunction

Special Considerations

• COVID-19 screening should be considered in cases of sudden anosmia, especially when presenting as an isolated or early symptom 1

• FDG-PET/CT and functional MRI remain largely investigative and are not generally used in routine evaluations 3

Common Diagnostic Pitfalls

1. Failing to distinguish between smell and taste disorders - patients often report "taste loss" when experiencing smell dysfunction 1

2. Relying solely on patient self-report - objective testing is essential as patients frequently underestimate their impairment 3, 1

3. Inadequate physical examination - anterior rhinoscopy alone is insufficient; nasal endoscopy is crucial 2

4. Missing serious underlying pathology - tumors or neurodegenerative diseases may present with anosmia 3, 1

5. Inadequate imaging protocols - CT and MRI must specifically evaluate the olfactory apparatus 3

By following this systematic approach, clinicians can accurately diagnose the underlying cause of olfactory dysfunction and guide appropriate treatment to improve patient outcomes related to morbidity, mortality, and quality of life.