Evaluation Approach for Loss of Sense of Smell and Taste
A comprehensive diagnostic approach for anosmia and ageusia should include objective smell testing, nasal endoscopy, and imaging when indicated, with particular attention to ruling out COVID-19 infection, inflammatory conditions, and structural abnormalities. 1
Initial Assessment
History
- Onset and duration of symptoms (sudden vs. gradual)
- Associated symptoms (nasal obstruction, rhinorrhea, facial pain)
- Recent upper respiratory infections, especially COVID-19
- History of head trauma
- Medication review (may interfere with smell/taste)
- Exposure to toxins or chemicals
- Previous sinonasal surgeries
- Fluctuation of symptoms
Physical Examination
- Complete nasal endoscopy to evaluate:
- Presence of polyps
- Inflammatory changes
- Masses or tumors
- Olfactory cleft patency
- Structural abnormalities
Objective Testing
Smell Testing
- Standardized psychophysical testing is essential as patients often cannot accurately assess their degree of impairment 1
- Recommended validated tests:
- North American UPSIT (University of Pennsylvania Smell Identification Test)
- Sniffin' Sticks (European standard)
- Brief versions: SIT, B-SIT for screening
Taste Testing
- Distinguish between true gustatory loss (bitter, sweet, salty, sour, umami) and flavor perception (which requires smell)
- Spatial testing of tongue and palate may reveal gustatory nerve pathology
COVID-19 Consideration
- COVID-19 should be considered as a primary cause of sudden anosmia, especially when presenting as an isolated or early symptom 1
- Anosmia may present before other symptoms in 11.8-26.6% of COVID-19 cases
- Recovery rates vary: 13-44% complete resolution, 14% partial resolution
- Mean recovery time: 7.2 days, though some cases persist longer 1, 2
Imaging Studies
CT of maxillofacial area is indicated when:
- Endoscopy reveals structural abnormalities
- Suspicion of inflammatory sinonasal disease
- History of trauma
- No improvement with initial treatment 1
MRI of 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 1
Common Etiologies to Consider
Inflammatory
- Chronic rhinosinusitis with/without polyps
- Allergic rhinitis
- COVID-19 and other viral infections
Structural
- Nasal polyps
- Tumors (sinonasal, skull base)
- Trauma-related damage
Neurological
- Post-viral olfactory dysfunction
- Head trauma
- Neurodegenerative diseases (Parkinson's, Alzheimer's)
Other
- Medication-induced
- Toxic exposure
- Congenital disorders
- Aging-related decline
Treatment Considerations
For COVID-19 related anosmia:
- Olfactory training is first-line treatment
- Consider intranasal corticosteroids in combination with olfactory training
- Begin treatment as soon as possible after acute COVID-19 phase 2
For inflammatory causes:
- Intranasal corticosteroids
- Systemic corticosteroids in select cases
- Treatment of underlying condition (e.g., rhinosinusitis)
For structural causes:
- Surgical intervention when appropriate
Patient Safety Counseling
Patients with persistent anosmia should be advised about:
- Installing gas and smoke alarms
- Checking food expiration dates carefully
- Being cautious with gas appliances 2
Pitfalls to Avoid
- Failing to distinguish between smell and taste disorders - Patients often report "taste loss" when experiencing smell dysfunction
- Relying solely on patient self-report - Objective testing is essential as patients frequently underestimate their impairment
- Missing COVID-19 diagnosis - Anosmia may be the earliest or only symptom
- Overlooking serious underlying pathology - Tumors or neurodegenerative diseases may present with anosmia
- Inadequate imaging - CT protocols should specifically include the olfactory cleft and cribriform plate
By following this structured approach, clinicians can effectively evaluate and manage patients with anosmia and ageusia, potentially improving outcomes and quality of life.