What is the evaluation and treatment approach for patients with loss of taste and smell?

Evaluation of Patients with Loss of Taste and Smell

Most patients with loss of taste and smell do not require imaging unless history or physical examination reveals concerning features; the evaluation should begin with objective psychophysical testing using validated instruments (UPSIT or Sniffin' Sticks) combined with rigid nasal endoscopy, followed by COVID-19 testing in cases of sudden onset. 1, 2, 3

Initial Clinical Assessment

History Taking

• Document the precise onset, duration, and temporal relationship to viral infections, particularly COVID-19, as post-viral olfactory loss accounts for 20-25% of cases presenting to specialist clinics 3
• Identify associated symptoms including nasal obstruction, rhinorrhea, flu-like illness, or recent head trauma 1
• Review all medications, as they commonly interfere with chemosensory function 4
• Note that patients typically confuse "taste" complaints with olfactory dysfunction—true taste loss involves only bitter, sweet, salty, sour, or umami, while flavor perception requires intact olfaction 5

Physical Examination

• Perform thorough nasal and neurological examination focusing on signs of sinonasal obstruction or inflammation 1, 2
• Conduct rigid nasal endoscopy to differentiate conductive (obstructive) from sensorineural causes 3

Objective Testing

Mandatory Psychophysical Testing

• Administer validated smell tests (UPSIT or Sniffin' Sticks) in all patients, as they cannot accurately assess their own degree of impairment 3
• These tests have high test-retest reliability and take 4-25 minutes to complete 3
• Objective testing is mandatory rather than optional (high strength of evidence) 3

COVID-19 Screening

• Perform COVID-19 testing in all patients with sudden-onset taste/smell loss, especially during pandemic periods, as olfactory dysfunction may be the sole presenting symptom with high specificity (98.7%) 1, 2, 3
• Recovery occurs in 44-73% of COVID-19 patients within the first month, though some develop persistent dysfunction 1, 2, 3

Imaging Considerations

When Imaging is NOT Needed

• Most patients with olfactory symptoms do not require imaging unless history or physical examination warrants it 1
• Avoid unnecessary neuroimaging when there is a clear temporal relationship to viral infection 2

When to Order Imaging

• Order MRI of orbits, face, and neck (preferred over MRI head) when psychophysical testing severity does not correlate with endoscopic findings, raising suspicion for occult sinonasal or skull base tumor 1, 3
• CT maxillofacial without contrast is useful to evaluate fractures, paranasal sinus inflammatory disease, and bony anatomy impacting olfaction 1
• Add contrast to CT only when evaluating granulomatous or neoplastic disease 1

Common Etiologies by Category

Conductive Loss (Sinonasal Obstruction)

• Rhinosinusitis with nasal polyposis—severity on CT correlates with worse olfaction 1
• Obstructing polyps or masses 4

Sensorineural Loss (Olfactory Neuroepithelial Damage)

• Post-viral (most common: upper respiratory infections, COVID-19) 1, 6
• Head trauma 1, 4, 7
• Aging (natural impairment) 1, 4
• Idiopathic (26% of cases) 6

Central Nervous System Disorders

• Tumors affecting cribriform plate (squamous cell carcinomas, meningiomas, esthesioneuroblastoma) 1
• Inflammatory lesions (sarcoidosis, granulomatosis with polyangiitis) 1
• Neurodegenerative diseases (Alzheimer disease, Parkinson disease) 1, 8

Treatment Approach

Reversible Causes

• Treat sinonasal inflammatory disease with appropriate medical or surgical management—this is the most amenable cause to treatment 1, 3, 4
• Excise obstructing polyps or masses 4
• Trial of corticosteroids to confirm inflammatory etiology; smell return after corticosteroid course indicates reversible cause 7

Persistent Dysfunction

• Start olfactory training immediately and continue for a minimum of 3-6 months (moderate strength of evidence) 2, 3
• Refer to registered dietitian for counseling on flavor enhancement, additional seasoning, and expanding dietary options 2, 3

Follow-Up Protocol

• Re-evaluate at 1 month, 3 months, and 6 months after initiating treatment 2, 3
• Repeat psychophysical testing at follow-up visits to objectively document changes 3
• Refer to otolaryngologist or specialized smell/taste clinic if no improvement after 3-6 months 2, 3

Critical Safety Counseling

• Address safety concerns related to inability to detect spoiled food, gas leaks, or smoke 2, 7
• Counsel patients on these dangers if restoration of smell is unlikely 7

Common Pitfalls to Avoid

• Do not overlook COVID-19 as a potential cause, especially when taste/smell loss is the primary or isolated symptom 1, 2
• Do not rely on patient self-assessment of impairment severity—objective testing is mandatory 3
• Do not confuse patient complaints of "taste loss" with true gustatory dysfunction—most are olfactory problems 5
• Do not order CT head or CTA head, as there is no relevant literature supporting their use in olfactory nerve evaluation 1