Olfactory Receptor Damage and Anosmia: Causes, Consequences, and Evaluation

Anosmia: Loss of Smell

Damage to olfactory receptors (bipolar neurons in olfactory epithelium) causes **anosmia** – partial (hyposmia) or complete loss of smell.

Common Causes

Category	Examples
Post-viral	COVID-19 (very common), influenza, other URI
Sinonasal	Chronic rhinosinusitis (CRSwNP/CRSsNP), polyps, allergic rhinitis
Traumatic	Head injury (shear of fila olfactoria), nasal surgery
Neurodegenerative	Parkinson's, Alzheimer's, Lewy body – often early sign
Toxic/Medication	Intranasal zinc, long-term topical decongestants, chemo, some antibiotics
Congenital	Kallmann syndrome (anosmia + hypogonadism)
Neoplastic	Olfactory neuroblastoma, meningioma, frontal lobe glioma
Aging	Presbyosmia (gradual decline >60)

Consequences

• Flavor loss (taste + smell = flavor) → appetite/weight changes.
• Safety hazards: gas leaks, smoke, spoiled food.
• Quality of life: depression, social isolation, loss of pleasure.
• Occupational impact: chefs, perfumers, firefighters.

Evaluation

1. History: onset, progression, associated symptoms, meds, trauma.
2. Exam: nasal endoscopy (polyps, inflammation, anatomy).
3. Olfactory testing: UPSIT, Sniffin' Sticks, or simple odor ID.
4. Imaging: MRI brain (olfactory bulbs, tracts) ± CT sinuses.
5. Labs: TSH, B12, zinc, ANA if indicated.

Treatment

• Treat underlying cause (steroids for CRSwNP, surgery for polyps).
• Olfactory training (essential oils 2×/day × 12+ weeks) – best evidence for post-viral/traumatic.
• Topical/oral steroids (short course) for inflammatory.
• No proven pharmacologic regeneration.

Sudden anosmia = urgent evaluation (COVID, tumor, stroke). Gradual = ENT/neurology workup.