What is the appropriate evaluation and management for a patient presenting with phantosmia (e.g., smelling burning odors without an actual source)?

Evaluation and Management of Phantosmia (Phantom Burning Smells)

Begin with rigid nasal endoscopy and standardized psychophysical olfactory testing (UPSIT or Sniffin' Sticks) to objectively characterize the dysfunction and rule out sinonasal pathology before considering imaging. 1, 2

Initial Clinical Assessment

The evaluation should focus on distinguishing phantosmia (smelling odors without a source) from parosmia (distorted smells with a trigger present) and determining whether the phantom smell is unilateral or bilateral, as this guides further workup 1, 3, 4:

• Perform rigid nasal endoscopy to exclude conductive causes including sinonasal obstruction, inflammatory disease (rhinosinusitis, nasal polyps), and tumors that may not be visible on anterior rhinoscopy 1, 2
• Conduct standardized olfactory testing using validated instruments (UPSIT or Sniffin' Sticks) because patients cannot reliably self-assess their olfactory function 1, 2
• Obtain detailed history focusing on:
  • Recent upper respiratory infections, particularly COVID-19 5, 1
  • Trauma history (olfactory nerve is most commonly disrupted by trauma) 5
  • Temporal relationship to headaches (phantosmia can be a migraine aura, typically lasting 5-60 minutes with burning smell) 6
  • Medications and toxic exposures 7, 4
  • Neurological symptoms suggesting temporal lobe dysfunction or neurodegenerative disease 5, 1, 2

When to Pursue Imaging

MRI orbits, face, and neck (with and without contrast) is the preferred imaging modality when structural pathology is suspected. 5, 1

Imaging is indicated when 1, 2:

• Discordance exists between subjective symptoms and endoscopic findings
• Progressive or persistent symptoms without clear inflammatory or obstructive cause
• Associated neurological signs suggesting central nervous system pathology (temporal lobe lesions, neurodegenerative disease)
• Unilateral phantosmia with ipsilateral olfactory loss (suggests peripheral pathology) 3

CT head or vascular imaging has no established role in olfactory evaluation and should be avoided unless specific red-flag findings are present. 1, 2 CT maxillofacial may be useful specifically for evaluating fractures, paranasal sinus inflammatory disease, and bony anatomy 5.

Common Etiologies to Consider

Peripheral Causes

• Post-infectious olfactory dysfunction (including COVID-19, which has caused a surge in qualitative olfactory disorders) 5, 1, 7
• Sinonasal inflammatory disease (chronic rhinosinusitis, nasal polyposis) 1, 2
• Traumatic brain injury 7, 4

Central Causes

• Temporal lobe pathology (tumors, epilepsy) requiring neurological evaluation 5, 1, 2
• Neurodegenerative disorders (Alzheimer's, Parkinson's, Lewy body dementia) 1, 2
• Migraine aura (typically burning smell lasting 5-60 minutes before headache onset) 6
• Psychiatric disorders including schizophrenia 7, 4

Other Causes

• Medications and toxic chemicals 7, 4
• Skull base tumors (meningiomas, esthesioneuroblastoma affecting cribriform plate) 1
• Inflammatory lesions (sarcoidosis, granulomatosis with polyangiitis) 1

Treatment Approach

For Post-Infectious Phantosmia (Including COVID-19)

Offer olfactory training as first-line therapy due to its safety, simplicity, and demonstrated efficacy. 5, 1, 2 Modified olfactory training has been shown effective for COVID-19-induced parosmia and should be recommended for qualitative disorders 7.

Provide safety counseling regarding 5:

• Installation of smoke and gas alarms
• Careful attention to food expiration dates
• Caution with cooking

For Inflammatory Sinonasal Disease

Anti-inflammatory therapy improves olfactory function in chronic rhinosinusitis patients, with serial smell testing to track recovery. 2

For Persistent or Refractory Cases

Treatment options include 3:

• Topical medications to the nasal mucosa
• Systemic medications (though evidence is limited)
• Anesthesia to parts of the nose in select cases
• Rarely, surgical excision of olfactory neurons via endoscopic transnasal approach (may allow return of olfactory ability post-operatively)

For Migraine-Associated Phantosmia

Initiation of prophylactic headache therapy typically diminishes or eliminates phantosmias. 6

Critical Pitfalls to Avoid

• Do not assume all phantosmia requires imaging—most cases do not need advanced imaging unless clinical examination warrants it 1, 2
• Do not rely on patient self-assessment of olfactory function; objective testing is essential 1, 2
• Do not overlook temporal lobe pathology in patients with persistent olfactory hallucinations, as this may signal serious neurological disease 5, 1, 2
• Do not order CT head or vascular imaging routinely, as these have no established role in olfactory evaluation 1, 2
• Document pre-operative olfactory assessment before any nasal surgery for medico-legal protection 2

Follow-Up and Monitoring

• Provide rhinology follow-up after acute phase, particularly for post-infectious cases 5
• Consider MRI only if concerning symptoms develop or if there is no clear temporal relationship to viral infection 5
• Refer for multidisciplinary management when neurodegenerative conditions are suspected 2
• Reassure patients that many qualitative olfactory disorders resolve naturally over time, though recovery duration varies 7, 3