What could be causing a persistent increased smell of smoke in an adult with a history of Covid-19 infection?

Persistent Phantom Smoke Smell After COVID-19

This patient is most likely experiencing phantosmia (phantom smell perception), a form of post-viral olfactory dysfunction that occurs in a subset of COVID-19 patients who develop persistent chemosensory distortions rather than complete smell loss. 1, 2

Understanding the Condition

Phantosmia represents a qualitative olfactory distortion where patients perceive odors (commonly smoke, burning, or chemical smells) that are not present in the environment. 3 This differs from parosmia (distorted perception of actual odors) and complete anosmia (total smell loss). 4

Pathophysiology

The mechanism involves inflammation and potential dysfunction at multiple levels of the olfactory system: 2, 3

• Sustentacular cell infection and mucosal inflammation likely caused the initial acute smell changes 2
• Persistent dysfunction may reflect olfactory receptor neuron damage, olfactory bulb injury, or alterations in olfactory cortex processing 2, 3
• Chronic inflammation in intracranial olfactory structures has been documented on neuroimaging in patients with persistent deficits 3

Important caveat: While acute COVID-19 smell loss is well-documented, the exact mechanisms of persistent phantosmia years later remain incompletely understood. 2, 3

Diagnostic Workup

Mandatory Objective Testing

Do not rely on the patient's subjective assessment - objective psychophysical testing reveals dysfunction in 98.3% of patients even when only 35% report symptoms. 1

• Perform validated smell testing using UPSIT or Sniffin'Sticks (takes 4-25 minutes) 5
• Conduct rigid nasal endoscopy to rule out conductive causes (polyps, inflammation, obstruction) 5

When to Order Imaging

Order CT and MRI of skull base and brain only if psychophysical testing severity does not correlate with endoscopic findings, raising suspicion for occult sinonasal or skull base tumor. 5 Do not order neuroimaging when there is a clear temporal relationship to viral infection - this is unnecessary and wasteful. 1

Treatment Protocol

Primary Intervention: Olfactory Training

Initiate olfactory training immediately - this is the only intervention with consistent guideline support for post-viral olfactory dysfunction. 1, 5

• Continue for a minimum of 3-6 months 1, 5
• Refer to validated resources such as www.fifthsense.org.uk for proper technique 5
• Do not wait for spontaneous recovery - begin training at diagnosis 1

Adjunctive Management

Treat any underlying sinonasal inflammatory disease with appropriate medical or surgical management. 5

Do not prescribe topical corticosteroids routinely - the highest quality RCT showed no significant benefit over olfactory training alone. 1 Given the immunocompromised state and potential respiratory complications in COVID-19 patients, steroid use should be particularly cautious. 6

Nutritional Support

Refer to a registered dietitian for counseling on: 1, 7

• Flavor enhancement techniques
• Additional seasoning strategies
• Expanding dietary options to maintain adequate nutrition

Critical Safety Counseling

Address safety concerns immediately - this is not optional. 1, 8

Patients with persistent chemosensory dysfunction face real-world risks: 8

• 45% cannot detect smoke that others perceive 8
• 57% report at least one safety-related event 8
• 36% report 2 or more safety events 8

Specific safety recommendations to discuss:

• Install working smoke detectors and carbon monoxide alarms
• Check expiration dates on food rather than relying on smell
• Have others check for gas leaks
• Be cautious with cooking (risk of burning food undetected)

Quality of Life Impact

Recognize the substantial burden - 96% of COVID-19 patients with chemosensory loss report at least one quality of life deficit, and 75% report at least 3 deficits. 8

• 87% report reduced enjoyment of food 8
• 43% self-report depression 8

This is not a minor inconvenience - it warrants serious clinical attention and support. 8

Follow-Up Schedule

Re-evaluate at structured intervals: 1, 5

• 1 month after initiating treatment
• 3 months after initiating treatment
• 6 months after initiating treatment

Repeat objective psychophysical testing at each visit to document changes - do not rely on patient self-assessment. 5

Referral Criteria

Refer to an otolaryngologist or specialized smell/taste clinic if no improvement occurs after 3-6 months of olfactory training. 1, 5

Prognosis

Recovery timeline is variable: 5

• 44-73% of COVID-19 patients recover within the first month 1, 5
• Mean improvement time is 7.2 days for those who recover early 1
• However, persistent dysfunction requiring ongoing management occurs in a significant subset 5

Long-term consideration: Persistent olfactory impairment with perceptual distortions (phantosmias) after COVID-19 could potentially serve as a marker for increased long-term risk of neurological disease, though this remains speculative. 3