What is the workup for a patient presenting with anosmia?

Diagnostic Workup for Anosmia

A comprehensive diagnostic workup for anosmia should include objective smell testing, nasal endoscopy, and targeted imaging studies to determine etiology and guide treatment decisions. 1

Initial Assessment

History Taking

• Duration and onset of smell loss (sudden vs. gradual)
• Associated symptoms (nasal congestion, rhinorrhea, facial pain)
• Recent upper respiratory infections, including COVID-19
• History of head trauma
• Exposure to toxins or medications
• Neurological symptoms
• Comorbidities (allergies, sinonasal disease, neurodegenerative disorders)

Physical Examination

• Complete nasal examination
• Cranial nerve examination
• Neurological examination

Objective Testing

Validated Smell Tests

• University of Pennsylvania Smell Identification Test (UPSIT)
• Sniffin' Sticks
• Validated abbreviated smell tests

These standardized psychophysical tests are mandatory to objectively assess olfactory function, as patients frequently underestimate their impairment 1, 2. Testing should evaluate:

• Odor threshold
• Odor discrimination
• Odor identification

Diagnostic Procedures

Nasal Endoscopy

Essential to evaluate:

• Nasal mucosa
• Presence of polyps
• Structural abnormalities
• Signs of inflammation
• Olfactory cleft patency

Imaging Studies

Based on clinical findings, the following may be indicated:

1. CT Maxillofacial

   • Indicated for:
     • Structural abnormalities
     • Inflammatory sinonasal disease
     • History of trauma
     • No improvement with initial treatment

2. MRI Brain/Olfactory Bulbs

   • Indicated for:
     • Intracranial or skull base pathology
     • Congenital anosmia
     • Olfactory bulb volume assessment
     • No obvious cause on endoscopy and CT
     • Suspected neurodegenerative disease

MRI is the most widely studied imaging modality for olfactory dysfunction, but criteria for timing and sequence selection vary 2.

Etiological Classification

Inflammatory Causes

• Chronic rhinosinusitis with/without polyps
• Allergic rhinitis
• Viral infections (including COVID-19)
  • COVID-19-related anosmia prevalence: 11.8-26.6% 1

Structural Causes

• Nasal polyps
• Tumors (sinonasal, skull base)
• Trauma-related damage

Neurological Causes

• Post-viral olfactory dysfunction
• Head trauma
• Neurodegenerative diseases (Parkinson's, Alzheimer's)

Other Causes

• Medication-induced
• Toxic exposure
• Congenital disorders
• Age-related decline

Treatment Approach

Treatment should be directed at the underlying cause:

For Inflammatory Causes

• Intranasal corticosteroids: 2 sprays in each nostril once daily for at least 3 weeks 1, 3
  • Best administered in head-down-forward position for improved delivery to olfactory cleft 3
• Systemic corticosteroids: For severe cases (0.25-0.5 mg/kg for 1-3 weeks with tapering) 1
• Treatment of underlying conditions (e.g., antibiotics for bacterial sinusitis)

For Post-Viral/Post-Traumatic Causes

• Olfactory training: Exposure to different odors twice daily for at least 12 weeks 1
• Combined approach with intranasal corticosteroids may improve outcomes

For Structural Causes

• Surgical intervention when appropriate

Prognosis and Follow-up

• Approximately 30% of patients show improvement within 6 months
• Recovery can continue for up to 2 years post-injury
• Complete recovery is less common with severe initial dysfunction
• Regular follow-up with repeat smell testing to monitor progress

Special Considerations

Post-Traumatic Anosmia

• Associated with greater impairment in frontal-lobe mediated executive functions 4
• Only 30% of patients with post-traumatic anosmia are aware of their deficit 4
• May indicate more severe brain injury

Chronic Sinusitis

• Severity of sinus disease correlates with persistence of anosmia
• Patients with disease extending beyond the ethmoids have poorer prognosis 5
• Endoscopic sinus surgery may improve smell in approximately 52% of patients 5

Safety Concerns

Patients with persistent anosmia should be advised about:

• Installing gas and smoke alarms
• Checking food expiration dates carefully
• Being cautious with gas appliances 1

Common Pitfalls to Avoid

1. Relying solely on patient self-report without objective testing
2. Failing to distinguish between smell and taste disorders (patients often report "taste loss" when experiencing smell dysfunction)
3. Missing serious underlying pathology (tumors, neurodegenerative diseases)
4. Using inadequate imaging protocols that don't specifically evaluate the olfactory apparatus
5. Not considering COVID-19 as a potential cause in the current pandemic context

By following this systematic approach to the workup of anosmia, clinicians can accurately diagnose the underlying cause and implement appropriate treatment strategies to improve outcomes and quality of life.