Is a non-contrast computed tomography (NCCT) scan required to exclude Bell's palsy?

Diagnostic Imaging for Bell's Palsy

No, you do not need to perform a non-contrast CT (NCCT) scan to exclude Bell's palsy—routine diagnostic imaging is explicitly NOT recommended for new-onset Bell's palsy. 1, 2

Primary Diagnostic Approach

Bell's palsy is a clinical diagnosis based on history and physical examination alone. 1, 2 The American Academy of Otolaryngology-Head and Neck Surgery provides a strong recommendation against routine diagnostic imaging for patients presenting with typical Bell's palsy features. 1

Key diagnostic criteria that do NOT require imaging: 1, 2

• Acute onset of unilateral facial weakness developing over less than 72 hours
• Involvement of the forehead (distinguishing it from central/stroke causes)
• No other cranial nerve abnormalities
• No identifiable cause on history and physical examination

When Imaging IS Indicated

MRI with and without contrast (not NCCT) becomes the imaging test of choice only in these specific atypical scenarios: 1, 2

• Atypical presentations requiring imaging: 1

  • Second episode of paralysis on the same side
  • Isolated paralysis of individual facial nerve branches (not complete hemifacial involvement)
  • Other cranial nerve involvement beyond CN VII
  • Bilateral facial weakness
  • History of trauma to the temporal bone
  • Known history of malignancy

• Failed recovery scenarios: 1, 2

  • No sign of recovery after 3 months
  • Progressive worsening of paralysis at any point
  • New neurologic findings developing during follow-up

Why NCCT Is Inadequate

When imaging is truly needed, CT is inferior to MRI for evaluating the facial nerve. 1 CT provides useful information only for: 1

• Temporal bone fractures and trauma
• Presurgical osseous anatomy
• Inflammatory middle ear disease with bone involvement

MRI is superior because it: 1

• Directly visualizes the entire intracranial and extracranial course of CN VII
• Detects enhancement patterns in neuritis
• Identifies tumors, schwannomas, meningiomas, and perineural spread
• Excludes brainstem pathology (infarction, multiple sclerosis, vascular malformations)

Common Pitfalls to Avoid

Do not order imaging "just to be safe" in typical Bell's palsy presentations. 1 This approach:

• Exposes patients to unnecessary radiation (particularly problematic in children) 1
• Generates false-positive findings requiring costly workups 1
• Delays appropriate treatment with corticosteroids 2
• Costs hundreds to thousands of dollars without clinical benefit 1

Do not use head CT instead of dedicated temporal bone imaging if CT is truly indicated (e.g., trauma). 1 A dedicated temporal bone CT with thin sections is required to properly evaluate CN VII course. 1

Do not delay treatment waiting for imaging results in typical presentations. 2 Oral corticosteroids must be initiated within 72 hours of symptom onset for maximum benefit. 1, 2

Practical Algorithm

1. Perform thorough history and physical examination looking specifically for: 1, 2

   • Onset timeline (must be <72 hours for typical Bell's palsy)
   • Forehead involvement (present in Bell's palsy, absent in stroke)
   • Other cranial nerve deficits (absent in Bell's palsy)
   • Trauma history, tumor history, or systemic symptoms

2. If presentation is typical Bell's palsy: 1, 2

   • No imaging required
   • Start oral corticosteroids immediately (prednisolone 50-60 mg daily)
   • Implement eye protection measures
   • Schedule follow-up

3. If ANY atypical features present: 1

   • Order MRI of the entire facial nerve course with and without contrast
   • Include internal auditory canal and face in imaging protocol
   • If MRI contraindicated, use contrast-enhanced CT (not NCCT)

4. If typical presentation but no recovery at 3 months: 1, 2

   • Order MRI with and without contrast
   • Refer to facial nerve specialist

The evidence is unequivocal: routine imaging for typical Bell's palsy presentations wastes resources, delays treatment, and provides no clinical benefit. 1, 2