Do you still use Computed Tomography (CT) or Computed Tomography Angiography (CTA) in the Emergency Department (ED) for suspected Bell's palsy?

CT/CTA Imaging for Suspected Bell's Palsy in the Emergency Department

No, you should NOT routinely perform CT or CTA imaging in the ED for suspected Bell's palsy. 1

Primary Diagnostic Approach

The diagnosis of Bell's palsy is clinical and requires only a thorough history and physical examination to exclude other identifiable causes of facial weakness. 1, 2

Key Clinical Features to Confirm Bell's Palsy

• Acute unilateral facial weakness involving the forehead (distinguishes from central causes where forehead is spared) developing over less than 72 hours 2, 3
• No other cranial nerve involvement - presence of other cranial nerve deficits suggests alternative diagnosis 1
• Normal otoscopic examination - no evidence of otitis media or mastoiditis 4
• No skin vesicles or blisters - rules out herpes zoster (Ramsay Hunt syndrome) 4
• No parotid mass - excludes parotid tumor causing facial nerve compression 4
• No history of trauma - temporal bone fracture must be excluded 2

When Imaging IS Indicated

MRI with and without contrast (not CT/CTA) should be obtained only when clinical features are atypical: 1, 2

• Second episode of paralysis on the same side 1, 2
• Isolated paralysis of individual facial nerve branches (rather than complete hemifacial involvement) 1, 2
• Other cranial nerve involvement (diplopia, dysphagia, dizziness) 1
• No sign of recovery after 3 months 1, 2
• Progressive worsening after initial presentation 1, 2
• Bilateral facial weakness (highly atypical for Bell's palsy) 1
• History suggestive of tumor or temporal bone trauma 1, 2

Evidence Supporting No Routine Imaging

The American Academy of Otolaryngology-Head and Neck Surgery explicitly recommends against routine diagnostic imaging for new-onset Bell's palsy based on: 1

• Radiation exposure risk, particularly concerning in children, with the American College of Radiology advising against imaging unless clear medical benefit outweighs risk 1
• High cost ranging from hundreds to thousands of dollars without changing management 1
• Very low misdiagnosis rate of only 0.8% in a large California study of 43,979 ED patients discharged with Bell's palsy diagnosis 5
• No impact on acute management since treatment (oral steroids within 72 hours) is the same regardless of imaging findings 2, 3

Real-World Context

In the ED setting, approximately 70% of acute facial palsies are Bell's palsy, meaning 30% have alternative causes. 1 However, these alternative diagnoses are identified through careful history and physical examination, not routine imaging. 1

Alternative Diagnoses to Consider Clinically

• Stroke - look for forehead sparing, other neurologic deficits, sudden onset 2, 5
• Herpes zoster (Ramsay Hunt) - vesicles in ear canal or on tongue, severe otalgia 5
• Lyme disease - endemic area exposure, erythema migrans, bilateral facial palsy 1
• Guillain-Barré syndrome - bilateral weakness, areflexia, ascending paralysis 5
• Otitis media/mastoiditis - abnormal otoscopy, ear pain, fever 5

Critical Pitfalls to Avoid

• Ordering CT/CTA "just to be safe" exposes patients to unnecessary radiation and cost without changing management 1
• Failing to examine forehead function - this is the single most important distinguishing feature from central causes 2, 3
• Missing bilateral involvement - this is never Bell's palsy and requires immediate workup for Guillain-Barré, Lyme disease, or other systemic causes 1
• Delaying steroid treatment while waiting for imaging - treatment must begin within 72 hours for maximum benefit 2, 3
• Using CT instead of MRI when imaging is indicated - MRI with contrast is the test of choice for evaluating the facial nerve course when atypical features are present 1, 2

Appropriate ED Management Algorithm

1. Complete history and physical focusing on onset timing, trauma, infection symptoms, other cranial nerves, forehead involvement 1, 2
2. If typical Bell's palsy (unilateral, forehead involved, no other deficits, acute onset <72 hours): No imaging 1
3. Initiate oral steroids immediately (prednisolone 50-60 mg daily for 5 days, then 5-day taper) 2, 3
4. Implement eye protection (lubricating drops every 1-2 hours, ointment at night, taping if needed) 2
5. Arrange follow-up at 3 months or sooner if worsening 2

The evidence is clear and consistent: routine CT/CTA imaging for suspected Bell's palsy in the ED is not indicated, wastes resources, exposes patients to unnecessary radiation, and does not change acute management. 1