Does Bell's palsy present with the classical features of peripheral facial palsy?

Bell's Palsy and Peripheral Facial Palsy Features

Yes, Bell's palsy presents with the classical features of peripheral facial nerve palsy, characterized by acute unilateral facial weakness or paralysis involving all facial muscles including the forehead, with onset in less than 72 hours and without an identifiable cause. 1

Clinical Presentation of Bell's Palsy

• Bell's palsy manifests as rapid onset unilateral facial weakness or complete paralysis affecting all branches of the facial nerve, including the forehead, which is a key distinguishing feature from central causes of facial weakness 2, 1
• The condition develops over 1-3 days with symptoms typically peaking within the first week 3
• Patients experience inability to close the eyelid (lagophthalmos), drooping of the corner of the mouth, and flattening of the nasolabial fold on the affected side 1, 4
• Associated symptoms include:
  • Ipsilateral pain around the ear or face 2
  • Taste disturbance or loss due to involvement of chorda tympani 2, 1
  • Hyperacusis due to stapedius muscle involvement 2
  • Dryness of the eye or mouth 2, 1

Distinguishing Features of Peripheral vs. Central Facial Palsy

• In peripheral facial palsy (including Bell's palsy), the entire hemiface is affected including the forehead, as the lesion is at the level of the facial nerve 1, 4
• In central facial palsy (as seen in stroke), forehead sparing is typically observed because of bilateral cortical innervation to the upper face 4, 5
• Bell's phenomenon (upward rolling of the eyeball when attempting to close the affected eye) is often present in Bell's palsy 1

Diagnostic Criteria

• Bell's palsy is diagnosed when there is:
  • Acute onset (<72 hours) of unilateral facial weakness or paralysis 2
  • No other identifiable cause for the facial weakness 2
  • Involvement of all facial muscles on the affected side, including the forehead 1, 4
• It is primarily a diagnosis of exclusion after ruling out other causes of facial paralysis 6

Common Pitfalls in Diagnosis

• Failing to recognize red flags that suggest alternative diagnoses:
  • Gradual onset over more than 72 hours 2, 6
  • Bilateral facial weakness (extremely rare in Bell's palsy) 2
  • Presence of other neurological deficits 4
  • Recurrent episodes of facial paralysis 2
• Misdiagnosing central facial weakness (as in stroke) as Bell's palsy 4, 5
• Not considering other causes such as Lyme disease, sarcoidosis, tumors, or zoster in atypical presentations 2

Severity Assessment

• The House-Brackmann facial nerve grading system (grades I-VI) is commonly used to assess severity and monitor recovery 2
• This scale ranges from normal function (grade I) to total paralysis (grade VI) 2
• The severity of initial paralysis is a significant prognostic factor for recovery 1

Bell's palsy is indeed characterized by the classic features of peripheral facial nerve palsy, with the important distinction that it is idiopathic and diagnosed only after excluding other potential causes of facial weakness.