For Patients & General Readers

Bell's Palsy is a sudden, temporary weakness or paralysis of the muscles on one side of your face. It can happen to anyone, but it's more common in pregnant women and people with diabetes. While usually not serious, it can affect your ability to smile, close your eye, and speak clearly.

Clinical Overview

Bell's Palsy is an idiopathic, acute peripheral facial nerve palsy, characterized by unilateral facial weakness affecting both the upper and lower face. The etiology is presumed to be viral reactivation or inflammatory processes impacting the facial nerve (CN VII) within its intra-osseous or extracranial course.

Clinical Presentation

Sudden onset of unilateral facial weakness or paralysis.
Involvement of both the forehead and lower facial muscles.
Absence of other neurological deficits.
Typically unilateral, but bilateral cases are rare.
Onset over hours to days, peaking within 72 hours.

Signs & Symptoms

Symptoms (Patient-Reported)

Drooping of one side of the face.
Difficulty closing the affected eye.
Inability to smile or frown symmetrically.
Numbness or tingling sensation on the affected side of the face.
Increased sensitivity to sound (hyperacusis) on the affected side.
Pain around the jaw or behind the ear on the affected side.
Changes in taste on the front of the tongue on the affected side.
Drooling from the affected side of the mouth.

Signs (Clinician-Observed)

Flattening of the nasolabial fold.
Inability to wrinkle the forehead on the affected side.
Inability to close the eye tightly on the affected side (lagophthalmos).
Facial asymmetry at rest and during voluntary movements (e.g., smiling, grimacing).

Differential Diagnoses

Condition	Distinguishing Feature
Ischemic Stroke	Stroke typically involves contralateral hemiparesis or hemisensory loss, and often spares the forehead due to bilateral cortical innervation.
Lyme Disease	May present with other systemic symptoms (rash, arthralgias, headache) and can cause bilateral facial nerve palsies.
Ramsay Hunt Syndrome (Herpes Zoster Oticus)	Characterized by a vesicular rash in the external auditory canal or on the auricle, often accompanied by severe ear pain and hearing loss.
Tumor of the Facial Nerve or Cerebellopontine Angle	Typically presents with a more gradual onset, progressive worsening, and may be associated with other cranial nerve deficits (e.g., hearing loss, vertigo, ataxia).
Otitis Media with Mastoiditis	Facial nerve involvement is usually secondary to inflammation and may be associated with otalgia, otorrhea, fever, and signs of mastoid inflammation.
Sarcoidosis	Can cause facial nerve palsy, often bilateral, and may be associated with other systemic manifestations of sarcoidosis (e.g., pulmonary infiltrates, erythema nodosum).

Red Flags — Seek Immediate Care

Bilateral facial weakness.
Associated neurological deficits (e.g., limb weakness, sensory loss, visual changes, ataxia).
Presence of a rash, particularly vesicular lesions.
Rapidly progressive or severe pain associated with facial weakness.

Key Investigations

Clinical diagnosis is typically sufficient.
Consider blood tests for Lyme disease serology if endemic area or suggestive symptoms.
Consider imaging (MRI brain with contrast) if atypical features, suspicion of stroke, tumor, or other central nervous system pathology.
Consider audiometry and electrodiagnostic studies (nerve conduction studies, EMG) in severe or persistent cases to assess prognosis and rule out other neuropathies.

Management Overview

Management of Bell's Palsy typically involves a short course of oral corticosteroids initiated within 72 hours of symptom onset to reduce inflammation. Antiviral therapy may be considered in cases suspected to be of viral etiology, particularly herpes simplex virus. Supportive care includes eye protection (lubricating eye drops, patching) to prevent corneal drying and injury.

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. TruelyserMD does not replace clinical judgement.