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Emergency and Acute Medicine – Bell’s Palsy
Overview And Clinical Definition
Bell’s palsy is an acute, idiopathic peripheral seventh cranial nerve (facial nerve) palsy. It is the most common cause of facial nerve paralysis in both adults and children. Spontaneous recovery occurs in approximately 85% of patients without treatment. Prognosis correlates with severity, with partial lesions recovering more reliably than complete paralysis. Clinical improvement usually begins within two weeks, often with return of taste sensation first, and recovery is typically complete within two to three months. Advanced age and delayed recovery are associated with worse outcomes. Men and women are affected equally, most commonly between the third and fifth decades, though all ages may be affected. Diabetes and pregnancy increase risk, and annual incidence ranges from 15 to 40 per 100,000.
Etiology And Pathophysiology
By definition, Bell’s palsy is idiopathic, though viral reactivation—most notably herpes simplex virus—is strongly suspected. Other infectious causes of peripheral facial nerve palsy include Lyme disease, Epstein–Barr virus, and varicella-zoster virus. The underlying mechanism is thought to be edema and degeneration of the facial nerve within the stylomastoid foramen. Because the forehead receives bilateral cortical innervation, only peripheral or brainstem lesions produce unilateral forehead weakness; isolated cortical lesions spare forehead movement.
Clinical Presentation
Patients typically report sudden onset unilateral facial droop with incomplete eyelid closure and loss of forehead muscle tone. Maximal weakness is reached within five days in nearly all cases, and within two days in about half. Associated features include excessive tearing or eye dryness, reduced blinking, subjective facial numbness, drooling, altered taste, hyperacusis, mastoid fullness or pain, and a frequent viral prodrome. On examination, there is isolated unilateral facial weakness involving both upper and lower face. Loss of forehead movement confirms a peripheral lesion. The remainder of the neurologic examination, including other cranial nerves and limb motor function, should be normal. The Bell phenomenon, upward rolling of the eye during attempted eyelid closure, may be observed.
Diagnostic Evaluation
Diagnosis is clinical and based on history and physical examination. Routine laboratory testing and imaging are not required. Lyme serology should be obtained in endemic regions or when clinical suspicion exists. Testing for infectious mononucleosis may be appropriate when EBV is suspected. Imaging is reserved for atypical cases or when alternative diagnoses such as tumor, mastoiditis, or central nervous system pathology are suspected.
Differential Diagnosis
Important alternatives include brainstem lesions, which typically involve additional cranial nerves or extraocular movement abnormalities; Lyme disease; Ramsay Hunt syndrome, suggested by vesicular rash, tinnitus, or vertigo; infectious mononucleosis; parotid or acoustic tumors; trauma; postoperative or infectious middle ear pathology; meningitis; Guillain–Barré syndrome; basilar artery aneurysm; early HIV infection; and bilateral facial palsy due to systemic disease such as sarcoidosis or leukemia. Rare recurrence of idiopathic palsy can occur without change in management.
Emergency Management
Patients with isolated peripheral facial nerve palsy are hemodynamically stable. Primary ED management focuses on eye protection to prevent corneal injury due to impaired eyelid closure. Lubricating ophthalmic preparations are essential, with eye patching at night as needed. Oral corticosteroids started within one week of symptom onset, ideally within 72 hours, improve recovery rates with minimal risk. Antiviral therapy combined with steroids may offer additional benefit in severe cases, though evidence is mixed. When Lyme disease is suspected, appropriate antibiotic therapy should be initiated. Surgical decompression is rarely considered and remains controversial, reserved for severe cases without improvement.
Medications
First-line therapy includes artificial tears or lubricating ophthalmic ointment as needed and prednisone 30–40 mg orally twice daily for seven days, with pediatric dosing adjusted by weight. In more severe presentations, valacyclovir 1 g orally three times daily for seven days may be added.
Disposition And Follow-Up
Hospital admission is not required for isolated Bell’s palsy. Patients may be safely discharged with outpatient management. Follow-up within one week is recommended to assess recovery and ensure adequate eye protection.
Key Clinical Lessons And Common Errors
Isolated seventh nerve weakness must involve both upper and lower face to support Bell’s palsy. Preservation of forehead movement indicates a central lesion and mandates further evaluation. A normal neurologic examination elsewhere is essential for diagnosis. Eye protection is critical to prevent corneal injury. Corticosteroids improve outcomes when given early, while antivirals remain optional and situation dependent.
Overview And Clinical Definition
Bell’s palsy is an acute, idiopathic peripheral seventh cranial nerve (facial nerve) palsy. It is the most common cause of facial nerve paralysis in both adults and children. Spontaneous recovery occurs in approximately 85% of patients without treatment. Prognosis correlates with severity, with partial lesions recovering more reliably than complete paralysis. Clinical improvement usually begins within two weeks, often with return of taste sensation first, and recovery is typically complete within two to three months. Advanced age and delayed recovery are associated with worse outcomes. Men and women are affected equally, most commonly between the third and fifth decades, though all ages may be affected. Diabetes and pregnancy increase risk, and annual incidence ranges from 15 to 40 per 100,000.
Etiology And Pathophysiology
By definition, Bell’s palsy is idiopathic, though viral reactivation—most notably herpes simplex virus—is strongly suspected. Other infectious causes of peripheral facial nerve palsy include Lyme disease, Epstein–Barr virus, and varicella-zoster virus. The underlying mechanism is thought to be edema and degeneration of the facial nerve within the stylomastoid foramen. Because the forehead receives bilateral cortical innervation, only peripheral or brainstem lesions produce unilateral forehead weakness; isolated cortical lesions spare forehead movement.
Clinical Presentation
Patients typically report sudden onset unilateral facial droop with incomplete eyelid closure and loss of forehead muscle tone. Maximal weakness is reached within five days in nearly all cases, and within two days in about half. Associated features include excessive tearing or eye dryness, reduced blinking, subjective facial numbness, drooling, altered taste, hyperacusis, mastoid fullness or pain, and a frequent viral prodrome. On examination, there is isolated unilateral facial weakness involving both upper and lower face. Loss of forehead movement confirms a peripheral lesion. The remainder of the neurologic examination, including other cranial nerves and limb motor function, should be normal. The Bell phenomenon, upward rolling of the eye during attempted eyelid closure, may be observed.
Diagnostic Evaluation
Diagnosis is clinical and based on history and physical examination. Routine laboratory testing and imaging are not required. Lyme serology should be obtained in endemic regions or when clinical suspicion exists. Testing for infectious mononucleosis may be appropriate when EBV is suspected. Imaging is reserved for atypical cases or when alternative diagnoses such as tumor, mastoiditis, or central nervous system pathology are suspected.
Differential Diagnosis
Important alternatives include brainstem lesions, which typically involve additional cranial nerves or extraocular movement abnormalities; Lyme disease; Ramsay Hunt syndrome, suggested by vesicular rash, tinnitus, or vertigo; infectious mononucleosis; parotid or acoustic tumors; trauma; postoperative or infectious middle ear pathology; meningitis; Guillain–Barré syndrome; basilar artery aneurysm; early HIV infection; and bilateral facial palsy due to systemic disease such as sarcoidosis or leukemia. Rare recurrence of idiopathic palsy can occur without change in management.
Emergency Management
Patients with isolated peripheral facial nerve palsy are hemodynamically stable. Primary ED management focuses on eye protection to prevent corneal injury due to impaired eyelid closure. Lubricating ophthalmic preparations are essential, with eye patching at night as needed. Oral corticosteroids started within one week of symptom onset, ideally within 72 hours, improve recovery rates with minimal risk. Antiviral therapy combined with steroids may offer additional benefit in severe cases, though evidence is mixed. When Lyme disease is suspected, appropriate antibiotic therapy should be initiated. Surgical decompression is rarely considered and remains controversial, reserved for severe cases without improvement.
Medications
First-line therapy includes artificial tears or lubricating ophthalmic ointment as needed and prednisone 30–40 mg orally twice daily for seven days, with pediatric dosing adjusted by weight. In more severe presentations, valacyclovir 1 g orally three times daily for seven days may be added.
Disposition And Follow-Up
Hospital admission is not required for isolated Bell’s palsy. Patients may be safely discharged with outpatient management. Follow-up within one week is recommended to assess recovery and ensure adequate eye protection.
Key Clinical Lessons And Common Errors
Isolated seventh nerve weakness must involve both upper and lower face to support Bell’s palsy. Preservation of forehead movement indicates a central lesion and mandates further evaluation. A normal neurologic examination elsewhere is essential for diagnosis. Eye protection is critical to prevent corneal injury. Corticosteroids improve outcomes when given early, while antivirals remain optional and situation dependent.
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