Neurology · Cranial Nerve Disorders
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Bell palsy is an idiopathic, unilateral facial nerve (CN VII) palsy characterized by the sudden onset of ipsilateral facial muscle weakness involving both the upper and lower face.
The hallmark clinical finding is the inability to wrinkle the forehead or raise the eyebrow, which distinguishes a peripheral CN VII lesion from a central lesion like a stroke.
Patients frequently present with postauricular pain, hyperacusis due to paralysis of the stapedius muscle, and decreased lacrimation or taste disturbance.
The most common etiology is a reactivation of herpes simplex virus (HSV) leading to inflammation and edema of the facial nerve within the facial canal.
The first-line treatment is a short course of oral corticosteroids (e.g., prednisone) initiated within 72 hours of symptom onset to improve the likelihood of complete recovery.
Antiviral therapy (e.g., valacyclovir) may be added to corticosteroids in cases of severe facial paralysis, though it is not considered monotherapy.
Eye care is critical to prevent corneal abrasion or ulceration, requiring the use of artificial tears during the day and lubricating ointment with eye taping at night.
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A 34-year-old male presents to the urgent care clinic complaining of the sudden onset of right-sided facial drooping that began this morning. He reports a dull ache behind his right ear that started yesterday. On physical examination, he has complete right-sided facial paralysis, including the inability to close the right eye and the inability to wrinkle the right forehead. The remainder of the neurological examination is unremarkable, and he has no other focal deficits. He has no history of recent trauma or tick bites.
What is the most appropriate initial management for this patient?
Oral prednisone
The patient presents with classic signs of Bell palsy (peripheral CN VII palsy). The most effective initial treatment to improve outcomes is early administration of oral corticosteroids.
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Etiology / Epidemiology
Idiopathic unilateral facial nerve (CN VII) palsy; often associated with HSV reactivation.
Clinical Manifestations
Sudden onset ipsilateral facial paralysis involving the forehead; Bell phenomenon.
Diagnosis
A clinical diagnosis of exclusion; no specific lab or imaging required.
Treatment
Prednisone (within 72 hours) is the gold standard; add Valacyclovir for severe cases.
Prognosis
Most recover fully; 85% show improvement within 3 weeks.
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Epidemiology & Etiology
Most common cause of facial paralysis, peaking in the 4th decade. Strongly linked to herpes simplex virus reactivation within the geniculate ganglion. Diabetes mellitus and pregnancy (3rd trimester) are significant risk factors.
Pertinent Anatomy
The facial nerve exits the cranium via the stylomastoid foramen. It traverses the parotid gland and provides motor innervation to the muscles of facial expression. Lesions proximal to the geniculate ganglion may cause hyperacusis or loss of taste.
Pathophysiology
Inflammation and edema of the facial nerve within the narrow bony facial canal lead to nerve compression and ischemia. This results in a lower motor neuron (LMN) lesion. The process is typically self-limiting but requires early intervention to prevent permanent axonal degeneration.
Clinical Manifestations
Presents as acute, unilateral facial weakness including the forehead. Patients exhibit Bell phenomenon (upward eye deviation upon attempted closure) and inability to wrinkle the forehead. Red flags include bilateral involvement, gradual onset, or associated limb weakness, which suggest Lyme disease, Guillain-Barré syndrome, or stroke.
Diagnosis
Diagnosis is clinical after excluding other causes. No gold standard test exists for the condition itself. If the presentation is atypical, MRI of the brain is indicated to rule out cerebellopontine angle tumors or stroke.
Treatment
Initiate Prednisone (60-80 mg/day) within 72 hours of symptom onset to reduce nerve edema. Add Valacyclovir for patients with severe paralysis. Do not use antivirals as monotherapy. Eye protection with artificial tears and nighttime patching is mandatory to prevent corneal abrasion.
Prognosis
Prognosis is excellent, with 85% of patients showing clinical improvement within 3 weeks. Incomplete paralysis at presentation is a positive prognostic indicator. Electromyography (EMG) may be used in refractory cases to assess for denervation.
Differential Diagnosis
Stroke: forehead is spared due to bilateral cortical innervation
Lyme disease: often bilateral and associated with erythema migrans
Herpes Zoster Oticus: Ramsay Hunt syndrome with vesicles in the ear canal
Parotid tumor: gradual onset with palpable mass
Guillain-Barré syndrome: bilateral weakness with ascending paralysis