The document summarizes the anatomy and pathophysiology of Bell's palsy, which is a sudden, unilateral facial paralysis of unknown cause. It describes the facial nerve's course from the brainstem nuclei through the facial canal. Bell's palsy is most common in ages 15-45 and of slightly higher incidence in Japanese individuals. The main cause is believed to be reactivation of latent herpes viruses in the facial nerve ganglia. Patients experience rapid onset of maximal facial weakness within two days and associated symptoms of tearing and taste abnormalities. Physical exam reveals impairment of facial muscle movement on one side. Management focuses on eye care to protect the cornea from drying due to impaired lid closure and tearing.
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