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Bell's palsy: Pathogenesis, clinical features, and diagnosis in adults

Michael Ronthal, MD
Section Editor
Jeremy M Shefner, MD, PhD
Deputy Editor
John F Dashe, MD, PhD


Sir Charles Bell first described the anatomy and function of the facial nerve in the early 1800s [1,2]. Bell's initial description of facial palsy related to facial paralysis caused by trauma to the peripheral branches of the facial nerve.

Bell's palsy is the appellation commonly used to describe an acute peripheral facial palsy of unknown cause. However, the terms "Bell's palsy" and "idiopathic facial paralysis" may no longer be considered synonymous. A peripheral facial palsy is a clinical syndrome of many causes, as discussed below, and evaluation requires more than a superficial examination.

This review will discuss the pathogenesis, clinical features, and diagnosis of Bell's palsy. The prognosis and treatment of Bell's palsy is discussed elsewhere. (See "Bell's palsy: Treatment and prognosis in adults".)


The facial nerve is a mixed nerve, containing the following (figure 1):

Motor fibers that innervate the facial muscles

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Literature review current through: Nov 2017. | This topic last updated: Dec 01, 2016.
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