Sir Charles Bell first described the anatomy and function of the facial nerve in the 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 [3-5]. A peripheral facial palsy is a clinical syndrome of many causes, and evaluation requires more than a superficial examination.
This review will discuss the pathogenesis, clinical features, and diagnosis of Bell's palsy. Other causes of facial palsy are mentioned only as part of the differential diagnosis.
The prognosis and treatment of Bell's palsy is discussed elsewhere. (See "Bell's palsy: Prognosis and treatment in adults".)
ANATOMY OF THE FACIAL NERVE
The facial nerve is a mixed nerve, containing the following (figure 1):