Bell's palsy is a form of temporary facial paralysis resulting from damage or trauma to a facial nerve. Generally, the condition affects only one of the two facial nerves and one side of the face; however, in rare cases, it can affect both sides.
Bell's palsy is named for Sir Charles Bell, a nineteenth-century Scottish surgeon who was the first to describe the condition. Bell's palsy, which is not related to stroke
, is the most common cause of facial paralysis.
Understanding the Facial Nerves
The facial nerve (also called the seventh cranial nerve) is a paired structure that travels through a narrow, bony canal (called the fallopian canal) in the skull, beneath the ear, to the muscles on each side of the face. For most of its journey, the nerve is encased in this bony shell.
Each facial nerve directs the muscles on one side of the face, including those that control eye blinking and closing, and facial expressions such as smiling and frowning. The facial nerve also carries nerve impulses to the:
- Lacrimal (tear) glands
- Saliva glands
- Muscles of a small bone in the middle of the ear, called the stapes.
The facial nerve also transmits taste sensations from the tongue.
When Bell's palsy occurs, the function of the facial nerve is disrupted, causing an interruption in the messages the brain sends to the facial muscles. This interruption results in facial weakness or paralysis.