|Classification and external resources|
A person attempting to show his teeth and raise his eyebrows with Bell's palsy on his right side (left side of the image).
Bell's palsy is a paralysis of the face on one side. It is caused because cranial nerve VII (the facial nerve) stops conducting to the facial muscles. The sufferer cannot move facial muscles on the affected side.
Several conditions can cause facial paralysis, e.g., brain tumor, stroke, and Lyme disease. Bell's palsy is named after Scottish anatomist Charles Bell, who first described it. It is the most common acute disease involving only one nerve, and is the most common cause of sudden facial nerve paralysis.
Bell's palsy usually cures itself, sometimes in a few weeks. The hallmark of this condition is a rapid start of partial or complete paralysis that often occurs overnight. It is thought that an inflammation leads to swelling of the facial nerve. The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to stop the nerve from working. At times of lowered immunity, a dormant (sleeping) virus, usually the chicken pox or cold sore virus, can wake up and attack the nerve causing it to swell.
Corticosteroids (cortisone steroids) have been found to improve the condition while anti-viral drugs have not. Early treatment is necessary for steroids to be effective. Most people recover spontaneously and achieve near-normal to normal functions. Many show signs of improvement as early as 10 days after the onset, even without treatment.
Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea may be permanently damaged resulting in impaired vision. The eye may need to be taped shut at night.
- Sudworth, John 2012. Bell's palsy: Facing the TV cameras with half a smile. BBC News. 
- Sullivan F.M. et al 2007. "Early treatment with prednisolone or acyclovir in Bell's palsy". N. Engl. J. Med. 357 (16): 1598–607. doi:10.1056/NEJMoa072006. PMID 17942873. http://content.nejm.org/cgi/pmidlookup?view=short&pmid=17942873&promo=ONFLNS19.