Bell's palsy is sudden but temporary paralysis of one side of your face (or rarely, both sides). If you have Bell's palsy, your face might feel weak, or it might twitch; one side of your mouth might droop and you might be unable to close your eye. The symptoms are caused by a disorder in one of the nerves that controls your facial muscles. According to the National Institute of Neurological Disorders and Stroke, most scientists believe that the nerve malfunction is caused by infection with viral meningitis or the herpes simplex (cold sore) virus.
Nerve Function
The seventh cranial nerve is one of two nerves that control the muscles of your face. As it passes out of your skull, it travels through a narrow opening called the internal acoustic meatus in your temporal bone (your temple). If the nerve is compressed at that narrow point, it can cause paralysis. Although the exact cause of Bell's palsy is not known for certain, it has been associated with certain viral infections.
Meningitis
Infection with viral meningitis is associated with the development of Bell's palsy. The theory is that the seventh cranial nerve becomes inflamed and swollen in response to infection with the virus. If the inflammation is severe, the nerve might be compressed, causing paralysis. When the infection is successfully fought off or the inflammation stops, so does the nerve compression. That is why the paralysis is temporary.
Herpes and Other Causes
The herpes simplex virus, which causes cold sores and genital herpes, is commonly found in people afflicted with Bell's palsy. Other viruses such as herpes zoster, which causes chicken pox and shingles, and Epstein-Barr virus, which causes mononucleosis, have also been associated with Bell's palsy.
Any condition that runs down your immune system, such as an upper respiratory infection like the common cold or the flu, or conditions that tax your metabolism, such as pregnancy or diabetes, increase your risk for Bell's palsy.
Treatment
Most people with Bell's palsy will recover fully in time, even without treatment, but current treatments reflect the belief that viral inflammation of the seventh cranial nerve causes the compression and resulting paralysis. Your doctor might prescribe a corticosteroid like prednisone to combat the inflammation and swelling of the nerve, along with an antiviral medication such as acyclovir or valacyclovir if he suspects that you have a viral infection. According to the Mayo Clinic, evidence from clinical trials shows that treatment with steroids tends to be more successful than treatment with antivirals.
