Definition of Ramsay Hunt syndrome:

Ramsay Hunt syndrome is a disorder of the brain and nervous system (neurologic disorder) that occurs when a virus (varicella zoster) infects certain nerves in the head.

Causes, incidence, and risk factors:

The varicella zoster virus causes both Ramsay Hunt syndrome and another common cause of facial weakness, Bell's palsy (in which there is no rash).

This virus is part of the family of human herpes viruses, which cause fever sores on the mouth and genital herpes. The varicella zoster virus also causes shingles and chickenpox.

In people with Ramsay Hunt syndrome, the virus is believed to infect the facial nerve near the inner ear. This leads to irritation and swelling.