The facial nerve controls most of the muscles in the face and parts of the ear. The facial nerve goes through a narrow gap of bone from the brain to the face.
If the facial nerve is inflamed, it will press against the cheekbone or may pinch in the narrow gap. This can result in damage to the protective covering of the nerve.
If the protective covering of the nerve becomes damaged, the signals that travel from the brain to the muscles in the face may not be transmitted properly, leading to weakened or paralyzed facial muscles. This is Bell’s palsy.
The exact reason why this happens is unclear.
It may result when a virus, usually the herpes virus, inflames the nerve. This is the same virus that causes cold sores and genital herpes.
Other viruses that have been linked to Bell’s palsy include:
- chickenpox and shingles virus
- coldsores and genital herpes virus
- Epstein-Barr virus, or EBV, responsible for mononucleosis
- cytomegalovirus
- mumps virus
- influenza B
- hand-foot-and-mouth disease (coxsackievirus)