How is the Facial Nerve Injured?
The nerve can be injured anywhere along the path from its origin to its destination at the muscles of facial expression.
Some examples:
- Stroke (injury to the motor neurons in the seventh nerve nucleus in the brain)
- Trauma (injury to the nerve anywhere along its path, usually with the bony canal in the skull which it passes through, the fallopian canal)
- Benign tumors (acoustic or facial neuromas can gradually compress the nerve, as can benign tumors of the parotid gland)
- Cancerous tumors (tumors of the parotid gland or upper neck/face)
- Surgery for removal of tumors (above) or surgery of the middle or inner ear
- Congenital facial paralysis (Möbius syndrome, congenital unilateral lower lip palsy, others)
- Unknown (or idiopathic; this is the classic 'Bell's Palsy', in which case the nerve simply stops working without any of the above causes. Various theories exist for cause, but the end result is most likely inflammation and swelling of the nerve within the fallopian canal, resulting in decreased blood supply and thus injury to the nerve)