The Facial Nerve and Facial Paralysis
The facial nerve is one of the large nerves arising from the base of the brain that exits the skull base in front of the ear. It is one of the nerves that control special functions such as seeing, hearing, smell and swallowing and controls the muscles that supply movement to the face. The facial nerve also carries nerve fibers that are responsible for taste for the front 2/3 of the tongue, as well tearing from the eye.
Facial paralysis is the loss of function of the 7th cranial nerve that results in total or partial loss of the movement of the muscles of the face. Decreased taste and problems with tearing can also occur with facial paralysis.
Effects of facial paralysis
Facial paralysis can lead to less intelligible speech, drooling and difficulty eating, incomplete closure of the eye with exposure of the cornea and cosmetic deformity. For instance, with a facial paralysis, one side of the face does not move when smiling, much like you see with a victim of a stroke.
Causes of facial paralysis
- Bell’s palsy (cause of paralysis not known, named after Dr. Bell who first described it)
- Herpes infection (viral infection with the virus causing cold sores)
- Ear Infection
There is a grading system that assists the physician in categorizing the extent of the nerve deficit.
I - Normal Movement.
II - Mild Dysfunction: Gross slight weakness, normal tone of the muscles, asymmetry (difference in function between the two sides of the face) limited to mouth.
III - Moderate Dysfunction: Obvious but not disfiguring asymmetry, weak forehead, asymmetric mouth, eye closure with effort.
IV - Moderately Severe Dysfunction: Obvious weakness and/or disfiguring asymmetry. Good tone at rest. No forehead movement, incomplete eye closure, asymmetric mouth.
V - Severe Dysfunction: Only barely perceptible movement, rest asymmetry. Mouth and eye only slight movement without eye closure.
VI - Total Paralysis: No movement, gross asymmetry.