Muscles affected by Bell's palsy:
- Orbicularis oculi - closes eye
- Orbicularis oris - closes and protrudes lips
- Occipitofrontalis - draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally
- Buccinator - presses cheeks against teeth and lips; draws corner of mouth laterally
- Platysma - draws outer part of lower lip inferiorly and posteriorly; depresses mandible
Mechanism of muscle weakness:
When there is disease or damage to the facial (VII) nerve, it causes Bell's palsy. Some possible causes include inflammation due to ear infections, surgical errors, or infection of the herpes simplex virus.
Other symptoms:
Unable to close the eye on the affected side, unable to wrinkle the forehead, drooling, and being unable to swallow. Other symptoms are similar to the onset of stroke.