Affected muscles:
- Frontalis - helps to move the eyebrows up and wrinkle the forehead
- Orbicularis oculi - closes the eyelids and assists in pumping the tears from the eye into the nasolacrimal duct system
- Orbicularis oris - pursing or puckering of the lips
- Buccinator - maintains the tightness of the cheeks and presses them against the teeth during chewing.
- Platysma – depresses the mandible and lower lip and tenses the skin of the anterior neck
Bell’s palsy is caused by trauma to the seventh cranial nerve, also called the “facial nerve.” Symptoms often peak in severity in 72 hours. Weakness will be partial to complete to one-half of the face. Patients may present with an inability to close the affected eyelid or lip. Other symptoms include corneal exposure, lagophthalmos, brow droop, paralytic ectropion of the lower lid, upper eyelid retraction, decreased tear output, and loss of nasolabial fold.