The muscles affected by Bell's palsy:
1. Frontalis
> Action: lift the eyebrows; wrinkle the forehead
2. Orbicularis oculi
> Action: closes the eyelids (voluntarily and involuntarily); cause tears to flow out into the eyes
3. Orbicularis oris
> Action: purse, pucker, and close the lips
4. Buccinator
> Action: maintains the tightness of the cheeks and compresses them into the teeth for chewing
5. Platysma
> Action: depresses the mandible and lower lip; tenses the skin of the anterior neck
Mechanism of muscle weakness:
Bell's palsy is a facial paralysis which is caused by dysfunction of cranial nerve VII (facial nerve). Although the exact cause of Bell's palsy is unknown, it has been proposed that the illness is brought on by inflammation that is directed by the body's immune system against the nerve controlling movement of the face. The facial nerve travels via a confined channel in the temporal bone; enlargement of the nerve may cause compression and subsequent damage. Along with one-sided facial paralysis, the patient may also experience dry mouth and eyes, taste disturbances, and hyperacusis.
Other symptoms:
- inability to close the eye on the affected side of the face
- disordered movement of the muscles that control facial expressions, such as smiling, squinting, or blinking
- loss of feeling in the face
- drooling and tearing