Affected muscles and their actions:
1. Frontalis - raises the eyebrows and gives wrinkles to the forehead horizontally
2. Orbicularis oculi - pulls the skin of the forehead and cheek towards the nose and closes the eyes
3. Orbicularis oris - produce movements of the lips
4. Buccinator - compress the cheek against the molar teeth and prevent them from getting bitten during mastication
5. Platysma - lowering the corners of the mouth and lower lip, depressing the mandible, and opening the mouth
Mechanism of muscle weakness
Bell's palsy is believed to occur when the seventh cranial nerve gets compressed at the geniculate ganglion. The first part of the facial canal, called the labyrinthine segment, is the narrowest, and this is where most compression occurs. Inflammation in the canal causes pressure on the nerve and reduces blood flow.
Other symptoms:
- Disordered movement of the muscles that control facial expressions
- Headache
- Tearing
- Drooling
- Loss of the sense of taste
- Hypersensitivity to sound in the affected ear
- Inability to close the eye on the affected side of the face