N3 Anatomy and Physiology (1st Sem AY 2022-2023)

Bell's palsy condition occurs when a lateral side of the face causes sudden muscle weakness. For patients diagnosed with Bell’s palsy, here are some of the facial muscles that are affected:

1. Orbicularis Oculi muscle
   Action: closes the eye

2. Frontalis or Frontal Belly muscle
   Action: Draws scalp anteriorly, raises eyebrows, and wrinkles the skin of the forehead horizontally

3. Buccinator muscle
   Action: Presses cheeks against the teeth and lips, draw the corner of the mouth laterally, and assist in chewing or mastication

4. Orbicularis Oris muscle
   Action: Closes and protrudes lips, compresses lips against teeth and shapes lips during talking

5. Zygomaticus Major muscle 
   Action: Draws angle of mouth superiorly and laterally

Bell’s palsy happens when a disorder in the facial nerve causes muscle weakness or paralysis. It transpires due to spasticity, which is the increased muscle tone or stiffness that increases tendon reflexes and pathological reflexes. Other symptoms of facial muscle weakness may include:

• Disordered movement of facial muscles;

• Unable to feel the face, going to paralysis;

• Tearing and unable to close eyes on the affected lateral side of the face;

• Drooling and loss of sense of taste;

• Hypersensitivity on the affected side of the ear; and

• Headache.