Anatomy & Function of the Facial Nerve

• The facial nerve (CNVII) has two major divisions and controls the muscles of facial expression, including the frontalis muscle (raises the eyebrows), the orbicularis oculi muscle (closes the eyes), the zygomaticus muscles (raises the angle of the mouth)
  • The upper zygomatic branch supplies the frontalis, upper lid orbicularis oculi, corregator supercilli and procerus.
• The lower zyqomatic branch supplies the lower lid orbicularis.
• The nervus intermedius gives off the greater petrosal nerve which carries parasympathetic secretary fibers to the lacrimal gland

Etiologies

• Paresis of the orbicularis oculi muscle leads to a diminished blink, incomplete eyelid closure ( Lagophthalmos ), impairment of the nasolacrimal pumping system
  • The blink reflex and lid position are critical to maintain the ocular surface 
  • Each blink spreads the tear film over the ocular surface and allows for a continuous layer of moisture.

• Congenital
  • Moebius' Syndrome
• Acquired
  • Bell's Palsy
  • vascular lesions
• Tumors
  • Acoustic Neuroma
  • Parotid gland
  • temporal bone tumor
• Trauma

Symptoms

• Tearing, atonic eyelid

Terms

Lagophthalmos : Patients with lagophthalmos have an inability to close eyelids. This may occur, for instance, in patients with Thyroid eye disease. Visit the lagophthalmos page for more details.