Facial Nerve

Anatomy and Course

• The facial nerve (Cranial Nerve VII) is a mixed nerve that controls the muscles of facial expression and conveys taste sensations from the anterior two-thirds of the tongue.
• It originates in the pons and exits the brainstem at the cerebellopontine angle.
• The nerve then enters the internal auditory canal, runs through the facial canal in the temporal bone, and exits the skull via the stylomastoid foramen.
• Within the temporal bone, the facial nerve gives off the greater petrosal nerve, nerve to stapedius, and chorda tympani.

Nuclei of the Facial Nerve

Motor Nucleus:

• Located in the pons.
• Controls muscles of facial expression.

Superior Salivatory Nucleus:

• Provides parasympathetic innervation to the lacrimal, nasal, and palatine glands.

Nucleus of the Solitary Tract:

• Receives taste sensations from the anterior two-thirds of the tongue.

Spinal Trigeminal Nucleus:

• Processes pain and temperature sensations from the ear.

Clinical grading of facial nerve function (House and Brackmann)

Grade	Function Description	Clinical Sx
1	normal facial function in all areas
2	mild dysfunction	gross: slight weakness noticeable on close inspection; may have very slight synkinesis at rest: normal symmetry and tone motion: forehead: slight to moderate movement eye: complete closure with effort mouth: slight asymmetry
3	moderate dysfunction	gross: obvious but not disfiguring asymmetry; noticeable but not severe synkinesis motion: forehead: slight to moderate movement eye: complete closure with effort mouth: slightly weak with maximal effort
4	moderate to severe dysfunction	gross: obvious weakness and/or disfiguring asymmetry motion: forehead: none eye: incomplete closure mouth: asymmetry with maximum effort
5	severe dysfunction	gross: only barely perceptible motion at rest: asymmetry motion: forehead: none eye: incomplete closure
6	total paralysis no movement