The anatomy is quite complex but as for functionality, facial nerve is involved in the movements of muscles related to facial expression and laryngeal muscles. While testing, the patients are asked to give facial expressions. Cranial nerve VIII is a sensory nerve is responsible for hearing and senses of equilibrium. Although this more relates to speech and hearing but the testing is not the task of a speech pathologist but rather a neurologist or audiologist. If such problems arise, the patient should be referred to an ENT or audiologist.
To test cranial nerve IX, the gag reflex involves a brisk and brief elevation of the soft palate and bilateral contraction of pharyngeal muscles evoked by touching the posterior pharyngeal wall. It is tested on the left and the right sides and the reflex response should be consensual (i.e., the elevation of the soft palate should be symmetrical regardless of the side touched).
Unilateral nuclear or infranuclear involvement of the vagus causes ipsilateral paralysis of the soft palate, pharynx, and larynx. The voice is hoarse or nasal, the involved palatal arch is paralyzed, and liquids will enter the nasopharynx or trachea. The vocal cord on the involved side is