The vestibulocochlear nerve is the eighth nerve of the twelve cranial nerves, which are all located in the brain's cranium. It has two main jobs: transmitting sound and transmitting information about the body's place in space. Both of these functions are based in the ear, and each of these functions is performed by a different section of the nerve - the cochlear nerve section and the vestibular nerve section. The cochlear nerve is the section that assists in hearing, and the vestibular nerve assists in maintaining and identifying equilibrium.
The fibers of the cochlear section of the nerve end in the organ of Corti, the part of the ear that contains hair-like auditory sensory cells. It then passes on the information from these cells to the brain. The fibers of the vestibular section of the nerve end in the structures of the inner ear that sense equilibrium, such as the utricle and the saccule. The fluid in this area of the ear can sense where the head of the person is in relation to the gravitational pull.
Damage to the vestibulocochlear nerve may lead to symptoms such as ringing in the ears (tinnitus), dizziness, vertigo, deafness, or vomiting. To test this cranial nerve, you will need to perform at least two tests, one for each function that the nerve is responsible for. Simply making a sudden sound and watching to see whether the person responds can detect bilateral hearing loss, and special hearing tests called BEAR (brain stem evoked auditory response can detect issues with the nerve related to a single ear. To test the vestibular (balance-related) function of the nerve, you can tilt the patient's head backwards and turn it side to side as well as up and down. This should prompt the patient's eyes to travel in the same direction as the head, unless there is damage of the vestibulocochlear nerve.