Lesion: Vestibular-If only the vestibular branch is damaged it would result in loss of balance and dizziness (vertigo). Major Function: Sensory - Vestibular branch senses balance. This nerve is composed of fibers from two branches: the vestibular nerve and the cochlear nerve, each with specific functions Decreased salivation and lacrimation (tearing) Cranial Nerve 8 (CN VIII): Vestibulocochlear Decreased ability to taste (particularly on the anterior 2/3 of the tongue). Lesion: Facial paralysis often called Facial or Bell's palsy. Major Function: Sensory - Taste from the anterior 2/3 of the tongue and Motor - Somatic Motor to the muscles of facial expressionĪNS Innervation: Parasympathetic to salivary glands and lacrimal glands Lesion: Medial deviation of the eye causing double vision Cranial Nerve 7 (CN VII): Facial Major Function: Somatic Motor to lateral rectus eye muscle Also, muscle weakness of the muscles of mastication Cranial Nerve 6 (CN VI): Abducens ![]() Lesion: Loss of sensation in face and forehead or increased sensitivity to pain known as Trigeminal neuralgia. Motor: Somatic Motor to muscles of mastication (chewing muscles) Major Function: Sensory - General sense from the face and forehead (including sensation of much of the mouth and anterior 2/3 of the tongue) Lesion: Eye deviation causing double vision Cranial Nerve 5 (CN V): Trigeminal Major Function: Somatic Motor to superior oblique eye muscle Lesion: Eye deviation causing double vision, pupil dilation and loss of pupillary light reflex Cranial Nerve 4 (CN IV): Trochlear Major Function: Somatic Motor to four of the six extrinsic muscles that move the eyeĪNS Innervation: Parasympathetic to sphincter pupillae muscle for constriction of the pupil Lesion: Blindness on affected side and loss of pupillary light reflex (Described Later) Cranial Nerve 3 (CN III): Oculomotor *Note: Loss of smell doesn't necessarily confirm a CN I lesion as an upper respiratory tract infection etc. Lesion: Loss of smell on the affected side Major Function: Sensory - Smell (olfaction) ![]() ![]() Because of the clinical importance of the cranial nerves we will discuss further the major functions of each one and some of the common symptoms observed when the nerves are damaged. The remaining cranial nerves carry some combination of sensory, somatic motor and parasympathetic information. In fact, three cranial nerves carry purely sensory information and four cranial nerves carry almost entirely somatic motor information. In contrast to the spinal nerves, however, not all cranial nerves carry both sensory and motor information. The motor information can also be subdivided into 1) somatic motor and 2) parasympathetic. We can subdivide the sensory information further into 1) special senses and 2) general senses. These nerves can carry both sensory and motor information, just as we have seen with spinal nerves. The names usually correspond to either the function or the structure of the nerve, hence, the Optic nerve is involved with vision and the Trigeminal nerve has 3 branches. The numbering starts with those most superior and anterior and progresses posteriorly and inferiorly. The cranial nerves are designated by Roman numerals (I - XII) and by names. ![]() There are twelve pairs of cranial nerves that originate in the brain and carry information to and from the brain. Doing an examination of the cranial nerves can provide valuable clinical information about the state and condition of the nervous system. When the doctor shined a light into her eyes to check her reflexes he was actually performing a small part of a cranial nerve examination. Remember the friend that you took to the emergency room after she got hurt sledding. You will also study the location and anatomy of these nerves in Bio 264 lab. CLICK HERE to load an image search of cranial nerves and check some of the thumbnails out to help you get an idea of where these nerves are at. There are lots of great pictures of cranial nerves in any internet search.
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