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Cranial Nerve Anatomy
Dr. Peterson
Cranial Nerve I: Olfactory Nerve
• The axons of these cells extend through the
cribriform plate of the ethmoid bone into the
olfactory bulb at the anterior end of the olfactory
nerve.
anosmia – lack of smell
Cranial Nerve II: Optic Nerve
Raised disc of the retina at the point of entry of the
optic nerve is called the optic disc.
• The optic nerve carries visual information from the
retina (cells sensitive to light) through the optic
chiasm to the lateral geniculate nucleus of the
thalamus and then to the extrageniculate
pathways, including the visual cortex in the
occipital lobe.
papilledema – optic disc swelling
Cranial Nerve III, IV, VI: Oculomotor,
Trochlear & Abducens Nerves
Brain Anatomy
CN3
CN4
• The oculomotor (III) and trochlear (IV) nerves are
located in the midbrain. The abducens nerves are
located in the pons. All are responsible for
extraocular eye movements. CN III is also
responsible for pupillary constriction.
strabismus – eye deviation
CN6
Cranial Nerve V: Trigeminal Nerve
• The trigeminal nerve (CN V) exits the brainstem
at the ventrolateral pons and the 3 divisions exit
foramen in the skull. CN V provides sensation to
the face.
Trigeminal neuralgia – severe nerve pain
(neuralgia) involving 1 of 3 branches
Cranial Nerve VII: Facial Nerve
• The facial nerve (CN VII) exits the brain at the
pontomedullary junction in a region called the
cerebellopontine angle to the internal auditory
meatus to the facial canal in the temporal bone.
CN VII is primarily responsible for the muscles of
facial expression, taste and dampening sounds.
Bell’s palsy – unilateral facial weakness
(CN VII palsy)
Cranial Nerve VIII:
Vestibulocochlear Nerve
• The vestibulocochlear nerve (CN VIII) exits the
brainstem at the pontomedullary and travels
with facial nerve until it travels in the auditory
canal to reach the cochlea spiral-shaped cavity of
the inner ear and the main organ of hearing) and
vestibular organs (utricle, saccule, and the three
semicircular ducts of the membranous labyrinth
of the inner ear).
Vertigo – spinning sensation
Presbyacusis – age-related
hearing loss
Cranial Nerve IX & X: Glossopharyngeal
and Vagus Nerves
Dysarthria – difficulty with speech
• The glossopharyngeal (IX) exits the brainstem out from
the sides of the upper medulla, just rostral (closer to
the nose) to the vagus nerve (X). CN X is passes
through the neck & thorax to the abdomen. CN IX is
responsible for swallowing, taste & sensation to the
pharynx. CN X is responsible for HR, peristalsis,
sweating, speech, etc.!
Cranial Nerve XI: Spinal Accessory
Nerve
Spinal accessory nerve syndrome –
weakness/atrophy of upper trap & SCM
• Fibers of the spinal accessory nerve (CN XI)
originate in the upper spinal cord, form rootlets,
roots, and then the nerve itself. CN XI exits the
foramen magnum and supplies the upper
trapezius (shoulder elevation) and SCM (neck
rotation)
Cranial Nerve XII: Hypoglossal
Nerve
• The hypoglossal nerve (CN XII) exits the brain
at the medulla oblongata. CN XII is
responsible for tongue manipulation
responsible for speech, food manipulation
and swallowing.
Image Credits
• http://www.med.umich.edu/lrc/coursepages/m1/anatomy2010/html/modules/CN_module/Files
/cn1_a.jpg
• https://classconnection.s3.amazonaws.com/720/flashcards/1137720/jpg/8481354687740630.jpg
• https://12cranialnerves.files.wordpress.com/2012/04/optic_pathway-3.gif
• http://www.ophthobook.com/wp-content/uploads/2007/12/no-brainstem.jpg
• http://www.aafp.org/afp/2000/0115/afp20000115p427-f3.jpg
• http://upload.wikimedia.org/wikipedia/commons/3/36/Gray768.png
• http://becuo.com/vestibulocochlear-nerve
• http://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Brain_human_normal_inferior_vi
ew_with_labels_en-2.svg/250px-Brain_human_normal_inferior_view_with_labels_en-2.svg.png
• http://img.tfd.com/MosbyMD/thumb/accessory_nerve.jpg
• http://www.edoctoronline.com/media/19/photos_70e525d5-413a-4d15-9a87-62954e148e9a.jpg