CNs 1, 2, 8 - Solely Sensory Set
CNs 1, 2, 8 - solely sensory set
- These CNs are solely involved in sensory function.
functions
- CN 1, the olfactory nerve, is responsible for smell detection.
- CN 2, the optic nerve, is responsible for vision.
- CN 8, the vestibulocochlear nerve, is responsible for auditory and vestibular function.
CN entry into the brainstem
- Optic chiasm of CN 2 is the bundle of crossing fibers of the optic nerve as it transitions to optic tract.
- We see that if the pituitary enlarges, it can grow into and injure the optic chiasm.
- Clinical correlation - Pituitary tumor
- CN 8, the vestibulocochlear nerve enters at the pontomedullary junction.
- CN 1, the olfactory nerve lies superior to the brainstem.
Location in the Pons and medulla
- The vestibulocochlear nucleus of CN 8 lies postero-laterally and stretches from the pons into the medulla.
- CN 8 nerve enters laterally at the pontomedullary junction.
CN 1
Relevant Anatomy
Relevant anatomy surrounding the olfactory nerve (CN 1):
- The upper nasal cavity contains olfactory epithelium.
- The cribriform plate separates the cranial vault from the nasal cavity.
- Just above the cribriform plate the olfactory bulb transitions posteriorly to the olfactory tract.
- Within the olfactory epithelium lie the bipolar primary olfactory neurons, CN 1 extends through the cribriform plate to innervate the olfactory bulb. Note that this is the extent of cranial nerve 1, the olfactory nerve. The olfactory bulb and tract are telencephalic extensions of the cerebrum, itself.
CN 2
- An optic nerve projects from the back of each eyeball meet at the site of the pituitary body where select fibers cross in the optic chiasm.
- At that point they transition to optic tracts, which project to the back of the brain.
CN 8
- The vestibulocochlear nucleus (CN 8) spans from the upper pons to the mid-medulla. It's widest within the upper medulla but narrow at its vertical extremes.
- CN 8 passes through the internal acoustic foramen and enters the brainstem through the pontomedullary junction, laterally.