Cranial Nerves CN I-IV & VIII Flashcards
Where do olfactory nerves originate?
In olfactory mucosa of upper portion of nasal cavity
What is the only sense, special or general, that reaches cortex directly and not via thalamus?
Olfaction
Lesion to CN I?
Anosmia.
How to examine olfactory nerve?
Odorants applied to each nostril with eyes closed.
The retina itself is apart of what?
CNS
Where do optic nerves originate?
Ganglion cells of retina
Where does optic nerve synapse?
Lateral geniculate body.
How do we connect to CN III so that pupils constrict?
Fibers from optic tract also form superior brachium which sends light reflex info to superior colliculus
Where does olfactory nerve synapse?
In olfactory bulb after transversing cribiform plate of ethmoid bone.
Lesion to CN II?
Anopsia
Where does CN II exit skull?
Optic canal via sphenoid
Where does CN III originate?
Oculomotor nucleus (motor)
EWN (parasympathetic)
Where does CN III exit skull?
Interpedunculuar fossa.
Motor function of CN III?
Extraocular muscles
Parasympathetic function of CN III?
Pupillary constriction in response to light and accommodation for near vision (spinchter pupillae muscle) and thickening of lends during accommodation (ciliaris muscle)
If oculomotor nucelus is lesioned what happens?
Ptosis. Cannot hold eyelid open.
What happens if CN III is lesioned?
Diplopia, ptosis, lateral strabismus, mydriasis, cyclopegia
What exits skull via superior orbital fissure?
CN III oculomotor
Level of nuclei CN III?
Midbrain at level of superior colliculus, anterior portion of the periaqueductal gray
Level of CN IV?
Midbrain at level of inferior colliculus, in anterior portion of periaqueductal gray
Where does CN IV exit the skull?
Superior orbital fissure
How to examine CN IV ?
Downward and inward eye movements
Lesion to CN IV?
Diplopia when looking down and in and head tilt to the opposite side
CN IV function?
Extraocular movements of superior oblique muscle
Level of CN VI?
Lower pons at level of facial colliculus
Function of CN VI?
Extraocular movements of lateral rectus muscle
How to examine CN VI?
Lateral eye movements
Lesion to CN VI?
Diplopia, medial strabismus
Where does CN VI exit skull?
Superior orbital fissure
Where do CN IV nerves decussate before exiting inferior to inferior colliculi?
Superior medullary velum
Where does CN VIII originate?
Vestibular nuclei and cochlear nuclei
Level of CN VIII for vestibular nuclei?
Lateral aspect of 4th ventricle
Level of CN VIII for cochlear nuclei?
Acoustic tubercle
Where does CN VIII exit at?
Cerebellopontine angle
How to examine for CN VIII?
Caloric test and barony chair test for vestibular nuclei and Weber and rinne tests, audio gram for cochlear nuclei
Lesion to CN VIII?
Vertigo, nystagmus, dysequilibrium. Loss of hearing, tinnitus.
Name peripheral branches of CN V?
V1 opthalamic
V2 maxillary
V3 mandibular
Where does V1 opthalamic exit skull?
Via SOF
Where does V2 maxillary exit skull?
Foremen rotundum
V3 mandibular exits skull where?
Foremen ovale
Name the nuclei of CN V?
Nucelus of spinal tract of trigeminal (pain and temperature)
Chief sensory nucelus
Mesencephalic nucelus
Motor nucelus
Chief sensory nucelus does what?
Touch
Mesencephalic nucelus does what?
Proprioception
Motor nucelus does what?
Mastication muscles
What is the function of CN V?
Sensory to face, scalp, teeth, most of tongue, oral and nasal mucosa, dura mater, and cerebral blood vessels. Motor to muscles of mastication, the tensor tympani, and tensor veli palatini muscles, the mylohyoid and anterior belly of the diagastric muscles
Describe sensory fibers coming in from all three divisions of CN V?
Psuedounipolar cells whose bodies are in the trigeminal (semilunar ganglion) or Mesencephalic nucelus for proprio
Name muscles of mastication
Masseter, temporalis, medial and lateral ptyergoid muscles
How to examine CN V?
Cotton swab touch
Pain by pinprick
Temperature
Corneal reflex
Jaw reflex
Masticatory movements
Lesion to CN V?
Trigeminal neurgalgia, facial anesthesia or numbness, inability or difficulty to bite down
