Cranial Nerves Flashcards
what is the sensory and/or motor function of CN I - Olfactory Nerve?
only sensory for special sensation of smell (olfaction)
what is the CNS origin of CN I?
emerges from the forebrain
what cranial fossae and foramina does CN I travel through?
- anterior cranial fossa
- cribriform plate (ethmoid)
what is the location of the ganglia/nuclei and the cortical region CN I is destined for?
- olfactory glomeruli
- olfactory cortex of temporal lobe
what is the clinical relevance of CN I?
the cribriform plate is a weak spot of the anterior cranial fossa so trauma/fracture could lead to anosmia
what is the sensory and/or motor function of CN II - Optic Nerve
only sensory for special sensation of sight
what is the CNS origin of CN II?
forebrain
what cranial fossae and foramina does CN II travel through?
- retinal ganglion cell axons pass through the optic canal
- axons continue in the optic tract after the optic chiasm of the middle cranial fossa
what is the location of the ganglion/nuclei of CN II and what is its cortical region destination?
- lateral geniculate nucleus of the thalamus
- occipital lobe
what is the clinical relevance of CN II?
optic nerve trauma or pathological damage results in anopsia
what is the sensory and/or motor function of CN III - Occulomotor Nerve
only motor for somatic efferent innervation to extraocular muscles and parasympathetic innervation to intraocular muscles
what are the extraocular and intraocular muscles innervated by CN III?
Extraocular
- superior rectus
- inferior rectus
- medial rectus
- inferior oblique
- levator palpebrae superioris
Intraocular
- pupillary constrictors
- ciliary muscles
what is the CNS origin of CN III?
midbrain
what cranial fossa and foramina does CN III travel through?
- middle cranial fossa
- superior orbital fissure
what is the location of the ganglion/nuclei of CN III and what is its cortical region destination?
- oculomotor nuclei (edinger-westphal) in midbrain
- frontal eye field in the frontal lobe
what is the clinical relevance of CN III?
- CN III palsy can cause ptosis, mydriasis and the eye to be oriented down and out when looking straight.
- sudden onset of these symptoms suggests trauma, aneurysm or brain herniation
what is the sensory and/or motor function of CN IV - Trochlear Nerve?
only motor for somatic innervation to one extraocular muscle (superior oblique) for intorsion, depression and abduction
what is the CNS origin of CN IV?
dorsal midbrain
what cranial fossa and foramina does CN IV travel through?
- middle cranial fossa
- superior orbital fissure
what is the location of the ganglion/nuclei for CN IV and what cortical region is its destination?
- trochlear nucleus in midbrain
- frontal lobe
what is the clinical relevance of CN IV?
- eye would be elevated and adducted due to unopposed actions of superior rectus and medial rectus
- eye is extorted due to unopposed action of inferior oblique which causes a compensatory head tilt
look at Trigeminal nerve lecture for details
what is the sensory and/or motor function of CN VI - Abducens Nerve?
only motor for somatic efferent innervation to one extraocular muscle (lateral rectus) for abduction
what is the CNS origin for CN VI?
pontomedullary junction
what cranial fossa and foramina does CN VI travel through?
- middle cranial fossa
- superior orbital fissure
what is the ganglion/nuclei of CN VI and what is its cortical destination?
- abducens nucleus located in the pons
- frontal lobe
what is the clinical relevance of CN VI?
eye is adducted due to unopposed medial rectus muscle when looking straight
look at Facial nerve lecture for details
what is the sensory and/or motor function of CN VIII - Vestibulocochlear Nerve?
only sensory for special sensations of hearing and balance
what is the CNS origin of CN VIII?
pontomedullary junction
what cranial fossa and foramina does CN VIII travel through?
- posterior cranial fossa
- internal acoustic meatus
what is the ganglion/nuclei of CN VIII and what is its cortical region destination?
- vestibular and cochlear nuclei in pons/medulla
- temporal lobe (auditory) parietal lobe (vestibular)
what is the clinical relevance for CN VIII?
- labryrinthitis: inflammation of the membraneous labyrinth resulting in damage to branches of vestibularcochlear nerve leading to sensorineural hearing loss or tinnitus
- lesion at the internal acoustic meatus or in the petrous temporal bone can lead to ipsilateral hearing loss and vertigo (CN VII can also be damaged)
what is the sensory and/or motor function of CN IX - Glossopharyngeal Nerve?
Sensory
- general to posterior tongue, oropharynx, middle ear and eustachian tube
- special to posterior tongue for taste
Motor
- somatic is inconsequential
- autonomic is parasympathetics for secretomotor to parotid gland
what is the CNS origin for CN IX?
medulla
what is the fossa and foramina that CN IX travels through?
- posterior cranial fossa
- jugular foramen
what is the ganglion/nucleus for CN IX and which cortical region is its destination?
- nuclei located in medulla
- taste registers to the insular cortex
what is the clinical relevance for CN IX?
- when testing the gag reflex, the stimulus is detected by the sensory receptors of CN IX
- IX, X and XI all pass through jugular foramen so a stenosis or space occupying lesion may effect all three
what is the sensory and/or motor function of CN X - Vagus Nerve?
Sensory
- general to larynx and pharynx
- visceral afferents to abdominal and thoracic organs
- special to taste for epiglottis
Motor
- larynx, pharynx and soft palate
- parasympathetics innervate smooth muscles of trachea, bronchi, gastrointestinal tract and regulated heart rhythm
what is the CNS origin for CN X?
medulla
what is the fossa and foramina that CN X travels through?
- posterior cranial fossa
- jugular foramen
where is the ganglion/nuclei located for CN X and what is the cortical region its fibers are destined for?
- medulla
- frontal lobe (motor commands) insular cortex (taste)
what is the clinical relevance for CN X?
- lesions are rare but some branches like the recurrent laryngeal are susceptible to compression
- far-ranging effects that pharmacotherapeutics take advantage of (beta blockers, muscarinic agonists and cardiac glycosides)
what is the sensory and/or motor function of CN XI - Spinal Accessory Nerve?
only motor for somatic efferent innervation to two muscles ( sternocleidomastoid and trapezius)
what is the CNS origin for CN XI?
medulla
what is the fossa and foramina that CN XI travels through?
- posterior cranial fossa
- jugular foramen (spinal portion ascend through foramen magnum)
where is the ganglion/nuclei located for CN XI and what is the cortical region its fibers are destined for?
- medulla and upper cervical spinal cord
- frontal lobe
what is the clinical relevance for CN XI?
- accessory nerve damage (iatrogenic) can cause muscle wasting and partial paralysis of the sternocleidomastoid resulting in inability to rotate the head or weakness in shrugging the shoulders
- can also cause asymmetric neckline
what is the sensory and/or motor function for CN XII - Hypoglossal Nerve?
only motor for somatic efferent innervation to the tongue muscles ( genioglossus, hyoglossus and styloglossus)
what is the CNS origin of CN XII?
medulla
what fossa and foramina does CN XII travel through?
- posterior cranial fossa
- hypoglossal canal
where is the ganglion/nuclei located for CN XII and what is the cortical region its fibers are destined for?
- located in the medulla
- frontal lobe
what is the clinical relevance of CN XII?
- lesions superior to the hypoglossal nucleus will cause contralateral tongue deviation
- lesions inferior to the CN XII nucleus results in ipsilateral tongue deviation
