Clinically Relevant Anatomy of Cranial Nerve Testing Flashcards
outline CNI course
- extracranial part in olfactory mucosa in nasal cavity
- 1st neuron: receptor cells pass through cribriform plate of ethmoid bone. these are replaced every so often by the basal cells
- 2nd neuron: olfactory bulb
- the olfactory tract ends in temporal lobe
what is different about CNI
it is the only sensory modality that doesnt synapse at the thalamus prior to reaching the cortex
the neurons are in contact with the outside world
outline CNII course
- formed from ganglion at back of retina
- passes through optic canal in sphenoid bone in middle cranial fossa
- travels to optic chiasm to form optic tract
- connects to CNS at diencephalon
- LGN in the thalamus is a connection point for it then to go to the primary visual cortex in the occipital lobe (level 4C)
how do you test CNI
not routinely done, cover one nostril and ask the patient to smell a familiar smell
outline CNIII course
- connects with CNS in midbrain
- travels towards orbit in lateral wall of cavernous sinus
- goes through superior orbital fissure
- supplies extraocular muscles and parasympathetics synapse in ciliary ganglion
outline CNIV course
- comes off posterior aspect of midbrain
- travels towards orbit in lateral wall of cavernous sinus
- goes through superior orbital fissure
- supplies superior oblique muscle ONLY
why is CNIV susceptible to damage
very long and thin
outline CNVI course
- comes off pontomedullary junction
- travels towards orbit in the cavernous sinus (not on lateral wall)
- goes through SOF
- supplies only lateral rectus muscle
outline CNXI course
- connects with CNS at cervical spinal cord
- ascends through foramen magnum and travels towards jugular foramen in posterior cranial fossa
- exits via jugular foramen in posterior cranial fossa
- supplies SCM and trazpezius
outline how to clinically test CNXI
- shrug shoulders and turn head against resistance
outline CNXII course
- connects with CNS via rootlets lateral to the pyramids of the medulla
- passes through hypoglossal canal in posterior cranial fossa
- descends lateral to carotid sheath (contains common and internal carotid artery and IJV and CNX)
- at the level of the hyoid bone turns anteriorly towareds the lateral aspect of the tongue
- supplies muscles in tongue (except palatoglossus)
CNXII clinical testing
ask patient to stick tongue out, tongue tip points towards side of injured nerve
which muscle of mastication opens the jaw
lateral pterygoid
which muscle in the palate and ear does CNV3 supply
tensor veli palatini and tensor tympani
attachments of masseter
- angle of mandible
- zygomatic arch/bone
attachment of temporalis
coronoid process of mandible
outline CNVII course
- CNS connection at pontomedullary junction
- goes into internal acoustic meatus in posterior cranial fossa to enter middle ear cavity in petrous part of temporal bone
- leaves via stylomastoid foramen
- geniculate ganglion here is an L shaped collection of sensory neurons of this nerve
- somatic motor axons pass into parotid gland then supply muscles of facial expression
- also special sensory (taste) and parasympathetic (submitted by chorda tympani??)
stapedius muscle
- CNVII in middle ear cavity in petrous temporal bone
- reduces stapes movement to protect the internal ear from excessive noise
chorda tympani course
- piggy backs on the lingual nerve (CNV3) transmitting taste to the anterior 2/3rd of tongue and parasympathetic fibres to the submandibular and sublingual glands
name 4 movements to clinically test motor function of CNVII
- raise eyebrows
- close eyes tightly
- smile
- puff out cheeks and hold air
CNIX supplies
- somatic motor: stylopharyngeus muscle
- special sensory: vallate papillae (have taste buds) on posterior 1/3 of tongue
- parasympathetic: parotid gland
- general sensory: pharyngeal mucosa (laryngopharynx also CNX), posterior 1/3 of tongue, palatine tonsil, eustahcian tube, middle ear cavity
- visceral afferents: carotid body and sinus
how to test CNIX
elicit gag reflex
clinical testing of CNX
open mouth and say ahhh - uvula will be pulled away from non functioning side
