Anatomy - Cranial Nerves Flashcards
Three nerves for the eye
- Oculomotor (III)
- Trochlear (IV)
- Abducent (VI)
Oculomotor nerve course
- from brainstem, in between the two pillars
- lies upon circle of willins
- to cavernous sinus (on lateral wall)
- through superior orbital fissure
- gives off motor nerves
- parasympathetic goes through ciliary ganglion
Through which foramina does the oculomotor nerve exit?
Superior orbital fissure
What ganglion does the parasympathetic part of oculomotor go through
Ciliary Ganglion
What does the parasympathetic fibers of the oculomotor nerve innervate
- Ciliaris
- sphincter pupillae
What do the motor fibers of the oculomotor nerve innervate
- Most muscles of the eye except SO and LR
- LPS
- MR
- SR
- IO
- IR
Clinical issues with the oculomotor nerve
- hemmorage near circle of willis, aneurysms
- pupil dilation: mydriasis
- no pupillary reflex
- no accomodation
- lateral squint: down-out
- diplopia: double vision
- ptosis: because LPS is damaged
Trochlear nerve course
- only cranial nerve that crosses to the other side in the periphery
- goes through cavernous sinus on lateral wall
- exits skull through the orbital fissure
- along the superior eyelid
What type of fibers does the trochlear nerve have
- only motor
What fissure does the trochlear nerve exit by
- Superior orbital fissure
What does the trochlear nerve innervate
- Superior oblique
Clinical issues for the trochlear nerve
- rise in intracranial pressure
- slight lateral squint (extortio) - patients may try to correct this by tilting their head to one side. This is because the inferio oblique is rising the eye and SO cant contradict it
- weak eye depression when adducted
- diplopia
Abducent nerve course (VI)
- stupid
- down then hits sphenoid bone, goes back up
- goes through cavernous sinus next to internal carotid
- exits via superior orbital fissure
- innervates lateral rectus
What fissure does the abducent nerve use to exit the skull?
- the superior orbital fissure
What does the motor fibers of abducent nerve innervate?
- lateral rectus
What type of fibers does the abducent nerve have?
- motor only
Clinical issues with abducent nerve
- carotid dilation, pathology, rICP
- medial squint: esotropia: diplopia
Two cranial nerves for the face area
- Trigeminal (V)
- Facial (VII)
Trigeminal nerve three parts
- ophtalmic: V1
- Maxillary: V2
- Mandibular: V3
V1 and V2 are purely snesory
V3 is sensory but has a motor component
Trigeminal nerve course
- where does the trigeminal nerve exit?
- where does it form a swelling
- Where does V1 go through?
- Where does V2 go through?
- where does V3 go through?
- Exit midbrain through Merkel’s cave
- forms a swelling over the petrous temporal bone and then fibers separate
- V1 through superior orbital fissure
- V2 through foramen rotundum
- V3 through foramen ovale
What is the sensory innervztion of V1
- scalp
- forehead
- sinus
- eyelids
- nose
- nasal cavity
- eye
- HEAD BLOOD VESSELS
- MENINGES (particularly dura)
What is the sensory innervation of V2
- upper teeth
- palate, sinus
- cheek
- upper lip
- nose
- nasal cavity
- oral cavity
- pharynx
What is the sensory innervation of V3
- Lower teeth,
- tongue
- lower lip
- chin
- jaw
- ear
What is the motor innervation of V3
- Mastication muscles
- TVP
- Tensor tympanic
- mylohyoid
- ant digastric
Clinical issues of trigeminal
- sensory face loss: neuralgia, shingles
- mastication issues: jaw deviation
- headaches: artery dilation/pathology, visceral issues, rICP
Facial nerve course
- where does it exit?
- where does the ganglion form
- what structures does it pass
- exits via internal acoustic meatus
- forms a swelling at facial sensory gnaglion and then first division
- second division after tympanic cavity
First division of facial nerve:4 courses
1) parasympathetic fiber goes above petrous temporal bone, through trigeminal ganglion. Synapse into pterygopalatine ganglion and post-ganglionic fiber go to lacrimal gland
2) motor fiber to stapediues
3) sensory fibers to ear, auricle
4) some parasympathetic and motor fibers continue
Second division of facial nerve
- what fissures do motor fibers and parasympathetic fibers go through?
- what is the ganglion that the parasympathetic fibers synapse to, and where do post-ganglion neurons go to?
- after the first division: goes through tympanic cavity and then further divide
- Motor fibers continue down over mastoid process through stylomastoid foramen and parotid gland
- parasympathetic fiber go through petrotympanic fissure and take advantage of chorda tympani (lingual nerves to send fibers to V3 lingual) - synapse into submandinbular ganglion and post ganglionic fibers innervate submandibular gland and sublingual gland. This is also the path for taste nerves that go to anterior 2/3 of tongue
What do the fibers of facial nerve innervate?
- parasympathetic
- sensory
- taste
- motor
- Parasympathetic: lacrimal gland, submandibular/sublingual gland
- Sensory: ear
- Taste: anterior 2/3 of tonghe
- motor: muscles of facial expression + stapedius, stylohyoid, post digastric
Clinical issues with facial nerve
- intracranial: sensory/visceral issues ( + hyperacusis), Motor (bell’s palsy): middle ear infection/shingles
- extracranial: motor (Bell’s palsy): Parotid tumour/infections/ mastoid trauma
NErve that innervates ear
- Vestibulo cochlear
Cochlear nerve: function
- Sensory: hearing, frequency maps
Cochlear nerve: Clinical issues
- abscess/tymour, internal acoustic meatus, inner ear damage
- hearing loss: Rinne and Weber test to distinguish between sensorineural and conductive
- tinnitus
What foramina does the vestibulocochlear nerve use to exist brainstem?
- internal acoustic meatus
VEstibular nerve function
- sensory
- balance
- posture: position, movement
- ocular (head eye together, stable retinal moves)
Clinical issues with vestibular nerve
- Posture: balance loss, unsteady (without eyes)
- ocular: no eye-head moves, nystagmus
- visceral issues: vertigo, vomit, nausea
- will always fall towards sign of lesion
Innervation of mouth 3 nerves
- glossopharyngeal
- vagus
- hypoglossal
Glossopharyngeal nerve (IX) course
- foramen to leave brainstem
- swelling
- 5 branches off
- leave brainstem through jugular foramen
- swelling at glossopharyngeal sensory ganglion
- 1st branch off: parasympathetic fiber to parotid gland and sensory fiber to middle ear
- 2nd branch off: sensory fiber to carotid body
- 3rd branch off: motor nerve to stylopharyngeus
- 4th branch off: sensory and taste to posterior 1/3 of tongue
- 5th branch: sensory to oropharynx
Parasympathetic fibers of glossopharyngeal
- above which bone?
- synapse to which ganglion?
- what do postganglionic fibers innervate
- go above petrous temporal bone
- synapse into otic ganglion
- post ganglionic fiber go to parotid gland
Sensory fibers of glossopharyngeal nerve
- oropharynx
- posterior 1/3 of tongue
- carotid body
Taste fibers of glossopharyngeal nerve
- posterior 1/3 of tongue
- Motor fibers of glossopharyngeal
- stylopharyngeus
CLinical issues of glossopharyngeal
- sensory-visceral issues
- no gag reflex
- rare
What foramina does the vagus nerve use to exit midbrain
- jugular foramen
Then form vagus sensory ganglion
Divisions of vagus nerve: sensory
- one to aorta/baroreceptors
- two separate fibers to vocal folds (posterior and superior)
- laryngopharynx
- thorax/ upper GIT
Taste fibers of vagus
- to larynx
- parasynmpathetic fibers of vagus
- go through carotid sheath with IJV and CCA an then synapse into thorax/abdomen ganglia
- post ganglioninc fiber innervate thorax and upper GIT
Motor branches of vagus nerve
- pharyngeal plexus (middle constrictor)
- muscles of palate (except TVP)
- muscles of pharync (except stylopharyngeus)
- Cricothyroideus and cricopharyngeus
- all laryngeal muscles except cricothyroideus
Clinical issues with vagus nerve
- sensory-visceral issues
- dysphonia: recurrent laryngeal is damaged - cant contract cricothyroideus
- dysphagia: problem swallowing because constrictors are not working
- dyspalatia; problems with palate
Hypoglossal nerve: course
- exit midbrain through hypoglossal canal
- crosses carotid around the loop of lingual
Hypoglossal nerve: innervation
- only motor: tongue
- hyoglossus
- all glossal muscles except palatoglossus
Clinical issues with hypoglossal nerve
- nearly always unilateral
- glossal palsy: ask to stick tongue out: deviation to the right (side of lesion)
Accessory nerve: neck nnervation
- what spinal levels
- what foramen
- what muscles
- at spinal cord level C1-6
- exit through jugular foramen
- separates into to innervate SCM and trapexius
Accessory nerve clinical issues
- shoulder/head movement
- viral infection?
- difficulty turning to opposite side of lesion and shrugging shoulder
