Cranial nerves part 1 + 2 Flashcards
name the 12 cranial nerves
CN I= Olfactory
CN II= Optic
CN III= Oculomotor
CN IV= Trochlear
CN V= Trigeminal
CN VI= Abducens
CN VII= Facial
CN VIII= Vestibulocochlear
CN IX= Glossophryngeal
CN X= Vagus
CN XI= Accessory
CN XII= Hypoglassal
Which cranial nerve is the Olfactory nerve, explain where it is anatomically and what sensations it gives?
Olfactory nerve (CN I) is a sensory nerve.
It runs inferiorly from the olfactory bulb, though the perforated cribiform plate of ethmoid bone to enter the nasal cavity.
It has special sensory fibres conveying SMELL
Which cranial nerve is the Optic nerve, explain where it is anatomically and what sensations it gives?
The Optic nerve (CN II) traverses the optic canal to enter the orbit
approximately 10 mm superior to the pituitary gland within the suprasellar cistern.
The optic nerve is made entirely of special sensory fibres conveying VISION
If you have a lesion to the optic nerve on one side what do u expect the patients defect to be? (After chiasm)
patient will lose vision in that eye (monocular vision loss)
a patient has a pituitary tumour that has blocked their optic chiasm? What has happened to their vision?
tumour has blocked optic chiasm (crossing of temporal fields of view)= tunnel vision aka bitemporal hemianopia so u lose ur temporal (outer) fields of view
if u have a lesion to ur optic tract, what happens to ur eyesight?
homonymous hemianopia (you’d lose either the left or the right side of each field of view aka each eye loses part of sight)
What part of the brain do the 3 cranial nerves that traverse the superior orbital fissure to enter the orbit of the eye orginate from?
The Oculomotor (III), Trochlear (IV), and Abducens (VI) all traverse the superior orbital fissure to enter the orbit (bony cavity eye sits in/ eye socket) of the eye.
- oculomotor nerve emerges from the MIDBRAIN
- trochlear nerve emerges from the posterior surface of the MIDBRAIN
- abducens nerve emerges from the PONS
Name the 6 extra ocular muscles (look up diagram to make sure u know where these are)
- superior rectus
- inferior rectus
- medial rectus
- lateral rectus
*n.b. rectus means ‘straight’ - superior oblique
- inferior oblique
all of these APART FROM INFERIOR OBLIQUE are attached to the orbit by the COMMON TENDINOUS RING
what are the 6 movements of the eye and the muscles that allow this
rotation around vertical axis: abduction (lateral rectus contracts, superior and inferior oblique contract) /adduction (medial rectus contracts) aka moving eye side to side
rotation around transverse axis: elevation (superior rectus contracts, inferior oblique contracts) /depression (inferior rectus contracts, superior oblique contracts)
rotation around anterioposterior axis: intorsion (superior rectus contracts, superior oblique contracts) /extorsion (inferior rectus contracts, inferior oblique contracts)
What is cranial nerve III, explain where it is anatomically and what sensations it gives?
CN III= Oculomotor it carries motor fibres to supply superior rectus, inferior rectus, medial rectus, inferior oblique and levator palpabrae superioris
Also parasympathetic fibres for constrictor pupillae and ciliary body
what does the muscle levator palpabrae superioris mean literally/ what does it do and what nerve is it innervated by
levator= elevates
palpabrae= eyelid
superioris= superior
it open ur upper eyelid! its innervated by occulomotor nerve
if its damaged, eye droops (PTOSIS)
What muscle constricts the pupil, what musclle dilates pupil. Which one is innervated parasympathetically and which one is sympathetically innervated
constrictor pupillae constricts pupil (parasympathetic innervation)
dilator pupillae dilates pupil (sympathetic innervation)
what does oculomotor palsy look like?
OCULOMOTOR PALSY, pupil little bit dilated, eye is down and out (cuz only lateral rectus and superior oblique is working), droopy eyelid (PTOSIS)
deactivates all extra-ocular muscles except for superior oblique/lateral rectus.
Due to tone of these: eye will move in a down and out position
* Loss of levator Palpabrae superioris: eye slightly closes
* Dilated pupil (parasympathetic loss, also comes from oculomotor).
○ Double vision (diplopia).
○ Strabismus (eyes not aligned)
Can result from diabetes, hypertension, aneurysm, ischaemic event.
what does trochlear palsy look like?
Trochlear Palsy: (most subtle looking in clinical practise) paralysis of superior oblique (hard to diagnose)
* Right eye: moves up and in (extortion): patient tilts head to compensate!
* * patients have diplopia when they look down (double vision)
Tilting of head causes neck pain and headache.
what does abducens palsy look like?
Abducens Palsy: paralysis of lateral rectus. Eyes cannot abduct. Eyes appear normal when looking forward.
Might be a sign of increased intracranial pressure.
What does Horner’s syndrome look like?
Horner’s Syndrome (syphilis complication. Too): lack of sympathetic supply to the eye. Pupil constricts due to parasympathetic innervation (oculomotor) not being opposed. Also: ptosis (closing of eye) due to lack of tone in smooth muscle. Accommodate(can see close and far away) but don’t reflect (light doesn’t effect pupil) (they accommodate but don’t reflect your needs
Accomodation of eye: The pupil near response (PNR), also called the pupil near reflex, is the constriction of the pupil in response to looking at a nearby object, and the dilation of the pupil in response looking at a far-away object
Reflection- is to do with light constrict when its light, dilate when its dark
what cranial nerve (that comes from posterior surface of brainstem) carries motor fibres to supply superior oblique only
the trochlear nerve (CN IV) carries motor fibres to supply superior oblique
which cranial nerve carries motor fibres to supply lateral rectus eye muscle?
Abducent nerve (CN VI) carries motor fibres to supply lateral rectus muscle
The Trigeminal nerve (CN V) has 3 branches name them and what they innervate, then explain anatomy of these branches.
The Trigeminal nerve (CN V) emerges from the lateral surface of the pons and splits into 3 branches:
* opthalmic (V1)=
* maxillary (V2)=
* mandibular (V3)= innervates muscles of mastication (masseter, temporalis, lateral + medial pterygoid)
the opthalmic branch traverses(leaves through) the superior orbital fissure to enter the orbit
the maxillary branch leaves the cranium by passing through the foramen rotundum
the mandibular branch runs through the foramen ovale
= u can test each branch w cotton wool on the 3 regions of the face
what is the only place in body u have an artery travelling through a vein. What cranial nerves travel in the lateral wall of this place
the CAVERNOUS SINUS is the only place in body u have an artery (internal carotid artery) travelling through a vein
Travelling through the sinus with the internal carotid artery is the** abducent nerve**
Travelling through** lateral wall** of cavernous sinus is
* occulomotor nerve
* trochlear nerve
* ophthalmic nerve
* maxillary nerve
what are the symptoms and causes of cavernous sinus thrombosis
Cavernous sinus syndrome (CSS) is a condition caused by any pathology involving the cavernous sinus which may present as a combination of unilateral ophthalmoplegia (cranial nerve (CN) III, IV, VI), autonomic dysfunction (Horner syndrome) or sensory CN V1- CN V2 loss.
Patients with cavernous sinus thrombosis most commonly complain of fever, headache, periorbital swelling and pain, vision changes, such as photophobia, diplopia, loss of vision.
Cavernous sinus thrombosis is usually caused by bacterial infection that spreads from another area of the face or skull e.g. staphylococcal (staph) bacteria, which can cause: sinusitis – an infection of the small cavities behind the cheekbones and forehead.
which cranial nerve emerges from the pons, and passes through the internal acoustic meatus. This nerve then runs through the petrous temporal bone and exits skull via the stylomastoid foramen
the facial nerve (CN VII) emerges from the pons, and passes through the internal acoustic meatus. The facial nerve then runs through the petrous temporal bone and exits skull via the stylomastoid foramen
The facial nerve has 7 branches, what are they + some anatomy/functions of them
intracranially:
* chordae tympani (parasympathetic + special sensory)
* greater petrosal (parasympathetic) splits from facial nerve within temporal bone n.b. Greater petrosal nerve carries parasympathetic fibres to lacrimal gland (gland that produces tears)
extracranially:
* motor root of facial nerve runs out of stylomastoid foramen + splits into 5 branches (temporal, zygomatic {cheekbone}, buccal {cheek}, marginal mandibular, cervical) these collectively innervate muscles of facial expression
the chordae tympani splits from the rest of the facial nerve within the temporal bone + runs into infratemporal fossa to run towards the tongue, which part of the tongue does the chordae tympani innervate?
the chordae tympani splits from the rest of the facial nerve within the temporal bone + runs into infratemporal fossa to run towards the tongue and provides the anterior 2/3 with special sensory fibres. On its way it also provides the sublingual + submandibular glands with parasympathetic fibres
