Cranial nerves part 1 + 2

Question 1

name the 12 cranial nerves

Answer 1

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

Question 2

Which cranial nerve is the Olfactory nerve, explain where it is anatomically and what sensations it gives?

Answer 2

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

Question 3

Which cranial nerve is the Optic nerve, explain where it is anatomically and what sensations it gives?

Answer 3

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

Question 4

If you have a lesion to the optic nerve on one side what do u expect the patients defect to be? (After chiasm)

Answer 4

patient will lose vision in that eye (monocular vision loss)

Question 5

a patient has a pituitary tumour that has blocked their optic chiasm? What has happened to their vision?

Answer 5

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

Question 6

if u have a lesion to ur optic tract, what happens to ur eyesight?

Answer 6

homonymous hemianopia (you’d lose either the left or the right side of each field of view aka each eye loses part of sight)

Question 7

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?

Answer 7

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

Question 8

Name the 6 extra ocular muscles (look up diagram to make sure u know where these are)

Answer 8

• 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

Question 9

what are the 6 movements of the eye and the muscles that allow this

Answer 9

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)

Question 10

What is cranial nerve III, explain where it is anatomically and what sensations it gives?

Answer 10

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

Question 11

what does the muscle levator palpabrae superioris mean literally/ what does it do and what nerve is it innervated by

Answer 11

levator= elevates
palpabrae= eyelid
superioris= superior

it open ur upper eyelid! its innervated by occulomotor nerve

if its damaged, eye droops (PTOSIS)

Question 12

What muscle constricts the pupil, what musclle dilates pupil. Which one is innervated parasympathetically and which one is sympathetically innervated

Answer 12

constrictor pupillae constricts pupil (parasympathetic innervation)
dilator pupillae dilates pupil (sympathetic innervation)

Question 13

what does oculomotor palsy look like?

Answer 13

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.

Question 14

what does trochlear palsy look like?

Answer 14

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.

Question 15

what does abducens palsy look like?

Answer 15

Abducens Palsy: paralysis of lateral rectus. Eyes cannot abduct. Eyes appear normal when looking forward.
Might be a sign of increased intracranial pressure.

Question 16

What does Horner’s syndrome look like?

Answer 16

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

Question 17

what cranial nerve (that comes from posterior surface of brainstem) carries motor fibres to supply superior oblique only

Answer 17

the trochlear nerve (CN IV) carries motor fibres to supply superior oblique

Question 18

which cranial nerve carries motor fibres to supply lateral rectus eye muscle?

Answer 18

Abducent nerve (CN VI) carries motor fibres to supply lateral rectus muscle

Question 19

The Trigeminal nerve (CN V) has 3 branches name them and what they innervate, then explain anatomy of these branches.

Answer 19

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

Question 20

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

Answer 20

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

Question 21

what are the symptoms and causes of cavernous sinus thrombosis

Answer 21

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.

Question 22

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

Answer 22

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

Question 23

The facial nerve has 7 branches, what are they + some anatomy/functions of them

Answer 23

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

Question 24

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?

Answer 24

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

Question 25

which cranial nerve is the vestibulocochlear nerve?

Answer 25

CN VIII

The vestibulocochlear nerve emerges from the pons and enters the internal acoustic meatus.

It has special sensory fibres, for hearing and balance

Question 26

which cranial nerve emerges from the lateral surafce of the medulla oblongata with the vagus nerve, they both exit the skull via the jugular foramen. They have an overlapping distribution in the head and neck

Answer 26

cranial nerve IX is the glossophryngeal nerve and it emerges from the lateral surafce of the medulla oblongata with the vagus nerve, they both exit the skull via the jugular foramen. They have an overlapping distribution in the head and neck

glossopharyngeal nerve has general sensory + motor fibres are as well as parasympathetic + special sensory fibres

Question 27

The glossopharyngeal nerve has general sensory + motor fibres as well as parasympathetic + special sensory fibres

It provides special sensory + general sensory supply to what part of the tongue?

What gland gives parasympathetic supply

Answer 27

glossopharyngeal (IX) provides the posterior 1/3 of the tongue with special

Question 28

what cranial nerve provides general sensory fibres to the carotid body + sinus which provide info about blood pressure + oxygen saturation respectively

as well as general sensory supply to the pharynx, as well as one muscle of the pharynx (stylopharyngeus)

Answer 28

The glossopharyngeal nerve (CN IX) provides general sensory fibres to the carotid body + sinus which provide info about blood pressure + oxygen saturation respectively

Glossopharyngeal nerve has general sensory supply to the pharynx, as well as one muscle of the pharynx (stylopharyngeus)

Question 29

what is Bell’s palsy? What is the difference between Bell’s palsy and a person experiencing a stroke

Answer 29

Bell’s Palsy: Facial muscle paralysis due to lower motor lesion of CN VII (facial nerve).
* Lower half of face paralyzed as well as one side of forehead.
* Leads to droopy eyelid, dry eye/excessive tears.
* Drooping corner of mouth, impaired taste, dry mouth.
Difficulty chewing, inability to form some words (beginning with P), inability to whistle, blow bubbles.

Question 30

the vagus nerve is which cranial nerve?
The vagus nerve contains general motor, sensory + parasympathetic fibres; explain some places it innervates

Answer 30

The vagus nerve (CN X)

*provides the soft palate (elevates during swallowing to prevent food entering nasal cavity) , pharynx + oesophagus w motor supply
* innervates larynx w general + motor supply
* MAJOR PARASYMPATHETIC NERVE OF BODY; foregut, midgut

Question 31

uvula deviation is a sign of damage to which cranial nerve?

Answer 31

uvula deviation is a sign vagus nerve (CN X) is damaged

n.b. uvula deviates away from side that is damaged; so if left side damaged uvula will point to right

Question 32

where does the spinal accessory nerve originate from: describe anatomy + which cranial nerve it is

Answer 32

spinal accessory nerve (CN XI) originates from spinal cord; emerges from first 5-6 cervical segments and then runs superiorly through foramen magnum then leaves skull via jugular foramen.

Spinal accessory contains motor fibres innervating the sternocladiomastoid (turns head side to side or nodding) + trapezius (shrugs shoulders) muscle

Question 33

sympathetic innervation to head and neck does not come from cranial nerves, but from the ___________ of the spinal cord>

The sympathetic fibres travel into the head w the internal carotid artery (ICA)

Answer 33

sympathetic innervation (T1-L2) to head and neck does not come from cranial nerves, but from the thoracic region of the spinal cord

The sympathetic fibres travel into the head w the internal carotid artery ICA

Question 34

which cranial nerves have parasympathetic fibres

Answer 34

• occulomotor (head + neck)
• facial (head + neck)
• glossopharyngeal (head + neck)
• vagus

Question 35

Horner’s syndrome is ____ ptosis + constricted pupil, whereas Occulomotor palsy is ___ ptosis + dilated pupil

Answer 35

Horner’s syndrome is partial ptosis + constricted pupil, whereas Occulomotor palsy is complete ptosis + dilated pupil