testing cranial nerves

Question 1

what is the brainstem?

Answer 1

adjoins the brain to the spinal cord

continuous with spinal cord caudally

Question 2

how many parts are there to the brainstem? what are they?

Answer 2

3:
1 - midbrain (most superior)
2 - pons
3 - medulla (most caudal - continuous with the spinal cord)

Question 3

what is the role of the brainstem?

Answer 3

regulation of cardio-respiratory functions and maintaining consciousness

Question 4

what runs through the brainstem?

Answer 4

ascending and descending fibres between the brain and rest of body

Question 5

what is the brainstem the major location for?

Answer 5

majority of cranial nerve nuclei

Question 6

what is nuclei?

Answer 6

collections of cell bodies of nerve fibres that make up the whole cranial nerve

Question 7

how do you test for olfactory nerve (CN I)?

Answer 7

test 1 nostril at a time

smelling salts

Question 8

how do you test for optic nerve (CN II)?

Answer 8

test 1 eye at a time

visual tets and pupils

Question 9

how are optic nerves usually seen?

Answer 9

directly with fundoscopy (see the optic disc)

Question 10

what is different about olfactory and optic nerve?

Answer 10

paired anterior extensions of the forebrain rather than ‘true’ cranial nerves
arise from forebrain

Question 11

what is optic nerve part of?

Answer 11

the visual pathway

Question 12

describe the visual pathway

Answer 12

retina of the eyes –> optic nerve –> optic chiasm (mixing of fibres) –> optic tract –> (passes through thalamus) –> optic projection fibres –> visual cortex

Question 13

how do you test for oculomotor nerve (CN III)?

Answer 13

inspection of eyelid and pupils
eye movements
pupillary light reflexes

Question 14

what is the course of oculomotor nerve?

Answer 14

runs through cavernous sinus after leaving midbrain, exits the cavernous sinus to enter the superior orbital fissure

Question 15

what is the cavernous sinus?

Answer 15

full of venous plexus (interconnected veins), created by dura (periosteal and meningeal) - the 2 dura layers split creating the space called cavernous sinus

Question 16

which structure runs through the cavernous sinus?

Answer 16

internal carotid artery

Question 17

clinical: how can infection spread to the cavernous sinus? leading to?

Answer 17

spread from the face, into cavernous sinus (thrombosis), blocking cavernous sinus, leading to pressure increase and compressing the oculomotor nerve (3rd nerve palsy)

Question 18

which lesions tend to involve the pupil? which do not?

Answer 18

compressive lesions involves pupil

vascular lesions spare pupil

Question 19

how do you test for trochlear nerve? (CN IV)

Answer 19

eye movements

Question 20

what is the route taken by the trochlear nerve (CN IV)?

Answer 20

longest intracranial route of all CNs
only CN to arise from DORSAL aspect of brainstem
through superior orbital fissure into the orbit
passes through the cavernous sinus

Question 21

which 2 nerves arise from midbrain?

Answer 21

oculomotor

trochlear

Question 22

how do you test for trigeminal nerve?

Answer 22

sensation to face (sensory)

motor: muscles of mastication

Question 23

where do the 3 branches of the trigeminal nerve synapse before branching off?

Answer 23

trigeminal ganglion

Question 24

which of the 3 branches of the trigeminal nerve are most superior (forehead)?

Answer 24

opthalmic (forehead) > maxillary (zygomatic bone - cheeks) > mandibular (most inferior - chin)

Question 25

how do you test for abducens nerve (CN VI)?

Answer 25

eye movements

Question 26

what is the route taken by the abducens nerve?

Answer 26

pons --> cavernous sinus --> superior orbital fissure --> orbit --> lateral rectus muscle

Question 27

how come abducens nerve is easily stretched? (CN VI)

Answer 27

nerve can be easily stretched in raised ICP due to its running under the surface of the pons upwards towards cavernous sinus

Question 28

how do you test for motor function of facial nerve (CN VII)?

Answer 28

muscles of facial expression

Question 29

how do you test for special sensory of facial nerve (CN VII)?

Answer 29

anterior 2/3 tongue (taste)

Question 30

what are the autonomic parasympathetic innervation of the facial nerve?

Answer 30

lacrimal and salivary glands

Question 31

how do you test for vestibulocochlear nerve? (CN VIII)

Answer 31

hearing | Rinne's and Weber's test

Question 32

what is the route taken by vestibulocochlear nerve (CN VIII)?

Answer 32

through internal acoustic meatus | through same hole as ear - petrous part of temporal bone

Question 33

what is an acoustic neuroma also known as?

Answer 33

schwannoma

Question 34

where do acoustic neuroma commonly occur?

Answer 34

in the cerebellopontine angle

Question 35

what does an acoustic neuroma in the cerebellopontine angle lead to?

Answer 35

compromising cranial nerves V, VII, VIII

Question 36

what are the 4 cranial nerves arising from pons?

Answer 36

trigeminal (V) abducens (VI) facial (VII) vestibulocochlear (VIII)

Question 37

how do you test for the glossopharyngeal nerve?

Answer 37

gag reflex (sensory limb) taste not often formally tested tested in conjunction with CN X

Question 38

course of glossopharyngeal nerve?

Answer 38

medulla oblongata --> jugular foramen

Question 39

function of carotid branch of glossopharyngeal nerve (IX)?

Answer 39

carries sensory (afferent signal) from carotid body (chemoreceptors - blood oxygen and CO2 levels) to cardiorespiratory centres in brain medulla

Question 40

testing for vagus nerve (CN X)?

Answer 40

noting speech swallow cough gag reflex (efferent limb)

Question 41

route of vagus nerve (CN X)?

Answer 41

brainstem medulla --> jugular foramen

Question 42

where does left recurrent laryngeal nerve travel under?

Answer 42

arch of aorta

Question 43

where does right recurrent laryngeal nerve travel under?

Answer 43

right subclavian artery

Question 44

how do you test for spinal accessory nerve (CN XI)?

Answer 44

shrug shoulders | turn head against resistance

Question 45

route of spinal accessory nerve (CN XI)?

Answer 45

through jugular foramen

Question 46

how do you test for hypoglossal nerve (XII)?

Answer 46

inspection and movement of the tongue

Question 47

route of hypoglossal nerve (CN XII)?

Answer 47

medulla --> hypoglossal canal --> supply muscles of tongue

Question 48

where does CN XII run?

Answer 48

runs medial to angle of mandible; crosses internal and external carotid arteries in neck

Question 49

which are the 4 nerves from the medulla?

Answer 49

glossopharyngeal vagus accessory hypoglossal

Question 50

what are the 4 sections of cranial nerve origins on the brain and nerves in each section?

Answer 50

brain - I, II midbrain - III, IV pons - V, VI, VII, VIII medulla - IX, X, XI, XII