The Cranial Nerves Flashcards
List All 12 Nerves In Order
I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII - Vestibulocochlear
IX - Glossopharyngeal
X - Vagus
XI - Accessory
XII - Hypoglossal
Mnemonic: Oh Oh Oh! To Touch And Feel Very Good Velvet. Ah, Heaven!
Basics
Cranial Nerve I
Name, Sensory/Motor/Both, Function
Name: Olfactory
Type: Sensory
Function: Smell
Basics
Cranial Nerve II
Name, Sensory/Motor/Both, Function
Name: Optic
Type: Sensory
Function: Vision
Basics
Cranial Nerve III
Name, Sensory/Motor/Both, Function
Name: Oculomotor
Type: Motor
Function: Most eye movement, eyelid movement
Basics
Cranial Nerve IV
Name, Sensory/Motor/Both, Function
Name: Trochlear
Type: Motor
Function: Eye movement
Basics
Cranial Nerve V
Name, Sensory/Motor/Both, Function
Name: Trigeminal
Type: Both
Function: Facial sensation, movement of biting/chewing/swallowing jaw muscles
Basics
Cranial Nerve VI
Name, Sensory/Motor/Both, Function
Name: Abducens
Type: Motor
Function: Eye movement
Basics
Cranial Nerve VII
Name, Sensory/Motor/Both, Function
Name: Facial
Type: Both
Function: Taste, facial sensation (a little) - all muscles of facial expression
Basics
Cranial Nerve VIII
Name, Sensory/Motor/Both, Function
Name: Vestibulocochlear
Type: Sensory
Function: Sound, sense of balance
Basics
Cranial Nerve IX
Name, Sensory/Motor/Both, Function
Name: Glossopharyngeal
Type: Both
Function: Taste and sensation from posterior tongue, muscles of pharynx (speech, swallowing)
Basics
Cranial Nerve X
Name, Sensory/Motor/Both, Function
Name: Vagus
Type: Both
Function: Outer ear canal sensation, motor control of heart, lungs, viscera (internal organs), larynx (speech), more
Vagus nerve - has long axons
Basics
Cranial Nerve XI
Name, Sensory/Motor/Both, Function
Name: Accessory
Type: Motor
Function: Movement of muscles of head rotation and shoulder shrug
Basics
Cranial Nerve XII
Name, Sensory/Motor/Both, Function
Name: Hypoglossal
Type: Motor
Function: Movement of tongue muscles (speech, swallowing)
Cranial Nerves
What does testing a sensory nerve pattern entail?
Looking for normal amounts of sensation, as well as symmetry (let each side/organ act on its own).
Symmetry helps determine whether you have a problem in the brain (slightly more likely with bilateral conditions) or in the cranial nerve (usually asymmetric).
Cranial Nerves
What does testing a motor nerve pattern entail?
Looking to see if the patient can use the muscle, and maintain that use with a little bit of resistance. Also, examining the muscle (how does the muscle tone feel, is there muscle atrophy).
What symptoms would we see after a TBI when there is damage to the ethmoid ridge, specifically the cribriform plate? Which cranial nerve is affected?
The olfactory nerve (I) is affected, as the ethmoid bone, due to a jarring hit to the head, shears off the axons/cuts them off. They do not grow back, thus it can potentially cause a permanent loss of smell.
What is one way (besides head trauma) to lose functions relating to the olfactory nerve (I)?
A viral infection, e.g. COVID
Cranial Nerve I - Examination
Know at least one way to examine the nerve’s function(s)
Testing one side of the nose at a time to detect symmetry:
* Occlude one nostril
* Put a common scent (e.g.) under the open nostril while the patient’s eyes are closed, and ask them to identify it
* Repeat with the other nostril to detect asymmetry
Olfactory Nerve
Cranial Nerve II - Examination
Know at least one way to examine the nerve’s function(s)
Hint: Almost everyone has had this type of test used on them, just not necessarily to assess nerve damage.
The optic nerve is tested using a visual acuity test, the most common of which is a Snellen Chart.
* The chart is placed a standardized distance away (e.g. 20 feet)
* (Using a near card if someone cannot see anything from 20 feet away - may not be testable)
* One eye is occluded, and acuity is assessed
* Then, repeat with the other eye
Might follow up with structural MRI, etc. as you cannot necessarily be sure of nerve damage just from this test - however asymmetrical vision increases the likelihood the optic nerve is at play
Papilledema
How it’s assessed, what does it look like, what’s it from, causes
Assessed via fundoscopy.
Causes the fundus (back of eye) to be distorted. Clear distinguishment of the macula (a little spot in the back of the eye) is normal, but with the papilledema it disappears. The centre and periphery of the vision blur together.
Caused by intracranial pressure (pressure pushing on the eye, swelling the fundus/optic disk). Often caused by hyperthyroidism or growth behind the eye.
Often tested for along with optic nerve (II) tests despite not being directly relevant.
Testing Nerves III, IV and VI
III - Oculomotor
IV - Trochlear (smallest nerve)
VI - Abducens
Testing - ask someone to follow an object or light. Can they track it smoothly, or do you see nystagmus?
Nystagmus
What is it and which nerves?
Abnormal jittery eye movement - can be caused by dysfunction in nerves III, IV or VI
Ptosis
What is it and which nerves?
Eyelid droopiness, blocking vision - cranial nerve III only
Gaze restrictions
Double vision from nerve dysfunction of III, IV or VI
[Blank] muscles control the eye, [#]/[#] muscles being controlled by oculomotor nerve.
Six muscles control the eye. 4/6 muscles being controlled by oculomotor nerve.
Testing Nerve V
Two Tests!
- Touching the face to examine for dysfunction (facial somatosensation) across the chin, cheek and forehead. THREE different regions for the THREE nerve sections!!!
- AND testing for motor function, observe the muscle to make sure it has even muscle tone jaw muscle movement
Testing Nerve VII
Responsible for facial MOVEMENT.
Easy to observe facial asymmetry in patients with nerve VII problems.
Examination: Asking patient to wrinkle forehead, frown, smile, pout, etc
This nerve also helps us taste, but we do not test this as we do not have a strong sense of taste, much of our flavour sensation comes from our ability to smell instead.
Not facial sensation! That’s the trigeminal nerve!
Bell’s Palsy
What is it? Which nerve?
- Viral infection that impacts cranial nerve VII
- Half of your face is effectively paralyzed
- Muscles in the face are drooping
- Usually goes away after a couple weeks
Testing nerve VIII
Vestibulocochlear Nerve:
Testing hearing/audition: Speak into one ear while occluding the other ear and get the person to repeat the words, then repeat
Labrynth/Balance: Testing coordination - Close your eyes and then march in place - if there is an issue with balancing, the person will start to rotate
Testing nerves IX and X
IX - Glossopharyngeal
X - Vagus
Help control pharynx and larynx (swallowing, gag reflex, speaking, etc.)
Vagus (vagus in Latin: to wander, vagabond) nerve specifically has long axons that control the parasympathetic nervous system/PNS
Test Found Online: Ask patient to say “ah,” if the palate/roof of mouth does not raise symmetrically, then this could be a sign of dysfunction in cranial nerve IX or X
Testing nerve XI
XI - Accessory Nerve
Helps out the spinal cord, enables you to lift your shoulders and turn your head.
Tests: Examine symmetry, get person to turn head in both directions while providing resistance, get them to raise their shoulders while providing resistance. Feel both shoulders to check for asymmetrical muscle tone/muscle wasting in one shoulder or the other.
Testing nerve XII
XII - Hypoglossal Nerve
Controls muscle movement of the tongue.
Tests: Get people to stick out their tongue and push the tongue into the inside of the cheek, see if there is asymmetry.
