Neuro exam cranial nerves Flashcards
How do you usually test for CN 1
Ask if they’ve noticed a change in their sense of smell
What are some causes of anosmia?
Covid Cold/flu Head trauma Brain tumor Covid Meningitis Parkinsons Blocked nostrils Genetic eg Kalmans
Is CN 1 sensory or motor?
Sensory
Is CN II sensory or motor?
Sensory
What should you look for when inspecting pupils?
Size
Shape
Symmetry
What is the medical name for asymmetry in pupil size?
Anisocoria
What are some causes of anisocoria?
Physiological
Oculomotor nerve palsy
Horner’s syndrome
Holmes-Adie syndrome
What is Holmes-adie syndrome?
Uneven pupil due to viral/bacterial infection
Pupil does not respond well to light but will accomodate
What does a down and out dilated pupil suggest?
3rd nerve palsy
What does pupilary constriction and ptosis indicate?
Horner’s syndrome
How do you identify an abnormal pupil?
Shine a light in their eyes and whichever is larger is likely to be abnormal, similarly in a dark room the smaller pupil is likely to be abnormal
How do you test for visual acuity when testing CH II?
Use Snellen’s chart (with glasses/contacts if they usually wear them)
Get them to stand 6 meters away and read downwards
If not use a pinhole
How is visual acuity using snellen’s chart calculated?
Chart distance (numerator)/lowest line read (denominator)
What happens if they are unable to read snellen’s chart at 6 meters?
Bring the chart closer ie 3 meters, if still not then at 1 meter, if not get them to count fingers, if not ask them to say when their hand moves, if not ask if they can see light
How do you test identification of hand movement?
Tell them to point to the moving hand, move both one by one then together, when you move both they can only focus one at a time
Where will a lesion be if there is neglect wherein the patient cannot identify movement?
Parietal lobe
Where will a lesion be if a patient has visual neglect on the left?
Right side of parietal lobe (contralateral)
How do you test for peripheral vision in the visual field?
Get them to cover one eye and tell them to look at your nose. Bring your finger from a corner in towards and ask them to say when they can see your finger. Do this 4 times starting at each corner and then repeat for the other eye. Make sure your hand is in the midline!!!
How does the PITS acronym help you identify what visual field loss there will be?
Parietal lobe lesion = inferior quadrantanopia
Temporal love lesion= superior quadrantanopia
What are the afferent and efferent pathways for the pupillary light reflex
Afferent= optic nerve/ CNII Efferent= oculomotor nerve/ CN III
How do you do the pupillary light reflex?
Shine a light into one eye and look for constriction then do the same and look in the other eye for consensual constriction.
Don’t bring it in slowly bring it from outside straight in front of the eye
What does the swinging light test test for?
Relative afferent pupillary defect
How does the swinging light test work?
If you suspect a defect in one eye, shine a light in it and it will constrict a bit (and look normal)
Then shine the light into the other eye and it will constrict more
Then shine it back into the defect eye and it will appear to dilate because the normal eye constricts more
What are causes of relative afferent pupillary defect?
Optic MS
Optic nerve lesion on the side of the defected pupil
How do you test for accomodation reflex? What is the normal response?
Get them to look at something far and then something near
Their pupil should constrict and converge
What are the tests for the optic nerve?
Inspect the pupils Visual acuity Visual inattention/neglect Visual fields Pupillary light reflex Accomodation reflex Colour vision Blind spot Fundoscopy
What chart is used to test colour vision?
Ishihara
Are CN III, IV and VI sensory or motor?
Motor
What are causes of ptosis?
3rd nerve palsy
Horner’s
Neuromuscular eg myasthenia gravis
Congenital
How do you test for CN III?
Observe the eyelid
How do you remember which nerve controls which eye muscle?
LR6SO4
Lateral rectus= CN VI
Superior oblique= CN IV
If the 3rd nerve is damaged which eye muscles are left working and what does this cause?
Lateral rectus and superior oblique work= down and out
What may be seen in a partial 3rd nerve palsy?
Pupil may still dilate, ptosis may be less marked
What is nystagmus?
Flickering of the eyelid
What causes nystagmus?
Congenital
Central (cerebellar lesion or midbrain)
Peripheral (vestibular system)
Physiological
What should you ask for before doing the H test?
Do they have double vision or pain?
Is CN V sensory or motor?
Both
How do you test for sensation of CN V?
Cotton wool on 6 spots on the face with eyes closed and tell them to say yes when they feel it
Do it on the sternum first to show what it feels like
What are the 3 sensory components of CN V?
Ophthalmic= V1 Maxillary= V2 Mandibular= V3
What muscles does CN V innervate?
Masseter and temporalis
What are the afferent and efferent nerves for the corneal reflex?
Aff= CN V Eff= CN VII
What reflexes does CN V control?
Corneal and jaw jerk
What are the afferent and efferent nerves for the jaw jerk reflex?
Both CN V
What reflexes are tested for when examining CN V?
Usually none as corneal and jaw jerk are uncomfortable
Is CN VII motor or sensory? How?
Motor= muscles of facial expression Sensation= taste and anterior 2/3 of the tongue
How do you test the motor components of CN VII
Raise your eyebrows
Close your eyes and dont let me open them
Blow out your cheeks and dont let me deflate them
Do a big grin with teeth
If theres a facial nerve palsy how do you know if its and UMN or LMN lesion?
LMN= unilateral weakness of all ipsilateral facial muscle including the forehead (bell's palsy) UMN= unilateral weakness of contralateral facial muscles with forehead sparing
Why is the forehead spared in an UMN lesion in facial palsy?
There is double innervation so the forehead is innervated again below the original lesion
Is CN VIII sensory or motor?
Sensory
What is the function of CN VIII? How do you test for this?
Hearing and balance, ask about them
How do you do a gross hearing assessment for CN VIII?
Close one ear and then in the other ear whisper something or rub your fingers together and ask if they can hear it
What is Rinne’s and Webber’s test used for?
To see if hearing loss is conductive or sensorineural
Which tuning fork is used in Rinne’s test if they give you 2?
The smaller one or 512
How do you do Rinne’s test? What is a normal result
Make it vibrate and put it on the mastoid process (bone conduction) and ask them to tell you wen they can’t hear it. Once they say yes lift it into the air outside their ear and ask if they can hear it. They should be able to as air conduction is better
How do you do Weber’ test
Place a vibrating tuning fork on the patients forehead at the midline. Normally they should be able to hear the sound equally in both ears
In sensorineural hearing loss what will happen in Rinne and Weber’s test?
Rinne= normal result Weber's= only normal ear will hear
In conductive hearing loss what will happen in Rinne and Weber’s test?
Rinne= when tuning fork is in ear they will hear it less Weber's= normal ear hears it more
Are CN IX and X sensory or motor?
Both
What are the afferent and efferent components of the gag reflex?
Afferent= cn ix Efferent= cn x
How do you examine for CN IX and X?
Inspect soft palate and uvula
Get them to say ahh and the uvula will deviate away from the affected side (theres also reduced elevation on the effected side)
Ask them if they have any swallowing difficulty, changes in voice or cough
What muscles are effected by CN XI?
SCM and trapezius
How do you test for motor function of CN XI?
Get them to shrug their shoulders against resistance and then to turn against resistance
If you get a person to turn right against resistance what muscle specifically is being tested?
Left SCM
How do you test for CN XII?
Inspect tongue for wasting or fasciculations
Get them to stick their tongue out
What is an abnormal result when testing for CN XII?
Tongue deviates towards the lesion
What is the order of cranial nerves?
Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal
