Examination of Cranial Nerves Flashcards
Where is this examination important if we can simply do an MRI instead?
Clinical exam guides which bit to scan, and when comparing the patients functional status to the MRI then you can decide if the MRI lesion is important. You can also decide which lesion is responsible for the problem.
What may you discover on introducing yourself to the patient?
A dysphasia or dysphonia or a decreased conscious level
What may you discover on inspection? (5)
Facial palsy Ptosis Ophthalmoplegia Craniotomy scars PEG/trachy
What is CN IV?
Trochlear
What is CN XII?
Hypoglossal
What is CN VII?
Facial
What is CN IX?
Glossopharyngeal
How do you test the olfactory nerve (CN I)?
“Have you noticed any change in your senses of taste or smell?”
How do you test the optic nerve? What must you remember to do?
Acuity using a Snellen chart or any printed material at the bed side
Test each eye separately!
How do you test the optic nerve if acuity fails?
Finger counting & light discrimination
How do you test the visual fields?
Confrontation – compare the patients fields to your own in quadrants, one eye at a time.
If there is a lesion at the level of the optic nerve, what is the resulting deficit?
Monocular blindless
If there is a lesion at the level of the optic chiasm, what is the resulting deficit?
Bitemporal hemianopia
If there is a lesion at the level of the optic tract, what is the resulting deficit?
Contralateral homonymous hemianopia
What 6 reflexes do you need to test in the eyes?
Direct
Consensual
Accomodation (all in both eyes)
What causes miosis (small pupils)?
Drugs eg Opiates
Horner’s syndrome
Old age
What causes mydriasis (dilated pupils)?
Drugs eg Atropine
Oculomotor palsy
Ocular trauma (irregular)
How many muscles are there that move the eye? Name them and the movement they do.
6 – superior oblique (incycloduction), superior rectus (elevation, adduction), lateral rectus (abduction), medial rectus (adduction), inferior rectus (depression, adduction), inferior oblique (excycloduction)
With the eye abducted, the ______ and ______ move the eye up and down.
With the eye adducted, the _____ and ______ move the eye up and down.
Superior and inferior recti
Superior and inferior obliques
Oculomotor palsy results in…?
A dilated pupil and a depressed, abducted eye.
Which muscle does CN IV innervate?
Trochlear innervates superior oblique
Which muscle does CN VI innervate?
Abducens innervates lateral rectus
How do you assess the trigeminal nerve?
Examine facial sensation to fine touch in all 6 areas (V1, 2, 3 on both sides)
Examine muscles of mastication - “clench your teeth” and “open your mouth”
Examine jaw jerk reflex
How do you assess the facial nerve?
“Raise your eyebrows”
“Screw your eyes tight shut”
“Puff out your cheeks”
“Big smile
Which spares the forehead - a UMN or LMH lesion? Why?
UMN because the forehead area of the facial nucleus is innervated by both motor cortices.
What does the corneal reflex test?
V (ophthalmic devision) & VII - part of brain stem tests
How do you test CN VIII?
Mask one ear with tragal massage and whisper a number into the tested ear, then ask the patient to repeat the number.
Weber and Rinne uses a tuning fork with how many Hz?
512Hz
Weber test asks which question?
In which ear is the sound louder?
Rinne test asks which question?
Which is louder - air or bone conduction?
In a right conductive deafness, which side does Weber localise to? Is the stimulus louder in air or bone?
Localises to right side
Bone stimulus is louder
In a right sensorineural deafness, which side does Weber localise to? Is the stimulus louder in air or bone?
Localises to left side
Air stimulus is louder
How do you test CN IX, X and XI?
Open mouth, say “ah” - uvula will elevate
It deviates away from a bulbar palsy.
Also test the gag reflex.
How do you test CN XI and XII?
“Shrug you shoulders” (tests trapezius)
“Stick out your tongue”
Look for fasciculation and wasting
Deviates towards side of palsy
