Cranial Nerve Exam Flashcards
How to test CN I (Olfactory)
- First make sure each nasal passage is patent
- Then ask the patient to close both eyes and occlude on nostril
- The patient will then smell a substance such as coffee
- Then repeat with the other nostril with a different substance
When can loss of smell occur in?
- Head trauma
- Smoking
- Aging
- Cocaine use
- Parkinson’s disease
How to test CN II (optic)
- Test visual acuity
*Rosenbaum (screening device) - Visual fields by confrontation
- Fundoscopic examination
What is the difference between the Snellen chart and the Rosenbaum
S: test for central vision, patient stands 20 feet away
R: test for near vision, done at beside
What does visual fields by confrontation test for?
Peripheral vision
What does a temporal defect in one eye suggest about the other eye?
There is a nasal defect in that eye
What is Anisocoria?
A difference of >0.4mm in the diameter of one pupil compared to the other
How to test for CN III, IV, and VI Oculomotor, Trochlear, Abducens
EOM
What is CN V?
Motor and sensory
What is the motor part of CN V?
temporal and masseter muscle, lateral pterygoid
What is the sensory division of CN V?
- Opthalmic
- Maxillary
- Mandibular
How to test for the motor part of CN V?
- While palpating the temporal and masseter muscles ask the patient to firmly clench the teeth
- Ask patient to open and move jaw from side to side
How to test for CN V sensory?
- Use a cotton ball for light touch and have the patient respond whenever they feel the cotton ball on their skin
- Use a sharp wool splinter and a cotton ball to asses for pain
- Ask the patient if they feel “sharp” or “dull”
*every area that was assessed for dull MUST be assessed with sharp
What would you do if you suspecting sensory loss (CN v)?
1, use temperature sensation
2. Fill two test tubes with hot and ice-cold water
*ask the patient to identify hot or cold
What does flattening of the nasolacrimal fold and drooping of the lower eyelid indicate?
Facial weakness
How to test for CN VII Facial?
Ask the patient to
1. Raise both eyebrows
2. Frown
3. Close eyes as tight as possible so you cannot open them
4. Show both upper and lower teeth
5. Smile
6. Puff out both cheeks
What does a peripheral injury to CN VII affect?
- Upper and lower face
What does a central lesion affect?
Mainly the lower face
What is the component and function of CN I (olfactory)
C: sensory
F: smell
What type of smells should you avoid when testing CN I and why?
- Noxious triggers such as ammonia
*will stimulate pain endings of trigeminal nerve
What is the component and function of CN II?
C: sensory
F: vision
Which CN are involved in light stimulus?
CN II and CN III
What is the component and function of CN III?
C: motor
F: raise upper eyelid, constricts pupils, accommodates the eye
What does near response test?
Pupillary constriction
1. Convergence of medial recuts muscle
2. Accommodations of ciliary muscles of the lens
What does drooping of the upper eyelids suggest?
- CN III palsy
*Horners syndrome
What is the component and function of Trochlear nerve CN IV?
C: motor
F: assisting in turning the eyeball downward and laterally
*SO
What is the component and function of the Abducens nerve CN VI?
C: motor
F: lateral rectus muscle turns eyeball laterally
What is the function of the superior rectus and inferior oblique?
Elevates the eye
What is the function of the medial rectus?
- Adducts when contracts
*pulls eye inward
What is the function of inferior rectus?
Downward gas aided by the superior oblique
What is the function of CN IV (superior oblique)
- Downward, internal rotation of eye
What is the function of CN VI Abducens?
- Lateral deviation of the eye
What does corneal reflex test for?
Sensory: CN V
Motor: CN VII
*if there is a diminished corneal reflex it reflects pathology either of CN V or CN VII
What is the component and function of the mandibular nerve (motor)
C: motor
F: muscle of mastication, mylohyoid, anterior belly of digastric, tensor veli palatine, tensor tympani
What is the component and function of the mandibular nerve? (Sensory)
C: sensory
F: skin of cheek, skin over mandible and side of head, teeth of lower jaw and TMJ, mucous membrane of mouth and anterior part of tongue
What is the function and component of the facial nerve?
C: mixed
FM: muscles of face and scalp, stapedius muscle, posterior belly of digastric, stylohyoid muscles
FS: taste from anterior 2/3 of tongue
What is the component and function of CN VIII?
C: Sensory
Function vestibular: saculae, saccule, semicircular canals, position of head
Function cochlear: Hearing
If there is vertical nystagmus what does that indicate?
A potential underlying pathology
1. Lesions of cerebellum
2. Tumors
3. MS
What is conductive hearing loss due to?
Impaired air through ear transmission
What is sensorineural hearing loss due to?
Damage to cochlear branch
If there is conductive hearing loss, where would the sound lateralize to? (Weber)
Sound is heard to the impaired ear
If there is sensorineural hearing loss where does the sound lateralize to? (Weber)
Sound is heard in the good ear
If there is conductive hearing loss what is greater BC or AC? Rinne
BC=AC or BC>AC
If there is sensorineural hearing loss what is heard longer AC or BC?
AC>BC
What is the function of CN IX?
Sensory and motor
M: pharynx
S: posterior portions of the eardrum and ear canal, pharynx and posterior tongue including taste
What is the function of the vagus nerve?
Motor and sensory
M: palate, pharynx, and larynx
S: pharynx and larynx
*check gag reflex and rise of palate
What is the function and component of CN XI
C: motor
F:
Cranial root
1. Muscles of soft palate (except tensor Veli Palatini)
2. Muscles of pharynx
3. Muscles of larynx
Spinal root
1. Sternocleidomastoid and trapezius muscle
How to test CN XI?
- Assess the movement of the Sternocleidomastoid and upper trapezius
What is the component and function of the hypoglossal nerve?
C: motor
F: muscles of tongue (except Palatoglossus)
If the tongue deviates to the left where is the lesion?
Lesion is on the left (Lower motor neuron lesions)
*deviates to opposite side in upper motor neuron lesions
