Midterm - Cranial Nerve more Flashcards
CN I
Olfactory nerve
Sensory: ability to smell
CN I test
Odor recognition
Amosmia vs hyposmia
Anosmia = complete loss of sense of smell Hyposmia = diminished sense of smell
Loss of smell is commonly (bilateral/unilateral) and due to _____
Bilateral
Chronic rhinitis, fracture to cribiform plate, etc
Anosmia that is a new onset and unilateral is
Most concerning. Suggests possible intracranial mass
Dysosmia/parosmia
Difficulty identifying odors. A CN I problem
*considered idiopathic
Phantosmia
Hallucination of an odor when none present. A CN I problem
*implies a problem in the olfactory cortex
CN II
Optic nerve
Sensory only: vision & afferent portion of pupil constriction
CN II tests
- Visual acuity
- Peripheral vision
- Pupillary light reflexes (affarent portion)
- Visualize optic disc
Primary open angle glaucoma can cause
Globally narrowed visual fields (high pressure in the eye damages the optic nerve)
What is Normal response to light?
And what is direct and consensual response?
Miosis = pupil constriction
Direct response = pupil with the light source constricts
Consensual = constriction fo the pupil in the eye opposite from the light source
How does light coming in one eye constrict both pupils?
Light come in one eye, travel along CN II which synapses with CN III. CN III generates efferent motor response bilaterally, causing pupil constriction
CN III
Oculomotor nerve. Efferent motor.
Innervates the levator palpebrea superioris muscle which causes eyelid elevation
Controls 4/6 muscles involved in moving the eye: inferior oblique, inferior superior and medial rectus
CN III tests
- Pupillary light reflex - motor component of pupil constriction
- Check for intact eyelid elevation
- Assess cardinal fields of gaze (evaluates CN III, IV, VI)
- also corneal light reflection & cover/ uncover tests for strabismus - Accommodation
Abnormal CN III function
Droopy eyelid (ptosis)
Dysconjugate gaze
Eyes that don’t move in parallel
Usually indicates paresis (weakness) or paralysis of extra-ocular muscles
End point nystagmus is ______ whereas involuntary nystagmus through the cardinal fields of gaze is ______
Normal, abnormal
Lateral rectus m is innervated by ____ and does _____
CN VI, eye abduction
Superior oblique is innervated by ____ and does ____
CN IV, moves eyes down and in
Signs of complete right CN III palsy
Dilated pupil (mydriasis), ptosis, can’t move the R eye medically
A patient with disconjugate gaze will complain of ________ and tends to occur in the direction (of/ opposite) the dysconjugate gaze
Double vision (diplopia), in direction of dysconjugate gaze
Asymmetric corneal reflections indicates _____
Strabismus = deviation of normal ocular alignment
aka heterotropia
The cover/ uncover test assesses for ____
Phoria (latent strabismus)
- patient looks straight ahead with both eyes, cover one eye, the covered eye will deviate when not in use, the eye moves back to center when you uncover it
In Accommodation (aka convergence), the eyes should both move inward together until about ___ inches from the bridge of the most and pupils should _____
5 inches, constrict
What is the accommodation triad? Aka near reflex
- The eyes should converge (CN III)
- The pupils should constrict (CN III)
- Lenses should change shape (not visible to examiner - parasympathetic innervation)
Cranial nerve palsies are often cause by intracranial problems such as
- cerebral vascular accidents
- tumors
- trauma
- multiple sclerosis
- infection
- migraines
Can be congenital
CN V
Trigeminal nerve
Sensory and motor innervation
Muscles of mastication
CN V tests
- bite the stick
- light touch and pain sensation
- corneal reflex (blink reflex)
Where do V1, V2 and V3 have sensory innervation?
V1 (ophthalmic) - forehead and top of nose)
V2 (maxillary) - bottom of nose, upper lip, zygomatic process
V3 (mandibular) - anterior to ear, lateral mandible and chin/bottom lip
What is Trigeminal neuralgia/neuropathy aka Tic Doulourex?
peak onset?
Pain characteristics?
Trigger zones
Causes
Management
Facial pain in the trigeminal distribution between maxi alley and mandibular branch
60-70
- sharp, lancinating,
- lips, gums, cheek or chin
- unilateral
- paroxysmal
- seconds to minutes
Trigger zones
- small areas in the region of the nose and mouth (possibly brushing teeth, chewing, cold exposure)
- idiopathic, sometimes from contact/compression by other structures (superior cerebellar artery, multiple sclerosis plaques, tumor)
- MRI, referral to neurologist, medication (anti-seizure)
Corneal reflex (blink reflex) tests the ___ part of CN V and CN ____ controls eyelid closure.
What is Normal/abnormal response
CN V1 (ophthalmic branch)
CN VII controls orbicularis oculi muscles for lid closure
Normal: light touch to cornea (CN V) causes both eyes to blink (CN VII)
Abnormal: absent blink in either or both eyes
CN VII
Facial nerve
Motor and sensory functions
Facial expression, taste, corneal reflex
CN VII facial expression abnormalities can be due to peripheral nerve lesion (LMN) such as _____ and central lesion (UMN) such as ____
Bell’s palsy
Stroke or tumor
Forehead/eyebrows have (unilateral/bilateral) UMN and (unilateral/bilateral) LMN innervation
An injury to CN VII LMN will cause loss function of the (upper/lower/both) divisions of the face? This is known as ______
Bilateral UMN, unilateral LMN
Both = bell’s palsy
- sudden onset, one-sided facial paresis/paralysis but no loss of facial sensation (exception: taste)
- unable to raise eyebrow/wrinkle the forehead
- can’t fully close the eye
- loss of Nash-labial folds
- drooping of the corner of the mouth
- trouble with lip sounds B,P and M
CN VII Bell Palsy
What are risk factors for Bell Palsy? What are the causes?
Diabetes, pregnancy, history of Herpes Simplex Virus (HSV) or Varicella Zoster Virus (VZV)
Idiopathic, possibly virally-mediated
What is the management and prognosis of bell palsy?
- eye drops/temporary patch
- refer to PCP for co-management
Urgent but not an emergency, corticosteroids +/- antivirals
Most often resolves over 3-6 weeks
UMN lesion of CN VII (will/ will not) spare the forehead?
Will spare the forehead but the contralateral lower face will have deficits
What part of the tongue does CN VII innervate?
Sensory (taste) to the anterior 2/3 of the tongue
CN VIII
Auditory nerve
2 divisions (vestibular and cochlear)
Both sensory
How do you test the cochlear division of CN VIII?
Whisper test
*if the patient fails, perform the Weber and Rinne tests to asses for conductive vs sensorineural hearing loss
What is conductive hearing loss?
External sound waves from the air are not able to gain access to the inner ear
Due to trauma, infection, inflammation, foreign body, cerumen buildup, etc. in the outer or middle ear
What is sensorineural hearing loss?
Caused by damage to the inner ear or the cochlear branch of CN VIII
Ex: aging and acoustic neuroma
In Webber’s test, sound will lateralize to the _____ side in conductive hearing loss or the ______ side in sensorineural hearing loss
Affected, unaffected
Abnormal rinne test results for conductive and sensorineural hearing loss
Conductive: Bone conduction (BC) > air conduction (AC)
Sensorineural: AC>BC in affected ear but diminished compared to normal
CN IX and CN X
Glossopharyngeal & Vagus
Both have motor and sensory functions
CN IX and CN X tests
“Say ahhh”
Gag reflex
Observe patients ability to speak clearly
Check the oropharynx: uvula midline, upward movement of soft palate is symmetrical, gag reflex intact and symmetrical
What part of the tongue does CN IX innervate?
Sensory to the posterior 1/3 of the tongue
CN XI
Spinal accessory nerve
Motor: trapezius and SCM muscles
CN XII
Hypoglossal nerve
Motor: tongue movement
CN XII tests
- stick out your tongue and move side to side
- say L, D, T and N
When there is an issue with one side of the hyppoglossal nerve, the tongue will deviate (toward/away from) the side of lesion
Toward
*the functioning side will dominate
