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list all the cranial nerves
- I: olfactory nerve
- II: optic nerve
- III: ocular motor nerve
- IV: trochlear nerve
- V: trigeminal nerve
- VI: abducens nerve
- VII: facial nerve
- VIII: vestibulocochlear nerve
- IX: glossopharingeal nerve
- X: vegus nerve
- XI: accessory nerve
- XII: hypoglossal nerve
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what does the olfactory nerve do?
- (CN I)
- transmit signals from nasal cavity
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how is the olfactory nerve tested?
- presenting non-noxious odorants separately to each nostril
- person occludes one nostril and is asked if smells something (after visual inspection for obstructions)
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why shouldn't volitale chemicals like ammonia be used when testing the olfactory nerve?
bc they produce reactions mediated by trigeminal nerve that signals injury
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the inability to detect ordorants is called?
- anosmia
- can be uni or bilateral
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the inability to recognize an ordorant is called?
olfactory agnosia
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what information does the optic nerve transmit?
info on visual acuity (central vision) and visual fields (peripheral vision)
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how is the optic nerve tested?
- by testing visual acuity and visual fields separately
- impt ot inspec the eyes and eyelids for assymetrics (ptosis or exophthalmos)
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how is visual acuity tested?
- in each eye separately
- pt covers one eye and reads letters or numbers 20ft away and on pocket sized card held 14" away
- normal vision is 20/20 if person can read what is expected at 20 ft
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what are problems in visual acuity called?
can be myopia or hypertropia
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what is the simplest method for testing someone's visual field?
- confrontation test
- pt covers one eye and looks directly at examiners nose
- examiner presents a static visual stim to each of the four diagonal vis quadrants
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what are problems with visual fields called?
scotoma, anopsia, and hemianopsia
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what does the oculomotor nerve innervate?
- (CN III)
- levator palpebrae (lifts upper eyelid)
- regulates pupilary function and lens shape
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what does the trochlear nerve innervate?
- (CN IV)
- the superior oblique muscle of the eye
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what does the abducens nerve innervate?
- (CN VI)
- lateral rectus muscle of the eye
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how to examine the oculomotor, trochlear, abducens
- examines ocular motility
- starts w/ observation of the eye's axis when looking straight ahead at distant object
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what is malalignment of the visual axes called?
- heterotropia or starbismus
- can be comitant or noncomitant
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what does the trigeminal nerve innervate?
- mixed nerve w/ 3 divisions: opthalmic, maxillary, and mandibular
- sensory innerv on face and eye
- motoric: muscles of mastication, mylohyoid, ant digastric, m. tensor tympani
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how to test sensory stimuli with the trigeminal nerve?
- 1. use sharp or blunt pressure on forehead
- 2. use test tubes filled with warm/cold water
- 3. corneal reflex test (trigeminal sensory, facial motor)
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how to test trigeminal using test tubes of water
two tubes of same temp are placed simultaneously in similiar locations on either side of the face -- discrepancies if the temp feels stronger on one side vs the other
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how to test trigeminal nerve with the corneal reflex?
- if opthalmic part damaged: no response seen in either eye after corna touchd by wisp of cotton
- if facial n. part damaged: no repsonse seen on the lesion side when touched
- blink response on the nonlesion side will be present regardless of which cornea is touched
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how to test trigeminal motor innerv of masseter, temporalis, medial pterygoid?
pt asked to alternately bite hard and relax with mouth and teeth closed
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how to test trigeminal motor innerv of lateral pterygoid?
pt asked to push the jaw forward w/ mouth slightly open (any deviation should be noted)
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how to test trigeminal motor innerv of mylohyoid muscle?
- push tongue against roof of mouth
- examiners palpates submandibular triangle
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what does the facial nerve innervate?
- (CN VII)
- mixed cranial nerve
- motor: muscles of facial expression, platysma, post digastric, stylohyoid, stapedius
- sensory: transmits taste from anterior 2/3 of tongue and general senstation from oropharyngeal mucosa and skin in external ear canal
- autonomic: lacrimal gland, submandibular and submaxillary salivary glands and nasal mucosa glands
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how to examine motor innerv of facial nerve?
- facial expression capability w/ attention to lower eyelids, nasolabila folds, and mouth corners
- -- wrinkle forhead w/ head straight and eyes looking up
- -- close eyes forcefully
- -- purse lips
- -- smile widely showing teeth
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what happens in pt motor function w/ facial nerve dysfunction?
- eyebrow on invovled side may not rise and winkles appear on that side
- approximation of upper and lower eyelids will be incomplete and sclera below the iris wil be seen btwn the eyelids
- corner of the mouth on the involved side will not move laterally, smile is asymmetric
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how to test taste functionality of facial nerve?
- ant 2/3 of tongue
- apply dilute solutions of glucose, NaCl, citric acid and quinine to either side of tongue separately
- pt points to the word indicating the taste
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what happens to taste if the facial nerve is damanged?
person may point to the word water when one of the test subjects is applied to tongue
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what is the most common site of injury of the facial nerve and what results?
- stylomastoid foramen as the nerve exits the skull
- paralysis of the facial muscles on ipsilateral side of the face (Bell's Palsy)
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what happens if facial nerve is injured proximal to the origin of the chorda tympani?
ageusia (absense of taste) in addition to weakness or paralysis of facial muscles
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what happens if injury to the facial nerve involves corticobulbar projections?
contralateral facial weakness only in mm of lower 1/2 of face
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what are the components of the vestibulocochlear nerve?
- (CN VIII)
- 1. cochlear: audition and hearing
- 2. vestibular: equilibrium, monitoring position and orientation of the head
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how to test the audition functionality of the vestibulocochlear nerve?
- simple test: rubbing noise applied lateral to the ear
- -- further tests needed if pt performs poorly
- Rinne's test
- Weber's test
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what is Rinne's test
- used to test audition functionality of vestibulocochlear nerve place tuning fork against mastoid process, when tone no longer heard,
- the tuning fork is then brought to ext aud meatus and pt is asked if they hear a noise (normally it will be heard and for twice as long at
- the ext aud meatus)
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what is Weber's test?
- place the tuning fork on vertex of the skull or in center of forehead
- pt indicates on which side (if either) the tone is louder
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what are the results of Weber's test if the pt has unilateral sensorineural hearing loss?
- (prob with vestibulocochlear n)
- tone is louder in the normal ear (tone is lateralized to the good ear)
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what are the results of Weber's test if the pt has unilateral conduction deafness?
- (prob with vestibulocochlear n)
- tone is louder on the diseased side (tone is lateralized to the bad ear)
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what does the vestibular division of the vestibulocochlear nerve transmit?
impulses from the receptors responding to rotational (semicircular canals) and linear (utricle and saccule) movements of the head
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how to test the vestibular division of the vestibulocochlear nerve?
- simple tests performed as part of routine neurological exams
- -- alt touch nose and reach for examiners finger 3-4 times w/ eyes open and then eyes closed
- -- march in place w/ eyes open and closed
- careful function evaluated only when vestibular or cerebellar dysfunction is suspected
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what happens w/ pt having unilarteral reduced vestibular input?
- problem with vestibulocochlear n.
- will drift away from the examiner's finger toward the side of the vestibular disease
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what happens w/ pt having vestibular disease when they march in place with eyes open and then closed?
will rotate to one side when eyes are closed
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what does the glossopharingeal nerve innervate?
- (CN IX)
- mixed nerve
- innervaties stylopharingeal mm and parotid gland
- leave the skull through the jugular foramen and synapse w/ otic ganglion
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what are the two types of afferent fibers of the glossopharingeal n.?
visceral and somatic
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what do visceral afferent fibers of the glossopharingeal n. transmit?
- sensations from pharyngeal mucosa, taste from post 1/3 of tongue, impulses from baroreceptors in the carotid sinus
- terminates in nucleus solitarus
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what do somatic afferent fibers of the glossopharingeal n. transmit?
- little or no clinical importance
- tactile info from external ear canal
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what does unilateral numbness and absense of a gag response suggest?
a dysfunction of the glossopharingeal nerve
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what does the vagus nerve transmit?
- (CN X)
- mixed nerve
- sensory fibers: mostly transmitting info from thoracic and abdominal visceral structures, chemoreceptors of the carotid body, and taste receptors on epiglottis
- motor fibers: innerv mm of soft palate, pharyngeal constrictors, intrinsic/extrinsic mm of larynx
- parasympathetic innerv of abdominal smooth mm and glands
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what are the two tests of vagal function?
- observation of uvula and soft palate when pt says "ahhhh"
- gag reflex when touching lateral wall of pharynx wall
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what happens with unilateral involvement of the vagus n.
- deviation of uvula during phonation
- loss of gag reflex on involved side
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what does the accessory nerve innervate?
- (CN XI)
- motor nerve
- C1-C4
- innervates SCM and traps - test mm strength and asymmetry of these muscle functions
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what does the hypoglossal nerve innervate?
- (CN XII)
- motor nerve
- innerve to intrinsic/extrinsic mm of tongue (most impt for tongue protrusion)
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how to test the hypoglossal nerve?
- observe tonge resting in mouth - mass and contour
- pt asked to protrude the tongue or push it into the cheek, tongue remains in midline
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what happens with unilateral lesions of the hypoglossal n?
tongue will deviate towards the side of involvement
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