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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
what does the olfactory nerve do?
- (CN I)
- transmit signals from nasal cavity
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)
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
the inability to detect ordorants is called?
- can be uni or bilateral
the inability to recognize an ordorant is called?
what information does the optic nerve transmit?
info on visual acuity (central vision) and visual fields (peripheral vision)
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)
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
what are problems in visual acuity called?
can be myopia or hypertropia
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
what are problems with visual fields called?
scotoma, anopsia, and hemianopsia
what does the oculomotor nerve innervate?
- (CN III)
- levator palpebrae (lifts upper eyelid)
- regulates pupilary function and lens shape
what does the trochlear nerve innervate?
- (CN IV)
- the superior oblique muscle of the eye
what does the abducens nerve innervate?
- (CN VI)
- lateral rectus muscle of the eye
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
what is malalignment of the visual axes called?
- heterotropia or starbismus
- can be comitant or noncomitant
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
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)
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
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
how to test trigeminal motor innerv of masseter, temporalis, medial pterygoid?
pt asked to alternately bite hard and relax with mouth and teeth closed
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)
how to test trigeminal motor innerv of mylohyoid muscle?
- push tongue against roof of mouth
- examiners palpates submandibular triangle
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
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
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
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
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
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)
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
what happens if injury to the facial nerve involves corticobulbar projections?
contralateral facial weakness only in mm of lower 1/2 of face
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
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
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)
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
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)
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)
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
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
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
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
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
what are the two types of afferent fibers of the glossopharingeal n.?
visceral and somatic
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
what do somatic afferent fibers of the glossopharingeal n. transmit?
- little or no clinical importance
- tactile info from external ear canal
what does unilateral numbness and absense of a gag response suggest?
a dysfunction of the glossopharingeal nerve
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
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
what happens with unilateral involvement of the vagus n.
- deviation of uvula during phonation
- loss of gag reflex on involved side
what does the accessory nerve innervate?
- (CN XI)
- motor nerve
- innervates SCM and traps - test mm strength and asymmetry of these muscle functions
what does the hypoglossal nerve innervate?
- (CN XII)
- motor nerve
- innerve to intrinsic/extrinsic mm of tongue (most impt for tongue protrusion)
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
what happens with unilateral lesions of the hypoglossal n?
tongue will deviate towards the side of involvement
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