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Cranial Nrvs
| Question | Answer |
|---|---|
| Name the structures that exit through or enter the foramen magnum. | medulla and meninges, spinal accessory nerve, vertebral arteries, anterior and posterior spinal arteries |
| Name the structures that exit through or enter the jugular foramen. | CN IX, X and XI |
| Name the structures that exit through or enter the internal acoustic meatus. | CN VII and VIII |
| Name the structure(s) that exit through or enter the foramen ovale. | V3 of trigeminal nerve |
| Name the structure(s) that exit through or enter the foramen lacerum. | internal cartoid arteries |
| Name the structure(s) that exit through or enter the foramen rotundum. | V2 of trigeminal nerve |
| Name the structures that exit through or enter the superior orbital fissure. | CN III, IV, VI and V1 of trigeminal nerve |
| Where do the olfactory nerves enter the cranium? | cribriform plate of the ethmoid bone |
| What muscle is most efficient at elevating the globe when it is in line 23 degrees lateral to the straight-ahead position of the eye? | superior rectus |
| What muscle is most responsible for depressing the globe while it is abducted? | inferior rectus |
| Name the extraocular muscles that cause intorsion. | superior rectus and superior oblique |
| Name the extraocular muscles that cause extorsion. | inferior rectus and inferior oblique |
| What extraocular muscle is most efficient as a depressor when the eye is adducted? | superior oblique |
| What extraocular muscle is most efficient as an elevator when the eye is adducted? | inferior oblique |
| Which of the inferior named extraocular muscles is most inferior? | inferior oblique |
| What extraocular muscles in each eye does a physician test when he asks the patient to look to the pt's right and down? | inferior rectus in the R eye and superior oblique in the L eye |
| What will the globe do if the SO muscle is activated while a patient's eye is abducted? | intorsion |
| What will the globe do if the IO muscle is activated while a patient's eye is abducted? | extorsion |
| What is a tertiary action of the SO muscle when the globe is extorted and depressed? | abduction |
| If a pt presented with a lesion of the right 6th CN, what problem might she have? | unable to look to the right with the right eye when eyes are looking straight forward |
| If a pt presented with a lesion of the right 6th CN and its nucleus, what problem might he have? | gaze palsy - left MR muscle would move the eye laterally, but very slowly. The LR on the right wouldn't move at all. |
| If a pt is acutely having a stroke in the lower left midbrain at the level of the trochlear nucleus and site of nerve exit, what might her physician see on the EOM exam? | R eye elevated and extorted |
| Identify the muscle producing: pure vertical up movement of the eye when it is positioned 51 deg toward the nose (adducted). | inferior oblique |
| Identify the muscle producing: pure down movement of the eye when it is rotated 23 deg outward. | inferior rectus |
| Identify the muscle producing: pure intorsion with the eye positioned 39 deg away the nose. | superior oblique |
| Besides the EOM, what else do the motor fibers of CN III directly innervate? | levator palpebrae superioris muscle |
| The loss of ability to accomodate with age is called? | presbyopia |
| If while testing a pt's ability to accomodate, you notice the globes do not converge, what is a probable diagnosis you might be thinking about? | midbrain stroke or any type of lesion that would affect the bilat oculomotor nuclei; impingement of CN IIIs as they exit interpeduncular fossa |
| What is the etiology of the so-called "down and out" eye positioning? | CN III/nucleus damage |
| What might a physician see on EOM exam if a pt has a severed R CN III? | the affected eye will be abducted, depressed and slightly intorted |
| Describe the manifestations of Horner's syndrome. | unilateral sx on affected side: mild ptosis of both upper and lower eyelids coupled with a miosis and anhidrosis of upper half of face |
| What might an astute triage nurse be looking for if she suspects the pt has a R sided CN III parasympathetic nerve problem? | R sided mydriasis and moderate to severe ptosis of R eyelid |
| My ciliary muscles are relaxed because I'm giving my Edinger-Westphal nucleus a break. Which activity will be the easiest for me - reading the newest JAMA issue or spotting a bird across the street? | Spotting a bird across the street - relaxed ciliary muscles mean flattened lens, which is best for distance sight |
| If CN III signs are seen on the R side but not the left, would the lesion more likely involve the nuclei of CN III or the nerve itself? | Nerve itself; one nucleus complex feeds parasympathetics to both sides and their close proximity makes it hard to obliterate just one |
| Define strabismus. | misalignment of gaze due to deviation of a globe |
| What tract is just ventral to the trochlear nucleus in brainstem cross-section? | MLF |
| Which CN is most susceptible to damage after a head injury due to its unorthodox and circuitous route to its target? | trochlear nerve |
| Which nerve is the only one to exit the brainstem dorsally and decussate before reaching its target muscle? | CN IV |
| Following a lesion of the R fourth CN tract, how would the R eye be positioned? | normally |
| Following a lesion of the R fourth CN nucleus, how would the L eye be positioned? | extorted and elevated, causing diplopia |
| A pt with left CN IV damage presents to your office holding her head in a tilted position to ameliorate her diplopia. How is her head positioned? | Head tilted to the R to offset the induced extorsion and held with chin downwards to elevate the normal eye to the level the affected eye is abnormally elevated to |
| Monocular diplopia is due to... | cornea, vitreous humor, retina or anterior eye problem |
| Binocular diplopia is due to... | a neurologic issue |
| 3 year-old Trinity is mimicking Nemo on TV and tilts to follow the screen. If she rolls her head to the R, what do her eyes naturally do? | Both eyes roll to the left = intorted R eye and extorted L eye |
| What muscle's paralysis would result in esotropia? | inward maintenance of eye is due to LR paralysis |
| What is the L abducens nucleus responsible for innervating? | ipsilateral LR and contralateral MR |
| What sx are typical of "1-and-a-half syndrome?" | unilateral abducens and MLF lesion cause only contralateral LR to be functional |
| What is typically the cause of bilateral internuclear ophthalmoplegia (INO) in a young pt? | multiple sclerosis (MS) |
| Name the tract that allows the R abducens nucleus to control both the R LR muscle and the L MR muscle. | MLF (in this case via L CN III nucleus) |
| Explain the mechanism behind internuclear ophthalmoplegia. | If the L MLF was lesioned, the R CN VI nucleus could move the R LR successfully, but not the L MR. Moving a finger from far to near to test convergence of the globes would rule out a L MR paralysis. |
| List the 3 nuclei associated with CN VII. | salivatory, nucleus solitarius and facial motor nucleus |
| What might a physician expect to see if her pt has a LR muscle paralysis? | the eye would be deviated medially |
| What is the purpose of the paramedial pontine reticular formation (PPRF)? | It allows for smooth voluntary eye movement during lateral gaze by innervating the abducens nucleus ipsilaterally and sending fibers that travel in the MLF to the oculomotor nucleus contralaterally |
| Where is the PPRF located in a braintem cross-section? | Just ventral to the MLF at levels of III, IV and V and in similar place at levels of VI and VII |
| Which Brodmann's area includes the frontal eye fields (FEF)? | Brodmann's area 8 |
| Define saccadic eye movements. | rapid movement of eye under conscious control to allow abrupt change of point of fixation |
| What Brodmann's areas include the extrastriate visual cortex? | areas 18-19 |
| 3 structures that are important for saccadic eye movements | ipsi superior colliculus, ipsi frontal eye fields and contra PPRF |
| How do the pretectal nuclei communicate with each other? | through the posterior commissure |
| True/False: One test for an intact lateral geniculate nucleus with fully functioning synapses is the swinging light test. | false |
| Fibers coming from the retina traveling in the optic tract eventually reach the pretectal nuclei via what structure? | brachium of the superior colliculus |
| What functions comprise the "near triad?" | convergence of the eyes, rounding of both lenses and constriction of the pupils |
| What CNS infection produces an Argyll-Robertson pupil? | syphilis |
| Explain the mechanism given in the syllabus for an Argyll-Robertson pupil. | syphilis likely selectively attacks the fibers that enter the E-W nucleus ventromedially; these fibers are only responsible for destroying light reflex fibers. Near triad fibers are ventrolateral and thus spared. |
| Argyll-Robertson pupil | Accommodation Retained |
| Explain the path of neuronal activity needed to elicit mydriasis. | retina - hypothalamus - reticular formation - down to C8-T2 preganglionic neurons in IML column - up sympathetic chain - superior cervical ganglion - carotid plexus - cavernous sinus - pupil |
| What ocular exam abnormalities might one expect to see in a pt with an advanced and invasive apical lung tumor? | obliteration of sympathetic fibers feeding the affected side's eye - Horner's syndrome sx |
| True/False: Both autonomic nerves affecting pupillary size make synaptic connections in the ciliary ganglion. | False: only para synapses, symp just rides through the ganglion |
| Eye exam findings: direct light into the R eye shows sluggish pupillary response, direct light into the L causes a brisk constriction of the R pupil. IMMEDIATELY after, direct light in the R pupil shows no constriction, but a steady dilation. Condition? | Afferent pupillary defect (APD) caused by optic neuritis or demyelinating syndromes like MS |
| Which trigeminal nucleus is closest to the MLF in a pontine cross-section? | motor is always medial |
| What structure from the medulla merges with the dorsal horn of the spinal cord? | spinal nucleus of CN V is contiguous with substantia gelatinosa as far down as C6 |
| Name all the cranial nerves that provide sensation to the external ear. | CN V, VII, IX and X |
| Identify the relationship btwn the mesencephalic nucleus of CN V and the EOMs. | EOMs have sensory receptors that originate in mes. nucleus of trigeminal that relay to CN III, IV and VI to control eye movements |
| Where are the cell bodies of neurons which provide information about the amount of tension in the masseter muscle? | mesencephalic nucleus of CN V |
| What is the innervation of the muscle that attaches to the malleus? | nerve from motor nucleus of trigeminal |
| What reflex and CN is a young physician testing when he takes a wisp of cotton and touches a pt's eye? | corneal reflex, chief sensory nucleus of trigeminal and its peripheral afferent through V1 |
| How will the jaw of a pt who has a L sided trigeminal motor nerve injury be situated? | the jaw will be towards the L; the L. lateral pterygoid moves the jaw to the R. Therefore, the strong R. lateral pterygoid will move jaw to same side as lesion |
| If the nerve going to ocular muscles on the R is severed and a physician takes a wisp of cotton to touch the R cornea, what should she see the pt do? | the pt would feel the cotton but blink only on the L side |
| What CN must be intact in order to send signals to the brain that one has just inhaled ammonia? | nasal mucosa sensation and nociceptors - CN V |
| Name the condition arising from lesions to the motor nucleus or root of CN VII. | Bell's palsy |
| The facial motor nucleus is divided into dorsal and ventral portions; what does each innervate? | dorsal - lower face ventral - upper face |
| One or both of these CNs could be involved in hyperacusis. | CN VII - stapedius CN V - tensor tympani |
| The ventral portion of the facial motor nucleus receives (unilateral/bilateral) innervation from the motor cortex. | bilateral |
| How might one tell the difference btwn Bell's palsy or an acute ischemic stroke of the cerebral motor hemicortex? | Bell's palsy affects the nerve after it leaves the facial motor nucleus and thus an entire side of the face. Stroke will cause a total lower face paresis but just weakness of the upper face. |
| What is the name for palpebral fissure diminishment? | lagophthalmos |
| An UMN lesion in the motor cortex in the facial region would cause what else in addition to facial muscle paralysis in the contralateral lower face? | CONTRALATERAL(?) hyperacusis |
| What do nerve fibers from the superior salivatory nucleus innervate? | lacrimal, submandibular and sublingual glands |
| What is the most easily detectable symptom of a lesion of the division of the facial nerve that arose from the salivatory nucleus? | dry eye on the same side as the lesion |
| What are the CNs involved in swallowing? | CN IX, X, XI (bulbar), and XII |
| Where do fibers innervating the parotid gland originate (what nucleus)? | inferior salivatory nucleus |
| In which direction will the palate deviate in a pt with a glossopharyngeal lower motor nerve lesion? | to the unaffected side |
| A pt comes to you for uncontrolled BP. You test her CNs and notice her palate deviates to the right. What might this tell you? | Nothing necessarily, although CN IX brings info from carotid sinus, unilateral 9th nerve deficits should not make a detectable deficit in BP |
| What comprises the gustatory nucleus? | the portion of the nucleus solitarius receiving afferents via CNs VII and IX |
| If an 84 yr old woman can press her tongue into her R cheek, what is your conclusion about her neuromuscular status? | R cerebral cortex, L hypoglossal nucleus and L CN XII are all intact |
| What section of the brainstem is the hypoglossal nucleus within? | medullary tegmentum |
| What nerve rootlets supply the SCM and trapezius? | C1-2 for SCM C3-4 for trapezius |
| What CN nucleus must be intact to elecit a negative chronotropic effect on the heart? | vagus nerve coming from dorsal motor nucleus |
| Which CN provides the most extensive sensory supply to the pharynx? | glossopharyngeal |
| Which CN(s) innervate the pharyngeal constrictors? | CN X and XI |
| What is the neurologic etiology of dysarthria? | any interruption of CN X innervating laryngeal muscles |
| What else provides motor innervation to the pharynx and larynx besides CN X? | bulbar portion of CN XI |
| True/False: Unilateral lesions of the nucleus ambiguus will not produce detectable alterations of the voice. | false |
| Trace the pathway for saccadic eye movements beginning with the retina. | retina -- optic nerve -- optic tract -- lat. geniculate nucleus -- optic radiations -- primary visual cortex -- supp. motor cortex/FEF -- opposite, contralat. PPRF for horiz. eye movements |
| Input from what 2 structures is needed for initiation and accurate targeting of saccadic eye movements? | frontal eye field (Brodmann's area 8) and superior colliculus |
| Smooth pursuit eye movements require input from what cortical structures for initiation and accurate guidance of eyes to track visual targets? | visual cortex and extrastriate visual cortex (Brodmann 18-19) |
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sirprakes
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