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62 Cards in this Set
- Front
- Back
Cranial nerve symptoms are often coupled with damage to what? (2)
Why? |
Long sensory or motor tracts
Cranial nerve exit is near these systems |
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Where can the lesion be localized if the cranial nerve and the long tract signs are associated?
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Brainstem
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Where can the lesion be localized if the cranial nerve symptoms are present but the long tract symptoms are not?
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Damage may be to a more anatomically restricted area or peripheral course of cranial nerve
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If there is motor/sensory symptoms without evidence of cranial nerve signs, what area can you rule out as a source of the lesion?
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Brainstem
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How is the line of insertion of the superior/inferior rectus positioned?
When does it work most efficiently? |
Attaches at an angle 23 degrees lateral to straight ahead
Works when eye is 23 degrees abducted |
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What are 2 movements produced by the superior rectus?
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1. elevate globe in abduction
2. intorsion |
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What are 2 movements produced by the inferior rectus?
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1. move globe down when abducted
2. extorsion |
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How are the attachments of the superior/inferior obliques positioned?
What action do they mediate? |
Angle 51 degrees medial to straight ahead
Raise/Depresses globe when adducted |
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What does the superior oblique do when the eye is abducted 39 degrees?
Inferior oblique? |
Oblique is perpendicular to antero-posterior axis --> complete intorsion
Complete extorsion |
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Which way will the eye deviate if CN III is damaged?
Which direction will there be paralysis? |
Down (with some intorsion) and out because of SO and LR unopposed --> double vision (diplopia)
MR paralysis |
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What three muscles besides the extrinsic eye muscles are innervated by CN III? What are their nuclei and functions?
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Levator palpebrae superioris - cheif oculomotor nucleus - lifts eyelid
Sphincter of iris - EW nucleus - constrict pupil Ciliary muscle - EW nucleus - reduces tension on lens for accomodation |
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What are 2 causes of ptosis?
How do the two compare? |
1. Lesion of CN3 --> no levator palpebrae superioris
2. Interruption of sympathetic fibers that innervate tarsal muscle Lesion of CN 3 causes much bigger ptosis |
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What is the effect of a lesion to CN 3 on pupil size?
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Causes dilated pupil (mydriasis) because no sphincter muscle innervation anymore
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What is strabismus?
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Chronic deviation of eye 'down and out' due to CN 3 lesion
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What is diplopia?
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Double vision caused by CN 3 lesion --> strabismus
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What is the path of fibers from CN 4?
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They loop dorsally and caudally around central gray, cross to other side, and leave brainstem dorsally
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What does CN4 innervate?
Action? |
Contralateral SO
Depress, intort |
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What will happen after a lesion to CN 4?
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Affected eye will deviate up, chronically extort --> diplopia
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What does CN 6 innervate?
What does it do? |
LR
Moves eye laterally |
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What happens in a lesion to CN 6?
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Ipsilateral eye deviates medially
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What is smooth pursuit?
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When the cerebral cortex initiates conjugate lateral deviation of the eyes as a reflex response to visual stimuli
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What is sacchades?
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Conscious deviation of the eyes
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How do fibers travel to allow for coordinated movement of the eye?
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Cerebral cortex --> PPRF (pons) --> ipsilateral CN6 nucleus (for LR) and up the contralateral MLF for CN3 nucleus of other eye (for MR)
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How will the eyes move with input to the right paramedian nucleus?
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Both eyes will rotate to the right
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What would be the result if a lesion spared the nuclei of CN 6, but involved the MLFs between CN 3 and CN6?
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Neither eye would deviate, but neither eye would move medially when patient is asked to make coordinated lateral eye movements
Eyes can still move medially to focus on a near object |
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What is internuclear opthalmoplegia?
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Lesion in MLF between CN 3 and CN 6
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Why are eye movement problems usually bilateral?
What can be inferred if all the eye muscles are affected by a lesion? |
Because of the close proximity of CNs 3, 4, 6, and MLF
Lesion is probably peripheral, where CNs 3, 4, and 6 run together |
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What are saccadic movements and what do they require?
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Rapid, conscious movements of the eye allowing one to abruptly change the point of fixation
Requires input from frontal eye field and superior colliculus --> contralateral PPRF --> initiate horizontal eye movements |
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What is smooth pursuit and what does it require?
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Slow tracking movements that allow you to keep a specific object or stimulus in your central vision
Input from visual cortex and extrastriate visual cortex --> PPRF |
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What is a midbrain area receiving visual afferents?
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Pretectal area (rostral to the superior colliculi)
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Pretectal area of midbrain
a. input b. output |
a. Receive light input from retinas and contralateral pretectal nucleus via posterior commissure
b. Main occulomotor nuclei, Ipsi- and contralateral EW nuclei --> ciliar ganglion --> pupillary sphincter and ciliary muscle |
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What is the pathway for the light reflex?
Lens accomodation? |
pretectal nuclei --> EW --> ciliary --> pupillary constrictor
pretectal nuclei --> EW --> ciliary --> ciliary muscle |
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What is the direct light reflex?
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Constriction of the pupil of the illuminated eye
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What is the consensual light reflex?
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Constriction of the pupil in response to illumination of the other eye
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What is the near triad?
What are its 3 components? |
Stimulated by a near object, allows for near vision
1. Convergence of eyes (bilat. contraction of MR) 2. Rounding of lens (ciliary muscle) 3. Constriction of pupil |
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What is the pathway that leads from unfocused, close object to the near triad response?
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Unfocussed object --> blurred image to visual cortex via retino-calacrine pathway --> to brainstem in occipitomesencephalic tract --> synapse of EW and occulomotor nucleus
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What is Argyll-Robertson pupil?
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Small pupil that is unresponsive to bright light, but does constrict during near triad
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What is the pathway of sympathetic fibers that dilate the pupil?
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Hypothalamus --> descend through brainstem and cervical cord --> synapse in interomediolateral cell column --> exit cord in lower cervical roots --> ascend w/ carotid plexus --> pupil
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What happens if the sympathetic flow to the pupil is disrupted?
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Pupil under less tonic sympathetic input, will be relatively constricted or miotic
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What other functions to the face and eye travel in the sympathetic pathway? (2)
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Sweating over upper 1/2 of face (sudomotor)
Motor input to the eyelid of Muller's muscle |
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What happens if sympathetic flow to the face is disrupted? (3)
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1. Decreased size of pupil on side of lesion (miosis)
2. Droopy eyelid (ptosis) 3. Decreased sweating on the same side of the face (Horner's syndrome) |
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What are the somatosensory areas innervated by CN 5?
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Front of face, external ear
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Which cranial nerves innervate the external ear?
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CN 7, 9, 10, and 5
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What types of fibers have their origin in the Mesencephalic nucleus of CN 5?
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proprioceptive fibers from joint capsules of jaw, muscles of mastication, teeth
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What is the mesencephalic root of CN V? Where does it lead?
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Dendrites and axons of primary afferents, leads to the motor nucleus of CN V for reflex control of chewing
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To what structures does the spinal nucleus of V fuse?
What does it carry? |
rostrally with chief sensory, caudally with dorsal horn of cervical spinal cord
Carries pain and temperature from the face |
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What does the motor nucleus of V send out?
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Efferents to Muscles of mastication, tensor tympani
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To where does CN7 send efferents?
What are the divisions? |
Muscles of facial expression, including orbicularis oculi
Dorsal supplies lower face Ventral supplies upper face |
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How does innervation of the ventral and dorsal divisions of CN 7 motor nucleus differ?
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Ventral = receives bilateral input from the cortex
Dorsal = receives contralateral input from the cortex |
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What happens in an upper motor neuron lesion in facial nerves?
Lower motor neuron? |
Upper motor lesion --> affects facial muscles on lower portion of face
Lower motor lesion --> affects both sides of face |
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What results from a lesion involving the nucleus of CN 7?
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Bell's Palsy = flaccid paralysis of facial muscles, inability to close ipsilateral eyelid, wrinkle forehead, show teeth or smile ipsilaterally
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What is hyperacusis?
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Increased noxious quality to loud sounds with lesion to facial nucleus leads to no more innervation of stapedius muscle
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Why is it difficult to detect a lesion to CN 7?
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Even though salivary glands will be out, the parotid gland can still function (via CN 9)
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What does CN 7 innervation of the lacrimal gland do?
What happens if interrupted? |
Lacrimal gland --> vasodilation --> tears
Interruption --> dry eye |
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How do you test for a lesion of CN 7 in the mouth?
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Apply substances to the tip of the tongue
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Where do motor fibers of CN 9 leaving the nucleus ambiguus go?
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Stylopharyngeus --> raises and dilates the pharynx
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Where do motor fibers of CN9 from the salivatory nucleus go?
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Parotid gland, aid in eliciting salivation
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What happens in a CN 9 lesion?
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Drooping arch of the soft palate, uvula deviates to the unaffected side
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What happens if you lose CN 9 afferents from the pharynx and posterior tongue?
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No longer have a gag reflex
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Why are lesions in CN 9 difficult to test?
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Stylopharyngeus and carotid sinus innervated bilaterally, salivation shared by CN 7 and 9, swallowing by CNs 9 and 10, and taste by CNs 7,9, and 10
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What occurs in a unilateral lesion to CN 12?
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Deviation of the tongue to the ipsilateral side (of the lesion)
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How would you distinguish lower motor neuron of CN 12 from an upper motor neuron lesion of CN 12?
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Lower motor neuron = tongue deviates ipsilaterally
Upper motor neuron = tongue deviates contralateral to lesion (because fibers would decussate in the pons) |