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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
Where can the lesion be localized if the cranial nerve and the long tract signs are associated?
Brainstem
Where can the lesion be localized if the cranial nerve symptoms are present but the long tract symptoms are not?
Damage may be to a more anatomically restricted area or peripheral course of cranial nerve
If there is motor/sensory symptoms without evidence of cranial nerve signs, what area can you rule out as a source of the lesion?
Brainstem
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
What are 2 movements produced by the superior rectus?
1. elevate globe in abduction
2. intorsion
What are 2 movements produced by the inferior rectus?
1. move globe down when abducted
2. extorsion
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
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
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
What three muscles besides the extrinsic eye muscles are innervated by CN III? What are their nuclei and functions?
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
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
What is the effect of a lesion to CN 3 on pupil size?
Causes dilated pupil (mydriasis) because no sphincter muscle innervation anymore
What is strabismus?
Chronic deviation of eye 'down and out' due to CN 3 lesion
What is diplopia?
Double vision caused by CN 3 lesion --> strabismus
What is the path of fibers from CN 4?
They loop dorsally and caudally around central gray, cross to other side, and leave brainstem dorsally
What does CN4 innervate?

Action?
Contralateral SO

Depress, intort
What will happen after a lesion to CN 4?
Affected eye will deviate up, chronically extort --> diplopia
What does CN 6 innervate?

What does it do?
LR

Moves eye laterally
What happens in a lesion to CN 6?
Ipsilateral eye deviates medially
What is smooth pursuit?
When the cerebral cortex initiates conjugate lateral deviation of the eyes as a reflex response to visual stimuli
What is sacchades?
Conscious deviation of the eyes
How do fibers travel to allow for coordinated movement of the eye?
Cerebral cortex --> PPRF (pons) --> ipsilateral CN6 nucleus (for LR) and up the contralateral MLF for CN3 nucleus of other eye (for MR)
How will the eyes move with input to the right paramedian nucleus?
Both eyes will rotate to the right
What would be the result if a lesion spared the nuclei of CN 6, but involved the MLFs between CN 3 and CN6?
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
What is internuclear opthalmoplegia?
Lesion in MLF between CN 3 and CN 6
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
What are saccadic movements and what do they require?
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
What is smooth pursuit and what does it require?
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
What is a midbrain area receiving visual afferents?
Pretectal area (rostral to the superior colliculi)
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
What is the pathway for the light reflex?

Lens accomodation?
pretectal nuclei --> EW --> ciliary --> pupillary constrictor

pretectal nuclei --> EW --> ciliary --> ciliary muscle
What is the direct light reflex?
Constriction of the pupil of the illuminated eye
What is the consensual light reflex?
Constriction of the pupil in response to illumination of the other eye
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
What is the pathway that leads from unfocused, close object to the near triad response?
Unfocussed object --> blurred image to visual cortex via retino-calacrine pathway --> to brainstem in occipitomesencephalic tract --> synapse of EW and occulomotor nucleus
What is Argyll-Robertson pupil?
Small pupil that is unresponsive to bright light, but does constrict during near triad
What is the pathway of sympathetic fibers that dilate the pupil?
Hypothalamus --> descend through brainstem and cervical cord --> synapse in interomediolateral cell column --> exit cord in lower cervical roots --> ascend w/ carotid plexus --> pupil
What happens if the sympathetic flow to the pupil is disrupted?
Pupil under less tonic sympathetic input, will be relatively constricted or miotic
What other functions to the face and eye travel in the sympathetic pathway? (2)
Sweating over upper 1/2 of face (sudomotor)
Motor input to the eyelid of Muller's muscle
What happens if sympathetic flow to the face is disrupted? (3)
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)
What are the somatosensory areas innervated by CN 5?
Front of face, external ear
Which cranial nerves innervate the external ear?
CN 7, 9, 10, and 5
What types of fibers have their origin in the Mesencephalic nucleus of CN 5?
proprioceptive fibers from joint capsules of jaw, muscles of mastication, teeth
What is the mesencephalic root of CN V? Where does it lead?
Dendrites and axons of primary afferents, leads to the motor nucleus of CN V for reflex control of chewing
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
What does the motor nucleus of V send out?
Efferents to Muscles of mastication, tensor tympani
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
How does innervation of the ventral and dorsal divisions of CN 7 motor nucleus differ?
Ventral = receives bilateral input from the cortex

Dorsal = receives contralateral input from the cortex
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
What results from a lesion involving the nucleus of CN 7?
Bell's Palsy = flaccid paralysis of facial muscles, inability to close ipsilateral eyelid, wrinkle forehead, show teeth or smile ipsilaterally
What is hyperacusis?
Increased noxious quality to loud sounds with lesion to facial nucleus leads to no more innervation of stapedius muscle
Why is it difficult to detect a lesion to CN 7?
Even though salivary glands will be out, the parotid gland can still function (via CN 9)
What does CN 7 innervation of the lacrimal gland do?

What happens if interrupted?
Lacrimal gland --> vasodilation --> tears

Interruption --> dry eye
How do you test for a lesion of CN 7 in the mouth?
Apply substances to the tip of the tongue
Where do motor fibers of CN 9 leaving the nucleus ambiguus go?
Stylopharyngeus --> raises and dilates the pharynx
Where do motor fibers of CN9 from the salivatory nucleus go?
Parotid gland, aid in eliciting salivation
What happens in a CN 9 lesion?
Drooping arch of the soft palate, uvula deviates to the unaffected side
What happens if you lose CN 9 afferents from the pharynx and posterior tongue?
No longer have a gag reflex
Why are lesions in CN 9 difficult to test?
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
What occurs in a unilateral lesion to CN 12?
Deviation of the tongue to the ipsilateral side (of the lesion)
How would you distinguish lower motor neuron of CN 12 from an upper motor neuron lesion of CN 12?
Lower motor neuron = tongue deviates ipsilaterally

Upper motor neuron = tongue deviates contralateral to lesion (because fibers would decussate in the pons)