Cranial Nerves Flashcards
0
Q
If a cranial nerve and long tract signs are associated, where can the lesion most likely be located?
What is more likely if there is not signs of long tract involvement?
What if sensory or motor impairment is present but cranial nerve signs are not evident?
A
Within the brainstem.
The damage many be smaller or in the peripheral course of the nerve
Implications of the brain stem are less likely
1
Q
Where do the olfactory nerves exit the skull?
A
Cribriform plate of ethmoid
2
Q
Where do the optic nerves and ophthalmic artery exit the skull?
A
Through the optic foramen
3
Q
What nerves exit through the superior orbital fissure?
A
3,4,6, ophthalmic branch of 5
4
Q
What cranial nerve exits through the foramen rotundum?
A
Maxillary division of the trigeminal nerve
5
Q
What cranial nerve exits through the foramen ovale?
A
The Mandibular branch of the trigeminal nerve
6
Q
What exits the skull through the foramen lacerum?
A
The internal carotid artery
7
Q
What exits the skull through the foramen spinosum?
A
The middle meningeal artery
8
Q
What exits the skull through the internal acoustic meatus?
A
CN 7 and 8
9
Q
What exits the skull through the jugular foramen?
A
CN 9, 10, 11
10
Q
What exits the skull through the hypoglossal canal?
A
CN12
11
Q
What exits the skull through the foramen magnum?
A
Medulla and meninges, CN 11, vertebral arteries, anterior and posterior spinal arteries
12
Q
What cranial nerves control eye movements?
A
CN 3, 4 and 6
13
Q
Where do the four rectus muscles insert on the eye?
A
The anterior half.
MR is purely horizontal so contraction will do pure medial rotation (adduction)
LR is purely horizontal so contraction will do pure lateral rotation (abduction)
SR and IF insert 23degrees from the center (toward the nose) so when they contract they will go up and out and down and out respectively
14
Q
How does CN 6 move the eye?
A
It innervates the lateral rectus muscle so it will abduct the eye.
15
Q
What direction does the SR move the eye?
A
- Up and out because the muscle inserts on a 23 degree lateral angle to the straight ahead position of the eye
- Intorsion
16
Q
When are the SR and IR most effective?
A
When the eye is abducted 23 degrees
17
Q
All superior named muscles move the eyeball in what direction?
A
Intorsion
18
Q
All inferior named muscles produce what movement of the eye?
A
Extorsion
19
Q
What direction does the inferior rectus move the eye?
A
- Down and abducted
2. Extorsion
20
Q
How do the superior oblique and inferior oblique approach their insertion points on the eye ball?
A
From the anterior direction at 51 degrees medial to the straight ahead position of the eye
21
Q
When is the superior oblique the most efficient depressor?
A
When the eye is a little adducted
22
Q
How does the superior oblique move the eye?
A
Down and in
23
Q
How does the inferior oblique move the eye?
A
Up and in (most effective when the eye is adducted)
24
What eye muscles are intorters?
| What eye muscles are extorters?
Intorters- superior oblique and superior rectus
| Extorters- inferior oblique and inferior rectus
25
What is the role of the superior colliculi?
| What is the role of the cerebral peduncle?
1. It is the optic portion of the tectum
2. It carries motor tracts from the cerebral cortex to the brainstem or spinal cord (corticospinal or corticobulbar tracts)
26
Where does the motor nucleus of CN 3 sent root fibers?
Through the red nucleus which is a motor relay to the cerebellum, cerebral cortex and spinal cord
27
Where is the parasympathetic nucleus of CN 3 located?
| What is it called?
Edinger-Westphal nucleus and it is located just below the periaquaductal gray
28
What does CN 3 innervate?
Ipsilateral medial, superior and inferior rectus, inferior oblique, levator palpebrae
29
If a patient has severe ptosis, what muscle is most likely affected?
If the patient has mild ptosis, what muscle is affected?
The levator palpebrae (CN3)
The mueller muscles (sympathetics)
30
If the third cranial nerve is damaged, what would the presentation be?
The eye would be down and out because the superior oblique would still be depression (and trying to be going in) but the lateral rectus still works and pulls the muscle laterally (abducts)
You would also see severe ptosis because the levator palpebrae would be blown
31
What is the superior rectus subnucleus of cranial nerve 3? Where do the fibers go?
It is a paired nucleus where the fibers completely decussate. So the right superior rectus nucleus will send fibers that travel with the left cranial nerve 3 and innervate the left superior rectus
32
What is the term for double vision?
What is the term for "down and out"?
What is the term for dilated pupil?
What causes "down and out" movement of the eye?
Diplopia
Extropia
Mydriasis
CN 3 palsy
33
In what syndrome would you see mild ptosis due to mullers muscle dysfunction?
Horners syndrome (a disorder where sympathetics get messed up)
34
What muscles are supplied by the edinger-Westphal nucleus?
1. The sphincter muscles of the iris that reduce the size of the pupil in response to light and accommodate the lenses for close up vision. Therefore a CN 3 lesion could also produce dilated pupil.
2. Ciliary muscles which when contracted reduce tension on the zonules to reduce tension on the lens and allow for accommodation (more spherical)
35
What is presbyopia?
With age the flexibility of the lens to assume spherical shape for up close reading is reduced
36
Where do the root fibers of CN 4 exit the brainstem?
| Does CN 4 innervate ipsilateral or contralateral muscles?
Loop dorsally and caudally around the central gray to cross in the anterior medulla after exiting from the brainstem.
Because the fibers cross, they innervate contralateral superior oblique muscles.
37
Lesion to CN 4 would cause what problems?
1. Vertical double vision
2. Slow movement of the eye to the lesion
3. Extorsion
4. Elevated eye
38
Damage to what cranial nerve causes oblique Diplopia?
| How do patients tend to compensate for this?
CN 4 because the superior oblique muscle will not work and the affected eye will drift up and outward.
Because the two pupils are at different vertical levels, there will be double vision with the images from the two eyes on top of each other.
Patients try to compensate by turning their head in and down (away from the hyper-deviated eye)
39
What are the three nuclei of CN 7?
Motor nucleus
Superior salivatory nucleus
Nucleus solitarius
40
What is the function of CN 6?
What would the presentation be for a CN 6 lesion?
Move the lateral rectus on the ipsilateral side.
Medial deviation on the ipsilateral side
41
For lateral movements of the eye, what two muscles need to be operating in synchrony?
What is this called?
If you are moving your eyes to the right, you need your right lateral rectus and your left medial rectus to be coordinated.
This is called a yoke pair.
42
What are the sources of input that initiate conjugate lateral deviation of the eyes?
1. Cerebral cortex for reflex following visual stimulus (smooth pursuit) or Conscious deviation of the eyes (sacchades)
3. Vestibular systems
43
In order to coordinate lateral movements of the eye, where do fibers descending from the cerebrum synapse first?
1. The fibers descend in the brainstem to synapse first at the level of CN 6 in the paramedian pontine reticular formation (pprf)
2 the pprf sends fibers to CN 6 nucleus on the ipsilateral side and contralateral MLF to synapse on cn3 nucleus that can move the contralateral eye medially
44
What are sacchades?
| What input allows these movement to occur?
Rapid movements of the eyes under conscious control allowing you to abruptly change point of fixation.
Saccadic movements require input from the frontal eye field (brodemanns 8) and the superior colliculus to initiate targeting. Both of these areas project to the contralateral pprf to initiate horizontal movement
45
What is smooth pursuit?
| Where do the inputs for smooth pursuit come from?
Slow tracking movements allowing you to keep an object in your central vision.
Visual cortex and extrastriate visual cortex (Brodmann 18/19)
46
Where does the frontal eye field project to to facilitate saccadic movement of the eyes?
FEF projects through the anterior limb of the internal capsule, decussates at the midbrain-pontine junction to the contralateral PPRF.
The PPRF directly innervates the lateral rectus on the ipsilateral side and crosses back to the original side (where the FEF initiated the signal) via MLF to innervate the medial rectus subnucleus of cn3 on the other side
47
What would a lesion in the MLF present with?
| What is this disorder called?
It interrupts the connection between CN 6 and CN 3 on the other side so there is trouble coordinating synchronized eye movements
This is called internuclear ophthalmoplegia (INO)
48
Where is the pretectal area?
What are the afferents to the pretectal area?
What are the efferents from the pretectal area?
What is the main purpose of this area?
1. Rostral extreme of the tectum
2. Direct light information input from the retinas and input from the contralateral pretectal nucleus via the posterior commissure
3. Ipsilateral and contralateral edinger-Westphal nuclei
4. Symmetrical pupil constriction and lens accomodation
49
1. What is the direct light reflex?
| 2. What is the consensual light reflex?
Direct- light will constrict the pupil of the illuminated eye
Consensual- the contralateral pupil will also constrict in response to light in the opposite eye due to pretectal connections
50
What are the three motor elements of the near triad?
| What cranial nerve is involved (specifically what branch)
CN 3 parasympathetic branch aids in achieving vision of near objects.
1. Convergence of the eyes (both medial rectus contract)
2. Rounding of the lens through contraction of ciliary muscles, relaxing tension on the zonules to increase curvature and optical power
3. pupillary constriction to limit the entrance of stray light
51
When using the near triad, what is the blurred image conveyed to and through what tract?
How is this information then relayed to the brainstem?
What nuclei does the signal synapse with and what are the outcomes?
The blurred image travels through the retino-calcarine pathway to the occipital lobe visual cortex.
It then travels to the brainstem via the occipitomesencephalic tract to synapse on the edinger-Westphal nuclei which constrict the pupil, accommodate the lens and to the CN 3 medial rectus subnucleus to converge the eyes.
52
What is argyll-Robertson pupil?
| What is it caused by?
It is a small pupil unresponsive to bright light but that still constricts during the near triad
It is caused by CNS syphilis
53
1. What fibers are responsible for light reflex on the pupil?
2. What fibers are responsible for near triad reflex?
1. Ventromedial
| 2. Ventrolateral
54
Where do preganglionic neurons for the sympathetic chain get input?
Where do they synapse?
Neurons from the hypothalamus descend through the brainstem and cervical spinal cord and synapse on the preganglionic neurons in the intermediolateral cell column.
These preganglionics ascend in the sympathetic chain and terminate in the superior cervical ganglion.
55
What do sympathetic postganglionics travel with through the cavernous sinus?
The carotid plexus and internal carotid artery
56
If the superior cervical ganglion sympathetic pathway is interrupted, what would the patient present with?
What is this disorder called?
What is a likely culprit for development of this disorder?
1. The pupil would be relatively constricted or miotic (more parasympathetic tone)
2. The patient would not sweat on the upper half of the face
3. The patient would have mild ptosis from muller muscle relaxation
This disorder is called Horners syndrome and is often caused by a tumor on the apex of the lung that compresses the cervical ganglion
57
How would you test a patient for Horners syndrome?
Turn off the lights and see if their eyes dilate
58
Which is the only branch of the trigeminal nerve that has a motor component?
V3- pterygoid. The jaw deviates to the side of the lesion.
59
How far into the spinal column does the trigeminal tract run?
It runs down to C2-C4 in the substantia gelatinosa
60
Where does CN 5 provide somatosensory input?
The face (but the external ear neck and back of the head are innervates by CN 5,7,9,10and cervical nerves 2-4.)
61
What is the corneal reflex?
The cornea of the eye is swabbed with a cotton swab and the person should blind because v1 afferent-> CN 7-> blink
62
Where do proprioception fibers with info from jaw, muscles of mastication and teeth originate?
Mesenchephalic nucleus of CN 5
63
Where do the axons of mesencephalic nuclear cells end?
In the motor nucleus of CN 5 to provide reflex for the control of chewing.
64
Where does tactile information from the face go?
To the chief sensory nucleus and spinal nucleus of CN 5.
65
What type of fibers travel in the spinal nucleus of CN 5 and spinal tract of CN 5?
Pain and temperature input from the face
66
Where does the motor nucleus of CN 5 send efferent axons?
To the muscles of mastication and tensor tympani of the ear
67
What would a lesion to the Mesencephalic nucleus of 5 present with?
1. Loss of muscle sense creating difficulty in executing controlled chewing
2. Difficulty determining pressure exerted on teeth when biting
3. Difficulty in appreciating position of jaw
68
A lesion to the spinal tract and nucleus of five would cause what?
Loss of pain and temperature sensation to the same side of the face.
They could still feel touch though because that goes to the chief sensory nucleus of 5
69
If the whole fifth nerve was lesioned, what symptoms would the patient have?
(5)
1. Loss of position sense of jaw, pressure sense when biting, difficulty in chewing
2. Loss of pain and temperature to the ipsilateral side
3. Blink and corneal reflex would be lost with stimulation of the ipsilateral eyelid or cornea (but stimulation of the opposite, functional eyelid or cornea will cause bilateral lid closure bc CN 7 is still intact)
4. Sneeze reflex is lost from tickling nasal mucosa as will the noxious sensation from sniffing ammonia
5. Jaw will deviate toward the lesion because of flaccid paralysis of the ipsilateral muscles of mastication
70
What are the afferent and efferents of the corneal and blink reflex?
What response would be expected if CN 5 was lesioned and you swabbed the side of the lesion?
What response would be expected if you swabbed the normal eye?
1. Afferent are v1 branch of the CN 5. Efferents are CN 7.
2. The affected eye would show loss of corneal reflex ipsilaterally
3. If swabbing the normal eye, you would get bilateral blinking because the seventh cranial nerve still works
71
What are the three nuclei of CN 7?
Somatic motor nucleus
Visceral motor nucleus (superior salivatory)
Visceral afferent nucleus (nucleus solitarius)
72
Where do efferents from the motor nucleus of CN 7 go?
| What two divisions do they break into?
Muscles of facial expression including orbicularis oculi that closes the eye
Dorsal- lower part of the face
Ventral- upper part of the face
73
What disorder would be caused by a lesion to the motor nucleus or root of CN 7?
What are four major symptoms associated with it?
Is it an upper motor neuron or lower motor neuron disorder?
Bells palsy:
1. flaccid paralysis of the upper and lower facial muscles excluding the muscles of mastication
2. Inability to close eyes on ipsilateral side
3. Inability to wrinkle forehead, show teeth or smile ipsilateral to the lesion
4. Lack of innervation to the stapedius increases the noxious quality of loud sounds bc it can't dampen them
It is a lower motor neuron disorder.
74
What does the ventral portion of motor CN 7 innervate? What is the input to the ventral portion?
What does the dorsal portion of motor CN 7 innervate? What is the input to the dorsal portion?
Ventral innervates the upper portion of the face. It receives bilateral input from the cortex
Dorsal innervate the lower portion of the face. It receives contralateral input from the cortex
75
A central upper motor neuron lesion of the fibers of the motor cortex would cause what presentation?
Facial drooping in the muscles of the lower portion of the face.
76
Which glands are innervates by the CN 7 superior salivatory nucleus?
What would an interruption to these fibers cause?
All the glands of the face except the parotid (CN 9)
The parotid can still produce saliva so problems with the submandibular and sublingual glands are hard to detect but the lacrimal gland vasodilator to secrete tears so an interruption would cause dry eye.
77
What portion of CN 7 synapses on the solitary nucleus?
Taste from the anterior 2/3 of the tongue
78
What are the three nuclei where the CN 9 distributes?
Nucleus solitarius
Inferior salivatory nucleus
Nucleus ambiguus
79
What nucleus contains motor functions of CN 9?
Nucleus ambiguus supplies the stylopharyngeus muscles which raises and dilates the pharynx
Salivatory nucleus supplies the parotid glad to supplement CN 7 in making saliva
80
If there is a lower lesion affecting CN 9, what happens to the palate?
If there is an upper lesion affecting CN 9, what happens to the palate?
If there is a lower right lesion, the left side of the palate will be unopposed so the palate will pull to the left.
Upper right lesion would cause the palate to move to the right
81
What are the four types of sensory information that enter CN 9 and distribute to the nucleus solitarius?
1. Pain, temp, and touch from the pharynx and posterior tongue
2. Blood pressure info from the carotid sinus
3. Taste sensation from the posterior 1/3 of the tongue
4. Pain from the external auditory meatus (5, 7, 9, 10)
82
What happens to the nucleus solitarius functions if the ninth nerve is lesioned?
The gag reflex is lost (no sensory to pharynx)
Difficulty swallowing
No detectable deficit in blood pressure regulation despite the fact that the carotid sinus is not relaying to nucleus solitarius
83
Why are the functions of CN 9 difficult to test?
1. Stylopharyngeus and carotid sinus are innervated bilaterally so their functions are not entirely lost
2. Salivation is shared with CN 7
3. Swallowing is shared with 10
4. Taste is 9, 7, 10
Damage is usually only seen with bilateral damage to 9 or damage to 9 and 10 together
84
What does CN 12 innervate?
It arises from the hypoglossal nucleus and innervates the tongue on the ipsilateral side.
85
An UMN lesion to CN 12 would cause what to happen?
| A LMN lesion to CN 12 would cause what to happen?
The tongue would deviate to the opposite side of the lesion.
The tongue would deviate toward the lesion.
86
What does the vagus nerve innervate?
Sensory and motor innervation to the pharynx and larynx and thoracic and abdominal viscera
87
What nuclei do the vagus nerve synapse with?
Nucleus solitarius- afferents from rom abdominal and thoracic viscera, efferents for reflex control of viscera, afferents from the pharynx for swallowing reflexes
Dorsal efferent nucleus (motor nucleus) to the parasympathetics of the GI tract, to slow heart and increase peristalsis
88
Which nerve has the largest control over the pharynx?
9 has a more substantial effect than 10
89
What nucleus provides the major innervation of the pharynx and larynx?
How does swallowing occur?
Motor fibers from the nucleus ambiguus.
1. CN 9 dilate the pharynx to allow food to course toward the esophagus
2. Constrictors of the pharynx are activated by 10 and 11 to force food down
90
What nerve gathers taste from the epiglottis?
Vagus and then it enters nucleus solitarius like 7 and 9
91
Where does the spinal portion of CN 11 originate?
Where does it exit?
What does it innervate?
Accessory nuclei at C1-C6.
It is part of the ventral gray and exits between sensory and motor spinal roots
It innervates the trapezius and SCM so lesions would cause problems shrugging or turning head to the opposite side
92
Even though the larynx is innervated bilaterally by CN 10 and 11, how would you be able to detect a unilateral lesion to nucleus ambiguus?
There would still be a detectable alteration in voice.
