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Neuroscience and Head and Neck Anatomy > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

Cranial Nerve 1

  1. Name of CN?
  2. Function?
  3. Sensory? Motor? Both?
  4. Course of travel?
  5. Exit foramen?
A
  1. Olfactory nerve
  2. Olfactory stimuli detected by chemoreceptors in neuroepithelium of nasal cavity
  3. Sensory only
  4. Receptors in nasal cavity –> cell body in olfactory bulb –> sends info via projections in olfactory tract
  5. Cribiform plate of ethmoid bone
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2
Q

Cranial Nerve 2

  1. Name
  2. Function
  3. Sensory, motor, or both
  4. Course of travel
  5. Exit foramen
A
  1. Optic Nerve
  2. (A) carries visual information from retina to lateral geniculate nucleus of thalamus (B) afferent limb of pupillary reflex
  3. Sensory only
  4. Retinal ganglion cells are part of CNS so CN2 is actually a tract, not a nerve persay
  5. Optic canal
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3
Q

If a person has a problem with CN2 on the left side, what will you observe in the pupillary reflex?

A

When the light is shone in their left eye, neither of their pupils will constrict (CN2 damaged, carries afferent pupillary reflex information). If the light is shone in their right eye, their right pupil will constrict (CN2 intact) and their left eye will constrict (CN3 intact). Thus, CN3 is responsible for the consensual constriction of the contralateral pupil whereas CN2 is responsible for the constriction of the pupil that is ipsilateral to the stimulus.

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4
Q

Cranial Nerve 3

  1. Name
  2. Sensory? Motor? Both?
  3. Function
A
  1. Occulomotor nerve
  2. Motor only (Somatic motor and parasympathetic visceral motor)
  3. Move the eye up and medially, elevate the upper eyelid, efferent limb of pupillary reflex, accomodation
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5
Q

Cranial Nerve 3

What muscles are innervated by this nerve?

A

Somatic motor

  • Medial rectus
  • Inferior rectus
  • Superior rectus
  • Inferior oblique
  • Levator palpabrae superioris

Parasympathetic visceral motor

  • Pupillary constrictor
  • Cilliary muscle of lens
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6
Q

If a person had a lesion that effected CN3, what would their symptoms be and why?

A
  • Eye moves down and out due to unopposed action of lateral rectus (CN6) and superior oblique (CN4)
  • Ptosis due to loss of levator palpabrae superioris
  • Fixed dilated pupil due to loss of constriction of pupil on same side as lesion
  • Double vision due to loss of accomodation
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7
Q

Describe the pathway traveled by neurons in CN3 that carry somatic motor information.

A

Oculomotor nucleus in midbrain –> exit brainstem at interpeduncular fossa –> cavernous sinuses –> exit skull at supraorbital fissure –> innervate eye muscles

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8
Q

Describe the pathway traveled by neurons in CN3 that carry parasympathetic visceral motor information.

A

Pre-ganglionic neurons: Edinger-Westphal nucleus –> interpeduncular fossa –> cavernous sinus –> cilliary ganglion in face

Post-ganglionic neurons: cilliary ganglion –> pupillary constrictor and ciliary muscle of lens

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9
Q

Cranial Nerve 3 (oculomotor nerve) has 2 nuclei that its cell bodies arise from.

  • Where are these nuclei?
  • What type of information is conveyed by the cell bodies of each nucleus?
A
  • Edinger-Westphal nucleus in superior colliculus of midbrain –> pre-ganglionic parasympathetic motor neurons
  • Oculomotor nucleus in superior colliculus of midbrain –> somatic motor neurons to muscles of eye
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10
Q

Cranial Nerve 4

  1. Name
  2. Sensory, motor or both
  3. Function
  4. Course traveled in brain
  5. Exit point of skull
A
  1. Trochlear Nerve
  2. Motor (somatic)
  3. Innervates superior oblique muscle which moves the eye downward and medially
  4. Trochlear nucleus in inferior colliculus of midbrain –> pontomedullary junction –> cavernous sinus –> supraorbital fissure –> muscle
  5. Supraorbital fissure
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11
Q

How do patients with a CN4 lesion typically present?

A

With difficulty going down stairs.

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12
Q

What is unique about CN 4?

A

It is the only CN to fully decussate, thus lesions affect the contralateral superior oblique muscle

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13
Q

What are the 3 branches of the trigeminal nerve?

A

Opthalmic

Maxillary

Mandibular

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14
Q

Cranial Nerve 5

  1. Name
  2. Sensory, motor, both?
  3. Function
  4. Function
  5. Course of travel
  6. Course of travel
  7. Exit foramen
A
  1. Trigeminal nerve
  2. Both (somatic sensory and branchial motor)
  3. Sensory
    1. Innervation to face
    2. Pain and temp for inside nose, mouth, anterior 2/3 tongue
  4. Motor
    1. innervates muscles of mastication
  5. Sensory
    1. trigeminal sensory nucleus –> pons –> meckel’s cave
      1. Opthalmic –> cavernous sinus –> supraorbital fissure
      2. Maxillary –> foramen rotundum
      3. Mandibular –> foramen ovale
  6. Motor
    1. Trigeminal motor nucleus –> pons –> meckel’s cave –> joins mandibular to exit via foramen ovale –> muscles of mastication
  7. Supraorbital fissure (V1); foramen rotundum (V2); foramen ovale (V3 and motor roots)
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15
Q

Which cranial nerves are somatic motor?

A

3, 4, 6, 12

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16
Q

Which nerves are special visceral motor?

A

5, 7, 9, 10, 11

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17
Q

Which CNs are parasympathetic (visceral efferent)

A

3, 7, 9, 10

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18
Q

Which CNs carry afferent visceral sensory information?

A

7, 9, 10

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19
Q

Which CNs carry afferent general visceral sensory information?

A

9, 10

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20
Q

Which CNs carry afferent general somatic sensory information?

A

5, 7, 9, 10

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21
Q

Which CNs carry afferent special somatic sensory information?

A

8

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22
Q

What arteries supply blood to the edinger-westphal and oculomotor nuclei?

A

Posterior cerebral and superior cerebellar arteries

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23
Q

This is a section of the midbrain. The two bumps on top are the superior colliculi. Label the 2 missing nuclei.

A
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24
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25
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26
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27
Q
A
28
Q

Describe what is happening in the pupillary light refelx.

A

Light stimulus enters right eye. Sensory information about stimulus carried via CN2 to pretectal nucleus on ipsilateral side. Pretectal nucleus talks to edginger westphal nucleus of same side and also to edinger westphal of contralateral side via posterior commisure. CN3 has parasympathetic pre-ganglionic cells in EW nucleus, sends signal to post-ganglionic nervs in ciliary ganglia on both sides to constrict both pupils.

29
Q

Where do the primary sensory neurons for trigeminal nuclei lie?

A

Mainly in the trigeminal ganglion

30
Q

Explain the pathway that is followed by nerurons in the mesencephlanic nucleus.

A

Sensory stimuli about proprioception from muscles of mastication are collected by neurons whose cell bodies are in the mesencephalic nucleus in the midbrain. Those neurons do not project up to the thalamus but instead have ascending and descending projections that go elsewhere.

31
Q

Explain the pathway that neurons of the chief sensory nucleus take to provide information.

A

Sensory stimuli related to fine touch and dental pressure excite receptors on the endings of neurons whose cell bodies are in the trigeminal ganglion. The information travels to the trigem ganglion, then the same neuron sends a projection to the chief sensory ganglion in the pons. That project synapses on another neuron that crosses and ascends to the ventral posterior medial nucleus of the thalamus as the trigeminal lemniscus. From there, tertiary sensory neurons travel to the face area of the primary somatosensory cortex.

A second, smaller pathway, called the dorsal trigeminal tract, travels from the chief trigeminal sensory nucleus to the ipsilateral VPM, without crossing. This pathway appears to convey dental pressure.

NOTE: this is analagous to the medial lemniscus in the spine.

32
Q

Explain the pathway that neurons of the spinal trigeminal nucleus take to convey their information.

A

Sensory stimuli of crude touch, pain and temp are detected by nerve endings whose cell bodies are in the trigeminal ganglion. These neurons then send projections to the spinal nucleus in the medulla where they synapse with a neuron that crosses and ascends as the trigeminothalamic tract to the VPM. From there, tertiary sensory neurons travel to the face area of the primary somatosensory cortex.

NOTE: this is analagous to the spinothalamic tract

33
Q

Cranial Nerve 6

  • What is the name?
  • Sensory, motor, both?
  • Function?
  • Location in brain?
  • Where is nucleus?
A
  • Abducens
  • Somatic motor only
  • Innervation of lateral rectus
  • Exits brainstem at pontomedullary junction –> cavernous sinus –> exit skull at supraorbital foramen
  • Cell bodies are in abducens nucleus in pons (in/near facial colliculus)
34
Q

Cranial Nerve 7

  • Name?
  • Sensory, motor, both?
  • Function?
A
  • Facial nerve
  • Branchial motor and sensory
  • Motor - muscles of facial expression, stapedius, stylohyoid, posterior digastric
  • Parasympathetic innervation to lacrimal glands and salivary glands, taste to anterior 2/3 of tongue, sensation to small area near external auditory meatus
35
Q

Describe the location and path of travel in the brain of neurons that control the motor functions of the facial nerve.

A

Facial nucleus in pons –> fibers loop dorsally around abducens nucleus –> exit brainstem at cerebellopontine angle –> subarachnoid space –> internal auditory meatus –> auditory canal with CN 8 –> stylomastoid foramen – >parotid gland –> TZBMC

36
Q

Describe the location and path of travel in the brain of neurons that control the parasympathetic functions of the facial nerve.

A
  • Parasympathetic preganglionic neurons in the superior salivatory nucleus –> exit as greater petrosal nerve –> pterygopalatine ganglion –> postganglionic nerve –> lacrimal gland + nasal mucosa
  • Parasympathetic preganglionic neurons superior salivatory nucleus –> exit as lingual nerve –> submandibular ganglion –> postganglionic nerve –> submandibular and sublingual glands
37
Q

How much saliva is produced by the submandibular gland?

A

~70%

38
Q

Describe the pathway taken by neurons involved in taste for anterior 2/3 tongue.

A

Taste receptors in tongue send information via chorda tympani nerve to their cell bodies in facial geniculate nucleus –> same neuron projects to nucleus solitarius where sensory input combines with tongue sensory info from CN 9 and 10 –> Synapse w/ neuron that carries info to VPM –> synapses with neuron that carries to cortical taste area

39
Q

How can you distinguish between an UMN lesion that goes to the facial nucleus or an LMN lesion that goes from the facial nucleus to the muscles of facial expression?

A

LMNs that innervate the upper face are synapsed upon by UMNs from both the left and right motor cortices. LMNs that innervate the lower face are synapsed upon by UMNs from only the opposite motor cortex (i.e. left lower face is innervated by right motor cortex).

  • UMN lesion - lower face on side contralateral to lesion will show deficit, upper face will be normal (possibly very mild weakness but unlikely to be significant)
  • LMN lesion - both lower and upper face on side ipsilateral to lesion will show deficit
40
Q
  • What is Bell’s Palsy?
  • What causes it?
  • How does it present clinically?
  • How is it diagnosed?
  • What findings would you expect upon neurological exam?
  • What symptoms, if present in conjunction with those of Bell’s Palsy, would suggest UMN lesion instead?
  • What tests should be ordered as part of differential diagnosis?
  • What is the treatment course?
A
  • Most common facial nerve disorder in which all divisions of the facial nerve are impaired within a few hours or days and then gradually recover
  • The cause is unknown, although viral or inflammatory mechanisms have been suggested
  • Symptoms:
    • Unilateral facial weakness of the lower motor neuron type
    • retroauricular pain
    • Hyperacusis can occur because of stapedius muscle weakness
    • Dry eye resulting from decreased lacrimation with parasympathetic involvement
  • Diagnosis is based on clinical history and exam
  • Neurologic examination is notable for unilateral lower motor neuron type facial weakness, sometimes associated with loss of taste on the ipsilateral tongue
  • The presence of hand weakness, sensory loss, dysarthria, or aphasia
  • MRI scan to exclude a structural lesion and blood studies including a blood count, glucose, and Lyme titer.
  • 10-day course of oral steroids started soon after onset with lubricating eyedrops and instructions to tape the eye shut at night
41
Q
  • What are crocodile tears?
  • What causes them?
A
  • Patients experience lacrimation instead of salivation when they see food
  • Aberrant regeneration of parasympathetic fibers of CN 7
42
Q
  • What is facial synkinesis?
  • What causes it?
A
  • Abnormal movement of two muscles together (i.e. when you try to voluntarily do one motion you also involuntarily do another)
  • Aberrant regeneration of different motor branches of the facial nerve
43
Q
  • What is the corneal reflex?
  • Describe the innervation that leads to this reflex
  • What does the reflex tell you clinically?
A
  • Eye closure in response to gentle stroking of each cornea with a cotton swab
  • Afferent limb = ophthalmic division CN 5 to the chief sensory and spinal trigeminal nuclei; Efferent limb = facial nerve to orbicularis oculi
  • A lesion of the trigeminal sensory pathways, the facial nerve, or their connections causes a decreased corneal reflex in the ipsilateral eye
44
Q
  • What is the jaw jerk reflex?
  • Describe the innervation that gives rise to this reflex.
  • What does this reflex tell you clinically?
A
  • When jaw jerks forward in response to tapping on the chin with the mouth slightly open
  • Monosynaptic pathway of primary sensory neurons in the mesencephalic trigeminal nucleus –> send axons to the pons to synapse in the motor trigeminal nucleus
  • Normal individuals - reflex is minimal or absent. In bilateral upper motor neuron lesions or diffuse white matter disease, the jaw jerk reflex may be brisk.
45
Q

Why is unilateral hearing loss is not seen in lesions in the central nervous system proximal to the cochlear nuclei?

A

Because auditory information from each ear ascends bilaterally in the brainstem, with decussations oc- curring at multiple levels

46
Q

What is the lateral lemniscus?

A

The lateral lemniscus is an important as- cending auditory pathway in the pons and lower midbrain that terminates in the inferior colliculus

47
Q

What are the superior olivary nuclei?

A

The superior olivary nuclei appear to function in localizing sounds horizontally in space

48
Q

Auditory information ascending through the brainstem and thalamus to the auditory cortex does contain a relatively greater contribution from the […] ear.

A

Contralateral

49
Q

What information do the vestibular nuclei convey to the brain?

A

vestibular nuclei are important for adjustment of posture, muscle tone, and eye position in response to movements of the head in space

50
Q

What areas of the brain does the vestibular branch of CN 8 project to?

A

Intimate connections with the cerebellum, and with the brainstem motor and extraocular system

51
Q

What do the semicircular canals of the ear do?

A

Detect angular accel- eration around three orthogonal axes

52
Q

Describe the pathway of activation for information conveyed by the semicircular canals of the vestibular system (i.e. info about angular acceleration).

A

Rotation of the head around any of the axes of the semicircular canals causes movement of en- dolymph through the ampullae –> deforms the gelatinous cupula –> stimulate mechanoreceptor cilia of hair cells in crista ampullaris (a ridge within each ampulla) –> activate terminals of bipolar primary sensory neurons that have their cell bodies in the vestibular ganglia of Scarpa and send axons into the vestibular nerves

53
Q

What do the utricle and saccule of the ear do?

A

they detect linear acceleration and head tilt

54
Q

Describe the pathway of information conveyed by the utricle and saccule (i.e. info about linear acceleration and head tilt).

A

Calcified crystals (otoliths) sit on a gelatinous layer within which mechanoreceptor hair cells are embedded –> Gravity or other causes of linear acceleration pull on the crystals and activate these hair cells –> vestibular ganglia

55
Q

The superior vestibular ganglion receives input from the […] . The inferior vestibular ganglion receives input from the […].

A
  • utricle, anterior saccule, and anterior and lateral semicircular canals
  • posterior saccule and posterior semicircular canal
56
Q

What is the medial longitudinal fasiculus?

A

medial longitudinal fasciculus (MLF) is an important pathway that connects the nuclei involved in eye movements to each other and to the vestibular nuclei. This pathway mediates the vestibuloocular reflex, in which eye movements are adjusted for changes in head position.

57
Q
  • What is a vestibular schwannoma?
  • Mean age of onset?
  • Bilateral or unilateral?
  • Pathogenesis?
  • Symptoms?
A
  • Most common form of cerebellopontine angle tumor
  • 50 years
  • Unilatearl
  • Slow growing tumor develops where CN VIII enters the internal auditory meatus. Initially the tumor grows within the bony auditory canal, but then it expands into the cerebellopontine angle
  • Common early symptoms are unilateral hearing loss, tinnitus (ringing in the ear), and unsteadiness
58
Q
  • What is vertigo?
  • What are other causes of dizziness?
  • What does vertigo suggest pathologically?
  • What causes vertigo?
  • What symptoms should be asked about in order to rule out brainstem stroke or brain hemmorrhage?
A
  • A spinning sensation of movement
  • Faintness, nausea, and unsteadiness on one’s feet
  • Suggestive of vestibular disease
  • Lesions anywhere in the vestibular pathway, peripheral disorders involving the inner ear, or central disorders of the brainstem or cerebellum (less common)
  • Diplopia, other visual changes, somatosensory changes, weakness, dysarthria, incoordination, or impaired consciousness
59
Q

What is Meniere’s disease?

A

In Meniere’s disease, patients have recurrent episodes of vertigo, accompanied by fluctuating and sometimes stepwise, progressive hearing loss and tinnitus. Patients with Meniere’s disease also often complain of a full feeling in the ear. The etiology is thought to be excess fluid and pressure in the endolymphatic system. This is tested by cold or hot water in the inner ear.

60
Q

Cranial Nerve 9

  • Name?
  • Motor, sensory, both?
  • Course of travel in brain?
  • Nuclei?
  • Exit from skull?
A
  • Glossopharyngeal nerve
  • Branchial motor, parasympathetic, visceral and somatic sensation
  • Ventrolateral medulla below pontomedullary junction at level of inferior olive and inferior cerebellar peduncle –> subarachoid space –> jugular foramen
  • NUCLEI:
    • Nucleus ambiguus –> branchial motor for staphylopharyngeus and afferent limb gag reflex
    • Caudal nucleus solitarius (cardiorespiratory nucleus) –> input from chemoreceptors and baroreceptors from carotid body
    • Rostral nucleus solitarius (gustatory nucleus) –> input form taste receptors on posterior 1/3 tongue
    • Superior glossopharyngeal ganglion –> pain, temp, touch from posterior tongue, ear, and external acoustic meatus
    • Parasympathetic preganglionic axon from inferior salivatory nucleus –> tympanic nerve –> lesser petrosal nerve –> otic ganglion –> postganglionic neuron –> parotid gland
    • Jugular foramen
61
Q

Cranial Nerve 10

  • Name
  • Sensory, motor, both?
  • Location / course of travel in brain?
  • Nuclei?
  • Exit skull?
A
  • Vagus nerve
  • Both
    • Branchial motor to pharyngeal, laryngeal muscles and efferent gag reflex
    • Parasympathetic to most organs of body
    • Sensation in pharynx + meninges
    • Taste epiglottis and pharynx
    • Chemoreceptors and baroreceptors in aortic arch
  • Ventrolateral medulla below 9 –> subarachnoid space –> jugular foramen
  • NUCLEI
    • Nucleus ambiguus –> motor and efferent gag reflex
    • Dorsal motor nucleus of CN X –> parasympathetic innervation
    • Spinal trigeminal nucleus –> vagal ganglia –> sensation pharynx + meninges
    • Rostral nucleus solitarius –> taste epiglottis and pharynx
    • Caudal nucleus solitarius –> chemo and baroreceptors aortic arch
  • Jugular foramen
62
Q

Cranial Nerve 11

  • Name
  • Sensory, motor, both?
  • Function?
  • Nuclei
  • Exit point from skull?
A
  • Spinal accessory nerve
  • motor only
  • innervation to trapezius and sternocleidomastoid
  • Spinal accessory nucleus in cervical spinal cord –> rootlets from nucles exit lateral cord between dorsal and ventral horns –> ascend and enter skull via foramen magnum –> exit skull through jugular foramen –> innervate muscles
  • Jugular foramen
63
Q

What would a lesion of LMN for CN 11 present with?

A

Ipsilateral weakness of shoulder shrug or arm elevation (trapezius) and weakness of head turning away from the lesion (i.e. if lesion is on left, then difficulty turning head to right b/c sternocleidomastoid turns head in contralateral direction)

64
Q

Cranial Nerve 12

  • Name
  • Sensory, motor, both?
  • Function?
  • Location?
  • Nuclei?
  • Upper motor neuron path of travel to nucleus?
  • Exit foramen?
A
  • Hypoglossal nerve
  • Somatic motor only
  • Innervate extrinsic and intrinsic muscles of tongue
  • Ventral medulla between inferior olive and pyramids
  • Hypoglossal nucleus near the midline in medulla on floor of 4th ventricle
  • Primary motor cortex –> descend via corticobulbar tract –> decussate –> innervate LMNs of hypoglossal nucleus
  • Hypoglossal foramen
65
Q

For the hypoglossal nerve, a lesion in the primary motor cortex or internal capsule will cause […] tongue weakness, while lesions of the hypoglossal nucleus, exiting fascicles, or nerve cause […] tongue weakness

A
  • contralateral
  • ipsilateral

Neuroscience and Head and Neck Anatomy (40 decks)

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