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Head and Neck > Introduction to Cranial Nerves > Flashcards

Introduction to Cranial Nerves Flashcards

1
Q

What are the cranial nerves?

A

Cranial nerves are 12 nerves that arise directly from cranial nerve nuclei in the brainstem as opposed to the spinal cord. The cranial nerves can have motor, sensory, and parasympathetic fibers as integral components of their fiber composition, but never sympathetic.

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2
Q

What are common to cranial nerve and spinal nerve?

A

Cranial and spinal nerves can carry both somatic and visceral sensory, but as far as autonomics, cranial nerves can only have parasympathetic fibers as an integral component of their composition. Sympathetic fibers can only “hitch a ride” on the track of cranial nerves.

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3
Q

Which cranial nerves are purely sensory?

A 
Olfactory Nerve (CN I)
Optic Nerve (CN II)
Vestibulocochlear Nerve (CN VIII)
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4
Q

Which cranial nerves carry special sensory component?

A

The term “special” refers to fiber types that are carried by spinal nerves only. These include Special Somatic Afferent (vision and hearing) Special Visceral Afferent (smell and taste) and Special Visceral Efferent (striated muscles in the face). The nerves that carry either of the special afferent components include: Optic Nerve CN II (SSA)
Vestibulocochlear Nerve CN VIII (SSA)
Olfactory Nerve CN I (SVA)
Facial Nerve CN VII (SVA)
Vagus CN X (SVA)
Glossopharyngeal CN IX (SVA)

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5
Q

Which cranial nerves carry parasympathetic nerve fibers?

A 
Oculomotor Nerve (CN III)
Facial Nerve (CN VII)
Glossopharyngeal NErve (CN IX) 
Vagus Nerve (CN X)
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6
Q

What and where are the sensory ganglia of the cranial nerves equivalent to dorsal root ganglion of the spinal nerve?

A

The cranial nerve sensory ganglia are equivalent to dorsal root ganglion (spinal ganglion) and are located outside of the brainstem. They have a peripheral process associated with a receptor and a central process that terminates in a cranial nerve sensory nucleus in the brainstem.

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7
Q

Describe the 4 cranial parasympathetic ganglia and with what cranial nerve each ganglion is associated.

A 
"COPS Ganglia" 
Ciliary (CN III Oculomotor Nerve)
Otic (CN IX Glossopharyngeal Nerve)
Pterygopalatine (CN VII Facial Nerve)
Submandibular (CN VII Facial Nerve)
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8
Q

Are the sympathetic nerves in the head preganglionic or postganglionic?

A

Sympathetics in the head are always postganglionic.

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9
Q

What is Horner’s syndrome? How is it characterized clinically?

A

Horner’s syndrome is caused by an interruption of the cervical sympathetic trunk. It presents with constriction of the pupil (miosis), drooping of the superior eyelid (ptosis), redness and increased temperature of the skin (vasodilation), and absence of sweating (anhydrosis).

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10
Q

What function does the sphincter pupillae serve? What does the ciliary muscle do when it contracts? What is the process of accommodation in the eye?

A

Sphincter pupillae is a ring of smooth muscles around the iris that narrows the diameter of the iris. The ciliary muscle changes the shape of the lens of the eye by pulling on the sides of it. This controls accommodation (focusing) when viewing objects at different distances.

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11
Q

Which cranial nerve exits the DORSAL side of the brainstem?

A

Trochlear Nerve (CN IV)

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12
Q

How will a patient with an abducens nerve lesion present clinically?

A

The patient will be unable to abduct the eye.

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13
Q

How would a CN XI lesion present clinically?

A

CN XI is the spinal accessory nerve that innervates the trapezius muscle and the sternocleidomastoid muscle. When a lesion occurs, the patient will present with shoulder droop.

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14
Q

What is anosmia?

A

Anosmia is the loss of sense of smell. The Olfactory Nerve (CN I) is most easily torn in trauma and will present with CSF dripping from the nose.

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15
Q

What is the sensory ganglion of CN V?

A

The Trigeminal Ganglion are the cell bodies of origin for sensory fibers. Located on petrous ridge of temporal bone.

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16
Q

Which divisions of CN V are purely sensory? Which division carries motor fibers?

A

The ophthalmic and maxillary divisions of CN V (trigeminal nerve) are purely sensory. The mandibular division is the only division to carry motor fibers.

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17
Q

Through what opening does the facial nerve exit the cranial cavity? What other cranial nerve exits
the cranial cavity through this opening? Through what opening does the facial nerve exit the base of
the skull?

A

The facial nerve (CN VII) exits the cranial cavity via the internal acoustic meatus. The vestibulocochlear nerve also exits the cranial cavity through the acoustic meatus. The facial nerve exits through the stylomastoid foramen at the base of the skull.

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18
Q

What is the sensory ganglion for the facial nerve? Where is this ganglion located in the temporal
bone?

A

All sensory fibers for the facial nerve arise from the geniculate ganglion, which is located in the bend of the facial canal in the temporal bone posterior to the middle ear.

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19
Q

Which cranial nerves carry taste sensation?

A 
Facial Nerve (CN VII)
Glossopharyngeal (CN IX) 
Vagus Nerve (CN X)
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20
Q

opening for V1

A

superior orbital fissure

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21
Q

opening for V2

A

foramen rotundum

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22
Q

opening for V3

A

foramen ovale

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23
Q

What are the differences between cranial nerves and spinal nerves? (2 major differences)

A
  • Cranial nerves NEVER contain sympathetic fibers as integral component (spinal nerves typically contain postganglionic sympathetic, as well as somatic motor and somatic sensory)
  • Cranial nerves come from Cranial nerve nuclei (spinal nerves come from dorsal/ventral/lateral horns of the spinal cord)
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24
Q

Name of CN I and bony foramen it travels through

A

CN I = Olfactory nerve.

Foramina in Cribiform plate of Ethmoid bone

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25
Q

Name of CN II and bony foramen it travels through

A

CN II = Optic nerve

Optic Canal

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26
Q

Name of CN III and bony foramen it travels through

A

CN III = Oculomotor nerve

Superior Orbital fissure

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27
Q

Name of CN IV and its bony foramen of cranial exit

A

CN IV = Trochlear nerve. Superior Orbital fissure

28
Q

Name CN V, it’s (3) major branches, and bony foramina they travel through

A

CN V = Trigeminal nerve. (3) major branches supplying facial skin:

  • V1 = Opthalmic (Superior Orbital fissure)
  • V2 = Maxillary. (Foramen rotundum)
  • V3 = Mandibular (Foramen ovale)
29
Q

Name of CN VI and bony foramen it travels through

A

CN VI = Abducent nerve. Superior orbital fissure

30
Q

Name of CN VII and bony foramen it travels through. Which fibers of CN VII then go on to exit via another bony foramen?

A

CN VII = Facial nerve. ALL fibers of CN VII exit cranial cavity via Internal acoustic meatus, entering the temporal bone. Then:
-Somatic motor fibers of CN VII take a sharp turn at the facial canal of the temporal bone to exit at the sylomastoid foramen

31
Q

Name of CN VIII and bony foramen it travels through

A

CN VIII = Vestibulocochlear nerve

Internal acoustic meatus (after exit, then divides into 2 components: Vestibular and Cochlear)

32
Q

Name of CN IX and bony foramen it travels through

A

CN IX = Glossopharyngeal nerve

Jugular foramen

33
Q

Name of CN X and bony foramen it travels through

A

CN X = Vagus nerve

Jugular foramen

34
Q

Name of CN XI and bony foramen it travels through

A

CN XI = Spinal Accessory nerve

Jugular foramen

35
Q

Name of CN XII and bony foramen it travels through

A

CN XII = Hypoglossal nerve

Hypoglossal canal

36
Q

Which (5) Cranial nerves are purely motor?

A
  • Oculomotor nerve (CN III)
  • Trochlear nerve (CN IV)
  • Abducens nerve (CN VI)
  • Spinal Accessory nerve (CN XI)
  • Hypoglossal nerve (CN XII)
37
Q

What are branchial motor fibers? Which (4) cranial nerves carry branchial motor component?

A

branchial motor: motor fibers of voluntary (striated) muscle going specifically to the muscles of mastication. These muscles have embryological origin from the pharyngeal arches.

CN V, CN VII, CN IX, and CN X (5, 7, 9 and 10) are mixed nerves with both somatic (branchial) motor and somatic (general) sensory components, and each nerve supplies different derivatives of a diff pharyngeal arch

38
Q

How do parasympathetic nerves in the head differ from those in the body?

A

Parasympathetics in head (all but Vagus nerve) synapse in a named parasympathetic ganglia (“COPS”). Different from parasympathetics in rest of body that synapse in the wall of the organ

39
Q

What is the brainstem’s equivalent of dorsal, ventral, and lateral horns?

A

~Dorsal horn = Cranial Nerve Sensory Nucleus
(where the CENTRAL process of Cranial Nerve Sensory Ganglia terminate)
~Ventral horn = Cranial Nerve Motor Nuclei
(somatic motor fibers)
~Lateral horn = Parasympathetic Nuclei

40
Q

What cranial nerve do most cranial postganglionic parasympathetic fibers hitch hike along to reach their target?

A

CN V (Trigeminal System)

41
Q

What is the superior cervical ganglion? How are postganglionic fibers from this ganglion distributed to the head and neck?

A

Preganglionic SYMPATHETIC fibers (from T1-T4) ascend in sympathetic chain and synapse on postganglionics in the Superior Cervical Ganglion. From there (3) ways postganglionic fibers go to head/neck:

1) external carotid artery–follow its branches to reach target organs
2) follow internal carotid artery into cranium, then hitch hike with branches of Trigeminal system
3) travel on their own before joining with other nerves

42
Q

Trace the path of CN III parasympathetics from the brainstem to their targets (sphincter pupillae and ciliaris muscles)

A

[These are the fibers of Oculomotor n. that act on the pupils and adjust focus of the lens]

  1. Cell bodies in Edinger Westphal (accessory oculomotor) nucleus
  2. Synapse on postganglionics in Ciliary Ganglion
  3. Post-g’s travel directly to the sphincter pupillae and ciliaris mm of the eye via Short Ciliary nn (branches of V1)
43
Q

How does an oculomotor lesion present? How will the pupil and upper eyelid appear?

A

Dilated pupil, Ptosis (droopy upper eyelid), pupil directed “down and out”

44
Q

How will a patient with a trochlear nerve lesion present clinically?

A

Patient will be unable to look down when the eye is adducted

45
Q

What 2 openings in the skull does CN XI travel through?

A

Enters skull: Foramen magnum
Exits skull: Jugular foramen

[Expl: Spinal Accessory n (CN XI) is weird in that its cell bodies of origin are in the spinal cord. It ascends through skull (foramen magnum) only to cruise through & exit again (jugular foramen) to supply trapezius and sternocleidomastoid.]

46
Q

How would a Hypoglossal nerve lesion present clinically?

A

The patient’s protruded tongue will deviate to the affected side

47
Q

CN I opening

A

cribriform plate of ethmoid bone

48
Q

CN II opening

A

Optic canal

49
Q

CNIII opening

A

superior orbital fissure

50
Q

CN IV opening

A

superior orbital fissure

51
Q

CN V opening

A

V1-superior orbital fissure
V2-foramen rotundum
V3-foramen ovale

52
Q

CN VI opening

A

(inside cranial sinus) superior orbital fissure

53
Q

CN VII opening

A

internal acoustic meatus

54
Q

CN VIII opening

A

internal acoustic meatus

55
Q

CN IX opening

A

jugular foramen

56
Q

CN X opening

A

jugular foramen (with internal jugular vein and common carotid artery)

57
Q

CN XI opening

A

foramen magnum and then back out through jugular foramen

58
Q

CN XII opening

A

Hypoglossal cannal

59
Q

What nerve carries somatic sensory information from the face?

A

Trigeminal nerve (CN V)

60
Q

What are the 3 divisions of CN V? What areas of the face and head do they innervate?

A 
V1 = Opthalmic - forehead to lateral corner of eyes (going right under eyes to top of nose)
V2 = Maxillary - between lateral corners of eyes and corners of mouth (cheek and upper jaw)
V3 = Mandibular - mandible (lower jaw); makes "smiley face" shape going up from mouth in front of ear
61
Q

What opening in the skull does each of the 3 divisions of the Trigeminal nerve pass through?

A
  • Opthalmic (V1) - passes through Superior Orbital fissure to enter the orbit
  • Maxillary (V2) - passes through Foramen Rotundum to enter pterygopalatine fossa.
  • Mandibular (V3) - passes through Foramen Ovale to enter infratemporal fossa
62
Q

What nerve supplies the face with motor innervations (muscles of facial expression)?

A

Facial nerve (CN VII)

63
Q

What 2 branches of the Facial nerve carry parasympathetic fibers? Which cranial parasympathetic ganglion does each branch synapse in?

A

2 pre-gang parasympathetic branches of CN VII =

  • Greater Petrosal nerve. Synapses in Pterygopalatine ganglion
  • Chorda Tympani nerve. Synapses in Submandibular ganglion.

*P and S of ‘COPS’

64
Q

What is the cavernous sinus? What structures pass through the cavernous sinus? What nerves travel through the lateral wall of the cavernous sinus?

A
  • Cavernous sinus is a blood-filled space (due to its main occupants being a large venous plexus) on top of body of sphenoid bone.
  • (3) other non-vein occupants: Abducent Nerve (CN VI), Internal carotid artery, and Carotid Plexus of sympathetic nn (surrounding Int Carotid A)
  • (4) nerves travel in lateral walls: Oculomotor n (CN III), Trochlear n (CN IV), Opthalmic n (CN V1), and Maxillary n (CN V2)
65
Q

What is cavernous sinus thrombosis, and how does it present clinically?

A

Clotting in cavernous sinus, usually as a result of infection in the Danger Triangle–orbit, nasal sinuses, and superior part of face

Head and Neck (22 decks)

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