Anatomy of Cranial Nerves Flashcards
1
Q
What is the function and modality of cranial nerve I?
A
Olfactory nerve- smell
Special sensory
2
Q
Where is the extra cranial part of CN I?
A
Lays within olfactory mucosa in nasal cavity
3
Q
What is the cranial foramina of CN I?
A
Cribriform plate of the ethmoid bone
Lies within anterior cranial fossa
4
Q
Where is the intracranial part of CN I where is connects with the CNS?
A
Olfactory nerves synapse in the olfactory bulb
Then pass through the olfactory tract to cortical areas
5
Q
What is the function and modality of CN II?
A
Optic nerve- vision
Special sensory
6
Q
Where is the extra cranial part of CN II?
A
Neurons of retina travel posteriorly via optic nerve from posterior hemisphere of eye through orbit
7
Q
What is the cranial foramina for CN II?
A
Optic canal in middle cranial fossa
8
Q
Where is the intracranial part of CN II?
A
Optic nerve passes around pituitary stalk to optic chasm to form the optic tract
9
Q
Where does CN II connect with the CNS?
A
Diencephalon
10
Q
What are the only 2 structures running through the optic canal?
A
Optic nerve and ophthalmic artery
11
Q
How is CN I clinically tested?
A
Not routinely tested!
Can ask patient to smell familiar smell whilst covering contralateral nostril
12
Q
How is CN II clinically tested?
A
5 ways: Acuity (Snellen chart) Colour (Ishihara plates for colour blindness) Fields (Four quadrants) Reflexes (Pupillary light reflexes) Fundoscopy
13
Q
What is the function and modality of CN III?
A
Oculomotor nerve Eye movement (motor) Pupil constriction (parasympathetic)
14
Q
Where does CN III connect with the CNS?
A
Midbrain (mesencephalon)
15
Q
Where is the intracranial part of CN III?
A
Towards the orbit in the lateral wall of the cavernous sinus
16
Q
What is the cranial foramina for CN III?
A
Superior orbital tissue (SOF)
17
Q
What is the extra cranial part of CN III?
A
Passed from SOF into orbit to supply all extra ocular muscles except 2
Parasympathetic part synapses in ciliary ganglion
18
Q
What is the function and modality of CN IV?
A
Trochlear nerve Eye movement (Motor)
19
Q
Where does CN IV connect with the CNS?
A
Midbrain (mesencephalon)
20
Q
Where is the intracranial part of CN IV?
A
Nerve travels towards the orbit in the lateral wall of the cavernous sinus
21
Q
What is the cranial foramina for CN IV?
A
Superior orbital fissure (SOF)
22
Q
Where is the extra cranial part of CN IV?
A
Passes through SOF into orbit and supplies only superior oblique muscle
23
Q
What is the function and modality of CN VI?
A
Abducent nerve Eye movement (motor)
24
Q
Where does CN VI connect with the CNS?
A
Pontomedullary junction
25
Where is the intracranial part of CN VI?
Travels towards orbit within cavernous sinus
26
What is the cranial foramina for CN VI?
Superior orbital fissure (SOF)
27
Where is the extra cranial part of CN IV?
Passes through SOF into orbit and supplies only lateral rectus
28
How are eye movements tested?
The 'H' test
29
What is the function and modality of CN VIII?
Vestibulocochlear nerve
| Hearing and balance (special sensory)
30
Where is the extra cranial part of CN VIII?
Axons from cochlear and vestibular apparatus
31
What is the cranial foramina for CN VIII?
Internal acoustic meatus
| In posterior cranial fossa
32
Where is the intracranial part of CN VIII?
Travels posteromedially from internal acoustic to pontomedullary junction
33
Where does CN VIII connect with the CNS?
Pontomedullary junction
34
How do you clinically test VIII?
Rinne and Weber test
35
What is the function and modality of CN XI?
Spinal accessory nerve
| Motor- sternocleidomastoid and trapezius muscle
36
Where does CN XI connect with the CNS?
Cervical spinal cord
37
Where is the intracranial part of CN XI?
Ascends through foramen magnum then travels towards jugular foramen in posterior cranial fossa
38
What is the cranial foramina for CN XI?
Jugular foramen in posterior cranial fossa
39
Where is the extra cranial part of CN XI?
Axons supply SCM on deep surface, then continue across posterior triangle to supply trapezius
40
How do you clinically test XI?
Ask patient to shrug shoulder
| Ask patient to turn head to flex neck and turn towards the opposite side
41
What is the function and modality of CN XII?
Hypoglossal nerve
| Motor ( all muscles of the tongue except palatoglossus)
42
Where does CN XII connect with the CNS?
Via rootlets lateral to pyramids of medulla oblongata
43
Where is the intracranial part of CN XII?
Passes anteriorly to hypoglossal canal
44
What is the cranial foramina for CN XII?
Hypoglossal canal in posterior cranial fossa
45
Where is the extra cranial part of CN XII?
Descends lateral to carotid sheath
| At level of hyoid it turns anteriorly towards lateral aspect of tongue
46
How do you clinically test XII?
Ask patient to stick tongue straight out
| Tongue tip will point towards side of injured nerve
47
Which cranial nerves are more complex?
Trigeminal
Facial
Glossopharyngeal
Vagus
48
What are the 3 divisions of CN V (Trigeminal) and what are their modalities?
CNV1- Ophthalmic- Sensory
CNV2- Maxillary- Sensory
CNV3- Mandibular- Sensory and Motor
49
Where does CN V connect with the CNS?
Pons (laterally)
50
Where is the intracranial part of CN V?
Inferior to edge of tentorium cerebella between posterior and middle cranial fossae
51
What are the cranial foramina for the 3 divisions of CN V?
CN V1- Superior orbital fissure
CNV2- Foramen rotundum
CNV3- Foramen ovale
52
Where is the extra cranial part of CN XII?
Sensory axons from all 3 divisions- from superficial and deep facial structures posteriorly towards respective cranial foramen
Motor axons- from CNV3 flow from foramen ovale towards skeletal muscle they supply
53
What areas of the face does CNV1 supply?
Upper eyelid
Cornea
All the conjunctiva
Skin of root/bridge/tip of nose
54
What areas of the face does CNV2 supply?
Skin of lower eyelid
Skin of maxilla
Skin of ala of nose
Skin/mucosa of upper lip
55
What areas of the face does CNV3 supply?
Skin over mandible and TMJ
56
What are the motor functions of CNV3 mandibular nerve?
Innervation of 3 pairs of jaw closing muscles- master, temporalis and medial pterygoid
Innervation of 1 pair of jaw opening muscles- lateral pterygoid
Tensor veli palatini and tensor tympani
57
How do you clinically test CNV?
Sensory: ask patient to close eyes and gently brush skin in each dermatome with fine top of cotton wool, compare both sides
Motor: Palpate strength of contraction of masseter & temporalis by asking patient to clench teeth
Ask patient to open jaw against resistance
58
What is the function and modality of CN VII?
Facial nerve- special sensory (taste), motor and parasympathetic
59
Where does CN VII connect with the CNS?
Anterolateral at pontomedullary junction
60
What is the cranial foramina for CN VII?
Temporal bone
Internal acoustic meatus (in)
Stylomastoid foramen (out)
61
Where is the extra cranial part of CN VII?
Most somatic motor axons pass into parotid gland then into 1 of 5 branches that supply muscles of facial expression
62
Where is the course of the facial nerve in the base of skull?
Through the petrous part of temporal bone
63
What does the branch of CN VII (chorda tympani) innervate?
Taste buds on anterior 2/3rds of tongue
| Parasympathetic supply to submandibular & sublingual glands (salivation)
64
Which muscle in the inner ear is innervated by CN VII?
Stapedius muscle
| Reduces stapes movement to protect the internal ear from excessive noise
65
The chorda tympani joins the lingual nerve (CNV3) to innervate what?
Anterior 2/3rds of tongue and parasympathetic fibres to glands of submandibular and sublingual
66
How do you clinically test CN VII?
```
Ask patient to:
Raise eyebrows (frontalis)
Close eyes tightly (orbicularis oculi)
Smile (elevators of lips)
Puff out cheeks and hold air (orbicularis oris)
```
67
What is the function and modality of CN IX?
```
Glossopharyngeal nerve
Special sensory (Taste)
Sensory
Motor
Visceral afferent
Parasympathetic
```
68
Where does CN IX connect with the CNS?
Lateral aspect of superior medulla oblongata
69
What is the cranial foramina for CN IX?
Jugular foramen
70
Where is the extra cranial part of CN IX?
```
Descends towards pharynx and mouth
To stylopharyngeus muscle
To parotid gland
From pharyngeal mucosa
From carotid body and sinus
From posterior 1/3rd of tongue
```
71
Where is the intracranial part of CN IX?
Directly towards jugular foramen in posterior cranial fossa
72
Which areas does CN IX innervate in general sensory?
```
Posterior 1/3rd of tongue
Mucosa of most of nasopharynx and oropharynx
Mucosa of some of laryngopharynx
Palatine tonsil
Eustachian tube
Middle ear cavity
```
73
CN IX innervates what with special sensory?
Vallate papillae (taste buds) of posterior 1/3rd of tongue
74
CN IX innervates what with visceral afferent?
Carotid sinus baroreceptors
| Carotid body chemoreceptors
75
CN IX innervates what with somatic motor?
Stylopharyngeus
76
CN IX innervate what with parasympathetic?
Secretomotor to parotid gland (salivary)
77
How do you clinically test CN IX?
Gag reflex in general sensory
| Referred pain from pharynx to ear and vice versa
78
What is the function and modality of CN X?
Vagus nerve
| Sensory, motor, visceral afferent and parasympathetic
79
Where does CN X connect with the CNS?
Lateral aspect of medulla oblongata
| Immediately inferior to CN IX
80
Where is the intracranial part of CN X?
Directly towards jugular foramen in the posterior cranial fossa
81
What is the cranial foramina for CN X?
Jugular foramen
82
Where is the extra cranial part of CN X?
Axons supply lots of structures between the palate and the midgut
83
Which anatomical structures lie close to the CN X in the neck?
CN X runs within the carotid sheath
| Posterior to and between the common carotid artery and internal jugular vein
84
Which anatomical structures lie close to the CN X in the thorax?
CN X runs inferiorly into the thorax then gives off the recurrent laryngeal nerve to turn back superiorly to supply the muscles of the larynx.
85
Which anatomical structures lie close to the left and right recurrent laryngeal nerves?
```
Left= curves under arch of aorta
Right= curves under right subclavian artery
```
86
Which anatomical structures lie close to CN X in the abdomen?
Both CNs X pass onto surface of stomach
| Vagus nerves very last parasympathetic axons pass to the splenic flexure of the colon
87
How do you clinically test CN X?
Ask patient to say 'ahhhh"- muscles of palate- uvula should lift straight in the midline
Unilateral pathology will pull uvula away from non-functioning side
Ask patient to swallow water- splutter may suggest abnormal swallow
Listen to speech- hoarseness may suggest abnormal function of laryngeal muscles
