Cervical Plexus and CN I, II, IV, VIII, XI, X

Question 1

What spinal nerves comprise the cervical plexus?

Answer 1

Ventral rami of spinal nerves C1-C5

Question 2

What does the cervical plexus innervate?

Answer 2

Neck
Thoracic Cavity
Diaphragmatic muscles

Question 3

Where is the cervical plexus located?

Answer 3

Deep to the SCM

Question 4

How many major branches does the cervical plexus have?

Answer 4

6

Question 5

What are the major branches of the cervical plexus?

Answer 5

Sensory, Motor, Mixed

• Lesser occipital n.
• Greater auricular n.
• Supraclavicular n.
• Phrenic n.
• Ansa cervicalis

Question 6

What cranial nerve is the cervical plexus associated with?

Answer 6

CN XII

Question 7

What are the 4 major cutaneous branches of the cervical plexus? (sensory)

Answer 7

Lesser occipital n.
Great auricular n.
Transverse cervical n.
Supraclavicular n.

Question 8

`Lesser occipital n.

Answer 8

One of the major cutaneous branches of the cervical plexus

C2
Skin of neck and scalp posterior to ear

Question 9

Great auricular n.

Answer 9

One of the major cutaneous branches of the cervical plexus

C2, C3
Skin of inferior parotid region, ear, mastoid area

Question 10

Transverse cervical n.

Answer 10

One of the major cutaneous branches of the cervical plexus

C2, C3
Lateral and anterior parts of neck

Question 11

Supraclavicular n.

Answer 11

One of the major cutaneous branches of the cervical plexus

C3, C4
Skin over clavicle and shoulder

Question 12

What is Erb’s point?

Answer 12

The point where the 4 branches of the cervical plexus emerge from behind the SCM

Question 13

What is the clinical significance of Erbs’ point?

Answer 13

Surgical landmark

Injury can occur there during birth or a fall on the shoulder

Question 14

Phrenic n.

Answer 14

Mixed - sensory and motor
Very important nerve - you’ll die without this

• C3, C4, C5
• Runs along anterior scalene muscle, deep to the carotid sheath
• Sensory and motor to DIAPHRAGM

Question 15

Ansa Cervicalis

Answer 15

Motor
Most complicated because of the loop

• Loop of nerve fibers
• – Superior and inferior roots
• – C1, C2, C3
• Travels with CN XII
• Innervates 3 of 4 infrahyoid muscles
• – Omohyoid
• – Sternohyoid
• – Sternothyroid

Question 16

Which cranial nerve is within the carotid sheath or a content of the sheath?

Answer 16

CN X

Question 17

What branch of the cervical plexus is embedded in the carotid sheath?

Answer 17

Ansa cervicalis

Question 18

Which cranial nerve is associated with the carotid sheath?

Answer 18

CN XII runs with C1

SOO close together that they are wrapped together at some point

Question 19

Which cranial nerves are special sensory nerves only?

Answer 19

I
II
VIII

Question 20

Which cranial nerves are motor nerves only?

Answer 20

III
IV
VI
XI
XII

Question 21

Which cranial nerves are mixed nerves (both sensory and motor)?

Answer 21

V
VII
IX
X

Question 22

Which cranial nerves contain parasympathetic motor fibers?

Answer 22

III
VII
IX
X

Question 23

Which cranial nerve is mixed with only somatic motor and sensory? (i.e. no parasympathetic)

Answer 23

V

Question 24

Olfactory Nerves (CN I): course and distribution

Answer 24

Olfactory nerve cells (hanging through the cribiform plate) > Pass through cribiform plate > Olfactory bulb > Olfactory tract > Olfactory area of the cerebral cortex (temporal lobe)

Question 25

``` Olfactory Nerve (CN I) Functional group, Primary function, Origin, Path through skull ```

Answer 25

Special Visceral Afferent, Special Sensory Primary function: Olfaction Origin: Olfactory receptor cells in nasal mucosa Path through skull: Olfactory foramina of cribiform plate of ethmoid

Question 26

``` Optic Nerve (CN II) Functional group, Primary function, Origin, Path through skull ```

Answer 26

Special Somatic Afferent, Special Sensory Primary function: Vision Origin: Ganglion cells of retina Path through skull: Optic canals of sphenoid

Question 27

Optic Nerve (CN II): course and distribution

Answer 27

Rods and cones to ganglion cells of retina > Optic canal > Optic chiasm (nasal fibers flip to opposite side; temporal fibers stay on the same side) > Optic tract > Lateral geniculate body (thalamus) > Visual cortex of the brain (occipital lobe)

Question 28

What would a runny nose after head trauma indicate? What nerve would be affected?

Answer 28

Runny nose = CSF leakage Indicate torn dura mater near cribiform plate Torn olfactory neurons CN I

Question 29

How would vision be affected if you had a lesion on the optic nerve?

Answer 29

Blindness

Question 30

How would vision be affected if you had a lesion on the optic chiasm?

Answer 30

Bitemporal hemianopsia

Question 31

How would vision be affected if you had a lesion on the optic tract?

Answer 31

Homonymous hemianopsia

Question 32

Vestibulocochlear Nerve (CN VIII): course and distribution

Answer 32

Two sets of sensory fibers (vestibular and cochlear) > leave anterior surface of brain at the pontomedullary junction > cross posterior cranial fossa > internal acoustic meatus with facial nerve

Question 33

``` Vestibulocochlear Nerve (CN VIII) Functional group, Primary function, Origin, Path through skull, Associated Nuclei ```

Answer 33

Special Somatic Afferent, Special Sensory Primary function: Vestibular branch (balance and equlibrium); Cochlear branch (hearing) Origin: Vestibular and cochlear ganglia (where the cell bodies are) Path through skull: Internal acoustic meatus of temporal Associated Nuclei: To vestibular and cochlear nuclei

Question 34

What is an acoustic neuroma and what can it lead to?

Answer 34

Benign tumor of Schwann cells - Hearing loss and gait ataxia - Block CSF drainage of 4th ventricle = hydrocephaly - -- Vomiting, loss of consciousness and death if it compresses important structures

Question 35

Trochlear Nerve (CN IV): course and distribution

Answer 35

Posterior surface of midbrain > Middle cranial fossa > Lateral cavernous sinus > Superior orbital fissure > Superior oblique

Question 36

``` Trochlear Nerve (CN IV) Functional group, Primary function, Origin, Path through skull ```

Answer 36

General Somatic Efferent, Somatic Motor Primary function: Motor to superior oblique (down and out, depression and abduction) Origin: Trochlear nucleus Path through skull: Superior orbital fissure of sphenoid

Question 37

Trochlear Nerve Lesions can cause what?

Answer 37

Dipolopia - double vision Eye is adducted and elevated Strabismus

Question 38

Abducens (Abducent) Nerve (CN VI): course and distribution

Answer 38

Anterior surface of hindbrain, at pontomedullary junction > passes forward with internal carotid artery through cavernous sinus > Enters orbit through superior orbital fissure > Lateral rectus

Question 39

``` Abducens Nerve (VI) Functional group, Primary function, Origin, Path through skull ```

Answer 39

General Somatic Efferent, Somatic Motor Primary function: Motor to lateral rectus (abduction) Origin: Abducens nucleus Path through skull: Superior orbital fissures of sphenoid

Question 40

Abducens Nerve Lesions

Answer 40

Diplopia | Medial strabismus

Question 41

What is the cavernous sinus?

Answer 41

Venous blood flow in a little pouch surrounding the sella turcica - Receives blood from the superior and inferior ophthalmic veins - Drains into the superior and inferior petrosal sinuses

Question 42

What nerves pass through the cranial sinus?

Answer 42

``` III IV V1 V2 VI ``` And internal carotid artery (ICA)

Question 43

Accessory Nerves (CN XI): course and distribution

Answer 43

Cranial Root: Anterior surface of medulla - Runs laterally in posterior cranial fossa and joins spinal root Spinal Root: Anterior gray horn of upper 5 segments of spinal cord - Ascends along spinal cord - Enters skill through foramen magnum - Turns laterally to join cranial root The 2 roots unite, leaving the skull through the jugular foramen, then roots separate. - Cranial root joins vagus (pharyngeal plexus) - Spinal to SCM and trapezius

Question 44

``` Accessory Nerves (CN XI) - CRANIAL ROOT Functional group, Primary function, Origin, Path through skull ```

Answer 44

Special Visceral Efferent, Branchial Motor Primary function: Motor to muscles of soft palate, pharynx, and intrinsic muscles of larynx (via vagus, pharyngeal plexus) Origin: Nucleus ambiguus Path through skull: Jugular foramina between occipital and temporal bones

Question 45

``` Accessory Nerves (CN XI) - SPINAL ROOT Functional group, Primary function, Origin, Path through skull ```

Answer 45

General Somatic Efferent, Somatic Motor Primary function: Motor to SCM and trapezius Origin: Spinal accessory nucleus, spinal cord segments C1-C5 Path through skull: Jugular foramina between occipital and temporal bones

Question 46

Accessory Nerve Lesions

Answer 46

Lead to partial paralysis of trapezius - Drooping of shoulder on the affected side - Also innervated by C3-C5 Lead to complete (flaccid) paralysis of SCM - Torticollis (wry neck) - -- Unilateral injury - difficulty turning head to opposite side - -- Bilateral injury, difficult holding head up - Only innervated by CN XI

Question 47

Hypoglossal Nerves (CN XII): course and distribution

Answer 47

Anterior surface of medulla as rootlets > Rootlets join and form CN XII > Travel through hypoglossal canal > Enter the root of the tongue superior to the hyoid bone and lateral to hyoglossus

Question 48

``` Hypoglossal Nerves (CN XII) Functional group, Primary function, Origin, Path through skull ```

Answer 48

General Somatic Efferent, Somatic Motor Primary function: - Motor to all intrinsic and extrinsic muscles of the tongue, except palatoglossus (innervated by CN X) - Controls shape and movement of the tongue Origin: Hypoglossal nucleus Path through skull: Hypoglossal canals of occipital bone

Question 49

Hypoglossal Nerve Lesions

Answer 49

Supranuclear lesions (i.e. in the brain) cause contralateral paralysis Peripheral lesions cause ipsilateral paralysis - Unilateral injury, the tongue deviates to the side of the lesion on protrusion; "lick your wounds" (If lesion is on CN XII)