Cervical Plexus and CN I, II, IV, VIII, XI, X Flashcards
What spinal nerves comprise the cervical plexus?
Ventral rami of spinal nerves C1-C5
What does the cervical plexus innervate?
Neck
Thoracic Cavity
Diaphragmatic muscles
Where is the cervical plexus located?
Deep to the SCM
How many major branches does the cervical plexus have?
6
What are the major branches of the cervical plexus?
Sensory, Motor, Mixed
- Lesser occipital n.
- Greater auricular n.
- Supraclavicular n.
- Phrenic n.
- Ansa cervicalis
What cranial nerve is the cervical plexus associated with?
CN XII
What are the 4 major cutaneous branches of the cervical plexus? (sensory)
Lesser occipital n.
Great auricular n.
Transverse cervical n.
Supraclavicular n.
`Lesser occipital n.
One of the major cutaneous branches of the cervical plexus
C2
Skin of neck and scalp posterior to ear
Great auricular n.
One of the major cutaneous branches of the cervical plexus
C2, C3
Skin of inferior parotid region, ear, mastoid area
Transverse cervical n.
One of the major cutaneous branches of the cervical plexus
C2, C3
Lateral and anterior parts of neck
Supraclavicular n.
One of the major cutaneous branches of the cervical plexus
C3, C4
Skin over clavicle and shoulder
What is Erb’s point?
The point where the 4 branches of the cervical plexus emerge from behind the SCM
What is the clinical significance of Erbs’ point?
Surgical landmark
Injury can occur there during birth or a fall on the shoulder
Phrenic n.
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
Ansa Cervicalis
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
Which cranial nerve is within the carotid sheath or a content of the sheath?
CN X
What branch of the cervical plexus is embedded in the carotid sheath?
Ansa cervicalis
Which cranial nerve is associated with the carotid sheath?
CN XII runs with C1
SOO close together that they are wrapped together at some point
Which cranial nerves are special sensory nerves only?
I
II
VIII
Which cranial nerves are motor nerves only?
III IV VI XI XII
Which cranial nerves are mixed nerves (both sensory and motor)?
V
VII
IX
X
Which cranial nerves contain parasympathetic motor fibers?
III
VII
IX
X
Which cranial nerve is mixed with only somatic motor and sensory? (i.e. no parasympathetic)
V
Olfactory Nerves (CN I): course and distribution
Olfactory nerve cells (hanging through the cribiform plate) > Pass through cribiform plate > Olfactory bulb > Olfactory tract > Olfactory area of the cerebral cortex (temporal lobe)
Olfactory Nerve (CN I) Functional group, Primary function, Origin, Path through skull
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
Optic Nerve (CN II) Functional group, Primary function, Origin, Path through skull
Special Somatic Afferent, Special Sensory
Primary function: Vision
Origin: Ganglion cells of retina
Path through skull: Optic canals of sphenoid
Optic Nerve (CN II): course and distribution
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)
What would a runny nose after head trauma indicate? What nerve would be affected?
Runny nose = CSF leakage
Indicate torn dura mater near cribiform plate
Torn olfactory neurons
CN I
How would vision be affected if you had a lesion on the optic nerve?
Blindness
How would vision be affected if you had a lesion on the optic chiasm?
Bitemporal hemianopsia
How would vision be affected if you had a lesion on the optic tract?
Homonymous hemianopsia
Vestibulocochlear Nerve (CN VIII): course and distribution
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
Vestibulocochlear Nerve (CN VIII) Functional group, Primary function, Origin, Path through skull, Associated Nuclei
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
What is an acoustic neuroma and what can it lead to?
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
Trochlear Nerve (CN IV): course and distribution
Posterior surface of midbrain > Middle cranial fossa > Lateral cavernous sinus > Superior orbital fissure > Superior oblique
Trochlear Nerve (CN IV) Functional group, Primary function, Origin, Path through skull
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
Trochlear Nerve Lesions can cause what?
Dipolopia - double vision
Eye is adducted and elevated
Strabismus
Abducens (Abducent) Nerve (CN VI): course and distribution
Anterior surface of hindbrain, at pontomedullary junction > passes forward with internal carotid artery through cavernous sinus > Enters orbit through superior orbital fissure > Lateral rectus
Abducens Nerve (VI) Functional group, Primary function, Origin, Path through skull
General Somatic Efferent, Somatic Motor
Primary function: Motor to lateral rectus (abduction)
Origin: Abducens nucleus
Path through skull: Superior orbital fissures of sphenoid
Abducens Nerve Lesions
Diplopia
Medial strabismus
What is the cavernous sinus?
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
What nerves pass through the cranial sinus?
III IV V1 V2 VI
And internal carotid artery (ICA)
Accessory Nerves (CN XI): course and distribution
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
Accessory Nerves (CN XI) - CRANIAL ROOT Functional group, Primary function, Origin, Path through skull
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
Accessory Nerves (CN XI) - SPINAL ROOT Functional group, Primary function, Origin, Path through skull
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
Accessory Nerve Lesions
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
Hypoglossal Nerves (CN XII): course and distribution
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
Hypoglossal Nerves (CN XII) Functional group, Primary function, Origin, Path through skull
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
Hypoglossal Nerve Lesions
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)