2. Cranial Nerves (Keim) Flashcards
Name the cranial nerves in order.
OH OH OH, TO TOUCH AND FEEL A GIRLS VAGINA AH HEAVEN.
- CN I. Olfactory
- CN II. Optic
- CN III: Oculomotor.
- CN IV: Trochlear
- CN V: Trigeminal
- CN VI: Abducens
- CN VII: Facial
- CN VIII: Vestibulocochlear
- CN IX: Glossopharyngeal
- CN X: Vagus
- CN XI: Spinal Acessory N.
- CN XII: Hypoglossal N
Name the general function of each cranial N.
Some say marry money, but my brother says big boobs matter most.
- CN I. Olfactory: sensory
- CN II. Optic: sensory
- CN III: Oculomotor: motor
- CN IV: Trochlear: motor
- CN V: Trigeminal: both
- CN VI: Abducens: motor
- CN VII: Facial: both
- CN VIII: Vestibulocochlear: sensory
- CN IX: Glossopharyngeal: both
- CN X: Vagus: both
- CN XI: Spinal Acessory N: motor
- CN XII: Hypoglossal N: motor
There are several fibers within the cranial nerves:
- GSE
- GVE
- SVE
- GSA
- GVA
- SSA
- SVA
What are each?
Efferent (motor)
- GSE (general somatic efferent): send somatic efferent information to somatic muscles
- GVE (general visceral efferent): autonomics to smooth/cardiac muscle and glands
- SVE (branchial or special visceral efferent) send info to muscles derived from pharyngeal arches.
Afferent
- GSA (general somatic afferent): send sensory information to the skin, joint capsule, tendon or muscle from ectoderm
- GVA (general visceral afferent) send sensory information. to visceral structures from endoderm
- SSA (sensory somatic afferent): resp for hearing (CN 8), balance (CN 8) and sight (CN2)
- SVA (special visceral afferent): taste (CN 7, 9, 10) and smell (CN 1)
What is the function, location, and tract of the olfactory nerve (CN I)?
- Function: SVA –smell.
- Location: olfactory organ.
- Tract: cribiform plate (in nasal cavity) to olfactory bulbs (in brain)
Head impact can shear olfactory. N. What can happen?
Pt can become anosmic (complete olfactory loss)
How does our sense of smell change with age?
Gradually decreases with age.
Pts will commonly complain for loss of taste
What is ansomia?
What happens if we have unilateral anosmia?
Causes?
- Anosmia. -> complete olfactory loss.
- Our other nostril can compensate for unilateral anosmia.
- Causes:
- head trauma,
- viral infection
- intracranila lesion
- obstruction of nasal passage
What is CSF rhinorrhea with fracture of cribriform plate?
Tested using?
- Can cause CSF leakage through nose.
- Tested via halo sign: clear drainage that forms ring around blood suggests that it is CSF. Thus, we have damage to meninges
Optic nerve (CN II) function
SSA: vision
What is the pathway for the fibers of the optic nerve into the brain?
ganglion cells in the retina -> leaves bony orbit via optic canal of the sphenoid bone -> enters cranial cavity runnning along middle cranial fossa -> optic chiasm -> optic tract -> fibers terminate LGN of the thalamus ->
- Axons are then sent to the optic radiations -> primary visual cortex.
CN II: clinical correactions
What can compress the optic chiasm?
- Optic chiasm is located near pituitary gland. Thus, pituitary tumors can cause damage.
- Interal carotid a. aneuyrism can compress optic chiasm
What happens if we have damage to optic chiasm?
Bitemporal hemianopia (loss of vision laterally in both visual fields)
Oculomotor nerve (CN III) Functions
GSE and GVE
- GSE: motor innervation to eye muscles:
- superior, medial, and inferior recti m.
- inferior oblique m.
- levator palpebrae superioris m.
- GVE: carries parasympathetic innervation to the pupil and ciliary muscle.
What tract is followed by the oculomotor nerve?
- Leave the midbrain ->
- pierces the dura lateral to diaphragma sellae ->
- runs in lateral wall of cavernous sinus ->
- enters orbit via superior orbital fissure.
What is the function of the trochlear nerve (CN IV)?
GSE
GSE: motor innervation to the superior oblique muscle of the eye.
What is the tract of the trochlear nerve?
- Exits the dorsal surface of the midbrain ->
- Pierces the dura mater at the margin of the tentorium cerebelli ->
- Runs in the lateral wall the cavernous sinus ->
- Enters the orbit via the superior orbital fissure.
What is the only nerve to exit the dorsal surface of the midbrain?
CN IV (trochlear)
What is the function of the abducens nerve (CN VI)?
GSE
Motor innervation to the lateral rectus m. of the eye
What is the tract of the abducens nerve (CN VI)?
- Emerges from the brainstem at the pontomedullary. junction ->
- Goes thru pontine cistern ->
- pierces of the dura covering the clivus ->
- runs in the cavernous sinus near the ICA ->
- enters the orbit by the superior orbital fissure.
Where is the nucleus of the abducens located?
In the pons.
What are the functions of the trigeminal nerve (CN V)?
SVE and GSA
- Special visceral efferent (SVE): motor innervation to the chewing muscles (derived from pharyngeal arch 1).
- General somatic afferen (GSA)t: sensory from face and scalp.
What is the tract for the trigeminal nerve (CN V)?
Both the motor and sensory portions emerge from the lateral aspect of the pon: trigeminal ganglion is located in the trigeminal cave, lateral to cavernous sinus. Then, it branches into:
- V1 (Opthalmic): passes through the cavernous sinus and enters the orbit of the eye via the superior orbital fissure.
- V2 (Maxillary): passes through the cavernous sinus and exits the skull by the foramen rotundum.
- V3 Mandibular: exits the skull by the foramen ovale- > inferotemporal fossa
The motor portion of the trigeminal nerve exists within which branch?
V3 Mandibular
What is the function of the ophthalmic division of the trigeminal nerve (CN V)?
Sensation from:
- cornea,
- skin of forehead and scalp,
- upper eyelid,
- part of nose (bridge -> point)
- part of nasal cavity.
What is the function of the maxillary division of the trigeminal nerve (CN 5)?
Sensation from
- the skin of the face
- lower eyelid
- cheek
- upper lip
- maxillary teeth
- mucosa of nose and
- maxillary sinus.
What is the function of the mandibular division of the trigeminal nerve (CN V)?
Sensation from the :
- skin of the mandible,
- lower lip side of head (?),
- Mandibular teeth,
- TMJ joint,
- part of oral mucosa,
- anterior 2/3 of tongue
motor innervation to the:
- muscles of chewing (as well as the myelohyoid, anterior belly of the digastric, and the tensor tympani).
Facial N (CN VII) Function
SVE, GVE, SVA, GSA
- (SVE) Motor innervation: muscles of facial expression (pharyngeal arch 2)
-
(GVE) Parasympathetic innervation to:
- lacrimal, nasal, and palatine glands
- submandibular and sublingual salivary glands
- (SVA) Taste to: anterior 2/3 of tongue
- (GSA) Sensation to: eternal acoustic meatus
Facial N (CN VII) tract
- Emerges from pontine-medullary junction in brainstem
- Posterior cranial fossa and exits the skull via the internal acoustic meatus
- Enter facial canal, where nerve gives rise to
- Greater petrosal nerve -> parasympathetic inn. to lacrimal gland
- Nerve to stapedius-> motor fibers to stapedius m of middle ear
- Chorda tympani -> parasympathetic to sublingual and submandibular gland.
- Exits via the stylomastoid foramen
- Passes through the parotid gland, where it terminates into 5 branches -> ms of facial expression
- Temporal branch
- Zygomatic branch
- Buccal branch
- Marginal mandibular branch
- Cervical branch
What nerve supplies the lacrimal gland?
Greater petrosal N.
What 2 nerves from off of the facial canal?
- Stapedius n.
- Chorda tympani -> carries taste to 2/3 of tongue and parasympathetic to sublingual and submandibular gland.
Within the parotid gland, the facial nerve terminates by splitting into five branches:
THE ZEBRA BIT MY CHEEK
- Temporal branch
- Zygomatic branch
- Buccal branch
- Marginal mandibular branch
- Cervical branch
Describe the parasympathetic tract of facial N. to lacrimal gland?
- Greater petrosal N. of facial N. originates at geniculate ganglion
- -> petrous part of temporal bone
- -> Axons join the deep petrousal n and forms n. of the pterygoid canal
- -> synapses in pterygopalatine ganglion
Describe the parasympathetic tract of facial N to the salivary gland.
- Chorda tympanic arises from facial n, proximal to the stylomastoid foramen
- -> crosses tympanic cavity in middle ear
- -> Passes through the petrotympanic fissure to join lingual N.
- -> Submandibular ganglion
* sends fibers to anterior 2/3 of tongue w/ synapsing
* synpases -> sends fibers to submandibular gland and sublingual gland
- -> Submandibular ganglion
How can we test facial N?
- Blink reflex will test CN 2 (sensation) and CN 7 (close eyes)
- Sensation test by taste at anterior 2/3 of tongue
- Motor test
- Upper division: wrinkle forhead or close eyes tightly (examiner tries to open)
- Lower division: have pt blow, whistly, smile, suck on straw
- Corneal reflex: Tests CN 5 (V1) and facial nerve.
What is Bell’s Palsy?
- Unilateral facial nerve paralysis.
- Pt cannot blink (cornea is dry), pucker lips, or keep food in mouth while chewing, so they drool.
Vestibulocochlear (CN VIII) Function
SSA
(SSA): hearing and equilibrium
Vestibulocochlear (CN VIII) Tract
- Vestibular N innervates: utricle and saccule
- Cochlear nerve innervates: cochlea.
- Enter skull via the internal acoustic meatus
- Enter brainstem on the pontine-medullary junction
Clinical correlations of CN 8
- Tinnitus
- Disturbance of balance (Vertigo)
- Nystagmus
- Deafness d/t complete cut of CN8
- Acoustic neuroma
How can we test the vestibular division of vesticulocochlear N (CN 8) ?
Vestibular division is responsible for the position of our head in space (d/t. eyes, joints and propioception).
- 1. Romberg’s sign
- 2. Past pointing
- 3. Check for nystagmus
- Romberg’s sign
- Past pointing
- Check for nystagmus
What are these?
Tests for vestibular division of vestibulocochlear N (CN 8).
-
Romberg’s sign: balance, put. feet together, extend arms at sides, eyes closed. Be prepared to catch patient.
* + sign: fall over - Past pointing: finger to nose, first with eyes open then closed [also test of cerebellum]
- Nystagmus- an abnormal eye movement caused by vestibular lesion. When you scan a room, eye moves from target to target, called saccades. Nystagmus -> abnormal saccades.
How can we test the cochlear division of vesticulocochlear N (CN 8)?
- Conduction deafness - sound to ear is impeded d/t wax, otitis media, bony ankylosis, otosclerosis, torn tympanic membrane.
- Whispering or rubbing fingers - rough assessment of acuteness
- Rinne test: confirm with Weber’s test
What is Rhinne’s test and Weber’s test?
What will the results be if: normal, nerve deafness, conduction deafness?
Rinne test will show abnormal ratio of air to bone conduction in conduction deafness.
- Two methods: Put tuning fork on mastoid and next to pinna and ask which sounds louder; or put tuning fork on mastoid and wait until sound decays, then put next to pinna and wait till sound decays. Time the decays.
- Normal:air conduction is twice as long as bone conduction.
- Nerve deafness: the Rinne ratio is normal, but the decay times are diminished.
- Conduction deafness: bone conduction is longer than air.
Weber’s test – confirmatory test. Place tuning fork on top of head.
- The sound lateralizes to the bad ear in conduction deafness
Glossopharyngeal (CN IX) Functions
GSA, GVA, SVA, GVE, SVE
- (GSA) Sensation from ear and external auditory canal, and posterior 1/3 of tongue
- (GVA) Sensory information from oropharynx and carotid body
- (SVA) Taste to the posterior 1/3 of tongue
- (GVE) Parasympathetics to parotid gland
- (SVE) Motor to stylopharyngeus muscles (pharyngeal arch 3)
Glossopharyngeal (CN IX) tract
- Emerges from Medulla
- Exits cranium through jugular foramen
- Passes between the superior and middle pharyngeal constrictors
- Enters oral cavity
Glossopharyngeal is tested at the same time as __________
Vagus N
How can we test the Glossopharyngeal N (CN IX)?
Motor to stylopharyngeus is not directly testable. But, we can test via:
- Secretomotor- parotid reflex
- Sensory- taste on posterior 1/3 of tongue
- General sensation - gag reflex from back of tongue, uvula and pharyngeal walls. However, this overlaps with vagus, therefore not specific.
Glossopharyngeal Neuralgia
eating or swallowing causes intense pain that can lead to suicide
Vagus (CN X) Functions
GSA, GVA, SVA, GVE, SVE
- (GSA) Sensation from: external auditory canal and dura
- (GVA) Sensory information from viscera, pharynx, larynx, aortic arch, epiglottis, and base of tongue
- (SVA) Taste from epiglottis
- (GVE) Parasympathetics to viscera
- (SVE) Motor to constrictors of pharynx, palatine muscles, and intrinsic muscle of larynx (pharyngeal arch 4 & 6)
Vagus N (CN X) Tract
- Emerges from medulla
- Exits cranium through jugular foramen
How can we test vagus N (CNX)?
Test sensory through:
- Gag reflex by touching posterior pharyngeal wall, edge of soft palate
Test motor through:
- Swallowing reflex
- Look for hoarsness when speaking
- Say “Ahh” and look at uvula: it should elevate at the same height.
Spinal Accessory (CN XI) Function
GSE:
(GSE) Motor to sternocleidomastoid m. and trapezius
Spinal Accessory (CN XI) Tract:
- Emerges from the spinal cord
- Enters the cranium through foramen magnum
- Exits the skull through the jugular foramen
How to test spinal accessory N (CN XI):
Testing is motor only:
- Shrug shoulders against resistance to test trapezius m.
- Turn face to opposite side against resistance to test sternomastoid m.
CN: Jugular foramen
- CN 9, 10, and 11 go through jugular foramen.
- Damage to jugular foramen can lead to sx of 9, 10 and 11.
Hypoglossal (CN XII) Fx
GSE:
(GSE) Motor to intrinsic tongue muscles, and styloglossus, hypoglossus and genioglossus ms.
Hypoglossal (CN XII) Tract
- Emerges from the medulla
- Exits skull via hypoglossal canal
- Travels with the cervical plexus
- Crosses the occipital artery
- Enters the oral cavity
How can we test hypoglossal N?
Motor fx of hypoglossal nerve can only be tested
- Stick out tongue or push tongue into cheek: if lesioned, will deviate to ipsilateral side.
Test CN II:
Test visial acuity
- Light and dark – test after head injury
- Finger counting – test after head injury
-
Snellen’s test types - 20/80 = read at 20 feet what normal vision sees at 80
- Limits = number of cones, sharpness of focus. Astigmatism (corneal irregularities).
- Visual field test – Patient in front of examiner, cover eye, finger count in all 4 quadrants.
- Peripheral vision - Stand close, look straight ahead, and cover opposite eyes. Extend arm and move fingers while gradually moving hand toward midline. Normally subject can see moving fingers.
• Pupillary light reflex - ipsilateral and consensual. Requires full fx of optic (CN2) and oculomotor (CN3) to constrict pupils.
• Blink reflex – blink response requires optic (CN2) and facial nerves (CN7) and occurs when object comes at eye
How do we test : CN III (oculomotor), IV (trochlear), & VI (abducens)?
Testing CN III, IV, & VI are tested together.
- 1. Pupillary light reflex tests the parasympathetic component CN 2?)
- 2. Accomodation has 3 parts: convergence, adjust lens thickness and pupillary constriction (input of optic nerve)
- 3. EMO testing
What. is EMO testing?
Make an H with fingers and then end at. the middle of the nose. Assess oculomotor (CNIII), trochlear (IV) and abducens (VI)
To assess occulootor
- Superior Rectus m. – abduct eye and looks up
- Inferior Rectus m. – abduct eye and look downs
- Inferior Oblique m. – adduct eye and look up
- Medial Rectus m. – adduct eye (reason we can cross eyes)
- Check for ptosis
To assess trochlear
- Superior Oblique m. – adduct eye and looks down.
To assess abducens
- Lateral Rectus m. – abduct eyes
How do we test the Levator Palpebrae Superioris, which is I by the oculomotor N (CN III)?
EMO testing
- Place hand on forehead to fix occipitofrontalis muscle. Examiner holds eye shut while patient tries to open.
Aneurysms of what can compress CN 3 (oculomotor).
1. Posterior communicating A.
2. Posterior cerebral A.
3. Superior cerebellar A.
Aneurysms of what can compress CN 6 (abducens n).
1. Anterior. inferior cerebellar A.
2. Internal Acoustic A (?)
Trigeminal (CN V) Testing
- Testing opthalamic division
- Maxillary division
- Mandibular division
To test ophthalamic division
- Check sensation at the forehead and nose
- Corneal reflex: take cotton and touch sclera -> blink.
- Sensation is supplied by trigmenal N (V1).
- Motor to close the eye is supplied by CN 7.
- Ppl with contacts have supressed this reflex.
To test maxillary division
- Check sensation at the cheek
To test mandibular division
- Check sensation at the chin
- To check motor, check to see person can chew (checks muscles of mastication)
CN V clinical correlations (3)
- Trigeminal neuralgia (tic douloureux)
- Dental trauma
- Cavernous sinus
