Cranial Nerves

Eye motions are controlled by

CN III, CN IV, CN VI

medial rectus muscle

adduction, nasal direction, towards middle

lateral rectus muscle

abduction, moves eye laterally

superior rectus muscle

elevates eye

inferior rectus

depressor down

superior oblique

depression and intorsion

intorsion of the eye

upper pole of the eye is rotated towards the nose (superior muscles)

extorsion of the eye

upper pole of the eye is rotated away from the nose (inferior muscles)

CN III eye movements use what muscles

superior rectus

inferior rectus

medial rectus

inferior oblique

CN IV eye movements use what muscles

superior oblique

CN VI eye movements use what muscles

lateral rectus

superior and inferior oblique are most efficient when eye is?

Adducted

Parasympathetic nucleus of cranial nerve III

Edinger-Westphal Nucleus

Three clinical tests of eye movement are commonly used in diagnosis of eye movement disorders. The three most common tests evaluate

• the position of the eyes at rest

• the ability to move the eyes up, down, in and out on command

• the ability to follow an object with the eyes when the object is moved in each of the four directions (tracking).

Three clinical tests of eye movement are commonly used in diagnosis of eye movement disorders. The three most common tests evaluate:

• the position of the eyes at rest

• the ability to move the eyes up, down, in and out on command

• the ability to follow an object with the eyes when the object is moved in each of the four directions (tracking)

Using these three tests, what deficits would result from damage to CN III?

At rest, The eye would be down and out

Difficulties when CN III is damaged

Adduction of the eye (medial)

Elevation of the eye

Depression of the eye

If CN III signs are seen on the right side but not the left, would the lesion more likely involve the nuclei of CN III or the third nerve?

Involve the nerve because the nuclei of the two sides are so close together that they both are likely to be damaged by a CNS lesion

After loss of the parasympathetic functions of CN III, resulting from damage to the Edinger-Westphal nucleus, identify three expected findings (symptoms) that would be observed?

-The pupil would be dilated because of loss of tone in the constrictor muscles

-There would be a loss of the pupillary light reflex because light causes pupillary constriction by parasympathetic activation via CN III

-The lens would remain elliptical and there would be loss of accommodation (ability to focus on near objects).

Ptosis

dropping of eyelid (CN III)

Levator Palpebrae

Muscle that elevates eyelid (VN III)

Accommodation of lens

Describes the changes in shape of the lens to allow for near and far vision

Extorsion

Rotation the eye so the top moves laterally

Ciliary Muscles

Muscles that relax tension on the lens and cause the lens to be more spherical (see closer up)

Strabismus

Deviation of eye from normal position

Diplopia

Double vision (mismatching images from left and right eye)

Mydriasis

Dilated Pupil

CN IV is the only nerve to

exit dorsally and contralaterally from the brainstem and exclusively innervate a contralateral structure (superior oblique)

True or false: The right nucleus of CN IV supplies the left IO.

FALSE (SO)

True or False: The left CN IV supplies the right SO.

FALSE

True or False: The left CN IV supplies the right SO.

TRUE

True or False: The right CN IV supplies the right IO.

FALSE

True or False: Damage to the R. nucleus of IV produces intorsion of the left eye

FALSE, extorsion

True or false: Damage to the L. CN IV produces down and out deviation on the left.

FALSE

True or False: Damage to the L. nucleus of IV produces upward deviation of the R. eye.

TRUE

CN IV damage produces extorsion on the ______ side

same

The left Nucleus of CN IV produces upward deviation of the _____ side

opposite

True or false: Damage to the right CN IX produces extorsion of the right eye

True

Superior Oblique (intorsion vs extorsion)

In group: Intorsion

Inferior Oblique (intorsion vs extorsion)

Out group: Extorsion

A patient presents with symptoms that you immediately recognize as indicative of left CN IV damage. You are cued by the way the patient carries her head. In order to get rid of diplopia resulting from the left SO paralysis, the head is tilted to align the two eyes. This is a difficult question, but see if you can figure it out. The diagram above (Figure 15) holds a few clues.

The head is titled to the ____ because ____

The head is tilted the side opposite of the affected eye because the normal head compensates for the head tilt

Function of CN VI (abducens)

Movement of the eye laterally by contraction of the ipsilateral LR muscles

What are the three nuclei of CN VII

Motor Nucleus

Salivatory Nucleus

Nucleus Solitarius

Innervation pattern of eye muscles mnemonic

LR6-SO4-ALO3

Lateral rectus CN 6, Superior Oblique CN 4, All others CN 3

Saccades

abruptly changing fixation point of eye

Volitional Saccades

Under conscious control from the frontal lobe

Reflexive Saccades

Unconscious superior colliculi

Smooth Pursuit

slow tracking allowing an object to be in central vision

paramedian pontine reticular formation

CN VI sends axons to the same side then crosses in the contralateral medial longitudinal fasciculus to synapse on cells of CN III to move the contralateral eye

Both eyes will rotate right

Internuclear opthalmoplegia

damage to the MLF, cannot tract inward however because cranial nerve 6 remains in tact they can move the eye nasally to focus on a near object

multiple sclerosis

Deviation of the eye at rest: down and out

CN III (means that the eyes cannot go in and up if this is injured)

Deviation of the eye at rest: up

CN IV

Deviation of the eye at rest: in

CN VI

Inability to move the eyes: Down when adducted

CN IV

Inability to move the eyes: Up or In

CN III

Inability to move the eyes: out

CN VI

Identify the eye muscle that produces movement in each of the following directions: Down when adducted

SO

Identify the eye muscle that produces movement in each of the following directions: up when abducted

SR

Identify the eye muscle that produces movement in each of the following directions: in

MR

Identify the eye muscle that produces movement in each of the following directions: up when adducted

IO

Identify the eye muscle that produces movement in each of the following directions: down when abducted

IR

Identify the eye muscle that produces movement in each of the following directions: out

LR

Two patients have paralysis of the right LR muscle. In patient A the right CN VI has been severed; the damage to patient B is at the nucleus of CN VI, including the paramedian pontine reticular formation. How would you tell the difference between these two patients with a simple clinical test?

a. Both patients will show deviation of the right eye nasally at rest (strabismus). And, when asked to converge the eyes to focus on a point near the nose, the left eye of both patients will look in towards the nose.

b. If patient A is asked to look to the right, the left eye will move nasally, but the right eye will not move temporally.

c. If patient B is asked to look to the right, neither eye will move. This is because the involvement of the PPRF nucleus interrupts the circuit for conjugate lateral deviation

d. If the lesion has spared the nuclei of CN VI but involved the MLFs between CNs III and VI, neither eye would deviate at rest, but neither eye would move nasally when the patient is asked to make conjugate lateral eye movements to the right and left side. However, the eyes would move nasally to focus on an object near the nose (like when reading). This is called internuclear ophthalmoplegia (INO). Remember that eye movement problems will often be bilateral because of the close proximity to the midline of the nuclei of CNs III, IV and VI, and the MLF. If all the eye muscles are involved, the lesion is probably peripheral, where CNs III, IV and VI run together (e.g., the cavernous sinus or superior orbital fissure).

The pretectal area of the midbrain receives visual afferents that originate

in the retina and pass through the optic nerve

sphincter muscle controls

pupil size

ciliary muscle

allows the lens to round and focus the eye for near vision

the LGN (is / isn't) a necessary relay for the retinotectal system

ISN'T

Parasympathetic pupil constriction

AFFERENT (Towards to brain from the eye)

signal comes down optic nerve, through optic chiasma, along optic tract, and to the pretectal nucleus

then sent to edinger-westphal nucleus

Parasympathetic pupil constriction EFFERENT (from the brain to the eye)

Signal from EWN travels along oculomotor nerve, through ciliary ganglion, to the iris sphincter and ciliary muscle causing the pupil to constrict

Which of the following characterize input to the pretectal nuclei?

a. involves both eyes

b. both direct from retinae and relayed from contralateral pretectal nucleus c. travels in part through posterior commissure

d. travels in part through anterior commissure

e. relays through lateral geniculate body

f. directly synapses onto CN III neurons

involves both eyes

both direct from retinae and relayed from contralateral pretectal nucleus

travels in part through posterior commissure

Which of the following characterize output to the pretectal nuclei?

a. involves both eyes

b. both direct from retinae and relayed from contralateral pretectal nucleus c. travels in part through posterior commissure

d. travels in part through anterior commissure

e. relays through lateral geniculate body

f. directly synapses onto CN III neurons

involves both eyes

travels in part through posterior commissure

directly synapses onto CN III Neurons

Direct light reflex

effects on eye illuminated

Consensual Light Reflex

Affects other eye

Describe the near Triad ( what must happen for you to accomplish near vision)

convergence of the eyes

contraction of ciliary muscle produces tension on lens allowing focusing on closer objects ( makes lens rounder) - accommodation

constriction of pupil bilaterally

Argyll Robertson Pupil

Small bilateral pupils, constrict very poorly to light

will not react but will accommodate to near stimuli

Associated with CNS syphilis

damage to pretectal nuclei will impair

the consensual light reflex induced to either eye

Horner's Syndrome

Mitosis (pupil constriction)

Ptosis (eye drop)

Anihidrosis (loss of sweating on that side)

Stimulating the edge of the cornea with saline/cotton will produce

ipsi and contralateral corneal reflex in intact trigerminal sensation

Upper motor lesion CN VII (facial) causes what

Spare the eyebrow but cause contralateral smile droop (impacts lower part of face on opposite side)

Lower motor lesion CN VII (facial) causes what

weakness of eyebrow and smile on the same side

If a patient who has left facial weakness had a cortical stroke which vessel is likely the cause?

right middle cerebral artery

If a patient has left facial weakness what cranial nerve and location is it at?

Left pons

what side does the uvula go for glossopharyngeal (CN IX)

goes to the side that still has an intact lower motor pathway, goes to unaffected side of lower motor lesion

nucleus solitarius

pain temperature and touch from pharynx and posterior tongue

back 1/3 of tongue

Blood pressure

9th cranial nerve

CNXII Lower motor lesion

lick the lower lesion, goes to weak side

CN XII Upper lesion

Will go to the opposite side of the lesion (will not lick the lower)

What side will the tongue go for CN XII upper lesion?

Opposite side as upper lesion

What side will the tongue go for CN XII lower lesion?

To the side of the lesion ("licks lower lesion")

The patient with a lesion distal to the lateral pons will most likely exhibit?

Ipsilateral smile droop and ipsilateral upper facial weakness

(eyebrow is supplied by both right and left so that is why cortex supplies both left and right

What do they usually test in neuro for different functions?

pupillary light, corneal, cough, and gag

afferent and efferent for midbrain pons and medulla

Upper motor lesion for CN VII (PONS, facial nerve)

opposite side smile droop

Lower motor lesion CN VII (PONS, facial nerve)

Ipsilateral smile AND facial weakness IMPACTS THE EYEBROW

remember: cortex

contralateral

your patient has difficulty maintaining a patent airway and is unable to lift their head off the bead; which is the most likely cause

Medullary infarct involving CN X and XI causing bulbar weakness

Which of the following structures participate in both the direct and consensual light reflex

Optic Nerve

Optic Chiasm

Optic Tract

Pretectal Area

Edinger-Westphal nucleus

CN III

Pupillary Sphincter

What nerves monitors the consensual reflex to the eye?

CN V (Trigeminal) sensing touch on the cornea

CN VII (Facial) motor response inducing the eyelid to close

What are the symptoms for a CN VII (facial) lower motor lesion?

eye and mouth are dropping

What are the symptoms for a CN VII (facial) uppermotor lesion?

only the mouth is dropping, since it is from the top the eyebrows are controlled

ipsilateral means

same side

contralateral

opposite side

Name the nucleus of CN VII: Submandibular Gland

Salivatory Nucleus