Wvsom Neuro 3 05 - Cranial Nerve Nuclei Iii, Iv, Vi

Front 1

CN 3 innervates what?

Back 1

Medial, Superior, Inferior Rectus

Inferior Oblique

Levator Palpebrae superioris

Pupillary Constrictors

Lens Ciliary Muscles

Front 2

Where is the oculomotor nucleus is located?

Back 2

Rostral Midbrain, midline anterior to PAG

on level with the Superior colliculus & Red nucleus

Front 3

Detail the three Ipsilateral parts of the Oculomotor subnucleus & what they innervate

Back 3

Dorsal - Inferior Rectus

Intermediate - Inferior Oblique

Ventral - Medial rectus

Front 4

Detail the two bilateral parts of the Oculomotor subnucleus & what they innervate

Back 4

Edinger-Westphal - Pupillary constrictors & Lens ciliary muscles

Central Caudal - Levator Palpebrae superior

Front 5

Detail the contralateral part of the Oculomotor subnucleus & what they innervate

Back 5

Medial - Superior Rectus

Front 6

Draw the Oculomotor Subnuclei

Back 6

Doodle time

Front 7

Lesions of the oculomotor nucleus affect the:

Back 7

Contralateral superior rectus m.

Front 8

CN 4 innervates

Back 8

contralateral superior oblique m.

Front 9

Describe the pathway of CN 4

Back 9

1. Exits the midbrain dorsally, above the level of the midbrain-pons

2. Wraps around to the ventral side of the midbrain & passes between the superior cerebellar a. & posterior cerebral a.

3. Enters the orbital cavity through the superior orbital fissure

4. synapses on the contralateral superior oblique muscle

Front 10

Describe the pathway of CN 3

Back 10

1. Exits the anteroventral midbrain

2. passes between the superior cerebellar a. & the posterior cerebral a.

3. enters the orbital cavity through the superior orbital fissure

4. Either

- synapses on the ciliary ganglion & later to the ciliary muscles like pupillae constrictor muscles

- directly innervates the muscles controlling eye movement [minus lateral rectus & superior oblique]

Front 11

Location of the CN 4 nucleus

Back 11

Caudal Midbrain at the level of the inferior colliculus & decussation of the superior cerebellar peduncle

At midline, On the edge of the PAG

Front 12

CN 6 Innervates what?

Back 12

Ipsilateral Lateral Rectus

Front 13

Describe the pathway of CN 6

Back 13

1. Abducens nucleus in the caudal pons

2. Exits the brainstem at the ventral pons

3. Wraps around the lateral side of the internal carotid artery

4. Enters the orbital cavity through the superior orbital fissure

5. Synapses on the lateral rectus muscle

Front 14

Location of the CN 6 nucleus

Back 14

Caudal Pons

- slightly lateral to midline

- close to 4V

- look for facial nerve arcing around it

Front 15

Define Diplopia

Back 15

Double vision

Front 16

Causes of Diplopia

Back 16

1. Mechanical problems - orbital fracture with muscle entrapment

2. Disorders of the extraocular muscles (thyroid disease, orbital myositis, orbital pseudotumor)

3. Disorders of the Neuromuscular junction (myasthenia gravis)

4. Disorders of CN 3, 4, 6

Front 17

What can and cannot cause Monocular Diplopia

Back 17

Never caused by eye movement disorders

more related to disorders in control (supranuclear)

Front 18

Causes of CN 3 Palsy

Back 18

- Diabetic neuropathy

- Head Trauma

- abnormalities in the subarachnoid space, cavernous sinus or orbit from tumor, infection or venous thrombosis

- herniation of the medial temporal lobe

- lacunar infarcts or other infarcts involving the oculomotor nucleus or exiting nerve fascicles

- Neuromuscular junction [myasthenia gravis] or muscle disorders

- compression by intracranial aneurysm

Front 19

Most common location for intracranial aneurysms

Back 19

Junction of the Posterior communicating artery & the internal carotid

Front 20

Less common location for intracranial aneurysm

Back 20

- junction of the posterior communicating artery with the posterior cerebral artery

- junction of the basilar artery + PCA junction

- junction of the basilar artery + superior cerebellar artery

Front 21

Symptoms of a CN 3 Nerve palsy

Back 21

Ipsilateral side of lesion

- Ptosis

- weakness of upward gaze

- weakness of downward gaze

- weakness of adduction

- dilated, unresponsive pupil

Front 22

Symptoms of a CN 3 nucleus palsy

Back 22

Ipsilateral side of lesion

- weakness of downward gaze

- weakness of adduction

Contralateral side of lesion

- weakness in upward gaze

Front 23

Define hypertropia

Back 23

misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye

Front 24

Define Extorsion

Back 24

The outward divergent rotation of the upper poles of the vertical meridian of the cornea of each eye.

Front 25

s/sx of CN 4 Palsy

Back 25

Vertical diplopia

Hypertropia + Extorsion

Front 26

Causes of CN 4 Palsy

Back 26

- trochlear nerve is the most commonly injured cranial nerve due to its long course & thin caliber = sheer injury

- pathology of the subarachnoid space, cavernous sinus, or orbit due to tumor, infection, & aneurysm

- vascular disorders or tumors in the midbrain or tectum [pineal gland or anterior cerebellum]

Front 27

s/sx of CN 6 palsy

Back 27

Horizontal diplopia

- better with near-vision due to convergence which is dependent upon medial rectus

- worse with far-sight due to divergence which is dependent upon lateral rectus

Front 28

Causes of CN 6 Palsy

Back 28

- Abducens nerve is susceptible to injury from downward traction caused by elevated intracranial pressure

- Pathology of the subarachnoid space, cavernous sinus, or orbit due to tumor, infection, & aneurysms.

- pontine infarct or other disorders affects exiting VI nerve fascicles - these also produce horizontal gaze palsy in the direction of the legion due to supranuclear controls

- lesion of CN VI nucleus often affect CN VII resulting in an ipsilateral facial weakness

Front 29

What muscles generate Horizontal eye movements & what innervates them

Back 29

Oculomotor - Medial rectus m.

Abducens motor nucleus - lateral rectus m.

Front 30

What is the horizontal gaze center & what is its function?

Back 30

Abducens nucleus

controls the horizontal movement of both eyes in the direction ipsilateral to the side of the nucleus

Front 31

Describe the function of the PPRF

Back 31

Paramedian pontine reticular formation

- provides input from the cerebral cortex & other pathways to the Abducens nucleus

Front 32

Describe the nerve pathways as they extend from the Abducens nucleus with regards to Horizontal gaze control.

Back 32

some nerves project from the Abducens nucleus to the ipsilateral Lateral Rectus muscles.

some nerves project to the contralateral oculomotor nucleus to activate the contralateral medial rectus muscle.

Front 33

What is the MLF & what happens when it is lesioned?

Back 33

- connection between the Abducens nucleus and the contralateral oculomotor nucleus

lesion = eye ipsilateral to the lesion does not adduct on attempted horizontal gaze

Front 34

With a lesion of the MLF, why is adduction by the affected eye spared during convergence

Back 34

fibers for adduction come from the pretectal area & do not travel in the MLF

Front 35

Common causes of Lesions of the MLF

Back 35

Multiple Sclerosis

Pontine Infarcts

Tumors involving the MLF

Front 36

Where is the vertical gaze control center?

Back 36

Rostral Interstitial Nucleus of the MLF [inMLF]

~interstitial nuclei of Cajal [INC]

Project dorsally through the posterior commissure to innervate mainly CN 3

[inferior oblique & superior rectus]

Front 37

Describe the various lesions in the vertical eye movement centers.

Back 37

Dorsal inMLF = impaired upgaze

Ventral inMLF = impaired downgaze

Front 38

Describe Parinaud's Syndrome

Back 38

Lesion of the Dorsal Midbrain & pretectal area

- impairment of vertical gaze [esp. upgaze]

- large irregular pupils that do not react to light but may react to near-far accommodation

- eyelid abnormalities

- impaired convergence = convergence-retraction nystagmus

Cause: pineal tumors & hydrocephalus that compress the dorsal midbrain

Front 39

Describe the Vergence control centers

Back 39

Vergence movements are under the control of descending inputs from the visual pathways in the occipital & parietal cortex & constitute part of the accommodation reflex

- brainstem centers for vergence are in the midbrain reticular formation

Front 40

Describe Convergence

Back 40

- visual signals relayed to the visual cortex & then to the pretectal nuclei

- Descending inputs from the visual pathways in the occipital & parietal cortex

- occurs when a visual object moves from far to near

Front 41

What are the components of Convergence?

[3 things]

Back 41

1. Pupillary constriction

2. Accommodation of the Lens ciliary muscle

3. Convergence of the eyes

Front 42

What is the Lesion: Impaired OD rightward gaze

Back 42

Right Abducens nerve - CN VI palsy

Front 43

What is the Lesion: impaired OU rightward gaze

Back 43

right lateral gaze palsy

- Right Abducens nucleus

- Right PPRF

Front 44

What is the lesion: impaired OS rightward gaze + OD horizontal nystagmus

Back 44

Left MLF [left INO] - nystagmus is a result of reflex

or

Left MLF + Left abducens nucleus

Front 45

Describe the 1 1/2 syndrome

Back 45

Left MLF + Left Abducens nucleus

Front 46

What are the three supranuclear systems of control?

Back 46

Vestibular apparatus & nuclei

Reticular formation - PPRF

Tectum (superior colliculus) & pretectal areas

Front 47

What gaze center is in the pons?

Back 47

Pontine horizontal gaze center

Front 48

What vision control centers are in the cerebrum

Back 48

Frontal Eye fields

Parieto-occipito-temporal cortex

Visual Cortex

Front 49

What gaze centers are in the midbrain

Back 49

Vertical gaze center of the midbrain

Front 50

Define Saccades

Back 50

point the fovea toward the object of interest

Front 51

Define Smooth pursuit

Back 51

voluntary reflex & operates in tracking a moving object to keep the object on the fovea of the retina

Front 52

Define Convergence & Divergence

Back 52

move the eyes in opposite directions so the image is positioned on both fovea

Front 53

Define Vestibulu-ocular Reflex [VOR]

Back 53

hold images still on the retina during brief head movements

Front 54

Define Optokinetic movements

Back 54

hold images stationary during sustained head rotations or translation

Front 55

Describe horizontal saccade control

Back 55

Frontal eye fields generate saccades in the contralateral direction through connections to the contralateral PPRF.

Front 56

Describe control of the smooth pursuit movements

Back 56

Parieto-temporal cortex is responsible for smooth pursuit movements in the ipsilateral direction via connections with the vestibular nuclei, cerebellum, PPRF

- right pursuit is driven by the right parietal lobe

- left pursuit is driven by the left parietal lobe

- may have a contribution to voluntary horizontal saccades

Front 57

__________ constitutes a head orienting response to a compelling stimulus

Back 57

Reflexive saccades

Front 58

Describe smooth pursuit circuitry

Back 58

- Trigger - movement of a visual target across the retina way from the fovea [retinal slip]

- Parietotemporal junction conputes speed & direction of moving visual stimul. Project to the frontal eye fields & brainstem.

- Pathway descends to the ipsilateral pons then to the PPRF, the flocculonodular lobe of the cerebellum, vestibular nuclei, ultimately the horizontal or vertical gaze center.

Front 59

Describe the VOR

Back 59

Vestibulo-ocular reflex - stabilizes the eyes on the visual image during head & body movements

Front 60

Describe the OKN

Back 60

Optokinetic Reflex - allows the eye to follow objects in motion when the head remains stationary