Neuro Part 2 Video 2

What is Internuclear Ophthalmoplegia (MLF syndrome)?

*Connection between the two nuclei is messed up Damage: BILATERAL to the MLF (Medial Longitudinal Fasciculus) Symptoms: Inability to ADDUCT eyes during LATERAL GAZE TO EITHER SIDE, NYSTAGMUS- rapid movement of eyeball *Only during lateral gaze you lose function of medial rectus Note: Convergence. (Focus on near object) remains NORMAL

TQ) Damage to CN 4 can lead to what disorder?

Fourth Nerve Palsy -CONGENITAL is the most common (kids) In adult can get from ischemia to CN 4

Pupillary Responses and Eye movements: Centers for eye movements- Vestibular (subcortical): coordination of eye movements are associated with the _____ ____.

Inner ear

The oculomotor nucleus is located where?

Location: at the level of the superior colliculus in the Midbrain

Pinealoma would cause damage to the posterior commissure and we would be loosing pupillary light reflex for the eye on the ______ side.

Opposite

What are some requirements for being able to clearly visualize near objects?

A) Convergence- turning inward of eyes (medial rectus muscles, LMN) B) Accommodation- -requires thickening of the lens (ciliary body muscles, parasympth) -pupillary constriction (sphincter pupillae muscles, parasympth)

TQ) The interpeduncular fossa is located between the _____ peduncles.

Cerebral

TQ) What is alternating Oculomotor hemiplegia ("Weber's Syndrome"):

Damage to the: 1) Oculomotor nerve fibers- results in IPSILATERAL 3rd nerve palsy 2) Pyramidal Tract- descending motor pathway in the crus cerebri of the MIDBRAIN Results in CONTRALATERAL findings: - UMN paralysis - SPASTIC HEMIPLEGIA - MAY INCLUDE PARALYSIS OF LOWER FACE (corticobulbar fibers) TQ) Cause: aneurysm to the POSTERIOR CEREBRAL ARTERY (pressing on CN 3 as it goes through the brainstem *UMN are traveling through the crusi cerebri at the level of the midbrain

What is Parinaud's syndrome?

Damage: Compression of DORSAL midbrain near the VERTICAL GAZE CENTER Cause: Pinealoma (tumor) Sxs: inability to raise eyes above the horizontal plane (upward portion only) Note: UPWARD GAZE is more susceptible to dysfunction

What is the Argyll Robertson pupil?

-PUPILS DO NOT CONSTRICT WITH LIGHT STIMULATION (BOTH DIRECT AND INDIRECT) -due to BILATERAL damage to the Pretectal area (syphilis) - STD -pupils CAN constrict during ACCOMMODATION for near vision (different pathway)

What is the pupillary light reflex?

The pupillary light reflex is how both pupils constrict when exposed to light. When one is stimulated with light ("unilateral light stimulation") BOTH pupils constrict. Bilateral response: 1) Direct response- response of light stimulated eye 2) Consensual response (indirect response)- response of the unstimulated eye

What is the pathway for the accommodation reflex?

*Pathway requires a neural circuit to the cerebral cortex (occipital lobe and back) 1) NEAR OBJECT 2) Retina 3) Optic nerve 4) Optic chiasm 5) Optic tract 6) LGN of the thalamus 7) Occipital lobe 8) Superior colliculi 9) Oculomotor nuclear complexes which include: 1. Edinger Westphal nuclei: -PREganglionic parasympathetic nerve fibers to ciliary ganglion -Postganglionic parasympathetic nerve fibers to CILIARY BODY muscles for rounding of lens and sphincter pupillae muscles for constriction 2. Oculomotor LMN to medial rectus muscles for turning inward of eyes

TQ) Which of the following portions of the ventricular system is associated with the midbrain?

-cerebral aqueduct

TQ) Which of the following are required for near vision?

-convergence -thickening of the lens -pupillary constriction

In the pathway of pupillary light reflex, the afferent limb is by CN _____. Than interneurons in the _____ nuclei. Then the efferent limb is by CN _____.

1) 2 (Optic N.) 2) Pretectal (tectum = roof in brainstem) 3) 3 (Oculomotor N.-parasympathic portion

Damage to the LMN portion of CN 3 results in: paralysis of four ________ muscles. Loss of all eye movements, except _______. ______ during upward gaze and downward gaze. Diplopia during lateral gaze to the _____ side of the lesion. Lateral ______. Can not ______ eyes for near vision. Paralysis of the skeletal muscle portion of LPS muscle causing severe _____ of the _____ eyelid.

1) Extraocular (SR, IR, MR, IO) 2) Abduction 3. Diplopia (double vision) 4. opposite (but NOT during lateral gaze to the side of the lesion) 5. Strabismus (eye turned outward) 6. converge (turn eyes inward) 7. Ptosis 8. Upper

TQ) The red nucleus us located at which of the following levels?

1) In the midbrain at the level of the SUPERIOR colliculus *Red nucleus is the team player the cerebellum uses to talk to the brainstem at the level of the midbrain

What is the order of the pupillary light reflex pathway?

1) Light exposure in ONE eye 2) Retina 3) Optic Nerve 4) Optic chiasm 5) Optic Tract 6) PRETECTAL NUCLEI 7) BOTH Edinger-Westphal nuclei 8) PREganglionic Parasympathic nerve fibers in Oculomotor nerves 9) Ciliary ganglia 10) Postganglionic parasympathic nerve fibers 11) Sphincter pupillae muscles CONSTRICTION OF BOTH PUPILS

What can damage to the parasympathetic portion of CN 3 cause?

1) Loss of Function of the CILIARY MUSCLES - disruption of near vision - inability to ACCOMMODATE lens for NEAR VISION 2) Loss of function of the SPHINCTER PUPILLAE MUSCLES - MYDRIASIS: pupil fixed and dilated - loss of pupillary light reflexes

The vertical gaze center is located near the ______ nuclear complex in the midbrain. It's function is upward or downward gaze.

1) Oculomotor

The Pretectal area is a part of the midbrain located immediately rostral to the ______ colliculus and contains the posterior commissure with the adjacent Pretectal nuclei. The Pretectal nuclei project both uncrossed and crossed fibers (some via the posterior commissure) to _____ Edinger-Westphal nuclei of CN 3, resulting in constriction of BOTH pupils.

1) Superior 2) BOTH

CN3 innervates structures on the _______ side. Therefore damage to the right Oculomotor nerve would result in signs and symptoms on the ____ side.

1) ipsilateral (same) 2) right

In left internuclear ophthalmopegia, the sxs include paresis of _____ ocular adduction, and nystagmus of _____ eye.

1) left 2) Right (lead dog lateral rectus)

In unaccommodated lens, the ciliary muscles are _____. In accommodated lens, the ciliary muscles are ______.

1) relaxed 2) contracted

The oculomotor nucleus: contains cell bodies of LMNs and gives rise to motor fibers that innervate the _______ muscles and the skeletal muscle portion of the _______ muscles. The oculomotor nerve exits from the ____ surface of midbrain from the ____ _____

1. Extraocular muscles (SR, IR, MR, IO) 2. LPS 3. Ventral 4. Interpeduncular fossa Function: elevates upper eyelid and involved in ALL eye movement (except abduction b/c CN 6 does that)

Pupillary Responses and Eye movements: Centers for eye movements- Cortical Centers: 1) Voluntary eye movements are associated with the ____ ____. 2) Automatic scanning or following movements are associated with the _____ _____. 3) Accommodation and convergence of eyes for near vision are associated with the _____ _____.

1. Frontal lobe 2. Occipital lobe 3. Occipital lobe

CN 3 Oculomotor Nerve- Has two components which arise from two different nuclei. The LOWER MOTOR NEURON portion of CN 3 arises from the ______ nucleus. The PARASYMPATHETIC portion of CN 3 arises from the _____ _____ nucleus.

1. Oculomotor 2. Edinger-Westphal

The Edinger-Westphal Nucleus: contains pre-ganglionic ______ neurons. Pre-ganglionic parasympathetic fibers exit with LMNs and synapse in the ____ ____. Post-ganglionic parasympathetic fibers innervate two intraocular muscles. Function: ______ muscles- thicken the lens during accommodation to visualize near objects. _____ _____ muscles - constrict the pupils

1. Parasympathetic 2. Ciliary ganglion 3. Ciliary 4. Sphincter pupillae Reminder: The dilator pupillae muscles, also intraocular muscles, are innervated by sympathetic nerve fibers from the superior cervical ganglion.

Pupillary Responses and Eye movements: Centers for eye movements- Gaze centers in the brainstem: 1) Lateral gaze center: located in the Abducens nucleus in the _____. A) LMN portion of Abducens nucleus innervates ______ LR muscle. B) Interneurons portion via axons traveling in medial longitudinal fasciculus (MLF), MLF activates the _____ OCULOMOTOR NUELUS for innervation of the MR muscle.

1. Pons 2. Ipsilateral (same side) 3) CONTRALATERAL

In a NORMAL individual, when the head is tilted, the eyes rotate due to the normal function of both the right and left superior oblique muscles. However a person with left superior oblique paralysis displays: head tilt to the ______ side, _____ eye intorts, extorted ____ eye, causing double vision.

1. Unaffected 2. Right 3. Left *Dysfunction common sxs is DOUBLE VISION

What are the sxs of Third Nerve Palsy?

Diplopia + lateral strabismus + NO Convergence + Ptosis ——> DOWN & OUT PANS: NO accommodation/near vision + Mydriasis + NO pupillary light reflex

Where does the trochlear nerve originate? What is the location? Course? Function?

Origin: cell bodies of LMNs in the Trochlear Nucleus Location: The trochlear nucleus is at the level of the INFERIOR COLLICULUS in the midbrain Course: Fibers emerge from the nucleus and cross (decussate) fibers from the other side. The trochlear nerve is the only CN to emerge dorsally from the brainstem. The nerve exits the midbrain below the inferior colliculus and turns ventral toward the orbit to innervate the superior oblique muscle. Function: depresses and abducts the eye. Pure motor.

What are some results of damage to the Trochlear Nerve?

Results in difficulty depressing the eyeball when turned inward, difficulty walking downstairs when eyes need to be turned down and in unilateral involvement leads to a compensatory head tilt to the contralateral side. Superior oblique paralysis: CAN'T DEPRESS EYEBALL —-> Difficulty walking downstairs = CONTRA HEAD TILT