Clin Med - Neuro 2

drraythe's version from 2017-09-30 21:00


Question Answer
4 ways you can assess vision on a neuro exam?Menace response
Visual placing
Cotton ball tracking
Obstacle course
What is the word for uneven pupils, which might indicate a problem w/ parasympathetic/sympathetic control?Anisocoria
(Thank you David Bowie)
You might check Pupillary Light Reflexes why?Problems could be Signs of parasympathetic or sympathetic dysfxn
What is the peripheral pathway for vision? where does it then go in the brain? (not yet central tho)Retina → Optic nn → Optic chiasm & tract. Then from there it is the Rostroventral to hypothalamus & pituitary gland
Where do most axons decussate (cross over) in the visual pathway?Optic chiasm/tract (Degree depends on the species)
Why is decussating useful?It allows Binocular field of vision, frontal positioning of eyes, conjugate eyeball movement
The axons of the optic nerve which decussate at the optic chiasm come from which aspect of the retina? (medial or temporal(lateral)?)MEDIAL
Which axons in coming from the retina/optic nerve stay ipsilateral?The ones on the temporal side
Be able to draw out the basic chart of vision pathologiesThe left side of the R & L eye both go to the L nerve bundle. The R side of the L & R eye go to the right nerve bundle
How much do primate optic nerves decussate?50%
How much do cat (dog?) optic nerves decussate?Cat = 65%
Dog = 75%
How much do hose/ruminant optic nerves decussate?80-90%
How much do birds/fish optic nerves decussate?100%
What are the 2 places (in order) of the CENTRAL PATHWAY for vision?The Lateral geniculate nucleus (LGN, in the thalamus) → Occipital lobe (visual cortex is there)
Lateral geniculate nucleus (LGN) is where/part of what? Is it part of the white or grey matter? where does it travel to get to the last part of the central path for vision?The LGN is part of the thalamus. It is part of the internal capsule (where ascending & descending axons for the cortex travel) which is WHITE MATTER & follows along the optic radiation path to the visual cortex in the occipital lobe
The occipital lobe houses the visual cortex, where the signal traveling from the optic nerve reaches it's final destination in the brain. what happens in the visual cortex?Visual information is received, decoded, integrated w/ other senses & then decisions about it can occur
What is photopic vision? What is scotopic vision? Which evaluation of vision can be used to test both of these?Photopic = Vision of eye in well lit conditions
Scotopic vision = Vision of eye in poorly lit conditions
You can make an OBSTACLE COURSE & run them through it w/ the lights on & then w/↓lighting conditions.
What is the Dazzle Reflex & what does it test?It's a vision test. The Dazzle Reflex is an involuntary aversion response (dramatic or prolonged blinking, globe retraction, 3rd eyelid protrusion, &/or head movement) to intense illumination of the eye. (This response involves the retina, cranial nerve II, the rostral colliculus & cranial nerve VII.)
Describe the afferent, brain & efferent pathway of the Pupillary Light ReflexAfferent: CN II (moving along through the retina, optic nerve, optic chiasm & optic tract) until it reaches the Brain: Pretectal nucleus in the midbrain (the pretectal nuc. axons decussate in caudal commissure & then Terminate at the Parasympathetic Nucleus of III (midbrain) )
Efferent: CN III-parasympathetic fibers, to the ciliary ganglion → short ciliary nerves, to control the iris sphincter mm
Which part of inside the brain deals w/ the Pupillary Light Reflex? (Which part of the brain)Pretectal nucleus (midbrain) (the axons decussate in the caudal commissure & Terminate at the Parasympathetic Nucleus of III (midbrain) )
What are 5 factors that can influence the Pupillary Light Reflex?(1) ↑ sympathetic tone (pupil wouldnt shrink as much)
(2) Intensity of light source
(3) Area of retina stimulated
(4) Ambient light
(5) Iris atrophy & other ocular dz
Does Horner’s Syndrome have to do w/ parasympathetic or sympathetic innervation to the eye?Sympathetic dysfxn
Where can the lesion occur along the visual pathway to cz Horner’s?Lesion can occur anywhere along the pathway!
These places incld:
Brain (hypothalamus)
Cervicothoracic spinal cord
Brachial plexus, middle ear
What are the CS of Horner’s Syndrome?Ptosis
Enophthalmos & elevated nictitans
(might also be peripheral vasodilation = warm, pink skin)
Where are the czs (locations) where dmg can result in Horner’s? (5, maybe 6)Cervicothoracic spinal cord
Brachial plexus nerve roots/proximal nerves
Neck (cervical sympathetic trunk
Middle ear
Internal Ophthalmoplegia - what is this? What does the pupil look like during this?This is paralysis affecting only the ciliary muscle & the iris of the eye. There will be Mydriasis (dilated pupil)
What are 3 reasons Internal Ophthalmoplegia can develop?(1) Iris sphincter muscle dysfxn/dz
(2) Atropine or atropine-like drugs
(3) Parasympathetic denervation (CN III or its nucleus)
The motor aspect of CN III (Occulomotor) controls which mm? (4)Dorsal rectus
Medial rectus
Ventral rectus (look dorsal, look medial, look ventral)
Ventral oblique (external Rotation)
CN IV (trochlear) controls which mm?Dorsal oblique (internally Rotates) (**Contralateral)
CN VI (abducens) controls which mm? (2)Lateral rectus (look laterally)
Retractor bulbi (pull eyeball inward)
What is Strabismus?Abnormal eye position
Oculomotor n. dysfxn leads to what kinda strabismus?Ventrolateral strabismus (CN III controls Dorsal, medial, ventral rectus & ventral oblique, so if those dont work the dysfxn of these results in looking down & to the side bc the only muscles still working are the lateral rectus (CN6) & the dorsal oblique (CN4) )
Trochlear n dysfxn czs what kinda strabismus?The eyes will be externally Rotated
Abducens n dysfxn czs what kinda strabismus?Medial strabismus
Which CN closes the eye & which opens it?CNVII closes it (the number 7 looks like it has a hook on top to push it closed)
CNIII opens it (III looks like pillars keeping it open)
When is it total Ophthalmoplegia?When there is Internal Ophthalmoplegia & External Ophthalmoplegia
What is external Ophthalmoplegia?Paralysis affecting 1 or more of the extrinsic eye muscles
Which type of Ophthalmoplegia is more common w/ central lesions?External - esp more common to be a central lesion if there is total Ophthalmoplegia (internal+external = total)
External opthalmoplegia happens when there is damage to which nerve? what are the CS you see?Cranial nerve III (MOTOR - Internal Ophthalmoplegia is when then parasympathetic innervation of CN III is affected) & you will see a small palpebral fissure (Theyre squinty), there is Ventrolateral strabismus (looking down & to the side) & there is Abnormal vestibular-ocular reflexes
In blindness czd by damage to the Retina or prechiasmal optic nerve, what CS will you see on neurological examination?Ipsilateral mydriasis
Blindness (no shit)
Negative PLRs (direct & indirect)
What will the neurologic exam look like in a cz where there is blindness due to damage in the Thalamus, optic radiation, and/or visual cortex (forebrain)?Pupils symmetric & responsive
Contralateral blindness (bc this is past where it crossed over)
If the animal is blind & the PLRs are abnormal, where is the damage?Rostral (before) the the LGN (part of the thalamus) (SEE PIC ON slide 74-the axons bodies after the chiasm but before the brain)
If the animal is blind & the PLRs are normal, where is the damage?It is caudal (after) the LGN (part of the thalamus) (SEE PIC ON slide 74-the axons bodies after the chiasm but before the brain), up & into the cortex → CORTAL blindness (amaurosis)
What is Amaurosis?Cortical blindness
If the animal is NOT blind, but there is an abnormal PLR, where is the damage?It is in the Efferent arm of reflex → that is to say it is the parasympathetic portion of CN III or just eye dz (so before the chiasm)

Cerebellum & Vestibular System

Question Answer
What are the 3 main fxns of the cerebellum?Coordination of movement & posture
Regulation of body tone
Maintenance of equilibrium
How does the cerebellum go about accomplishing Coordination of movement & posture?It smooths muscle movements & REGULATES rate
Range & force of movement (not the 1° initiator of movement, tho)
Why does the cerebellum regulate body tone, both in motion & at rest? Is it done thot UMN or LMN?Tone control via UMN (think about how UMN has signs of going up) for antigravity support of body
What are 5 symptoms of cerebellar syndrome?Cerebellar ataxia (inability to coordinate balance, gait, extremity & eye movements)
Intention tremors
Decerebellate rigidity (extension of the thoracic limbs & flexion of the pelvic limbs)
↑ muscle tone
Abnormal postural rxns
What are the 2 kinds of vestibular syndrome?Regular or Paradoxical
What is Dysmetria?Inability to regulate the rate, range & force of movement
What are 4 problems/symptoms which characterize cerebellar ataxia (part of cerebellar syndrome)?Dysmetria (hypermetria)
Truncal swaying
What are Intention Tremors?A form of dysmetria involving the head & neck...there is a fine tremor when an animal initiates voluntary movement (such as reaching for food or a toy)
What does Decerebellate Rigidity look like?It is a kind of Opisthotonus (state of severe hyperextension & spasticity) where there is Extended thoracic limbs & flexed pelvic limbs. The mentation is unaffected.
Will the muscle tone be LMN or UMN in cerebellar syndrome?UMN
What will reflexes be like in cerebellar syndrome?Normal to hyperactive (bc UMNs are being activated)
What will postural rxns be like in cerebellar syndrome?They will be delayed & followed by an exaggerated response
What is "Head Rebound Phenomenon" & when do you see it?If you lift their head up so their nose is pointing up & then let go, their head will fall to the table in an exaggerated manner instead of them just returning to normal head position. This is a sign you can see in cerebellar syndrome
What optic-related tests might be abnormal in a cerebellar syndrome?There MIGHT be an absent menace response & there might be anisocoria
Is there weakness in cerebellary ataxia?NO
Is the animal able to initiate movement w/ cerebellar syndrome?YES, but there might be a fine tremor when they do it (intention tremor)
What is a simple way to say how the cerebellum works?It smooths out the motor movements
Will a problem w/ the cerebellum change mentation?No
Explain the PERIPHERAL vestibular anatomy/path starting from most peripheralStarts w/ the receptor, which is the vestibular organ. This is a membranous labyrinth of the inner ear w/ ducts oriented in each plane. The vestibular nerve comes from the receptors & then joins w/ the chochlear nerve. This becomes the vestibulo-cochlear nerve which is CN VIII. CN VIII courses through the internal acoustic meatus along w/ the facial nerve near it (*CN VIII does not actually wend (go in a specified direction) through the middle ear, but dz of the tympanic cavity can result in vestibular syndrome)
Explain the CENTRAL vestibular anatomy/path starting from where CN VIII left offCN VIII goes to the vestibular nuclei (which is adj. to the 4th ventricle in the MEDULLA) & then travels to the brainstem (to the motor nuclei of CNs III, IV & VI, also the reticular formation leading to the vomiting center & then relay through the thalamus for conscious perception of balance). Lastly, the signal can go to the spinal cord for ipsilateral extensor muscle facilitation
How does the cerebellum relate to the vestibular system?Fibers from the vestibular receptors go to the flocculonodular lobe ( a lobe in the cerebellum). In the F. lobe there are Purkinje cells which are inhibitory to the vestibular nuclei (the part in the medulla that CN VIII goes to). Also, fibers in the cerebellum reach the vestibular nuclei via the caudal cerebellar peduncles
Vestibular proprioception/ataxia can be aka?Special proprioception/ataxia
What are the 4 fxns of the vestibular system?(1) Special proprioception
(2) Maintain balance
(3) Maintains the position of the eyes, neck & limbs relative to the head (vestibulo-ocular reflexes)
(4) Maintains orientation relative to gravity
W/ vestibular stuff, if you tilt your head to the right, which way do the eyes flick?To the right
What are 3 major signs of peripheral vestibular ataxia?(1) Listing, leaning to 1 side ("drunken sailor")
(2) Rolling
(3) Tight circling
Which rxns WONT you see on a neuro exam for Peripheral Vestibular Syndrome?NO POSTURAL RXN DEFICITS
What kinda postural rxn things will you see w/ peripheral vestibular syndrome?NONE
In peripheral vestibular syndrome which direction will the head tilt in? (Toward or away from lesion?)Toward the lesion
In which direction does the FAST phase of the pathological nystagmus go in vestibular syndrome?Fast phase AWAY from lesion (slow phase towards lesion it is corrective, it is the slow phase that is pathologic)
In peripheral vestibular syndrome, what kinda strabismus do you see?Ventral strabismus

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