Clin Med- Dysfunctional Neuroanatomy 2

kelseyfmeyer's version from 2015-11-30 13:50


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 with parasympathetic/sympathetic control?Anisocoria
you might check Pupillary light reflexes why?problems could be Signs of parasympathetic or sympathetic dysfunction
what is the peripheral pathway for vision? where does it then go in the brain? (not yet central though)retina--> optic nn--> Optic chiasm and tract. Then from there it is the Rostroventral to hypothalamus and 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 on slide 57the left side of the R and L eye both go to the L nerve bundle. The R side of the L and 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 two 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 and descending axons for the cortex travel) which is WHITE MATTER and 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 with other senses, and 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 and run them through it with the lights on and then with low lighting conditions.
what is the dazzle reflex/what does it test?it's a vision test. The dazzle reflex is an involuntary aversion response (blinking, globe retraction, third eyelid protrusion, and/or head movement) to intense illumination of the eye.(This response involves the retina, cranial nerve II, the rostral colliculus, and cranial nerve VII.)
describe the afferent, brain, and efferent pathway of the pupillary light reflexAfferent: CN II (moving along through the retina, optic nerve, optic chiasm, and optic tract) until it reaches the Brain: Pretectal nucleus in the midbrain (the pretectal nuc. axons decussate in caudal comissure, and 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 with the pupillary light reflex? (and which part of the brain)Pretectal nucleus (midbrain) (the axons decussate in the caudal comissure and Terminate at the Parasympathetic Nucleus of III (midbrain) )
what are 5 factors that can influence the pupillary light reflex?(1) Increased sympathetic tone (pupil wouldnt skrink as much) (2) intensity of light source (3) area of retina stimulated (4) ambient light (5) Iris atrophy and other ocular disease
does horner's syndrome have to do with parasympathetic or sympathetic innervation to the eye?sympathetic dysfunction
where can the lesion occur along the visual pathway to cause horners?Lesion can occur anywhere along the pathway! These places include Brain (hypothalamus), cervicothoracic spinal cord, brachial plexus, middle ear, retrobulbar
what are the clinical signs of horner's syndrome?Ptosis, miosis, enophthalmos, and elevated nictitans (might also be peripheral vasodilation= warm, pink skin)
where are the causes (locations) where damage can result in horners? (5, maybe 6)Cervicothoracic spinal cord, Brachial plexus nerve roots/proximal nerves, Neck (cervical sympathetic trunk), Middle ear, Retrobulbar, central(?)
Internal Ophthalmoplegia- what is this? What does the pupil look like during this?This is Paralysis affecting only the ciliary muscle and the iris of the eye.. There will be Mydriasis (dilated pupil)
what are 3 reasons Internal Ophthalmoplegia can develop?(1) Iris sphincter muscle dysfunction/disease (2) Atropine or atropine-like drugs (3) Parasympathetic denervation (CN III or its nucleus)
the motor aspect of CN III (occulomotor) contols which mm? (4)Dorsal, medial, ventral rectus (look dorsal, look medial, look ventral) and ventral oblique (external rotation) (pic on slide 66)
CN IV (trochlear) controls which mm?dorsal oblique (internally rotates) (**contralateral)
CN VI (abduscens) controls which mm? (2)lateral rectus (look laterally), retractor bulbi (pull eyeball inward)
what is Strabismus?Abnormal Eye Position
oculomotor n. dysfunction leads to what kinda strabismus?ventrolateral strabismus (CN III controls Dorsal, medial, ventral rectus and ventral oblique, so if that doesnt work the dysfunction of these results in looking down and to the side)
trochlear n dysfunction causes what kinda strabismus?the eyes will be externally rotated
abducens n dysfunction causes what kinda strabismus?medial strabismus
which CN closes the eye, and which opens it?VII closes it (the number 7 looks like it has a hook on top to push it closed) and III opens it (III looks like pillars keeping it open)
when is it total opthalmoplegia?when there is internal opthalmoplegia and external opthalmoplegia
what is external Ophthalmoplegia?Paralysis affecting one or more of the extrinsic eye muscles.
which type of Ophthalmoplegia is more common with central lesions?external- esp more common to be a central lesion if there is total opthalmoplegia (internal+external= total)
external opthalmoplegia happens when there is damage to which nerve? what are the clinical signs you see?Cranial nerve III (MOTOR-- internal opthalmoplegia is when then parasympathetic innervation of CN III is affected), and you will see a small palpebral fissue (Theyre squinty), there is Ventrolateral strabismus (looking down and to the side), and there is Abnormal vestibular-ocular reflexes
in blindness caused by damage to the Retina or prechiasmal optic nerve, what clinical signs will you see on neurological examination?Ipsilateral mydriasis, blindness (no shit), and Negative PLRs (direct and indirect)
look at slide 71 for a good chart of eye nerve reflex crapwee
what will the neurologic exam look like in a casue where there is blindness due to damage in the Thalamus, optic radiation, and/or visual cortex (forebrain)?Pupils symmetric and responsive, contralateral blindness (bc this is past where it crossed over)
If the animal is blind and 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 and 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 and 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 parasymapthetic partion of CN III or just eye dz (so before the chiasm)

Cerebellum and Vestibular system

Question Answer
what are the three main functions 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 and rEGULATES rate, range, and force of movement (not the primary initiator of movement, though)
why does the cerebellum regulate body tone, both in motion AND at rest? is it done thought 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 and eye movements), intention tremors, Decerebellate rigidity (extension of the thoracic limbs and flexion of the pelvic limbs), Increased muscle tone, Abnormal postural reactions
what are the two kinds of vestibular syndrome?regular or paradoxical
what is Dysmetria?inability to regulate the rate, range, and force of movement
what are 4 problems/symptoms which characterize cerebellar ataxia (part of cerebellar syndrome)?Dysmetria(hypermetria), spasticity, truncal sway, falling
what are Intention Tremors?A form of dysmetria involving the head and 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 and spasticity) where there is Extended thoracic limbs and 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 (because UMNs are being activated)
what will postural reactions be like in cerebellar syndrome?they will be Delayed and followed by an exaggerated response
what is "head rebound phemonemon" and wen do you see it?if you lift their head up so their nose is pointing up, and 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 cerebeallar syndrome
what optic-related tests might be abnormal in a cerebellar syndrome?there MIGHT be an absent menace response, and there might be anisocoria
is there weakness in cerebellary ataxia?NO
is the animal able to initiate movement with 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 with the cerebellum change mentation?no
explain the PERIPHERAL vestibular anatomy/path starting from most peripheralstarts with the receptor, which is the vestibular organ. This is a membranous labyrinth of the inner ear with ducts oriented in each plane. The vestibular nerve comes from the receptors, and then joins with the chochlear nerve. This becomes the vestibulo-cochlear nerve which is CN VIII. CN VIII courses through the internal acoustic meatus along with 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), and then travels to the brainstem (to the motor nuclei of CNs III, IV, and VI, also the reticular formation leading to the vomiting center, and 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 functions of the vestibular system?(1) special proprioception (2) maintain balance (3) Maintains the position of the eyes, neck, and limbs relative to the head (vestibulo-ocular reflexes) (4) Maintains orientation relative to gravity
with vestibular stuff, if you tilt your head to the right, which way do the eyes flick?to the right
what are three major signs of peripheral vestibular ataxia?(1) Listing, leaning to one side ("drunken sailor") (2) rolling (3) tight circling
which reactions WONT you see on a neuro exam for Peripheral Vestibular Syndrome?NO POSTURAL REACTION DEFICITS
what kinda postural reaction things will you see with 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 (head toward someone but quickly look away if you're spotted)
in peripheral vestibular syndrome, what kinda strabismus do you see?ventral strabismus (looking down) (down down dizzy dizz down down dizzy dizzy)