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Peripheral vestibular disorders
- benign paroxysmal positional vertigo
- vestibular neuritis
- endolymphatic hydrops/Meniere's disease
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BPPV
- >50YO, head trauma, prior inner ear injury prolonged recumbency, migraine w/aura
- diagnose w/Dix-Hallpike Maneuver (lay down)
- Nyatagmus: delayed onset, <1min, fatigue
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Vestibular neuritis
- inflammation secondary to viral reactivation
- isolated vertigo, nausea, no hearing loss, gradual improvement over weeks
- good recovery
- positive head impulse test: delayed correction of eye movement for head movement (VOR) (if cerebellar infarct, negative test)
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Endolymphatic hydrops
- abnormal fluid balance in inner ear, dilation
- end-stage response to vascular, autoimmune, metabolic insults
- >2 vertigo episodes >20min
- hearing loss
- tinnitus or fullness
- treatment: diuretics, salt restriction, stress reduction, shunt
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peripheral v central nystagmus
- peripheral: unidirectional, vertical or horizontal comp, inhibit w/ smooth pursuit, normal neuro exam and ocular control
- central: direction changing, not related to inner ear structure, no inhibition w/ fixation, no compensation, other ocular probs, abnormal neuro exam
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Pathway of motor learning in cerebellum
- climbing fibers trigger complex spike in Purkinje cells
- recently active parallel fiber inputs from granule cells are "punished"
- protein kinase C is a coincidence detector necessary for LTD, reduced # of AMPA receptors
- inhibitory interneuron/parallel fiber connections are strengthened
- LTP of mossy fibers to deep nucleus neurons
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What are the different inputs to the cerebellum and where do they come from?
- pons: mossy fibers travel thru middle cerebellar peduncle
- spinal cord: mossy fibers travel thru inferior cerebellar peduncle
- vestibular nuclei: mossy fibers travel thru inferior cerebellar peduncle
- inferior olive: climbing fibers thru inferior cerebellar peduncle (1:1 fiber:PK cell)
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What are the outputs of the cerebellum?
- carried by Purkinje cell axons
- vestibular nuclei
- deep nuclei: dentate nucleus, interposed nucleus, fastigial nucleus
- deep nuclei then project to: thalamus/cortex, red nucleus/spinal cord, inferior olive (influence climbing fiber input), vestibular nuclei and reticular formation (influence posture/balance)
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Cells that use GABA as a neurotransmitter
Purkinje, Golgi neuron, basket cell
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dentate nucleus
- with the lateral parts of the cerebellar hemispheres and serves as the major output nucleus of the cerebrocerebellum
- damage of the dentate nucleus = cerebellar signs that you would find with damage of the lateral cerebellar hemispheres, i.e. limb ataxia and action (intention) tremor
- leave the cerebellum through the superior cerebellar peduncle and project to motor nuclei of the thalamus, on their way to the cerebral cortex
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Medial longitundinal fasciculus
- carries information from the abducens nucleus to the oculomotor nucleus
- from the medial vestibular nucleus to the medial vestibulospinal tract to regulate head position
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lateral vestibulospinal tract
- mediates balance and posture
- is not fed by the MLF
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vestibular semicircular canals
- kinocilia are on the utricle side of the hair cells in the horizontal canal, but on the opposite side in the other 2 canals
- hair cells depolarize when the cupula is pushed in the direction of the kinocilia
- planes of the 3 semicircular canals are all orthogonal to one another
- right vestibular nerve is excited during a horizontal rightward turn
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areas that get direct input from the vestibular nuclei
- cerebellum
- eye movement nuclei (including the abducens)
- reticular formation
- lateral & medial vestibulospinal tracts
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Nystagmus to the right can be caused by:
- Damage to the left vestibular end organ
- Spinning around to the right
- Damage to the left Scarpa’s ganglion
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what prevents regeneration in the CNS?
- Oligodendrocytes express several inhibitory proteins (Nogo, MAG, OMgp)
- bind to Nogo Receptors on the neuronal surface and actively inhibit regrowth.
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Unlike long-term depression (LTD) at parallel fiber synapses onto cerebellar Purkinje cells, NMDA receptor-dependent LTD at excitatory synapses in the CA1 region of the hippocampus requires:
Activation of protein phosphatases by increases in intracellular calcium levels.
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auditory path, caudal to rostral
- superior olivary nucleus
- lateral lemniscus
- inferior colliculus
- medial geniculate nucleus
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