Neuroscience Lec 9 - Peripheral Neuropathies

Front 1

what are the 3 types of peripheral neuropathies?

Back 1

- axonal

- demyelinating

- wallerian degeneration

Front 2

what is the difference between the epi & perineurium?

Back 2

- perineurium surrounds each fasicle (whole nerve)

- epineurium binds all the fascicles in the nerve

Front 3

which axonal transport is towards & away from cell body? does it require energy?

Back 3

- anterograde: towards synapse

- retrograde: towards cell body

- energy dependent

Front 4

what happens in muscle if you effect anterograde transport?

Back 4

- muscle can atrophy because it is involved in maintaining muscle

Front 5

what do vincristine & vinblastine do?

Back 5

- arrest mitosis in rapidly developing cells to disrupt cancer cells

- because it binds to tubulin it damages nerves as well & can cause denervated muscle atrophy

Front 6

which protein is involved in rapid axonal transport? what does it carry?

Back 6

- kinesin (ATP dependent)

- carries synaptic vesicles & membrane bound proteins like plasma membrane proteins

Front 7

what does slow axonal transport carry?

Back 7

- soluble enzymes and tubulin used in making microtubules

- determines rate of recovery from nerve injury as it is needed to transport structural components

Front 8

which type of axonal transport determines rate of recovery from nerve injury?

Back 8

- slow axonal transport

Front 9

what is chromatolysis? who incudces this?

Back 9

- nerve body swells, nissl substance dissolves (seen in beginning of regeneration & apoptosis)

- carried by retrograde transport

Front 10

which motor protein is important for retrograde transport?

Back 10

- dynein

Front 11

what is wallerian degeneration?

Back 11

- dying forward

- degneration from point of axonal injury peripherally

- Nerve dies forward, get muscle atrophy, chromatolysis

Front 12

what does the degeneration pattern look like in axonal degeneration?

Back 12

- metabolic derangement, from most distal part --> proximal part of axon

- Nerve dies forward, get muscle atrophy, chromatolysis

Front 13

what happens in segmental demyelination?

Back 13

- axon is in tact, no chromatolysis, myelin is damaged & don't get conduction through this section

- muscle does not atrophy, cell body is ok

Front 14

if injury is distal to DRG what types of neurons are injured?

Back 14

- sensory & motor

Front 15

what if injury is proximal to DRG?

Back 15

- sensory axon will be normal

Front 16

what does proximal vs distal weakness indicate?

Back 16

- distal indicates axonal

- proximal indicates demyelinating or myopathic pattern

Front 17

what is the timeline for axonal neuropathy? distribution? reflexes? muscle tone?

Back 17

- slow & chronic

- stocking-glove distribution

- loss of reflexes distally

- muscle wasting distally

- decreased CMAPS (motor), absent SNAP

Front 18

what happens to CMAP in axonal neuropathy?

Back 18

- lower amplitude CMAP telling you muscle is atrophied

- with proximal stimulation velocity is about same & amplitude about same (because there are some axons still & some not functioning)

Front 19

what is Guillian - Barre syndrome?

Back 19

- primarily motor, can be sensory, myelin disruption

- rapidly progessive (peaks in 2 weeks)

- areflexia & ataxia because demyelination of the sensory component too

Front 20

do muscles waste in guillian-barre syndrome?

Back 20

- no because axonal transport & axon is ok, but myelin is not functioning so nerve is not functioning

Front 21

what happens to CMAP in segmental demyelination?

Back 21

- loss of CMAP beyond the myelin

Front 22

what kinds of demyelinating polyneuropathies are there?

Back 22

- autoimmune: guillian-barre, CIDP, antibodies

- genetic: charcot-marie tooth type I, metachromatic leukodystrophy

Front 23

what are onion bulbs?

Back 23

- when you have chronic demyelinating disease where you get demyelination and remyelination looks like onion bulb

Front 24

what happens in ischemic mononeuritis multiplex?

Back 24

- can be seen in polyarteritis nodosa

- nerve infarcts b/c blood flow to nerve is compromised in vasculitis

Front 25

what kinds of different focal neuropathies are possible?

Back 25

- compressive

- ischemic: diabetic or vasculitic. Fascicular injury

- infiltrative: neoplastic or granulomatous

- autoimmune: brachial plexopathy

Front 26

what happens in wallerian degneration?

Back 26

- distruption of anterograde transport means organelles cannot be transmitted to distal axons & cannot renew membrane

- retrograde transport tells cell to increase metabolic acitvity & produce GFs for axonal regeneration

Front 27

what is the difference between axonotmesis vs neurotmesis with wallerian degneration?

Back 27

- if schwann cells are not disrupted will regenerate - axonotmesis

- if schwann cells disrupted reinnervation cannot occur - neurotmesis

Front 28

what are the 3 classes of traumatic nerve injury?

Back 28

Class I neurapraxia: stretch injury or compressive, demyelinating, may recover in weeks to months
Class 2 axonotmesis: axon destroyed but nerve sheath intact, slow process
Class 3 neurotmesis: sheath is transected or destroyed will not regenerate