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Emma H&N > Peripheral Neuropathies > Flashcards

Peripheral Neuropathies Flashcards

1
Q

what % of peripheral neuropathies are idiopathic?

A

10-30% are idiopathic

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2
Q

subtypes of neuropathy

A

1) axonal
2) demyelinating
3) wallerian degeneration

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3
Q

perineurium

A

surrounds each nerve fascicle

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4
Q

epineurium

A

binds all the fascicles in a nerve

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5
Q

blood supply of peripheral nerves

A

longitundinal, highly anastamosing vascular supply of arterial branches

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6
Q

size and myelination of touch, pressure, spindle afferents

A

Large, heavily myelinated

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7
Q

size and myelination of sharp pain, temperature

A

smaller, thinly myelinated

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8
Q

size and myelination of dull/burning/poorly localized pain

A

small, unmyelinated

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9
Q

type I PNS sensory fibers

A

myelinated
80-120 m/sec (fastest)

touch, pressure, spindle afferents

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10
Q

type II PNS sensory fibers

A

thinly myelinated
30-75 m/sec (medium speed)

sharp pain, temperature

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11
Q

type III PNS sensory fibers

A

unmyelinated
0.5-30 m/sec (slowest)

burning, dull, diffuse pain

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12
Q

PNS Motor: large myelinated fibers terminate on _____

A

PNS Motor: large myelinated fibers terminate on MUSCLE

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13
Q

PNS Motor: small unmyelinated fibers terminate on _____

A

PNS Motor: small unmyelinated fibers terminate on parasympathetic/sympathetic ganglia

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14
Q

alpha motor unit

A

80-120 m/sec (fast)
large, myelinated

main movers of skeletal muscle

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15
Q

gamma motor unit

A

4-25 m/sec (kinda slow)
large, myelinated

terminate on muscle spindles, maintain tension

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16
Q

preganglionic autonomic

A

3-15 m/sec (slow)

small, unmyelinated

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17
Q

postganglionic autonomic

A

.5-2 m/sec (super slow)

small, unmyelinated

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18
Q

axonal transport runs along __________

A

axonal transport runs along MICROTUBULES

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19
Q

anterograde transportation

A

away from cell body

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20
Q

retrograde transportation

A

towards cell body

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21
Q

T or F: axonal transport does not require energy

A

F.

Axonal transport requires energy – ox phos in mitochondria

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22
Q

effects of vincristin/vinblastine (chemotherapeutic drugs) on axons

A

Disrupt neurotubule organiation.

Results in neuropathy.

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23
Q

________ transport is necessary to maintain the axon itself

A

ANTEROGRADE transport is necessary to maintain the axon itself (and thus the muscle too since denervated muscles atrophy)

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24
Q

what happens to denervated muscle?

A

atrophy

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25
what is transported with rapid axonal transport?
synaptic vesicles, | membrane bound proteins
26
what is required to link proteins to microtubules in anterograde axonal transport?
kinesin
27
what is transported with slow axonal transport?
soluble enzymes, tubulin (used in making microtubules) 100x slower
28
what determines the rate of recovery from nerve injury?
slow axonal transport | -bc it is needed to transport the structural components
29
what is transported with retrograde transport?
Signal of nerve injury | -induces chromatolysis
30
neurotropic viruses and axonal transport
Neurotropic viruses: polio, herpes, rabies. - enter peripheral nerve endings - use retrograde transport to ascend to nerve body
31
what protein is required with retrograde axonal transport?
dynein (instead of kinesin)
32
Wallerian degeneration
"dying forward" - axonal injury occurs - axon dies from site of injury to the end of the axon (peripherally) - chromatolysis - muscle atrophy
33
axonal degeneration
"dying back" - metabolic derangement - distal part dies first (due to lack of nutrients etc) - proximal direction - chromatolysis - muscle atrophy
34
segmental demyelination
- myelin is stripped off in some places - AP dies out - axon is still intact, just missing myelin - NO chromatolysis - NO muscle atrophy
35
nerve conduction studies
- used to diagnose peripheral neuropathies - measure nerve function - measure evoked action potentials (either motor or sensory) does NOT look at overall nerve function -just between cell body and end organ -helps distinguish between types of lesions
36
Peripheral nerve injury: appearance on nerve conduction studies
Motor: abnormal Sensory: abnormal - lesion distal to dorsal root ganglion - both axons are cut between cell body and muscle - neither trigger an AP
37
nerve root injury: appearance on nerve conduction studies
Motor: abnormal Sensory: normal - axon bringing sensory info to cell body is still intact; still transmits AP - motor axon is cut between anterior horn cells and muscle; degenerates; no AP
38
patterns involved in diagnosis of peripheral neuropathies
- Focal v. Systemic - Motor v. Sensory v. Autonomic v. Mixed - Chronic v. Acute - Axonal v. Demyelinating - weakness: myotomal or peripheral nerve pattern - atrophy? - distal weakness (axonal) or proximal weakness (demyelinating)?
39
patellar reflex tests
L4
40
achilles reflex tests
S1
41
how to measure conduction velocity
Stimulate nerve at two spots Subtract the time between the two slower in demyelinated nerve
42
pattern of root damage v. peripheral n damage
ROOT - dermatomes overlap - difficult to pinpoint PERIPHERAL N - do not overlap - easier to pin point
43
muscles atrophy suggests
axonal damage
44
no atrophy suggests
demyelinating damage
45
distal weakness suggests
axonal damage
46
proximal weakness suggests
demyelinating damage | OR myopathy
47
symptoms of axonal neuropathy
- slow, chronic - stocking glove distribution - loss of reflexes distally - muscle wasting distally - low amplitude CMAPs (muscle AP) - absent SNAPs (sensory AP)
48
causes of axonal neuropathy
- metabolic: diabetes, uremia, endocrine, porphyria - toxic: environmental or pharmalogical agents - deficiency: thiamine, pyridoxine, vit E - genetic: HSMN II - paraneoplastic: tumors make antibodies that injure nerves
49
Guillian-Barre Syndrome
- acute demyelinating polyneuropathy - segmental demyelination - primarily motor (some sensory) - rapidly progressive - no reflexes (afferent pathology) - ataxia (afferent pathology) - conduction block - treatment: immune modulating therapy (IVIg)
50
if reflexes are lost, it is most likely due to a ______ injury
sensory/afferent
51
what part of the nerve is most susceptible to injury?
myelin - may degenerate as part of primary disease process - or as secondary effect of axonal disruption
52
causes of demylinating polyneuropathy
- autoimmune: Guillain-Barre, CIDP (chronic inflammatory demyelinating neuropathy), certain antibodies - genetic: Charcot-Marie-Tooth I, metachromatic leukodystrophy
53
causes of chronic demyelinating neuropathy
- hereditary: Charcot-Marie-Tooth I | - chronic inflammatory demyelinating neuropathy (CIDP)
54
histological sign of chronic demyelinating neuropathy
onion bulb sign | -myelin grows, dies, grows, dies...
55
ischemic mononeuritis multiplex
- commonly seen in polyarteritis nodosa (vasculitis) - fascicular injury --> individual fascicles are injured by interruption of microcirculation of nerve - confluent mononeuritis makes it look like generalized neuropathy - biopsy: arteritis, fascicular injury -tx: steroids (vasculitis), cyclophosphamide (immune modulating drug)
56
fascicular injury
- Individual fascicles are injured, not the whole nerve. | - Due to interruption of the microcirculation of the nerve.
57
types of focal neuropathies
- Compressive/traumatic - Ischemic: diabetic or vasculitic -- fascicular injury - autoimmune; brachial plexopathy -Injury: wallerian degeneration
58
injury associated with focal neuropathies
wallerian degeneration - disruption of anterograde transport so axon dies backward - retrograde transport starts chromatolysis, increases metabolic activity for axonal regeneration - axonal sprouting occurs - regeneration depends on if schwann cell sheaths are disrupted or not
59
traumatic nerve injury classification
CLASS 1: Neurapraxia - compression with focal demyelination - no denervation (no atrophy) - quick recovery CLASS 2: Axonotmesis - axonal damage - intact nerve sheath for sprouting to occur through - slower recovery (sometimes incomplete) CLASS 3: Neurotmesis - scarred/disrupted nerve sheath - no recovery
60
neurotmesis
- scarred/disrupted nerve sheath | - no recovery
61
Axonotmesis
- axonal damage - intact nerve sheath for sprouting to occur through - slower recovery (sometimes incomplete)
62
Neurapraxia
- compression with focal demyelination - no denervation (no atrophy) - quick recovery
63
involvement of feet before hands is seen in ______ neuropathy
involvement of feet before hands is seen in AXONAL neuropathy
64
slowed conduction characterizes a ________ neuropathy
slowed conduction characterizes a DEMYELINATING neuropathy
65
nerve disease in general (w/ exception of ____________) usually leads to atrophy
nerve disease in general (w/ exception of SEGMENTAL DEMYELINATION) usually leads to atrophy

Emma H&N (49 decks)

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