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pmod 2nd shift > evoked potentials > Flashcards

evoked potentials Flashcards

1
Q

what makes an evoked potential unique

A

uses a machine to produce ES

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2
Q

kinds of electrophysiologic eval under evoked potentials

A

NCV
NMJ transmission
centrally evoked potentials
reaction of degeneration test
SD curve

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3
Q

what is the purpose of electrophysiologic ecam

A

evaluates integrity of neuromuscular system by detecting nerve potentials

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4
Q

what does NCV test

A

tests peripheral motor & sensory neurons on both orthodromic & antidromic responses

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5
Q

define orthodromic

A

sensory - distal to proximal

motor - proximal to distal

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6
Q

define antidromic

A

sensory - proximal to distal

motor - distal to proximal

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7
Q

what are the 2 types of NCV tests

A

SNAP and CMAP

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8
Q

exp SNAP

A

Sensory Nerve Action Potential

tests sensory nerve axons - distal cutaneous receptors to DRG

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9
Q

exp CMAP

A

Compound Muscle Action Potential

tests motor nerve fibers - anterior horn cells to NMJ of the innervated muscle

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10
Q

what type of current does NCV use

A

rectangular monophasic PC

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11
Q

explain the electrode placement of NCV

A

apply active electrode to nerve - cathode is distal part and closest to recording electrode

recording electrode - over muscle or nerve

ground - usually on bony prominence

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12
Q

what is measured in NCV

A

distance - betw stim and recording electrode; mm

latency - time bet stim and muscle contraction or nerve acitvation; msec

d/l = NCV; m/sec

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13
Q

relate body temp to NCV

A

inc body temp = inc NCV and dec latency; hence uses gel for accurate results

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14
Q

relate UE/LE to NCV

A

UE is 7-10 m/s faster than LE

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15
Q

relate proximal/distal segments to NCV

A

more proximal = faster

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16
Q

relate age to NCV

A

<3-5 y/o = lower by 50% vs normal adults

> 40 = gradual slowing vs middle-aged

6th & 7th decade = 10 m/sec less than
middle-aged

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17
Q

what conditions reduces NCV

A

CTS
PNI
demyelinating disorders

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18
Q

specifically tests for myasthenia gravis

A

NMJ transmission

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19
Q

exp NMJ transmission

A

assesses the function of the neuromuscular junction

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20
Q

type of test under NMJ transmission

A

repetitive nerve stimulation test (RNS) or jolly test

21
Q

what is myasthenia gravis

A

chronic autoimmune neuromuscular disease - nag wweaken skeletal muscles and affects breathing if diaphragm

22
Q

exp centrally-evoked potentials

A

cental = CNS

machine induces stim tas computer measures if brain receives the stim from the receptor tested

23
Q

kinds of test under centrally-evoked potentials

A

somatosensory evoked potentions (SSEP)
visual evoked potential (VEP)
brainstem auditory evoked potential (BAEP)

24
Q

what does RD test assess

A

lower motor neuron lesions - peripheral nerve injury only

25
Q

what kind of current does RD test use

A

faradic muna tas galvanic

26
Q

explain faradic current in RD test

A

Short pulse duration (<1msec) and >20-50 Hz frequency

Monophasic or asymmetrical biphasic PC using cathode as active electrode

smooth tetanic or sustained contraction

27
Q

explain galvanic current in RD test

A

Long pulse duration (100msec)

Monophasic or Interrupted DC using cathode as active electrode

brisk muscle twitches

28
Q

outcome in faradic and galvanic if normal peripheral nerve

A

faradic - smooth tetanic or sustained contraction

galvanic - brisk muscle twitches

29
Q

outcome in faradic and galvanic if partial RD

A

faradic - partial or diminished tetanic contraction

galvanic - partial or diminished, sluggish twitch

30
Q

outcome in faradic and galvanic if complete RD

A

faradic - no contraction

galvanic - very slow, sluggish twitches

31
Q

outcome in faradic and galvanic if absolute RD

A

faradic - no contraction

galvanic - no contraction

32
Q

exp partial RD

A

degeneration of part of nerve fibers

33
Q

exp complete RD

A

degeneration of all nerve fibers; muscle tissue retains contractile elements; so wala pa atrophy, fibrotic changes

34
Q

exp absolute RD

A

degeneration of all nerve fibers; muscle tissue severely atrophic, fibrotic or non-contractile

35
Q

when do we use RD

A

if we want to know if may PNI or if unexplained paralysis

should be done > 10 days post injury; kc need mag wallerian muna or mag manifest yung injury

36
Q

what does SD curve and chronaxie test assess

A

location, severity, and progress of peripheral motor nerve degeneration

37
Q

when do we use SD curve and chronaxie test assess

A

after 3 wks post-injury para may wallerian na

38
Q

type of current used in SD curve and chronaxie test assess

A

square monophasic PC or sawtooth/triangular if walang square

39
Q

what are the pulse durations usually used in SD curve and chronaxie test

A

100, 30, 10, 3, 1, 0.3, 0.1, 0.03, 0.01 msec - start from 100 msec then pababa

40
Q

usual chronaxie of normal nerve

A

0.05 - 0.5 msec or <1 msec

41
Q

usual chronaxie of fully denervated nerve

A

30-50 msec

42
Q

usual rheobase for normal nerve

A

5-35volts / 2-18mA

43
Q

exp the curve from normal to denervated

A

shifts upward and to the right

44
Q

exp the curve from normal to partially denervated

A

may kink

45
Q

factors that affect SD curve

A

Skin resistance
Subcutaneous tissues (eg fats)
Skin temperature
Electrode size
Electrode placement
Age
Fatigue

46
Q

advantages of SD curve test

A

Quick and easy to perform

Requires minimal training

More economical (vs
other tests)

47
Q

disadvantages of SD curve test

A

Only provides qualitative data in relation to degree of denervation

Cannot locate site of lesion

Only few fibers can be assessed in large muscles

48
Q
A

pmod 2nd shift (12 decks)

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