evoked potentials

Question 1

what makes an evoked potential unique

Answer 1

uses a machine to produce ES

Question 2

kinds of electrophysiologic eval under evoked potentials

Answer 2

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

Question 3

what is the purpose of electrophysiologic ecam

Answer 3

evaluates integrity of neuromuscular system by detecting nerve potentials

Question 4

what does NCV test

Answer 4

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

Question 5

define orthodromic

Answer 5

sensory - distal to proximal

motor - proximal to distal

Question 6

define antidromic

Answer 6

sensory - proximal to distal

motor - distal to proximal

Question 7

what are the 2 types of NCV tests

Answer 7

SNAP and CMAP

Question 8

exp SNAP

Answer 8

Sensory Nerve Action Potential

tests sensory nerve axons - distal cutaneous receptors to DRG

Question 9

exp CMAP

Answer 9

Compound Muscle Action Potential

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

Question 10

what type of current does NCV use

Answer 10

rectangular monophasic PC

Question 11

explain the electrode placement of NCV

Answer 11

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

Question 12

what is measured in NCV

Answer 12

distance - betw stim and recording electrode; mm

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

d/l = NCV; m/sec

Question 13

relate body temp to NCV

Answer 13

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

Question 14

relate UE/LE to NCV

Answer 14

UE is 7-10 m/s faster than LE

Question 15

relate proximal/distal segments to NCV

Answer 15

more proximal = faster

Question 16

relate age to NCV

Answer 16

<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

Question 17

what conditions reduces NCV

Answer 17

CTS
PNI
demyelinating disorders

Question 18

specifically tests for myasthenia gravis

Answer 18

NMJ transmission

Question 19

exp NMJ transmission

Answer 19

assesses the function of the neuromuscular junction

Question 20

type of test under NMJ transmission

Answer 20

repetitive nerve stimulation test (RNS) or jolly test

Question 21

what is myasthenia gravis

Answer 21

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

Question 22

exp centrally-evoked potentials

Answer 22

cental = CNS

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

Question 23

kinds of test under centrally-evoked potentials

Answer 23

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

Question 24

what does RD test assess

Answer 24

lower motor neuron lesions - peripheral nerve injury only

Question 25

what kind of current does RD test use

Answer 25

faradic muna tas galvanic

Question 26

explain faradic current in RD test

Answer 26

Short pulse duration (<1msec) and >20-50 Hz frequency Monophasic or asymmetrical biphasic PC using cathode as active electrode smooth tetanic or sustained contraction

Question 27

explain galvanic current in RD test

Answer 27

Long pulse duration (100msec) Monophasic or Interrupted DC using cathode as active electrode brisk muscle twitches

Question 28

outcome in faradic and galvanic if normal peripheral nerve

Answer 28

faradic - smooth tetanic or sustained contraction galvanic - brisk muscle twitches

Question 29

outcome in faradic and galvanic if partial RD

Answer 29

faradic - partial or diminished tetanic contraction galvanic - partial or diminished, sluggish twitch

Question 30

outcome in faradic and galvanic if complete RD

Answer 30

faradic - no contraction galvanic - very slow, sluggish twitches

Question 31

outcome in faradic and galvanic if absolute RD

Answer 31

faradic - no contraction galvanic - no contraction

Question 32

exp partial RD

Answer 32

degeneration of part of nerve fibers

Question 33

exp complete RD

Answer 33

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

Question 34

exp absolute RD

Answer 34

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

Question 35

when do we use RD

Answer 35

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

Question 36

what does SD curve and chronaxie test assess

Answer 36

location, severity, and progress of peripheral motor nerve degeneration

Question 37

when do we use SD curve and chronaxie test assess

Answer 37

after 3 wks post-injury para may wallerian na

Question 38

type of current used in SD curve and chronaxie test assess

Answer 38

square monophasic PC or sawtooth/triangular if walang square

Question 39

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

Answer 39

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

Question 40

usual chronaxie of normal nerve

Answer 40

0.05 - 0.5 msec or <1 msec

Question 41

usual chronaxie of fully denervated nerve

Answer 41

30-50 msec

Question 42

usual rheobase for normal nerve

Answer 42

5-35volts / 2-18mA

Question 43

exp the curve from normal to denervated

Answer 43

shifts upward and to the right

Question 44

exp the curve from normal to partially denervated

Answer 44

may kink

Question 45

factors that affect SD curve

Answer 45

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

Question 46

advantages of SD curve test

Answer 46

Quick and easy to perform Requires minimal training More economical (vs other tests)

Question 47

disadvantages of SD curve test

Answer 47

Only provides qualitative data in relation to degree of denervation Cannot locate site of lesion Only few fibers can be assessed in large muscles