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1

What is electrophysiology exam

Evaluate integrity of neuromuscular system
Measures electrical activity

2

Biofeedback

Monitoring and transforming physiologic data into understandable feedback
Enables individual to gain voluntary control over muscular or autonomic nervous system functions
Visual or auditory stimuli
Adjunct tool and not a treatment itself

3

Evoked potentials

Applies electricity to evoke an action potential

4

NCV

Peripheral, motor, and sensory neurons

Orthodromic and antidromic responses

5

Orthodromic

normal

6

Antidromic

reverse

7

SNAP

Provides info on sensory nerve axon
Cutaneous receptors to DRG

8

CMAP

Motor nerve fibers from origin in anterior horn cells to neuromuscular junction of muscle it innervates

9

NCV Answers the questions:

Is there involvement of peripheral nerves?
Sensory? Motor? both?
Where?
How many?
Magnitude?
increasing/decreasing impairment?
localized/systemic disorder?

10

NCV motor components

Stimulating electrode coming from machine
2 small electrodes applied on nerve
2 cm apart
Handheld electrodes
Cathode distal to anode
active/recording electrode: on muscle or nerve
Reference: distally placed
Ground: over bony areas for elimination of noise

11

motor vs. sensory ncv

Stimulate sensory nerves distally instead of proximally

12

what info do we get from ncv test

distance = Distance from stimulating to recording electrode (mm)

Latency
Conduction time between stimulus and start of muscle contraction or activation of nerve
(Msec)

13

Latency

Conduction time between stimulus and start of muscle contraction or activation of nerve (msec)

14

ncv =

distance/latency

15

factors affecting ncv

Body temp
UE is 7-10 m/s faster
Proximal segments are faster
Age
Less than 3-5 yr old is slower than normal adults
>40 - gradual slowing
60-70- 10 m/sec less than middle aged

16

in compression lesions, ncv is

reduced

17

NMJ transmission

Also known as jolly test
Test for myasthenia gravis
Weakness of skeletal muscles
Affects diaphragm
Function of neuromuscular junction

18

centrally evoked potentials

Generated by nervous system in response to sensory stimuli
SSEP: what we feel, light touch, pressure
VEP
BAEP
Induce a stimuli and computer reflects if stimuli was received by brain

19

REACTION OF DEGENERATION

Faradic and galvanic test
Assessment of lower motor neuron lesions
A motorpoint is stimulated
Screening test for differentiating with normal peripheral innervation vs muscle with peripheral denervation
Not specific location
Not a standalone test
Not done at least 10 days after onset of problem
May be indicated in conditions of unexplained paralysis

20

faradic current

short pulse duration less than 1 msec

monophasic or asymmetrical PC

cathode is active

smooth tetanic

21

galvanic current

long pulse duration >100 msec

monophasic or interrupted dc

cathode is active

brisk muscle twitch

22

partial RD faradic vs galvanic

F; partial or diminished tetanic

G: partial or diminished sluggish twitches

23

partial RD

degeneration of part of nerve fibers

24

complete RD

degeneration of all nerve fibers

muscle tissue remains

25

absolute RD

degeneration of all nerve fibers; muscle is non-contractile

26

complete rd f vs. g

f: no contraction

g: very slow, sluggish twitches

27

STRENGTH-DURATION CURVE AND CHRONAXIE TEST

After 3 weeks of nerve injury
Used to check for improvements
Square monophasic PC / sawtooth/ triangular
Cathode is stimulating
8-10 pulse durations

28

usual pulse durations in SD curve

100, 30, 10, 3, 1, 0.3, 0.1, 0.03, 0.01

must be strong enough to depolarize threshold

29

rheobase

least intensity needed to elicit contraction

normal: 3-35 v/2-18 ma

30

chronaxie

Minimum time needed to produce a muscle contraction with intensity set at twice the rheobase
Normal: 0.05-0.5 msec or <1 msec

31

compute for chronaxie

2 x rheobase

32

Factors affecting sd curve

Skin resistance
Subcutaneous tissue
Skin temperature
Electrode size
Electrode placement
Age
Fatigue

33

Advantages of sd curve

Quick and easy
Minimal training
Economical

34

Disadvantages of sd curve

Provides qualitative data in relation to degree of denervation
Cannot locate site of lesion
Few fibers can be assessed

35

emg biofeedback

We are getting the muscle activity
Determines best management for pt
Can increase or decrease muscle activity
Detects electrical activities
Not a treatment

36

Facilitatory feedback

inc muscle activity

post injury or post op

37

inhibitory feedback

dec muscle activity

hypertonic muscles

38

EMG + components

Electricity produced by voluntary movement
Electrical stimulator not needed
Electrodes:
Recording electrode: over muscle being tested
Avoid crosstalk: input from other muscles
Surface EMG
Needle EMG: invasive
Ground electrode: minimize noise

39

Signal amplification and filtration

Minimize distortion
Maximize signal to noise ratio

40

High pass filter

blocks low frequency, 5 Hz/10-20 Hz cut off

41

Low pass filter

blocks high frequency, 500 hz cut off

42

Signal rectification

Absolute value of all signals
Rectification + low pass filter = linear envelope
Process of traditional low pass filter = butterworth or chebyshev

43

Signal smooth

Moving average
Certain amount of data are averaged using sliding window technique
Root mean square
Square root calculation
Reflects mean power of signal
Preferred method

44

EMG can determine

Muscle activation
Muscle fatigue

45

Muscle fatigue index

Identifies weak muscles
Determines effectivity of exercise

46

normal and abnormal EMG at rest

normal: (+) insertion activity, miniature endplate action potentials, no muscle action potentials

abnormal: (+) fibrillations/fasciculations, complex discharges, inc or dec insertional activity

47

normal and abnormal EMG w mild contraction

normal: biphasic or triphasic muscle AP, mup from small amplitude potentions become progressively large amplitude potentials

abnormal: polyphasic, amplitude dec or inc, altered recruitment pattern

48

normal and abnormal EMG with max contraction

normal: inc frequency, (N) step wise, inc interference patterns

abnormal: dec interference pattern, early full interference pattern