Flashcards in electrophysio exam Deck (48)
Loading flashcards...
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
