Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

123 Cards in this Set

  • Front
  • Back
Define orthodromic
when impulse travels the same way it would physiologically
Define antidromic
when impulse travels opposite the way it would physiologically
4 major uses for electrodiagnostics (reasons to order)
1. diagnosis
2. localization
3. help determine treatment
4. prognosis
3 major types of EMG needles
1. monopolar
2. bipolar
3. concentric
Role of filters (most generally)
faithfully reproduce the signal you want while trying to exclude both high and low frequency electrical noise
As sensitivity is increased, onset latency
Typical conduction velocity in a myelinated nerve
40-70 m/sec
Typical conduction velocity in an unmyelinated nerve
1-5 m/sec
Conduction block = neur____
Conduction slowing and conduction block are indicative of
Normal conduction velocity in upper extremity (general)
50 m/sec
Normal conduction velocity in lower extremity (general)
40 m/sec
CMAP amplitude is dependent on these 3 general factors
1. integrity of the axons
2. muscle fibers depolarized by axons
3. conduction velocity of individual fibers
Motor nerve amplitudes are measured in
Sensory nerve amplitudes are measured in
Is temporal dispersion seen in congenital neuropathies?
not usually
True or false, in general the cathode is placed towards the direction of stimulation?
Optimal separation distance for active and reference electrodes in SNAPs
General placement of the ground electrode
between the stimulation and the recording electrode
In H-reflex we use _____maximal stimulation
What happens to the H-reflex with supramaximal stimulation
it dissapears (replaced by M-wave)
H-reflexes in S1 are often absent in normal individuals over the age of ___
Formula for the f-wave ratio
(F-wave latency - CMAP latency) - 1ms/(CMAP latency x2)
Normal F-wave ratio in upper limb
1.0 +/- 0.3
Normal F-wave ratio in lower limb
1.1 +/- 0.3
An f-wave ratio higher than 1.3 indicates
a proximal lesion
An f-wave ratio lower than 0.7 indicates
a distal lesion
For motor studies, normal stimulation site differences for amplitude may be around ___
How can you verify that a low amplitude is from segmental demylination and resultant temporal dispersion?
the area under the curve should be unchanged
Skin measurements appear to be accurate to about what factor?
How can you estimate the % of axonal motor loss?
Compare the amplitude to the other side
When stimulating the ulnar nerve, the elbow should be
flexed 70-90 degrees
Type of synapse in the H-reflex
monosynaptic (or oligosynaptic)
Type of synapse in the F-wave
Sensory and motor pathway directions in H-reflex
Sensory orthodromic
Motor antidromic
Sensory and motor pathway directions in F-wave
Motor antidromic
Motor rothodromic
Stimulus required in H-reflex
Stimulus required in F-wave
Where can the H-reflex be normally elicited?
flexor carpi radialis
Where can the F-wave be normally elicited?
most muscles (distal preferred)
Where is the stimulus cathode places for the H-reflex?
Where is the stimulus cathode places for the f-wave?
What is the size of the H-reflex compared to the m-wave?
What is the size of the F-wave compared to the m-wave?
What facilitates the H-reflex?
* anything that increases motor-neuron pool excitability (contraction, CNS lesion)
What facilitates the f-wave?
facilitation does not apply here
Two major uses of the H-reflex
S1 radiculopathy
3 major uses of the F-wave
Demyelinating polyneuropathies
Proximal nerve/root injury
Reproducibility of the H-reflex
latency and configuration reproducible, amplitude varies depending on stimulation
Reproducibility of the F-wave
variable in amplitude, latency and configuration
What's the general guide for upper limit of ok side-to-side difference for H-reflex?
What's the general guide for upper limit of ok side-to-side difference for f-wave in hand, calf and foot?
hand: >2 msec
calf: >3 msec
foot: > 4 msec
What do F-wave ratios assume for distance?
That the distance of stimulation is halfway between distal site and spinal cord (elbow or knee)
Overall muscle contraction is from _____fusal fibers
Intracellular resting potential of extrafusal fibers
Fundamental structure assessed during EMG
the motor unit
What makes up a motor unit?
Anterior horn cell; axon; all muscle fibers that that axon innervates
Motor unit architecture refers to its:
size, distribution and endplate area
Which type of motor units fire first?
Type I, smallest
In EMG the needle is the ____ electrode
The reference for EMG should be placed
over the muscle being tested
The ground for EMG can be placed
anywhere on the extremity being tested
A monopolar needle records the voltage differences between
the needle tip and the reference electrode
Which registers a larger potential - a monopolar or concentric needle?
A monopolar needle electrode picks up from a ____ degree field
A concentric needle electrode picks up from a ____ degree field
Which registers more polyphasicity- a monopolar or concentric needle?
4 parts to the EMG
1. insertional activity
2. muscle at rest
3. analyze motor unit
4. recruitment
Basic filter and amplifier settings to check prior to starting EMG
- low freq filter 10-30 Hz
- high filter 10,000-20,000 Hz
- amplifier sensitivity 50-100 microvolts per division
- sweep 10ms per division
Inserting a needle into atrophied muscle often feels like inserting the needle into
Insertional activity that lasts longer than ____ ms is considered increased
List 4 examples of spontaneous activity generated by muscle
- fibrillation potentials
- positive sharp wave
- myotonic discharges
- complex repetitive discharges
List 6 examples of spontaneous activity generated by nerve
- myokymic discharges
- cramps
- neuromyotonic discharges
- tremors
- multiples
- fasciluations (may be mm or nerve)
Gain on EMG for looking at sponateous activity often needs to be set at
7 examples of chronic muscle disorders associated with positive sharp waves and fibrillation potentials
- inflammatory myopathies
- muscular dystrophies
- inclusion body myositis
- cogenital myopathies
- rhabdomyolysis
- muscle trauma
- trichinosis
6 examples of neurogenic disorders associate with positive sharp waves and fibrillation potentials
- radiculopathy
- axonal peripheral neuropathy
- plexopathies
- entrapment neuropathies
- motor neuron disease
- mononeuropathies
5 examples of chronic muscle disorders associated with complex repetitive discharges
- myopathies
- inflammatory processes
- limb-girdle dystrophy
- myxedema
- Schwartz-Jampel syndrome
5 examples of neurogenic disorders associated with complex repetitive discharges
- chronic myopathy or radiculopathy
- poliomyelitis
- spinal muscular atrophy
- motor neuron disease
- hereditary neuropathies
Complex repetitive discharges are suggestive that the lesion is more than ____ old.
6 months
Clinical correlation of myotonic discharges on EMG
delayed muscle relaxation after a forceful contraction
7 examples of disorders associated with myotonic discharges
- myotonic dystrophy
- myotonia congenita
- paramyotonia
- hyperkalemic periodic paralysis
- polymyositis
- acid maltase deficiency
- chronic radiculopathy/neuropathy
5 examples of disorders associated with myokymic discharges
Facial muscles:
- Bell's palsy
- multiple sclerosis
- polyradiculopathy
- chronic nerve lesions
- radiation plexopathy
3 things that tell you you are likely in the endplate region
1. Miniature endplate potentials
2. Endplate spikes
3. Pain
MEPPs represent
spontaneous release of Ach from the presynaptic terminal and the resultant local depolarization
Endplate spikes represent
single muscle fiber depolarizations
What do positive waves mean when they are found in the endplate?
They are likely a normal finding and interpretation otherwise is not wise
What should you do if you find yourself in the endplate?
Get out; either by withdrawing needle or advancing firmly
Typical sweep speed and gain during minimal contraction during EMG?
sweep 10msec/div
gain 200-500 microvolts
4 parameters to evaluate the components of motor unit action potential morphology
1. amplitude
2. rise time
3. duration
4. phases
MUAP amplitude is measured from
most positive to most negative peak
Acceptable rise time on MUAP is ___msec or less
Duration is measured as
the initial departure from baseline to the return to baseline
Normal MUAP duration (general)
5-15 msec
Why is MUAP duration often decreased in myopathies?
Because there are fewer muscle fibers available to contribute to the MUAP.
2 major ways of counting phases:
1. the number of times it crosses the basline
2. the peaks and valleys across baseline +1
Which is a better measure of pathology, motor unit duration or polyphasicity?
Name the two ways that a muscle contraction can become stronger
1. the same motor unit fires faster
2. additional motor units fire
The INITIAL motor unit firing (patient just thinking about moving the muscle) is often
2-3 Hz and irregular; switches to regular when at 5 Hz
How do you find the recruitment ratio?
Hz of fastest motor unit divided by the number of motor units
MUAP recruitment ratio above 8 suggests
neuropathic process
MUAP recruitment ratio less than 3 suggests a
myopathic process
Why is it difficult to evaluate type II motor fibers on EMG?
By the time type II fibers are recruited the baseline is obscured by the activity of type I fibers
Why might EMG be normal in a patient with a steroid myopathy?
Steroid myopathy typically involves type II fibers which are not easily studied on EMG
What are the three types of nerve injury in the Seddon classification of nerve injuries?
- neurapraxia
- axonotmesis
- neurotmesis
What is neurapraxia?
Damage to the myelin
Damage to myelin is called
What is axonotmesis
injury only affecting the nerve's axons
An injury only affecting the nerve's axons is called
What is neurotmesis?
injury affects the myelin, axons and all supporting structures
injury that affects the myelin, axons and all supporting structures is labeled
Name the 4 general categories of demyelinating injuries
1. uniform demyelination
2. segmental demyelination
3. focal nerve slowing
4. conduction block
Where is uniform demyelination typically seen?
in hereditary disorders such as Charcot-Marie-Tooth disease
Clinically, conduction block should present as
In a pure neurapraxia, EMG testing will be
normal (unless conduction block is present)
What would EMG show if there is conduction block?
decreased recruitment
How fast do peripheral nerve axons regrow?
1mm/day, 1 inch per month
Effect of cold temp on latency
prolonged (0.2 ms/degree C)
Effect of cold on amplitude
increased (sensory more than motor)
Effect of cold on conduction velocity
decreased (1.8-2.4 m/s/degree C)
Effect of cold on duration
Repetitive nerve stimulation in a patient with NMJ disease is likely to be _____ if they are cold
General temperature goals in NCS
- upper limb: above 32C
- lower limb: above 30C
Positive initial deflection in CMAP with median nerve stimulation at the wrist should prompt consideration of
Martin-Gruber Anastomosis