Term
|
Definition
|
|
Term
| in what direction does an orthodromic M wave travel |
|
Definition
| from central to peripheral |
|
|
Term
| what is done and measured in M wave testing |
|
Definition
| we create an orthodromic action potential and measure the motor nerve |
|
|
Term
| setup of recording electrodes for motor NCV |
|
Definition
| ground electrode on back of hand/elsewhere; cathod on motor point; anode distal to cathod |
|
|
Term
| why is the cathode chosen as the active electrode |
|
Definition
| Pflueger's Law: for a given amount of electricity, you will get more activity under a cathode than you will under an anode because of resistance of the nerves |
|
|
Term
| does position of cathode/anode matter for biphasic balanced or pulsed monophasic? |
|
Definition
|
|
Term
| what waveform is used in NCV |
|
Definition
|
|
Term
| what does placement of stimulating electrodes in M wave NCV depend on? |
|
Definition
| depends on location of Nerve/segment being studied |
|
|
Term
| how many action potentials does the stimulating cathode set off? |
|
Definition
|
|
Term
| in m waves, what happens to the action potential that travels distally from the cathode |
|
Definition
| goes down the nerve orthodromically and is picked up and read by the recording/bar electrode |
|
|
Term
| how many action potentials does the stimulating anode set off? |
|
Definition
|
|
Term
| in m waves, what happens to the action potential that travels proximally from the anode |
|
Definition
| goes to anterior horn of spinal cord, hits the cell body, and dies out |
|
|
Term
| what action potential do we record and measure in m waves |
|
Definition
| the one that travels distally from the cathode |
|
|
Term
| in m waves, what happens to the action potential that travels proximally from the cathode and the action potential that travels distally from the anode |
|
Definition
| they hit each other and die out |
|
|
Term
| purpose of ground electrode |
|
Definition
| negate other electrical signals |
|
|
Term
| at what point in M wave EMG do you know you have the right wave |
|
Definition
| supramaximal; can't go any higher |
|
|
Term
| why do you need a supramaximal response for M wave NCV |
|
Definition
| insures that all motor nerves of the mixed nerve are activated including all slow and fast twitch motor units |
|
|
Term
|
Definition
| time from initiating stimulus from the cathode to first recording of response |
|
|
Term
| what do we look for in m wave NCV graph? |
|
Definition
| amplitude, shape, distal latency |
|
|
Term
| how to measure velocity using M wave |
|
Definition
| distance between cathodes/distal lateny |
|
|
Term
| how can the frequency of the oscilloscope affect your measurement |
|
Definition
| the oscilliscope has a frequency of 50 hz, meaning it refreshes 50 times asecond. It's possible that your action potential could occur during the time that the screen is refreshing. You have to be sure that the line being drawn on the screen is syncrhonized to the stimulator |
|
|
Term
| how to measure velocity at proximal portion of nerve using M wave |
|
Definition
| distance between stimulator sites/latency 2 - latency 1 |
|
|
Term
| when to be concerned with m waves |
|
Definition
| if the conduction velocities are slower than normal or if the shape changes |
|
|
Term
| what to do if NCV is slow |
|
Definition
| send findings to physician |
|
|
Term
| indications for motor NCV |
|
Definition
| peripheral neuropathies, such as disc protruding and pressing on nerve |
|
|
Term
|
Definition
| motor test for when you can't go farther up the nerve proximally because of space |
|
|
Term
| what is the position of the cathode/anode on the recording electrode for an F wave |
|
Definition
| cathode on motor point, anode distal |
|
|
Term
| what is the position of the cathode/anode on the stimulating electrode for an F wave |
|
Definition
| cathode proximal, anode distal |
|
|
Term
| is the cathode positive or negative |
|
Definition
|
|
Term
| which action potential are we interested in in F waves |
|
Definition
| cathode sends action potentials up the motor nerve antidromically |
|
|
Term
| what is the path of the action potential sent antidromically to the CNS by the stimulating cathode |
|
Definition
| travels into the anterior horn of spinal cord, hits the cell bodies. Signal is reflected back down the motor nerve orthodromically. The orthodromic response is measured |
|
|
Term
| what is a possibility for error in F waves |
|
Definition
| nerves don't always respond; don't always get enough of a signal reflecting back orthodromically |
|
|
Term
| in particular, what part of the nerve is tested using F waves |
|
Definition
|
|
Term
| describe orthodromic/antidromicnesss of M wave |
|
Definition
| orthodromic stimulus to get an orthodromic response |
|
|
Term
| describe orthodromic/antidromicnesss of F wave |
|
Definition
| antidromic stimulus to get an orthodromic resposne |
|
|
Term
| what happens if you do an F wave with the stimulus too proximal |
|
Definition
| there is a greater likelihood that M and F waves will hit the recording electrode at the same time. The M wave will overshadow the F wave. |
|
|
Term
| what happens if you do an F wave with the stimulus distal |
|
Definition
| the M wave will show up on the recording device very early and the F wave will show up later so that you can tell which one it is. |
|
|
Term
|
Definition
|
|
Term
|
Definition
| proximal neuropathies, Guillian Barre, Charcot Marie Tooth, thoracic outlet syndrome, radiculopathy |
|
|
Term
|
Definition
| attack on anterior horn cells. F wave tells us how much it affects peripheral nerves |
|
|
Term
| what is charcot-marie-tooth |
|
Definition
| central motor responses occur with this. Can be assessed with f wave |
|
|
Term
| what is repetitive stimulating used to assess |
|
Definition
| problems of synapse trnasmission, such as for myasthenia gravis, botulism, some cancer |
|
|
Term
| what is the electrode configuration for repetitive stimulation |
|
Definition
|
|
Term
| how to do repetitive stimulation testing |
|
Definition
| repeated stimulation of motor nerve. Constant stimulator amplitude applied. Measure waves before and after exercise or before and after ischemia |
|
|
Term
| how to determine outcome of repetitive stimulus |
|
Definition
| compare to normal responses |
|
|
Term
| what can cause errors in repetitive stimulus testing |
|
Definition
| drugs, position, temperature |
|
|
Term
|
Definition
| sensory nerve action potential |
|
|
Term
| what is the direction of orthodromic SNAP |
|
Definition
|
|
Term
| what nerves are stimulated by SNAP |
|
Definition
|
|
Term
| what is the direction of antidromic SNAP |
|
Definition
|
|
Term
| what is a disadvantage of antidromic SNAP |
|
Definition
| produces potential movement artifact which can make sensory look bigger than it actually is |
|
|
Term
| how to achieve antidromic SNAP compared to orthodromic SNAP |
|
Definition
| reverse the stimulating and recording electrodes: plug them in oppositely so that recording electrodes are now the stimulating electrodes and vice versa |
|
|
Term
| where are the recording electrodes in SNAP (on the muscle or on the nerve) |
|
Definition
|
|
Term
| what type of stimulating electrodes are used for median nerve |
|
Definition
|
|
Term
| is the stimulating cathode distal or proximal |
|
Definition
|
|
Term
| is the recording cathode distal or proximal |
|
Definition
|
|
Term
| what distance is measured in SNAP |
|
Definition
|
|
Term
| is it easier to get a response in orthodromic or antidromic SNAP in overweight people |
|
Definition
|
|
Term
| is the cathode black or red |
|
Definition
|
|
Term
| does antidromic SNAP stimulate sensory or motor nerves |
|
Definition
|
|
Term
| when do you use antidromic SNAP |
|
Definition
| in overweight people or when orthodromic doesn't work |
|
|
Term
| sensory waves are smaller than motor waves. What do you do if you can't see the wave on the screen |
|
Definition
| adjust the gain to increase sensitivity |
|
|
Term
| what outcomes do we look at for SNAP waves |
|
Definition
| shape, amplitude, time of wave |
|
|
Term
| what do SNAP waves look like |
|
Definition
|
|
Term
| what is the most stable part of a SNAP wave that you should use for measurements |
|
Definition
|
|
Term
|
Definition
| use of orthodromic motor afferent stimulation to produce motor efferent reaction |
|
|
Term
| when is the H reflex typically used |
|
Definition
| in S1 nerve root compression |
|
|
Term
| where are the recording electrodes in H wave |
|
Definition
|
|
Term
| where is the stimulator for H wave |
|
Definition
| tibial nerve at popliteal fossa |
|
|
Term
| what is the H reflex an indicatin for |
|
Definition
|
|
Term
| what affects the H reflex |
|
Definition
|
|
Term
| why is the S1 nerve root used for H reflex |
|
Definition
| soleus is a postural muscle with many muscle spindles. It is easy to get a response out of the soleus. |
|
|
Term
| what is the position of the stimulating cathode in H reflex |
|
Definition
|
|
Term
| what types of action potentials are sent along what types of nerves in H reflex |
|
Definition
| antidromic up motor nerves and orthodromic up sensory nerves |
|
|
Term
| why does the H wave take longer than an M wave in the H reflex |
|
Definition
| H wave has to go up through the spinal cord and back down again. |
|
|
Term
| how does the H wave amplitude change with increase in intensity and why |
|
Definition
| H wave gets smaller as we turn the intensityup because H and M waves collide and cancel each other out |
|
|
Term
| what are sources of error in NCV |
|
Definition
| electrode placement, intensity, measurement, age, temperature |
|
|
Term
| is precise placement of electrodes more essential for motor or sensory readings? |
|
Definition
|
|
Term
| what can happen if your electrode placement is not precisely on motor point, nerve path |
|
Definition
| will affect readings/results |
|
|
Term
| what kind of error is associated with intensity |
|
Definition
| need supra-maximal stimulation to make sure you're getting all the axons in a nerve to fire. Not turning up intensity to supramaximal will give you different numbers of motor units and different readings |
|
|
Term
| what should you take account into measurement of distance to avoid error |
|
Definition
| measure the same way each time for each individual; body position should be recorded for comparison to other tests/norms |
|
|
Term
| how can you avoid measurement errors on the graph |
|
Definition
| print the graph to decrease parallax errors from reading off the oscilloscope |
|
|
Term
| at what age is NCV decreased |
|
Definition
|
|
Term
| at what age is NCV at the low end of normal |
|
Definition
|
|
Term
| what do you need to have to be able to account for age related changes to NCV |
|
Definition
| table for age related changes |
|
|
Term
| what is the greatest source of error in NCV |
|
Definition
|
|
Term
| what is the 2nd greatest source of error in NCV |
|
Definition
|
|
Term
| at what skin temp does NCV begin to slow |
|
Definition
|
|
Term
| what should be the minimum surface temp for NCV |
|
Definition
|
|
Term
| what should be the temp min for repetitive stimulation |
|
Definition
|
|
Term
| what should you establish to reduce error |
|
Definition
|
|
Term
| what are technique electrodes |
|
Definition
| indwelling electrodes; go into the muscle |
|
|
Term
| what equipment differences are there between NCV and technique |
|
Definition
| in technique, you don't need a stimulator. The patient contracts the muscle, and you record what comes out. |
|
|
Term
| when do you take measurements with technique |
|
Definition
| response at insertion; response at rest; response with voluntary contraction |
|
|
Term
| what do you look for in the technique recording |
|
Definition
| amplitude, duration, shape,sound, frequency |
|
|
Term
| how do you reduce error in technique recording that comes from area recorded by needle being so small |
|
Definition
| ssample many areas of the muscle |
|
|
Term
|
Definition
|
|
Term
| what are Saturday night palsies |
|
Definition
| fall asleep laying on one side, that side feels numb when you wake up |
|
|
Term
| what happens with neuropraxias |
|
Definition
| interference of neuroplasmic flow causes damage to outer portion of nerve, slowing down actoin potentials. |
|
|
Term
| what are some examples of neuropraxias |
|
Definition
| Saturday night palsy, carpal tunnel syndrome |
|
|
Term
| how is NCV affected by neuropraxias |
|
Definition
| shows increased latency across blocked area |
|
|
Term
| how is conduction/amplitude affected above and below a neuropraxia |
|
Definition
|
|
Term
| how is EMG affected by neuropraxia |
|
Definition
| depends on duration and level of denervation |
|
|
Term
|
Definition
| intact neural tube in which axonal damage has occurred |
|
|
Term
| what is the result of fewer axons traveling in the compound motor nerve |
|
Definition
| won't get as many motor units to contract |
|
|
Term
| can NCV be normal with axonotmesis |
|
Definition
|
|
Term
|
Definition
| acute trauma, chronic neuropraxia |
|
|
Term
| what part of axonotmesis will cause a decrease in NCV amplitude |
|
Definition
| larger number of axons damaged |
|
|
Term
| as axonotmesis degeneration progresses, what wave changes occur in EMG |
|
Definition
| fibrillation and positive sharp waves |
|
|
Term
|
Definition
| disruption fo neural tube. Full degeneration. Complete disruption. Cut off periphery and CNS. Muscle can't respond because action potentials can't bridge the area of damage. |
|
|
Term
| is there activity with voluntary effort in neurotmesis |
|
Definition
|
|
Term
| does an EMG show any activity in muscle with neurotmesis |
|
Definition
| spontaneous activity in resting muscle |
|
|
Term
|
Definition
| a neuropathy: sensory changes, distal weakness, hyporeflexia |
|
|
Term
| contraindications for NCV/EMG |
|
Definition
| bleeding disorders, anticoagulants, recurrent systemic infections |
|
|
Term
| should you use universal precautions with NCV |
|
Definition
|
|
Term
| what is the display of a normally contracting muscle |
|
Definition
| amplitude, recruitment, and frequency will increase with increased contraction. Baseline obliteration occurs with maximal contractoin |
|
|
Term
| when might abnormal EMG waves show up? |
|
Definition
| myelopathy (diabetes, Guillian Barre), myopathies (dystrophies, polymyositis), motor neuron disorders (polio, ALS), myotonia, myasthenia gravis |
|
|
Term
| what are the acceptable number of polyphasic potentials |
|
Definition
| 10% (abnormal if more than 10%) |
|
|
Term
| what is normal activity with EMG testing |
|
Definition
| noise is heard when needle is inserted, then muscle is silent unless it is at motor end plate, in which case it must be reinserted |
|
|
Term
| what is abnormal activity with testing |
|
Definition
| fibrillation potentials/positive sharp waves; fasciculations/complex discharges |
|
|
Term
| what is normal activity with slight contraction |
|
Definition
| single action potentials, usually biphasic or triphasic |
|
|
Term
| what is abnormal activity with slight contraction |
|
Definition
|
|
Term
| what is normal activity with max contraction |
|
Definition
| obliteration of baseline due to all motr units firing all fibers; increase in frequency, amplitude, and recruitment |
|
|
Term
| what is abnormal activity with max contraction |
|
Definition
| may be decreased activity with max effort and increased activity with decreased effort. May see only a few action potentials firing |
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|
