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electrodiagnosis 2 - Coggle Diagram
electrodiagnosis 2
Electromyography
- the procedure of recording the electrical activity of the ms is called electromyography
- the record is electromyograph.
Equipment
EMG machine
-
recording electrodes
- surface electrodes
-ring or disk electrodes,
-disposable or non-disposable
- needle electrodes:
-monopolar
-bipolar
-or concentric
EMG
- Active (needle electrode)
- reference (surface electrode)
- ground (surface electrode)
-
amplifiers
- magnify the signal so that it can be displayed
- preamplifiers attenuate the biological signal before it gets to the amplifier
filters
are used to reproduce the signal we want while trying ti exclude both high & low frequency electrical noise
-
EMG examination
can be divided unto 4 components
- insertional activity
- examination of ms at rest
- analyzing the motor unit
- recruitment
1.insertional activity
- if the needle is properly placed the ms you are testing you will hear & see brief electrical activity associated with the needle movement.
this is called insertional activity
- the sound associated with this needle movement has been described as ' crisp' & it's temporally related to the high-frequency positive response & negative spikes that are easily visualized on the monitor.
- normal insertional activity typically only lasts a few hundred milisecs, just barely longer than the needle movement itself
- decreased insertional activity occurs when the needle is inserted into an atrophied ms
- increased insertional activity may occur
when there is ms pathology
& is evidenced by
the presence of positive sharp waves
& sometimes fibrillation potentials that are apparent only on insertion & do not persist.
- 1 more item...
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recruitment
Recruitment refers to the orderly addition of motor units
so as to
increase the force of a contraction.
A contraction becomes stronger in 2 ways:
- the firing motor units incr their rate of firing
- additional motor units commence firing.
- Normally the motor unit will fire in a regular pattern at about 5Hz.
- At around 10 Hz - another MUAP will be recruited to fire.
Neuropathic recruitment, also called neurogenic recruitment, can be seen in:
- neuropathies,
- radiculopathies,
- motor neuron disease and
- nerve trauma.
Few motor units fire at an
- increased rate, or firing frequency.
- The firing rates of these MUAPs are greater than 20 Hz (20 cycles per second)
and may increase to over 30 Hz or more.
Myopathic MUAPs
tend to have an early recruitment of
- short duration low amplitude MUAPs
- firing at increased rates.
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