CNIM - Certificate Neurophysiologic Intraoperative Monitoring
Terminology
|
|
|
Auditory Terminology
- acoustic neuroma
*from handwritten notes at chucks house*
dB = 20 log E1/E2; the voltage ratio (six zeroes = 120)
common mode rejection ratio
waveform polarity and polarity of the amplifier inputs
polarity convention of amplifier inputs
default convention is negative up; wave 1 of BAEP
square root of the number of trials averaged; square root of 100 responses equals ten
avoid signals that are a multiple of 60Hz; 60 cycles per second will interfere
SSEP's at a range where time is a factor; say stimulator is at 4 times per second and 2 minutes is a practical setting (120 secs = 500 trials)
2 or 300 is better; I've seen some people get excellent SSEP's at 50 trials, initally set for 200
stimulation time and intensity
extra ocular muscles
vagus monitoring and vocal chords
what is the effect of mis-positioning electrode position? a small change makes a big change in the potential; electrode position is extremely critical
N20 near field cortical medial ulnar
N34 response at the medulla; subcortical somatosensory response to tibial stimulation
far field and near field
major potentials - N20 - primary cortical response
P40 or P37 - primary cortical response to tibial stimulation
6 ms earlier P31, P34 are subcortical potentials
Amplifiers; gain - how many times the amplifier
high pass filter - passes high and blocks low; place capacitor
low pass filters - place inductor
capacitance - passes AC blocks DC
Inductance - Passes DC blocks AC
resistance - passes AC, passes DC
Impedance is a function of frequency
can clean up by bringing high pass filter
Band pass filters - 50-300 for SSEP's
electrodes - more voltage to the same current
Dwaves - subdural
referential recording - as opposite
bipolar recording
C3 - CZ - left posterior for right hemisphere; electrode placement; dendritic axons
ground is to minimize stimulus artifact between stimulation and recording sites; you want it to be closer to the stimulation site
T5 Spine afferent voltage at the popliteal fossa
the higher the resistance the less the current which equals a poorer signal
important that they're balanced because common mode rejection - balanced and low
surface electrodes; paste; subcutaneous are more reliable
nyquist theorem
highest frequency for EEG is 70 so need to measured at 140
human hearing is 20-20,000 Hz so for, sampling is 441 = obeys nyquist @ 2x
safe levels for EMG; signal of interest overlaps, distribution to EKG
ABR - already decreases example
SEP 3-10ms
MEP 50-1000hz
EEG slow D wave more than 1 second
EMG compound muscle action potentials
all signals are constantly present
to avoid aliasing, sample at or above the nyquist and aliasing
what determines max frequency constant
get rid of frequencies before analog to digital conversion
ACNS guidelines
monitoring for position, for spinal cord SEPs and EMGs
4 extremities for control and to monitor and test if upper extremities connection are not lost
younger people the spinal cord is lower; higher in older people unless it's tethered
possible correlation with the actual height and individual differences
what is at risk???
Dwaves are cortical; this is the action potential traveling down the spinal cord; they are not able to be lateralized
orthodromic - stimulating backward
record directly from muscle
Bowel & Bladder function is most important to be able to walk and go to the bathroom
Healthy stimulation is at 0.5 mA (milliamps) *Chuck uses 1mA at some arbitrary cutoff
Looking for amplitude changes between rostral and caudal Dwave electrodes
Myotome
Remember it's the difference in potential between active and reference also the first is a negative/upward deflection
gain output/input x amp max sensitivity is small number 10 microvolt is fine for?????
*the latency is efferent for upper and lower extremities
no notch filter because it's right at the frequencey we're looking for, essentially a huge valley right at where the mark is
recruiting
for EMG activity you go from 1000 high cut to 70 for the EMG
biggest MEP is about 1000 microvolts or even 5000 microvolt
so 50 microvolt for lower extremities is good because these are smaller potentials
dB = 20 log E1/E2; the voltage ratio (six zeroes = 120)
common mode rejection ratio
waveform polarity and polarity of the amplifier inputs
polarity convention of amplifier inputs
default convention is negative up; wave 1 of BAEP
square root of the number of trials averaged; square root of 100 responses equals ten
avoid signals that are a multiple of 60Hz; 60 cycles per second will interfere
SSEP's at a range where time is a factor; say stimulator is at 4 times per second and 2 minutes is a practical setting (120 secs = 500 trials)
2 or 300 is better; I've seen some people get excellent SSEP's at 50 trials, initally set for 200
stimulation time and intensity
extra ocular muscles
vagus monitoring and vocal chords
what is the effect of mis-positioning electrode position? a small change makes a big change in the potential; electrode position is extremely critical
N20 near field cortical medial ulnar
N34 response at the medulla; subcortical somatosensory response to tibial stimulation
far field and near field
major potentials - N20 - primary cortical response
P40 or P37 - primary cortical response to tibial stimulation
6 ms earlier P31, P34 are subcortical potentials
Amplifiers; gain - how many times the amplifier
high pass filter - passes high and blocks low; place capacitor
low pass filters - place inductor
capacitance - passes AC blocks DC
Inductance - Passes DC blocks AC
resistance - passes AC, passes DC
Impedance is a function of frequency
can clean up by bringing high pass filter
Band pass filters - 50-300 for SSEP's
- passes dominant frequencies
- eliminate frequencies outs of that
- improve signal to noise ratio
electrodes - more voltage to the same current
Dwaves - subdural
referential recording - as opposite
bipolar recording
C3 - CZ - left posterior for right hemisphere; electrode placement; dendritic axons
ground is to minimize stimulus artifact between stimulation and recording sites; you want it to be closer to the stimulation site
T5 Spine afferent voltage at the popliteal fossa
the higher the resistance the less the current which equals a poorer signal
important that they're balanced because common mode rejection - balanced and low
surface electrodes; paste; subcutaneous are more reliable
nyquist theorem
highest frequency for EEG is 70 so need to measured at 140
human hearing is 20-20,000 Hz so for, sampling is 441 = obeys nyquist @ 2x
safe levels for EMG; signal of interest overlaps, distribution to EKG
ABR - already decreases example
SEP 3-10ms
MEP 50-1000hz
EEG slow D wave more than 1 second
EMG compound muscle action potentials
all signals are constantly present
to avoid aliasing, sample at or above the nyquist and aliasing
what determines max frequency constant
get rid of frequencies before analog to digital conversion
ACNS guidelines
monitoring for position, for spinal cord SEPs and EMGs
4 extremities for control and to monitor and test if upper extremities connection are not lost
younger people the spinal cord is lower; higher in older people unless it's tethered
possible correlation with the actual height and individual differences
what is at risk???
- patient positioning
- upper extremities
- lower extremities
Dwaves are cortical; this is the action potential traveling down the spinal cord; they are not able to be lateralized
- ball tip stimulator
- close to the ???
- stimulates across from left to right
orthodromic - stimulating backward
record directly from muscle
Bowel & Bladder function is most important to be able to walk and go to the bathroom
Healthy stimulation is at 0.5 mA (milliamps) *Chuck uses 1mA at some arbitrary cutoff
Looking for amplitude changes between rostral and caudal Dwave electrodes
Myotome
Remember it's the difference in potential between active and reference also the first is a negative/upward deflection
gain output/input x amp max sensitivity is small number 10 microvolt is fine for?????
*the latency is efferent for upper and lower extremities
no notch filter because it's right at the frequencey we're looking for, essentially a huge valley right at where the mark is
recruiting
for EMG activity you go from 1000 high cut to 70 for the EMG
biggest MEP is about 1000 microvolts or even 5000 microvolt
so 50 microvolt for lower extremities is good because these are smaller potentials
- but you can use 100 microvolt for the hands because these can get high activity
Papers mentioned in CNIM Packet
Isley Balzer Intraoperative Motor Evoked Potentials American Journal of Electroneurodiagnostic Technology