My name is Maddie, I’m a Fort Smith tech, member of the QA team, and we’re going to go over
what will be a Cadwell refresher for most of you today, along with an introduction to a new
modality for most of you.
Channel Setup
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-Step One-Input Editor
This is where your individual channels live, or where you plug in individual needles. You
have four pods, two amplifiers. You cannot have more than sixteen channels on each
amplifier ENABLED for the system that most of you have. What this means is that if you
have more than 16 channels on the mode group you have selected (SSEP, EMG, etc.)
you will have to go and deselect them. I’ll touch more on this later. The number of
individual inputs isn’t necessarily important.
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The only real consideration with what goes in what “pod” is accessibility to the patient.
You wouldn’t want your head channels on a pod running down to the foot.
Input Editor Step Two
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Within whatever pod and amplifier you’re looking at, click the small drop down icon, and
begin typing what you’re looking for. Functionally, it does not matter what this is called,
just the laterality. The label can be changed to whatever you want later. It’s just to keep
you from confusing yourself 
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These are paired, and will normally pair themselves together in active/reference. If not,
just search for the same thing and add the opposite polarity ( (-) (+) ) below your first
channel.
Channel Editor- Adding Input to Channel
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Once you’ve created your inputs, go to the right side and find your amplifier
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Click the drop down under “active” and find one of your inputs. Then, go to reference,
click the drop down, and find your other input.
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Next to that is the name—you can name your channel whatever you want. Remember to
add innervations 
Channel Editor and Mode Group Errors
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Active and reference must be from the same amplifier- they can be from different
pods, but not one from amp one, and the other from amp two
I’ll touch on this later. If you’re creating a test (this red banner suggests that you
are) this is a real error and you’ll have to disable these channels, or deselect the
mode that they are assigned to
Mode EMG must be included in a test to be included in Mode Group EMG and
EEG- you’ve assigned EMG to a mode, but haven’t included the mode group in
an active test, so it’s throwing this. Seems silly, but that’s what it is
Filters, Settings: Gain
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This is not the same type of display gain that you engage with when you scroll up or
down on an existing waveform. Input editor gain controls how large or small that the
waveform has the capability to display or record at.
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If the waveform is too large or is being clipped, you can increase the display gain. If it’s
too small, you can lower this.
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For SSEPs, usually starts at 10uV/div
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For EMG/MEP, usually starts at 500uV/div
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For To4, usually starts at 5000uV/div
To4 Gain
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Any time you see that boxy morphology on To4 or MEP (it can happen in fEMG too, but
usually with EKG artifact) open up your gain, and it will usually resolve. It’s a bigger deal
with MEPs as far as interpretation, but it certainly helps here, since the amplitude
doubles. I’d say it started at 5,000uV and then increased to 10,000uV
Filters, Settings: HFF/LFF
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Whether it’s high or low cut (frequency) filter, the purpose of these are to attenuate
frequencies that are above or below your desired frequency
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High frequency will attenuate frequencies over what you have it set at. Low frequency
will attenuate frequencies below what you have it set at
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SSEP- HFF=250, LFF=30
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EMG/MEP- HFF=2500, LFF=30
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EEG- HFF=70, LFF=1
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To4- HFF=1000, LFF=10
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TLDR- These are set at frequencies that you wouldn’t *typically* see traces averaging
with frequencies above or below.
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Raise the HFF if you want something higher to come through, lower the HFF for the
same reason.
Filters, Settings: Notch
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Notch is a combination high and low frequency filter designed at a band to filter out 60hz
electrical noise (in the US) and decreases power for the band between 50-60hz
It can be a good tool to have, but it’s relatively controversial, and most neurologists
prefer not to use it, since it can attenuate both the electrical noise and evoked/free run
potentials
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Notch affected the final amplitude and latency of evoked potentials, filtering can result in
considerable distortion of the time course and amplitude of a signal demonstrated
It can also cause ringing artifact in SSEP, tEMG, and some cortical attenuation in
SSEPs, although I believe that’s a little less common
This is another example of distortion, but in tEMG
Mode Controls: SSEP
Sweep-How much data is actually being recorded
Amp Channel/ESU- leave off, can cause rejection
Auto Store- DON’T turn off
Rep rate- not divisible by 6, lower the rep rate, typically better the stimulation
Filter- higher the filter number, the more distortion you’re getting
Invert-If your waveform looks inverted, please fix it . It’s not an aesthetic issue, the waveform will
degrade over time, and the latency can appear to be falsely prolonged or the amplitude
decreased if it’s not the appropriate polarity
Enable- Just whether or not you want it on the screen or not. You can also reach this from the
“gear,” but it will still trace. This is turning off the trace completely
Reject- This is for specific channels (like C5, EP, PF) that have a lot of artifact. You can just turn
that channel’s reject off and leave the cortical channels unaffected
Mode Controls: MEP
Sweep: Tall, myelopathic etc. patients, prolong this to 12-15 for single train if you don’t see an
AH response
Auto lock: don’t turn off
Auto lock duration: how long it remains on
Primary stimulator: Can change the output if you’re doing corticobulbar MEP or if your output is
defective
Polarity: If you can’t get to the head and you’re only seeing contralateral, reverse this
MEP double train
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Pulse count- I like 2 and 7, like Peyton said, 2+7 does not equal 9  This seems to be
the “happy number” of priming vs. stimulating
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ITI- Intertrain interval. Needs to be below 20 or above 100
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(?) for optimal stimulation. This separates priming and stimulation. I like 15ms
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ISI- Interstimulus interval. The amount of time between grouped pulses. 3.5 tends to be
happy for LE, 1.5 tends to be happy for UE, 1.0 or so tends to be happy for face. Play
around and see what works
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Keep polarity the same on both
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Sweep needs to be at least 15 ms/div if you’re doing 15 ms ITI. Proximal UE muscles
can bleed into the stim artifact
Mode controls tEMG
Reject/amp channel- This is really what I want to highlight here. If you’re doing a thyroid or any
other stimulation case, uncheck these, and the “high impedance trials,” it will allow the system to
process every input
I would also suggest, as we said earlier, not leaving the notch filter on channels that are applied
to tEMG to avoid that distortion
Cascade/cadwell Errors:
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These errors can usually be divided into one of two situations: you have a physical
problem with your amplifier (or surrounding components), or Cascade has become
overwhelmed by the demands of life
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No base module connected- sometimes this literally means no base module connected.
Other times the power supply isn’t working, the plug-in to power supply is too
loose/failing, the aux cable has come loose/is failing, or it’s a software failure. It usually
cycles through this if it’s a software failure.
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Amplifier can only support 16 channels- 99% of the time, this means that one of your
physical amplifier connectors isn’t seated well. Unscrew the (tiny) screws, push
everything in to ensure a good connection, screw the (tiny) screws back in.
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Stimulator not connected- either a disconnect of the stimulator cable on the box end, the
amplifier end, or the program is cycling through “base module” physical errors before it
starts
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The initial program itself will not launch- literally turn it off or turn it back on and check
aux cable/power supply. Make sure your software is compatible with the amplifier you’re
using, if the amp is further updated than the computer, it will not launch
Cascade/Program Errors-
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The operation could not be performed while the system loaded configuration into
hardware- most of the time, this is when the program itself has buffered or frozen, and is
cycling back. It should go away on it’s own
ES-IX IBlock warning- amplifier saturation or electrical interference with stimulation, run
impedance to desaturate the amp
Mode failed to initialize without reason- this typically follows the ES-IX IBlock warning
when you run impedance to desaturate the amp, but cautery resumes while impedance
is running. It should go away on it’s own and is something that is typically cycled through
Stimulator output level is low, patient connection may be bad- this is actually helpful,
most of the time. It’s an imbalance in requested versus delivered voltage. However, if
you’re getting this error and your connection is fine, it’s either the port that’s gone out, or
potentially the metallic portion inside of the stimulating leads have gotten bent/broken
and can no longer stimulate effectively. I have also had this happen when the system is
both giving and receiving stimulus information.
Common Forms of Artifact:
What does this look like to anyone?
It’s amplifier saturation, but what makes this a little bit unique is there’s still a couple of channels
in EEG and SSEP that are acquiring noise that looks somewhat like a waveform, so that can be
confused with an issue without context
What does this look like to anyone?
It could be one of a few things, but the defining feature here is that the one channel that is clean
is Cz-Fz, so you’re not getting as much noise from the temporalis, frontalis, masseter in that
channel as you are the channels that aren’t referenced to Cz. This requires context clues as
well, if the patient has no myogenic artifact in any other modality, no blood pressure increase, is
isoelectric, has been stable throughout the case, you’re probably looking at an electrical issue
What does this look like to anyone?
Noise, someone touching wires, poor impedance? It’s actually nothing plugged in at all. The pod
is still connected to the amplifier, but there’s no needle plugged in. It looks scarily like real data,
so always go visually verify that your needles are still in
What does this look like to anyone?
For context, this was a thoracic lam with kypho, I think for malignancy. With that history, I
thought this was real, but as you can see, it’s very cyclical and too rhythmic. Given the channels
and location, where do you think it is?
It’s a gastric stimulator. I had no medical history on this patient, but eventually figured this out
and confirmed this with a merged medical record.
Let’s talk about transabdominal MEPs quickly
 TaMEPs are elicited by stimulating over the conus medullaris, and thereby, the ventral
nerve roots, directly
 TcMEP activate reduced subset of lower motor neurons whereas TaMEP activate nearly
all spinal nerve fibers (Allison et. al., 2024). There has been some concern about how
you know that you are activating what you think that you are, that’s slightly above my
pay grade, but I would venture to say that you are getting some current spread from
what I’ve seen
 Relatively resistant to anesthesia, think D-wave (there are differences in terms of
averaging, why/how/where you run them, but they are both nonsynaptic) whereas
TcMEPs are sensitive due to number of synapses
 ONLY pertains to lumbar, L2 or below; no cervicothoracic applications
 Should be used in conjunction with TcMEPs as a form of control
DIY: TAMEP
 Anode-single large ground sticky pad at umbilicus
 Cathode-two needle electrodes “directly caudal to the tip of the conus medullaris,” at L12, straddling spinous process
 1 pulse, ~300V, 3.5ISI
 Use a separate cord and output, reserving one for TcMEP
TAMEP Execution Notes:
 Need fluoro for these, especially on higher BMI patients; can palpate from T12 rib and
count spinous processes, but easier to fluoro. I ended up slightly more distal (not
markedly so where my results were impacted or where I would just be getting current
spread) and slightly eccentric to one side
 Positive correlation with voltage and BMI (Allison et. al., 2024). Higher BMI, higher
stimulation
 Use Tegaderm for anterior and posterior leads, prep over posterior leads. For posterior
fusions (not lateral) the surgeon you’re working with will have to be okay with these in
the prep field
 Can reverse polarity if you’re not getting response you think you should be
 These could hypothetically move if they expose and manipulate the fascia around it (I
had this concern, luckily didn’t happen) I think it is of more concern for large open
fusions vs MIS exposures
 These would be much more helpful for something like a lateral paired with saphenous
SSEP
 Be mindful of movement; causes kind of “dolphin jump”, have surgeon remove hands
 Make sure you’re using them in indicated procedures as to not supersede MEP consent.
You wouldn’t want to run this on anything it’s not specifically indicated for, or it would be
considered more experimental and unnecessary