D-WAVE
What is a D-wave? Direct waves, It's in the spinal cord. A laminectomy is performed and a four contact strip, like for cortical tumors and dcMEPs is used. It is inserted into the exposed spinal cord either epi or subdural. subdural will give a larger response but it is more invasive/precarious.
Record 2 bipolar channels from the contacts at each end of each electrode. The filters should be set from 100-3000Hz and the gain set not to clip because the signals can be as large as 1000 uV which is 1 millivolt 1 millivolt is 0.001 volt but they can also be much smaller.
Use EP mode, TCS-4 as stimulator average 5-10 traces with 5 or 10 ms/div sweep depending on location and latency. Set the TCS-4 to the lowest level that produces consistent D-wave AND muscle responses (muscle responses in separate tcMEP mode)
Rostral recording is control, caudal recording may be smaller amplitude due to the effect of the tumor, measure the caudal/rostral ratio
If muscle MEP is preserved and D-wave either unchanged or up to 30-50% decrease, postop motor status should be unchanged.
If muscle MEP is lost but D-wave is preserved with no more than 50% decrement, predict transient motor deficit but good long term outcome
If D-Wave shows >50% decrease, high probability of long-term motor deficit
Record 2 bipolar channels from the contacts at each end of each electrode. The filters should be set from 100-3000Hz and the gain set not to clip because the signals can be as large as 1000 uV which is 1 millivolt 1 millivolt is 0.001 volt but they can also be much smaller.
Use EP mode, TCS-4 as stimulator average 5-10 traces with 5 or 10 ms/div sweep depending on location and latency. Set the TCS-4 to the lowest level that produces consistent D-wave AND muscle responses (muscle responses in separate tcMEP mode)
Rostral recording is control, caudal recording may be smaller amplitude due to the effect of the tumor, measure the caudal/rostral ratio
If muscle MEP is preserved and D-wave either unchanged or up to 30-50% decrease, postop motor status should be unchanged.
If muscle MEP is lost but D-wave is preserved with no more than 50% decrement, predict transient motor deficit but good long term outcome
If D-Wave shows >50% decrease, high probability of long-term motor deficit