Spinal Cord Dorsal Column Mapping
Record from all muscle groups distal to tumor, 5-10 ms/div, same filter/gain/stim settings as EMG. Stimulate with 1mm ball-tip probe as cathode, anode in skin rostral to incision. Have the surgeon hold the probe in location clearly lateral to one side or the other, stim with 0.2 ms duration pulses, 3-5/sec, determine threshold for unilateral response.
Move the stim probe to the other side, confirm get response from ipsilateral muscles on each side. Now move the probe across the midline, find transition point from one side to the other, may get bilateral responses in lower extremities at midline.
REPEAT at several levels since midline may be distorted! once the midline is established, record PTN seps during myelootomy, ideally will remain intact although may be decreased when sutures are placed to hold the midline incision open.
Move the stim probe to the other side, confirm get response from ipsilateral muscles on each side. Now move the probe across the midline, find transition point from one side to the other, may get bilateral responses in lower extremities at midline.
REPEAT at several levels since midline may be distorted! once the midline is established, record PTN seps during myelootomy, ideally will remain intact although may be decreased when sutures are placed to hold the midline incision open.