Spinal Cord Stimulator Trial – Technique and Overview

Name of Procedure

  • Percutaneous Spinal Cord Stimulator (SCS) Lead Placement

Sample Opnote

Goal

To place midline (as opposed to dorsal root ganglion) spinal cord stimulator leads as part of a trial phase before a spinal cord stimulator implant.

Indications

A variety of pain can be treated with spinal cord stimulators but commonly for radicular pain, CRPS, peripheral neuropathy.

Contraindications

Anatomy

coming soon…

Equipment/Skills/Setup

Typically spinal cord stimulator trials are placed with the kit provided by the manufacturer and everything needed should be in there. Special items and suggested setup for this procedure:

  • 10cc 1% lidocaine in a 10cc syringe attached to a 25g x 1.5″ hypodermic needle for subcutaneous local anesthetic
  • 1-2 14g tuohy needles for epidural space access
  • Device supplies (leads, anchor devices)

Landmarks and Patient Positioning

Position the patient in a basic prone position so that the bottom of the c-arm can go under the table below the lumbar and thoracic spine. For the purposes of this article we’ll focus on stimulators for low back and leg pain.

Technique

Overview

There are a few levels to keep in mind:

  • Where the top of your stimulator leads need to land. This depends on the individual patient. Typically they’ll land around T8-T10. Higher pain means higher lead placement. Also, exact position might be determined by feedback from the patient during the procedure (details below)
  • The epidural access point. You’ll enter an interspace, perhaps somewhere around the low thoracic or high lumbar area.
  • The skin entry point. Like any epidural injection you can enter the skin anywhere around your interspace, but your trajectory might affect your ability to place your lead:
    • Entering lower allows for a “flat” approach and might help a lead slide out along the same trajectory as the needle and smoothly continue that trajectory up the epidural space.
    • Entering the skin right above the interspace leads might require the lead to take a sharper turn when exiting the needle and trying to thread superiorly.
    • Entering far lateral might cause the lead to cross over while threading (ie, if you start on the left and your needle is pointing lateral to medial when it accesses the epidural space, the lead might continue to go towards the right side while threading.)

Steps

  1. Obtain a simple AP view of the low thoracic and upper lumbar spine.
  2. Choose an interspace to access the epidural space. Choice depends on the above factors and if you’re placing one or two leads. We’ll assume we’re placing 2 leads so we’ll place a left and right epidural needle:
    1. Enter the skin around L3-L4. So anesthetize there just left of midline and aim towards the L1-L2 space.
    2. Insert the tuohy needle and aim for the L3-L4 interspace
    3. Use your typical desired technique here. Either hit lamina at L2 and walk off, or if you have good feedback and sense of depth, just aim straight to the interspace
    4. Continue with loss of resistance to access the epidural space.
  3. Insert the first lead and advance till you feel it just exit the needle
    1. You’ll advance it under live fluoroscopy, while twisting/steering with the stylet till it’s in it’s final destination
    2. This is the part of the procedure that can be the most difficult and mostly takes practice (see some tips below)
    3. You’ll aim to get this lead as the left paramedian lead.
  4. Once the top of the lead is at your target you simply repeat steps 2 and 3 above to place a right paramedian lead.
  1. From here you’ll start to hook the leads up the manufacturer’s connector, which in turn is connected with the device rep’s controller.
    1. While the rep is getting things setup, this is a good time to check an lateral view to confirm posterior lead placement
  1. Ideally anesthesia has been timing a wakeup around now so the rep can turn on stimulation and see if the leads are placed correctly:
    1. The rep will be asking the patient for feedback to see if your lead placement can provide coverage over the patient’s desired area.
    2. A knowledgeable rep will often be able to suggest specific lead adjustments based on feedback.
    3. After making appropriate adjustment you may test again or if the rep is confident the changes are likely to be sufficient, you may be finished with lead placement.
  2. Take an AP fluoroscopy view. This will act as your reference picture to know where your leads are supposed to be.
  3. You will know simply pull the tuohy needles and simultaneously pull the stylets out, while keeping the leads in their exact spot.
    1. TIP: Advance the leads a bit while pulling the stylet/needle. Once the stylet/needle are out you might not be able to advance the leads. So if you pulled the lead accidently while pulling the stylet/needle you won’t have a way to advance it again. But if it’s advanced past it’s original position you can always pull it back easily without a stylet/needle in and it will usually pull back to it’s original positioning.
    2. After pulling take another AP view and compare it to your reference picture to make sure you didn’t move the leads.
    3. As noted above, if it moved you can pull it slightly to it’s original position.
  4. There is usually some kind of anchoring tape that you can put the leads into that tapes onto the patient’s back (manufacturer specific). This keeps the leads secure and clean during the trial. Make sure the surgical area is clean and dry before applying the full dressing to prevent migration, dressing disintegration, and infection during the trial.
  5. Usually from here the patient can recover in post op and start to work with the rep on initial programming of the stimulator. Most work after this is between the rep and patient to try and optimize the SCS function during the trial.

Tips

Several factors can complicate lead steering/placement:

  1. There may be random areas of resistance even when the lead is in the appropriate posterior epidural space. Sometimes simply pulling and advancing the lead in repetitive small movements, with minor adjustments in steering, will help you to move past or around these pockets.
    1. Sometimes you may find that your lead moves far lateral (in either direction) while advancing and then you are able to steer it back to midline. This might be a problem.
      1. Remember to think 3-dimensionally. You may have advanced the lead around the side and into the anterior epidural space.
      2. A lateral right here might be useful. If you don’t check now you might waste time trying to get your lead in it’s final spot in an AP view only to find it’s in the anterior space
  2. Sometimes a lead will simply “want” to go to one side, despite your intention to put it on the other side.
    1. If it easily goes to one side it might be best to simply keep it on that side and then see if your other lead will go to the contralateral side.
    2. (ie, you put a left paramedial tuohy needle but the lead only advances easily to the right paramedian space. Just take it, and place a right paramedian tuohy and see if that lead will go to the left paramedian space.)
  3. The aperture of the tuohy needle might effect lead direction.
    1. If your lead is exiting the tuohy needle in an undesired direction, pull the lead back into the needle. Then rotate the tuohy needle so the aperture faces the direction you want the lead to travel, then try re-advancing and see if that helps.
  4. In the technique above you place the first tuohy and then place the first lead. Sometimes this first lead isn’t advancing where you want it to.
    1. Try keeping this first needle where it is. don’t advance any lead. Then place the second tuohy needle, advance the 2nd lead through that needle. Then come back to the first needle and try advancing the lead through it again. The second lead may act as an obstacle and re-direct your first lead where you want it.
  5. Sometimes your angle of approach on the tuohy needle is simply not optimal and you can’t get the lead to go where you want.
    1. Try re-accessing the epidural space
    2. A slight re-adjustment of the angle/trajectory can be enough
    3. Sometimes picking a different interspace or skin entry point might be necessary
  6. Sometimes getting a second lead placed correctly is failing despite all these efforts. You can try the wake/patient test with one lead and see if it’s sufficient to cover the desired area. If it is you might be able to trial with just one lead.
  7. The tuohy needle aperture may not be entirely in the epidural space.
    1. These are large needles, so when you get loss of resistance the needle tip may not be fully in the space. Then when you go to advance the lead you’ll get resistance and it won’t exit the needle tip.
    2. Advancing the needle slightly can solve this.

References

  1. Spinal Cord Stimulation Technique
  2. Spinal Cord Stimulators: Typical Positioning and Postsurgical Complications