Prognostic blocks for peripheral neuromodulation

[NJPAIN]

I see many articles for peripheral nerve stimulation in which most if not all of them report a positive response to a block of the same nerve prior to placing the stimulator. I see similar regarding blocking nerve roots and DRG stimulation. At a recent course I had the opportunity to discuss this with a guru that I respect. His response was " the MOA of stim is not the same as a local anesthetic block so it makes no sense to predict a response based on a block. Do you do a spinal to predict response to conventional SCS?”

Interested in everyone's thoughts on this. For instance I had a patient come in with textbook meralgia paresthetica. US block performed to LFCN. The nerve was markedly swollen and surrounded by fluid. Block with 2% lidocaine did NOTHING. Is he now absolutely not a candidate for PNS, DRG, etc?? If I consider DRG do I need to block T12 and L1?

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[lobelsteve]

Like printing money, but not like taking care of the patient.

No MOA.
Does not fit pathoanatomic correlates.

 

[deleted875186]

If no response from a local block, but demonstrative numbness in the distribution and technically successful block, I would not place a PNS.

And yes, a spinal block prior to SCS would relieve pain. Also, we do SCS trials before an implant for this very reason.

 

[Dr. Ice]

I have a similar patient to NJpain..overweight guy with meralgia paresthetica with no response to us guided lfcn block. Anyone have any success with any kind of neuromodulation?

 

[deleted875186]

I have a similar patient to NJpain..overweight guy with meralgia paresthetica with no response to us guided lfcn block. Anyone have any success with any kind of neuromodulation?

I would also be interested. Was thinking gif trying pulsed RF on the LFCN as I have a patient with good effect for about 3 weeks after a nerve block. I don’t have a setup to do PNS, plus it’s bilateral.

 

[lobelsteve]

I have a similar patient to NJpain..overweight guy with meralgia paresthetica with no response to us guided lfcn block. Anyone have any success with any kind of neuromodulation?

I have one with Nevro doing well.
Had resection of nerve at Emory, then came to me.

 

[RoloTomassi]

I would also be interested. Was thinking gif trying pulsed RF on the LFCN as I have a patient with good effect for about 3 weeks after a nerve block. I don’t have a setup to do PNS, plus it’s bilateral.

This is what I would try. Would have to self pay though.

 

[deleted875186]

This is what I would try. Would have to self pay though.

Indeed, it will get denied, I’m probably going to book a nerve block, do the block, and then just do the pulsed after local is in and not charge for it.

 

[callmeanesthesia]

I did a thermal RF for LFCN once, after much discussion of risks with the patient. Neurosurgeon sent him to me as an alternative to anything more invasive. Severe pain after a few minutes of walking. Great temp response to NB.
Responded well to the RF, obviously numb but relieved the pain. Increased ambulation tolerance. Haven’t had to repeat it.
N=1, YMMV…

 

[MitchLevi]

I have one with Nevro doing well.
Had resection of nerve at Emory, then came to me.

...and you called it causalgia and stuck a DRG in him?

 

[lobelsteve]

...and you called it causalgia and stuck a DRG in him?

Nevro standard array.
Chronic intractable pain of the limb.

 

[Orin]

I see many articles for peripheral nerve stimulation in which most if not all of them report a positive response to a block of the same nerve prior to placing the stimulator. I see similar regarding blocking nerve roots and DRG stimulation. At a recent course I had the opportunity to discuss this with a guru that I respect. His response was " the MOA of stim is not the same as a local anesthetic block so it makes no sense to predict a response based on a block. Do you do a spinal to predict response to conventional SCS?”

Interested in everyone's thoughts on this. For instance I had a patient come in with textbook meralgia paresthetica. US block performed to LFCN. The nerve was markedly swollen and surrounded by fluid. Block with 2% lidocaine did NOTHING. Is he now absolutely not a candidate for PNS, DRG, etc?? If I consider DRG do I need to block T12 and L1?

The KOL is correct that they don't work the same way, but conflicted. The data just don't support the block/PNS/SCS correlation for a trial.

I still do the block. I counsel using a stimulating needle while doing the block to verify sensory capture in the distribution of the pain. If that captures the pain pattern, then I would trial PNS even if a block didn't help. If the pain isn't concordant, then don't stim for imaging abnormalities.

In the older days when people did differential blocks, the question really is whether low dose neuraxial blockade/sympathectomy helped, as SCS doesn't really create a true motor or sensory block.

The pressure if the block doesn't work peripherally is to do stimulation more proximally/centrally, but this is all handwaving still.

 

[NJPAIN]

The patient has pain and dense numbness in the distribution of LFCN. After the US guided block he still hand pain and dense numbness. The only indication I could have that block was on target was US. I like the stim Idea as that’s how I learned to do blocks prior to US being integrated into anesthesiology. The problem is that no one seems to have a nerve stimulator now that everyone uses US. I could use RF generator but don’t have in my office.

How about DRG stim? Are many of you relying on root blocks to identify dermatomes and “predict” response?

 

[lobelsteve]

Pain and dense numbness sounds like anesthesia dolorosa. We used to teach SCS was not effective for this when I was a KOL.

 

[RoloTomassi]

The patient has pain and dense numbness in the distribution of LFCN. After the US guided block he still hand pain and dense numbness. The only indication I could have that block was on target was US. I like the stim Idea as that’s how I learned to do blocks prior to US being integrated into anesthesiology. The problem is that no one seems to have a nerve stimulator now that everyone uses US. I could use RF generator but don’t have in my office.

How about DRG stim? Are many of you relying on root blocks to identify dermatomes and “predict” response?

Do you have access to EMG machine?

 

[Orin]

The patient has pain and dense numbness in the distribution of LFCN. After the US guided block he still hand pain and dense numbness. The only indication I could have that block was on target was US. I like the stim Idea as that’s how I learned to do blocks prior to US being integrated into anesthesiology. The problem is that no one seems to have a nerve stimulator now that everyone uses US. I could use RF generator but don’t have in my office.

How about DRG stim? Are many of you relying on root blocks to identify dermatomes and “predict” response?

Stimrouter used to sell/give a Stimpod for doing stimulation, but BBraun also sells their old one for doing blocks. It's still 1 - 3k I think list price?

You could jerry rig a 25$ TENS unit for this purpose I suspect.

I have been doing some nerve root blocks before referring to a partner for DRG but it's hard without an RF generator with reusable probes to do stimulation to predict targets for DRG stim. In theory they could do it on the table, but it's such a pain to place them.