Claudio A. Feler, MD :I always begin device type selection by looking at the lead array that I think is necessary to treat the patient. This is partly a function of the physiology of the patient’s pain and partly a function of the topography that we’re trying to cover. So in my book, device selection always begins with lead selection.
Once the lead or leads have been selected for the array, that will determine to some extent what sort of generator we might end up using. If the patient needs to have 8 (eight) contacts there are all sorts of options available, but if they need 16 (sixteen), then there are less options available.
Subtle factors:
Timothy Deer, MD: Well I think several subtle factors come in. For example: What’s the patient’s weight? If the patient is extremely obese it may be hard to recharge the system because of the amount of tissue you have to go through. What about the patient’s skin texture, skin diseases that may impact rechargability or radio frequency? What about the patient’s intelligence level? Can they recharge their system appropriately? Can they wear a radio frequency device?
What about the cosmetics of it all? If they’re a fashion model they may want the smallest generator possible. And then lastly, are they willing to do what it takes to help their pain?
What’s the most important part of the process?
Dr. Deer: Well, I think it’s great that we have 3 (three) devices to choose from. I think the real important point though, is that the trial of stimulation still is the most important part of this whole process, because if we don’t take information from that process to pick our final generator, we’ll make mistakes. So I’m glad we have more choices. On the other hand, we need to use the trial information and match that to the type of generator we’re going to pick.
Who is best suited for a conventional IPG?
Robert M. Levy, MD, PhD : For a totally implantable conventional pulse generator, the ideal patient is the one who uses a relatively low rate, a relatively low amplitude, and in home, the requirements for input on their part is minimal. So, in our patients with marginal cognitive function, in our patients who just don’t want to mess with it, that device is the one that requires the least input on their part.
Who is best suited for a rechargeable IPG?
Dr. Deer: Well, I think in my practice the rechargeable patient would be someone who has a complicated pain problem that would lead us to use a complex array of programs. So for example, the patient who’s had a laminectomy, who has pain in their back, down their leg, or down both legs, and we don’t think we can achieve that with a simple low amplitude, simple array.
Who is best suited for an RF system?
Dr. Levy: Radio Frequency systems are required for patients who use very high currents, for patients who require very high frequency with their stimulation, and in patients who require multiple programs to be run in order to adequately cover their pain. That’s really not much choice because if the patient needs those things, the implantable devices that are programmable don’t allow us the ability to do that.
Who should not receive a rechargeable IPG?
Dr. Levy: A patient who has significant cognitive dysfunction is not a patient who you want to trust to recharge their battery, especially if you know you that if you don’t recharge the battery the device becomes useless.
Who should not receive a conventional IPG?
Dr. Deer: Where the trial with two quadripolar leads wouldn’t cover the pain pattern, where if one octapolar lead wouldn’t cover the pain pattern, they’re going to definitely fail conventional IPG’s over time. So the trial suggests that you need 16 (sixteen) contact points or surgical needs that may be more complicated, then you need either an RF system or rechargeable system, the conventional IPG will always fail.
The other side of that story is someone who needs high frequency. You can’t achieve that with a conventional IPG. And then lastly someone with high amplitude requirements, they’ll get re-operated on every year for several years in a row [to replace the battery]. And again that’s not very good cost effectiveness, it’s not good for patient care, and it’s not very good for patient satisfaction.
Who should not receive an RF system?
Dr. Levy: Patients who don’t have an appropriate support structure, who also have cognitive limitations probably shouldn’t have a radio frequency system because they just don’t have the wherewithal to maintain the system so that it gives them good relief.
What are the downsides of rechargeability?
Dr. Deer: Well, I think the downsides of rechargeability, number one is the cost. So, if you really feel the patient could get by with a conventional IPG, then you may not want to pass that cost on to the patient, the insurer and the hospital facility. Secondly will be the patients’ ability to recharge the system if they feel they can understand how to do that. Thirdly will be, are there any skin issues with rechargeability, adhesive irritation, skin irritation? And lastly, cosmetics.
What should an implanter know?
Dr. Feler: I think it’s important for the physician to try and educate themselves as best possible about the range of devices available in neuro-stimulation. Just because one company makes a device that is a conventional battery, and another company makes a device that’s a conventional battery, that doesn’t mean that they operate the same. It doesn’t mean that they have the same parameters of stimulation available and it doesn’t mean that they program the same. And so, essentially, they’re two different devices that are potentially going to have different applications and indications.
Similarly with rechargeables, there are many issues at hand that are important. Many of them have to do with the ease with which a patient will be able to interact with the device. These include recharge cycles, amount of time that it takes to totally recharge a unit, as well as the discharge cycle.
How often should a patient be expected to recharge the device?
Dr. Feler: Another issue is the duty cycle. In other words, how often should the patient be expected to have to recharge the device? This is going to be dependent on the power requirements and how many programs and cathodes the patient is using, as well as the frequency of stimulation. Obviously, the longer the duty cycle the better.
What are the safety issues?
Dr. Deer: Well, safety issues with rechargeability are important for several factors. One really is the medical legal environment. If someone has a skin injury from this device, we’ve learned from the McDonald’s experience (spilling hot coffee) that anything you ask, juries will award considerable sums of money for things that may actually be the fault of the person injured. So it’s really important that you can’t overcharge the system. If someone falls asleep with the recharger on, that they won’t get the heat up and injure the skin. That’s probably the most important thing I’ve seen so far in the industry with the new rechargeable systems, has been some of the device makers have had some problems with that issue.
Dr. Levy: Well, one of them I’ve already alluded to, and that is the potential for heating. That’s one of the things that really isn’t required by current battery technology. And as I’ve said, if you move the antenna outside of the case containing the rest of the electronics, one can recharge with little or no risk of heating or burning. But that’s a real safety issue, and that safety issue is such that I couldn’t recommend any pulse generator to a patient unless I was certain that there was not a risk of device heating or burning.
What if a patient has selected a device before the trial?
Dr. Levy: Well, this really isn’t a theoretical question. I face this all the time when patients come to me having done research on the internet or having read about the various devices. The important thing to do is to educate the patients. It’s important to let them know the things that I’ve just talked about. And for example, I had a patient come in last week who was absolutely convinced that she wanted a rechargeable unit, but when I discussed with her and her husband the current limitations of a rechargeable unit they absolutely refused it and didn’t want it. And they really were happier to have a conventional implanted pulse generator.
It’s also important in terms of the maintenance of patients with chronic pain for you to set limits as a pain care physician. And certainly there are decisions and input that is important from the patient, but it’s also important that they’re willing to benefit from and accept your expertise. And a patient who won’t do that suggests that there are other problems that might make their pain care more difficult.
