Dr. Attaman is fellowship trained and board certified in Interventional Pain Managemement, and is residency trained and board certified in Physical Medicine and Rehabilitation. Dr. Attaman was interviewed by Violet Matthews, BSN, RN, Secretary of Health Organization for Pudendal Education.
Violet: Please describe the procedure for neuromodulation.
Dr. Attaman: First I’d like to discuss why we need neuromodulatory procedures in the first place.
There is an interesting physiologic response known as “wind-up phenomenon.” This occurs in nervous tissue such as peripheral nerves (the pudendal nerve is an example), nerve roots, the spinal cord, and the brain. The closer to the brain, the more powerful wind up phenomenon becomes. We have found through research that as pain becomes chronic such nervous tissues actually become more efficient at perceiving and processing pain rather than becoming tolerant to said pain. In other words, the body becomes better at feeling it more often, and with more severity!
In fact, the nervous tissues may become so “wound up” that they generate pain signals even when the offending “pain generator” is eliminated. For example, a person who has had a knee replacement may continue to experience their pre-operative knee pain for many months after the surgery. The knee is gone, but the pain remains.
Not only that, but the portion of the brain that is dedicated to the painful area becomes physically more dedicated to this pain. This obviously sounds counterintuitive. Wind up phenomenon is thus a maladaptive evolutionary trait.
Neuromodulation is a branch of Interventional Pain Management. The goal of neuromodulation is to counteract wind-up phenomenon, and help these sensitized nerves function normally. We may even be able to help these nerves heal. There are many methods of neuromodulation, but in this article we will discuss spinal cord stimulation. Another powerful method of neuromodulation is pulsed radiofrequency treatment which will not be discussed here.
Spinal cord stimulation or SCS (aka Dorsal Column Stimulation or DCS) is a procedure in which 1-3 thin wires with electrodes at the end are placed on top of certain parts of the spinal cord via a needle under x-ray guidance. These wires are called “leads.” These leads are then plugged into a small device very similar to a pacemaker. This device is called the SCS generator. The generator creates very small electrical signals which are transmitted through the leads to the spinal cord. These signals act to change – or neuromodulate - the way chronic pain signals are transmitted to the brain, and thereby help to reduce or eliminate chronic pain. The SCS system does not eliminate acute pains such as injuries, but only helps reduce or eliminate chronic pain signals.
If a patient elects to try a SCS system for their pain, the process occurs in two phases. Phase one is known as the SCS trial phase. During this time, the leads are placed through the skin with needles during a procedure that lasts roughly one hour. The wires then exit the skin, are secured with special adhesives, and are plugged into a SCS generator worn on a belt. The patient returns home and lives with this SCS system for 5-7 days to see if there is sufficient pain relief. During this time, the patient is encouraged to do normally painful activities to see if the SCS system is efficacious at stopping the pain.
The patient then returns to the physician’s office at day 5-7 and the leads are removed easily. The adhesive is removed and leads gently slide out of the spine and skin. It is generally completely painless and safe.
The results of the 5-7 day trial are then discussed with the physician. If the patient reports very significant pain relief during the SCS trial, then a decision to move onto phase two may be made. Phase two is known as SCS implantation. During this phase, the patient undergoes a rather minor surgical procedure during which two 1” incisions are typically made in the skin, and both the generator and the leads are placed completely inside the body and spinal canal. This surgery typically takes 1-2 hours and the patient then goes home. From this point on the SCS system is permanently implanted in the patient, is waterproof, controlled by a remote control, and recharged through the skin via radio waves.
The typical SCS generator lasts 5-7 years after which time it must be replaced during a very short surgery during which a 1” incision is made.
Violet: How do you determine if a patient is a good candidate for neurostimulation and whether to use stimulation at the conus medullaris or at S2-S4?
Dr. Attaman: I offer SCS trials under two situations:
1. All conservative measures such as PT, medications, and injections have failed and my patient is not a good candidate for pudendal surgery.
2. My patient has had pudendal surgery with no pain relief or worsening symptoms.
If my patient has reached that point, only then will we discuss SCS trial as an option.
The conus medullaris (http://en.wikipedia.org/wiki/Conus_medullaris) is a special area of the spinal cord which can be targeted during a SCS trial to help with pelvic pain, in particular the pain of pudendal neuralgia.
The S2-S4 roots are spinal nerves that exit the sacrum and merge together to form the pudendal nerve. A SCS lead can be placed directly onto one of these nerves to neuromodulate the pudendal nerve.
In 2009, a German case report article emerged describing SCS stimulation at the conus medullaris as a treatment for pudendal neuralgia1. To my knowledge, this was the first description of conus stimulation for pudendal neuralgia.
This was then followed by a 2012 case report of successful treatment of refractory pudendal neuralgia from conus medullaris stimulat2.
Then a 2015 study appeared from Nantes, France3. Nantes is considered the epicenter of pudendal neuralgia diagnosis and treatment. This paper studied 27 patients who did not improve after pudendal nerve surgery who then underwent SCS trial. Twenty of the 27 patients were considered to be responders to spinal cord stimulation and 100% of implanted patients remained long-term responders (mean tripling of sitting time, and mean estimated percent improvement of 55.5%).
During my earlier SCS trials for pudendal neuralgia, I placed two leads over the conus medullaris and one lead over each of the S2 nerve roots simultaneously. My patients would thus have four SCS leads running during the trial. My patients would have the ability to use any combination of these four leads during the trial to give them pain relief.
I found that the vast majority of patients rarely used the sacral nerve root leads and much preferred stimulation over the conus medullaris. Therefore I now initially trial over the conus medullaris solely. If that fails, we can repeat a trial with leads over the S2 or S3 roots.
I also have seen a great many patients who have had SCS leads placed over the S2 or S3 roots under the care of other physicians with little benefit. Oftentimes my patient was misdiagnosed with interstitial cystitis for which sacral nerve root stimulation was offered. Failure of sacral nerve root stimulation was further information influencing me to choose the conus medullaris as a primary target.
I am convinced at this point that the conus medullaris is the optimal target for neuromodulation in cases of pudendal neuralgia. Perhaps a better target will emerge in the future.
Violet: In your experience, what expectations should a patient going into the neurostimulation procedure have, as far as achieving pain relief?
Dr. Attaman: I honestly don’t want my patient to have any expectations regarding pain relief! As we start with a SCS trial, I want them to be very open with both themselves and me about what type of pain relief they are getting. I am very honest with them prior to the SCS trial and tell my patients that their pain relief may range between 0 and 100% during the trial. I do not want to influence their pain relief reports in any way, as we are considering surgically implanting a medical device in them if all goes well. Neither the patient nor myself wants to implant a SCS system unless it truly gave outstanding pain relief during the SCS trial phase.
Violet: What risks or complications should a patient be aware of when undergoing a neurostimulation procedure?
Dr. Attaman: The risks are statistically very few and generally very minor. They include bleeding, infection, no effect at all, worsening pain, nerve damage, paralysis, stroke, death. Case reports of severe complications are exceedingly rare and statistically SCS is typically safer than most medications used for pain.
Violet: What are your thoughts on pudendal nerve release surgery for patients with pudendal neuralgia vs. neuromodulation without surgery first, and do you consider neuromodulation a long-term solution or does it eventually lose its effectiveness?
Dr. Attaman: This is a good question. Let us assume in this case that all conservative measures such as PT, medications, injections have failed. In my opinion, if a clear structural cause of pudendal neuralgia can be identified, and an experienced surgeon feels there is an excellent prognosis of pain relief from surgery, that is probably the best option. If there is no structural cause that can be surgically corrected, or if the likelihood of pain relief from surgery is poor to moderate, neuromodulation may be the better option.
SCS systems can be removed. The risk is very low. A patient in which an SCS trial fails can have it removed with low chances of any worsening symptoms.
Pudendal surgery is irreversible. The risk is moderate. While the chances of worsening symptoms are low, if pudendal symptoms worsen post-operatively it is usually very difficult to overcome, though SCS can be efficacious3.
Violet: Do you know of any reliable way to determine whether a patient with pain in the distribution area of the pudendal nerve has pudendal neuralgia stemming from the peripheral pudendal nerve as opposed to a spinal radiculopathy?
Dr. Attaman: Great question! Pudendal neuralgia is generally a diagnosis of exclusion.
Spinal radiculopathy will usually have imaging abnormalities on MRI. Radiculopathy is exceedingly rare in the S2-S5 nerve roots. Typical causes are Tarlov’s cysts, fracture, tumor. S2-S5 radiculopathic pain will be incompletely relieved from image-guided pudendal nerve blocks, but completely relieved from selective nerve root blocks. Sensory abnormalities are more common with sacral nerve root pathology as well.
Pudendal neuralgia is diagnosed by image guided pudendal nerve blocks. I generally do two on each affected side with a different local anesthetic each time to rule out false negatives and false positives. For one block I will use a short acting local anesthetic such as Lidocaine which typically lasts 2-4 hours. For the other I will use a long acting local anesthetic such as Bupivicaine or Ropivicaine which typically last 6-12 hours. I do not tell my patient which specific local anesthetic I am using unless they request this information. If I find >80% pain relief after each block, and the pain relief duration is concordant with the expected duration of the local anesthetic used, then I feel confident making the diagnosis of pudendal neuralgia.
MRI neurography may also be used to help rule in pudendal neuralgia. If entrapment or inflammation can clearly be seen, that helps point toward pudendal neuralgia as the problem. However, the presence of MRI neurogram abnormalities alone does not render the diagnosis of pudendal neuralgia. A pudendal nerve may be entrapped or inflamed, yet not be producing any pain at all. That is why pudendal nerve block is so critical.
Finally, pudendal nerve conduction studies can be done. However they are rarely performed and generally done so only at tertiary academic centers.
1. Reichart R, Kuhn SA, Vogel L, et al. Spinal cord stimulation at the level of the conus medullaris: Treatment option for therapy-resistant postoperative neuralgia of the pudendal nerve. Schmerz 2009;23:640–644.
2. Rigoard P, Delmotte A, Moles A, et al. Successful treatment of pudendal neuralgia with tricolumn spinal cord stimulation: Case report. Neurosurgery 2012;71:757–763.
3. Buffenoir, K., Rioult, B., Hamel, O., Labat, J.-J., Riant, T. and Robert, R. (2015), Spinal cord stimulation of the conus medullaris for refractory pudendal neuralgia: A prospective study of 27 consecutive cases. Neurourol. Urodyn., 34: 177–182. doi: 10.1002/nau.22525