The International Spine Centre

12 Walter Street, North Adelaide South Australia 5006
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Neuromodulation for Spinal Pain

Spinal pain is, in the vast majority of patients, caused by degeneration (“wear and tear”) of the joints connecting the small bones of the spine (vertebrae) without any significant secondary involvement of the nerves and/or the spinal cord. In most cases therefore, the actual cause of the pain is completely benign and the real problem is the pain itself rather than the anatomical structures that may be causing it. It makes sense therefore, to target the pain rather than attempting with an operation to interfere with the anatomical structures that may be triggering it, especially when there is doubt which area of the spine may be causing the symptoms, thus making the possible operation not only risky but also unreliable, unless the pain is clearly and directly linked to a nerve. Over the last thirty years significant progress has been made in the use of neuromodulation to relieve chronic pain. Neuromodulation works by interfering with the transmission of pain from the spine to the brain through the use of electrical currents. The electricity can be delivered either superficially via pads applied onto the skin (TENS – transcutaneous electric nerve stimulation) and/or with surgically implanted electrodes (“paddles” and “leads”) which are connected to a battery/pacemaker similar to the one used for heart problems (cardiac pacemaker). The stimulation delivered by the battery can either be felt like a tingling sensation in the area where the patient would usually feel his or her pain or can be programmed not to be felt at all (“silent”). Neuromodulation for spinal pain can be considered successful if at least 50% reduction of the patient pain is achieved following the implantation of the neurostimulator. This should result not only in increased mobility and function but also in a substantial decrease in the patient’s need for pain medications. Having recently reviewed the first 100 patients treated by me with neuromodulation with a minimum 12 month follow-up, more than three quarters of them (approximately 80%) have reported to have experienced at least 50% relief of their original pain.

The best candidates for neuromodulation are individuals suffering from chronic and debilitating spinal pain which is unlikely to respond favourably to formal surgical intervention. The reason for the low likelihood of operative treatment proving effective for these patients may be the presence of very extensive degeneration at multiple levels without significant compression of the nerves or that they may have already undergone repeat surgery with an unfavourable outcome and/or if general state of health may make a formal spinal operation too dangerous. Over the last few years I have become increasingly impressed by the favourable results of neuromodulation for spinal pain and therefore I am now offering neuromodulation to some of my patients as an alternative to formal surgery due to the potential advantages of a less invasive procedure, quicker recovery and similar outcome in terms of pain relief. Nevertheless in individuals suffering from significant spinal pain due to proven neural compression, if feasible formal spinal surgery is likely to lead to more substantial and reliable pain relief. This is also true for individuals in good state of general health with debilitating spinal pain if their pre-operative films show significant instability at one or two spinal motion segments.

There are two ways in which the electrodes (“leads”) for the neurostimulator can be inserted into the patient, either directly onto the posterior aspect of the spinal cord (“surgical paddle”) or underneath the skin (“transcutaneous leads”). The insertion of the surgical paddle is performed by a Spinal Surgeon and involves a small vertical skin cut, generally below the shoulder blades, to allow direct exposure of the spinal cord (laminotomy) and being able to insert the paddle with multiple electrodes into the epidural space in direct contact with the cord. The main advantage of this approach is that, when compared to the percutaneously inserted electrodes, there is a much lower chance of the electrodes moving, therefore making their position more stable and precise and also achieving a much wider contact area between the electrodes and the cord, likely to lead to more effective and reliable neurostimulation. The other approach for insertion of electrodes, in fact, generally adopted by Pain Specialists unable to carry out a formal laminotomy, involves smaller wire-like electrodes implanted through a needle and using an X-Ray machine to check their position. The percutaneously inserted electrodes, being much thinner than the surgical paddle, can move more easily and therefore are much more likely to migrate away from the chosen area, therefore reducing their reliability and effectiveness. The percutaneous approach for insertion has the advantage of being less invasive and carrying a lower risk of infection. This is a greater problem if a trial of stimulation is carried out due to the need for externalisation of the leads to allow the electrodes to be connected with an outside pacemaker/battery. Currently in the United States of America most Health Insurance Companies force the Doctors to do at least one week of trial before approving definitive implantation of the neurostimulator. In Australia however, at least until now, our Health funds allow us to proceed with definitive implantation of the electrodes and the battery at the same time, therefore decreasing significantly the risk of an infection. In any case, I believe that one or even two weeks of stimulation are not enough to allow the patient to meaningfully assess the potential efficacy of the neurostimulator. Most patients considered for this type of treatment, in fact, have been suffering from debilitating pain for a number of years and may have undergone already multiple operations and rely on large doses of strong pain medications. It is therefore unlikely that they may be able to come to any meaningful conclusion on the effectiveness or otherwise of the treatment after only a few days. My preferred approach therefore, when direct stimulation of the dorsal cord may represent the best option such as in patients with debilitating spinal pain, is to proceed with definitive implantation of the surgical paddle and battery in one stage. This operation is done under either neuroleptic intravenous sedation (“twilight anaesthetic”) or general anaesthesia and most patients may be able to be discharged within a few hours of undergoing the procedure even if I encourage my patients to stay in Hospital overnight. All patients should be able to ambulate immediately after the procedure. The surgery, in fact, should not be particularly painful even if it is normal to feel post-surgical pain at the site of the insertion of the paddle for the electrodes in the lower thoracic area if dealing with lower back and leg pain and/or in the neck if treating upper back, neck and shoulder and arm pain. In some cases the patient may experience also abdominal pain due to irritation of the thoracic cord but which should settle within a few days. The modern neurostimulators allow an increasingly diverse number of programs for neuromodulation with different characteristics of stimulation and which has led to better and better results. The general risk of complications from neuromodulation surgery is lower than conventional spinal surgery even if there is still a moderate chance of infection due to the presence of an implant and also a minor risk of neurological complications if, as a result of either an infection or bleeding around the electrodes, pressure may develop onto the nerves or the spinal cord. One significant advantage of this approach over conventional spinal surgery is that it is reversible and if it is established, after some time, that the treatment is ineffective, the implants can be relatively easily removed. A modern neurostimulator allows the connection of up to four separate leads. In most cases, though, a single paddle with multiple electrodes and two leads is used with the leads from the paddle connected to a battery positioned either into one of the buttocks and/or in the abdomen depending on the patient’s preference.

Having a neuromodulation system implanted requires a surgical procedure and should be carefully considered. The ideal candidate for neuromodulation is someone suffering from debilitating spinal pain when formal surgery is unlikely to be effective or may be too dangerous. If a patient is considered suitable I recommend that he or she spends sometime, before finalising his or her decision, discussing this approach and the relevant required hardware with one of the Technical Specialists in charge of monitoring patients treated by neuromodulation. This allows the patient to become familiar with the different types of implants and with the way the neuro-stimulation can be controlled and modified.

The leads are implanted indefinitely and may need to be replaced only if damaged and/or displaced. The lifetime of the battery varies depending on the Manufacturer and type. There are two types of batteries, one that the patient recharges through the skin with a charging device and another one which does not require recharging. The choice of battery is something that the patient should discuss with the Surgeon and the Technician before the operation. However, in general terms, non-rechargeable batteries tend to offer fewer stimulation options and therefore, in most patients a rechargeable battery is chosen.

Neuromodulation for spinal pain can represent a highly effective means of controlling debilitating symptoms where formal surgical treatment is unlikely to be effective or may be too dangerous.

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