Alert Topic: Spinal Cord Stimulators

Heady times for spinal cord stimulation: Can it serve as treatment for migraines?

If research being led by Chicago’s Rush University Medical Center proves out, the estimated 2.8 million Americans whose migraine headaches do not respond to existing treatments or medications may one day soon be helped by implantation of a spinal cord stimulator.

The research – begun in 2006 and currently ongoing – is taking place at 15 sites across the U.S. and involves roughly 150 patients. The subjects have been implanted with a modified spinal cord stimulator placed at the rear of the base of the head so that the device can deliver electrical impulses to the occipital nerve.

The study goes by the name of PRISM – short for Precision Implantable Stimulator for Migraine. There is no word yet from researchers with regard to what they are finding.

Record of success

However, it would come as no surprise were the PRISM researchers to be seeing encouraging results, given the lengthy track record of success for spinal cord stimulators generally.

Studies dating back to the 1990s have demonstrated the efficacy of spinal cord stimulation in relieving select chronic pain disorders such as failed back syndrome, complex regional pain syndrome (Types I and II) and peripheral neuropathy. Newer indications for this treatment modality include cancer pain, abdominal pain, interstitial cystitis, phantom limb pain, diabetic neuropathy and postherpetic neuralgia. The January 2008 issue of The Review of Cardiovascular Medicine informs that spinal cord stimulation even shows effectiveness in the treatment of intractable angina pectoris.

According to a study published in the journal Pain Practice (March 2006), an implanted spinal cord stimulator helps most refractory neuropathic pain sufferers experience at least a 50% reduction in the level of pain, with minimal side effects. Moreover, many such patients who benefit from spinal cord stimulation are able to dramatically trim their consumption of analgesics, the journal indicated. Improved quality of life is reported by implant recipients and there are potential cost savings to the healthcare system, Pain Practice added.

An important point raised by this same Pain Practice article was that many physicians view spinal cord stimulator implantation as an intervention of last resort, when in fact they should esteem it in the exact opposite regard. “...[E]vidence suggests that early intervention with spinal cord stimulation results in greater efficacy and, in the case of failed back surgery syndrome, should be considered before reoperation,” the journal states.

Mechanisms not fully understood

Spinal cord stimulators – alternatively referred to as dorsal column stimulators – generate an electric impulse near the dorsal surface of the spinal cord to create paresthesia, thereby changing the patient’s perception of pain.

It is not fully understood how the effects of spinal cord stimulation are mediated, but one explanation floated in the November 2007 issue of European Journal of Pain holds that a complex set of interactions must occur at several levels of the nervous system and take in both spinal and supraspinal mechanisms. “Results suggest that spinal cord stimulation is able to influence neurobiological processes at the supraspinal level and that the clinical effects may be at least in part of cortical origin,” the journal offers.

Other research efforts have led scientists to speculate that the mechanism of action behind spinal cord stimulation involves a “closing of the gate” by the antidromic activation of large-diameter afferent fibers in either the brain stem or thalamocortical systems, which then produces both ascending and descending inhibition activation of anterior pretectal nucleus.

While the answer to the question of how and why it works remains elusive, what is known right now about spinal cord stimulation is that it works. For example, the February 2008 issue of The Journal of Neurosurgery divulges that 95% of complex regional pain syndrome Type I patients studied by the University of Maastricht in the Netherlands were well enough satisfied that they would have their spinal cord stimulator implanted again were it removed and a
choice given for some other intervention.

Three main parts

As for the device itself, a spinal cord stimulator consists of three main parts.

The first is the electrical pulse generator (which can come in the form of a radiofrequency receiver, depending on the manufacturer and model). The generator is implanted into either the abdomen or buttocks. The unit (except for the RF version) is powered by either a rechargeable or non-rechargeable battery. (The downside to the non-rechargeable option is the battery must be surgically replaced each time it runs out of power.)

The second part is a wiring harness. It contains electrical leads that connect to the generator and extend outward into the epidural space.

The final component is a hand-held controller that the patient operates to activate or deactivate the stimulator and to increase or decrease the amount of electric pulse traveling through the wire leads. Some device models are physician-programmable to allow for preset stimulation patterns customized to the patient’s individual requirements.

The implanted part of the spinal cord stimulator is introduced by a pain medicine specialist or other appropriately trained surgeon using either a percutaneous approach or surgical laminectomy (or laminotomy). In any event, the patient is kept awake so as to provide feedback about the paresthesia effect, which abets the process of deploying the electrical leads in the optimum locations.

Prior to the day of implantation, though, it is customary to conduct a trial with a temporary device to determine whether the patient is a suitable candidate for a permanent spinal cord stimulator. During the trial – which normally runs three to seven days – a percutaneous lead is connected to an external pulse generator. Patients are deemed appropriate candidates for a permanent device if they experience at least a 50% improvement in pain during the trial.

Conclusions

Spinal cord stimulation is an effective – albeit overlooked – treatment for severe chronic pain.
It is FDA-approved and has been utilized for more than 30 years, with over 100,000 patients currently experiencing pain relief because of it.

The modality is most closely associated with the treatment of back pain. However, as ongoing research may yet show, spinal cord stimulation technology could emerge as useful for resolving pain from head to toe.

Quite a few of the chronic-pain patients we see here at Oregon Pain Associates prove to be good candidates for implantation of a spinal cord stimulator. Our team has over the years successfully provided genuine life-changing relief for nearly all of these individuals – a reason among many why we have grown to become the area’s leading resource for treatment of chronic pain.

We’re here to help all your chronic pain patients and in particular those cases where achievement of desired good results has proven elusive.

Oregon Pain Associates can perform evaluations of your patients and make intervention recommendations or, at your request, initiate treatment and perform follow-up. Whichever path you choose, the team at Oregon Pain Associates will keep you apprised every step of the way. Satisfied by the high-quality services and interactions delivered at each encounter, your patients will return to you as willing as ever to continue entrusting you with their ongoing care.

For more information, please call Oregon Pain Associates in Portland or Salem at (503) 238-7246 or toll-free (866) 785-7246.

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