Two new methods to manage chronic pain take advantage of the fact that pain only seems to be felt at the point of injury. Actually, pain messages are sent up the spinal cord to the brain, where the pain sensation is experienced. So blocking pain impulses from reaching the brain can prevent pain from being perceived, and thats the idea behind spinal cord stimulation therapy and intrathecal pain therapy. Both can be used when less invasive therapies have failed to provide pain relief.
Spinal cord stimulation therapy delivers low-voltage stimulation to the spinal cord to inhibit or block the sensation of pain. The patient often feels a tingling or vibration that is not unpleasant - the patient, in effect, trades one sensation for another. With spinal cord stimulation, leads are placed near the spinal cord and connected to an implantable or an external power source. Spinal cord stimulation therapy differs from transcutaneous electrical nerve stimulation in that TENS has no implantable components and acts only in the periphery.
Patients being evaluated for spinal cord stimulation therapy participate in a screening trial using local anesthesia to evaluate their response to electrical stimulation. A stimulating electrode is placed in the appropriate position in the epidural space over the nerves corresponding to the painful area. The lead is connected to an external power source during the trial screening period of several days. If the patient experiences adequate pain relief, the leads are placed in the epidural space by percutaneous placement or laminectomy. A subcutaneous tunnel is created to connect the lead to the generator and receiver pocket site. A subcutaneous pocket is created for implantation of the neurostimulator. Complications of spinal cord stimulation therapy include lead migration, hardware malfunction, or undesirable sensations described by patients as a jolt or shock. Batteries for a spinal cord stimulation system last about five years, and follow-up involves periodic assessments and adjustment of the effectiveness of treatment.
Intrathecal pain therapy delivers morphine directly into the intrathecal space of the patients spinal cord, where the drug binds to pain receptors, inhibiting the release of substance P, a neurotransmitter involved in the transmission of pain signals. Because morphine is delivered directly into the spinal cord, a fraction of the dose needed for oral or intravenous administration is given. For example, an intrathecal dose of morphine sulfate is approximately one-three hundredths of an oral equivalent dose. During trial screening, small doses of morphine are given through a bolus dose or continuous infusion into the epidural or intrathecal space. If the trial produces adequate pain relief, the catheter is placed intrathecally and connected to a surgically implanted programmable pump that releases prescribed amounts of morphine. The pump is refilled by inserting a needle through the skin into a filling port at the center of the pump. For most patients, refills are needed between one and three months, depending on dosage requirements. The programmable pump allows dosage adjustments to be made noninvasively using an external programmer. Batteries for the infusion system last three to four years. Complications and side effects of intrathecal pain therapy may be surgical, mechanical, or pharmacological. The surgical procedure to implant the device can cause bleeding, infection, and leakage of cerebrospinal fluid, although such complications are rare. Mechanical complications may involve the catheter and the pump. The most common complications are kinking, occlusion, or dislodgment of the catheter. Side effects of morphine include: constipation, pruritis, urinary retention, nausea, vomiting, and decreased libido.
In general, spinal cord stimulation therapy is indicated for neuropathic pain and unilateral or bilateral extremity pain. Intrathecal pain therapy is most often indicated for patients whose pain is nociceptive, in multiple or axial sites (located on the bodys head-to-toe axis), or changeable in pattern and for patients with neuropathic pain who have failed to respond to a trial with stimulation therapy.
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The above information is from:
] Chronic Pain: Stopping a Downward Spiral