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blocking nerves |
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For close to 90 percent of cancer patients, and more than 75 percent of terminally ill cancer patients, nonprescription drugs or narcotics provide adequate relief from pain. However, for some patients, additional pain-relieving measures are needed, and often these require some type of surgery. They include nerve blocks, spinal cord stimulation, and other surgical and non-surgical medical procedures. Reasons that some patients may require more aggressive pain treatment include an inability to achieve adequate pain relief from drugs alone, or the development of intolerable side effects such as nausea, constipation, sedation and confusion. Anesthetic (eg. nitrous oxide, lidocaine, peripheral nervve blocks, and autonomic nerve blocks) and neurosurgical approaches (eg. cordotomy, dorsal root entry zone lesions, and rhizotomy) are most effective in treating patients with well-defined , localized pain. Other surgical interventions include removing the tumor from effected area(s) (ed. removal of spinal metastases), stabilization procedures for bone fractures (eg. spine, hip, and femur), and implantation of drug delivery devises (eg. epidural, intrathecal, and intraventricular.) Blocking Nerve Pathways When certain substances are injected into or around a nerve, that nerve is no longer able to transmit pain. A local anesthetic, which may be combined with cortisone, provides temporary pain relief. For longer lasting pain relief, phenol or alcohol can be injected. Loss of all feeling in the affected area is a frequent side effect of a nerve block. In rare cases, a nerve block may cause muscle paralysis. In certain types of nerve blocks called neurologic interventions, surgery can be performed to implant devices that deliver drugs or electrically stimulate the nerves. Sometimes, surgery may be done to destroy a nerve or nerves that are part of the pain pathway. To block these pathways, a neurosurgeon may cut a nerve close to the spinal cord (rhizotomy) or cut bundles of nerves in the spinal cord itself (cordotomy). However, when the nerves that transmit pain are destroyed, sensations like pressure and temperature can no longer be felt. Therefore, after these operations, patients are more likely to injure the affected area because they no longer have the protective reflexes of pain, pressure or temperature. Electrical Nerve Stimulation The use of electricity in pain control dates back thousand of years, to when electric eels and torpedo fish were applied to painful areas. Benjamin Franklin also experimented with electricity as an analgesic tool. Transcutaneous electric nerve stimulation (TENS) is a technique in which mild electric currents are applied to selected areas of the skin by a small power pack connected to two electrodes. The sensation is described as a buzzing, tingling, or tapping feeling. The small electric impulses seem to interfere with pain messages and they can be adjusted by the patient so that the sensation is mild yet effective. Furthermore, pain relief lasts beyond the time that the electric current is applied. TENS units can be purchased from medical supply outlets. Speak to your doctor or physical therapist about how to use this technique appropriately. Non-Surgical Interventions Local or whole-body radiation therapy may increase the effectiveness of pain medication and other noninvasive therapies by directly affecting the cause of the pain (e.g., by reducing tumor size). In addition, a single injection of a radioactive agent may relieve pain when cancer spreads extensively to the bones. Hormone therapy may also be used in treating pain for some cancers. For example, the Food and Drug administration recently approved the drug Viadur (leuprolide acetate implant) as an annual treatment for pain experienced by patients with advanced prostate cancer. The drug is given via an implant in the patient’s arm and can deliver up to a year’s worth of pain-relieving medication. Leuprolide is currently used for pain associated with advanced prostate cancer, but it is administered through frequent injections. The Viadur implant will not only deliver the drug automatically for a period of up to one year, but it would do so at a much more precise level. Recent Developments Researchers from Stanford University Medical School have developed a type of magnetic resonance imaging (MRI) to deliver regional anesthesia more accurately. In a presentation at the annual meeting of the American Society of Anesthesiologists, Dr. Sean Mackey said the new method enables a physician to observe the precise trajectory and depth of the needle and to monitor the exact distribution of the pain medication. The interventional MRI (iMRI) unit is designed like an open-magnet. It allows the physician and the radiologist to stand between the two magnet units, on either side of a patient. During clinical trials, they performed a number of nerve block surgeries. In all of the patients in the trial, conventional blocks had either failed or were deemed too risky due to the patients’ distorted anatomy from cancer or obesity. Mackey told the attendees that the procedure takes from 45 minutes to 2 ½ hours, but pain relief lasts for weeks to months. The iMRI procedure allowed them to target needles and catheters in places that were previously inaccessible, he added. A team of British researchers, writing in the Journal of Bone and Joint Surgery, concluded that many breast cancer patients do not receive pain-relieving surgery for tumors that have spread to the spine. In a study of 963 women with breast cancer, Dr. Charles Galasko and colleagues from the University of Manchester reported that 44 percent of the women had suffered bone pain at some point. In 51 women, the cancer had spread to the spine, yet only 6 had been referred for spinal surgery to alleviate their pain. Galasko noted that breast tumors are more likely than any other cancer to spread to and destabilize the spine. This instability, which can make simple movements agonizing, strikes about 5 percent of breast cancer patients. Surgical techniques to stabilize the spine and relieve compression of the vertebrae and nerves are available, yet often not utilized. Galasko reported that among 80 cancer patients they have treated for spinal instability, 89 percent had complete pain relief. However, he cautioned, women should only have spinal surgery after their bodies have had time to recover from their regular chemotherapy or radiation. SOURCES:
This page was last
edited on 05/07/2002 Written by Richard
Zmuda, senior writer, cancerpage.com
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