Treatment of Phantom Pain
Treatment of Phantom Pain
Phantom Limb Pain (PLP) is a serious condtion that causes the subject, usually an amputee, to feel painful sensations in the area where the limb originally was.
When a condtion or an accident occurs that causes a limb to be severed or have to be removed surgically, there is a good chance of phantom sensation and pain. What percentage of patients have sensation and/or pain? Reports of sensation are almost always part of an amputation. "It is widely accepted that over 90% of all parients have some sensation after surgery or accident" (Kamen, 1994).
But how about phantom pain? Accounts of phantom pain are vague and widespread. Why is that? There seems to be several reasons. "Because of the intangible, subjective sensation of PLP, the reports of incidence are widely scattered" (Kamen, 1994). A study done by Sherman et al. (1984) "finds that amputees are reluctant to divulge their complaints (of PLP) for fear of being labelled insane" (Sherman, 1980). So what is the percentage of patients suffering PLP? That has never been very well determined. "Incidence of phantom pain is inconsistently spread between 0.5-13%, 30-75%, and 75-97% with the greatest number of surveys reporting an incidence between 30-75%" (Kamen, 1994). And, "Reports on the incidence of phantom pain range from one to fifty percent" (Feinstein, 1954). Obviously, this is a very wide range.
Several different factors affect the perception of PLP. Melzack, created a paradigm called the neuromatrix theory of PLP that gives an account of phantom pain.
Brain Elements in PLP
There are many different strategies for dealing with phantom pain. "In 1980, Sherman showed that there were over 60 different treatment methods for phantom pain" (Feinstein, 1954). This shows the very subjective and varying kinds of PLP. Among the effective drugs have been ß-blockers, central nervous system serotonin agonists, the tricyclic antidepressants, and calcitonin (a polypeptide hormone) (Kamen, 1994). It seems that elevated serotonin: 5-HT, a monoamine neurotransmitter, excite the inhibitory pathways thereby lessening pain. The key note is to remember that different drugs are more and less effective for dofferent people. So, a drug that is very effective for most patients may not have any effect on a particular one.
Although drugs are the first line of defense for alleviating phantom limb pain, recent research shows that perioperative and postoperative anesthetics may be more effective. (Gross, 1982). Pre and postoperative local anasthetics have been shown to block "pain sensation and spinal cord hyperexcitability associated with nocioception" (Gross, 1982). Gross injected a local anasthetic into the contralateral limb reduced pain in all four patients. Only one of the patients had had any more PLP at six months and two years. It is not currently known in contralateral treatment acts through a neuromatrix model or a placebo mechanism, as Gross says "further study is required".
Several forms of physical therapy have been tried. (Anderson, 1958) tried ultrasound, and other treatments such as vibration and electrical nerve stimulation have been tried. While some patients have felt relief, even total in a few cases, this has not proven to be a vary effective treatment route.
Neurosurgical treatments have been tried to relieve PLP with a very low success rate. It is important to note however, that only the most serious cases get to this point. The classical surgeries have been "to cut nerves above the neuromas (nodules that form when connections are cut and cannot be reestablished), cut the dorsal roots that bring the information in, or to make lesions in somatosensory pathways in the spinal cord, thalamus, or cerebral cortex" (Carlson, 1994). But as Melzack reports, "these treatments may work a while, but the pain often returns" (Melzack, 1992). The newest methods have been to implant of a spinal cord stimulator. This is the dorsal column stimulation procedure "in which electrodes are implanted surgically in the spinal cord...used after the report of the gate-control theory presented by Melzack and Wall" (Kamen, 1994).
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