Underprotective and overactive pain perception:

Its problems and possible solutions

by Christina Willis

Pain is probably one of the most universal perceptions thathumans, or indeed any animal, can experience. From stress headachesto stubbing one's toe, we come into contact with pain on a dailybasis. This is normal data about the experience of pain. However,there are several groups of people that do not feel pain in a commonway. Either they don't feel enough pain to tell them that somethingis wrong, as in the cases of lepers and some diabetics, or they havetoo much pain, as in the cases of some diabetics, people with phantomlimb pain, cancer victims, stroke victims, and other diseases of thebrain or spinal cord (Casey, 1996).

The effects of pain on these people is in many cases debilitating;their normal lives are likely gone or, at best, on hiatus. Thesereasons are incentive enough for scientists trying to discover moreways to eradicate wanton pain (or the absence of pain) because thereis a threat that many of us, at some point, will be subject to thesesame problems.

The first case of underprotective pain perception that will bediscussed is that of leprosy. Leprosy is a bacterial pathogen (M.leprae) that attacks the peripherial nervous system in humans and isthe leading cause of peripheral nerve disease in the world. Thebacteria attack the Scwann cells that form the myelin sheath aroundnerve fibers. Without the protection and insulation of the myelinsheath, nerve cells fire inefficiently. The net results of thisbacterial infection are skin lesions and damage to the nerves, mainlyin the extremities and facial area (Henderson, 1998) .

The result of the nerve damage that is pertinant to this topic isthe loss of sensation. This lack of feeling complicates normalliving: the person with leprosy is not able to identify cuts or burnson his or her skin. Without the protection of normal pain responses,this person could conceivably fail to notice for quite some time thathe has been injured and therefore not take further consciousprotective measures such as cleaning the cut with alcohol or treatingthe burn with salve. The effects of this lack of protective sensationare grim: lesions and eventual deformities result from the lack ofcare given to the body. Although luckily the bacteria can be killedwith a month-long course of several drugs, unfortunately the nervedamage is permanent (Henderson, 1998). This means that the personwith leprosy will remain feeling a lack of sensation fo the rest ofhis life, and constant vigilance may be necessary to preventinfections and complications from something as small as a papercut.

The next people subject to the phenomena of an underprotectivepain mechanism are diabetics. Diabetes, aside from the primaryproblem of blood sugars as the result of renal failure, offers a hostof complications ranging from diabetic retinopathy to diabeticneuropathy. The causes of peripheral neuropathy suffered by diabeticsis not yet known but is characterized by pain in the legs and toesand, paradoxically, the loss of sensation in those same places(Lavery, Armstrong, Vela, Quebedeaux, & Heischlt, 1998). Thegeneral pain felt in the legs will be discussed along with overactivepain; the loss of sensation is of primary importance here.

The loss of sensation due to peripheral neuropathy manifestsitself in a way similar to that of a person with leprosy; lowerextremities are subject to foot ulceration and foot deformities.Ulcers on the foot are adequate avenues for infections, and whencoupled with a high incidence of poor wound healing, can lead to evengreater problems, namely lower extremity amputation. Foot ulcers,along with foot deformities and abnormal pressures resulting fromdiabetes are all major risk factors for amputation. There is alsosome evidence that the impaired visual acuity of the diabetic as aresult of diabetic retinopathy could also be a factor in theincidence of foot ulcerations (Lavery et al, 1998).

On a practical level, the diabetic is subject to many problems.They must be vigilant about foot care which can be compromised byvision problems, all a result of their condition. The lack of aprotective pain perception in these people can lead to amputations,which in turn reveals a new set of problems discussed later to whichamputees are subject. In addition to this lack of protective painperception in diabetics is the opposite side of diabetic neuropathy:neuropathy that manifests itself as unlocalized chronic pain(Tesfaye, Watt, Benbow, Pang, Miles, & MacFarlane, 1996). Thismay seem to be a paradox. However, nearly every patient who haschronic pain has difficulty detecting protective pain in that samearea (Casey, 1996).

Pain associated with peripheral neuropathy is charaterized bylower extremity pain, night-time exacerbation of the problem, andextreme sensitivity to bedclothes leading to loss of sleep. The painfrom this condition can be disabling and is chronic. Unfortunately,conventional methods of pain management for this condition isdifficult; the drugs often don't work or they produce too many sideeffects and complications to be efficacious Tesfaye, et al,1996).

Another type of pain occurring from a pathological painperception, is that of the phenomena of phantom limb pain, acondition in which an amputee not only feels the prescence of themissing limb, but she experiences pain in it as well. Recent findingssuggest that phantom limb pain is not a result of grief for themissing limb as was once assumed. (Fisher & Hanspal, 1998).Research continues to determine the source of this phenomena.

Finding a way to manage these diverse types of pain is representedby a large volume of research and is the subject of its own journal,Pain. There are several different tracks research has taken, fromstudying how electricity effects nerves to techniques that are newaltogether.

A technique recently researched to help treat painful peripheralneuropathy associated with diabetes is called electrical spinal-cordstimulation (ESCS). This involves placing a stimulator with a lead onthe dorsal side of the spinal cord. The lead is then connected to anoutside stimulator. The patient controlled the frequency ofstimulation from 5 Hz to 1400 Hz and the intensity from 0 V to 10 V.Patients were instructed to adjust the frequency and amplitude of theimpulses as they saw fit. Since all pain relieving drugs were haltedfor the study, the electrical current was the only means for reducingpain. The findings demonstrated that ESCS is an effective painmanagement technique for diabetics with peripheral neurpathy. ESCS isalso effective for treating other people with Chronic Pain Syndrome,associated with patients suffering from stroke, multiple sclerosis,trauma, and other spinal cord disorders (Tesfaye et al 1996; Casey,1996).

Further study on the neural level has been conducted in relationto a substance Substnce P (SP), which is released in the spinal cordas a response to painful stimuli. Receptor sites for SP were not justblocked, as in older studies, but killed altogether by theexperimenters in this experiment performed on rats. This seemed tohave a positive effect, however, future studies involving humans maybe difficult; the conseqeunces of the permanent removal of SPreceptor sites is uncertain (Mantyh, Rogers, Honore, Allen, Ghilardi,Li, Daughters, Lappi, Wiley, & Simone, 1997).

Another method of pain management which has been in use for 2,500years in China and is just now beginning to gain acceptance in theWest is acupunture. Based on the principle that there are patterns ofenergy flow that are disrupted by disease, acupuncture utisizes theinsertion of fine needles to correct the imbalances of flow. A morescientifc explanation has been offered by Goldstein (1999). Theneedles are inserted and produce the analgesic effect because of thegate control theory, a system of excitatory and inhibitory cells that"open" or "close" the pain gate. The needles may activate the cellsthat inhibit pain. However, the real nature of acupunture is stillunknown. There is much debate about it amongst the medical communityin the United States. One camp tentatively believes in its uses, andthe other thinks that it is the result of suggestion and couldtherefore be dangerous. Whteher or not this is the case, there stillremains the problems of deciding when to use acupuncture, how totrain for it, and how to certify the trainees (Marwick, 1997).

A more psychological approach to the problem of controlling painis the (approved) use of nondirective suggestions. Imbedded in aneutral text, the suggestions in an experiment were introduced inorder to influence pain tolerance, pain threshold, and pain intensityperception. The subjects in the experiment listend to a 20-minutetape on pain theory in which the statements that pain control waseasy and that one should recall the effects of analgesic drugs weremade. Pain tolerance and thresholds were measured. The group thatreceived the suggestions had significantly prolonged pain tolerance,according to the results. The discussion section put forth the theorythat this method of pain management may be effective for shortlasting medical procedures but that relxation and imagery might bemore efficacious for long-term amd chronic pain. Hypnosis and otherforms of altered consciousness are also cited as possibly haviing aneffect on pain threshholds, as well (Neumann, Kugler, Seelbach, &Kruskemper, 1997).

In the same line of work is a study about mood and pain tolerance(Weisenberg, Raz, & Hener, 1998). A desired mood is induced bymeans of subjects watching a either a humorous, holocaust, or neutralfilm in 15, 30, or 45 minute lengths. The results concluded that nomatter which subject was presented, the longer movies had more effectthan the shorter length film. Although the effects of watching themovies took about 30 minutes to manifest physiologically, thesubjects then performed with greater pain tolerance than the originalbaseline. This method ties in with the above non-directive suggestiontecnique. It follows, then, that this method of pain management maynot be too helpful in long-term or chronic patients, but good forshor-term procedures.

Further research is being done on gene transfer and theimplantation of genetically engineered cells, as well as subtancesknown as noci-toxins (Caudle, 1997). With the increased availabilityof something as efficacious as ESCS and the other treatmentsdescribed here, chronic pain caused by diabetic neuropathy, chronicpain syndrome, and other disorders may well begin to be seen as atreatable conditions and not and certain doom of pain and sleeplessnights. The harder reserachers work to find answers now, the bettercare can be taken of these unfortunate people in the future.


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