Relief of pain by transcutaneous stimulation JOHN D. LOESER~M.D., RICHARD G. BLACK,M.D., AND AMALIA CHRISTMAN,R.N.

Department of Neurological Surgery, Department of A nesthesiology and Anesthesia Research Center, and Pain Clinic, University of Washington School of Medicine, Seattle, Washington ~" A series of 198 patients with chronic pain of diverse etiology was carefully analyzed for epidemiologic and descriptive factors which might influence the response to transcutaneous stimulation. The overall series included 121/2% with long-term success, and 68% with partial or short-term relief. There were no consistent specific diagnoses, or epidemiologic or descriptive factors that made good results from stimulation predictable. Stimulation of the painful area itself was not always necessary for pain relief. Favorable responses to transcutaneous stimulation were usually correlated with the continued existence of significant sensory input from the painful region. The authors conclude that transcutaneous stimulation is a valuable therapeutic modality for some patients with chronic pain. KEY WoRDs

p

9 transcutaneous stimulation

UVSIC~ANSwho attempt to manage the vexing problems of patients with chronic, intractable pain are often forced to recognize the inadequacy of most therapeutic measures. The patient with chronic pain has already tried a variety of drugs, as well as physical, surgical, and psychiatric therapies. These measures also have potentially disabling planned results or complications. Therapies advised by physicians have often added to, rather than reduced, the disabilities of these patients. Thus the evaluation of a particular form of therapy should include an assessment of the potential hazards as well as the chances of success. The most significant fact about transcutaneous stimulation for the relief of chronic pain is that no patient, to our knowledge, has suffered any 308

9 pain relief

complication related to its use. We are reporting our long-term experience (at least 1 year follow-up) because we have concluded that this therapy is valuable. Clinical Material and Methods

This study was carried out during 1973 on 198 consecutive patients referred to the University of Washington teaching hospitals or outpatient clinics because of chronic pain. After an initial medical evaluation all of the patients were treated by one of the authors using a stimulator and electrodes.* Patients were told that the stimulator delivered an *Stimulator and electrodes manufactured by Stimtech Corporation, 4001 Stinson Boulevard, Suite 224, Minneapolis, Minnesota 55421.

J. Neurosurg. / Volume 42 / March, 1975

Relief of pain by t r a n s c u t a n e o u s

stimulation

electrical stimulus to the skin and that its purpose was to alleviate their pain. No attempt was made to advertise the efficacy of this form of therapy. Patients were told that the technique was new, without known hazard, and sometimes yielded excellent pain control, and that if it was effective, they could purchase a stimulator for their own use. No patient was told that this was the only treatment available. If the stimulation was not helpful after an adequate clinical trial, it was discontinued. Stimulation techniques varied during the study. Usually, the patient was initially shown the device and the electrodes placed upon his hand and forearm to demonstrate the sensation of electrical stimulation. Most patients reported a threshold of tingling sensation and, as the voltage was increased, the development of a painful sensation in the area stimulated. After the patient was familiar with the device and the sensation it produced on normal skin, the electrodes were placed in the region of the patient's pain. Pulse width and frequency controls were placed at their lowest settings and the output increased until the patient reported a strong, but not painful sensation. The pulse width was then increased in small steps to mid-range while the output was decreased to maintain stimulation in the range of a strong, but tolerable sensation. Frequency of stimulation was manipulated to give the patient experience with a range of high (about 150 Hz) to low (about 10 Hz) stimulation; the patient's preference based on these results determined the frequency ultimately used. The electrodes were then moved about the skin in search of regions that would afford pain relief. When the patient's pain was in an extremity and relief was not obtained from local stimulation, the electrodes were placed proximally over the nerves to the involved area and an attempt was made to elicit a referred sensation into the painful area. Patients with low back and leg pain were stimulated over both the leg and back regions if stimulation at one site did not relieve pain in both areas. The initial trial of transcutaneous stimulation lasted up to 1 hour if the patient failed to achieve pain relief. We found that some patients obtained relief only after very localized areas responsive to stimulation had been identified by trial and error. An occasional patient achieved J. Neurosurg. / Volume 42 / March, 1975

dramatic relief from the first electrode localization and consequently required only a brief initial trial. When the patient reported relief of his pain during stimulation, the device was left on and in situ for several minutes and then turned off. If the pain did not recur within 30 minutes, the patient was asked to record the time it did recur and to return for another treatment. Patients who obtained no pain relief were seen the following day and the process was repeated. After three consecutive trials with no relief of pain, the patient was told that this method seemed unlikely to help him. Occasional patients refused to undergo a second or third trial after a negative initial result. If the patient reported the return of pain within 30 minutes, another, longer trial of stimulation was given. If the pain again immediately returned, the patient was usually loaned a stimulator on a short-term basis. Patients who reported on subsequent visits that stimulation controlled their pain were loaned a stimulator. They were carefully instructed in the proper use and care of their device. If pain relief continued for 1 to 2 weeks, the patient was asked to purchase a stimulator for his own use. Some patients were loaned a stimulator after an initial successful trial; although they had the opportunity to explore the utility of transcutaneous stimulation on a more intensive basis than outpatients, they fared neither better nor worse than other patients. Careful follow-up data have been obtained by personal interview, letter or telephone on all of the patients in this study. There have been no technical problems with the equipment used. Battery life is a function of frequency of use and output voltage, and averaged 3 weeks. Several patients have broken electrode leads, but this has been an infrequent occurrence. If the patient did not heed our warnings about changing stimulation sites and washing electrode sponges, areas of erythema might occur after 24 to 48 hours of continuous stimulation. This was easily controlled by discontinuation of stimulation at the inflamed sites. The stimulator does not pose an electrical hazard, but data are not available concerning the interaction with implanted cardiac pacemakers. It can interfere with surface monitoring of electrocardiographic (ECG) or electroencephalographic (EEG) activity. The size and weight of the original device was ob309

J. D. Loeser, R. G. Black and A. Christman jectionable to a few patients in spite of adequate pain relief. A new, smaller model of stimulator has solved this problem. The intensity of perceived stimulation is proportional to current density; the stimulator was therefore designed to maintain a constant current output. This causes the stimulator automatically to increase its output voltage when the electrode is lifted from the skin while the stimulator is on. The patient perceives this as a "bite" or sharp sting which, although harmless, is quite surprising. A similar sensation can occur if the stimulator is turned on prior to the application of the electrodes. Patients with a wide variety of diagnoses were included in this group. An effort was made to visit clinics run by several of our associates to obtain some patients with such diseases as rheumatoid arthritis and fractures due to osteoporosis who would not normally attend the Pain or Neurological Surgery Clinics. Results

General Results in 198 consecutive, unselected patients are summarized in Table 1. The age range of our patients was 16 to 83-years; 92 patients were male and 106 were female. We have established four categories of results. Group 1 (63 patients). Patients in this group experienced no significant pain relief after three thorough trials. Group 2 (135 patients). These patients reported significant initial relief of pain during the first trials. Group 3 (25 patients). These patients obtained long-term relief and were continuing to use transcutaneous stimulation as the primary treatment at the time of the most recent follow-up examination (or their pain had abated in the interim without utilization of any other form of therapy directed at this pain). All patients were followed for at least 1 year. Group 4 (30 patients). These patients were terminated for other reasons (PTOR). In this group initial success was achieved but the patient, his attending physician, or insurance carrier did not choose to proceed with this form of therapy. If some of these 30 patients had achieved long-term relief of their pain with transcutaneous stimulation, the long3]0

term success rate might have approached 25%. On the other hand, such factors as acceptability to the patient, his physicians, and the bill-paying organizations must be included in any assessment of the overall value of a therapeutic modality. Table 1 shows the wide range of diagnostic categories that we included. Sixty-eight percent of the patients experienced initial relief of their symptoms; 121/2% maintained effective pain relief on a long-term basis. Good results were not associated with any specific diagnostic entities. A Minnesota Multiphasic Personality Index (MMPI) could not be used to predict patients who would experience long-term relief. The small number of patients with any one etiology for pain makes statistical comparison of the diagnostic categories meaningless. Suffice it to say that no diagnosis is a guarantee of either success or failure of this form of therapy. The magnitude of success in some patients is illustrated by the following brief representative case reports.

Case Reports Case 1. This 46-year-old man injured his back in an industrial accident in 1950; in the years between the onset of his pain and his visit to our Pain Clinic he had had 13 major back operations, psychiatric therapies including electroshock and psychoactive drugs, physical therapies including heat, cold, exercises, braces, manipulations and traction, polypharmacologic therapies and multiple paramedical and quackish remedies. Abuse of alcohol and other drugs, including 3000 mg of Talwin intravenously each day and a bizarre life style were problems at the time of his University Hospital admission. A wide assortment of consultants agreed that this patient had intradural and extradural scarring as the cause of his pain and that there were significant psychological problems that added to his pain behavior. Transcutaneous stimulation was tried and afforded him complete pain relief. All of his medications were tapered and discontinued. He used the stimulator one to four times each day for up to 15 minutes. Sometimes he did not need to use it for several days but he always kept it with him. A quotation from his response to our follow-up query 1 year after initiation of transcutaneous stimulation included the statement: " . . . the stimulation has not cured J. Neurosurg. / Volume 42 / March, 1975

Relief of pain by transcutaneous stimulation TABLE 1 Relation of cause of pain and results obtained

Diagnosis headache atypical facial pain tic douloureux psychosomatic pain cervical arthritis low back pain myofascial syndrome perineal pain peripheral nerve entrapment post-surgical neuralgia cancer/radiation therapy spinal cord trauma peripheral neuropathy post-herpetic neuralgia phantom limb pain causalgia or causalgia-like pain post-traumatic leg pain fracture secondary to osteoporosis extremity arthritis acute postoperative pain miscellaneous total percent

No. of Cases 13 4 l 5 18 61 4 3 6 6 7 7 2 5 4 13 8 2 14 3 12 198

No Relief 10 1 0 3 3 14 0 2 2 t 4 4 1 1 1 4 3 0 2 0 7 63 327o

Initial Relief 3 3 1 2 15 47 4 1 4 5 3 3 1 4 3 9 5 2 12 3 5 135 68yo

Long-Term Relief 1 0 1 1 3 8 0 0 0 3 0 0 0 1 0 2 0 0 3 1 1 25 137o

PTOR* 1 1 0 0 1 13 1 0 3 1 0 0 0 1 0 1 2 0 2 1 2 30 157o

* PTOR = patient terminated for other reasons.

the problem by any means, but it has given me a very great amount of relief. There have been times when I may go as much as 2 weeks without using it, but I always have it with me at all times. I have been more free of pain than I can remember. Also it is a great relief to not have to take the great amount of medication . . . . I am very pleased and happy with the results I have." Case 2. This 70-year-old man was referred to the University Hospital for evaluation and treatment of right chest wall pain of 8 years duration. The onset of this burning and sometimes shock-like pain was not associated with known trauma, illness, or skin eruption. Right-sided D-6 to D-10 dorsal rhizotomies had produced only several weeks of pain relief even though anesthesia persisted in the denervated segments and the right upper quadrant abdominal reflex was absent. The patient used aspirin, Tylenol, and codeine without achieving pain relief. Psychiatric and psychological consultants felt that the patient was depressed and that emotional factors could be influencing his pain behavior. The transcutaneous stimulation promptly J. Neurosurg. / Volume 42 / March, 1975

relieved the chest wall pain. One year later he uses the stimulator for 1 to 5 minutes every morning and evening and requires no pain medication. He has not had to increase stimulation intensity, frequency, or duration to achieve complete pain relief. Case 3. This 56-year-old man complained of "excruciating" burning pain of the left chest wall since a thoracotomy and left upper lobectomy for carcinoma of the lung 2 years prior to his evaluation in Pain Clinic. A postoperative course of irradiation did not alter the pain. Tegretol was effective for 2 months but its benefits were evanescent. Mild analgesics were ineffective. H e showed hypesthesia in the right D-4 to D-5 region; light stroking of the skin in this region alleviated the pain. An M M P I revealed mild depression and anxiety, but psychiatric and psychological consultants did not feel that the patient's pain was significantly influenced by emotional or situational factors. Transcutaneous stimulation effectively alleviated the pain for several days; he purchased a stimulator and now uses it several times a week. Stimulation for 10 minutes in the 31 ]

J. D. Loeser, R. G. Black and A. Christman hypesthetic region gives complete pain relief for several hours and satisfactory partial relief for days. Case 4. This 31-year-old man was hospitalized for evaluation of back and leg pain after an industrial accident in 1967; he subsequently had several myelograms, a discogram, conservative therapy, and eventually an operative procedure which consisted of bilateral L3-4, L4-5, and L5-S1 explorations; L3-4 and L5-S1 discectomies; and an L3-S1 fusion. Pseudoarthrosis at L4-5 was treated by a second attempt at fusion 5 months later; and again 4 months after that by a third attempt. A fourth operation 8 months later included exploration and left S- 1 and S-2 dorsal rhizotomies. Persistent pain subsequently led to further diagnostic studies, steroid injections, physical therapy, and multiple drugs. At the time of his first admission to the University Hospital, he complained of continuous left leg and low back pain with occasional radiation into the interscapular region. Physical examination revealed multiple well-healed back incisions, limited range of motion of the back, straight leg raising positive at 60 ~ on the right and 45 ~ on the left, absent left ankle jerk, and hypesthesia of the lateral aspect of the left thigh and foot. Spine films showed a solid fusion; an electromyogram showed bilateral L-4 to S-2 paraspinal denervation and an MMPI was interpreted as indicative of moderate depression and passivity. Transcutaneous stimulation applied to both the low back and left leg effectively alleviated the pain, nine months later he was using the stimulator two to four times a day for 30 minutes, and obtaining 4 to 6 hours relief from each session. He has been able to reduce his drug intake significantly and increase his physical activity. Case 5. This 29-year-old woman was admitted to the University Hospital for evaluation of intractable low back and right leg pain. She first developed back pain 11 years earlier; two lumbar laminotomies and discectomies had not altered her pains. After 10 years of drugs, physical therapy, and psychiatric care she was referred to our institution. She showed paravertebral muscle spasm, reduced range of motion of the back, right sciatic notch tenderness, an absent right ankle jerk, but no sensory or motor loss. MMPI revealed her to be "perennially unhappy, anxious, and melodramatic, with pain 312

symptoms likely to be under the control of environmental or emotional factors." Transcutaneous stimulation of the back or right leg relieved pain in the area stimulated for the duration of stimulation. She found the stimulator to be too bulky and the electrodes too cumbersome for use during working hours; an implanted stimulator was placed around her sciatic nerve. This device has totally relieved her back and leg pain. The response to transcutaneous stimulation accurately predicted the results from the implanted stimulator. Case 6. This 69-year-old woman had a 10year history of left-sided second and third division tic douloureux. She had been treated with peripheral neurectomies, vitamins, diphenylhydantoin, and carbamazepine with only partial and temporary relief of symptoms and unacceptable side effects. There was an area of hypesthesia at the left corner of the mouth and a patch of hyperesthesia in the left malar region. Her apparent depression was corroborated by an MMPI. Treatment with antidepressant medication did not alter the pain. During an exacerbation of the facial pain she was treated with transcutaneous stimulation to the areas of her face in which she felt lancinating and burning pains; this lessened the lancinating pains but the lowintensity background burning dysesthesia persisted. She now uses her stimulator when she has a flurry of severe pains and finds she can quickly turn off this pain with the stimulator. Prophylactic stimulation does not seem to be effective in preventing attacks. Discussion

We have been able to make a few observations which may help in the selection of patients for this form of therapy. The existence of iatrogenic drug addiction is not a contraindication to transcutaneous stimulation. If pain relief is obtained, as is true for any other form of therapy, it is quite easy to taper and eventually discontinue the use of narcotics. Some patients promptly become "addicted" to their stimulator, but the habitual use of this device does not seem to lead to physiological dependence or withdrawal reactions. Patients who are confused because of heavy narcotic, sedative, or tranquilizing drug intake are poor candidates for any form of therapy and their drug problem must be dealt with prior to the J. Neurosurg. / Volume 42 / March, 1975

Relief of pain by transcutaneous stimulation The patients in this study are individuals in evaluation of transcutaneous stimulation. Stimulation delivered to an anesthetic whom most other forms of therapy had failed. region has never provided relief of pain in that Some had expensive drug habits, others spent area or any other area of the body. On the time and money shopping for new physicians other hand, stimulation applied to regions and treatments. We found that this process adjacent to anesthetic areas sometimes has could be halted in at least one out of eight provided good relief of a pain which was patients by transcutaneous stimulation, a referred exclusively to the anesthetic region. therapy which is both inexpensive and Indeed, some patients reported short-term without significant complication. Occasional relief of pain from stimulation of the skin patients will require implantation of a contralateral to their pain; however, when peripheral nerve stimulator or dorsal column given the choice these patients always stimulator because of one or more of the preferred stimulation on the side of the pain. following factors: 1) a wide area must be We also found that patients whose chronic stimulated to get effective pain relief; 2) the pain was associated with a profound loss of electrodes cannot be worn conveniently over cutaneous sensation rarely seemed to benefit the stimulation site; 3) stimulation of a nerve from transcutaneous stimulation. Patients is required and cannot be achieved by whose pain was perceived in an area which transcutaneous stimulation; 4) some pain had essentially normal sensation seemed to be states may require spinal cord stimulation for more likely to find relief with transcutaneous relief. We do not implant a stimulator if stimulation. We have not studied the specific transcutaneous stimulation is effective and modalities or thresholds of sensation which acceptable to the patient. must be present if pain relief does occur. We have now seen several patients in whom Some patients achieved pain relief only transcutaneous stimulation by other when the stimulator was on. Others used the physicians had been considered a failure. stimulator for brief periods (5 to 30 minutes) Some of these patients did have a good on a regular schedule, much as they had used response to transcutaneous stimulation in our analgesic medications; they found that com- clinic. In general, the original "failure" was plete relief of pain lasted many hours after due to an inadequate attempt to find suitable stimulation had been discontinued. Most stimulation sites and l~arameters of stimulapatients established a stable utilization tion. Many physicians do not have the time to pattern within the first week of therapy. perform the initial evaluation of transThose who experienced continuing relief did cutaneous stimulation. The easy successes not need to increase stimulation time, may be dramatic, but a significant number of stimulus intensity, or frequency of treatment. patients will achieve pain relief only after a A long-term success rate of 121/2%does not more thorough trial of stimulation. We appear to be a good advertisement for any believe, therefore, that transcutaneous form of therapy. Yet we are convinced that stimulation usually should be administered by transcutaneous stimulation is a valuable part adequately trained paramedical personnel of our therapeutic repertoire. It is well known who will be thorough in their evaluation of that the placebo effect will yield a short-term stimulation sites and parameters. success rate of approximately 33% for any All of the patients who reported pain relief form of therapy such as analgesic medication, from transcutaneous stimulation also hypnosis, psychotherapy, surgery, and so reported that they enjoyed the sensations forth. However, this is a short-term effect, produced by the stimulator. This effectively and there is little evidence to support the con- pleasurable response was not seen in subjects tention that the placebo effect persists for any who were stimulated in the absence of chronic significant period of time. Indeed, the mere pain or in patients with chronic pain who did presence of a chronic pain patient in our clinic not report pain relief with stimulation. The attests to the short duration of both placebo majority of patients described a clear and direct effects of prior therapy. Further- difference between detection threshold and an more, there are little data related to the intensity of stimulation which was painful. A problem of the generalization of placebo few patients reported that transcutaneous reactions derived from differing forms of stimulation was an unpleasant, painful sensatreatment. tion at any level above stimulus detection J. Neurosurg. / Volume 42 / March, 1975

3]3

J. D. Loeser, R. G. Black and A. Christman threshold, whether applied to areas of pain or elsewhere over their bodies. Without exception, this unusual response had the following implications: 1) transcutaneous stimulation was not effective in alleviating the patient's pain; 2) the patient would not permit more than one trial or, rarely, two; 3) no clear-cut diagnosis of the etiology of the patient's pain could be made; 4) the patient's pain did not seem to be amenable to any other mode of therapy utilizing drugs or surgery; 5) psychologic factors seemed to play a large role in the genesis of the patient's pain behavior. Accurate long-term follow-up data upon patients with chronic pain is difficult to find. We believe that transcutaneous stimulation is just as effective as any pharmacological or surgical therapy for patients who have already experienced failure of operations, drugs, and treatments, as well as deterioration of doctor-patient relationships. Since it

3]4

does not add to the patient's neurological deficit, depress affect, or require expensive equipment or professional administration after initial evaluation, transcutaneous stimulation is a useful form of therapy. The small number of totally cured patients justifies a trial for every patient with chronic, intractable pain until accurate prognostic criteria can be identified.

Acknowledgment The financial and technical support of Stimtech Corporation, Minneapolis, Minnesota, is gratefully acknowledged.

Address reprint requests to: John D. Loeser, M.D., Department of Neurological Surgery, University of Washington School of Medicine, RI20, Seattle, Washington 98195.

J. Neurosurg. / Volume 4 2 / M a r c h , 1975

Relief of pain by transcutaneous stimulation.

A series of 198 patients with chronic pain of diverse etiology was carefully analyzed for epidemiologic and descriptive factors which might influence ...
649KB Sizes 0 Downloads 0 Views