Transcutaneous electrical nerve stimulation in the relief of primary dysmenorrhea.

Transcutaneous Electrical Nerve Stimulation in the Relief of Primary Dysmenorrhea Dysmenorrhea, or painful menstruation, affects 52% of postpuhescent women with 10% of these women incapacitated for one to three days per month. [1] Dysmenorrhea appears in two forms: 1) primary and 2) secondary. Primary dysmenorrhea is defined as pain during menstruation that is not the result of a macroscopic pelvic pathological condition; that is, the woman has had a normal pelvic examination. Secondary dysmenorrhea is the result of a macroscopic pelvic pathological condition. [1] Symptoms seen in both forms include spasmodic pain over the low abdomen, possibly radiating to the anterior thigh; low back pain; nausea; diarrhea; headache; fatigue; and sometimes syncope and collapse. These symptoms can begin a few hours or days before menstruation and last up to two or three days. [1]

The causes of primary dysmenorrhea have not been defined spefically, but many possible causes have been presented. Psychologica factors may be possible as in any case of pain, [1] but no conclusive studies have shown these factors as the cause. [2] Endocrine factors have been suggested because primary dysmenorrhea occurs only during ovulatory cycles. Recent studies propose that vasopressin levels are increased during the menstrual phase of primary dysmenorrheic women resulting in dysrhythmic uterine contractions or cramps. [1] Cervical obstruction or stenosis has been suggested since the days of Hippocrates, [3] but no evidence has been reported to suggest this condition as a cause of primary dysmenorrhea. [1] Recent studies have indicated an increase in intrauterine prostaglandin production and a decrease in ovarian steroid hormone as causes of primary dysmenorrhea. [1,4] These changes result in an elevated intrauterine pressure, which subsequently results in a decreased uterine blood flow, ischemia, and pain. [1,4] The prostaglandins that are released, mainly [PGF.sub.2a] and [PGE.sub.2], also sensitize the nerves in the uterus to the action of chemical and physical stimuli. [1]

Methods of treatment for dysmenorrhea range from prostaglandin synthetase inhibitors and oral contraceptives to noninvasive methods such as heat packs, biofeedback, relaxation techniques, and acupressure. [5] Traditional acupuncture has been documented as successful by Walker and Katz [6] and Steinberger, [7] resulting in an attempt by other investigators to use transcutaneous electrical nerve stimulation over traditional acupuncture points to achieve the same success. [8-10]

Transcutaneous electrical nerve stimulation is an accepted method of noninvasive, nonnarcotic pain control. [5] It has been used successfully in control of postoperative pain [11,12]; low back pain [13,14]; labor and delivery [15,16]; and cystitis, pancreatitis, angina pectoris, thrombophlebitis, and dysmenorrhea. [5,17] Conventional TENS and "acupuncture-like" TENS are used most frequently for treatment. Conventional TENS requires a high pulse rate with a low intensity, whereas acupuncture-like TENS uses a low pulse rate with a high intensity, often as high as the patient can tolerate. Kroth studied relief of dysmenorrhea with acupuncture-like TENS in 10 women and saw significant pain relief, but no control group was used. [10] Janke studied the effectiveness of acupuncture-like TENS using an experimental group that received treatment on acupuncture points and a control group that received conventional TENS on points not believed to be associated with dysmenorrhea. [9] She reported a 50% decrease in pain for both groups, suggesting that any form of electrical stimulation may relieve the pain of primary dysmenorrhea. Mannheimer and Whalen compared the effectiveness of conventional TENS and acupuncture-like TENS and found significant relief in primary dysmenorhea with both forms. [5] Neighbors et al studied 20 women, 10 receiving treatment of dysmenorrhea with acupuncture-like TENS and 10 receiving a placebo pill. Their results supported the hypothesis that a single treatment with acupuncture-like TENS would significantly decrease the pain of primary dysmenorrhea. [8]

Acupuncture-like TENS is believed to work via release of endorphins in the brain. [5] Endorphins are natural opiates that block the input of pain, possibly via the dorsolateral funiculus. These endorphins bind to receptors in the periaqueductal gray matter and lead to an antidromic inhibitory process that blocks the nociceptive impulse from reaching the substantia gelantinosa. [18]

The purpose of this study was to replicate the study by Neighbors et al [8] to determine the effectiveness of acupuncture-like TENS in the treatment of primary dysmenorrhea. Because physical therapists often use TENS to decrease pain, we hoped to discover whether it can be used to decrease pain for the large number of women who are affected by dysmenorrhea. The hypothesis of this study was that a single treatment with acupuncture-like TENS would reduce significantly the pain of primary dysmenorrhea.

Method

Subjects

Twenty-one women who were experiencing self-reported dysmenorrhea volunteered to participate in this study. These women all reported having a pelvic examination within the previous two years that revealed no pathological problems or secondary dysmenorrhea. The subjects were assigned randomly to one of two groups: 1) an Experimental Group (n = 10) that received TENS treatment or 2) a Control Group (n = 11) that received placebo pill. This study received the approval of the Institutional Review Board for Human Use, The University of Alabama at Birmingham.

Protocol

Each subject notified the investigator upon onset of her pain, and a time was scheduled for that day for either a TENS treatment (Experimental Group) or treatment with a placebo pill (Control Group). The treatment was administered in a clinical laboratory room at The University of Alabama at Birmingham. The subjects were instructed to take no pain medication for at least four hours before treatment. Before beginning treatment, the subjects completed a menstrual history questionnaire, a consent form, the pain rating index (PRI) of the McGill Pain Questionnaire (Appendix 1), and a visual analog scale (VAS) (Appendix 2). The PRI and VAS were used to establish a baseline level of pain.

At this point, each subject participated in a study by Reynolds et al [19] that involved measuring the electrical conductance at four auricular acupuncture points, bilaterally, with the Stayodyn Insight stimulator. (1) The auricular acupuncture points assessed were the uterus, endocrine, low back, and ovary. [19] After this portion of the Reynolds et al study, [19] each Control Group subject in our study took a placebo pill with a glass of water in the presence of the investigator (D.L.) The subject was then positioned prone on a plinth for 30 minutes with pillows under her head, abdomen, and lower legs. The subjects in the Experimental Group were positioned in the same manner as those in the Control Group. Two NTRON 2600 TENS units (2) were used, and eight 1.5-in (3) diameter karaya electrodes were placed bilaterally on the following acupuncture points: Stomach 36, Spleen 6, and Bladder 21 and 29 (Fig. 1).

The following TENS variables were used: 1) the lowest rate possible (1 pulse/sec), 2) the highest intensity that was tolerable for the subject for 30 minutes, and 3) the lowest possible pulse duration (40 msec). If the subject could tolerate the highest intensity stimulation, the duration of the pulse was increased to the point of tolerance. Tolerance was defined as the level at which the subjects asked the investigator to stop increasing the stimulation. The TENS unit was rechecked after 5 minutes. If adjustments in intensity were needed to attain the subject's tolerance level, they were made at this time. The treatment was given for a total of 30 minutes, and the electrodes were then removed.

The posttreatment pain scales were completed immediately after the TENS treatment for the Experimental Group and immediately after the 30-minute rest period for the Control Group. After completion of the pain scales, the same auricular acupuncture points of each subject were measured for electrical conductance by Reynolds et al. [19]

Pain Measurement

The subject's pain level was assessed using the PRI and the VAS. The PRI gives the subject a choice of words describing her pain at that moment. The words are assigned a rank value that allows a pain index to be calculated. The VAS is composed of a 10-cm horizontal line with the words "no pain" on the left and "pain as bad as it could be" on the right. The subject is instructed to make a mark on the line at a point that represents her pain level at that time. These pain scales were completed immediately before treatment before the first measurement of conductance at auricular points and immediately posttreatment in the presence of the investigator before the second measurement of conductance. After the measurement of conductance at auricular points was taken, the subject was dismissed and instructed to complete the pain scales again in 30 minutes, 60 minutes, 120 minutes, 180 minutes, and the next morning upon awakening. Each subject was instructed not to take any pain medication until after completion of all the pain scales unless it was absolutely necessary. A self-addressed, stamped envelope was provided for return of the completed pain scales.

Data Analysis

The value obtained pretreatment and posttreatment from the VAS and the PRI were analyzed using a two-factor repeated-measures analysis of variance (ANOVA). An alpha level of .05 was chosen as the criterion for statistical significance in all tests. A pair-wise comparison using Tukey's Honestly Significant Differenc (HSD) test was used to follow up statistically significant main effects over time.

To better assess clinical significance, the percentage of change was calculated for each subject, and the mean of these values was calculated to obtain a mean percentage pain reduction value. In addition, the number of subjects experiencing at least a 50% pain reduction at each of the posttreatment times was noted.

Results

The subjects ranged in age from 20 to 38 years (X = 25.9 years), with a mean age of menarche of 11.6 years for the Experimental Group and 12.1 years for the Control Group. The main complaints from the subjects were abdominal pain, cramps, and low back pain. Ten subjects also complained of irritability, headaches, and general aching.

Twenty-one subjects were treated in this study with pain scales completed immediately posttreatment; at 30, 60, 120, and 180 minutes posttreatment; and the next morning. Two subjects in the Experimental Group were the only subjects who did not complete the information at all of the posttreatment measurement times because they were asleep at that time and needing to take additional medication. They did not complete the scales at 180 minutes posttreatment and the next morning. Given our small sample size, we did not want to drop these two subjects from the study because they were missing the last two of their seven data points. Thus, we substituted their pain scores at 120 minutes posttreatment for their missing scores at 180 minutes posttreatment and the next morning; that is, we assumed no change after 120 minutes for these subjects. We analyzed the data with and without the two subjects, and found the same results in each analysis.

Figures 2 and 3 present mean pain values for the Experimental and Control Groups using the PRI and VAS, respectively. The ANOVAs revealed statistical significance (p [is less than] .001) only in time of measurement for both the VAS and PRI (Tabs. 1, 2), Group and interaction between group and time were not statistically significant for either the PRI or the VAS. Thus, pain relief was approximately the same for the two groups over time. For both the PRI and the VAS, Tukey's HSD test showed a statistically significant difference (p [is less than] .05) between the pretreatment mean and each posttreatment mean, but we found no statistically significant differences among the six posttreatment means.

At the initial posttreatment measurement time, the VAS revealed a 47.1% decrease in pain for the Control Group and a 65.2% decrease in pain for the Experimental Group, and the PRI revealed a 55.6% reduction in pain for the Control Group and a 61.9% reduction in pain for the Experimental Group. The number of subjects experiencing at least 50% pain reduction are shown in Table 3.

The median Pearson product-moment correlation between the VAS and the PRI over the seven measurement times was .72 (p [is less than] .05). This value represents a strong positive relationship between the two measures.

Discussion

As research into the cause of primary dysmenorrheic pain continues to demonstrate that the cause is not psychological, [1,2] more research is being conducted to discover ways to decrease and hopefully eliminate this pain for many women. Some current research has focused on acupuncture and TENS. Steinberger used acupuncture at four acupuncture points for five consecutive days before the menstrual cycle of 48 women. [7] Of those 48 subjects, 58.3% had total cessation of pain before and during menstruation, and 25% had greatly decreased symptoms. The pain relief or pain reduction lasted up to six months for these women. [7] Helms used acupuncture on 43 dysmenorrheic women who were divided into four groups: 1) the Real Acupuncture Group (n = 11), 2) the Placebo Acupuncture Group (n = 11), 3) the Standard Control Group (n = 11), and 4) the Visitation Control Group (n = 10). [17] Although the results of the study were not statistically significant, 10 subjects in the Real Acupuncture Group, 4 subjects in the Placebo Acupuncture Group, 2 subjects in the Standard Control Group, and 1 subject in the Visitation Control Group showed improvement. Improvement was defined as an average posttreatment score of less than half of the pretreatment pain score. [17] Mannheimer and Whalen compared the effectiveness of conventional TENS and acupuncture-like TENS and found significant relief of primary dysmenorrhea with both forms. [5] Kroth, in an unpublished study, used acupuncture-like TENS to treat 10 women with primary dysmenorrhea. [10] She found that all 10 subjects experienced more than 50% pain reduction 180 minutes after treatment. She, however, did not use a control group. [10] Janke followed up her study by treating women with acupuncture-like TENS using a sham TENS for a control group. [9] She found both groups to have a statistically significant reduction in pain, resulting in the rejection of the proposed hypothesis that a single treatment with acupuncture-like TENS would reduce the pain of primary dysmenorrhea. [9] Neighbors et al in another follow-up study treated 10 women with acupuncture-like TENS and 10 women with a placebo pill. [8] They found a statistically significant reduction in pain immediately posttreatment for subjects treated with acupuncture-like TENS, with 7 experimental subjects receiving at least 50% relief of pain and only 1 control subject receiving the same relief. [8]

All of these studies showed significant pain relief for the subjects receiving acupuncture or acupuncture-like TENS. Our study was an exact duplicate of the Neighbors et al study [8] and, therefore, should have revealed a significant difference between the groups treated with acupuncture-like TENS and the placebo group. The results from our study indicated that the Control and Experimental Groups received approximately the same amount of pain relief. The fact that the Control Group in this study also received pain relief, whereas the control group in the Neighbors et al study [8] did not, may be due to the fact that all of our subjects participated in a concurrent study determining electrical conductance at auricular acupuncture points. [19] The control subjects in the Neighbors et al study [8] received only a placebo pill. The auricle has a rich sensory innervation that has led investigators to believe that stimulation to the auricle may affect different areas of the body, depending on the area stimulated. Investigators have suggested that there is a link between sensory nerves of the auricle and the central nervous system that may produce analgesic effects. [20] Because the probe from the Staodyn Insight stimulation was placed on four bilateral auricular points of each subject for determination of electrical conductance at those points, each of those points was tactilely stimulated. That is, although the points were not stimulated electrically, they were treated by acupressure. Thus, the acupressure treatment that the Control Group received may have decreased their pain.

Another factor that may have contributed to decrease in pain for the Control Group may have been the placebo effect. [21] The 47.1% and 55.6% reduction in pain for the VAS and PRI, respectively, experienced by the Control Group cannot be attributed totally to the placebo effect, but may be due to the treatment received through the Reynolds et al study. [19]

This study did reveal a significant decrease in pain over time for both the Control Group and the Experimental Group. Decreases in pain lasting as long as hours and days have been documented by other researchers after treatment with TENS. [14] We attempted to control for other causes for the continued decrease in pain over time by requesting that the subjects take no pain medication if possible until all data were collected and by recording their pain level after a night's sleep.

The limitations of this study include the small sample size and the fact that each subject participated in the Reynolds et al study [19] and received a treatment by acupressure to auricular points. The possibility that auricular stimulation reduced the pain of primary dysmenorrhea for the Control Group in this study suggests the need for a study of the effect of true auriculotherapy on primary dysmenorrhea. Although the results of this study did not show a statistically significant difference between groups, an average of at least 50% pain reduction was noted for both groups. For this reason, acupuncture-like TENS is a possible soulution for women who suffer from severe dysmenorrhea and do not experience pain relief with other forms of treatment. Because of the large number of women affected by dysmenorrhea and because 10% of these women are incapacitated by this condition, [1] continued research into the effects of TENS and auriculotherapy on primary dysmenorrhea is warranted.

Conclusion

In a group of women experiencing the pain of primary dysmenorrhea, acupuncture-like TENS and a placebo pill were used as treatments, and the amount of pain relief was recorded at various posttreatment times. The results of this study revealed a statistically significant reduction in pain over time for the Control and Experimental Groups. We found no statistically significant difference in pain relief between the groups. Both groups showed an average of at least 50% reduction in pain immediately posttreatment. The decrease in pain for the Control Group may have been due to their participation in another study that involved determining the electrical conductance at four auricular acupuncture points. The decrease in pain for the Experimental Group may have resulted from a combination of the acupuncture-like TENS and auricular acupressure provided by participation in the other study.

(1) Staodynamics, Inc, PO Box 1379, Longmont, CO 80502-1379.

(2) NTRON International Sales Co, 3833 Redwood Hwy, PO Box 7000, San Rafael, CA 94912.

(3) 1 in = 2.54 cm.

References

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Diewers, MS, is Physical Therapist, Spain Rehabilitation Center, University of Alabama Hospitals, 1717 6th Ave S. Birmingham, AL 35294. She was a graduate student, Division of Physical Therapy, School of Health Related Professions, The University of Alabama at Birmingham, Birmingham, AL 35209, when this study was conducted. This study was completed in partial fulfillment of Ms Lewer's master's degree program requirements. Address correspondence to 5608 9th Ave. S, Birmingham, AL 35212 (USA).

J Clelland, MS, is Associate Professor and Associate Director, Divison of Physical Therapy, School of Health Related Professions, The University of Alabama at Birmingham.

J Jackson, PhD, is Assistant Professor, Office of Educational Development, School of Medicine, The University of Alabama at Birmingham.

R Varner, MD, is Assistant Professor and Director, Division of Primary Obstetrics and Gynecology, Department of Obstetrics and Gynecology, The University of Alabama at Birmingham.

J Bergman, PhD, is Professor, Division of Physical Therapy, and Director, Physical Therapy Division, Sparks Center, The University of Alabama at Birmingham.

This article was submitted September 16, 1987; was with the authors for revision for 15 weeks; and was accepted May 26, 1988.