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Tension headaches: Psychophysiological investigation and treatment
Journal of Psychosomatic Research, Vol. 22, pp. 389 to 399. © Pergamon Press Ltd. 1978. Printed in Great Britain.
TENSION HEADACHES: PSYCHOPHYSIOLOGICAL INVESTIGATION AND T R E A T M E N T PAUL R. MARTIN* a n d ANDREW M. MATHEWS'~
(Received 10 May 1978) Abstract--Two experiments investigating the aetiology of chronic tension headaches are reported. The first compared neck and forehead EMG of tension headache patients with that of non-headache control subjects whilst at rest and whilst performing a stressful task. The two groups were also compared in terms of pain threshold, and the effect of a vasodilating agent on headache intensity was assessed. In general, EMG levels were similar in the two groups and there were few clearly significant differences. The forehead EMG of the headache patients was marginally higher than that of the control subjects when at rest, but this trend was reversed under stress. In the second experiment, tension headache patients received either EMG feedback training or progressive relaxation training. Results showed the two treatment conditions to be equally effective for reducing recorded headache activity. Headache reduction was not related to success at lowering forehead or neck EMG in the laboratory. Within subject correlations between forehead or neck EMG, and headache intensity at the time of EMG recording, failed to reach significance. Comparing subjects when experiencing headaches and when headache-free revealed no difference in neck EMG, but significantly lower forehead EMG during headaches. The results were interpreted as failing to support the widely-held belief that chronic tension headaches are primarily caused by excessive tension in the skeletal muscles of the head or neck. EXPERIMENT 1 EXPERIMENTS investigating the aetiology o f tension headaches have c o n c e n t r a t e d on two variables, electrical activity ( E M G ) in the head a n d neck muscles, a n d cerebral b l o o d flow. Papers r e p o r t i n g on the latter variable have p r o d u c e d conflicting results - two studies have suggested tension headaches are associated with cranial vasoconstriction [1, 2], whilst a larger study has suggested they are associated with cranial v a s o d i l a t i o n [3]. A n u m b e r o f early studies [1, 4, 5] have p r o d u c e d d a t a suggesting tension headaches are associated with elevated tension in skeletal muscle, b u t they are all open to m a j o r criticisms. The hypothesis t h a t ' t e n s i o n ' headaches are the result o f excessive skeletal muscle activity has been the object o f renewed interest following evidence t h a t training to reduce E M G levels c a n decrease r e p o r t e d h e a d a c h e pain [6]. Hence Philips [7] has recently investigated the muscle tension levels o f h e a d a c h e patients by c o m p a r i n g n o n - h e a d a c h e c o n t r o l subjects with patients suffering from tension headaches, migraines and m i x e d m i g r a i n e - t e n s i o n headaches. E M G was m o n i t o r e d during headache-free episodes f r o m the frontalis, temporalis, neck a n d trapezius muscles over four-minute rest periods. Analysis o f variance showed significant differences only with frontalis E M G ; the o r d e r o f the groups being control, tension, mixed, migraine, with the last g r o u p having the highest level. A l t h o u g h the difference between the tension a n d control groups reached significance (p <0.05), the difference between the tension a n d migraine groups did not. Bakal a n d K a g a n o v [8] c o m p a r e d tension h e a d a c h e a n d migraine patients with headache-free controls in terms o f E M G (forehead and neck) and vascular activity (pulse flow velocity from *Research Clinical Psychologist, Oxford Rehabilitation Research Unit, Nuftield Orthopaedic Centre, Oxford OX3 7LD, England. tProfessor of Psychology, St. George's Hospital Medical School, London SW17, England. 389
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PAUL R. MARTIN and ANDREW M. MATftEWS
s u p e r f i c i a l t e m p o r a l a r t e r i e s ) . H e a d a c h e p a t i e n t s a t t e n d e d f o r o n e session w i t h a s e v e r e headache and for another without a headache, but presence or absence of headache d i d n o t s i g n i f i c a n t l y affect t h e m e a s u r e s used. M i g r a i n e p a t i e n t s w e r e f o u n d t o h a v e significantly higher forehead EMG than tension headache patients, who had almost i d e n t i c a l f o r e h e a d E M G levels to t h e c o n t r o l ' s b u t s i g n i f i c a n t l y h i g h e r n e c k E M G . Pulse velocity responses obtained from the patients (tension headache and migraine) decreased in response to noise stimuli, supposedly indicating vasoconstriction, while p u l s e v e l o c i t y r e s p o n s e s o f t h e c o n t r o l s i n c r e a s e d to t h e s a m e s t i m u l i , i n d i c a t i n g vasodilation. The differences, however, were only significant for one of the velocity measures. T h e p u r p o s e o f t h e first e x p e r i m e n t w a s to i n v e s t i g a t e q u e s t i o n s a r i s i n g f r o m h y p o t h e s e s a b o u t t h e a e t i o l o g y o f t e n s i o n h e a d a c h e s ; specifically w h e t h e r r e s t i n g E M G levels w e r e h i g h e r t h a n in c l o s e l y m a t c h e d c o n t r o l s u b j e c t s ; w h e t h e r stress p r o d u c e d a d i s p r o p o r t i o n a t e i n c r e a s e o r s l o w e r r e c o v e r y in E M G ; w h e t h e r p a t i e n t s were more sensitive to head pain; and whether headaches responded to a vasodilating agent. METHOD General practitioners and neurologists in the area were asked to refer patients who had suffered from tension headaches frequently (one or more a week) for at least a year. Such patients were seen by one of two medical assessors who assigned them to one of three categories- 'primary muscle tension', 'combined muscle tension and other pathology', or 'other types of headache' and rated the diagnosis as possible, quite likely or very likely. No fixed diagnostic criteria were adopted, as in the absence of a generally agreed method of classification it was thought more appropriate to collect a representative sample of patients agreed by two clinicians to be suffering from tension headaches. Out of 50 patients referred, 13 were excluded as not being so diagnosed by the medical assessor, leaving a sample of 37 patients. The average age of these patients was 36 years (range 16-62), the average duration of headache problem was 12 years (range 1-46), and 7 of the patients were male. A nonheadache control group was assembled from the staff of an adjoining hospital, and subjects in the two groups were individually matched for age, sex and socio-economic status. None of the controls were well known to the experimenter, and none had previously participated in psychophysiological research projects. All subjects attended a single laboratory session during which E M G from the forehead and neck was monitored throughout. Standard positions were used for electrode attachment [9], and E M G activity was amplified and filtered (frequency range 30-1000 Hz) with a Devices M I 9 polygraph. A PDP-12 computer sampled from each of the E M G sites every millisecond providing the raw data for subsequent analysis. Sessions were held in a temperature-controlled (22°C), sound-attenuated laboratory, and subjects sat in a comfortable armchair with a high back. Electrode sites were marked using a template, and after skin preparation, gold-plated disc electrodes were attached with elastoplast. Electrode resistance was checked to ensure that it was below 10kQ. The experiment then preceded in four phases, in the first phase, lasting ten minutes, subjects were simply told to sit back and relax with eyes closed. In the second phase, pain thresholds were measured using a graded series cf thermal stimuli from a light focussed onto the forehead [10]. Successively more intense heat stimuli were presented at one-minute intervals until reported to be 'slightly painful'. The reliability of threshold measurement was estimated as 0.78 (p < 0.001, n = 12) from another sample of subjects retested after an interval of four months. The third phase was a stress condition which consisted of presentation of 24 problems from the Nufferno Level Intelligence Test [11] using a carousal slide projector. These problems consisted of series of letters and subjects were required to work out the next letter in the series within 20 seconds. Subjects were told whether their solution was correct, or if at the end of the time limit no solution was offered, they were given the correct solution before presentation of the next problem. The level of difficulty of the problems, and the time interval used, were selected so that only a proportion of the problems could be solved within the time limit. The fourth phase lasted 10 minutes and was similar to the first in that instructions were given to relax with eyes closed for 10 minutes. At the beginning and end of each phase, subjects were asked to rate their headache intensity (HI) on
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the six-point scale devised by Budzynski [6]. Those patients who gave a rating of greater than zero at the end of the fourth phase were asked to inhale a vasodilator (amyl nitrite), and a matching placebo (pabrinex), separated by a five-minute interval. Order of administration was balanced across patients, and they were asked to rate their HI immediately before and after inhaling each drug to assess any effects. ANALYSIS The EMG data was initially analysed using an analysis of variance suitable for repeated measures. The data included in the analysis derived from three 6-minute periods--the final 6 minutes of the initial relaxation period, the first 6 minutes of the stress task (6 minutes being the minimum time taken to complete the stress task), and the first 6 minutes of the post-stress relaxation period. Each 6-minute period was divided into twelve 30-second trials, and average scores were calculated for each trial. A logarithmic transformation was applied to the EMG data prior to analysis as the raw distributions were positively skewed, and mean levels of this variable are plotted graphically as Figs. 1 and 2. The main factors included in the subsequent analysis were: groups (headache patients vs controls); occasions (initial relaxation vs stress task vs post-stress relaxation); EMG (forehead vs neck) and trials. 1.3
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FIG. 2.--Comparison of headache patients and controls in terms of neck EMG.
RESULTS The main effect for groups fell well short of statistical significance, but two interactions involving the groups factor reached the 5 % level of significance--groups x occasions (p < 0"01) and groups
392
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>: trials (p < 0.05). The former interaction indicated that the headache patients tended to ha~e higher E M G during the relaxation conditions but lower E M G during the stress condition, while the latter interaction reflected the slight tendency for controls (but not patients) to show EMG increases within some 6-minute periods. When analyses of variance were calculated for each E M G site and each occasion separately, the main effect for groups failed to reach the 5 ~ level of significance for any of the six analyses. Hence the headache patients did not significantly differ from the controls in tcrms of forchead or neck E M G for any single condition of relaxation or stress taken on its own. The data were then re-analysed after splitting the headache patients and their corresponding controls into three groups, according to whether patients were headache-free, experienced a slight headache (rated between zero and two), or experienced a moderate to severe headache (rated as equal to or greater than two) during the session. The pattern of results in each of the three analyses was essentially the same, so that even patients experiencing moderate to severe headaches did not have significantly higher forehead or neck EMG than controls. The data were also re-analysed comparing those patients whom the medical assessor had considered to be the most unambiguous tension headache cases (diagnosed as 'primary muscle tension; very likely'), with those with more mixed symptomatology. In none of thcse analyses werc there any difference in E M G between groups, suggesting that the original findings were not distorted by inclusion of diagnostically inappropriate patients. The average pain threshold for the headache patient group was unexpectedly higher than for the control group, but a t-test for dependent groups showed that the difference was not statistically' significant (t = 1.07, d.f. = 36). A correlation was calculated for the headache patients between pain threshold and the average of the HI ratings before and after threshold measurement. As this correlation was also not significant (r = 0"13) there does not appear to be any cvidence that complaints of headache are attributable to greater sensitivity to pain. Twenty-three patients were given drugs following the post-stress relaxation period, and the results are presented in Table 1. The table shows that inhaling the vasodilator led to an increase in headache severity on 43 ~ of occasions and no change on 48 ~ of occasions. The large percentage reporting an increase in headache severity cannot be attributed to factors such as demand characteristics, since no increases were reported after inhaling the placebo and this difference was highly significant (p < 0.001 ) by Z2 test. Hence, these results suggest that pain is associated with cranial vasodilation rather than vasoconstriction, at least in those patients already experiencing a headache. TABLE I.--HEADACHE RESPONSE TO DRUG ADMINISTRATION
Amyl nitrite Placebo
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Worse 10 0
DISCUSSION T h e E M G d a t a p r e s e n t e d h e r e is m o r e s i m i l a r to P h i l i p ' s d a t a t h a n B a k a l ' s d a t a in f i n d i n g t e n s i o n h e a d a c h e p a t i e n t s t e n d t o differ f r o m n o n - h e a d a c h e c o n t r o l s ill t e r m s of forehead rather than neck EMG (during the post-stress relaxation period the d i f f e r e n c e in f o r e h e a d E M G w a s s i g n i f i c a n t at t h e 6 o4 level). H o w e v e r , t h e m o s t s t r i k i n g a s p e c t o f t h e d a t a f r o m t h e s e t h r e e s t u d i e s is t h a t n o c o n s i s t e n t l y s i g n i f i c a n t d i f f e r e n c e s in E M G b e t w e e n t e n s i o n h e a d a c h e p a t i e n t s a n d c o n t r o l s w e r e f o u n d - - d i f f e r e n c e s i n f o r e h e a d E M G o n l y r e a c h e d t h e 5 7o level o f s i g n i f i c a n c e in o n e o u t o f t h r e e s t u d i e s a n d likewise f o r n e c k E M G . In a d d i t i o n , t h e o n l y s t u d y to n o t find s i g n i f i c a n t d i f f e r e n c e s in E M G r e s t i n g levels w a s t h e o n e reported here which was also the only study to match headache patients and controls. T h e q u e s t i o n c l e a r l y a r i s e s as t o h o w m u c h t h e E M G d i f f e r e n c e s b e t w e e n g r o u p s t h a t h a v e b e e n r e p o r t e d w e r e d u e to f a c t o r s o t h e r t h a n t h e h e a d a c h e v a r i a b l e . F o r e x a m p l e , P h i l i p ' s c o n t r o l s u b j e c t s w e r e a s s e m b l e d f r o m h e r d e p a r t m e n t ( t h e y i n c l u d e d coll e a g u e s , s t u d e n t s a n d t e c h n i c i a n s ) a n d c o n s e q u e n t l y t e n d e d to b e y o u n g e r a n d m o r e familiar with the experimental environment than the headache patients. Both these
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factors could have c o n t r i b u t e d to the observed difference in forehead E M G between the groups (in the e x p e r i m e n t r e p o r t e d here a significant correlation o f 0.36 was f o u n d between f o r e h e a d E M G and age). Even in the study r e p o r t e d here it seems possible t h a t the E M G differences that were f o u n d could have arisen as a selectional artefact as the h e a d a c h e p a t i e n t s were referred by medical practitioners whilst the controls were staff o f an a d j o i n i n g hospital who agreed to participate. The findings f r o m this a n d B a k a l ' s study were even m o r e negative with respect to E M G response to stimuli. Hence, B a k a l ' s study d e m o n s t r a t e d no significant difference in E M G reactivity to noise stimuli a n d the present study showed t h a t the slight differences in E M G tend to reverse during presentation o f a 'stress" task. EXPERIMENT II Several experiments [6, 12-16] have been published in recent years in which some form o f relaxation training has been given as t r e a t m e n t for tension headaches, and the results can be s u m m a r i s e d as follows. E M G f e e d b a c k training has been d e m o n strated to be superior to a n o - t r e a t m e n t c o n t r o l c o n d i t i o n [6, 13], a p s e u d o - f e e d b a c k c o n d i t i o n [6, 15] a n d a m e d i c a t i o n - p l a c e b o c o n d i t i o n [14], in terms o f b o t h headache and E M G reduction. C o m p a r i s o n between E M G feedback training a n d relaxation instructions has sometimes indicated the f o r m e r to be m o r e effective [12] a n d sometimes t h a t they do n o t significantly differ [13, 14]. A l t h o u g h these t r e a t m e n t experiments involved repeated measures on the same individuals, thus providing the o p p o r t u n i t y for within subject analyses o f the relationship between muscle tension and headaches, few such analyses have been reported. One study [13] f o u n d subjects h a d significantly higher forehead E M G when experiencing a h e a d a c h e t h a n when headache-free and a n o t h e r [14] r e p o r t e d a correlation o f 0.42 between h e a d a c h e activity a n d forehead E M G . In contrast, a third study [16] l o o k e d at the c o n c o r d a n c e between changes in forehead E M G a n d h e a d a c h e reports over the three phases o f each treatm e n t session a n d f o u n d that similar changes in direction o f activity o f b o t h systems only occurred for one out o f six subjects. Even in the one exceptional case, relatively large-scale E M G changes were not reflected by similar changes in h e a d a c h e reports. The p u r p o s e o f the second experiment was to examine in greater detail the changes in E M G a n d reported headaches during t r e a t m e n t by E M G feedback, or by relaxation instruct ions. METHOD After completing experiment I, patients were asked to keep records of their headaches by rating their intensity hourly, and recording the ratings on cards (as in Budzynski et al. [6]). All patients whose HI ratings averaged at least 0.40 over the first two weeks of recording headaches were offered treatment aimed at reducing muscle tension. A sample of 24 subjects was collected in this way, of which four were male. Their average age was 36 years (range 16-62) and the average duration of headache problem was 10 years (range 1-30). The subjects were divided into two groups of 12 patients, one group receiving EMG feedback training and one receiving progressive relaxation training. A balance was maintained between the treatment groups by matching for age, sex, socio-economic status and duration of headache problem. All subjects attended for 14 weekly sessions, plus a follow-up session three months after treatment. During each session, patients sat in a comfortable armchair, whilst EMG was recorded from standard sites on the forehead and neck using a Devices M 19 polygraph (details as in earlier study). All sessions began and ended with subjects rating their HI. During three assessment sessions (Nos. 1, 14 and 15), all subjects were instructed to relax as best they could, but to keep their eyes open. They were told that the sessions would last approximately 30
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PAUL R. MARTIN and ANDREW M. MATFIEWS
minutes, and during this time they were welcome to make small movements except during three 65-second periods. The beginning of each period would be signalled by a low tone and the end of each period by a high tone. The periods would come at the beginning, middle and end of the sessions.
Feedback treatment Subjects in the EMG feedback group received feedback from the forehead in six sessions and from the neck in the other six, so that the efficacy of feedback from these two sites could be compared. Six subjects received feedback from the forehead followed by the neck, and six in the reverse order. Treatment sessions for subjects in the feedback group were divided into 21 trials each lasting 65 seconds, with 15-second intertrial intervals. As in the assessment sessions, each trial was announced by a low tone and terminated by a higher tone. A PDP-12 computer was programmed to produce feedback displays on the CRT scope, which were relayed via a camera to a TV screen in front of the subjects. The display during trial periods consisted of three short vertical lines intersecting a horizontal line. The length of the horizontal line varied (reset every 512 msec) in proportion to the E M G level recorded from the relevant site. The three vertical lines defined a linear scale with the leftmost line set at zero EMG, the centre line at the average EMG over the previous trial, and the rightmost line at twice this average level. Hence, the scale was reset from trial to trial providing a 'shaping' procedure. The display during intertrial intervals consisted of a number (correct to one decimal place) that indicated the average EMG in taV over the previous trial. Trial numbers 1, 11 and 21 were 'silent' (no display) in all treatment sessions, and more silent trials were introduced as treatment progressed. Patients were instructed to use the display to guide their efforts to reduce EMG levels on successive trials, the silent trials being explained as a way of helping them to maintain control under more normal conditions. Relaxation treatment Subjects in the progressive relaxation group listened to tape recordings of relaxation instructions based on those described by Jacobson [17]. The tapes in six treatment sessions concentrated on relaxing the forehead muscle, while the tapes in the other six treatment sessions concentrated on relaxing the neck muscles, to parallel the use of forehead and neck sites for the feedback group. Each tape lasted for 30 minutes and incorporated three 65-second periods, denoted by high and low tones, and situated at the beginning, middle and end of the sessions, during which subjects were asked to relax without making any movements. To parallel the introduction of more silent trials in the later treatment sessions of the feedback group, tapes for the equivalent treatment sessions of the relaxation group had blank sections during which subjects received no specific instructions, but were required to remain as relaxed as possible. Self-assessment All subjects were asked to continue rating their HI every hour, and to record these on the cards provided throughout the treatment period. They were also instructed to practise relaxation regularly at home, and to record the actual time spent each day, together with a note of any medications taken for their headaches. At the end of treatment, all subjects were asked to rate their improvement on a 9-point scale. They were asked to continue completing the record cards for seven days, and were subsequently sent cards for seven days at the one-month follow-up, and 14 days at the three-month follow-up. RESULTS Headache ratings Weekly headache activity scores were calculated by averaging all the HI ratings recorded in a week. As the distribution of these scores was positively skewed the scores were logarithmically transformed. Figure 3 shows a comparison between the treatment groups in terms of the transformed headache activity scores. These scores for the 15 consecutive weeks of the treatment period were analysed using a repeated measures analysis of variance with the following factors: groups (EMG feedback vs progressive relaxation); order (forehead-+neck vs neck-+forehead) and weeks. The main effect for Weeks was significant at the 1 ~ level, indicating that the headache activity scores of the patient group as a whole declined during the treatment period. The main effect for Groups and the interaction between Groups and Weeks fell well short of statistical significance, showing that the treatment groups did not significantly differ at any point during the treatment period. The interaction between Order and Weeks, and that between all three factors, failed to reach significance, demonstrating that whether training was directed at the forehead or neck muscles made no difference to the extent of reduction in headaches for either treatment group. The treatment groups were also compared at one-month and three-month follow-ups using analyses of covariance, the covariate in both analyses being the average headache activity over the two weeks
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EMG levels In all sessions (assessment and treatment) there were three 65-second periods during which subjects were instructed not to move, and received neither relaxation instructions nor E M G feedback. Consequently, E M G scores were calculated for each session by averaging forehead E M G and neck E M G over these three periods. As the distributions o f scores were again positively skewed, the scores were logarithmically transformed. Figure 4 shows the mean transformed E M G scores for each group throughout treatment. These scores were analysed using a repeated measure analysis o f variance as before, but with the additional factor o f periods within sessions. Unexpectedly there was no evidence o f a significantly overall reduction in E M G , or of any difference between the treatments. This lack o f difference due to treatments was confirmed by analysis o f covariance.
Correlational analysis To estimate the degree of response in each individual patient, linear regression equations were calculated for headache activity, forehead E M G and neck E M G on session number. The sample regression coefficients from these equations were used to test the null hypothesis that the population regression coefficient was equal to zero (i.e. whether or not a significant downward slope was present). Significant decreases in headache ratings were found for seven patients, but a signficant increasing trend occurred in one. In each o f the E M G measures, four patients showed significance decreases, but two had significant increases o f forehead E M G . Decreases in headaches or E M G were independent, since o f the seven subjects whose headaches significantly decreased, six showed no significant reduction in either forehead or neck E M G , and the one subject whose headaches increased showed a significant reduction in forehead E M G . F o r each subject, correlation coefficients were calculated between average HI rating and forehead or neck E M G from the same session. As testing showed no significant differences a m o n g any o f the sets o f individual correlations, the population coefficients were then estimated from each sample set using Fisher's corrected z transformation. The resulting correlation between headache intensity and forehead E M G was - 0 . 1 0 , and between headache intensity and neck E M G was 0-02. These extremely low and non-significant correlations between E M G and H I confirmed the lack of a
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FIG. 4.--Comparison of treatment groups in terms of forehead and neck EMG. linear relationship between them. An alternative hypothesis, that EMG merely had to reach a threshold level for a headache to occur, was assessed using a t-test for dependent groups. Only subjects who had experienced a headache throughout at least three sessions, and been headache-flee in another three, were included in this analysis. Mean neck EMG levels showed no significant difference between headache and headache-free sessions (t = 0-14, d.f. = 13). A difference significant at the 2 ~o level was found for forehead E M G (t = 2-60, d.f. = 13) but this unexpectedly indicated higher forehead EMG levels when headache-free than when experiencing a headache.
Prognostic factors Correlations were calculated between possible prognostic variables and four alternative measures of headache reduction. These four outcome measures were; self-rating of improvement at the end of treatment, the regression coefficient for headache activity during treatment, average headache level during the two weeks following treatment, and during an equivalent period at three month follow-up. For the last two outcome measures, the corresponding headache score before treatment was co-varied out, to eliminate the influence of starting level on outcome. The possible prognostic variables were forehead and neck E M G reduction (three each were calculated in identical fashion to the last three measures of headache reduction), duration of headache problem, age, and amount of time spent practising relaxation. None of the measures of headache reduction correlated significantly with any of the EMG measures, or time spent in relaxation practice. Hence, reduction of headache did not seem to be associated with reduction in forehead or neck muscle tension. Duration of headache problem and age correlated significantly with all three measures of headache reduction over the treatment period, but not with the measure of headache reduction at three month follow-up. The average correlation of headache reduction with duration of headache problem was 0.54, and with age was 0.46. Younger patients improved more than older patients, and patients with a shorter history of headache improved more than those with a longer history. The recorded information on medication taken for headaches was impossible to analyse statistically due to the wide range of drugs used. All subjects took some medication, the most commonly used classes being analgesics (n = 23), tranquillisers (n = 14), and anti-depressants (n = 8). Inspection of the records suggested that the consumption of drugs for both treatment groups was the same immediately after treatment as before treatment, although the EMG feedback group seemed to be taking fewer drugs at three month follow-up. Follow-up case studies if tension headaches are caused by excessive muscle tension, then it could be argued that the lack of
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treatment differences was due to the procedures failing to significantly lower EMG. To test this possibility, the first five patients who still had a significant headache problem at the three-month follow-up, and were willing to attend for more treatment, were given 12 sessions of more intensive EMG feedback training from the forehead muscle. Sessions were scheduled twice weekly, using a combination of auditory and visual feedback, and in the early sessions patients were given additional suggestions as to how they might relax more deeply (e.g. use of breathing exercises and imagery). They were also instructed to practise relaxation for 30 minutes each day at home and keep records as before. Individual data analysis was carried out as for the main experiment. Linear regression equations were calculated for headache activity, forehead EMG and neck EMG. These analyses revealed that three subjects who had failed to lower EMG in the main experiment, successfully lowered forehead EMG to a significant extent with the revised treatment programme. However, there was no significant decrease in headaches or medication usage for any of these subjects.
DISCUSSION Whilst the reported headache intensity of the whole patient group decreased over the treatment period, the effect was a small one and seemed less than those reported in comparable studies. This m a y have occurred because different methods were used for collecting subjects in other studies. The study reported here involved patients referred by medical practitioners, whilst those conducted in the U.S.A. used subjects collected by advertising [6, 12-14], and the other British study [15] involved the selection of some subjects by questionnaire given to patients on a general practitioner's list. The larger decreases in headache activity reported in the American studies could have been due to differences between referred patients and subjects recruited by newspaper advertisements in terms of severity, intelligence, suggestibility or motivation. There was no evidence in any o f the analyses to support the widely-held belief that tension headaches are caused by excessive tension in the muscles o f the forehead or neck. Within subject analyses revealed no relationship between neck E M G and headaches, whilst forehead E M G was if anything lower during a headache than in headache-free sessions. Although reported headaches decreased, there was no parallel reduction in E M G , and no associations between the extent of individual improvement and E M G changes. In those patients given additional treatment, E M G fell more, but headaches were not reduced. CONCLUSIONS The results o f both experiments consistently suggest that excessive muscle activity plays little or no part in the aetiology of chronic headaches. This view raises two main questions--if elevated muscle tension does not cause tension headaches then what does; and why should feedback or relaxation training benefit some headache patients ? In experiment I inhaling a vasodilator was found to make tension headaches worse on 4 3 ~ of occasions, suggesting tension headaches are associated with cranial vasodilation. As migraine headaches are thought to be associated with cranial vasodilation [18] this data suggests that these types o f headaches may not be as distinct as the A M A headache classification [19] implies--the difference may be largely in terms of severity rather than physiological mechanism. Tension headaches and migraines are certainly difficult to differentiate in terms of symptomatology, and it is c o m m o n to find both sets o f symptoms occurring in the same patient on different occasions. Bakal emphasised in his paper [8] that in the few studies that have compared migraine and tension headache patients, the differences found have been quantitative rather than
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PAI~L R. MARTINand ANDRFWM. MATHEWS
qualitative. Viewed fiom this perspective, the finding in experiment lI that tension headache patients had significantly lower forehead E M G d u r i n g headaches t h a n when headache-free is more understandable. The A M A classification refers to p o p u l a r names for ' c o m m o n migraines' as 'relaxation' headaches a n d 'weekend' headaches, implying that some patients experience migraine headaches when they relax rather t h a n when they become tense. With respect to the question of how relaxation training can help tension headache patients, one possibility would seem to be non-specific or 'placebo' effects. Attempts have been made to control for placebo effects b u t the procedures used have not been entirely satisfactory. Hence, pseudo-feedback (recording of successful E M G feedback sessions played to patients who were told it was a m o n o t o n o u s tone that would help them relax), and medication placebo (patients given a glucose capsule which they were told would help them relax)-- seem unlikely to have raised expectations to the same level as E M G feedback or relaxation instructions. A n o t h e r possibility is that the relaxation training procedures have a specific physiological action, but it may be mediated via the vascular rather t h a n the muscular system. F o r example, if the m e c h a n i s m of tension headaches and migraines is a function of cerebral vascular response to stressful stimuli, the action of relaxation training could be to reduce such reactivity. Clearly more research is needed to u n d e r s t a n d the aetiology of headaches. As the study of headache symptoms [20, 21] has produced little support for i n d e p e n d e n t tension headache a n d migraine syndromes, the selection of suitable subjects lk)r research in this area will need careful attention. REFERENCES 1. TlrNISM. M. and WOLFFH. G. Studies on headache: Cranial artery vasoconstriction and muscle contraction headache. Archs Neurol. Psyehiat. 71, 425434 (1954). 2. OSTFELDA. M., REIS D. J. and WOLFFH. G. Studies in headache: Bulbar conjunctival ischemia and muscle contraction headache. Archs Neurol. Psychiat. 77, 113-119 (1957). 3. ONFL Y., FRIEDMANA. P. and GROSSMANJ. Muscle blood flow studies in muscle-contraction headaches. Neurology 11,935-939 (1961). 4. SAINS~URYP. and GIBSONJ. F. Symptorns of anxiety and tension anti accompanying physiological changes in the muscular system. J. Neurol. Neurosurg. Psychiat. 17, 216 224 (1954). 5. MALMOR. B., WALLERSTEIN H. and SHAGASSC. Headache proneness and mechanisms of motor conflict in psychiatric patients. J. Person. 22, 163-187 (1953). 6. BUDZYNSKIT. H., STOYVAJ. M., ADLERC. S. and MULLANEYD. J. EMG biofeedback and tension headaches: a controlled outcome study. Psyehosom. Med. 35, 484-496 (1973). 7. PHILIPS C. A psychological analysis of tension headache. In Advances in Medical Psychology (Edited by RACHMANS.). Pergamon Press, Oxford (1977). 8. BAKALD. A. and KAGANOVJ. A. Muscle contraction and migraine headache: a psychophysiological comparison, tfeadache 17, 208--215 (1977). 9. LIPPOLD O. C. J. Electromyography. In Manual o f Psychophysiological MethocLv (Edited by VENABLESP. H. and MARTIN1.), pp. 245-297. North Holland, Amsterdam (1967). 10. HARDYJ. D., WOLFFH. G. and GOODELLH. Studies in pain: A new method for measuring pain threshold: observations of spatial summation of pain. J. Clin. Invest. 19, 649-657 (1940). l [. FURNEAUXW. D. ~4anual o[Nuff?rno Level Tests. National Foundation for Educational Research, London (I 950). 12. HUTCHINGSD. F. and REINKINGR. H. Tension headaches: what form of therapy is most effective? BioJ~,ed. Serf:Reg. l, 183-190 (1976). 13. HAYNES S. N., GRIFFIN P., MOONEY D. and PARISE M. Electromyographic biofeedback and relaxation instructions in the treatment of muscle contraction headaches. Behc¢. Ther. 6, 672-678
(1975).
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14. Cox D. J., FREUNDLICH A. and MEYER R. G. Differential effectiveness of electromyograph feedback, verbal relaxation instructions, and medication placebo with tension headaches. J. Consult. Clin. Psychol. 43, 892-898 (1975). 15. PHILIPS C. The modification of tension headache pain using E M G biofeedback. Behav. Res. Therap. 14, 119-129 (1977). 16. EPSTEIN L. H. and ABEL G. G. An analysis of biofeedback training effects for tension headache patients. Behav. Ther. 8, 37~1-7 (1977). 17. JACOSSON E. Progressive Relaxation. University of Chicago Press, Chicago, Ill. 0938). 18. DALESSIO D. J. Wo[ff's Headache and Other Head Pain. Oxford University Press, New York (1972). 19. Ad hoc Committee on Classification of Headache. Classification of headache. J. Am. Med. Ass. 179, 717-718 (1962). 20. ZIGGLER D. K., HASSANEIN R. and HASSANEIN K. Headache syndromes suggested by factor analysis of symptom variables in a headache prone population. J. Chron. Dis. 25, 335-365 0972). 21. WATERSW. E. The epidemiological enigma of migraine. Int. J. Epidem. 7, 189-195 (1977).
TENSION HEADACHES: PSYCHOPHYSIOLOGICAL INVESTIGATION AND T R E A T M E N T PAUL R. MARTIN* a n d ANDREW M. MATHEWS'~
(Received 10 May 1978) Abstract--Two experiments investigating the aetiology of chronic tension headaches are reported. The first compared neck and forehead EMG of tension headache patients with that of non-headache control subjects whilst at rest and whilst performing a stressful task. The two groups were also compared in terms of pain threshold, and the effect of a vasodilating agent on headache intensity was assessed. In general, EMG levels were similar in the two groups and there were few clearly significant differences. The forehead EMG of the headache patients was marginally higher than that of the control subjects when at rest, but this trend was reversed under stress. In the second experiment, tension headache patients received either EMG feedback training or progressive relaxation training. Results showed the two treatment conditions to be equally effective for reducing recorded headache activity. Headache reduction was not related to success at lowering forehead or neck EMG in the laboratory. Within subject correlations between forehead or neck EMG, and headache intensity at the time of EMG recording, failed to reach significance. Comparing subjects when experiencing headaches and when headache-free revealed no difference in neck EMG, but significantly lower forehead EMG during headaches. The results were interpreted as failing to support the widely-held belief that chronic tension headaches are primarily caused by excessive tension in the skeletal muscles of the head or neck. EXPERIMENT 1 EXPERIMENTS investigating the aetiology o f tension headaches have c o n c e n t r a t e d on two variables, electrical activity ( E M G ) in the head a n d neck muscles, a n d cerebral b l o o d flow. Papers r e p o r t i n g on the latter variable have p r o d u c e d conflicting results - two studies have suggested tension headaches are associated with cranial vasoconstriction [1, 2], whilst a larger study has suggested they are associated with cranial v a s o d i l a t i o n [3]. A n u m b e r o f early studies [1, 4, 5] have p r o d u c e d d a t a suggesting tension headaches are associated with elevated tension in skeletal muscle, b u t they are all open to m a j o r criticisms. The hypothesis t h a t ' t e n s i o n ' headaches are the result o f excessive skeletal muscle activity has been the object o f renewed interest following evidence t h a t training to reduce E M G levels c a n decrease r e p o r t e d h e a d a c h e pain [6]. Hence Philips [7] has recently investigated the muscle tension levels o f h e a d a c h e patients by c o m p a r i n g n o n - h e a d a c h e c o n t r o l subjects with patients suffering from tension headaches, migraines and m i x e d m i g r a i n e - t e n s i o n headaches. E M G was m o n i t o r e d during headache-free episodes f r o m the frontalis, temporalis, neck a n d trapezius muscles over four-minute rest periods. Analysis o f variance showed significant differences only with frontalis E M G ; the o r d e r o f the groups being control, tension, mixed, migraine, with the last g r o u p having the highest level. A l t h o u g h the difference between the tension a n d control groups reached significance (p <0.05), the difference between the tension a n d migraine groups did not. Bakal a n d K a g a n o v [8] c o m p a r e d tension h e a d a c h e a n d migraine patients with headache-free controls in terms o f E M G (forehead and neck) and vascular activity (pulse flow velocity from *Research Clinical Psychologist, Oxford Rehabilitation Research Unit, Nuftield Orthopaedic Centre, Oxford OX3 7LD, England. tProfessor of Psychology, St. George's Hospital Medical School, London SW17, England. 389
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PAUL R. MARTIN and ANDREW M. MATftEWS
s u p e r f i c i a l t e m p o r a l a r t e r i e s ) . H e a d a c h e p a t i e n t s a t t e n d e d f o r o n e session w i t h a s e v e r e headache and for another without a headache, but presence or absence of headache d i d n o t s i g n i f i c a n t l y affect t h e m e a s u r e s used. M i g r a i n e p a t i e n t s w e r e f o u n d t o h a v e significantly higher forehead EMG than tension headache patients, who had almost i d e n t i c a l f o r e h e a d E M G levels to t h e c o n t r o l ' s b u t s i g n i f i c a n t l y h i g h e r n e c k E M G . Pulse velocity responses obtained from the patients (tension headache and migraine) decreased in response to noise stimuli, supposedly indicating vasoconstriction, while p u l s e v e l o c i t y r e s p o n s e s o f t h e c o n t r o l s i n c r e a s e d to t h e s a m e s t i m u l i , i n d i c a t i n g vasodilation. The differences, however, were only significant for one of the velocity measures. T h e p u r p o s e o f t h e first e x p e r i m e n t w a s to i n v e s t i g a t e q u e s t i o n s a r i s i n g f r o m h y p o t h e s e s a b o u t t h e a e t i o l o g y o f t e n s i o n h e a d a c h e s ; specifically w h e t h e r r e s t i n g E M G levels w e r e h i g h e r t h a n in c l o s e l y m a t c h e d c o n t r o l s u b j e c t s ; w h e t h e r stress p r o d u c e d a d i s p r o p o r t i o n a t e i n c r e a s e o r s l o w e r r e c o v e r y in E M G ; w h e t h e r p a t i e n t s were more sensitive to head pain; and whether headaches responded to a vasodilating agent. METHOD General practitioners and neurologists in the area were asked to refer patients who had suffered from tension headaches frequently (one or more a week) for at least a year. Such patients were seen by one of two medical assessors who assigned them to one of three categories- 'primary muscle tension', 'combined muscle tension and other pathology', or 'other types of headache' and rated the diagnosis as possible, quite likely or very likely. No fixed diagnostic criteria were adopted, as in the absence of a generally agreed method of classification it was thought more appropriate to collect a representative sample of patients agreed by two clinicians to be suffering from tension headaches. Out of 50 patients referred, 13 were excluded as not being so diagnosed by the medical assessor, leaving a sample of 37 patients. The average age of these patients was 36 years (range 16-62), the average duration of headache problem was 12 years (range 1-46), and 7 of the patients were male. A nonheadache control group was assembled from the staff of an adjoining hospital, and subjects in the two groups were individually matched for age, sex and socio-economic status. None of the controls were well known to the experimenter, and none had previously participated in psychophysiological research projects. All subjects attended a single laboratory session during which E M G from the forehead and neck was monitored throughout. Standard positions were used for electrode attachment [9], and E M G activity was amplified and filtered (frequency range 30-1000 Hz) with a Devices M I 9 polygraph. A PDP-12 computer sampled from each of the E M G sites every millisecond providing the raw data for subsequent analysis. Sessions were held in a temperature-controlled (22°C), sound-attenuated laboratory, and subjects sat in a comfortable armchair with a high back. Electrode sites were marked using a template, and after skin preparation, gold-plated disc electrodes were attached with elastoplast. Electrode resistance was checked to ensure that it was below 10kQ. The experiment then preceded in four phases, in the first phase, lasting ten minutes, subjects were simply told to sit back and relax with eyes closed. In the second phase, pain thresholds were measured using a graded series cf thermal stimuli from a light focussed onto the forehead [10]. Successively more intense heat stimuli were presented at one-minute intervals until reported to be 'slightly painful'. The reliability of threshold measurement was estimated as 0.78 (p < 0.001, n = 12) from another sample of subjects retested after an interval of four months. The third phase was a stress condition which consisted of presentation of 24 problems from the Nufferno Level Intelligence Test [11] using a carousal slide projector. These problems consisted of series of letters and subjects were required to work out the next letter in the series within 20 seconds. Subjects were told whether their solution was correct, or if at the end of the time limit no solution was offered, they were given the correct solution before presentation of the next problem. The level of difficulty of the problems, and the time interval used, were selected so that only a proportion of the problems could be solved within the time limit. The fourth phase lasted 10 minutes and was similar to the first in that instructions were given to relax with eyes closed for 10 minutes. At the beginning and end of each phase, subjects were asked to rate their headache intensity (HI) on
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the six-point scale devised by Budzynski [6]. Those patients who gave a rating of greater than zero at the end of the fourth phase were asked to inhale a vasodilator (amyl nitrite), and a matching placebo (pabrinex), separated by a five-minute interval. Order of administration was balanced across patients, and they were asked to rate their HI immediately before and after inhaling each drug to assess any effects. ANALYSIS The EMG data was initially analysed using an analysis of variance suitable for repeated measures. The data included in the analysis derived from three 6-minute periods--the final 6 minutes of the initial relaxation period, the first 6 minutes of the stress task (6 minutes being the minimum time taken to complete the stress task), and the first 6 minutes of the post-stress relaxation period. Each 6-minute period was divided into twelve 30-second trials, and average scores were calculated for each trial. A logarithmic transformation was applied to the EMG data prior to analysis as the raw distributions were positively skewed, and mean levels of this variable are plotted graphically as Figs. 1 and 2. The main factors included in the subsequent analysis were: groups (headache patients vs controls); occasions (initial relaxation vs stress task vs post-stress relaxation); EMG (forehead vs neck) and trials. 1.3
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RESULTS The main effect for groups fell well short of statistical significance, but two interactions involving the groups factor reached the 5 % level of significance--groups x occasions (p < 0"01) and groups
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PALL P,. I~IAR'IIN a n d ANDP, I\V ]M. MATIIEV~S
>: trials (p < 0.05). The former interaction indicated that the headache patients tended to ha~e higher E M G during the relaxation conditions but lower E M G during the stress condition, while the latter interaction reflected the slight tendency for controls (but not patients) to show EMG increases within some 6-minute periods. When analyses of variance were calculated for each E M G site and each occasion separately, the main effect for groups failed to reach the 5 ~ level of significance for any of the six analyses. Hence the headache patients did not significantly differ from the controls in tcrms of forchead or neck E M G for any single condition of relaxation or stress taken on its own. The data were then re-analysed after splitting the headache patients and their corresponding controls into three groups, according to whether patients were headache-free, experienced a slight headache (rated between zero and two), or experienced a moderate to severe headache (rated as equal to or greater than two) during the session. The pattern of results in each of the three analyses was essentially the same, so that even patients experiencing moderate to severe headaches did not have significantly higher forehead or neck EMG than controls. The data were also re-analysed comparing those patients whom the medical assessor had considered to be the most unambiguous tension headache cases (diagnosed as 'primary muscle tension; very likely'), with those with more mixed symptomatology. In none of thcse analyses werc there any difference in E M G between groups, suggesting that the original findings were not distorted by inclusion of diagnostically inappropriate patients. The average pain threshold for the headache patient group was unexpectedly higher than for the control group, but a t-test for dependent groups showed that the difference was not statistically' significant (t = 1.07, d.f. = 36). A correlation was calculated for the headache patients between pain threshold and the average of the HI ratings before and after threshold measurement. As this correlation was also not significant (r = 0"13) there does not appear to be any cvidence that complaints of headache are attributable to greater sensitivity to pain. Twenty-three patients were given drugs following the post-stress relaxation period, and the results are presented in Table 1. The table shows that inhaling the vasodilator led to an increase in headache severity on 43 ~ of occasions and no change on 48 ~ of occasions. The large percentage reporting an increase in headache severity cannot be attributed to factors such as demand characteristics, since no increases were reported after inhaling the placebo and this difference was highly significant (p < 0.001 ) by Z2 test. Hence, these results suggest that pain is associated with cranial vasodilation rather than vasoconstriction, at least in those patients already experiencing a headache. TABLE I.--HEADACHE RESPONSE TO DRUG ADMINISTRATION
Amyl nitrite Placebo
Better I 2
No change 12 2!
Worse 10 0
DISCUSSION T h e E M G d a t a p r e s e n t e d h e r e is m o r e s i m i l a r to P h i l i p ' s d a t a t h a n B a k a l ' s d a t a in f i n d i n g t e n s i o n h e a d a c h e p a t i e n t s t e n d t o differ f r o m n o n - h e a d a c h e c o n t r o l s ill t e r m s of forehead rather than neck EMG (during the post-stress relaxation period the d i f f e r e n c e in f o r e h e a d E M G w a s s i g n i f i c a n t at t h e 6 o4 level). H o w e v e r , t h e m o s t s t r i k i n g a s p e c t o f t h e d a t a f r o m t h e s e t h r e e s t u d i e s is t h a t n o c o n s i s t e n t l y s i g n i f i c a n t d i f f e r e n c e s in E M G b e t w e e n t e n s i o n h e a d a c h e p a t i e n t s a n d c o n t r o l s w e r e f o u n d - - d i f f e r e n c e s i n f o r e h e a d E M G o n l y r e a c h e d t h e 5 7o level o f s i g n i f i c a n c e in o n e o u t o f t h r e e s t u d i e s a n d likewise f o r n e c k E M G . In a d d i t i o n , t h e o n l y s t u d y to n o t find s i g n i f i c a n t d i f f e r e n c e s in E M G r e s t i n g levels w a s t h e o n e reported here which was also the only study to match headache patients and controls. T h e q u e s t i o n c l e a r l y a r i s e s as t o h o w m u c h t h e E M G d i f f e r e n c e s b e t w e e n g r o u p s t h a t h a v e b e e n r e p o r t e d w e r e d u e to f a c t o r s o t h e r t h a n t h e h e a d a c h e v a r i a b l e . F o r e x a m p l e , P h i l i p ' s c o n t r o l s u b j e c t s w e r e a s s e m b l e d f r o m h e r d e p a r t m e n t ( t h e y i n c l u d e d coll e a g u e s , s t u d e n t s a n d t e c h n i c i a n s ) a n d c o n s e q u e n t l y t e n d e d to b e y o u n g e r a n d m o r e familiar with the experimental environment than the headache patients. Both these
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factors could have c o n t r i b u t e d to the observed difference in forehead E M G between the groups (in the e x p e r i m e n t r e p o r t e d here a significant correlation o f 0.36 was f o u n d between f o r e h e a d E M G and age). Even in the study r e p o r t e d here it seems possible t h a t the E M G differences that were f o u n d could have arisen as a selectional artefact as the h e a d a c h e p a t i e n t s were referred by medical practitioners whilst the controls were staff o f an a d j o i n i n g hospital who agreed to participate. The findings f r o m this a n d B a k a l ' s study were even m o r e negative with respect to E M G response to stimuli. Hence, B a k a l ' s study d e m o n s t r a t e d no significant difference in E M G reactivity to noise stimuli a n d the present study showed t h a t the slight differences in E M G tend to reverse during presentation o f a 'stress" task. EXPERIMENT II Several experiments [6, 12-16] have been published in recent years in which some form o f relaxation training has been given as t r e a t m e n t for tension headaches, and the results can be s u m m a r i s e d as follows. E M G f e e d b a c k training has been d e m o n strated to be superior to a n o - t r e a t m e n t c o n t r o l c o n d i t i o n [6, 13], a p s e u d o - f e e d b a c k c o n d i t i o n [6, 15] a n d a m e d i c a t i o n - p l a c e b o c o n d i t i o n [14], in terms o f b o t h headache and E M G reduction. C o m p a r i s o n between E M G feedback training a n d relaxation instructions has sometimes indicated the f o r m e r to be m o r e effective [12] a n d sometimes t h a t they do n o t significantly differ [13, 14]. A l t h o u g h these t r e a t m e n t experiments involved repeated measures on the same individuals, thus providing the o p p o r t u n i t y for within subject analyses o f the relationship between muscle tension and headaches, few such analyses have been reported. One study [13] f o u n d subjects h a d significantly higher forehead E M G when experiencing a h e a d a c h e t h a n when headache-free and a n o t h e r [14] r e p o r t e d a correlation o f 0.42 between h e a d a c h e activity a n d forehead E M G . In contrast, a third study [16] l o o k e d at the c o n c o r d a n c e between changes in forehead E M G a n d h e a d a c h e reports over the three phases o f each treatm e n t session a n d f o u n d that similar changes in direction o f activity o f b o t h systems only occurred for one out o f six subjects. Even in the one exceptional case, relatively large-scale E M G changes were not reflected by similar changes in h e a d a c h e reports. The p u r p o s e o f the second experiment was to examine in greater detail the changes in E M G a n d reported headaches during t r e a t m e n t by E M G feedback, or by relaxation instruct ions. METHOD After completing experiment I, patients were asked to keep records of their headaches by rating their intensity hourly, and recording the ratings on cards (as in Budzynski et al. [6]). All patients whose HI ratings averaged at least 0.40 over the first two weeks of recording headaches were offered treatment aimed at reducing muscle tension. A sample of 24 subjects was collected in this way, of which four were male. Their average age was 36 years (range 16-62) and the average duration of headache problem was 10 years (range 1-30). The subjects were divided into two groups of 12 patients, one group receiving EMG feedback training and one receiving progressive relaxation training. A balance was maintained between the treatment groups by matching for age, sex, socio-economic status and duration of headache problem. All subjects attended for 14 weekly sessions, plus a follow-up session three months after treatment. During each session, patients sat in a comfortable armchair, whilst EMG was recorded from standard sites on the forehead and neck using a Devices M 19 polygraph (details as in earlier study). All sessions began and ended with subjects rating their HI. During three assessment sessions (Nos. 1, 14 and 15), all subjects were instructed to relax as best they could, but to keep their eyes open. They were told that the sessions would last approximately 30
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PAUL R. MARTIN and ANDREW M. MATFIEWS
minutes, and during this time they were welcome to make small movements except during three 65-second periods. The beginning of each period would be signalled by a low tone and the end of each period by a high tone. The periods would come at the beginning, middle and end of the sessions.
Feedback treatment Subjects in the EMG feedback group received feedback from the forehead in six sessions and from the neck in the other six, so that the efficacy of feedback from these two sites could be compared. Six subjects received feedback from the forehead followed by the neck, and six in the reverse order. Treatment sessions for subjects in the feedback group were divided into 21 trials each lasting 65 seconds, with 15-second intertrial intervals. As in the assessment sessions, each trial was announced by a low tone and terminated by a higher tone. A PDP-12 computer was programmed to produce feedback displays on the CRT scope, which were relayed via a camera to a TV screen in front of the subjects. The display during trial periods consisted of three short vertical lines intersecting a horizontal line. The length of the horizontal line varied (reset every 512 msec) in proportion to the E M G level recorded from the relevant site. The three vertical lines defined a linear scale with the leftmost line set at zero EMG, the centre line at the average EMG over the previous trial, and the rightmost line at twice this average level. Hence, the scale was reset from trial to trial providing a 'shaping' procedure. The display during intertrial intervals consisted of a number (correct to one decimal place) that indicated the average EMG in taV over the previous trial. Trial numbers 1, 11 and 21 were 'silent' (no display) in all treatment sessions, and more silent trials were introduced as treatment progressed. Patients were instructed to use the display to guide their efforts to reduce EMG levels on successive trials, the silent trials being explained as a way of helping them to maintain control under more normal conditions. Relaxation treatment Subjects in the progressive relaxation group listened to tape recordings of relaxation instructions based on those described by Jacobson [17]. The tapes in six treatment sessions concentrated on relaxing the forehead muscle, while the tapes in the other six treatment sessions concentrated on relaxing the neck muscles, to parallel the use of forehead and neck sites for the feedback group. Each tape lasted for 30 minutes and incorporated three 65-second periods, denoted by high and low tones, and situated at the beginning, middle and end of the sessions, during which subjects were asked to relax without making any movements. To parallel the introduction of more silent trials in the later treatment sessions of the feedback group, tapes for the equivalent treatment sessions of the relaxation group had blank sections during which subjects received no specific instructions, but were required to remain as relaxed as possible. Self-assessment All subjects were asked to continue rating their HI every hour, and to record these on the cards provided throughout the treatment period. They were also instructed to practise relaxation regularly at home, and to record the actual time spent each day, together with a note of any medications taken for their headaches. At the end of treatment, all subjects were asked to rate their improvement on a 9-point scale. They were asked to continue completing the record cards for seven days, and were subsequently sent cards for seven days at the one-month follow-up, and 14 days at the three-month follow-up. RESULTS Headache ratings Weekly headache activity scores were calculated by averaging all the HI ratings recorded in a week. As the distribution of these scores was positively skewed the scores were logarithmically transformed. Figure 3 shows a comparison between the treatment groups in terms of the transformed headache activity scores. These scores for the 15 consecutive weeks of the treatment period were analysed using a repeated measures analysis of variance with the following factors: groups (EMG feedback vs progressive relaxation); order (forehead-+neck vs neck-+forehead) and weeks. The main effect for Weeks was significant at the 1 ~ level, indicating that the headache activity scores of the patient group as a whole declined during the treatment period. The main effect for Groups and the interaction between Groups and Weeks fell well short of statistical significance, showing that the treatment groups did not significantly differ at any point during the treatment period. The interaction between Order and Weeks, and that between all three factors, failed to reach significance, demonstrating that whether training was directed at the forehead or neck muscles made no difference to the extent of reduction in headaches for either treatment group. The treatment groups were also compared at one-month and three-month follow-ups using analyses of covariance, the covariate in both analyses being the average headache activity over the two weeks
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EMG levels In all sessions (assessment and treatment) there were three 65-second periods during which subjects were instructed not to move, and received neither relaxation instructions nor E M G feedback. Consequently, E M G scores were calculated for each session by averaging forehead E M G and neck E M G over these three periods. As the distributions o f scores were again positively skewed, the scores were logarithmically transformed. Figure 4 shows the mean transformed E M G scores for each group throughout treatment. These scores were analysed using a repeated measure analysis o f variance as before, but with the additional factor o f periods within sessions. Unexpectedly there was no evidence o f a significantly overall reduction in E M G , or of any difference between the treatments. This lack o f difference due to treatments was confirmed by analysis o f covariance.
Correlational analysis To estimate the degree of response in each individual patient, linear regression equations were calculated for headache activity, forehead E M G and neck E M G on session number. The sample regression coefficients from these equations were used to test the null hypothesis that the population regression coefficient was equal to zero (i.e. whether or not a significant downward slope was present). Significant decreases in headache ratings were found for seven patients, but a signficant increasing trend occurred in one. In each o f the E M G measures, four patients showed significance decreases, but two had significant increases o f forehead E M G . Decreases in headaches or E M G were independent, since o f the seven subjects whose headaches significantly decreased, six showed no significant reduction in either forehead or neck E M G , and the one subject whose headaches increased showed a significant reduction in forehead E M G . F o r each subject, correlation coefficients were calculated between average HI rating and forehead or neck E M G from the same session. As testing showed no significant differences a m o n g any o f the sets o f individual correlations, the population coefficients were then estimated from each sample set using Fisher's corrected z transformation. The resulting correlation between headache intensity and forehead E M G was - 0 . 1 0 , and between headache intensity and neck E M G was 0-02. These extremely low and non-significant correlations between E M G and H I confirmed the lack of a
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FIG. 4.--Comparison of treatment groups in terms of forehead and neck EMG. linear relationship between them. An alternative hypothesis, that EMG merely had to reach a threshold level for a headache to occur, was assessed using a t-test for dependent groups. Only subjects who had experienced a headache throughout at least three sessions, and been headache-flee in another three, were included in this analysis. Mean neck EMG levels showed no significant difference between headache and headache-free sessions (t = 0-14, d.f. = 13). A difference significant at the 2 ~o level was found for forehead E M G (t = 2-60, d.f. = 13) but this unexpectedly indicated higher forehead EMG levels when headache-free than when experiencing a headache.
Prognostic factors Correlations were calculated between possible prognostic variables and four alternative measures of headache reduction. These four outcome measures were; self-rating of improvement at the end of treatment, the regression coefficient for headache activity during treatment, average headache level during the two weeks following treatment, and during an equivalent period at three month follow-up. For the last two outcome measures, the corresponding headache score before treatment was co-varied out, to eliminate the influence of starting level on outcome. The possible prognostic variables were forehead and neck E M G reduction (three each were calculated in identical fashion to the last three measures of headache reduction), duration of headache problem, age, and amount of time spent practising relaxation. None of the measures of headache reduction correlated significantly with any of the EMG measures, or time spent in relaxation practice. Hence, reduction of headache did not seem to be associated with reduction in forehead or neck muscle tension. Duration of headache problem and age correlated significantly with all three measures of headache reduction over the treatment period, but not with the measure of headache reduction at three month follow-up. The average correlation of headache reduction with duration of headache problem was 0.54, and with age was 0.46. Younger patients improved more than older patients, and patients with a shorter history of headache improved more than those with a longer history. The recorded information on medication taken for headaches was impossible to analyse statistically due to the wide range of drugs used. All subjects took some medication, the most commonly used classes being analgesics (n = 23), tranquillisers (n = 14), and anti-depressants (n = 8). Inspection of the records suggested that the consumption of drugs for both treatment groups was the same immediately after treatment as before treatment, although the EMG feedback group seemed to be taking fewer drugs at three month follow-up. Follow-up case studies if tension headaches are caused by excessive muscle tension, then it could be argued that the lack of
Tension headaches
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treatment differences was due to the procedures failing to significantly lower EMG. To test this possibility, the first five patients who still had a significant headache problem at the three-month follow-up, and were willing to attend for more treatment, were given 12 sessions of more intensive EMG feedback training from the forehead muscle. Sessions were scheduled twice weekly, using a combination of auditory and visual feedback, and in the early sessions patients were given additional suggestions as to how they might relax more deeply (e.g. use of breathing exercises and imagery). They were also instructed to practise relaxation for 30 minutes each day at home and keep records as before. Individual data analysis was carried out as for the main experiment. Linear regression equations were calculated for headache activity, forehead EMG and neck EMG. These analyses revealed that three subjects who had failed to lower EMG in the main experiment, successfully lowered forehead EMG to a significant extent with the revised treatment programme. However, there was no significant decrease in headaches or medication usage for any of these subjects.
DISCUSSION Whilst the reported headache intensity of the whole patient group decreased over the treatment period, the effect was a small one and seemed less than those reported in comparable studies. This m a y have occurred because different methods were used for collecting subjects in other studies. The study reported here involved patients referred by medical practitioners, whilst those conducted in the U.S.A. used subjects collected by advertising [6, 12-14], and the other British study [15] involved the selection of some subjects by questionnaire given to patients on a general practitioner's list. The larger decreases in headache activity reported in the American studies could have been due to differences between referred patients and subjects recruited by newspaper advertisements in terms of severity, intelligence, suggestibility or motivation. There was no evidence in any o f the analyses to support the widely-held belief that tension headaches are caused by excessive tension in the muscles o f the forehead or neck. Within subject analyses revealed no relationship between neck E M G and headaches, whilst forehead E M G was if anything lower during a headache than in headache-free sessions. Although reported headaches decreased, there was no parallel reduction in E M G , and no associations between the extent of individual improvement and E M G changes. In those patients given additional treatment, E M G fell more, but headaches were not reduced. CONCLUSIONS The results o f both experiments consistently suggest that excessive muscle activity plays little or no part in the aetiology of chronic headaches. This view raises two main questions--if elevated muscle tension does not cause tension headaches then what does; and why should feedback or relaxation training benefit some headache patients ? In experiment I inhaling a vasodilator was found to make tension headaches worse on 4 3 ~ of occasions, suggesting tension headaches are associated with cranial vasodilation. As migraine headaches are thought to be associated with cranial vasodilation [18] this data suggests that these types o f headaches may not be as distinct as the A M A headache classification [19] implies--the difference may be largely in terms of severity rather than physiological mechanism. Tension headaches and migraines are certainly difficult to differentiate in terms of symptomatology, and it is c o m m o n to find both sets o f symptoms occurring in the same patient on different occasions. Bakal emphasised in his paper [8] that in the few studies that have compared migraine and tension headache patients, the differences found have been quantitative rather than
398
PAI~L R. MARTINand ANDRFWM. MATHEWS
qualitative. Viewed fiom this perspective, the finding in experiment lI that tension headache patients had significantly lower forehead E M G d u r i n g headaches t h a n when headache-free is more understandable. The A M A classification refers to p o p u l a r names for ' c o m m o n migraines' as 'relaxation' headaches a n d 'weekend' headaches, implying that some patients experience migraine headaches when they relax rather t h a n when they become tense. With respect to the question of how relaxation training can help tension headache patients, one possibility would seem to be non-specific or 'placebo' effects. Attempts have been made to control for placebo effects b u t the procedures used have not been entirely satisfactory. Hence, pseudo-feedback (recording of successful E M G feedback sessions played to patients who were told it was a m o n o t o n o u s tone that would help them relax), and medication placebo (patients given a glucose capsule which they were told would help them relax)-- seem unlikely to have raised expectations to the same level as E M G feedback or relaxation instructions. A n o t h e r possibility is that the relaxation training procedures have a specific physiological action, but it may be mediated via the vascular rather t h a n the muscular system. F o r example, if the m e c h a n i s m of tension headaches and migraines is a function of cerebral vascular response to stressful stimuli, the action of relaxation training could be to reduce such reactivity. Clearly more research is needed to u n d e r s t a n d the aetiology of headaches. As the study of headache symptoms [20, 21] has produced little support for i n d e p e n d e n t tension headache a n d migraine syndromes, the selection of suitable subjects lk)r research in this area will need careful attention. REFERENCES 1. TlrNISM. M. and WOLFFH. G. Studies on headache: Cranial artery vasoconstriction and muscle contraction headache. Archs Neurol. Psyehiat. 71, 425434 (1954). 2. OSTFELDA. M., REIS D. J. and WOLFFH. G. Studies in headache: Bulbar conjunctival ischemia and muscle contraction headache. Archs Neurol. Psychiat. 77, 113-119 (1957). 3. ONFL Y., FRIEDMANA. P. and GROSSMANJ. Muscle blood flow studies in muscle-contraction headaches. Neurology 11,935-939 (1961). 4. SAINS~URYP. and GIBSONJ. F. Symptorns of anxiety and tension anti accompanying physiological changes in the muscular system. J. Neurol. Neurosurg. Psychiat. 17, 216 224 (1954). 5. MALMOR. B., WALLERSTEIN H. and SHAGASSC. Headache proneness and mechanisms of motor conflict in psychiatric patients. J. Person. 22, 163-187 (1953). 6. BUDZYNSKIT. H., STOYVAJ. M., ADLERC. S. and MULLANEYD. J. EMG biofeedback and tension headaches: a controlled outcome study. Psyehosom. Med. 35, 484-496 (1973). 7. PHILIPS C. A psychological analysis of tension headache. In Advances in Medical Psychology (Edited by RACHMANS.). Pergamon Press, Oxford (1977). 8. BAKALD. A. and KAGANOVJ. A. Muscle contraction and migraine headache: a psychophysiological comparison, tfeadache 17, 208--215 (1977). 9. LIPPOLD O. C. J. Electromyography. In Manual o f Psychophysiological MethocLv (Edited by VENABLESP. H. and MARTIN1.), pp. 245-297. North Holland, Amsterdam (1967). 10. HARDYJ. D., WOLFFH. G. and GOODELLH. Studies in pain: A new method for measuring pain threshold: observations of spatial summation of pain. J. Clin. Invest. 19, 649-657 (1940). l [. FURNEAUXW. D. ~4anual o[Nuff?rno Level Tests. National Foundation for Educational Research, London (I 950). 12. HUTCHINGSD. F. and REINKINGR. H. Tension headaches: what form of therapy is most effective? BioJ~,ed. Serf:Reg. l, 183-190 (1976). 13. HAYNES S. N., GRIFFIN P., MOONEY D. and PARISE M. Electromyographic biofeedback and relaxation instructions in the treatment of muscle contraction headaches. Behc¢. Ther. 6, 672-678
(1975).
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14. Cox D. J., FREUNDLICH A. and MEYER R. G. Differential effectiveness of electromyograph feedback, verbal relaxation instructions, and medication placebo with tension headaches. J. Consult. Clin. Psychol. 43, 892-898 (1975). 15. PHILIPS C. The modification of tension headache pain using E M G biofeedback. Behav. Res. Therap. 14, 119-129 (1977). 16. EPSTEIN L. H. and ABEL G. G. An analysis of biofeedback training effects for tension headache patients. Behav. Ther. 8, 37~1-7 (1977). 17. JACOSSON E. Progressive Relaxation. University of Chicago Press, Chicago, Ill. 0938). 18. DALESSIO D. J. Wo[ff's Headache and Other Head Pain. Oxford University Press, New York (1972). 19. Ad hoc Committee on Classification of Headache. Classification of headache. J. Am. Med. Ass. 179, 717-718 (1962). 20. ZIGGLER D. K., HASSANEIN R. and HASSANEIN K. Headache syndromes suggested by factor analysis of symptom variables in a headache prone population. J. Chron. Dis. 25, 335-365 0972). 21. WATERSW. E. The epidemiological enigma of migraine. Int. J. Epidem. 7, 189-195 (1977).