Overview of tension-type headache

Tension-type headache (TTH) is the most prevalent form of headache. Although it is not the most severe form of headache, it has a significant impact on society. In spite of this, little is known about its pathophysiology. Current International Headache Society classification has been called into question, and new classification approaches have been suggested. With reference to chronic TTH, the issue of analgesic rebound may confound the diagnosis. Transformed migraine and new persistent daily headaches are clarified and differentiated from chronic TTHs (CTTHs). The best documented abnormality found in TTHs is the presence of pericranial tenderness. It is generally believed that pain is initiated by a peripheral mechanism, most likely increased input from the myofascial nociceptors. In CTTH, there may be an impaired supraspinal modulation of the incoming stimuli. Whether there is an overlap in the continuum between TTH and migraine is controversial. Abortive and prophylactic treatments are discussed and wellness and adjunct therapy are also emphasized. Lastly, special attention is paid to the doctor-patient relationship in patients with difficult headaches.     

Muscular Factors are of Importance in Tension-Type Headache

Recent studies have indicated that muscular disorders may be of importance for the development of increased pain sensitivity in patients with chronic tension-type headache. The objective of the present study was to investigate this hypothesis by examining the pain perception in tension-type headache with and without muscular disorders defined as increased tenderness. We examined 28 patients with episodic tension-type headache, 28 patients with chronic tension-type headache, and 30 healthy controls. Pericranial myofascial tenderness was recorded with manual palpation, and pressure pain detection and tolerances in cephalic and extracephalic locations with an electronic pressure algometer. In addition, thermal pain sensitivity and electromyographic activity were recorded. The main result was significantly lower pressure pain detection thresholds and tolerances in all the examined locations in patients with chronic tension-type headache with a muscular disorder compared to those without a muscular disorder. There were no such differences in any of the examined locations when the two subgroups of patients with episodic tension-type headache were compared. Thermal pain sensitivity did not differ between patients with and without a muscular disorder, while electromyographic activity levels were significantly higher in patients with chronic tension-type headache with than in those without a muscular disorder. Our results strongly indicate that prolonged nociceptive stimuli from the pericranial myofascial tissue sensitize the central nervous system and, thereby, lead to an increased general pain sensitivity. Muscular factors may, therefore, be of major importance for the conversion of episodic into chronic tension-type headache. The present study complements the understanding of the important interactions between peripheral and central factors in tension-type headache and may lead to a better prevention and treatment of the most prevalent type of headache.     

Referred pain from the trochlear region in tension-type headache: a myofascial trigger point from the superior oblique muscle

BACKGROUND: Tension-type headache (TTH) is a prototypical headache in which myofascial trigger points (MTrPs) can play an important role. To our knowledge, MTrPs in the muscle tissues of the trochlear region, ie, the superior oblique muscle (SOM), have not been previously mentioned, and a referred pain pattern from this region has never been reported. OBJECTIVE: To describe the referred pain from the trochlear area based on the examination of MTrPs in the SOM in patients with episodic and chronic TTH (CTTH). DESIGN: A blinded, controlled study. METHODS: The trochlear region was examined in 15 patients with CTTH, 15 patients with episodic TTH (ETTH), and 15 control subjects. Referred pain elicited by different maneuvers performed during manual palpation, ie, maintained pressure, active muscle contraction, and stretching of the muscle, was assessed with a visual analogue scale. Patients with ETTH were examined on days when they were headache-free, whereas CTTH patients were examined on days in which headache intensity was less than 4 points on a 10-cm horizontal visual analogue scale. RESULTS: Eighty-six percent of patients with CTTH and 60% with ETTH had referred pain that originated from MTrPs in the SOM, while only 27% of the controls reported referred pain. This pain was perceived as a deep ache located at the retro-orbital region, sometimes extending to the supra-orbital region or the homo-lateral forehead. Pain intensity was greater in CTTH patients than in ETTH patients or control subjects (P < .001). CONCLUSIONS: MTrPs in the SOM may evoke a typical referred pain pattern in patients with TTH. The presence of a myofascial disorder in the trochlear region might contribute to the pathogenesis of TTH.     

Central sensitization in tension-type headache--possible pathophysiological mechanisms

The aim of the present thesis was to investigate the pathophysiology of chronic tension-type headache with special reference to central mechanisms. Increased tenderness to palpation of pericranial myofascial tissues is the most apparent abnormality in patients with tension-type headache. A new piece of equipment, a so-called palpometer, that makes it possible to control the pressure intensity exerted during palpation, was developed. Thereafter, it was demonstrated that the measurement of tenderness could be compared between two observers if the palpation pressure was controlled, and that the Total Tenderness Scoring system was well suited for the scoring of tenderness during manual palpation. Subsequently, it was found that pressure pain detection and tolerance thresholds were significantly decreased in the finger and tended to be decreased in the temporal region in chronic tension-type headache patients compared with controls. In addition, the electrical pain threshold in the cephalic region was significantly decreased in patients. It was concluded that the central pain sensitivity was increased in the patients probably due to sensitization of supraspinal neurones. The stimulus-response function for palpation pressure vs. pain was found to be qualitatively altered in chronic tension-type headache patients compared with controls. The abnormality was related to the degree of tenderness and not to the diagnosis of tension-type headache. In support of this, the stimulus-response function was found to be qualitatively altered also in patients with fibromyalgia. It was concluded that the qualitatively altered nociception was probably due to central sensitization at the level of the spinal dorsal horn/trigeminal nucleus. Thereafter, the prophylactic effect of amitriptyline, a non-selective serotonin (5-HT) reuptake inhibitor, and of citalopram, a highly selective 5-HT reuptake inhibitor, was examined in patients with chronic tension-type headache. Amitriptyline reduced headache significantly more than placebo, while citalopram had only a slight and insignificant effect. It was concluded that the blockade of 5-HT reuptake could only partly explain the efficacy of amitriptyline in tension-type headache, and that also other actions of amitriptyline, e.g. reduction of central sensitization, were involved. Finally, the plasma 5-HT level, the platelet 5-HT level and the number of platelet 5-HT transporters were found to be normal in chronic tension-type headache. On the basis of the present and previous studies, a pathophysiological model for tension-type headache is presented. According to the model, the main problem in chronic tension-type headache is central sensitization at the level of the spinal dorsal horn/trigeminal nucleus due to prolonged nociceptive inputs from pericranial myofascial tissues. The increased nociceptive input to supraspinal structures may in turn result in supraspinal sensitization. The central neuroplastic changes may affect the regulation of peripheral mechanisms and thereby lead to, for example, increased pericranial muscle activity or release of neurotransmitters in the myofascial tissues. By such mechanisms the central sensitization may be maintained even after the initial eliciting factors have been normalized, resulting in the conversion of episodic into chronic tension-type headache. Future basic and clinical research should aim at identifying the source of peripheral nociception in order to prevent the development of central sensitization and at ways of reducing established sensitization. This may lead to a much needed improvement in the treatment of chronic tension-type headache and other chronic myofascial pain conditions.     

TENSION-TYPE HEADACHE

Tenderness is the most prominent abnormal finding in patients with tension-type headache (TTH). Recently we developed a model of myofascial tenderness using intramuscular infusion of a combination of bradykinin, serotonin, histamine and prostaglandin E2. We aimed to examine tenderness after this combination in patients with episodic TTH (ETTH). Fifteen patients and 15 healthy controls completed the study. Participants received the combination into the non-dominant trapezius muscle in a randomized, double-blinded and placebo-controlled design. Local tenderness and stimulus-response functions, mechanical pain thresholds (PPDT) in the temporal region and on the finger, and total tenderness score (TTS) were recorded. A local, prolonged, and mild to moderate tenderness was reported both in patients ( P = 0.001) and in controls ( P = 0.001) after the combination compared with the placebo. The response to the combination tended to be increased in patients. The stimulus-response function was leftward shifted after the combination, compared with baseline in both groups. No changes in PPDT or TTS were found after the infusions, whereas baseline PPDTs were decreased in ETTH compared with controls (PPDT finger: P = 0.033; PPDT temporal: P = 0.015). Intramuscular infusion of a combination of endogenous substances induced prolonged tenderness in both patients with episodic TTH and healthy subjects. The present results suggest an increased excitability of peripheral muscle afferents in TTH.     

Pathophysiology of tension-type headache

Tension-type headache is one of the most common primary headache disorders. Advances in basic pain and clinical research have improved our understanding of pathophysiologic mechanisms of tension-type headache. Increased excitability of the central nervous system generated by repetitive and sustained pericranial myofascial input may be responsible for the transformation of episodic tension-type headache into the chronic form. Studies of nitric oxide (NO) mechanisms suggest that NO may play a key role in the pathophysiology of tension-type headache and that the antinociceptive effect of nitric oxide synthase inhibitors may become a novel principle in the future treatment of chronic headache. Future studies should focus on investigation of the source of peripheral nociception, the role of descending pain modulation, and the development of an animal model of tension-type headache to support the pathophysiologic importance of central sensitization in tension-type headache.     

Heat pain thresholds and cerebral event-related potentials following painful CO2 laser stimulation in chronic tension-type headache

Current opinion concerning the pathophysiology of tension-type headache (TTH) and its related pericranial muscle tenderness proposes a primary role of central sensitization at the level of dorsalhorn/trigeminal nucleus as well as the supraspinal level. Investigation of these phenomena can be conducted using laser-evoked potentials (LEPs), which are objective and quantitative neurophysiological tools for the assessment of pain perception. In the present study we examined features of LEPs, as well as cutaneous heat-pain thresholds to laser stimulation, in relation to the tenderness of pericranial muscles in chronic TTH resulting from pericranial muscle disorder, during a pain-free phase. Twelve patients with TTH and 11 healthy controls were examined using the Total Tenderness Scoring (TTS) system. The stimulus was a laser pulse generated by a CO(2) laser. The dorsum of the hand and the cutaneous zones corresponding to pericranial muscles were stimulated. Subjective perception of stimulus intensity was assessed by a visual analogue scale. Two responses, the earlier named N2a and the last named P2, were considered; the absolute latency was measured at the highest peak of each response. The N2a-P2 components' peak-to-peak amplitude was detected. The heat pain threshold was similar in TTH patients and controls at the level of both the hand and pericranial skin. The TTS scores at almost all pericranial sites were higher in TTH patients than in normal controls. The amplitude of the N2a-P2 complex elicited by stimulation of the pericranial zone was greater in TTH patients than in controls; the amplitude increase was significantly associated with the TTS score. Our findings suggest that pericranial tenderness may be a primary phenomenon that precedes headache, and is mediated by a greater pain-specific hypervigilance at the cortical level.     

Dry needling versus friction massage to treat tension type headache: A randomized clinical trial

Tension type headache (TTH), the most common type of headache, is known to be associated with myofascial pain syndrome and the existence of myofascial trigger points. There are several treatment options for myofascial trigger points. In this study we compared the effectiveness of dry needling and friction massage to treat patients with TTH.A convenience sample of 44 patients with TTH participated in this randomized clinical trial. The frequency and intensity of headache, pressure pain threshold at the trigger point site, and cervical range of motion were recorded. Then the participants were randomly assigned to one of two treatment groups for dry needling or friction massage, delivered in 3 sessions during 1 week. The participants were evaluated 48?h after the last treatment session. Analysis of covariance, paired t-test and Wilcoxon's test were used for statistical analysis.The results showed that both treatment methods significantly reduced headache frequency and intensity, and increased pain threshold at the trigger points. However, neither treatment had any effect on cervical range of motion except for extension, which increased in the dry needling group. Between-group comparisons showed that dry needling increased pain threshold significantly more than friction massage. There were no significant differences between groups in any other outcome variables.Dry needling and friction massage were equally effective in improving symptoms in patients with TTH. The decreases in frequency and intensity of headache were similar after both dry needing and friction massage.     

Pathophysiological mechanisms of tension-type headache: a review of epidemiological and experimental studies

In this present thesis I have discussed the epidemiology and possible pathophysiological mechanisms of tension-type headache. A population-based study of 1000 subjects randomly selected from a general population, two clinical studies, and a method study of EMG recordings, were conducted. Tension-type headache was the most prevalent form of headache, with a life-time prevalence of 78% in a general adult population. Thirty percent were affected more than 14 days per year and 3% were chronically affected, i.e. had headache at least every other day. Females were more frequently affected than males, and young subjects more frequently affected than older subjects. Females were more sensitive to mechanical pressure pain and revealed more tenderness from pericranial muscles and tendon insertions than males, and young subjects were more pain-sensitive than older subjects. Significantly higher tenderness in pericranial muscles was found in subjects with tension-type headache compared to migraineurs and to subjects without any experience of headache. Tenderness increased significantly with increasing frequency of tension-type headache in both males and females, whereas no such relation was found for mechanical pain thresholds. The applied EMG methodology was fairly reliable and nonpainful, but due to intersubject variability paired studies should be preferred. Subjects with chronic tension-type headache had slightly increased EMG levels during resting conditions and decreased levels during maximal voluntary contraction compared with headache-free subjects, indicating insufficient relaxation at rest and impaired recruitment at maximal activity. In a subsequent clinical, controlled study, the effect of 30 min of sustained tooth clenching was studied. Within 24 h, 69% of patients and 17% of controls developed a tension-type headache. Shortly after clenching, tenderness was increased in the group who subsequently developed headache, whereas tenderness was stable in the group of patients who remained headache-free, indicating that tenderness might be a causative factor of the headache. Likewise, psychophysical and EMG parameters were studied in 28 patients with tension-type headache, both during and outside of a spontaneous episode of tension-type headache. It was concluded that a peripheral mechanism of tension-type headache is most likely in the episodic subform, whereas a secondary, segmental central sensitization and/or an impaired supraspinal modulation of incoming stimuli seems to be involved in subjects with chronic tension-type headache. Prolonged nociceptive stimuli from myofascial tissue may be of importance for the conversion of episodic into chronic tension-type headache. The author emphasizes that tension-type headache is a multifactorial disorder with several concurrent pathophysiological mechanisms, and that extracranial myofascial nociception may constitute only one of them. The present thesis supplements the understanding of the balance between peripheral and central components in tension-type headache, and thereby, hopefully, leads us to a better prevention and treatment of the most prevalent type of headache.     

Pain and tension-type headache: a review of the possible pathophysiological mechanisms

Abstract Tension-type headache represents a considerable health problem and is one of the most costly diseases in the modern society. However, the knowledge about the pathophysiological mechanisms leading to this disorder is limited. The review presents a summary of available research and experimental data on the pathophysiological mechanisms and the recent pathophysiological models. Although the pain in tension-type headache clinically resembles pain from myofascial tissues, both peripheral and central mechanisms are believed to be involved. It is likely that myofascial nociception is important in episodic tension-type headache and that central mechanisms are involved in the pathophysiology of the chronic form. Neurophysiological investigations are introduced to be the most suitable to confirm an involvement of trigeminal pathways, to substantiate recent theories on sensitization phenomena, and to disclose the exact pain-control mechanisms. More studies are needed to elucidate the mechanisms leading to central sensitization and to develop new therapeutic strategies.     

Amitriptyline reduces myofascial tenderness in patients with chronic tension-type headache

The tricyclic anti-depressant amitriptyline is widely used in the treatment of chronic tension-type headache. The aim of the present study was to investigate whether the analgesic effect is caused by a reduction of muscle pain or by a general reduction of pain sensitivity. Thirty-three non-depressed patients with chronic tension-type headache were treated with amitriptyline 75 mg/day and with the highly selective serotonin reuptake inhibitor citalopram 20 mg/day in a 32-week, double-blind, placebo-controlled, three-way crossover study. At the end of each treatment period, actual headache intensity and pericranial myofascial tenderness were recorded, pressure pain detection and tolerance thresholds were measured in the finger and in the temporal region and the electrical pain threshold was measured at the labial commissure. Amitriptyline reduced tenderness and headache intensity significantly more than placebo (P=0.01 and P=0.04, respectively). The reduction in tenderness could be ascribed solely to the group of patients who responded to amitriptyline treatment by at least 30% reduction in headache while tenderness was unchanged in non-responders. Amitriptyline did not affect pressure or electrical pain thresholds at any of the examined locations. Citalopram had no significant effect on any of the examined parameters. These findings indicate that amitriptyline elicits its analgesic effect in chronic myofascial pain by reducing the transmission of painful stimuli from myofascial tissues rather than by reducing overall pain sensitivity. We suggest that this effect is caused by a segmental reduction of central sensitization in combination with a peripheral anti-nociceptive action.     

Advances in the pathophysiology of tension-type headache: From stress to central sensitization

Tension-type headache (TTH) is the most common and most socioeconomically costly headache. Yet our knowledge regarding TTH pathophysiological mechanisms is still in its early stages. Psychological stress and weak coping mechanisms may initiate and propagate physiological pain via activation of second messengers in downstream substrates involved in pain. It seems that peripheral mechanisms are predominant in the episodic type (ETTH), whereas central mechanisms are involved in the chronic type (CTTH) of tension headache. The conversion from ETTH to CTTH is most relevant to the clinician and the patient, as CTTH is the most debilitating. This paper focuses and summarizes our current understanding of central sensitization, the process by which this conversion occurs in TTH, and proposes an integrated model to explain how ETTH progresses into CTTH in genetically susceptible individuals.     

Possible mechanisms of glyceryl-trinitrate-induced immediate headache in patients with chronic tension-type headache

Nitric oxide (NO) plays an important role in the pathophysiology of primary headaches including chronic tension-type headache (CTTH). Thus, a NO synthase inhibitor reduces headache and muscle hardness while the NO donor glyceryl trinitrate (GTN) causes more headache in patients than in healthy controls. Sensitization of myofascial pain pathways is important in CTTH, and the aim of the present study was to investigate if such mechanisms may also explain GTN-induced immediate headache in patients with CTTH. In a randomized, double-blind, crossover study 16 patients with CTTH and 16 healthy subjects received intravenous infusion of GTN (0.5 microg/kg per min for 20 min) or placebo on two headache-free days separated by at least 1 week. Muscle hardness, myofascial tenderness, mechanical and heat pain thresholds were measured at baseline and at 60 min and 120 min after start of infusion. In patients, GTN infusion resulted in a biphasic response with immediate headache and more pronounced delayed headache. A similar but less pronounced response was seen in controls. There was no difference between GTN and placebo regarding muscle hardness, myofascial tenderness or pressure and heat pain thresholds in either patients or controls (P>0.05). The unchanged sensitivity of pericranial myofascial pain pathways indicates that peripheral and central sensitization is not involved in the mechanisms of GTN-induced immediate headache.     

Similarities in stress physiology among patients with chronic pain and headache disorders: evidence for a common pathophysiological mechanism?

One common feature of chronic musculoskeletal pain and headaches are that they are both influenced by stress. Among these, tension-type headache (TTH), fibromyalgia (FMS) and chronic shoulder/neck pain (SNP) appear to have several similarities, both with regard to pathophysiology, clinical features and demographics. The main hypothesis of the present study was that patients with chronic pain (TTH, FMS and SNP) had stress-induced features distinguishing them from migraine patients and healthy controls. We measured pain, blood pressure, heart rate (HR) and skin blood flow (BF) during (1 h) and after (30 min) controlled low-grade cognitive stressor in 22 migraine patients, 18 TTH patients, 23 FMS patients, 29 SNP patients and 44 healthy controls. FMS patients had a lower early HR response to stress than migraine patients, but no differences were found among FMS, TTH and SNP patients. Finger skin BF decreased more in FMS patients compared to migraine patients, both during and after the test. When comparing chronic pain patients (chronic TTH, FMS and SNP) with those with episodic pain (episodic TTH and migraine patients) or little or no pain (healthy controls), different adaptation profiles were found during the test for systolic and diastolic blood pressure, HR and skin BF in the chronic group. In conclusion, these results suggest that TTH, FMS and SNP patients may share common pathophysiological mechanisms regarding the physiological responses to and recovery from low-grade cognitive stress, differentiating them from episodic pain conditions such as migraine.     

Pain perception studies in tension-type headache

Tension-type headache (TTH) is a disorder with high prevalence and significant impact on society. Understanding of pathophysiology of TTH is paramount for development of effective treatments and prevention of chronification of TTH. Our aim was to review the findings from pain perception studies of pathophysiology of TTH as well as to review the research of pathophysiology of TTH. Pain perception studies such as measurement of muscle tenderness, pain detection thresholds, pain tolerance thresholds, pain response to suprathreshold stimulation, temporal summation and diffuse noxious inhibitory control (DNIC) have played a central role in elucidating the pathophysiology of TTH. It has been demonstrated that continuous nociceptive input from peripheral myofascial structures may induce central sensitization and thereby chronification of the headache. Measurements of pain tolerance thresholds and suprathreshold stimulation have shown presence of generalized hyperalgesia in chronic tension-type headache (CTTH) patients, while DNIC function has been shown to be reduced in CTTH. One imaging study showed loss of gray matter structures involved in pain processing in CTTH patients. Future studies should aim to integrate pain perception and imaging to confirm this finding. Pharmacological studies have shown that drugs like tricyclic anti-depressant amitriptyline and nitric oxide synthase inhibitors can reverse central sensitization and the chronicity of headache. Finally, low frequency electrical stimulation has been shown to rapidly reverse central sensitization and may be a new modality in treatment of CTTH and other chronic pain disorders.     

紧张型头痛患者椎-基底动脉经颅多普勒超声检查的临床意义

目的:观察紧张型头痛(TTH)患者椎-基底动脉血流动力学改变,并探讨其临床意义.方法: TTH患者106例,其中伴有颅周肌障碍TTH(TTH-PM)42例和不伴有颅周肌障碍TTH(TTH-NOPM)64例;对照组48例,为无头痛症状的健康体检者.采用经颅多普勒(TCD)脑血流分析技术测定两侧椎动脉(VA)及基底动脉(BA)平均血流速度(Vm).结果: TTH患者,尤其是TTH-PM患者椎-基底动脉Vm显著增快,且以右侧椎动脉更为明显.结论: TTH患者有椎-基底动脉血流动力学异常,以TTH-PM者更显著.     

Myofascial trigger points and sensitization: an updated pain model for tension-type headache

Present pain models for tension-type headache suggest that nociceptive inputs from peripheral tender muscles can lead to central sensitization and chronic tension-type headache (CTTH) conditions. Such models support that possible peripheral mechanisms leading to pericranial tenderness include activation or sensitization of nociceptive nerve endings by liberation of chemical mediators (bradikinin, serotonin, substance P). However, a study has found that non-specific tender points in CTTH subjects were not responsible for liberation of algogenic substances in the periphery. Assuming that liberation of algogenic substances is important, the question arising is: if tender muscle points are not the primary sites of on-going neurogenic inflammation, which structure can be responsible for liberation of chemical mediators in the periphery? A recent study has found higher levels of algogenic substances, and lower pH levels, in active myofascial trigger point (TrPs) compared with control tender points. Clinical studies have demonstrated that referred pain elicited by head and neck muscles contribute to head pain patterns in CTTH. Based on available data, an updated pain model for CTTH is proposed in which headache can at least partly be explained by referred pain from TrPs in the posterior cervical, head and shoulder muscles. In this updated pain model, TrPs would be the primary hyperalgesic zones responsible for the development of central sensitization in CTTH.     

Impaired postural control in patients affected by tension-type headache

Sixteen subjects, affected by chronic tension-type headache (TTH) accordingly to the International Headache Society Classification (1988) criteria, in presence of tenderness in pericranial muscles,with a mean age of 37+/-11.8 years, and ten healthy volunteer subjects, age and sex matched, were submitted to postural analysis by Static Posturography (S.Ve.P. Amplaid). Aim of the study was to evaluate whether patients with TTH have disturbed postural control, as compared to normal subjects. Postural analysis considered all posturographic variables but focused on spectral frequency analysis of body sway. In both open (OE) and closed eyes (CE) condition, spectral frequency analysis showed a significantly increased body sway at low (OE= p < or = 0.01; CE= p < or = 0.01) and middle (OE= p < or = 0.01; CE= p < or = 0.01) frequencies on the antero-posterior (y) plane and at low frequencies (OE= p < or = 0.05; CE= p < or = 0.05) on the lateral (x) plane. Statistical analysis was performed using the Student's t test for unpaired data, p value 0.05 defined significant. The proprioceptive input seems to be predominant at middle and high frequencies in maintaining posture, our results seem then to suggest a proprioceptive disturbance in TTH patients. The disturbance is likely related to chronic pericranial muscle contraction and tenderness. Posturography and spectral analysis may help not only in the diagnosis of a postural disturbance but even more in the follow-up of TTH patients, during and after a medical and/or a rehabilitative treatment.     

Pain sensitivity and pain reactivity of pericranial muscles in migraine and tension-type headache

We investigated whether experimentally determined, suprathreshold pain sensitivity of pericranial musculature in patients with tension-type headache differs from that of migraine patients or from that of healthy subjects. Furthermore, we looked to see whether differences could be found in the effects of experimental pain induction on EMG activity of pericranial musculature and whether subgroups could be discovered with higher and lower pericranial pain sensitivity within the three diagnostic groups in terms of neurophysiological, psychological and clinical variables. In 20 patients with tension-type headache, 23 patients with migraine without aura, and 29 healthy individuals experimental pain was induced in the temporal muscle by mechanical pressure; pain sensitivity in the entire metrically subdivided suprathreshold pain sensitivity range was measured. Surface EMG activity of pericranial muscles was determined before, during and after experimental pain induction. In addition, headache characteristics as well as personality and mood states were determined and recorded in a standardized fashion. There were no significant differences in pain sensitivity of pericranial musculature between the three groups. Patients with tension-type headache showed significantly higher EMG scores during suprathreshold pain stimulation than did migraine patients. EMG scores of healthy subjects fell between these two groups. With respect to pericranial tenderness significant differences in clinical, neurophysiological and psychological variables were found only between subgroups within the group of patients with tension-type headache. The results indicate that significant differences in the examined groups are found not in pain perception but in the processing or reaction to experimental headache stimuli. In patients with tension-type headache subgroups evolve based on pericranial pain sensitivity with quantitatively and/or qualitatively impaired reactions; for this reason diagnostic grouping according to the IHS classification seems to be pathophysiologically relevant. The intraindividual phasic comparison of pain reactions appears to be more important than the absolute interindividual tonic comparison.