Central and peripheral mechanisms in chronic tension-type headache

Effect of 4 Weeks of Cervical Deep Muscle Flexion Exercise on Headache and Sleep Disorder in Patients with Tension Headache and Forward Head Posture

The purpose of this study was to investigate the effect of flexion exercise of the deep cervical muscles on headache and sleep disorders in patients with tension headaches and forward head posture. A total of 32 patients with tension headaches and forward head posture were randomly assigned to two groups: an experimental group (n = 16) and a control group (n = 16). The experimental group performed cervical deep muscle flexion exercises for 4 weeks, whereas the control group performed stretching exercises for the same period. The Henry Ford Hospital Headache Disability Inventory (HDI) was used for headache assessment, and the Korean version of the Pittsburgh Sleep Quality Index (PSQI-K) was used for sleep disorder assessment. The experimental group showed a significant reduction in both HDI and PSQI-K score after 4 weeks of intervention (p < 0.001), while no significant difference was found in the control group (p > 0.05). On comparing the experimental and control groups, we found a significant difference in changes in the HDI and PSQI-K between the groups (p < 0.05). The results indicate that flexion exercise of the deep cervical muscles in patients with tension headache and forward head posture will improve the quality of life and activities of daily life by mitigating headaches and sleep disorders.

Physical therapy and migraine: musculoskeletal and balance dysfunctions and their relevance for clinical practice

BACKGROUND

Migraine is a primary headache with high levels of associated disability that can be related to a variety of symptoms and comorbidities. The role of physical therapy in the management of migraine is largely unknown. Therefore, the aim of this review is to highlight and critically discuss the current literature and evidence for physical therapy interventions in individuals with migraines.

METHODS

A narrative review of the literature was performed.

RESULTS

Physical therapists assessing and treating patients with migraine should focus on two primary aspects: (1) musculoskeletal dysfunctions, and (2) vestibular symptoms/postural control impairment. Signs and symptoms of musculoskeletal and/or vestibular dysfunctions are prevalent among individuals with migraines and different disability levels can be observed depending on the presence of aura or increment of the migraine attacks.

CONCLUSION

A proper physical examination and interview of the patients will lead to a tailored treatment plan. The primary aim regarding musculoskeletal dysfunctions is to reduce pain and sensitization, and physical therapy interventions may include a combination of manual therapy, exercise therapy, and education. The aim regarding postural control impairment is to optimize function and reduce vestibular symptoms, and interventions should include balance exercises and vestibular rehabilitation. However, consistent evidence of benefits is still lacking due to the lack of and therefore need for tailored and pragmatic clinical trials with high methodological quality.

Which Examination Tests Detect Differences in Cervical Musculoskeletal Impairments in People With Migraine? A Systematic Review and Meta-Analysis

BACKGROUND

Most patients with migraine report associated neck pain. Whether neck pain is a symptom of migraine or an indicator for associated cervical musculoskeletal impairment has not yet been determined. Physical examination tests to detect cervical impairments in people with headache have been suggested, but results have not been evaluated systematically and combined in meta-analyses.

PURPOSE

The purpose of this study was to identify musculoskeletal impairments in people with migraine and people who were healthy (healthy controls) by reviewing published data on physical examination results.

DATA SOURCES

PubMed, CINAHL, Web of Science, and the Cochrane Register of Clinical Trials were searched for studies published prior to December 2017.

STUDY SELECTION

Publications investigating physical examination procedures that are feasible for use in a physical therapy setting for patients with migraine and healthy controls were independently selected by 2 researchers.

DATA EXTRACTION

One researcher extracted the data into predesigned data extraction tables. Entries were checked for correctness by a second researcher. The Downs and Black Scale was used for risk-of-bias assessment by 2 reviewers independently.

DATA SYNTHESIS

Thirty-five studies (involving 1033 participants who were healthy [healthy controls] and 1371 participants with migraine) were included in the qualitative synthesis, and 18 were included in the meta-analyses (544 healthy controls and 603 participants with migraine). Overall, studies were rated as having a low to moderate risk of bias. Included studies reported 20 different test procedures. Combined mean effects indicated that 4 of the tests included in the meta-analyses distinguished between patients and controls: range of cervical motion, flexion-rotation, pressure pain thresholds, and forward head posture in a standing position.

LIMITATIONS

Manual joint testing and evaluation of trigger points were the 2 most frequently investigated tests not included in the meta-analyses because of heterogeneity of reporting and procedures.

CONCLUSIONS

Three tests confirmed the presence of musculoskeletal impairments in participants with migraine when combined in meta-analyses. Pressure pain thresholds added information on sensory processing. Additional tests might be useful but require standardized protocols and reporting.

Association Between Trapezius Muscle Tenderness and Tension-Type Headache in Female Office Workers: A Cross-sectional Study

OBJECTIVE

The purpose of the study was to determine the association between trapezius muscle tenderness and tension-type headache among female office workers.

METHODS

Through a questionnaire survey, 256 female office workers with tension-type headaches reported the level of palpable tenderness ("no," "some," or "severe tenderness") in the trapezius muscle. The number of days with headache ("0-7," "8-14," or ">14"), intensity ("low," "moderate," or "high"), duration of headache ("<8 hours per day," ">8 hours per day," and "all day"), and use of analgesic medications were reported. Odds ratio (OR) for tenderness in the trapezius muscle ("no/some" vs "severe tenderness") as a function of days with headache, intensity of headache, duration of headache, and use of analgesic medications were calculated using a binary logistic regression controlling for age and body mass index.

RESULTS

After adjustments for confounders, a strong association was found between the level of trapezius muscle tenderness and intensity of headache (moderate intensity, OR 2.45; 95% confidence interval [CI] 1.08-5.54; high intensity, OR 7.51 [95% CI 2.65-21.29]) and days with headache (>14 days, OR 4.75 [95% CI 1.41-15.89]). No association was observed for duration of headache or use of analgesic medications.

CONCLUSIONS

For the participants studied, there was a strong association between trapezius muscle tenderness and the level of intensity and the number of days with a headache among female office workers. No association was seen for duration of headaches or use of analgesic medications.

Characteristics of Neck Pain Associated With Adolescent Headache

The objective of the study was to find out what kind of neck pain (NP) is associated with headache (HA) and with various headache variables: frequency, type, intensity, disturbance, and relief with analgesics. A population-based sample of 12-year-olds with and without HA ( n = 304) was followed for 4 years. At the age of 16 years, NP was evaluated on the basis of self-reported symptoms and a thorough physical examination of the neck region. Both self-reported and measured NP were associated with HA variables. Co-occurrent NP was found in adolescents with migraine as often as in those with tension-type HA. Especially, muscle pain and intensive, frequent NP were associated with disturbing HA unresponsive to analgesics. The study indicates that concomitant NP should be considered in adolescent HA sufferers, and a thorough cervical and muscle evaluation is recommended when planning the treatment of HA.

Exteroceptive Suppression of Masseter Muscle Activity in Juvenile Migraineurs

The second exteroceptive suppression period (ES2) of masseter or temporalis muscle activity may be reduced in adults with chronic tension-type headache. In adults with migraine, ES2 was found normal or tended to be protracted. To date, no studies on exteroceptive suppression in children and adolescents with headaches have been published. We investigated the exteroceptive suppression of masseter muscle activity in 14 migraineurs and 19 controls between 6 and 18 years of age. It was elicited by electrical stimulation at the labial commissure. No differences were found regarding the first suppression period, but ES2 was significantly longer in the migraine group than in controls. The results of the migraine group suggest overactivity of the interneurons of the reflex loop due to impaired inhibitory control from superior antinociceptive systems already at the beginning of this headache disorder.

International consensus on the most useful physical examination tests used by physiotherapists for patients with headache: A Delphi study

BACKGROUND

A wide range of physical tests have been published for use in the assessment of musculoskeletal dysfunction in patients with headache. Which tests are used depends on a physiotherapist's clinical and scientific background as there is little guidance on the most clinically useful tests.

OBJECTIVES

To identify which physical examination tests international experts in physiotherapy consider the most clinically useful for the assessment of patients with headache.

DESIGN/METHODS

Delphi survey with pre-specified procedures based on a systematic search of the literature for physical examination tests proposed for the assessment of musculoskeletal dysfunction in patients with headache.

RESULTS

Seventeen experts completed all three rounds of the survey. Fifteen tests were included in round one with eleven additional tests suggested by the experts. Finally eleven physical examination tests were considered clinically useful: manual joint palpation, the cranio-cervical flexion test, the cervical flexion-rotation test, active range of cervical movement, head forward position, trigger point palpation, muscle tests of the shoulder girdle, passive physiological intervertebral movements, reproduction and resolution of headache symptoms, screening of the thoracic spine, and combined movement tests.

CONCLUSIONS

Eleven tests are suggested as a minimum standard for the physical examination of musculoskeletal dysfunctions in patients with headache.

Pericranial tenderness in chronic tension-type headache: the Akershus population-based study of chronic headache

Background

Most knowledge on chronic tension-type headache (CTTH) is based on data from selected clinic populations, while data from the general population is sparse. Since pericranial tenderness is found to be the most prominent finding in CTTH, we wanted to explore the relationship between CTTH and pericranial muscle tenderness in a population-based sample.

Methods

An age- and gender-stratified random sample of 30,000 persons aged 30-44 years from the general population received a mailed questionnaire. Those with a self-reported chronic headache were interviewed and examined by neurological residents. The questionnaire response rate was 71% and the interview participation rate was 74%. The International Classification of Headache Disorders II was used. Pericranial muscle tenderness was assessed by a total tenderness score (TTS) involving 8 pairs of muscles and tendon insertions. Cross-sectional data from the Danish general population using the same scoring system were used for comparison.

Results

The tenderness scores were significantly higher in women than men in all muscle groups. The TTS was significantly higher in those with co-occurrence of migraine compared with those without; 19.3 vs. 16.8, p = 0.02. Those with bilateral CTTH had a significantly higher TTS than those with unilateral CTTH. The TTS decreased significantly with age. People with CTTH had a significantly higher TTS compared to the general population.

Conclusions

People with CTTH have increased pericranial tenderness. Elevated tenderness scores are associated with co-occurrence of migraine, bilateral headache and low age.

Whether the increased muscle tenderness is primary or secondary to the headache should be addressed by future studies.

Headache during a cluster of benign paroxysmal positional vertigo attacks

OBJECTIVE

In view of patients' recurrent complaints, we were interested in investigating the frequency and headache characteristics in patients during a benign paroxysmal positional vertigo (BPPV) cluster.

METHODS

Patients with BPPV treated at an outpatient dizziness clinic were interviewed about the presence of headache; its quality, localization, severity, time course, and aggravating and alleviating factors; and headache-related disability during their present vertigo cluster.

RESULTS

Among 152 patients with BPPV, 53 (34.8%) reported headache associated with vertigo. According to The International Classification of Headache Disorders, 8 (15%) patients could be classified as migraine without aura (1.1), 14 (26%) were classified as infrequent episodic tension-type headache associated with pericranial tenderness (2.1.1), 23 (43%) were classified as infrequent episodic tension-type headache without pericranial tenderness (2.1.2), 6 (11%) had cervicogenic headache (11.2.1), and in 2 (4%) patients, the headache could not be specified (14.2). Fifty-two age-matched BPPV patients without headache did not differ in history of headaches, BPPV history, or background diseases. The distribution of canal involvement and number of treatment maneuvers was also similar in both groups.

CONCLUSION

Headache is frequent in BPPV. The most common is tension-type headache, followed by migraine and cervicogenic headache. Head pain seems to be an independently associated epiphenomenon of BPPV that can worsen patients' distress.

Nerve growth factor and chronic daily headache: a potential implication for therapy

The pivotal role of nerve growth factor in inducing hyperalgesia and central sensitization has been emphasized in experimental pain models. Higher nerve growth factor levels have recently been found in the cerebrospinal fluid of patients with chronic daily headache. These levels were significantly correlated with the cerebrospinal fluid levels of substance P and calcitonin gene-related peptide, supporting the involvement of this neurotrophin in enhancing the production of the two sensory neuropeptides of the trigemino-vascular system in chronic daily headache. This may, in part, account for the long-lasting sensitization and activation of this system, which could contribute to headache chronicity. More recent research has shown a significant correlation between the higher cerebrospinal fluid levels of nerve growth factor and those of another neurotrophin, the brain-derived neurotrophic factor, as well as glutamate in chronic daily headache patients. These findings suggest the potential involvement of nerve growth factor-mediated upregulation of brain-derived neurotrophic factor in persistent head pain. Therefore, nerve growth factor appears to indirectly exert its effect through enhancing glutamatergic transmission involved in the processing of head pain via brain-derived neurotrophic factor. Based on these data, a potential application can be hypothesized for novel strategies targeting neurotrophins (nerve growth factor and brain-derived neurotrophic factor) and their receptors to chronic daily headache. To date, the majority of the molecules discovered in this regard have been scarcely or never proved in animal pain models and are far from clinical use in chronic pain, including chronic daily headache. If this approach is to be developed in the near future, research should be focused on identifying strategies with few central side effects and specific selective action on central sites involved in chronic head pain and more generally in chronic pain conditions. This will represent a very difficult challenge, taking into account the pleiotropic effect of nerve growth factor and the wide range of intracellular signalling pathways activated by this neurotrophin which are not limited to the nociceptive system.

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.

Neck flexor muscle fatigue in adolescents with headache - An electromyographic study

BACKGROUND

Muscular disorders of the neck region may be of importance for the etiology of tension-type headache. However, in adolescents, there are no data on the association between neck muscle fatigue and headache.

AIM

To study differences in fatigue characteristics of the neck flexor muscles in adolescents with and without headache.

METHODS

A population-based sample of 17-year-old adolescents with migraine-type headache (N=30), tension-type headache (N=29) and healthy controls without headache (N=30) was examined. Surface EMG data were recorded from the sternocleidomastoid (SCM) muscles bilaterally during an isometric neck flexor endurance test. The spectral median frequency (MF) change during the total endurance time (TMF) and the initial time of 30s (IMF) was calculated. The intensity of discomfort in the neck area was assessed with the visual analogue scale (VAS).

RESULTS

The rate of decline in TMF of both SCM muscles was significantly increased in the tension-type headache group compared with controls (right SCM, P=0.030, OR 2.0, 95% 1.2-3.7; left SCM, P=0.009, OR 2.5, 95% 1.4-4.9), while no significant differences were found between controls and subjects with migraine. The rate of decline in IMF, the total endurance time (P=0.050), and VAS did not differ significantly among the study groups.

CONCLUSIONS

This preliminary finding shows that increased neck flexor muscle fatigue in adolescents seems to be associated with tension-type headache.

Changes in Clinical Parameters in Patients with Tension-type Headache Following Massage Therapy: A Pilot Study

Complementary and alternative medicine approaches to treatment for tension-type headache are increasingly popular among patients, but evidence supporting its efficacy is limited. The objective of this study was to assess short term changes on primary and secondary headache pain measures in patients with tension-type headache (TTH) receiving a structured massage therapy program with a focus on myofascial trigger point therapy. Participants were enrolled in an open label trial using a baseline control with four 3-week phases: baseline, massage (two 3-week phases) and follow-up. Twice weekly, 45-minute massage sessions commenced following the baseline phase. A daily headache diary was maintained throughout the study in which participants recorded headache incidence, intensity, and duration. The Headache Disability Index was administered upon study entry and at 3-week intervals thereafter. 18 subjects were enrolled with 16 completing all headache diary, evaluation, and massage assignments. Study participants reported a median of 7.5 years with TTH. Headache frequency decreased from 4.7+/-0.7 episodes per week during baseline to 3.7+/-0.9 during treatment period 2 (P<0.001); reduction was also noted during the follow-up phase (3.2+/-1.0). Secondary measures of headache also decreased across the study phases with headache intensity decreasing by 30% (P<0.01) and headache duration from 4.0+/-1.3 to 2.8+/-0.5 hours (P<0.05). A corresponding improvement in Headache Disability Index was found with massage (P<0.001). This pilot study provides preliminary evidence for reduction in headache pain and disability with massage therapy that targets myofascial trigger points, suggesting the need for more rigorously controlled studies.

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.

Strength and mobility of the neck-shoulder region in adolescent headache

The significance of the musculoskeletal function of the neck-shoulder region in different headache types in children and adolescents is not clear. The purpose of this study was to investigate the association between different types of headache and the strength and mobility of the neck-shoulder region in 13-year-old schoolchildren. A structured questionnaire on headache was sent to all 1,409 children in the sixth grade in the city of Turku. Of the 1,135 (81%) children who completed the questionnaire, a sample from different headache groups was randomly selected for clinical examination. The study consisted of 59 children with migraine, 65 with episodic tension-type headache (TTHA), and 59 headache-free controls. Dynamic muscle strength of the upper extremities (UE endurance), mobility of both shoulders (UE mobility), and the cervical range of motion (CROM) were measured. Girls with episodic TTHA had lower UE endurance of both dominant and nondominant sides than girls in the other study groups. Girls with migraine had lower UE endurance of nondominant side than girls in the control group. In boys, no significant differences were observed. An interesting association between the function of the neck-shoulder region and headache complaints in adolescents was ascertained.

The second exteroceptive suppression is affected by psychophysiological factors

OBJECTIVE

The second exteroceptive suppression (ES2) is assumed to be an indicator of central antinociceptive processing, although some conflicting data have been produced. We examined the impact of experimentally induced psychophysiological conditions on the latency and duration of the ES2. Also, the association to the subjective evaluation of the painful electrical stimulation by which the ES2 is elicited was studied.

METHODS

ES2 was assessed in 46 healthy volunteers running through four experimentally induced psychophysiological conditions: stress, relaxation, depressed mood, and heterotopic pressure pain. Conditions were presented in a repeated measure design in permuted sequences. Ten stimulation-recording sequences per condition were averaged. ES2 parameters were compared to a baseline condition and correlated to subjective pain perception.

RESULTS

ES2 duration was found to be prolonged and ES2 latency to be shortened under the impact of relaxation and depressed mood. The subjective perception of the painful electrical stimulation was affected by the experimental conditions.

CONCLUSION

Data lend support to the hypothesis that the repeatedly observed limited stability of ES2 parameters might be caused by the variability of individual psychophysiological states. Against expectation, subjective pain perception is not systematically correlated with ES2 parameters. Thus it can be questioned whether the ES2 is directly associated with pain processing at all.

Force production and EMG activity of neck muscles in adolescent headache

PURPOSE

This study compared the maximal force, EMG/force ratio and co-activation characteristics of the neck-shoulder muscles between 30 adolescents with migraine-type headache, 29 with tension-type headache, and 30 headache-free controls.

METHOD

Force was measured with surface electromyography (EMG) from the cervical erector spinae (CES), the sternocleidomastoid (SCM) and trapezius muscles during the maximal isometric neck flexion, neck extension and shoulder flexion.

RESULTS

Girls with migraine-type headache had higher EMG/force ratios between the EMG of the left agonist SCM muscle and the corresponding maximal neck flexion (p = 0.030) and neck rotation force to the right side (p = 0.024) than the girls with tension-type headache. Migrainous girls had more co-activation of right antagonist CES muscle during maximal neck flexion force than the girls without headache (p = 0.015). Neck force production showed no significant differences between girls. Girls with tension-type headache displayed lower left shoulder flexion force than girls with migraine-type headache (p = 0.005) or with no headache (p = 0.005). In boys, no significant differences were observed.

CONCLUSIONS

Girls with tension-type headache and migraine-type headache have differences in neuromuscular function in the neck-shoulder muscles. The data amplify our knowledge of the neck-shoulder muscle dysfunction in adolescent headache, and may encourage the use of specific rehabilitation methods in the management of different types of headache.

The Role of Cervical Dysfunction in Migraine: A Systematic Review

This systematic review evaluates the strength of the evidence for the role of cervical musculoskeletal dysfunction in migraine. In this review, cervical musculoskeletal dysfunction will refer to the abnormal sensory afferentation from cervical region structures contained within the receptive field of the trigeminocervical nucleus. Electronic database searches using MEDLINE, PubMed and CINAHL were performed, and 17 studies investigating cervical musculoskeletal dysfunction in people with migraine were selected for review. The methodological quality of the included studies was assessed by two independent reviewers using a customized checklist. The review found that intersubject differences were inadequately reported and controlled, which resulted in grouping of participants with varying pathologies and symptoms. A diverse range of assessment procedures was used by the reviewed studies, which made comparison of their findings difficult. The assessment procedures were mainly used to quantify the degree of cervical musculoskeletal dysfunction, rather than to identify a cause and effect relationship between cervical structure and migrainous pain. Although animal study evidence proposes a role for cervical musculoskeletal dysfunction in migraine, this systematic review of the literature found that there is currently no convincing evidence to confirm this phenomenon in humans.

Predictor variables for identifying patients with chronic tension-type headache who are likely to achieve short-term success with muscle trigger point therapy

To date, no studies have investigated the predictive validity of variables from the initial examination to identify patients with tension-type headache pain who are likely to benefit from muscle trigger point (TrP) therapy. The purpose of this study was to develop a preliminary clinical prediction rule (CPR) to identify chronic tension-type headache (CTTH) patients who are likely to experience a successful response from TrP therapy. Consecutive patients with CTTH underwent a standardized examination and then received six sessions of TrP therapy over 3 weeks (two sessions per week). They were classified as having experienced a successful outcome at short-term (1 week after discharge) and 1-month follow-up based on a 50% reduction on at least one headache parameter (intensity, frequency or duration) and self-report perceived recovery. Potential predictor variables were entered into a stepwise logistic regression model to determine the most accurate set of variables for identifying treatment success. Data from 35 patients were included, of which 19 (55%) experienced a successful outcome. A CPR with four variables for short-term (headache duration < 8.5 h/day, headache frequency < 5.5 days/week, bodily pain < 47 and vitality < 47.5) and a CPR with two variables for 1-month (headache frequency < 5.5 days/week and bodily pain < 47) follow-up were identified. At short-term follow-up, if three of four variables [positive likelihood ratio (LR) 3.4] were present, the chance of experiencing a successful outcome improved from 54% to 80%, and if all the variables (positive LR 5.9) were present, the probability of success was 87.4%. At 1-month follow-up, if one of two variables (positive LR 2.2) was present, the probability of success increased from 54% to 72%, and if both variables (positive LR 4.6) were present, the probability of success was 84.4%. The present CPR provides the potential to identify CTTH patients who are likely to experience short-term and 1-month follow-up success with a muscle TrP therapy approach. Future studies are necessary to validate the CPR.

Increased Pericranial Tenderness, Decreased Pressure Pain Threshold, and Headache Clinical Parameters in Chronic Tension-type Headache Patients

OBJECTIVE

The aim was to investigate whether increased pericranial tenderness or decreased pressure pain threshold (PPT) was related to headache intensity, duration, and frequency in chronic tension-type headache (CTTH).

METHODS

Twenty-five CTTH patients and 25 matched controls were studied. A headache diary was kept for 4 weeks to substantiate the diagnosis and record the pain history. Three tenderness (total, cephalic, and neck) scores and PPT at both cephalic and neck points were objectively and blinded assessed. Bodily pain perceived by the patients was assessed with the Short Form-36 questionnaire.

RESULTS

CTTH patients showed decreased PPT and increased tenderness as compared with controls (P<0.001). Negative correlations were found between PPT on each point and their respective tenderness scores. Within the CTTH group, neither increased tenderness nor decreased PPT seemed to directly influence headache intensity, frequency or duration; or vice versa.

DISCUSSION

Increased tenderness may predispose the patients to other perpetuating factors in inducing headache attacks. Further research is needed to clearly define the role of pericranial tender tissues or other factors in the genesis and maintenance of CTTH.

New developments in the pharmacotherapy of tension-type headaches

The first International Headache Society classification defined tension-type headaches (TTHs) by itemising those characteristics of migraines TTHs did not possess [1]. As a result, TTHs, both episodic and chronic, remain the most nonspecific of all the commonly observed primary headaches. Until recently, there has been little impetus on the part of the pharmaceutical industry to investigate TTHs; many of the potentially useful drugs are now generic and unprofitable. In addition, few investigators have pursued the study of TTHs in lieu of its more glamorous neighbour, migraine. As a result, there are few well-designed studies on the pharmacotherapy of TTHs. The few studies that exist support the use of age-old standard drug classes, the tricyclic antidepressants and the NSAIDs. New research is now emerging that points to the potential utility of botulinum toxin type A, NMDA-receptor antagonists including Mg(2+) and nitric oxide synthase inhibitors. More scientifically rigorous clinical studies are needed.

Depression increases onset of tension-type headache following laboratory stress

The aim of this study is to examine the influence of depression on headache onset following laboratory stress and on psychophysiological variables associated with tension-type headaches (TTHs). Diagnostic interviews identified three groups: headache prone and depressed (HP/D, N = 13); headache prone not depressed (HP/ND, N = 22); and healthy controls (HC, N = 13). Ss completed a laboratory stress task. Blind evaluations of pericranial muscle tenderness (PMT) and pressure pain thresholds (PPT) were obtained immediately before, immediately after and 24 h post-task. Ss also recorded headaches (HA) before, during, immediately post-task and for 24 h post-task. HP/D Ss were more likely than HP/ND Ss or HC Ss to report a headache during and immediately following the stress task (P < 0.05). HP/D Ss exhibited higher PMT than HP/ND Ss or HC Ss before and following the stress task (P < 0.05). HP/D Ss exhibited lower finger PPT at all assessments and lower temporalis PPT at two of three assessments than HC Ss (P < 0.05) but did not significantly differ from HP/ND Ss at most assessments. Depression increased vulnerability to TTH following laboratory stress and was associated with elevated PMT. In individuals with frequent headaches, depression may aggravate existing central sensitization increasing vulnerability to TTHs.

The trigemino-cervical reflex in tension-type headache

To investigate the pathophysiology of tension-type headache (TTH) with special reference to central mechanisms and to the involvement of the trigeminal system. Short latency responses can be recorded in tonically active sternocleidomastoid muscle after stimulation of the infraorbital branch of the trigeminal nerve (the trigemino-cervical reflex). This brainstem reflex was studied in 15 healthy subjects, in 15 patients with episodic tension-type headache (ETTH) and in 15 patients with chronic tension-type headache (CTTH) outside of the pain attacks. The trigemino-cervical response was abnormal, in the size or latency, in 13 patients with CTTH and in only one patient with ETTH. This finding strongly suggests that only in the CTTH the underlying pathophysiology involves the trigeminal system. The trigemino-cervical reflex is a sensitive method to evaluate the involvement of the trigeminal brainstem neurones in TTH and their assessment may provide useful diagnostic and prognostic information.

Post-traumatic myofascial pain of the head and neck

Post-traumatic myofascial pain describes the majority of chronic head and neck pain seen in clinical practice. If conditions such as vascular headaches, neuropathic pain, degenerative cervical joint disease, and dental pain are excluded, myofascial tissues are directly or indirectly involved in all other forms of head and neck pain. The most common of these include temporomandibular disorders, neck pain such as whiplash-associated disorder, cervicogenic headaches, and tension-type headaches. The pathophysiology of these conditions is not widely understood; however, peripheral and central mechanisms appear to play a role.

Behavioral and psychologic aspects of the pathophysiology and management of tension-type headache

Behavioral and psychologic factors in tension-type headache are reviewed with reference to pathophysiology, comorbid psychiatric disorders, headache triggers, and behavioral treatment, including the efficacy of behavioral treatments, brief minimal contact administration of behavioral treatment, therapeutic mechanisms underlying the effectiveness of behavioral treatments, and the integration of drug and behavioral treatments. Anxiety or depression may contribute to central sensitization that underlies frequent tension-type headaches. Excessive analgesic use, comorbid psychiatric disorders, or persistent unaddressed headache triggers may limit the effectiveness of headache treatment. Available drug and behavioral treatments are effective for episodic tension-type headache, but are only moderately effective for chronic tension-type headaches. The combination of behavioral and preventive drug therapies may improve outcomes for patients with chronic tension-type headache.

Assessment and psychological management of recurrent headache disorders

This article updates earlier reviews of recurrent headache disorders published in 1982 and 1992, selectively reviewing research published since 1990. Current issues in assessment (headache diagnosis, psychophysiology, comorbid psychopathology, quality-of-life assessment, and new assessment technologies) and psychological treatment (efficacy, therapeutic mechanisms, treatment delivery, and integration with drug therapy) are addressed. The author emphasizes the need to adapt psychological treatments to the severity of the headache disorder and to developments in drug therapy. Opportunities for the integration of biological, medical, and psychological science are highlighted.

Chronic daily headache in children and adolescents

Chronic daily headache (CDH), an almost continual headache in the absence of organic pathology, is an exceptionally challenging type of headache to treat in children and adolescents. CDH has different expressions in children and adults; the different expressions may reflect several different etiologies or a developmental continuum. Although a positive family history predisposes children to develop headache, many environmental, biological, and psychological processes may share a role in the etiology. To date, no studies have examined the pathophysiology of CDH in children so that our understanding is presumed, rather than documented, and based primarily on extrapolation from adult studies. For some cases with migraine features, presumed mechanisms include a neurogenic inflammatory cascade, vascular reactivity, and serotonin, whereas for other cases, mechanisms may include pericranial muscle tenderness or musculoskeletal abnormalities, as noted recently for adults. A skilled and careful history is the first step to ensuring an accurate diagnosis for children with CDH. Pain assessment is an integral component of diagnosis and treatment. We need an objective measure of headache activity and an understanding of the factors that cause or exacerbate headaches for an individual child. Although many drug and nondrug therapies are available for treating children's headache, we lack data about which therapies are best for children with CDH or its subtypes. The current principles guiding our management of CDH in children and adolescents are extrapolated from the existing literature on childhood headache, CDH in adults, and our clinical experience. A child-centered focus is particularly important in the treatment of CDH because it is not caused by an underlying disease or disorder.

Migraine and tension-type headache reduction through pericranial muscular suppression: a preliminary report

Migraine and tension-type headaches have always plagued mankind. In spite of all the research dollars spent trying to determine the etiologies of these headaches, the neurology community still has not established a known cause of migraine and tension type headaches. This paper describes a study that was conducted for the U.S. Food and Drug Administration in which the efficacy of the Nociceptive Trigeminal Inhibition Tension Suppression System was evaluated and proved safe and efficacious in the reduction of medically diagnosed migraine and tension-type headache.

Antinociceptive reflex alteration in acute posttraumatic headache following whiplash injury

Brainstem-mediated antinociceptive inhibitory reflexes of the temporalis muscle were investigated in 82 patients (47 F, 35 M, mean age 28.3 years, SD 9.4) with acute posttraumatic headache (PH) following whiplash injury but without neurological deficits, bone injury of the cervical spine or a combined direct head trauma on average 5 days after the acceleration trauma. Latencies and durations of the early and late exteroceptive suppression (ES1 and ES2) and the interposed EMG burst (IE) of the EMG of the voluntarily contracted right temporalis muscle evoked by ipsilateral stimulation of the second and third branches of the trigeminal nerve were analyzed and compared to a cohort of 82 normal subjects (43 F, 39 M, mean age 27.7 years, SD 7.1). Highly significant reflex alterations were found in patients with PH with a shortening of ES2 duration with delayed onset and premature ending as the primary parameter of this study, a moderate prolongation of ES1 and IE duration and a delayed onset of IE. The latency of ES1 was not significantly changed. These findings indicate that acute PH in whiplash injury is accompanied by abnormal antinociceptive brainstem reflexes. We conclude that the abnormality of the trigeminal inhibitory temporalis reflex is based on a transient dysfunction of the brainstem-mediated reflex circuit mainly of the late polysynaptic pathways. The reflex abnormalities are considered as a neurophysiological correlate of the posttraumatic (cervico)-cephalic pain syndrome. They point to an altered central pain control in acute PH due to whiplash injury.

Exteroceptive suppression periods and pericranial muscle tenderness in chronic tension-type headache: effects of psychopathology, chronicity and disability

We examined pericranial muscle tenderness and abnormalities in the second exteroceptive suppression period (ES2) of the temporalis muscle in chronic tension-type headache (CTTH; n = 245) utilizing a blind design and methods to standardize the elicitation and scoring of these variables. No ES2 variable differed significantly between CTTH sufferers and controls (all tests, P>0.05). We found no evidence that CTTH sufferers with daily or near daily headaches, a mood or an anxiety disorder, or high levels of disability exhibit abnormal ES2 responses (all tests, P>0.05). CTTH sufferers were significantly more likely than controls to exhibit pervasive tenderness in pericranial muscles examined with standardized (500 g force) manual palpation (P<0.005). Female CTTH sufferers exhibited higher levels of pericranial muscle tenderness than male CTTH sufferers at the same level of headache activity (P<0.0001). Elevated pericranial muscle tenderness was associated with a comorbid anxiety disorder. These findings provide further evidence of pericranial hyperalgesia in CTTH and suggest this phenomenon deserves further study. Basic research that better elucidates the biological significance of the ES2 response and the factors that influence ES2 assessments appears necessary before this measure can be of use in clinical research.

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.

Treatment of chronic cervical-associated headache with botulinum toxin A: a pilot study

OBJECTIVE

To see whether therapy with botulinum toxin A may prove to be an effective treatment for headache of musculoskeletal origin.

BACKGROUND

Headache is a common finding associated with neck injury. Cervicogenic headache, which is believed to be attributable to injury of the ligaments, muscles, or joints of the cervical spine, is centered in the occipital region with pain referred to the frontotemporal region. Botulinum toxin A produces prolonged muscle relaxation, which is dose dependent and can be easily targeted to affected muscles.

METHODS

This randomized, double-blind, placebo-controlled study compares outcome measures in 26 patients suffering from chronic headache subsequent to a cervical whiplash injury. One half of the patients received botulinum toxin A, 100 units, diluted in 1 mL of saline, while the other half received just saline (1 mL). Five cervical trigger points received 0.2 mL each of injectant via a 30-gauge needle. Outcome measures included subjective head pain based on visual analog scales, as well as range of neck motion. Follow-up assessments were carried out at 2 and 4 weeks after treatment.

RESULTS

Fourteen subjects who received botulinum toxin A and 12 who received saline completed the study. At both 2 and 4 weeks post injection, the treatment group showed a significant improvement in pain and range of motion from preinjection levels (P<.01). The placebo group demonstrated no statistically significant changes at any posttreatment time.

The clinical use of brainstem reflexes and hand-muscle reflexes

Brainstem reflexes and hand-muscle reflexes can be elicited and recorded with routine EMG equipment. Not all these reflexes are useful in clinical neurology. But those that are - the subject of this review - exhibit distinct patterns of abnormality that have clinical diagnostic and localizing value in various diseases, including cranial neuropathies, focal lesions within the cervical cord, brainstem, and brain, movement disorders, and pain.

Dynamic assessment of abnormalities in central pain transmission and modulation in tension-type headache sufferers

OBJECTIVE

To examine and compare central pain processing and modulation in young tension-type headache sufferers with that of matched healthy controls using an induced headache "challenge" paradigm.

BACKGROUND

Recent research has suggested that abnormalities in central pain processing and descending pain modulation may contribute to chronic tension-type headache. These abnormalities, if they contribute to headache pathogenesis, should be present in young adult tension-type headache sufferers. Recent research using static measures of physiological variables, such as muscle tenderness and exteroceptive suppression, has identified chronic muscle tenderness as a characteristic of young tension-type headache sufferers, but other central nervous system functional abnormalities may require a dynamic "challenge" to be observed.

METHODS

Twenty-four young women meeting the International Headache Society diagnostic criteria for tension-type headache (headache-prone) and a matched group of 24 healthy women who reported fewer than 10 problem headaches per year (control) participated in a double-blind, placebo-controlled, crossover study. Subjects completed jaw clenching and a placebo condition on different days in counterbalanced order. Pericranial muscle tenderness, pressure-pain thresholds on the temporalis, and exteroceptive suppression periods were assessed before and after each procedure. Head pain was recorded for 12 to16 hours following each condition.

RESULTS

Headache-prone subjects were more likely than controls to experience headaches after both the jaw clenching and placebo procedures, but neither group was significantly more likely to experience headaches following jaw clenching than placebo. In pretreatment measurements, headache-prone subjects exhibited greater muscle tenderness than controls, but pressure-pain detection thresholds and exteroceptive suppression periods did not differ in the two groups. Control subjects showed increases in muscle tenderness and exteroceptive suppression periods following both the clenching and placebo procedures, whereas headache-prone subjects exhibited no significant changes in any of the physiological measures following either experimental manipulation.

CONCLUSIONS

These results confirm previous findings indicating abnormally high pericranial muscle tenderness in young tension headache sufferers even in the headache-free state. In addition, the results suggest that the development of headaches following noxious stimulation is more strongly related to headache proneness and associated abnormalities in central pain transmission or modulation (indexed by pericranial muscle tenderness and exteroceptive suppression responses) than muscle strain induced by jaw clenching.

Prophylactic pharmacological treatment of chronic daily headache

OBJECTIVE

To review all the prophylactic pharmacological treatments for chronic daily headache from the past decade.

BACKGROUND

Chronic daily headache is among the most common diagnoses seen in specialized headache centers. Prior to 1988, there were no criteria for the diagnosis of chronic tension-type headache and chronic daily headache. An expanded chronic daily headache classification has been proposed.

METHODS

A MEDLINE search was performed using the following key words: chronic daily headache, intractable headache, transformed migraine, chronic tension headache, and chronic tension-type headache. We limited our review to those studies published in English in the last decade, including published abstracts and letters to the editor. Double-blind studies carried out prior to 1988 were also included.

RESULTS

Pharmacological treatments for chronic daily headache include antidepressants (tricyclics, tetracyclics, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors), anticonvulsants, muscle relaxants, 5-HT1 agonists, ergots, 5-HT2 antagonists, antianxiety agents, and miscellaneous drugs. Many of these reports are anecdotal, and most are open rather than double-blind studies.

CONCLUSIONS

There is a great variety of pharmacological treatments available for chronic daily headache. Only the antidepressants have been extensively studied. Other medications may be used if these fail. Recommendations based on our experience at the Headache Unit of the Montefiore Medical Center are outlined here.

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.

The comparison of individuals with recurrent tension-type headache and headache-free controls in physiological response, appraisal, and coping with stressors: a review of the literature

It is widely accepted that stress plays an important role in the experience of tension-type headache. This article reviews the literature in which individuals with recurrent tension-type headache are compared to headache-free controls in the experience and appraisal of stress, psychophysiological response to stress, and coping with stress. A modified and extended version of the transactional model of stress as it might apply to tension-type headache is used to organize the relevant literature. In summary, there is evidence to suggest that individuals with recurrent tension-type headache experience more stressful events and are more sensitive and have a lower threshold to pain. There are some suggestions that headache sufferers may use different coping strategies for stress and pain. There is little evidence of differences in physiological responses to stressful events. The shortcomings of this body of literature are addressed and directions for future research are identified.

A comparison of headache symptoms between two groups: a TMD group and a general dental practice group

Several studies have shown that headaches are associated with patients who have temporomandibular disorders (TMD) compared with non-TMD patients. None of these studies separated the patients by gender or controlled for TMD in the two groups of patients. This study compared a TMD group of patients and a non-TMD group for recent headache symptoms, TMD symptoms and for gender differences. Each patient was asked to rate headache, temporomandibular joint and facial pain symptoms over the past week. The data was collected, tabulated and controlled for TMD symptoms. The data was scored using the Fischer's p-test and a multivariate logistic regression analysis was performed. The headaches were significantly greater in the TMD group (p < 001) than in the private practice group with the genders combined. Dividing the two groups into genders, both males and females in the TMD group were shown to have a greater number of headache symptoms, and the number of headaches was statistically different than the non-TMD group (males p = .037, females p < .001). The TMD group had greater severity of headaches than the non-TMD group. Dividing the two groups into genders, females also had a greater severity of headaches than male counterparts in the TMD and non-TMD groups. From the multivariate logistic regression analysis, these results indicate that headache symptoms are common in patients with TMD symptoms and that the headaches were more severe in the TMD patients than in the non-TMD patients.

The induction of pain: an integrative review

The highly disagreeable sensation of pain results from an extraordinarily complex and interactive series of mechanisms integrated at all levels of the neuroaxis, from the periphery, via the dorsal horn to higher cerebral structures. Pain is usually elicited by the activation of specific nociceptors ('nociceptive pain'). However, it may also result from injury to sensory fibres, or from damage to the CNS itself ('neuropathic pain'). Although acute and subchronic, nociceptive pain fulfils a warning role, chronic and/or severe nociceptive and neuropathic pain is maladaptive. Recent years have seen a progressive unravelling of the neuroanatomical circuits and cellular mechanisms underlying the induction of pain. In addition to familiar inflammatory mediators, such as prostaglandins and bradykinin, potentially-important, pronociceptive roles have been proposed for a variety of 'exotic' species, including protons, ATP, cytokines, neurotrophins (growth factors) and nitric oxide. Further, both in the periphery and in the CNS, non-neuronal glial and immunecompetent cells have been shown to play a modulatory role in the response to inflammation and injury, and in processes modifying nociception. In the dorsal horn of the spinal cord, wherein the primary processing of nociceptive information occurs, N-methyl-D-aspartate receptors are activated by glutamate released from nocisponsive afferent fibres. Their activation plays a key role in the induction of neuronal sensitization, a process underlying prolonged painful states. In addition, upon peripheral nerve injury, a reduction of inhibitory interneurone tone in the dorsal horn exacerbates sensitized states and further enhance nociception. As concerns the transfer of nociceptive information to the brain, several pathways other than the classical spinothalamic tract are of importance: for example, the postsynaptic dorsal column pathway. In discussing the roles of supraspinal structures in pain sensation, differences between its 'discriminative-sensory' and 'affective-cognitive' dimensions should be emphasized. The purpose of the present article is to provide a global account of mechanisms involved in the induction of pain. Particular attention is focused on cellular aspects and on the consequences of peripheral nerve injury. In the first part of the review, neuronal pathways for the transmission of nociceptive information from peripheral nerve terminals to the dorsal horn, and therefrom to higher centres, are outlined. This neuronal framework is then exploited for a consideration of peripheral, spinal and supraspinal mechanisms involved in the induction of pain by stimulation of peripheral nociceptors, by peripheral nerve injury and by damage to the CNS itself. Finally, a hypothesis is forwarded that neurotrophins may play an important role in central, adaptive mechanisms modulating nociception. An improved understanding of the origins of pain should facilitate the development of novel strategies for its more effective treatment.

Sensitivity of patients with painful temporomandibular disorders to experimentally evoked pain: evidence for altered temporal summation of pain

Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandibular joint. Several studies have reported that TMD is associated with enhanced sensitivity to experimental pain. Twenty-three TMD subjects and 24 pain-free matched control subjects participated in a set of studies which were designed to evaluate whether the temporal integrative aspects of thermal pain perception are altered in TMD patients compared with control subjects. Specifically, we have examined in both TMD patients and in age- and gender-matched control subjects: (1) the time-course and magnitude of perceived pain evoked by the application of sustained 7-s noxious thermal stimuli (45-48 degrees C) to the face and forearm, (2) the central summation of C-fiber-mediated pain produced by applying brief trains of noxious heat pulses to the skin overlying the ventral aspect of the right palm and (3) the ability to discriminate small increments in noxious heat applied to facial and volar forearm skin. Data collected from these studies indicate that TMD patients show enhanced temporal integration of thermal pain compared with control subjects. TMD patients show greater thermal C-fiber-mediated temporal summation than pain-free subjects and they report a greater magnitude of sustained noxious heat pulses applied to either the face or the forearm than control subjects. In contrast to these findings, TMD and pain-free subjects are equally able to discriminate and detect small increments of heat applied to noxious adapting temperatures. These findings suggest that the augmented temporal integration of noxious stimuli may result from alterations in central nervous system processes which contribute to the enhanced pain sensitivity observed in TMD patients.