Chronic pain in society--a case for chronic pain as a dysfunctional state?

Diagnostic accuracy of the Pain (P), Enjoyment (E), and General activity (G) scale, a three-item questionnaire, for grading the impact of orofacial pain-related dysfunction

ABSTRACT

Purpose of this study was to examine the discriminative properties of the 3-item Pain (P), Enjoyment (E), and General activity (G) (PEG) questionnaire for grading impact of nondental orofacial pain. Two hundred eighty-six consecutive patients with orofacial pain of nondental origin filled out the PEG questionnaire and Graded Chronic Pain Scale (GCPS, version 2). Correlation between the PEG and GCPS scores, internal consistency of the PEG, and differences between groups were examined statistically (level of significance: P ≤ 0.05). The mean (±SD) age of the 213 patients (158 female) who were included in the analysis was 43.1 (±16.7) years. Of the sample, 48.8% (n = 104) had some degree of orofacial pain-related disability (mean overall characteristic pain intensity: 51.2 ± 23.2, average overall PEG score: 4.3 ± 2.7, and average PHQ-9 score: 8.2 ± 6.5). No significant differences were found between the sexes for any score. The number of disability points (GCPS) and overall PEG score showed a strong and positive correlation (Spearman ρ = 0.77, P < 0.001). The internal consistency of the PEG questionnaire was high (Cronbach α = 0.86). Assuming 3 different levels of orofacial pain-related disability (mild, moderate, and severe), we obtained overall accuracy of 69.01%, with high specificity for mild and severe cases. The 3 PEG groups (mild, moderate, or severe) differed from each other significantly regarding their clinical grading according to the GCPS (Kruskal-Wallis, P < 0.001). Analysis of the receiver operating characteristic curve showed that a single cutoff value of 3.8 points in the PEG score yields adequate validity (sensitivity = 0.91 and specificity = 0.78). The proposed 2 cutoff points (upper = 7 and lower = 4) yield low sensitivity for the upper threshold. The 3-item PEG questionnaire is suitable for grading impact of nondental orofacial pain.

Increases in local pressure pain thresholds after muscle exertion in women with chronic shoulder pain

OBJECTIVE

To examine the relation between muscular tenderness and local muscular fatigue.

DESIGN

Before-after trial, measuring pressure pain thresholds and signs of local muscular fatigue by using surface electromyography before, after, 10 minutes after, and 20 minutes after intervention.

SETTING

University rehabilitation department in Sweden.

PARTICIPANTS

Nineteen female hospital cleaners with unilateral chronic shoulder pain for 1 year. No previous trauma, surgery, or signs of systemic or neurologic disease.

INTERVENTION

Static abduction endurance test with submaximal unilateral activation of the trapezius and deltoid muscles.

MAIN OUTCOME MEASURES

Pressure pain thresholds and electromyographic fatigue parameters (root mean square [RMS]; mean power frequency [MPF]).

RESULTS

Mean normalized pressure pain threshold values increased significantly (95% confidence interval [CI]) and lasted for 20 minutes: in the trapezius, threshold values increased to 115% to 120% (95% CI, 100%-140%; P=.04-.05); and in the deltoid, the threshold increased to 112% to 115% (95% CI, 100%-130%; P=.02-.05). Development of significant electromyographically defined fatigue was seen: in the trapezius, the RMS increased to 130% (95% CI, 119%-141%), and in the deltoid, the MPF decreased to 78% (95% CI, 74%-82%), but normalized within 15 seconds to 10 minutes.

CONCLUSION

Lasting bilateral increases in pressure pain thresholds but transient local muscular fatigue were seen after a unilateral static endurance test. The sensitivity of the sensory nervous system may change during a static muscle contraction and sometimes contributes to a localized sensation of numbness.

Pressure pain thresholds and electromyographically defined muscular fatigue induced by a muscular endurance test in normal women

OBJECTIVE

This study was undertaken to examine the relation between muscular tenderness measured as pressure pain thresholds (PPTs) and electromyographic (EMG) signs of fatigue before and after a local standardized static muscle contraction.

DESIGN

Pressure pain thresholds were measured in the shoulder region before, immediately after, and 10 minutes after a standardized static endurance test while monitoring the EMG signs of local muscular fatigue and its recovery. The study did not address local biochemical issues.

SETTING

The study was conducted at the Department of Rehabilitation, Lund University Hospital, Lund, Sweden.

SUBJECTS

Twenty-five healthy female volunteers without musculoskeletal problems participated in this study.

INTERVENTION

A static endurance test was performed, which consisted of a submaximal unilateral activation of the right trapezius and deltoid muscles for as long as possible.

OUTCOME MEASURES

Bilateral PPTs over the trapezius and deltoid muscles were measured with an electronic pressure algometer. Established surface EMG parameters of local muscular fatigue were assessed. The Borg Rating of Perceived Exertion scale was used.

RESULTS

The average endurance time was 330 seconds. Immediately after the test, significant bilateral increases in the normalized PPTs over both muscles were found, although the increase was more pronounced on the test side: over the right trapezius muscle by 13% (p <0.001), over the right deltoid muscle by 23% (p <0.001), and over the left trapezius and deltoid muscles by 6% (p = 0.04) and (p = 0.009), respectively. These increases persisted 10 minutes after the end of the test. The subjects developed significant signs of fatigue as defined by EMG criteria in both muscles on the right side during the test. The recovery from fatigue was approximately half complete 15 seconds after the end of the test and complete or almost complete 10 minutes thereafter.

CONCLUSIONS

Pressure pain thresholds over shoulder muscles remained elevated up to 10 minutes after a unilateral static endurance test. This time course was completely different from that of EMG-defined muscle fatigue, which showed a fast recovery. These findings indicate that the mechanisms of recovery from fatigue and nociception are independent of each other. The bilateral PPT increases might be explained by central antinociceptive mechanisms activated by static muscle work.

Musculoskeletal chronic pain in general practice. Studies of health care utilisation in comparison with pain prevalence

OBJECTIVE

To study the relations between population prevalence of chronic pain and pain-related diagnoses (musculoskeletal and headaches) in primary health care (PHC) and to examine longitudinal variations in these diagnoses.

DESIGN

A population-based mailed survey to catch prevalence data and continuous computerised diagnosis registration in PHC.

SETTING

General population in a well-defined Swedish PHC district.

SUBJECTS

A random sample of 15% of the population aged 25-74, n = 1101. Annual visitors to district physicians at the health centre.

MAIN OUTCOME MEASURES

Rates of pain-related diagnoses in PHC in relation to population prevalence of chronic pain. Comparisons of the number of individuals (annual visiting rates) with pain-related diagnoses 1987-1996.

RESULTS

Population pain prevalence and pain-related diagnoses in PHC corresponded as regards the magnitude and distribution of chronic pain by age and partly by pain location. Compared to low-back and widespread pain, neck-shoulder pain and headaches were less frequent in PHC in relation to reported prevalence. From 1987 to 1996 we found an increasing number of individuals seeking primary care with pain-related diagnoses. The increase was mainly assigned to the groups of fibrositis/myalgia and headache.

CONCLUSION

Pain-related diagnoses in PHC reflect partly the occurrence of self-reported chronic pain symptoms in the population. The observed increase in visits with pain-related diagnoses in the last 10 years is due to an increased number of individuals with soft-tissue rheumatism and headaches. Future studies will have to elucidate whether these findings are due to an increase in morbidity or changes in care-seeking and social conditions.