Aspects Of Pain Perception Research Articles

Pupillometry as a Potential Objective Measurement of Pain Assessment in Healthy Volunteers.

Pain leads to activation of the autonomic nervous system and thus, among other things, to pupillary reflex dilation (PRD). Previous studies have already confirmed a correlation between the perception of pain and the pupillary reaction, measured using pupillometry. However, the previous study populations were under the influence of medication for analgesia in perioperative setting or suffered from pain. This study examines the relationship between pupillary reaction and pain perception in healthy controls and addresses the question of whether endogenous pain inhibition, clinically tested by conditioned pain modulation (CPM), can be quantified using pupillometry. Forty-two healthy volunteers (21 females, 21 males, mean age 27.9 ± 5.8 years, range 20-39 years) were included in this study. The PRD, as a measure of the pupillary reaction (variance from the base diameter in percent), was investigated during baseline, heat application and during CPM testing and results compared to the reported pain intensity on the numerical rating scale (NRS). The volunteers showed higher variances under painful conditions compared to the measurement at rest corresponding to higher sympathetic activity during pain. Volunteers with a higher variance, ie a stronger pupillary reaction, gave higher pain ratings than subjects with a lower pupil variance. However, there was no correlation between the NRS and PRD. PRD and pain ratings during CPM were significantly lower compared to heat pain application alone. However, there was no correlation between the calculated CPM effect and the PRD. Pupillometry is capable of objectively reflecting the pain response, eg pain relief through CPM testing. However, the CPM effect calculated from the subjective pain ratings and the objective PRD measurements is not associated suggesting that both measure different aspects of pain perception. It must be discussed whether the CPM effect can be the correct measure for the functionality of the pain system.

Alcohol use and the pain system.

The World Health Organization's epidemiological data from 2016 revealed that while 57% of the global population aged 15years or older had abstained from drinking alcohol in the previous year, more than half of the population in the Americas, Europe, and Western Pacific consumed alcohol. The spectrum of alcohol use behavior is broad: low-risk use (sensible and in moderation), at-risk use (e.g., binge drinking), harmful use (misuse) and dependence (alcoholism; addiction; alcohol use disorder). The at-risk use and misuse of alcohol is associated with the transition to dependence, as well as many damaging health outcomes and preventable causes of premature death. Recent conceptualizations of alcohol dependence posit that the subjective experience of pain may be a significant contributing factor in the transition across the spectrum of alcohol use behavior. This narrative review summarizes the effects of alcohol at all levels of the pain system. The pain system includes nociceptors as sensory indicators of potentially dangerous stimuli and tissue damage (nociception), spinal circuits mediating defensive reflexes, and most importantly, the supraspinal circuits mediating nocifensive behaviors and the perception of pain. Although the functional importance of pain is to protect from injury and further or future damage, chronic pain may emerge despite the recovery from, and absence of, biological damage (i.e., in the absence of nociception). Like other biological perceptual systems, pain is a construction contingent on sensory information and a history of individual experiences (i.e., learning and memory). Neuroadaptations and brain plasticity underlying learning and memory and other basic physiological functions can also result in pathological conditions such as chronic pain and addiction. Moreover, the negative affective/emotional aspect of pain perception provides embodied and motivational components that may play a substantial role in the transition from alcohol use to dependence.

Pain experience and social support of endometriosis patients during the COVID-19 pandemic in Germany - results of a web-based cross-sectional survey.

BackgroundEndometriosis is a chronic pain condition in premenopausal women. Pain is mainly characterized by pain intensity and may induce disability in all areas of daily life. Nevertheless, pain is influenced by emotional and social factors as well. Social distancing measures or quarantine, as reaction to rapidly rising infections with the COVID-19 virus due to the SARS-CoV-2 pandemic, were implemented across Europe to prevent the spread of the virus and social distancing measures were imposed by the German government by beginning of March 2020 with initiation of the lockdown by the end of March 2020. The objective of this study was to assess, how social distancing measures during the lockdown impacted the various aspects of pain perception in a group of chronic pain patients, such as women suffering from endometriosis.MethodsBetween 6th to 27th April 2020, an online questionnaire was activated at internet platforms of endometriosis patients support groups. Participants were asked retrospectively at one time point about their visual pain intensity measured by the visual analogue scale (VAS) and pain disability via pain disability index (PDI) prior to initiation of social distancing measures in Germany (VASP, PDIP), as well as the pain intensity and pain disability since implementation of social distancing measures (VASI, PDII). Differences of VAS and PDI previous and after implementation of social distancing measures were displayed as ΔVAS and ΔPDI. Pain experience and social support were assessed by a 5-point Likert scale.Results285 participants completed at least one question regarding pain intensity, disability, pain experience or social support. Dysmenorrhea, the symptom with the highest level of pain assessed by VAS, decreased significantly during the SARS-CoV-2 pandemic compared to the time period prior to social isolation (45.30% respondents experienced improvemenet vs 40.50% who experienced worsening; p = 0.025). The global physical impairment improved significantly (improvement of pain induced disability in 48.20% vs 40.90% with worsening of pain symptoms; p = 0.032) after the implementation of social distancing measures. Pain experience was negatively affected by social distancing measures, since frequency of pain awareness increased in 43.6% (p<0.001) of participants and 30.0% (p<0.001) more participants experienced pain as a threat. Verbalization of pain experience was reduced in 36.6% (p = 0.001) of participants and 14.6% (p = 0.91), 21.9% (p<0.001) and 31.5% (p<0.001) of participants reported less social support from their partner, family and friends.ConclusionsPhysical pain and disability on one hand and emotional and social pain experience on the other were differentially affected by the emerged emotional, social and health care constraints related to the SARS-CoV-2 pandemic.

Pain-less injection: principles and pearls.

There has been an exponential growth in the number of dermatologic procedures performed over the past two decades. This surge in procedural volumes is accompanied by increasing utilization of local anesthetics. A proper technique in administering local anesthesia is necessary to minimize pain and promote comfort, as it is often regarded as the most painful part of cutaneous procedures. Pain is a psychophysiological phenomenon that involves attention, cognitive appraisal, and emotion. Sensory feedback and anxiety are two important aspects of pain perception. This article aims to introduce a novel way that minimizes pain and discomfort associated with local anesthetics. It is the authors' experience that painless injection is achievable by keeping syringes/needles out of sight, proceeding with injection without pre-procedure warning, and engaging patients in a conversation or simple tasks.

Gaining insights on the influence of attention, anxiety, and anticipation on pain perception.

PurposeThis article highlights the influence of attention and pain anticipation on pain attenuation. Pain-related trait anxiety was found to moderate the effect that attention strategies impose on pain perception. This article may contribute to clinical treatments quality, where pain attenuation effect is desired.Participants and methodsOne hundred seven participants, comprising of 72 (67%) females and 35 (33%) males between the age of 17 and 48 (M=22.6, SD =4.36), were used in the analysis. The current study measured the effect of pain anticipation and attention on three aspects of pain perception: threshold, tolerance, and perceived pain intensity. Pain anticipation was manipulated by varying the amount of information given to participants about a future pain stimulus. Attention was manipulated through a sensory focusing task and a distraction task. Participants were randomized into 1) InfoControl group with distraction task trial (n=30), 2) InfoControl group with attention to pain trial (n=26), 3) InfoExtra group with distraction task trial (n=26), or 4) InfoExtra group with attention to pain trial (n=25). The pain stimulus was delivered in a form of heat. The moderating effects of pain-related trait anxiety on these variables were also investigated using Pain Anxiety Symptom Scale Short Form.ResultsTwo structural equation models revealed that anticipation is not a predictor of pain perception and neither did it interact with pain-related trait anxiety. However, attention strategies do significantly relate to pain perception. Furthermore, pain-related anxiety was a significant moderator of attention and pain attenuation. These findings imply that the effectiveness of attention strategies in attenuating pain is affected by individuals’ pain-related trait anxiety.ConclusionThe results suggest the importance of appointing the appropriate attention strategy to different individuals with varying level of trait anxiety. Future explorations are necessary to develop a more specific understanding on the nature of information and distractions on pain perception.

Translation and validation of Simplified Chinese version of the Pain Catastrophizing Scale in chronic pain patients: Education may matter.

ObjectivePain catastrophizing is linked to many aspects of pain perception and defines a unique dimension in predicting pain intensity and physical disability. Pain Catastrophizing Scale (PCS) is an effective, validated,self-report measure, commonly used in clinical trials. Here, we present a Simplified Chinese PCS (SC-PCS) version developed in Chinese patients suffering from chronic pain.MethodsThe SC-PCS was generated in five steps and tested on an initial patient cohort (N = 30). A convenience sample (N = 200) of in-hospital patients with non-malignant pain lasting for more than 12 weeks were recruited for the study, of which 81 completed 5 additional pain questionnaires. A subset (N = 24) of the patients completed an additional SC-PCS, 10 days after the initial query to assess test–retest validation.ResultsIntra-class correlations coefficient indicated high reproducibility and temporal consistency, (0.97), for the total score. Cronbach’s alpha determined high internal consistency across the SC-PCS total score and its three subscales (0.87, 0.85, 0.62, and 0.65). The SC-PCS total score moderately or weakly (R = −0.2 to 0.49), but significantly, correlated with other measurements, such as pain Visual Analog Scale, Beck Depression Inventory, Pain Anxiety Symptoms Scales, Positive and Negative Affect Schedule, and education. We used exploratory factor analysis to examine the dimensionality of the SC-PCS, which indicated instability of the current three-factor model. However, a confirmatory factor analysis indicated that the three-factor model had the best goodness-fitting.ConclusionsWe demonstrate the successful translational adaptation from English to Simplified Chinese as well as the reliability and validity of SC-PCS. An important discovery was education level significantly correlated with SC-PCS, identifying a future consideration for other cross-cultural development of self-reported measures.

DISTINCT ASPECTS OF PAIN CATASTROPHIZING ACCORDING TO CHRONIC PAIN SYNDROMES

Introduction: Catastrophizing is the tendency to magnify the threat value of pain and has been associated with measures of physical and psychological disability among individuals with several pain conditions. The aim of this study was to investigate whether pain catastrophizing is differentially associated with distinct pain syndromes. Methods: This is a cross-sectional study including 158 patients (40 with fibromyalgia, 25 with myofascial pain syndrome, 33 with chronic tensional type headache, 33 with endometriosis, and 27 with knee osteoarthritis) and 93 healthy subjects. The recruitment procedure occurred in concurrence with randomized controlled trials. Participants answered the following instruments: Brazilian Portuguese Pain-Catastrophizing Scale, Beck Depression Inventory II, State-Trait Anxiety Inventory, Pittsburgh Sleep Quality Index, visual analogue scale for pain, as well as a sociodemographic questionnaire. Results: For the total pain catastrophizing score, patients with endometriosis had significantly more catastrophizing thoughts than knee osteoarthritis (p < 0.05). Healthy participants had lower scores than any clinical group. More interestingly were the dimensions of pain catastrophizing, which showed significant differences in more than two groups, especially magnification scores, since these scores were able to discriminate, in a particular way, the majority of clinical samples from each other. We also observed differences between rumination, magnification and helplessness scores in all groups, suggesting that the characteristics of pain catastrophizing are distinct according to the pain disorder. Conclusions: The results suggest that dimensions of pain catastrophizing differ between pain syndromes. Therefore, it is important that researchers and clinicians focus on cognitive and emotional aspects of pain perception to have more successful interventions. Keywords: Chronic pain; catastrophizing; cross-sectional study

P283 Effects of odours on electrophysiological responses to laser pain stimuli

Background Previous studies have shown increases in subjective experience and electrophysiological processing of experimental pain during induction of negative emotions with concurrent multi-modal sensory stimuli. The goal of the present study was to analyse spatio-temporal activation patterns underlying processing of acute pain during exposures to affectively valenced odour stimuli. Methods Negative, positive, and neutral (clean air) odour pulses were presented to 17 healthy participants via an olfactometer whilst brief noxious laser stimuli were administered to the dorsum of the left hand. Brain activity was monitored using electroencephalography (EEG) and participants rated the quality and intensity of pain and odour stimuli following each trial using visual analogue scales. Subjective ratings of pain stimuli and laser evoked potentials (LEPs) were analysed to evaluate the influence of valenced odours on subjective and electrophysioloigical aspects of pain processing. Results Analysis of pain ratings revealed no difference in pain intensity, or specific pain qualities across the different odour conditions. Individual LEP components demonstrated expected correlations with specific aspects of pain perception, but did not differ between odour conditions. Conclusions Contrary to research from other sensory modalities, the findings of the present study suggest that affectively valenced odours do not overtly influence aspects of subjective pain perception or electrophysiological processing of acute pain. This may be due to the influence of top-down factors affecting split perception between competing sensory stimuli, which may interact differently for pain and olfactory perception compared to other modalities.

Pain Related Cortical Oscillations: Methodological Advances and Potential Applications.

Alongside the time-locked event-related potentials (ERPs), nociceptive somatosensory inputs can induce modulations of ongoing oscillations, appeared as event-related synchronization or desynchronization (ERS/ERD) in different frequency bands. These ERD/ERS activities are suggested to reflect various aspects of pain perception, including the representation, encoding, assessment, and integration of the nociceptive sensory inputs, as well as behavioral responses to pain, even the precise details of their roles remain unclear. Previous studies investigating the functional relevance of ERD/ERS activities in pain perception were normally done by assessing their latencies, frequencies, magnitudes, and scalp distributions, which would be then correlated with subjective pain perception or stimulus intensity. Nevertheless, these temporal, spectral, and spatial profiles of stimulus induced ERD/ERS could only partly reveal the dynamics of brain oscillatory activities. Indeed, additional parameters, including but not limited to, phase, neural generator, and cross frequency couplings, should be paid attention to comprehensively and systemically evaluate the dynamics of oscillatory activities associated with pain perception and behavior. This would be crucial in exploring the psychophysiological mechanisms of neural oscillation, and in understanding the neural functions of cortical oscillations involved in pain perception and behavior. Notably, some chronic pain (e.g., neurogenic pain and complex regional pain syndrome) patients are often associated with the occurrence of abnormal synchronized oscillatory brain activities, and selectively modulating cortical oscillatory activities has been showed to be a potential therapy strategy to relieve pain with the application of neurostimulation techniques, e.g., repeated transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS). Thus, the investigation of the oscillatory activities proceeding from phenomenology to function, opens new perspectives to address questions in human pain psychophysiology and pathophysiology, thereby promoting the establishment of rational therapeutic strategy.

Pain Perception in Buddhism Perspective.

Dhamma, which Lord Buddha has presented to people after his enlightenment, analyzes every phenomenon and objects into their ultimate elements. The explanation of sensory system is also found in a part of Dhamma named Abhidhammapitaka, the Book of the Higher Doctrine in Buddhism. To find out the relationship between explanation of pain in the present neuroscience and the explanation of pain in Abhidhamma, the study was carried out by the use of a comprehensive review. The comparisons were in terms of peripheral stimulation, signal transmission, modulation, perception, suffering, determination and decision making for the responding to pain. We found that details of the explanation on pain mechanism and perception in Abhidhamma could associate well with our present scientific knowledge. Furthermore, more refinement information about the process and its function in particular aspects of pain perception were provided in Abhidhammapitaka.

Comunicazione oncologica. Medici e pazienti di fronte al dolore tumorale

This article describes an analysis of a study carried out in Italy on 4,057 cancer patients. More than 4% of Italians - that is 2 million people - have received a cancer diagnosis. Along with a deep investigation of different aspects of pain perception, the peculiarity of this research is the comparison done between the self-perception of the patients about their illness and the data resulting from their clinical records. It is evident that often these two dimensions (illness and disease) do not matches. It is possible that such a discrepancy is due more a patient’s wish to not know than poor health communications carried out by physicians.

Dopamine precursor depletion influences pain affect rather than pain sensation.

Pain is a multidimensional experience, which includes sensory, cognitive, and affective aspects. Converging lines of evidence indicate that dopaminergic neurotransmission plays an important role in human pain perception. However, the precise effects of dopamine on different aspects of pain perception remain to be elucidated. To address this question, we experimentally decreased dopaminergic neurotransmission in 22 healthy human subjects using Acute Phenylalanine and Tyrosine Depletion (APTD). During APTD and a control condition we applied brief painful laser stimuli to the hand, assessed different aspects of pain perception, and recorded electroencephalographic responses. APTD-induced decreases of cerebral dopaminergic activity did not influence sensory aspects of pain perception. In contrast, APTD yielded increases of pain unpleasantness. The increases of unpleasantness ratings positively correlated with effectiveness of APTD. Our finding of an influence of dopaminergic neurotransmission on affective but not sensory aspects of phasic pain suggests that analgesic effects of dopamine might be mediated by indirect effects on pain affect rather than by direct effects on ascending nociceptive signals. These findings contribute to our understanding of the complex relationship between dopamine and pain perception, which may play a role in various clinical pain states.

Differential Diagnosis of Psychological Factors Evoked by Pain Presentations

The degree to which psychological factors are believed to influence the experience of pain has evolved significantly through history. Over the past 100 years, the trend has shifted from a focus on the study of sensory aspects of pain perception to one where psychological factors play a prominent role. Pain is now viewed as a complex subjective experience consisting of sensory, affective, and cognitive components. Psychological presentations of pain are commonly reduced to a differential among Pain Disorder, Somatization Disorder, and Malingering. Limitations in the use of the current DSM-IV-TR diagnostic classifications for pain will lead to changes in the upcoming DSM-V. Psychological testing is becoming increasingly recognized as a valuable evidence-based method for making diagnoses of psychological factors influencing pain presentations. There is a shift from the use of brief measures of pain intensity to multidimensional scales including assessment of affect and perceived functional disability. There is also increased attention to the use of validity scales for assessing symptom exaggeration and other types of response bias. Neuropsychologists, with specialized knowledge and background in evidence based assessment methods, are particularly well equipped to provide valuable input regarding psychological presentations of pain in forensic contexts and in consultation to multidisciplinary treatment teams.

The Influence of Mindfulness on Different Aspects of Pain Perception and Affective Reactivity to Pain - Feasibility of a Multimethodical Approach

Theoretical models define the mechanism of change underlying mindfulness as an uncoupling of unpleasant stimuli (e.g., thoughts, feelings, and body sensations) and subsequent reactions which can be described as decentering, deautomatization, or detachment from contents of consciousness. Mindfulness has strong implications in the prevention and treatment of chronic pain considering current psychological models which highlight the role of dysfunctional reactions to pain or related stimuli like anxiety, catastrophizing, or avoidance. Existing studies cover only some of these aspects. The aim of this study was to explore the feasibility of a multimodal assessment approach to examine the influence of trait mindfulness on the affective reactivity to pain and components of pain perception. Thereby, we covered cognitive, affective, physiological, motivational, and behavioral components as indicators of pain reactivity. Twenty-four healthy students participated in this laboratory study examining the reactions to experimentally induced pain. Results indicate that the multimodal method realized seems to be a promising approach to allow for differentiated conclusions about relations between mindfulness and different process and outcome variables in the treatment of pain. Improvements of the methodical approach and future research directions based on the findings are discussed.

Combined analgesics in (headache) pain therapy: shotgun approach or precise multi-target therapeutics?

BackgroundPain in general and headache in particular are characterized by a change in activity in brain areas involved in pain processing. The therapeutic challenge is to identify drugs with molecular targets that restore the healthy state, resulting in meaningful pain relief or even freedom from pain. Different aspects of pain perception, i.e. sensory and affective components, also explain why there is not just one single target structure for therapeutic approaches to pain. A network of brain areas ("pain matrix") are involved in pain perception and pain control. This diversification of the pain system explains why a wide range of molecularly different substances can be used in the treatment of different pain states and why in recent years more and more studies have described a superior efficacy of a precise multi-target combination therapy compared to therapy with monotherapeutics.DiscussionIn this article, we discuss the available literature on the effects of several fixed-dose combinations in the treatment of headaches and discuss the evidence in support of the role of combination therapy in the pharmacotherapy of pain, particularly of headaches. The scientific rationale behind multi-target combinations is the therapeutic benefit that could not be achieved by the individual constituents and that the single substances of the combinations act together additively or even multiplicatively and cooperate to achieve a completeness of the desired therapeutic effect.As an example the fixesd-dose combination of acetylsalicylic acid (ASA), paracetamol (acetaminophen) and caffeine is reviewed in detail. The major advantage of using such a fixed combination is that the active ingredients act on different but distinct molecular targets and thus are able to act on more signalling cascades involved in pain than most single analgesics without adding more side effects to the therapy.SummaryMultitarget therapeutics like combined analgesics broaden the array of therapeutic options, enable the completeness of the therapeutic effect, and allow doctors (and, in self-medication with OTC medications, the patients themselves) to customize treatment to the patient's specific needs. There is substantial clinical evidence that such a multi-component therapy is more effective than mono-component therapies.

Brain Activation during Input from Mechanoinsensitive versus Polymodal C-Nociceptors

C-nociceptors mediating cutaneous pain in humans can be distinguished in mechano-heat-responsive units (CMH) and mechano-insensitive units (CMi). However, if sensitized in damaged tissue, CMi play an important role in inflammatory pain. CMi differ from CMH by higher electrical thresholds and by mediating the axon reflex. Using these properties, we established two stimulation paradigms: (1) transcutaneous stimulation (TCS) of low current density below the CMi threshold and (2) intracutaneous stimulation (ICS) of high current density that excites CMi. This was proven by the quantification of the axon-reflex flare. Applying these stimulation paradigms during functional magnetic resonance imaging, we investigated whether nociceptor stimulation that recruits CMi leads to different cerebral activation than stimuli that do not recruit CMi. Brain activation by CMi was inferred by subtraction. Both stimuli recruited multiple afferents other than CMi, and we expected a common network of regions involved in different aspects of pain perception and motor nocifensive reactions in both stimuli. ICS that additionally recruited CMi should activate regions with low acuity that are involved in pain memory and emotional attribution. Besides a common network of pain in both stimuli, TCS activated the supplementary motor area, motor thalamic nuclei, the ipsilateral insula, and the medial cingulate cortex. These regions contribute to a pain processing loop that coordinates the nocifensive motor reaction. CMi nociceptor activation did not cause relevant activation in this loop and does not seem to play a role in withdrawal. The posterior cingulate cortex was selectively activated by ICS and is apparently important for the processing of inflammatory pain.

The influence of rate of temperature change and peak stimulus duration on pain intensity and quality

An important aspect of experimental pain research is that the assessment methods can investigate the different aspects of pain perception. The aim of the present study was to investigate the influence of rate of temperature change and peak stimulus duration on heat evoked pain intensity and quality. All stimuli were applied within the medial aspect of the anterior forearm. The rate of temperature change was varied from 1 to 16 C/s without any effect on the pain threshold. The pain threshold decreased with an increasing peak stimulus duration from 0.1 to 2 s, but not from 2 to 3 s. The pain intensity for suprathreshold stimuli (46 C, 48 C, 50 C) increased for decreasing rates and increasing duration. The pain intensity was highly correlated with the energy of the stimulus. When the rates of temperature change (1-16 C/s) are varied, no differences between pricking and burning pain were present at either low stimulus intensity (46 C) or high stimulus intensity (50 C). At low stimulus intensity (46 C), the pricking pain was not influenced by the duration (0.1-3 s), but the burning pain was intensified when the duration was increased from 1.5 to 3 s. At high intensity stimuli (50 C), the pricking pain intensified with an increased duration, whereas burning pain did not. The heat pain threshold is influenced by the peak stimulus duration, and not by the rate of temperature change. If suprathreshold stimuli are used, both the rate of temperature change and the peak stimulus duration can strongly affect the pain intensity and the pain quality. Therefore, the same stimulus modality can be used to assess the modulation of different pain intensities and of the pricking and burning pain qualities simply by varying the stimulus configuration.

Anatomy and physiology of pain

Community nurses have a pivotal role to play in managing pain. Sound knowledge of nervous system structures and physiological mechanisms involved in the perception, transmission and interpretation of pain signals, provides an important background to the decision-making processes underpinning effective pain treatment. Traditional explanations of the mechanisms involved in pain perception focus on a ìhard-wiredî system of specific pain receptors, connecting nerve pathways and centres of interpretation in the thalamus and somatosensory cortex. Whilst this approach offers helpful insights into the subject, recent scientific advances have served to expand and clarify many, previously inadequately explained, aspects of pain perception. Better understanding of primary and secondary hyperalgesia, ìwind-upî and central sensitisation has encouraged the use of pre-emptive balanced analgesic techniques, whilst identification of a whole host of neurochemical transmitters and modulators has potentiated the search for new analgesic agents. Traditional and current explanations of pain perception can enhance community nursesí understanding of acute and persistent pain problems and illustrate how to select pain therapies according to the underlying pathophysiology.

Disorders characterised by pain: a methodological review of population surveys.

OBJECTIVE--To review a series of conceptual and methodological problems encountered in surveys primarily devoted to pain disorders. CRITERIA FOR INCLUSION AND EXCLUSION OF ARTICLES--Published reports were systematically collected by electronic database searches (Medline), citations in existing publications, and through personal contacts. Relevant articles from clinical and epidemiological research on pain were included and special attention was given to epidemiological research on back pain. CONCLUSIONS--Surveys of pain disorders should be based on a multidimensional pain model that includes nociceptive input, pain perception, suffering, and pain behaviour as major components. Because of the limited applicability of diagnostic procedures or genuine "non-specificity" of pain states, or both, epidemiological surveys may result in a considerable proportion of cases without an identifiable pathophysiological basis. Staging and grading procedures for pain disorders (as distinguished from classification) may comprise various aspects of pain perception: regional distribution, pain intensity, temporal characteristics, sensory qualities, and dimensions of cognitive-emotional appraisal. Description of temporal development and chronification (staging) should refer to different components of the multidimensional pain model. Explicit a posteriori procedures for grading are preferable to implicit grading based on question wording. Evidence from several sources suggests that localistic concepts of pain may be misleading. Identification of complex pain syndromes should be one primary target for epidemiological pain surveys. Of the many factors that may impair the reliability and validity of data collected in pain surveys, recall biases seem to deserve special attention.