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Background: The awareness is growing that central sensitization is of prime importance for the assessment and management of chronic pain, but its classification is challenging clinically since no gold standard method of assessment exists. Objectives: Designing the first set of classification criteria for the classification of central sensitization pain. Methods: A body of evidence from original research papers was used by 18 pain experts from 7 different countries to design the first classification criteria for central sensitization pain. Results: It is proposed that the classification of central sensitization pain entails 2 major steps: the exclusion of neuropathic pain and the differential classification of nociceptive versus central sensitization pain. For the former, the International Association for the Study of Pain diagnostic criteria are available for diagnosing or excluding neuropathic pain. For the latter, clinicians are advised to screen their patients for 3 major classification criteria, and use them to complete the classification algorithm for each individual patient with chronic pain. The first and obligatory criterion entails disproportionate pain, implying that the severity of pain and related reported or perceived disability are disproportionate to the nature and extent of injury or pathology (i.e., tissue damage or structural impairments). The 2 remaining criteria are 1) the presence of diffuse pain distribution, allodynia, and hyperalgesia; and 2) hypersensitivity of senses unrelated to the musculoskeletal system (defined as a score of at least 40 on the Central Sensitization Inventory). Limitations: Although based on direct and indirect research findings, the classification algorithm requires experimental testing in future studies. Conclusion: Clinicians can use the proposed classification algorithm for differentiating neuropathic, nociceptive, and central sensitization pain. Key words: Chronic pain, diagnosis, hypersensitivity, classification, neuropathic pain

Chronic pelvic pain (CPP) is a complex pain syndrome. Since its pathogenesis is still poorly understood and structural alterations in pain related brain regions may be present, there is a greater acceptance that sensitization of the central nervous system (CNS) plays an important role in the development and maintenance of chronicity.The purpose of this study is to systematically review the scientific evidence regarding central sensitization (CS) in female patients with urogynecological CPP.Systematic review of the literature.A systematic literature search was conducted in PubMed and Web of Science using different keyword combinations related to urogynecological CPP and central sensitization. Full text clinical reports addressing CS in adult women with urogynecological CPP were included and assessed for methodological quality by 2 independent reviewers.After screening for the eligibility, a total of 29 full-text articles with low to good methodological quality were retained. All studies were observational, 27 of which were case-control and 2 of which were cohorts. Sensitivity of the CNS was investigated by using a variety of methods. Although different central mechanisms seem to be involved in pain processing, the present evidence suggests hyperexcitability of the CNS in patients with urogynecological CPP. Altered brain morphology and function, generalized hyperalgesia to different type of stimuli, overactive bottom-up nociceptive mechanisms, and autonomic dysregulation were established in patients with urogynecological CPP. Nevertheless, diffuse noxious inhibitory control seemed normal, and therefore the contribution of an impaired endogenous pain inhibition mechanism to CPP requires further study. The same goes for the contribution of psychological factors.The level of evidence of retained studies is low due to the observational study designs and a wide range of diagnoses and assessment methods.Although the majority of the literature provides evidence for the presence of CS in urogynecological CPP with changes in brain morphology/function and sensory function, it is unclear whether these changes in central pain processing are secondary or primary to CPP, especially since evidence regarding the function of endogenous pain inhibition and the role of psychosocial pain facilitation is scarce. Further studies with good methodological quality are needed in order to clarify exact mechanisms.

Background: Sensory and motor system dysfunctions have been documented in a proportion of patients with acute whiplash associated disorders (WAD). Sensorimotor incongruence may occur and hence, may explain pain and other sensations in the acute stage after the trauma. Objectives: The present study aimed at 1) evaluating whether a visually mediated incongruence between sensory feedback and motor output increases symptoms and triggers additional sensations in patients with acute WAD, 2) investigating whether the pattern of sensations in response to sensorimotor incongruence differs among patients suffering from acute and chronic WAD, and healthy controls. Study Design: Experimental study. Setting: Patients with acute WAD were recruited within one month after whiplash injury via the emergency department of a local Red Cross medical care unit, the Antwerp University Hospital, and through primary care practices. Patients with chronic WAD were recruited through an advertisement on the World Wide Web and from the medical database of a local Red Cross medical care unit. Healthy controls were recruited from among the university college staff, family members, and acquaintances of the researchers. Methods: Thirty patients with acute WAD, 35 patients with chronic WAD, and 31 healthy persons were subjected to a coordination test. They performed congruent and incongruent arm movements while viewing a whiteboard or mirror. Results. Twenty-eight patients with acute WAD reported sensations such as pain, tightness, feeling of peculiarity, and tiredness at some stage of the test protocol. No significant differences in frequencies and intensities of sensations were found between the various test stages (P > .05). Significantly more sensations were reported during the incongruent mirror stage compared to the incongruent control stage (P < .05). The pattern in intensity of sensations across the congruent and incongruent stages was significantly different between the WAD groups and the control group. Limitations: The course and prognostic value of susceptibility to sensorimotor incongruence after an acute whiplash trauma are not yet clear from these results. A prospective longitudinal study with an expanded study population is needed to investigate if those with a lowered threshold to visually mediated sensorimotor incongruence in the acute stage are at risk to develop persistent pain and disability. Conclusion: Patients with acute WAD present an exacerbation of symptoms and additional sensations in response to visually mediated changes during action. These results indicate an altered perception of distorted visual feedback and suggest altered central sensorimotor nervous system processing in patients with acute WAD. Key words: Sensorimotor incongruence, visually mediated changes, whiplash, sensations, acute pain, chronic pain, altered central sensorimotor processing, central nervous system.