Abstract
BackgroundChronic pain enhances sensory sensitivity and induces the biased development of psychological traits such as depression and pain catastrophizing, leading to the formation of heterogeneous conditions. Fluctuations in the sensory-related thresholds of non-injured sites (with normal peripheral tissue) in patients with chronic pain are thought to be related to central sensitization. The objectives of this study were to analyze the association between pain tolerance thresholds (PTTs) in non-injured sites and the psychological traits of patients with chronic pain and to evaluate the usefulness of PTT measures in assessments of pathological conditions related to chronic pain.MethodsThis study included 57 patients with chronic pain. The PTTs were measured in non-injured sites with quantitative sensory testing (QST) with electrical stimulation and then classified with cluster analysis. The Short-Form McGill Pain Questionnaire was used to subjectively assess pain in the injured sites. The Minnesota Multiphasic Personality Inventory (MMPI) was used to assess the patients’ psychological traits.ResultsBased on the cluster analysis of PTTs, the patients were classified into a High-Sensitivity group and an Others group consisting of the remaining patients. The results of the MMPI profiles showed that the High-Sensitivity group included significantly more patients with the Neurotic Triad pattern and no patients with the Conversion V pattern. The scores of the hypochondriasis and hysteria scales were significantly lower in the High-Sensitivity group than in the Others group.ConclusionsThis study indicated that patients with chronic pain can be classified according to PTTs in non-injured sites and suggests that patients with High-Sensitivity have characteristic psychological traits. Assessment of PTTs in non-injured sites would be useful for evaluating the psychological condition of patients with chronic pain.
Highlights
Chronic pain enhances sensory sensitivity and induces the biased development of psychological traits such as depression and pain catastrophizing, leading to the formation of heterogeneous conditions
In order to evaluate the usefulness of pain threshold measures as a tool for assessing heterogeneous pathological conditions that involve chronic pain, this study aimed to clarify the association between pain thresholds in non-injured sites and the psychological traits of patients with chronic pain
This study had two important findings: these measurements differentiated a HighSensitivity group of patients who showed substantial decreases in their Pain tolerance threshold (PTT), and assessment with the Minnesota Multiphasic Personality Inventory (MMPI) revealed psychological traits that were characteristic of the patients with chronic pain, some of which have been reported by previous studies
Summary
Chronic pain enhances sensory sensitivity and induces the biased development of psychological traits such as depression and pain catastrophizing, leading to the formation of heterogeneous conditions. The objectives of this study were to analyze the association between pain tolerance thresholds (PTTs) in non-injured sites and the psychological traits of patients with chronic pain and to evaluate the usefulness of PTT measures in assessments of pathological conditions related to chronic pain. The following three in vivo mechanisms transform acute pain into chronic pain: peripheral sensitization at the peripheral level, dysfunction of the descending pain inhibitory system, and central sensitization at the central level [10,11,12,13] These mechanisms enhance pain at sites of tissue damage and frequently induce the appearance of spontaneous pain or changes in the sensory sensitivity of non-injured sites to stimulation [8, 14, 15]
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