Tactile localization accuracy at the low back

Localizing tactile stimulation is an important capability for everyday function and may be impaired in people with persistent pain. This study sought to provide a detailed description of lumbar spine tactile localization accuracy in healthy individuals. Sixty-nine healthy participants estimated where they were touched at nine different points, labelled in a 3 × 3 grid over the lumbar spine. Mislocalization between the perceived and actual stimulus was calculated in horizontal (x) and vertical (y) directions, and a derived hypotenuse (c) mislocalization was calculated to represent the direct distance between perceived and actual points. In the horizontal direction, midline sites had the smallest mislocalization. Participants exhibited greater mislocalization for left- and right-sided sites, perceiving sites more laterally than they actually were. For all vertical values, stimulated sites were perceived lower than reality. A greater inaccuracy was observed in the vertical direction. This study measured tactile localization for the low back utilizing a novel testing method. The large inaccuracies point to a possible distortion in the underlying perceptual maps informing the superficial schema; however, further testing comparing this novel method with an established tactile localization task, such as the point-to-point method, is suggested to confirm these findings.

Inter- and Intra-Examiner Reliability Study of Two-Point Discrimination Test (TPD) and Two-Point Estimation Task (TPE) in the Sacral Area of Pain-Free Individuals

Tactile acuity is typically measured by a two-point discrimination test (TPD) and a two-point estimation task (TPE). In the back area, they are only conducted in the lumbar and cervical regions of the spine. Considering that such measurements have not been conducted in the sacral regions, the purpose of this study was to assess the inter- and intra-examiner reliability of the TPD and TPE at the level of the S3 segment. The study included 30 pain-free subjects aged 20-30 years. Tests were performed with a pair of stainless hardened digital calipers. The TPD was measured in two locations: 5 and 15 cm from the midline; for TPE both, points were located inside the measured area. Session 1 involved assessments by two examiners in 10-min intervals. Session 2 was measured by one examiner, at analogous intervals between tests. The TPD inter-rater reliability was excellent for mean measurements (ICC3.2: 0.76-0.8; ICC3.3: 0.8-0.92); the intra-rater reliability was excellent for mean measurements (ICC2.2: 0.79-0.85; ICC2.3: 0.82-0.86). The TPE inter-rater reliability was good to excellent for mean measurements (ICC3.2: 0.65-0.92; ICC3.3: 0.73-0.94); the intra-rater reliability for all studies (ICC2.1, ICC2.2, ICC2.3) was excellent (0.85-0.89). Two measurements are sufficient to achieve good reliability (ICC ≥ 0.75), regardless of the assessed body side.

Reliabilities of the Two-Point Discrimination Test and the Two-Point Estimation Test for Use in the Lumbar Spine Area in Healthy Young Adults

Two-point discrimination (TPD) testing and two-point estimation (TPE) methods are often used to determine tactile acuity, but their reliability is uncertain. Our aim in this study was to assess the reliability of TPD and TPE measurements in the same lumbar spine region of healthy young adults. Participants were 37 young adults (16 females and 21 males; age range: 20-27 years - M age = 21.65, SD = 1.9), who received two tests (TPD and TPE) to determine their tactile acuity. The tests were performed in the lumbar spine area, at the level of the L3 segment, bilaterally, with a 10-minute interval between the measurements. The first test session assessed the reliability of measurements performed by two examiners (inter-rater reliability); and, after 7 days, another examiner repeated the measurements (intra-rater reliability). The reliability of both tests was evaluated using intra-class correlation coefficients (ICC), and results revealed high intra-rater, and inter-rater repeatability for immediate administration of TPD and TPE tests (i.e, after 10 minutes) and moderate repeatability when they were performed at a 7-day interval. Thus, we confirmed high reliability of TPD and TPE assessments of tactile acuity repeated at a short time interval and moderate reliability after 7 days. There was slightly higher reliability for the TPE method.

Correlations between Age, Pain Intensity, Disability, and Tactile Acuity in Patients with Chronic Low Back Pain

Objective

Chronic low back pain is an overwhelming problem for a wide range of people and leads to tactile acuity deficits. We aimed to investigate the correlations among age, pain severity, disability, and tactile acuity in patients with chronic low back pain by using multiple tactile acuity tests.

Methods

A total of 58 participants (36.40 ± 14.95 years) with chronic low back pain were recruited, and two-point discrimination, point-to-point test, and two-point estimation were performed on their painful low back areas. The correlations between age, pain intensity, disability, and tactile acuity were characterized with Pearson's correlation coefficients. Subgroup analyses according to the median values of age, pain intensity, and disability were used to compare the intergroup difference in tactile acuity.

Results

Results illustrated significant negative associations among age, pain intensity, disability, and tactile acuity. Subgroup analyses revealed that patients with below-the-median values of age, pain intensity, and disability had better performance in tactile acuity tests than those with above-the-median values.

Conclusion

This study indicated that tactile acuity was negatively associated with age, pain intensity, and disability in young patients with chronic low back pain.

No evidence for sex differences in tactile distance anisotropy

Perceptual illusions of the distance between two touches have been used to study mental representations of the body since E. H. Weber's classic studies in the nineteenth century. For example, on many body parts tactile distance is anisotropic, with distances aligned with body width being perceived as larger than distances aligned with body length on several skin regions. Recent work has demonstrated sex differences in other distortions of mental body representations, such as proprioceptive hand maps. Given such findings, I analysed the results of 24 experiments, conducted by myself and my colleagues, measuring tactile distance anisotropy on the hand dorsum in both women and men. The results showed clear, and highly consistent anisotropy in both women and men, with no evidence for any sex difference.

Modernising tactile acuity assessment; clinimetrics of semi-automated tests and effects of age, sex and anthropometry on performance

Background

Reduced tactile acuity has been observed in several chronic pain conditions and has been proposed as a clinical indicator of somatosensory impairments related to the condition. As some interventions targeting these impairments have resulted in pain reduction, assessing tactile acuity may have significant clinical potential. While two-point discrimination threshold (TPDT) is a popular method of assessing tactile acuity, large measurement error has been observed (impeding responsiveness) and its validity has been questioned. The recently developed semi-automated ‘imprint Tactile Acuity Device’ (iTAD) may improve tactile acuity assessment, but clinimetric properties of its scores (accuracy score, response time and rate correct score) need further examination.

Aims

Experiment 1: To determine inter-rater reliability and measurement error of TPDT and iTAD assessments. Experiment 2: To determine internal consistencies and floor or ceiling effects of iTAD scores, and investigate effects of age, sex, and anthropometry on performance.

Methods

Experiment 1: To assess inter-rater reliability (ICC_(2,1)) and measurement error (coefficient of variation (CoV)), three assessors each performed TPDT and iTAD assessments at the neck in forty healthy participants. Experiment 2: To assess internal consistency (ICC_(2,k)) and floor or ceiling effects (skewness z-scores), one hundred healthy participants performed the iTAD’s localisation and orientation tests. Balanced for sex, participants were equally divided over five age brackets (18–30, 31–40, 41–50, 51–60 and 61–70). Age, sex, body mass index (BMI) and neck surface area were assessed to examine their direct (using multiple linear regression analysis) and indirect (using sequential mediation analysis) relationship with iTAD scores.

Results

Mean ICC_(2,1) was moderate for TPDT (0.70) and moderate-to-good for the various iTAD scores (0.65–0.86). The CoV was 25.3% for TPDT and ranged from 6.1% to 16.5% for iTAD scores. Internal consistency was high for both iTAD accuracy scores (ICC_(2,6) = 0.84; ICC_(2,4) = 0.86). No overt floor or ceiling effects were detected (all skewness z-scores < 3.29). Accuracy scores were only directly related to age (decreasing with increasing age) and sex (higher for men).

Discussion

Although reliability was similar, iTAD scores demonstrated less measurement error than TPDT indicating a potential for better responsiveness to treatment effects. Further, unlike previously reported for TPDT, iTAD scores appeared independent of anthropometry, which simplifies interpretation. Additionally, the iTAD assesses multiple aspects of tactile processing which may provide a more comprehensive evaluation of tactile acuity. Taken together, the iTAD shows promise in measuring tactile acuity, but patient studies are needed to verify clinical relevance.

Perception of Tactile Distance on the Back

The perceived distance between two touches is anisotropic on many parts of the body. Generally, tactile distances oriented across body width are perceived as larger than distances oriented along body length, though the magnitude of such biases differs substantially across the body. In this study, we investigated tactile distance perception on the back. Participants made verbal estimates of the perceived distance between pairs of touches oriented either across body width or along body length on (a) the left hand, (b) the left upper back, and (c) the left lower back. There were clear tactile distance anisotropies on the hand and upper back, with distances oriented across body width overestimated relative to those along body length/height, consistent with previous results. On the lower back, however, an anisotropy in exactly the opposite direction was found. These results provide further evidence that tactile distance anisotropies vary systematically across the body and suggest that the spatial representation of touch on the lower back may differ qualitatively from that on other regions of the body.

The Relationship Between Corticomotor Reorganization and Acute Pain Severity: A Randomized, Controlled Study Using Rapid Transcranial Magnetic Stimulation Mapping

OBJECTIVE

Although acute pain has been shown to reduce corticomotor excitability, it remains unknown whether this response resolves over time or is related to symptom severity. Furthermore, acute pain research has relied upon data acquired from the cranial "hotspot," which do not provide valuable information regarding reorganization, such as changes to the distribution of a painful muscle's representation within M1. Using a novel, rapid transcranial magnetic stimulation (TMS) mapping method, this study aimed to 1) explore the temporal profile and variability of corticomotor reorganization in response to acute pain and 2) determine whether individual patterns of corticomotor reorganization are associated with differences in pain, sensitivity, and somatosensory organization.

METHODS

Corticomotor (TMS maps), pain processing (pain intensity, pressure pain thresholds), and somatosensory (two-point discrimination, two-point estimation) outcomes were taken at baseline, immediately after injection (hypertonic [n = 20] or isotonic saline [n = 20]), and at pain resolution. Follow-up measures were recorded every 15 minutes until 90 minutes after injection.

RESULTS

Corticomotor reorganization persisted at least 90 minutes after pain resolution. Corticomotor depression was associated with lower pain intensity than was corticomotor facilitation (r = 0.47 [P = 0.04]). These effects were not related to somatosensory reorganization or peripheral sensitization mechanisms.

CONCLUSIONS

Individual patterns of corticomotor reorganization during acute pain appear to be related to symptom severity, with early corticomotor depression possibly reflecting a protective response. These findings hold important implications for the management and potential prevention of pain chronicity. However, further research is required to determine whether these adaptations relate to long-term outcomes in clinical populations.

Intra- and Inter-Rater Reliability of Three Measurements for Assessing Tactile Acuity in Individuals with Chronic Low Back Pain

Objective

To investigate the intra- and inter-rater reliability of three measurements on painful and pain-free sides in participants with chronic low back pain (CLBP) at different ages.

Methods

We recruited 60 participants with CLBP and divided them equally into a group of younger participants with chronic low back pain (18 ≤ age ≤ 35, Y-CLBP) and a group of older participants with chronic low back pain (36 ≤ age ≤ 65, O-CLBP). Participants were assessed by two testers within the same day (10 min interval), and one of the testers repeated the assessment program 24 h later. The intraclass correlation coefficient (ICC) was used to assess reliability. The Pearson correlation coefficient was used to analyze the correlation between tactile acuity and age, waistline, and pain-related variables.

Results

In the Y-CLBP group, the intra-rater reliability of two-point discrimination (TPD), point-to-point test (PTP), and two-point estimation (TPE) on the painful and pain-free sides was good (ICC range: 0.74–0.85), whereas the inter-rater reliability of TPD, PTP, and TPE on the painful and pain-free sides was moderate to good (ICC range: 0.65–0.76). In the O-CLBP group, the intra-rater reliability of TPD, PTP, and TPE on the painful and pain-free sides was good (ICC range: 0.75–0.85), whereas the inter-rater reliability of TPD, PTP, and TPE on the painful and pain-free sides was moderate to good (ICC range: 0.70–0.85). Age, waistline, duration of pain, maximum pain, general pain, and unpleasant score caused by pain were positively correlated with tactile acuity thresholds (D-TPD, A-TPD, PTP, and TPE) (r > 0.365, p < 0.05). When BMI was controlled, age, waistline, and pain-related variables were positively correlated with tactile acuity thresholds (r > 0.388; p < 0.05).

Conclusion

In the participants of Y-CLBP and O-CLBP groups, TPD, PTP, and TPE have moderate-to-good intra- and inter-rater reliability on the painful and pain-free sides of the fifth lumbar vertebrae.

Explicit and Implicit Own's Body and Space Perception in Painful Musculoskeletal Disorders and Rheumatic Diseases: A Systematic Scoping Review

Background: Pain and body perception are essentially two subjective mutually influencing experiences. However, in the field of musculoskeletal disorders and rheumatic diseases we lack of a comprehensive knowledge about the relationship between body perception dysfunctions and pain or disability. We systematically mapped the literature published about the topics of: (a) somatoperception; (b) body ownership; and (c) perception of space, analysing the relationship with pain and disability. The results were organized around the two main topics of the assessment and treatment of perceptual dysfunctions.

Methods: This scoping review followed the six-stage methodology suggested by Arksey and O'Malley. Ten electronic databases and grey literature were systematically searched. The PRISMA Extension for Scoping Reviews was used for reporting results. Two reviewers with different background, independently performed study screening and selection, and one author performed data extraction, that was checked by a second reviewer.

Results: Thirty-seven studies fulfilled the eligibility criteria. The majority of studies (68%) concerned the assessment methodology, and the remaining 32% investigated the effects of therapeutic interventions. Research designs, methodologies adopted, and settings varied considerably across studies. Evidence of distorted body experience were found mainly for explicit somatoperception, especially in studies adopting self-administered questionnaire and subjective measures, highlighting in some cases the presence of sub-groups with different perceptual features. Almost half of the intervention studies (42%) provided therapeutic approaches combining more than one perceptual task, or sensory-motor tasks together with perceptual strategies, thus it was difficult to estimate the relative effectiveness of each single therapeutic component.

Conclusions: To our knowledge, this is the first attempt to systematically map and summarize this research area in the field of musculoskeletal disorders and rheumatic diseases. Although methodological limitations limit the validity of the evidence obtained, some strategies of assessment tested and therapeutic strategies proposed represent useful starting points for future research. This review highlights preliminary evidence, strengths, and limitations of the literature published about the research questions, identifying key points that remain opened to be addressed, and make suggestions for future research studies. Body representation, as well as pain perception and treatment, can be better understood if an enlarged perspective including body and space perception is considered.