Do Mirror Glasses Have the Same Effect on Brain Activity as a Mirror Box? Evidence from a Functional Magnetic Resonance Imaging Study with Healthy Subjects

Milde C, Rance M, Kirsch P, et al. Do Mirror Glasses Have the Same Effect on Brain Activity as a Mirror Box? Evidence from a Functional Magnetic Resonance Imaging Study with Healthy Subjects. PLOS ONE. 2015;10(5): e0127694

Phantom limb pain after unilateral arm amputation is associated with decreased heat pain thresholds in the face

BACKGROUND The mechanisms underlying chronic phantom limb pain (PLP) are complex and insufficiently understood. Altered sensory thresholds are often associated with chronic pain but quantitative sensory testing (QST) in PLP has so far been inconclusive due to large methodological variation between studies and small sample sizes. METHODS In this study, we applied QST in 37 unilateral upper-limb amputees (23 with and 14 without PLP) and 19 healthy controls. We assessed heat pain (HPT), pressure pain, warmth detection and two-point discrimination thresholds at the residual limb, a homologous point and the thenar of the intact limb as well as both corners of the mouth. RESULTS We did not find significant differences in any of the thresholds between the groups. However, PLP intensity was negatively associated with HPT at all measured body sites except for the residual limb, indicating lower pain thresholds with higher PLP levels. Correlations between HPT and PLP were strongest in the contralateral face (r = -0.65, p < 0.001). Facial HPT were specifically associated with PLP, independent of residual limb pain (RLP) and various other covariates. HPT at the residual limb, however, were significantly associated with RLP, but not with PLP. CONCLUSION We conclude that the association between PLP and, especially facial, HPT could be related to central mechanisms. SIGNIFICANCE Phantom limb pain (PLP) is still poorly understood. We show that PLP intensity is associated with lower heat pain thresholds, especially in the face. This finding could be related to central nervous changes in PLP

Phantom limb pain after unilateral arm amputation is associated with decreased heat pain thresholds in the face

Fuchs X, Diers M, Trojan J, et al. Phantom limb pain after unilateral arm amputation is associated with decreased heat pain thresholds in the face. European journal of pain. Accepted.The mechanisms underlying chronic phantom limb pain (PLP) are complex and insufficiently understood. Altered sensory thresholds are often associated with chronic pain but quantitative sensory testing (QST) in PLP has so far been inconclusive due to large methodological variation between studies and small sample sizes. In this study, we applied QST in 37 unilateral upper-limb amputees (23 with, 14 without PLP) and 19 healthy controls. We assessed heat pain (HPT), pressure pain (PPT), warmth detection (WDT), and two-point discrimination thresholds at the residual limb, a homologous point and the thenar of the intact limb as well as both corners of the mouth. We did not find significant differences in any of the thresholds between the groups. However, PLP intensity was negatively associated with HPT at all measured body sites except for the residual limb, indicating lower pain thresholds with higher PLP levels. Correlations between HPT and PLP were strongest in the contralateral face (r = -0.65, p < 0.001). Facial HPT were specifically associated with PLP, independent of residual limb pain (RLP) and various other covariates. HPT at the residual limb, however, were significantly associated with RLP, but not with PLP. We conclude that the association between PLP and, especially facial, HPT could be related to central mechanisms. This article is protected by copyright. All rights reserved

Illusion-related brain activations: A new virtual reality mirror box system for use during functional magnetic resonance imaging

Diers M, Kamping S, Kirsch P, et al. Illusion-related brain activations: A new virtual reality mirror box system for use during functional magnetic resonance imaging. Brain Research. 2014;1594:173-182

The Importance of Synchrony and Temporal Order of Visual and Tactile Input for Illusory Limb Ownership Experiences – An fMRI Study Applying Virtual Reality

Bekrater-Bodmann R, Foell J, Diers M, et al. The Importance of Synchrony and Temporal Order of Visual and Tactile Input for Illusory Limb Ownership Experiences – An fMRI Study Applying Virtual Reality. PLoS ONE. 2014;9(1): e87013

Mirror visual feedback (MVF) devices.

<p>(A) Mirror glasses: are usable within an MR environment. The optical path was deflected by a prism, which was a 1.5–1.53 45-90-45 angled glass, Barium crown (BK-7, Abbe 63) with quarter wavelength surface tolerance. (B) Mirror box: was a framed glass mirror (size: 35 by 12 centimetres / 13.8 by 4.7 inches) which was placed on the abdomen of the subject providing view on the executing hand as well as the visual reflection of the hand appearing to move in synchrony. During both conditions view on the mirror reflection of the moving limb was provided by means of an additional mirror attached to the head coil. (C) Illustration of the MVF as provided by the mirror glasses: in contrast to the mirror box the users’ view is limited to the mirror reflection of the moving (physical) hand as opposed to seeing both hands (physical hand and visual reflection of the physical hand). The mirror reflection of the physical hand was seen through on eye by means of a prism leading to a total inversion in the left-right dimension (in our setup the right hand movements were seen through the right eye appearing as left hand movements). Furthermore, mirror glasses provide a much larger field of view, allowing the whole limb to be inverted.</p

Ratings on the intensity and vividness of mirror illusions for the mirror box and mirror glasses conditions.

<p>Results are reported with Mean ± Standard Deviation of the Mean (<i>M</i> ± <i>SD</i>). Comparisons of the two items between conditions were conducted with paired sample <i>t</i>-tests with Bonferroni adjusted alpha-values of 0.025 (0.05/2). Numerical rating scale ranging from 1 (‘as clear and vivid as a real perceptual experience’) to 7 (‘not at all clear and vivid’).</p><p>Ratings on the intensity and vividness of mirror illusions for the mirror box and mirror glasses conditions.</p