Some chronic low back pain (CLBP) patients report an expanded perceived image of the low back using words like: “My back feels like it’s swollen”. Altered perceived body image is associated with chronic pain conditions such as complex regional pain syndrome (CRPS) (Moseley, 2005; Lewis and Schweinhardt, 2012) and phantom limb pain (Flor et al., 2006). Moseley (2008) reported that altered body image and decreased tactile acuity are also associated with CLBP. However, it is unclear whether low back pain and tactile acuity are related to differences in perceived image of the low back.
So, our group investigated the relationship between perceived image of the low back and the differences in two-point discrimination (TPD) (Nishigami et al, 2015) in people with CLBP and healthy controls.
Forty-two patients with CLBP and seventeen healthy individuals were recruited. We evaluated perceived body image, TPD and clinical profiles. The perceived image of the low back was constructed as follows: patients were instructed to draw the outline of their back and, while looking at the picture were asked “In fact, do you feel this perceived image is normal, expanded, or shrunken?” The author checked whether the perceived body line drawn by the patient shifted from the line that connected the top and bottom on each side. When the line drawing was consistent with the mental image, the patient was classified as normal, expanded, or shrunken.
Of the patients with CLBP, 42.8% were classified as normal and the remaining 57.2% were evenly classified as 28.6% expanded and 28.6% shrunken perceived body image. Interestingly, although the TPD distance threshold in shrunken subgroup was not significantly different compared with other subgroup, the TPD distance threshold was significantly larger for the expanded subgroup compared with the control and normal subgroups. These results may indicate that the possibility of somatosensory change is relatively greater when the perceived image of the low back is expanded. Many studies have shown that somatosensory cortex reorganization might contribute to pain (Flor et al.,1995; Pleger et al., 2004, 2006). McCabe et al. (2005) reported that a disturbance in sensory and motor function may induce sensorimotor incongruence and produce pain, discomfort and other sensations in healthy volunteers. Poor sensory function and distorted image are likely to contribute to discrepancies between sensory and motor performance. Therefor, sensorimotor incongruence may be associated with distorted perceived image of the low back in CLBP patients.
In our study, differences in perceived body image were not associated with clinical symptoms. It is possible that CLBP outcomes are not as strongly associated with psychological factors as other pain conditions might be and hence sensorimotor incongruence alone may not induce discomfort. Peltz et al. (2011) reported that the magnitude of body image distortion correlates with disease duration and decreased tactile acuity in patients with CRPS. What is the difference CLBP and CRPS? The disability and pain severity were more strongly associated with psychological factors in the CRPS than the CLBP (Bean et al, 2014). We found that the cingulate cortex, which is pain- and discomfort-related brain region, is more activated in the high-discomfort subgroup than in the no-discomfort subgroup during sensorimotor incongruence in healthy volunteer (Nishigami et al, 2014). That is, sensorimotor incongruence-induced discomfort is not associated with only sensory-motor mismatch, but also may be associated with characteristic (psychological factors). Therefore, CLBP patients with distorted body image may not feel discomfort during sensorimotor incongruence (e.g., movement) than CRPS patients. We need to examine whether CLBP patients with distorted body image feel discomfort during trunk movement.
Another method for evaluating disturbance of body-perception in the clinical setting has been reported. Wand et al. (2014) reported that altered body perception in patients with CLBP was detected by back-specific self-report questionnaires (FreBaQ). Altered body perception score in FreBaQ was correlated with clinical symptoms. This questionnaire might be one of standard evaluation of disturbance of body-perception in the future.
Do we have any rehabilitation techniques that might help people with altered body image? Gilpin et al. (2014) reported that illusory stretching using Newport MIRAGE multisensory illusions system increased perceived hand size in patients with painful hand osteoarthritis who reported that their hands felt small. This raises the possibility that treatment using multisensory illusions might be worth further investigation in CLBP patients who feel an expanded image of the low back.
About Tomohiko Nishigami
Tomo is a Japanese physiotherapist and works as an Associate Professor in Konan Woman’s University. He also works at the Pain Center, Osaka University Hospital. He completed his Ph.D. in 2014 at The Aichi Medical University. He is interested in the relationships between pain, body perception and brain. His goal is to clinically apply neuroscience informed rehabilitation and advance patient education in Japan.
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