Visual responsiveness in sensorimotor cortex is increased following amputation and reduced after mirror therapy

Abstract

Phantom limb pain (PLP) following amputation, which is experienced by the vast majority of amputees, has been reported to be relieved with daily sessions of mirror therapy. During each session, a mirror is used to view the reflected image of the intact limb moving, providing visual feedback consistent with the movement of the missing/phantom limb. To investigate potential neural correlates of the treatment effect, we measured brain responses in volunteers with unilateral leg amputation using functional magnetic resonance imaging (fMRI) during a four-week course of mirror therapy. Mirror therapy commenced immediately following baseline scans, which were repeated after approximately two and four week intervals. We focused on responses in the region of sensorimotor cortex corresponding to primary somatosensory and motor representations of the missing leg. At baseline, prior to starting therapy, we found a strong and unexpected response in sensorimotor cortex of amputees to visually presented images of limbs. This response was stronger for images of feet compared to hands and there was no such response in matched controls. Further, this response to visually presented limbs was no longer present at the end of the four week mirror therapy treatment, when perceived phantom limb pain was also reduced. A similar pattern of results was also observed in extrastriate and parietal regions typically responsive to viewing hand actions, but not in regions corresponding to secondary somatosensory cortex. Finally, there was a significant correlation between initial visual responsiveness in sensorimotor cortex and reduction in PLP suggesting a potential marker for predicting efficacy of mirror therapy. Thus, enhanced visual responsiveness in sensorimotor cortex is associated with PLP and modulated over the course of mirror therapy.

Recent advances in understanding and managing phantom limb pain

“…MT is a long-standing treatment for PLP 33 and is thought to reduce PLP by restoring normal somatosensory and visual inputs to associated brain structures, although the precise mechanisms by which this occurs are not well understood 20 . A recent neuroimaging study of lower limb amputees with PLP found enhanced responsiveness to viewing images of feet (but not hands) in the foot area of sensorimotor cortex contralateral to the amputated limb as well as in posterior parietal cortex 34 . Both PLP intensity and the increased visual responsiveness were abolished after 4 weeks of MT.…”

Body illusions for mental health: a systematic review

“…The reviewed studies in this systematic review also showed that the MBI had been widely used as an effective BOI toward a body part to reduce pain perception in patients with an amputation (Anaforoğlu Külünkoğlu et al, 2019;Chan et al, 2019;Darnall and Li, 2012;Diers et al, 2010;Finn et al, 2017;Kazemi et al, 2015;Ol et al, 2018;Ramadugu et al, 2017;Rothgangel et al, 2018;Tilak et al, 2016;Tung et al, 2014;Yildirim and Kanan, 2016). Indeed, the first clinical application of the MBI has been for pain relief in patients with phantom pain limb because of an amputation (Ramachandran et al, 1995).…”

“…Twenty-four studies used BIs to reduce pain perception in clinical populations (Alphonso et al, 2012;Anaforoğlu Külünkoğlu et al, 2019;Chan et al, 2019;Choi et al, 2019;Darnall & Li, 2012;Diers et al, 2010;Finn et al, 2017;Giummarra, Fitzgibbon, et al, 2010;Hwang et al, 2014;Kazemi et al, 2015;Lopez-Carballo et al, 2018;Louw et al, 2017;Matamala-gomez et al, 2018;Ol et al, 2018;Ortiz-Catalan et al, 2016;Osumi et al, 2019;Pamment & Aspell, 2017;Ramadugu et al, 2017;Reinersmann et al, 2013;Rothgangel et al, 2018;Themelis & Newport, 2018;Tilak et al, 2016;Tung et al, 2014;Yildirim & Kanan, 2016) (see table 3). Particularly, twelve studies used the MBI in amputee patients suffering from phantom pain limb (Anaforoğlu Külünkoğlu et al, 2019;Chan et al, 2019;Darnall & Li, 2012;Diers et al, 2010;Finn et al, 2017;Kazemi et al, 2015;Ol et al, 2018;Ramadugu et al, 2017;Rothgangel et al, 2018;Tilak et al, 2016;Tung et al, 2014;Yildirim & Kanan, 2016). One study used the MBI with patients with chronic stroke to decrease neck pain discomfort (Choi et ...…”

“…Two studies conducted pilot experimental studies without control group to investigate the use of the MBI for phantom pain relief (Anaforoğlu Külünkoğlu et al, 2019;Yildirim & Kanan, 2016). Two pilot studies were directed to investigate the potential neural correlates of the MBI impact on pain relief, through brain responses in volunteers with unilateral leg amputation using functional magnetic resonance imaging (fMRI) during the course of mirror therapy (Chan et al, 2019), and comparing mirroring movements with imagined or executed movements (Diers et al, 2010). Two studies compared the use of the MBI in bilateral amputee patients with an imagined movements intervention (Tung et al, 2014), and with a healthy control group (Kazemi et al, 2015).…”

“…Four studies used BOI toward a body part to investigate neurobiological responses in clinical populations (Bogdanov et al, 2012;Chan et al, 2019;Michielsen et al, 2011;Peled et al, 2003).…”