Mirror Therapy in Lower Limb Amputees – A Look Beyond Primary Motor Cortex Reorganization

Zusammenfassung

Ziel: Untersuchungen an Armamputierten konnten einen Zusammenhang zwischen Reorganisation im primären sensomotorischen Kortex und Phantomschmerz zeigen. Die Spiegeltherapie wird als nicht invasives Therapieverfahren zur Behandlung von Phantomschmerzen eingesetzt. Ziel dieser Studie war die Untersuchung kortikaler Reorganisationsphänomene vor und nach Spiegeltherapie bei Beinamputierten. Material und Methoden: Acht Beinamputierte absolvierten 12 Spiegeltherapiesitzungen, bei denen repetitive Extensions- und Flexionsbewegungen der gesunden unteren Extremität durchgeführt wurden. Vor der ersten und nach der letzten Therapiesitzung wurden fMRT-Messungen durchgeführt, bei denen die funktionelle Organisation repetitiver Bewegungen im gesunden und amputierten Sprunggelenk getestet wurde. Ergebnisse: Die mittlere Intensität des subjektiven Phantomschmerzes betrug vor der Spiegeltherapie 4,6 ± 3,1 auf einer visuellen Analogskala und verringerte sich auf 1,8 ± 1,7 (p = 0,04) nach der Therapie. Es konnten keine konsistenten Aktivierungen des primären sensomotorischen Kortex während der Bewegungen des Phantomsprunggelenks im Vergleich zur Ruhebedingung nachgewiesen werden. Nach der Spiegeltherapie zeigten die Patienten erhöhte Aktivität im rechten orbitofrontalen Kortex während Bewegungen des Phantomsprunggelenks. Der Vergleich zwischen Bewegungen des gesunden und des Phantomsprunggelenks zeigte eine signifikant höhere Aktivität im linken inferioren frontalen Kortex (Pars triangularis). Schlussfolgerung: Diese Ergebnisse stellen den bisher bekannten Zusammenhang zwischen kortikaler Reorganisation im primären sensomotorischen Kortex und Phantomschmerzen infrage und weisen auf die Veränderungen im sogenannten „Motor-Netzwerk“ hin. Die Phantomschmerzreduktion nach Spiegeltherapie wurde von einer erhöhten präfrontalen kortikalen Aktivität begleitet.

Abstract

Purpose: Phantom pain in upper limb amputees is associated with the extent of reorganization in the primary sensorimotor cortex. Mirror visual feedback therapy has been shown to improve phantom pain. We investigated the extent of cortical reorganization in lower limb amputees and changes in neural activity induced by mirror therapy. Materials and Methods: Eight lower limb amputees underwent 12 sessions of MVFT and functional magnetic resonance imaging (fMRI) of the brain before the first and after the last MVFT session. FMRI sessions consisted of two runs in which subjects were instructed to perform repetitive movement of the healthy and phantom ankle. Results: Before MVFT, the mean phantom pain intensity was 4.6 ± 3.1 on a visual analog scale and decreased to 1.8 ± 1.7 (p = 0.04). We did not observe a consistent pattern of cortical activation in primary sensorimotor areas during phantom limb movements. Following MVFT, increased activity was obtained in the right orbitofrontal cortex during phantom ankle movements. Comparison of cortical activity during movements of the phantom ankle and the intact ankle showed significantly higher activity in the left inferior frontal cortex (pars triangularis). Conclusion: These results question the known association between phantom pain and primary sensorimotor reorganization and propose reorganizational changes involving multiple cortical areas in lower limb amputees. Finally, reduction of phantom pain after mirror visual feedback therapy was associated with increased prefrontal cortical activity during phantom ankle movements.

MR functional imaging - neural networks - brain

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