S111 Brain reorganization following the use of robotic hand prosthesis in four amputees

Abstract

The amputation of a hand (as of any other body part) is followed by a cascade of plastic changes on the motor and somatosensory pathways; such changes are probably contributing to the Phantom limb syndrome, a distressing situation affecting the vast majority of amputees. Although many effort, a clear explanation of the phantom syndrome is still missing and it could be considered the result of multiple contributing mechanisms acting both at peripheral and central nervous system. The typical feature of cortical plastic reorganization following limb amputations is the invasion of the “deafferented” cortex by neighbouring areas in both the primary somatosensory and the motor cortices. The degree of cortical reorganization was directly related to the magnitude of pain: the greater the remapping, the more severe the pain. On the other side, some novel evidences indicate the persistence of a certain degree of functionality of the somatosensory and motor cortices corresponding to the amputated part and recent evidences showed a correlation between the amount of functional persistence and phantom limb pain, more persistence causing more phantom limb pain. Moreover, it was recently suggested a link between this hypotheses and the aberrant peripheral activity characterized by ectopic evoked and spontaneous nerve activity. Almost all previously cited evidences are the results of non-longitudinal studies, where one or more groups of patients are analysed in a resting situation. Very few information are reported in literature explaining how plastic changes evolve during the use of prosthesis and this is particularly true considering new prototypes of bidirectional neurally hand prosthesis. These implanted neural interfaces for the peripheral nervous system have shown a remarkable potential as tools to restore the bidirectional communication between the hand prosthesis and the nerves in the residuum. In the frame of European founded projects we assessed neuroplastic changes of brain sensorimotor organization (through the assessment of cortical SEPs, MEPs, EEG source analysis, connectivity analysis and fMRI) following the use of a robotic hand during trainings of different durations (4–24 weeks) in four human amputees, providing new advancements in the understanding of the complex phenomena of phantom limb syndrome.