113 CEREBRAL ADAPTATION ASSOCIATED WITH PERIPHERAL NERVE RECOVERY IN NA 6 Introduction When components of the sensorimotor system are injured, motor function can be recovered through adaptations within the nervous system. 12 However, these plastic adaptations are not always beneficial to clinical outcome, and can even contribute to subsequent motor dysfunction. Such maladaptive plasticity has been connected to persistent motor impairment in several central and peripheral nervous system disorders. 12 Reversal of maladaptation following injury may form a promising avenue for rehabilitation, especially in peripheral nervous system disorders where central structures are intact. One such disorder is neuralgic amyotrophy (NA): a common (incidence of 1:1000) and disabling peripheral nerve disorder, characterized by acute autoimmune inflammation of the nerves in the brachial plexus territory, which leads to paresis of muscles innervated by damaged nerves. 3, 6 NA is typically asymmetric, most often affecting one upper extremity. 7 To compensate for muscle weakness, many patients develop abnormal movement patterns, most notably of the shoulder (i.e. scapular dyskinesia), which can be beneficial at first, but lead to long-term motor dysfunction and subsequent residual complaints of the affected limb, even with (partial) peripheral recovery. 6, 8 Recently, we have empirically confirmed our clinical suspicion6, 124 that NA patients with peripheral nerve damage and residual motor dysfunction have abnormal cerebral sensorimotor representations related to their affected limb and residual symptoms. 2 The objective of the current study is to determine whether the cerebral abnormalities associated with NA can be modified by specialized, multidisciplinary outpatient rehabilitation, 1, 6 as compared to usual care. Whereas usual care commonly involves conventional physical therapy focused on regaining strength and endurance, 6, 8 multidisciplinary rehabilitation combines occupational and physical therapy, and focusses on improving self-management strategies and relearning motor control to normalize scapular movement and stability. 1, 6 We hypothesize that multidisciplinary rehabilitation, but not usual care, can modify abnormal cerebral sensorimotor representations of the affected upper extremity. As a secondary objective, we explore how cerebral changes relate to changes in clinical symptoms: functional capability of the upper extremity, and persistent pain, which strongly relates to scapular dyskinesia in NA. 6, 8, 10 To reach our objectives, we use a combination of task-based functional MRI (fMRI) and the hand laterality judgment task, for its ability to activate sensorimotor representations of the upper extremity25, 29, 86 and its sensitivity to cerebral and behavioral adaptations in NA. 2, 122 In this validated task, patients judge the laterality (left or right) of hand stimuli, by mentally rotating their own body part to match the stimulus. This involves “motor imagery” (i.e. mental simulation of movement) and engages sensorimotor processes similar to motor planning. 24, 86 The embodied nature of the task is confirmed by the fact that subjects incorporate their own body posture. 58, 69 Motor imagery activates a frontoparieto-occipital network involving key motor areas such as the supplementary motor area and premotor cortex, as well as visuomotor areas in the posterior parietal cortex and along the dorsal visual stream. 21, 24, 40, 58 This activation is typically more pronounced for imagined movements rotating away from the body midline, which pose complex biomechanical constraints, compared to movements rotating towards the body midline that are easier to perform as they pose fewer biomechanical constraints. 25, 29, 58 We have