52 CHAPTER 3 rely on sensorimotor representations of their own upper limb and a first-person imagery perspective is used to solve the task. 58, 69, 70 This task has been shown to be sensitive to changes in sensorimotor representations in several asymmetric central and peripheral disorders. 31, 40, 45, 71, 72 Importantly, manipulations of the peripheral nervous system (local anesthesia and immobilization) also influence performance on this task in healthy individuals. 73, 74 Here we compared behavioral performance on the hand laterality judgment task between right-lateralized NA patients and matched healthy controls. We predicted behavioral impairments for right- but not left- hand stimuli in patients. Materials and methods We made a cross-sectional comparison of patients with NA to healthy controls. The study was approved by the local medical ethical committee (Medical Ethical Committee region Arnhem-Nijmegen, CMO2014-1435). No part of the study procedures or analyses was pre-registered prior to the research being conducted. We report how we determined our sample size, all data exclusion, all inclusion/exclusion criteria, whether inclusion/exclusion criteria were established prior to data analysis, all manipulations, and all measures in the study. Participants Twenty-one patients with a clinical diagnosis of NA and twenty-one age and sex-matched healthy control subjects participated in the study. All participants were right-handed and 18 years or older, and all participants gave written informed consent according to the Declaration of Helsinki before they participated in the study. Patients were enrolled through the specialized outpatient plexus clinic at the Radboud university medical center in Nijmegen, the Netherlands. All NA patients had clearly lateralized symptoms in the right upper limb and presented with scapular dyskinesia (i.e. abnormal motor control of the shoulder) on the affected, right side. Patients in the acute phase (i.e. < 2 months since attack onset) of the disorder were excluded. Additional exclusion criteria were the presence of passive shoulder movement limitations, the presence of other disorders that affect the ability to move the upper limb, lumbosacral plexus involvement, and the inability to give informed consent. Healthy subjects were recruited through the university’s healthy participants’ databases. They were excluded if they had a history of or current complaints in the shoulder region, a neuromuscular or a neurological disorder. These in- and exclusion criteria were established prior to the start of the study. See Table 1 for an overview of the participant characteristics. We used objective and subjective measures to quantify NA-related symptoms. Since the serratus anterior muscle is often affected in NA patients with abnormal scapular movement patterns,7 we estimated a maximal force exerted by this muscle using a manual digital dynamometer (MicroFET2®), on both the left and the right side, in both patients and controls. This was done while the arm was extended at shoulder level in the scapular plane. 75 Furthermore, patients filled out two common questionnaires to assess functional capability of the affected upper limb. First, the Shoulder Rating Questionnaire, Dutch Language Version (SRQ-DLV) assesses functional capability of the shoulder, arm and hand. It is a reliable and validated questionnaire34 that has been shown to be sensitive in this patient population. 1 The SRQ-DLV consists of a visual analogue scale and 19 multiple
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