Balance impairments after brachial plexus injury as assessed through clinical and posturographic evaluation

Objective: To investigate whether a sensorimotor deficit of the upper limb following a brachial plexus injury (BPI) affects the upright balance. Design: Eleven patients with a unilateral BPI and 11 healthy subjects were recruited. The balance assessment includes the Berg Balance Scale (BBS), the number of feet touches on the ground while performing a 60s single-leg stance and posturographic assessment (eyes open and feet placed hip-width apart during a single 60s trial). The body weight distribution (BWD) between the legs was estimated from the center of pressure (COP) lateral position. The COP variability was quantified in the anterior-posterior and lateral directions.Results: BPI patients presented lower BBS scores (p=0.048) and a higher frequency of feet touches during the single-leg stance (p=0.042) compared with those of the healthy subjects. An asymmetric BWD toward the side opposite the affected arm was showed by 73% of BPI patients. Finally, higher COP variability was observed in BPI patients compared with healthy subjects for anterior-posterior (p=0.020), but not for lateral direction (p=0.818).Conclusions: This study demonstrates that upper limb sensorimotor deficits following BPI affect body balance, serving as a warning for the clinical community about the need to prevent and treat the secondary outcomes of this condition

Motor imagery modulation of body sway is task-dependent and relies on imagery ability

AbstractIn this study we investigate to what extent the effects of motor imagery on postural sway are constrained by movement features and the subject’s imagery ability. Twenty-three subjects were asked to imagine three movements using the kinesthetic modality: rising on tiptoes, whole-body forward reaching, and whole-body lateral reaching. After each task, subjects reported the level of imagery vividness and were subsequently grouped into a HIGH group (scores ≥3, moderately intense imagery) or a LOW group (scores ≤2, mildly intense imagery). An eyes closed trial was used as a control task. Center of gravity (COG) coordinates were collected, along with surface EMG of the deltoid (medial and anterior portion) and lateral gastrocnemius muscles. COG variability was quantified as the amount of fluctuations in position and velocity in the forward-backward and lateral directions. Changes in COG variability during motor imagery were observed only for the HIGH group. COG variability in the forward-backward direction was increased during the rising on tiptoes imagery, compared with the control task (p=0.01) and the lateral reaching imagery (p=0.02). Conversely, COG variability in the lateral direction was higher in rising on tiptoes and lateral reaching imagery than during the control task (p0.08) or task (p>0.46) for any of the tested muscles. In summary, motor imagery influences body sway dynamics in a task-dependent manner, and relies on the subject’ imagery ability.<br/