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BackgroundIncreasing recent evidence has implicated osteoporosis as a risk factor for benign paroxysmal positional vertigo (BPPV). We conducted a systematic review to examine the association between osteoporosis and BPPV.MethodsFour electronic databases (PubMed, EMBASE, Cochrane Library, and the China Network Knowledge Infrastructure) were searched to identify all papers, published in either English or Chinese, examining the association between osteoporosis (osteopenia) and BPPV.ResultsSeven studies were eligible for analysis, though these studies included some weaknesses. Most of the studies demonstrated a correlation between osteoporosis (osteopenia) and the occurrence and recurrence of BPPV, especially in older women. Patients with osteoporosis may require more canalith-repositioning procedures.ConclusionsThis systematic review provides insight into currently available evidence and elucidates the possible existence of an association between BPPV and osteoporosis (osteopenia). However, the evidence supporting that conclusion is not strong, and further studies are needed to clarify the association between these conditions.

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The central nervous system produces movements by activating specifically programmed muscle synergies that are also altered with injuries in the brain, such as stroke. In this study, we hypothesize that there exists a positive correlation between task-specific muscle synergy and motor functions at joint and task levels in patients following stroke. The purpose here is to define and evaluate neurophysiological metrics based on task-specific muscle synergy for assessing motor functions in patients. A patient group of 10 subjects suffering from stroke and a control group of nine age-matched healthy subjects were recruited to participate in this study. Electromyography (EMG) signals and movement kinematics were recorded in patients and control subjects while performing arm reaching tasks. Muscle synergies of individual patients were extracted off-line from EMG records of each patient, and a baseline pattern of muscle synergy was obtained from the pooled EMG data of all nine control subjects. Peak velocities and movement durations of each reaching movement were computed from measured kinematics. Similarity indices of matching components to those of the baseline synergy were defined by synergy vectors and time profiles, respectively, as well as by a combined similarity of vector and time profile. Results showed that pathological synergies of patients were altered from the characteristics of baseline synergy with missing components, or varied vector patterns and time profiles. The kinematic performance measured by peak velocities and movement durations was significantly poorer for the patient group than the control group. In patients, all three similarity indices were found to correlate significantly to the kinematics of movements for the reaching tasks. The correlation to the Fugl-Meyer score of arm was the highest with the vector index, the lowest with the time profile index, and in between with the combined index. These findings illustrate that the analysis of task-specific muscle synergy can provide valuable insights into motor deficits for patients following stroke, and the task-specific similarity indices are useful neurophysiological metrics to predict the function of neuromuscular control at the joint and task levels for patients.