Brain networks associated with anticipatory postural adjustments in Parkinson's disease patients with freezing of gait.

Specific impairments of anticipatory postural adjustment (APA) during step initiation have been reported in patients with Parkinson's disease (PD) and freezing of gait (FoG). Although APA disruption has been associated with FoG, there is scarce knowledge about its neural correlates. We sought to better understand the neural networks involved with APA in patients with FoG by assessing the level of hemodynamic response of specific brain regions and the functional connectivity during the leg lifting task. In the current investigation, APAs of patients with PD, with and without (nFoG) freezing were assessed during a leg lifting task in an event-related, functional magnetic resonance imaging (er-fMRI) protocol. Results identified a high hemodynamic response in the right anterior insula (AI) and supplementary motor area (SMA) in the FoG group when an APA was required. The nFoG had stronger connectivity between the right and left insulae than the FoG group. The strength of this connectivity was negatively correlated with the severity of FoG. Both groups showed different brain network organizations comprising the SMA and the bilateral AI. The SMA was found to be a hub in patients with FoG when an APA was required for the task. Our findings suggest that both groups used compensatory mechanism comprising the insulae during APA. Neither group used the entire network comprised of the insulae and SMA to accomplish the task. The FoG group relied more on SMA as a hub than as part of a broader network to exchange information during the APA.

The impact of surgical breast reduction on the postural control of women with breast hypertrophy.

BACKGROUND: Previous studies have demonstrated the impact of breast reduction surgery on the daily lives of women, including impacts directly related to changes in postural control such as a reduced center-of-pressure displacement. However, postural control is a dynamic process that depends on the integration of sensory information to organize a proper motor strategy to overcome the balance demands of the task. This study evaluated sensory integration in the postural control of women with breast hypertrophy after breast reduction surgery. METHODS: In this study, 14 women with breast hypertrophy were evaluated before surgery and 6 months afterward. A force platform was used to assess how the somatosensory, visual, and vestibular systems contributed to postural control. Four conditions were used: eyes open/fixed platform (normal condition), eyes closed/fixed platform, eyes open/mobile platform, and eyes closed/mobile platform. For each condition, a nonparametric Friedman test was applied to compare the area and velocity of the center-of-pressure displacement between pre- and post-surgery tests. RESULTS: After surgery, the women demonstrated a smaller displacement area under normal conditions and in the eyes closed/fixed platform condition. The mean velocity in the forward-backward direction was significantly reduced after surgery when the women's eyes were closed on a mobile platform. CONCLUSIONS: After breast reduction surgery, women were found to control their posture with a smaller center-of-pressure displacement area when all sensory information was available and when their vision was suppressed with a fixed platform. Furthermore, the velocities were smaller when vision was suppressed with inaccurate somatosensory information. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Balance disturbances in asthmatic patients.

OBJECTIVE: The aim of this study was to investigate balance control in asthmatic patients. METHODS: Thirty subjects with controlled persistent asthma were compared with 30 non-asthmatic subjects who were matched by age and sex. Individuals who had received psychiatric treatment, demonstrated chronic musculoskeletal pain, had limited joint movements, or showed vestibular or other equilibrium disorders were excluded from both the groups to avoid biomechanical bias in the dynamic posturography. Balance control was evaluated with the subject standing still on a force platform under four different sensory test conditions. These conditions combined the subject's eyes being opened or closed with a fixed or mobile force platform. A mobile platform provides a somatosensory perturbation, and when associated with the eyes closed condition, only vestibular information is available to moderate balance control. Sensory manipulation provides a more sensitive condition to differentiate postural control between populations or pathologies. Data were sampled at 100 Hz in three 20-second trials and four postural conditions were assessed. The center of pressure (CoP) displacement values were used to calculate area and velocity in the medial-lateral and forward-backward directions. A two-factor analysis of variance with repeated measurements was applied to the data. RESULTS: In comparison to the control group, the asthma group demonstrated a greater area of CoP displacement in conditions using the mobile force platform (with eyes opened or closed) and a higher velocity in forward-backward direction on the mobile platform with the eyes closed. CONCLUSION: Asthmatic individuals presented a greater area for the CoP displacement under somatosensory perturbations and a higher velocity in the forward-backward direction when vestibular information only was made available. Our data suggest that balance needs to be evaluated in asthmatic patients.

Fear of heights: cognitive performance and postural control.

INTRODUCTION: Fear of heights, or acrophobia, is one of the most frequent subtypes of specific phobia frequently associated to depression and other anxiety disorders. Previous evidence suggests a correlation between acrophobia and abnormalities in balance control, particularly involving the use of visual information to keep postural stability. This study investigates the hypotheses that (1) abnormalities in balance control are more frequent in individuals with acrophobia even when not exposed to heights, that (2) acrophobic symptoms are associated to abnormalities in visual perception of movement; and that (3) individuals with acrophobia are more sensitive to balance-cognition interactions. METHOD: Thirty-one individuals with specific phobia of heights and thirty one non-phobic controls were compared using dynamic posturography and a manual tracking task. RESULTS: Acrophobics had poorer performance in both tasks, especially when carried out simultaneously. Previously described interference between posture control and cognitive activity seems to play a major role in these individuals. DISCUSSION: The presence of physiologic abnormalities is compatible with the hypothesis of a non-associative acquisition of fear of heights, i.e., not associated to previous traumatic events or other learning experiences. Clinically, this preliminary study corroborates the hypothesis that vestibular physical therapy can be particularly useful in treating individuals with fear of heights.