The Function of the Proprioceptive, Vestibular and Visual Systems Following Fatigue in Individuals With and Without Chronic Ankle Instability

Bilateral alterations in sensorimotor function and altered sensory strategy in individuals with unilateral chronic ankle instability

Objective

This study aimed to evaluate bilateral sensorimotor function in patients with unilateral CAI. Furthermore, sensory reweighting ability and vestibular modulation were assessed.

Methods

Twenty individuals with unilateral CAI and twenty healthy controls participated in this study. All participants executed ankle proprioception, plantar sensation, unilateral stance, Y balance, motor control test (MCT) and sensory organisation test (SOT) assessments. Proprioception assessment included joint position sense and force sense (FS), and plantar sensation evaluation consisted of light-touch, vibration and two-point discrimination (TPD) thresholds at the heel, head of the first metatarsal (1 MF), base of the fifth metatarsal (5 MF), centre of foot and forefoot. MCT and SOT tests were conducted using NeuroCom Balance Manager System. Except for SOT, all tests evaluated bilateral limbs, and the order of limbs was randomly selected. 2 (group) × 2 (limb) mixed model analyses of variance were performed for outcome measures of unilateral stance, Y balance and MCT, and independent t-test was used to analyse the outcomes of SOT between two groups. Mann-Whitney U and Wilcoxon test were applied to examine the differences in plantar sensation between groups and limbs.

Results

For plantar sensation, increased light-touch threshold at heel and 1 MF and the TPD threshold at 1 MF were observed bilaterally in CAI group (p < 0.05). No differences were observed in joint position sense (JPS), but bilateral deficit was found in plantarflexor FS with moderate effect size (uninjured side: ES = 0.67; injured side: ES = 0.61) in CAI group. For unilateral stance with eyes closed, moderate postural instability was displayed bilaterally in the anteroposterior direction (uninjured side: ES = 0.71; injured side: ES = 0.86). The delayed latency of MCT with medium-backward translation was also observed in both sides of unilateral CAI (uninjured: ES = 0.74; injured: ES = 0.92). Compared with healthy controls, higher visual reliance was shown moderately in the injured and uninjured sides of unilateral CAI (uninjured: ES = 0.78; injured: ES = 0.91). Sensory analysis of SOT displayed decreased use of visual (p = 0.001) and vestibular information (p < 0.000) in CAI group.

Conclusion

Unilateral CAI presented impaired plantar sensation and ankle proprioception on both sides. Higher visual reliance, delayed motor response and postural instability under unreliable visual clues were also displayed bilaterally. Except for bilateral sensorimotor alterations, reduced ability of sensory reweighting and fixed sensory strategy also presented in CAI group, but the somatosensory clue still served as the main sensory source in CAI.

The Protocol for Active Movement Extent Discrimination Assessment (AMEDA) is Reliable When Shortened From 50 to 25 Stimuli to Reduce Testing Fatigue

Active movement extent discrimination assessment (AMEDA) is a psychophysical task that evaluates proprioception and tactile acuity of the lower limbs, and it is a method of determining sensorimotor ability. Sensorimotor ability is the ability to judge small differences in movement tasks through the process of receiving sensory messages (sensory input) and producing a response (motor output). Participant attention lapses in prior psychophysical studies have been implicated as a cause for increased measurement variance thresholds in these types of assessments. Since minimizing the time needed for the AMEDA may help to reduce attention lapses, we compared the reliability of the 50-repetition AMEDA protocol (Group 1) with that of a 25-repetition protocol (Group 2). We assessed the split half reliability of these two approaches, using the Spearman-Brown Adjusted Pearson correlation (r). For each method, we calculated Bland-Altman Plots and Intra Class Correlation Coefficients to compare the reliability of the two data sets and determine the 95% confidence intervals. Split-half test re-test Spearman-Brown Adjusted Pearson r (rfull) was Group 1 rfull = 0.83 and Group 2 rfull = 0.85. The Bland-Altman Plots indicated only a small degree of bias from the zero-difference line, with 95% of the difference points lying within the limits of agreement. For Group 1, the intraclass correlation coefficient (ICC) two-way, agreement was 0.83 (95% CI 0.54-0.93) and for Group 2, the ICC, two-way, agreement, was 0.85 (95% CI 0.66-0.93). The MDC90 for Group 1 was 0.082 AUC units and for Group 2, it was 0.086 AUC units. The combined data for Group 1 plus Group 2 Bland-Altman Plot indicated only a small degree of bias from the zero-difference line, with 95% of the difference points lying within the limits of agreement. The MDC90 for the combined groups was 0.08 AUC units. The multiple methods from previous research assessing test re-test reliability that we applied to our two data sets indicate that the 25-response AMEDA was a reliable system for evaluating sensorimotor function in the lower limbs and may be an alternative for the more traditional 50-response protocol in which lapses in participant attention from fatigue or other biases may be a concern. There are also practical advantages in time restricted athletic screenings to a shorter administration of this assessment.

Smartphone Usage and Postural Stability in Individuals With Forward Head Posture: A Nintendo Wii Balance Board Analysis

OBJECTIVE

To assess postural stability, specifically center of body sway during single-leg standing balance, among individuals with and without forward head posture (FHP) during smartphone use.

METHODS

The research recruited 53 healthy smartphone users, aged 18-25, and categorized them into FHP group comprising 26 subjects and the normal (control) group with 27 subjects. Participants were assigned the task of maintaining balance while engaged in smartphone typing during single-leg standing. The experiment involved four specific conditions according to neck posture and stable of surface. The study meticulously quantified body center of pressure (COP) sway amplitudes using the Nintendo Wii Balance Board.

RESULTS

The research revealed that individuals with FHP exhibited significantly greater body sway compared to the control group when using smartphones. Notably, distinct variations were observed in path length sway, anteroposterior (AP), and mediolateral (ML) sway amplitude, particularly evident when maintaining flexed neck positions on a soft surface while engaged with smartphones.

CONCLUSION

These findings strongly suggest that individuals with FHP encounter deteriorated postural stability during smartphone use, particularly in challenging head positions.

Increased functional connectivity between default mode network and visual network potentially correlates with duration of residual dizziness in patients with benign paroxysmal positional vertigo

Objective

To assess changes in static and dynamic functional network connectivity (sFNC and dFNC) and explore their correlations with clinical features in benign paroxysmal positional vertigo (BPPV) patients with residual dizziness (RD) after successful canalith repositioning maneuvers (CRM) using resting-state fMRI.

Methods

We studied resting-state fMRI data from 39 BPPV patients with RD compared to 38 BPPV patients without RD after successful CRM. Independent component analysis and methods of sliding window and k-means clustering were adopted to investigate the changes in dFNC and sFNC between the two groups. Additionally, temporal features and meta-states were compared between the two groups. Furthermore, the associations between fMRI results and clinical characteristics were analyzed using Pearson's partial correlation analysis.

Results

Compared with BPPV patients without RD, patients with RD had longer duration of BPPV and higher scores of dizziness handicap inventory (DHI) before successful CRM. BPPV patients with RD displayed no obvious abnormal sFNC compared to patients without RD. In the dFNC analysis, patients with RD showed increased FNC between default mode network (DMN) and visual network (VN) in state 4, the FNC between DMN and VN was positively correlated with the duration of RD. Furthermore, we found increased mean dwell time (MDT) and fractional windows (FW) in state 1 but decreased MDT and FW in state 3 in BPPV patients with RD. The FW of state 1 was positively correlated with DHI score before CRM, the MDT and FW of state 3 were negatively correlated with the duration of BPPV before CRM in patients with RD. Additionally, compared with patients without RD, patients with RD showed decreased number of states and state span.

Conclusion

The occurrence of RD might be associated with increased FNC between DMN and VN, and the increased FNC between DMN and VN might potentially correlate with the duration of RD symptoms. In addition, we found BPPV patients with RD showed altered global meta-states and temporal features. These findings are helpful for us to better understand the underlying neural mechanisms of RD and potentially contribute to intervention development for BPPV patients with RD.