Responses to balance challenges in persons with panic disorder: A pilot study of computerized static and dynamic balance measurements

Abstract

Introduction: Several studies have shown an association between panic disorder (PD) and reduced balance abilities, mainly based on functional balance scales. This pilot study aims to demonstrate the feasibility of studying balance abilities of persons with PD (PwPD) using computerized static and, for the first time, dynamic balance measurements in order to characterize balance control strategies employed by PwPD.

Methods: Twelve PwPD and 11 healthy controls were recruited. PD diagnosis was confirmed using the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), and the severity of symptoms was evaluated using the Hamilton Anxiety Scale (HAM-A), PD Severity Scales (PDSS), and Panic and Agoraphobia Scale (PAS). Balance was clinically assessed using the Activities-Specific Balance Confidence (ABC) scale and physically by the Mini-Balance Evaluation Systems Test (Mini-BESTest). Dizziness was evaluated using the Dizziness Handicap Inventory (DHI) scale. Postural control was evaluated statically by measuring body sway and dynamically by measuring body responses to rapid unexpected physical perturbations.

Results: PwPD had higher scores on the HAM-A (17.6 ± 10.3 vs. 3.0 ± 2.9; p < .001), PDSS (11.3 ± 5.1 vs. 0; p < .001), and PAS (20.3 ± 8.7 vs. 0; p < .001) questionnaires and lower scores on the balance scales compared to the controls (ABC scale: 156.2 ± 5.9 vs. 160 ± 0.0, p = .016; Mini-BESTest: 29.4 ± 2.1 vs. 31.4 ± 0.9, p = .014; DHI: 5.3 ± 4.4 vs. 0.09 ± 0.3, p < .001). In the static balance tests, PwPD showed a not-significantly smaller ellipse area of center of pressure trajectory (p = .36) and higher body sway velocity (p = .46), whereas in the dynamic balance tests, PwPD had shorter recovery time from physical perturbations in comparison to controls (2.1 ± 1.2s vs. 1.6 ± 0.9 s, p = .018).

Conclusion: The computerized balance tests results point to an adoption of a ''postural rigidity'' strategy by the PwPD, that is, reduced dynamic adaptations in the face of postural challenges. This may reflect a nonsecure compensatory behavior. Further research is needed to delineate this strategy.

Keywords: dynamic balance; panic disorder; perturbations; static balance; sway.

FIGURE 1

(a) Participant sway on a platform with two embedded force plates tracking her center of pressure displacement (Dc_op); (b) Dc_op area in the medial‐lateral (ML) and anterior‐posterior (AP); (c) A moveable platform with six degrees of freedom illustration (x, y, and z axes). The platform is synchronized with a motion capture system (Vicon, Oxford, UK), which collects kinematic positional data from 41 passive reflective markers attached to the participant's body (120 Hz; 1 mm resolution). Electrocardiography (ECG) was recorded as well. Kinematic and ECG results are not presented here. The weighted Dc_op was calculated by using the distance equation $D_{\mathrm{CoP}}=\sqrt{{D_{\mathrm{CoP}}}_{\mathrm{AP}}^2+{D_{\mathrm{CoP}}}_{\mathrm{ML}}^2}$

FIGURE 2

Center of pressure displacement (Dc_op; blue) and absolute velocity ($\overline{V_{\mathrm{CoP}}}$; green) during a left rotation perturbation with dual task (DT) time segment, from a single session of a single participant. An “envelope” over the velocity signal is shown in red. A red star marks onset of the perturbation (Pert), and a black star marks the participant's recovery

FIGURE 3

Box plots of Dc_op ellipse area (left) and of velocity (right) in four sway conditions depicted for both groups (see color key). Within each box, horizontal lines denote median values and “X” markers denote mean values; boxes extend from the 25th to the 75th percentile of each group's distribution of values; vertical extending lines denote adjacent values (i.e., the most extreme values within 1.5 interquartile range of the 25th and 75th percentile of each group). *p < .05; **p < .01