SURFACE DEPENDENCE - A BALANCE CONTROL STRATEGY IN PANIC DISORDER WITH AGORAPHOBIA

Previous studies have reported vestibular dysfunction and impaired bal ance in patients with agoraphobia. Vestibular dysfunction may lead to an information processing strategy focusing on spatial stimuli from tw o nonvestibular sensory channels, vision and proprioception. This nonv estibular balance control strategy may in turn lead to discomfort in s ituations involving inadequate visual or proprioceptive spatial cues ( space and motion discomfort). The objective of this study was to exami ne sensory integration of spatial information in agoraphobia. Because of previous findings that space and motion discomfort and vestibular d ysfunction are common in agoraphobia, we hypothesized that agoraphobic s would use a nonvestibular balance control strategy. Method: Using co mputerized dynamic posturography, we examined balance performance in p atients with panic disorder with agoraphobia, uncomplicated panic diso rder, nonpanic anxiety disorders, and depression without anxiety, as w ell as healthy subjects for comparison. The posturography procedure in cluded six sensory conditions in which visual and proprioceptive balan ce information was manipulated experimentally by permutations of sway- referencing the support surface or the visual surround or by having pa tients close their eyes. Results: The agoraphobics had impaired balanc e when proprioceptive balance information was minimized by sway-refere ncing the support surface (p < 0.02). This pattern, called surface dep endence, tended to be more pronounced in agoraphobics who reported spa ce and motion discomfort, including fear of heights or boats. Conclusi on: Agoraphobics rely on proprioceptive cues for maintenance of uprigh t balance. This strategy may lead to intolerance of situations charact erized by unstable support.