Inadequate interaction between open- and closed-loop postural control in phobic postural vertigo

Abstract

Phobic postural vertigo (PPV) is characterized by a subjective dizziness and postural imbalance. Changes in postural control strategy may cause the disturbed postural performance in PPV. A better understanding of the mechanisms behind this change in strategy is required to improve the diagnostic tools and therapeutic options for this prevalent disorder. Here we apply stabilogram diffusion analysis (SDA) to examine the characteristics and modes of interaction of open- and closed-loop processes that make up the postural control scheme in PPV. Twenty patients with PPV and 20 age-matched healthy controls were recorded on a stabilometer platform with eyes open and with eyes closed. Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed by means of SDA and complementary CoP amplitude measures. (1) Open-loop control mechanisms in PPV were disturbed because of a higher diffusion activity (p < 0.001). (2) The interaction of open- and closed-loop processes was altered in that the sensory feedback threshold of the system was lowered (p = 0.010). These two changes were comparable to those observed in healthy subjects during more demanding balance conditions such as standing with eyes closed. These data indicate that subjective imbalance in PPV is associated with characteristic changes in the coordination of open- and closed-loop mechanisms of postural control. Patients with PPV use sensory feedback inadequately during undisturbed stance, and this impairs postural performance. These changes are compatible with higher levels of anti-gravity muscle activity and co-contraction during the conscious concentration on control of postural stability.

Diagnostic criteria for persistent postural-perceptual dizziness (PPPD): Consensus document of the committee for the Classification of Vestibular Disorders of the Bárány Society

“…Several investigations showed that patients with PPV manifested an alteration in postural control characterized by high frequency, low amplitude postural sway related to co-contraction of lower leg muscles when standing at rest [46,98]. One study of patients with CSD demonstrated similar results [59].…”

“…In this connotation, functional is not a synonym for psychogenic or psychosomatic as it was throughout most of the 20th century and, therefore, does not reflect a presumption of psychopathological abnormalities. Studies of PPV, VV, SMD, and CSD identified a number of functional alterations in vestibular and balance mechanisms [33,37,46,59,67,68,71,88,98] associated with these clinical entities. Additional investigations separated them from primary psychiatric disorders [13,75] with which they may co-exist.…”

“…Investigations conducted in normal, healthy people found that they used this high demand postural control strategy only in challenging balance situations such as standing at heights [1,17,18]. Patients with PPV adopted this strategy during less demanding tasks than normal individuals [33,67,71], possibly related to a lower threshold for engaging closed loop feedback mechanisms to adjust posture [98]. Brandt et al [14] reported the case of a patient who was followed prospectively from a bout of acute vestibular neuritis to the development of PPV.…”

“…PPV = Phobic postural vertigo. 67,68,71,98]. Arguments against the idea included concerns that the mix of physical and psychological symptoms and personality traits that constitute PPV is difficult to operationalize in clinical practice [75] and may have to be updated based on newer research [76,85], and that including PPV as a subtype of PPPD without validating their relationship could perplex clinicians and investigators.…”

Tailored care for somatoform vertigo/dizziness: study protocol for a randomised controlled trial evaluating integrative group psychotherapy

“…Patients with panic or anxiety and patients with vestibular disorders frequently present with similar avoidance behaviours and complaints including dizziness, spatial disorientation, and anxiety in particular environments [14]. Additionally, both patients with primary vestibular disorders and patients with anxiety disorders have been observed to exhibit increased visual dependence (i.e., preferential use of vision for spatial orientation and postural control) and resulting body sway [15][16][17][18].…”