Abstract
Objective: To determine whether performance in a virtual spatial navigational task is poorer in persistent postural perceptual dizziness (PPPD) patients than in healthy volunteers and patients suffering other vestibular disorders.Methods: Subjects were asked to perform three virtual Morris water maze spatial navigational tasks: (i) with a visible target, (ii) then with an invisible target and a fixed starting position, and finally (iii) with an invisible target and random initial position. Data were analyzed using the cumulative search error (CSE) index.Results: While all subjects performed equally well with a visible target, the patients with PPPD (n = 19) performed poorer (p < 0.004) in the invisible target/navigationally demanding tasks (CSE median of 8) than did the healthy controls (n = 18; CSE: 3) and vestibular controls (n = 19; CSE: 4). Navigational performance in the most challenging setting allowed us to discriminate PPPD patients from controls with an area under the receiver operating characteristic curve of 0.83 (sensitivity 78.1%; specificity 83.3%). PPPD patients manifested more chaotic and disorganized search strategies, with more dispersion in the navigational pool than those of the non-PPPD groups (standard distance deviation of 0.97 vs. 0.46 in vestibular controls and 0.20 in healthy controls; p < 0.001).Conclusions: While all patients suffering a vestibular disorder had poorer navigational abilities than healthy controls did, patients with PPPD showed the worst performance, to the point that this variable allowed the discrimination of PPPD from non-PPPD patients. This distinct impairment in spatial navigation abilities offers new insights into PPPD pathophysiology and may also represent a new biomarker for diagnosing this entity.
Highlights
Persistent postural perceptual dizziness (PPPD) is a clinical entity that comprises different types of non-vertiginous dizziness and represents the most common cause of chronic vestibular syndromes [1, 2]
This framework is interesting, as it offers a better understanding of visual induced dizziness and symptoms reported in PPPD, in regard to the response of complex visual stimuli or the difficulty these patient refer when being in crowed spaces, such as a mall or in a subway station, with multiple objects moving rapidly in different directions
We found worse performance in the virtual Morris water maze (MWM) spatial navigation test [12, 15,16,17] in patients presenting with PPPD than in both healthy subjects and patients suffering from other vestibular disorders but not presenting with PPPD
Summary
Persistent postural perceptual dizziness (PPPD) is a clinical entity that comprises different types of non-vertiginous dizziness and represents the most common cause of chronic vestibular syndromes [1, 2]. One theoretical approach focuses on errors in visual, proprioceptive, and vestibular integration [6,7,8] and the reduced cortical integration of spatial orientation cues as a pathological response to a triggering event [9, 10]. These disturbed computations of multimodal inputs can generate an inappropriate inner spatial model of the environment and of the patient’s position in it. This framework is interesting, as it offers a better understanding of visual induced dizziness and symptoms reported in PPPD, in regard to the response of complex visual stimuli or the difficulty these patient refer when being in crowed spaces, such as a mall or in a subway station, with multiple objects moving rapidly in different directions (which could be understood as an overload of multimodal information to be processed, and a subsequent difficulty on constructing an accurate and properly timed inner model)
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