Objective: Previous studies in phobic postural vertigo patients showed characteristic frequency changes in body sway fluctuations, raising the question whether similar spectral changes can be also observed in the recently defined syndrome of persistent postural-perceptual dizziness (PPPD). Study design: Cross-sectional prospective study. Setting: Tertiary referral center. Subjects: Sixty-one PPPD patients and 41 healthy controls. Interventions: Static balance was assessed while standing on firm surface with eyes open or closed (conditions 1 and 2) and while standing on foam with eyes open or closed (conditions 3 and 4). Postural sway was analyzed by means of time (sway area and standard deviation) and frequency domain metrics. The latter was based on comparisons of the percentage of energy in each of three frequency bands: low (0-0.5 Hz), middle (0.05-2 Hz), and high frequency (2-20 Hz). Main outcome measure: Stabilometric time and frequency domain parameters. Results: Time domain metrics deteriorated significantly from conditions 1 through condition 4 in patients and controls.Spectral changes, however, were more abundant in PPPD subjects than in controls. Patients showed increased low frequency, but decreased high frequency spectral power in condition 3 as compared to condition 2. Dizziness Handicap Inventory score was positively correlated with middle frequency and negatively correlated with low frequency fluctuations. Conclusions: We conclude that PPPD patients exhibit a time domain sway pattern in different conditions which is grossly similar to that of controls. However, sensory feedback conditions with equal sway area show unique differences in their spectral content in PPPD patients. Moreover, perceived severity of dizziness is associated with greater body oscillations in the middle frequency band.

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Aims of the present article are: 1) assessing vestibular contribution to spatial navigation, 2) exploring how age, global positioning systems (GPS) use and vestibular navigation contribute to subjective sense of direction (SOD), 3) evaluating vestibular navigation in patients with lesions of the vestibular-cerebellum (downbeat nystagmus patients, DBN) which could inform on the signals carried by vestibulo-cerebellar-cortical pathways. We applied two navigation tasks on a rotating chair in the dark: return-to-start(RTS), where subjects drive the chair back to the origin after discrete angular displacement stimuli (path reversal), and complete-the-circle(CTC) where subjects drive the chair on, all the way round to origin (path completion). We examined 24 normal controls (20-83 year old), 5 DBN patients (62-77 year old) and, as proof of principle, 2 patients with early dementia (84 and 76 year old). We found a relationship between SOD, assessed by Santa-Barbara-Sense-Of-Direction-scale, and subject's age (positive), GPS use (negative) and CTC-vestibular-navigation-task (positive). Age-related decline in vestibular navigation was observed with the RTS-task but not with the complex CTC-task. Vestibular navigation was normal in vestibulo-cerebellar patients but abnormal, particularly CTC, in the demented patients. We conclude that vestibular navigation skills contribute to the build-up of our SOD. Unexpectedly, perceived SOD in the elderly is not inferior, possibly explained by increased GPS use by the young. Preserved vestibular navigation in cerebellar patients suggests that ascending vestibular-cerebellar projections carry velocity (not position) signals. The abnormalities in the cognitively impaired patients suggest that their vestibulo-spatial navigation is disrupted.