Postural stability maintenance was investigated in patients with "idiopathic" benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and compared to healthy subjects. To measure the postural stability during a quiet upright stance, we used static posturography in two conditions: with open and with closed eyes. The effect of the repositioning Epley's maneuver on the recovery of postural stability in patients with different durations of BPPV-PSC less than 60 days after the first attack of positioning vertigo (group I) and more than 60 days (group II) was examined. The investigation was made 1 h after the positive Dix-Hallpike test and 7 days after treatment with the Epley maneuver. "Sway velocity" (SV) and "relative power spectrum" (RPS) of the stabilograms were calculated to evaluate the postural stability for each subject and each experimental condition. We found a pronounced spectral density peak in the frequency range of 1.0-2.0 Hz and smaller spectral density in the range of 0.15-0.5 Hz compared to that in healthy subjects. Our results showed that the postural maintenance in BPPV-PSC patients depended on the disease duration. Patients with a duration of BPPV symptoms less than 60 days after the first attack demonstrated a high dependence on the visual input for postural stability. One week after the Epley maneuver, differences in the recovery of postural control in both groups of patients were also found. We assume that the disturbed otolith function together with the impaired dynamics of the semicircular canal generate a particular pattern of postural maintenance. The different degree of restoration of postural stability 1 week after the EM treatment in BPPV-PSC patients with different durations of the disease gives us reason to believe that after removing the otoconia from the semicircular canal, some stimulation of other sensory subsystems and adaptation mechanisms occur that lead to a new pattern of postural maintenance.

We studied the postural stability of 23 canoeing and kayaking young athletes and 15 healthy untrained age matched subjects during quiet and sensory conflicted stance (standing on stable and foam support with open and closed eyes). We measured with a force platform the center of pressure excursions and applied mean sway amplitude (MA), mean sway velocity (SV) and their Romberg ratios, and sway dispersion index to evaluate standing balance. During standing with eyes open, the athletes in comparison to non-athletes showed in sagittal and frontal plane greater MA and SV when the support was stable and smaller MA and SV when it was unstable. During standing with eyes closed, there were no differences between groups when the support was stable, however, the athletes sway faster and have smaller MA than controls while standing on the foam support. During standing on stable support, Romberg ratios for MA and SV revealed that unlike non-athletes the athletes' MA and SV were vision independent. However, while standing on unstable support the athletes' MA and SV became vision dependent and even greater for the medio-lateral sway. Canoeists' SV vision dependency in both planes was greater than for other groups. These results are in line with our hypothesis that young kayaking and canoeing athletes have a different from non-athletes model of sensory integration due to their specific sporting activity. One possible mechanism of this model may be a subtle re-adaptation deficit after disembarking to stable ground with diminished sensitivity of vision and vestibular apparatus.

The Bulgarian version of the DHI is a reliable and valid tool in assessing the impact of dizziness on the quality of life in Bulgarian vestibular patients.

The postural stability of 30 panic disorder (PD) patients and 30 sex- and age-matched healthy control subjects (age range 27-40 years) was investigated by static posturographic tests of quiet standing on stable and foam surfaces with open and closed eyes. Postural stability was evaluated by sway velocity (SV) and power density of relative power spectrum (RPS) in five frequency ranges. There were no differences of SV between two groups during stance with open eyes on both surfaces. The SV of the PD patients standing with closed eyes was significantly higher compared to controls for the stance on the stable surface (anterior-posterior plane) and on the foam surface (both anterior-posterior and medial-lateral planes). The stance on foam surface did not cause any significant changes in power density of postural sways of healthy subjects, while this parameter was significantly higher for PD patients, especially in closed eyes condition when a sensory conflict may exist. The higher value of SV and RPS (0.5-1.0 Hz) in patients compared to controls suggests that the visual information has more important role in the postural balance when sensory conflict exists during stance on foam surface. We proposed that the altered information from the visual and proprioceptive inputs may induce anxiety and panic symptoms in PD patients, which enhances the sensory conflict, leads to abnormal work of the vestibular system and disturbs the standing balance.