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Parkinson’s disease is a slowly progressive, degenerative disorder of the substantia nigra of unknown etiology. The main pathomorphological finding in Parkinson’s disease is the loss of dopaminergic neurons in the substantia nigra pars compacta, which results in deficiency of the neurotransmitter dopamine in the striatum. Parkinson’s disease is an akinetic-rigid syn­drome with the main clinical features of tremor, rigidity, bradykinesia and postural instability. Although postural instability has a large impact on the quality of life of Parkinsonian patients, it can be only poorly controlled by antiparkinsonian treatment.

Besides Parkinson’s disease, postural instability can also result from diseases of the vestibu­lar system, cerebellum, diabetes mellitus, effects of various drugs or aging. The aim of the first part of this study was to measure the maintenance of equilibrium during free stance in a group of young subjects and a group of healthy seniors in order to assess the influence of age on postural stability. The objective of the second part of the study was to measure the mainte­nance of equilibrium during free stance in a group of patients with Parkinson’s disease, before and after administration of the dopaminergic agonist apomorphine. The intention was to estab­lish the influence of apomorphine on postural instability.

The maintenance of equilibrium was measured during free stance and the overall motor status was evaluated in healthy subjects and in patients with Parkinson’s disease, before and after administration of apomorphine, in order to test the following two hypotheses: 1. The maintenance of equilibrium during free stance in healthy subjects (aged 23 to 61) is not affect­ed by age. 2. The dopaminergic agonist apomorphine can significantly change the power spectrum of body oscillations during free stance in patients with Parkinson’s disease.

The research was designed as a prospective study in humans. According to their age and the presence or absence of Parkinson’s disease, the subjects were divided into three groups: A) a group of young healthy subjects with the mean age of 23.2 years; B) a group of older healthy subjects with the mean age of 61.5 years; and C) a group of Parkinsonian patients with the mean age of 62 years. Stabilometry was used to measure the maintenance of equi­librium during free stance and the motor part of the unified Parkinson’s disease rating scale (mUPDRS) for evaluating the subject’s overall motor status. Healthy subjects were evaluat­ed with one mUPDRS and three consecutive stabilometric measurements. Parkinsonian patients were evaluated with mUPDRS and three stabilometric measurements, before and after the application of a dose of apomorphine. The results of mUPDRS evaluations in healthy sub­jects were compared statistically using the unpaired Wilcoxon’s test and, in patients with Parkinson’s disease, with the paired Wilcoxon’s test. From each of the three consecutive sta- bilometric measurements, the average power spectrum was calculated for saggittal and lateral body oscillations during free stance. The power spectrums were then compared statistical­ly using the unpaired Wilcoxon’s test for healthy subjects and the paired Wilcoxon’s test for patients with Parkinson’s disease.

There were no statistically significant differences in the results of mUPDRS between the two groups of healthy subjects (aged 23 to 61), but both groups had significantly lower mUPDRS results compared to the group of Parkinsonian patients, before and after the application of apomorphine (p < 0.01; unpaired Wilcoxon’s test). No significant differences in the power spec- trums of saggittal and lateral oscillations during free stance were found between the two groups of healthy subjects. Apomorphine significantly reduced the mUPDRS score in Parkinsonian patients (p < 0.01; paired Wilcoxon’s test). In addition, apomorphine significantly increased the average amplitude of frequencies 0.6-1 Hz (p < 0.01; paired Wilcoxon’s test) and reduced the average amplitude of frequencies 0.2-0.6 Hz (p < 0.05) of saggittal oscillations during free stance. A similar trend was observed for lateral oscillations, although the differences were not statistically significant.

Our first hypothesis was confirmed, as we proved that aging (from 23 to 61 years) does not affect the maintenance of equilibrium during free stance in healthy subjects. Our sec­ond hypothesis was also partially confirmed by proving that application of the dopaminergic agonist apomorphine results in statistically significant changes in the power spectrum of sag- gittal body oscillations during free stance. However, it does not have a significant influence on the power spectrum of lateral body oscillations during free stance. Apomorphine was par­tially successful in attenuating the symptoms of Parkinson’s disease, including postural instability. Postural instability in patients with Parkinson’s disease is therefore treatable.