Characteristics of Parkinson\u27s disease and their influence on postural control

The motor deficiencies seen in Parkinson\u27s Disease (PD) are caused by changes occurring within the basal ganglia. However, the precise changes in the ganglia have not been completely correlated with clinical characteristics of the disease. The objective of this study was to characterize motor deficiencies in PD and to test hypotheses on basal ganglia function/organization. Four hypotheses were examined: 1. Akinesia and rigidity both associate with disability level. Disability assessed by clinical scales was quantified by various akinesia measures across laboratory tests. Measures of rigidity did not show any monotone relationship to disability. This indicated that akinesia associates with the level of disability but rigidity does not appear to associate with disability. 2. The basal ganglia is functionally arranged with multiple parallel pathways, not with a single pathway. Various parameters of movement were quantified. A high correlation was seen between a movement preparation measure and a movement execution measure. Greater variability in both measures was seen with progression. These results were consistent with the hypothesis of both movement measures progressing with the disease but, at independent rates. These results supported the theory that parameters of movement are separately controlled using parallel, segregated pathways. 3. Since the basal ganglia are organized somatotopically with respect to functional relationship to the body, focal pathology in the ganglia is expected to produce corresponding regional dysfunction in the body rather than all joints being affected equally. Parameters at various joints were quantified using a balance task. Hip excursion showed changes between PD and controls while the knee and ankle excursions did not show change. The relative work of the hip decreased with disease progression. This means that the PD patients could not or chose not to perform work about the hip. If PD patients could not perform work about the hip, this would support the hypothesis of differential effect of disease on different joints. 4. Akinesia and rigidity are independent PD characteristics. No monotone relationship was seen between rigidity and akinesia. This confirmed the current belief that akinesia and rigidity are independent and that akinesia is not influenced by rigidity or vice versa