Concerning overall motor deterioration in PD, global motor function was reported to show an annual decline of about 3% in one population-based study ; though, different courses of disease progression were found when related to the age of onset with a faster decline of mentation and gait in the older-onset group. On the other hand, positron emission tomographic imaging/ PET-based studies suggested a negative exponential course of progression at least when related to dopaminergic neurodegeneration. These ostensible discrepancies between the clinical course of disease progression and findings of functional imaging based investigations might be explained by the fact that PET studies are restricted to the monitoring of defined regions of interest and neurotransmitter systems which do not necessarily mirror the overall disease progression observed in clinical surveys. Besides these considerations about overall disease progression in PD, little is known about the development of different Ganciclovir speech modalities in the course of the disease in the individual patient with only single studies documenting a deterioration of distinct prosodic speech dimensions as pitch variability, speech rate and stability of syllable repetition which seem to rather arise after a longer disease duration without correlation to global motor function. To gain additional insight into the development of further aspects of speech in PD, the aim of the present study was the investigation of vowel articulation in the course of the disease in the individual patient and to test for correlations with global motor, gait and speech impairment. According to our hypothesis, a deterioration of global speech impairment in the course of the disease as assessed by perceptual rating should be mirrored by a decrease of tVSA and VAI as surrogate parameters for distinctiveness of vowel articulation. A second aim of the present investigation was to survey, if measurement of VAI turns out to be superior to tVSA in the detection of Tolclofos-methyl subtle changes of vowel articulation over time as it has to be supposed according to previous studies. This study analysed the development of vowel articulation as one distinctive parameter of speech in the clinical course of PD. While general motor performance according to UPDRS III remained relatively stable over time, vowel articulation in Parkinsonian speakers exhibited a significant deterioration which was not observed in the control group and therefore can be interpreted as a symptom of disease progression rather than as an effect of aging although �C admittedly �C the average follow-up interval was shorter in the control than in the PD group. Notwithstanding the widely stable overall motor performance, the majority of patients featured a decline of gait function and an increase of H&Y staging between first and second examination which showed a correlation to the deterioration of vowel articulation.