Factor analysis of Parkinson's impairment. An evaluation of the final common pathway.

The question of how pathophysiologic mechanisms may combine to yield significant performance impairment in Parkinson's disease was studied by factor analysis of the covariation among behavioral deficits observed during simulated daily living activities. Eighty-four patients with idiopathic Parkinson's disease were videotape-recorded while performing a sequence of nine common tasks of daily living in a standardized format. Acceptable observer reliability was achieved for ten clinical signs that were factor-analyzed to suggest three dimensions of motor performance: ambulation, tremor, and animation. The findings are discussed with respect to traditional concepts of Parkinson's disease and the possible interplay between primary disease mechanisms.