premise: Parkinson's disease causes bradykinesia.
hypothesis: Parkinson-plus syndromes , also known as disorders of multiple system degeneration , is a group of neurodegenerative diseases featuring the classical features of Parkinson 's disease ( tremor , rigidity , akinesia/bradykinesia , and postural instability ) with additional features that distinguish them from simple idiopathic Parkinson 's disease ( PD ) . Additional features include bradykinesia , early-onset postural instability , increased rigidity in axial muscles , dysautonomia , alien limb syndrome , supranuclear gaze palsy , apraxia , involvement of the cerebellum including the pyramidal cells , and in some instances significant cognitive impairment . Parkinsonism is a clinical syndrome characterized by tremor , bradykinesia , rigidity , and postural instability .