The Phenotypic Spectrum of Parkinson Disease

For most patients, the diagnosis of Parkinson disease (PD) depends on recognition of the clinical features of the disorder since no definitive neuroimaging or laboratory diagnostic test is available. The four cardinal motor features of PD-tremor, rigidity, bradykinesia, and postural instability-are well known. It has only been in recent years, however, that a wide variety of abnormalities that have little or nothing to do with motor function also have been recognized as integral features of PD, sometimes even preceding the development of the motor features. Animal models of PD primarily have been aimed at reproducing the motor features of the disorder, but the need exists for the development of models that also incorporate the nonmotor aspects of PD. This chapter describes both the motor and nonmotor features of PD to provide a more complete picture of the disorder.