Parkinsonian syndrome (also known as Parkinsonism, atypical Parkinson's or secondary Parkinson's) is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. There are many conditions that lead to Parkinsonism, and diagnosis can be difficult. While the neurodegenerative condition Parkinson's disease (PD) is the most common cause of parkinsonism, a wide range of other causes may lead to a similar set of symptoms, including some toxins, a few metabolic diseases, and a handful of neurological conditions unrelated to Parkinson's disease.