Quite often the patient does not notice significantly the slowness of movement or the stiffness until quite late in the course of the disease, and the relatives do not become aware of it.
Depression is a frequent concommon disease even though well before the diagnosis is apparent.
The response to levodopa therapy is also characteristic of Parkinson's disease and failure to respond to levodopa, while it does not exclude the diagnosis of idiopathic Parkinson's disease, does alert one to the possibility that the diagnosis is in fact one of the other causes of the Parkinsonian syndrome. Differential diagnosis from benign essential tremor and a mild depression may be relevant. A family history of tremor is more likely to indicate an essential tremor although there are some genetic causes of Parkinson's disease. A tremor occuring at rest is more likely to be Parkinsonian than an essential tremor. A number of clinical syndromes present with features of Parkinsonism and these can be difficult to differentiate from Parkinsons disease especially early in the course of the disease.