Epidemiology, diagnosis and differential diagnosis in Parkinson's disease tremor.

The epidemiology of tremor in Parkinson's disease is not well examined. The prevalence of Parkinson's disease is about 100-300 per 100,000, and the majority (70-100%) of these patients may develop tremor during the course of the disorder. The expression of tremor is also influenced by the genetic background of selected patients. On the other hand, Parkinson patients with a predominant tremor phenotype may have a more favourable prognosis in terms of mortality and the development of motor and non-motor complications. The diagnosis of Parkinson tremor is based on a clinical diagnosis of both underlying Parkinson's disease and on the tremor itself. Tremor is a rhythmical, involuntary oscillatory movement of a body part, and includes resting tremor, action tremor including postural and kinetic tremor. The classical type is resting tremor, but other phenotypes may also occur. Misdiagnoses between Parkinson tremor and essential tremor are relatively common. Electrophysiological and functional imaging examinations can be useful in the distinction of the two, but both approaches suffer from some limitations. In general, essential tremor and other tremor forms can be distinguished from Parkinson tremor by their frequency and their expression with different activation.