Review of tremor in Parkinson's disease and atypical parkinsonian disorders.

Rest tremor (RT), a cardinal feature of Parkinson's disease (PD) is often accompanied by other types of tremor such as action tremor, which includes postural tremor, kinetic tremor, re-emergent tremor (ReT), and orthostatic tremor (OT). Literature on other tremors of PD, especially ReT and OT, is scarce. Tremor can be present in any of the atypical parkinsonian disorders such as progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration, and dementia with Lewy bodies. RT can even be the presenting symptom of these disorders. The objective of this review is to provide a comprehensive review of lesser known tremors in PD and to critically look at the prevalence of tremor in atypical Parkinsonian disorders.