[Relationship between essential tremor, Parkinson's disease and dementia with Lewy bodies]

Although essential tremor (ET), Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are considered to be distinct illnesses, there is a certain overlap between some of their clinical, pathological and genetic features.

To conduct a critical examination of the evidence for and against the association between these three pathological conditions.

The body of evidence supporting the notion of a relation between ET and PD is growing all the time; the same can be said of the fact that a postural tremor may appear years before the onset of other extrapyramidal symptoms, the involvement of common genes in the development of both conditions or the presence of common pathological findings. In addition, it has also been suggested that there are several aspects linking PD and DLB, and it has even been claimed that that they might be part of the clinical spectrum of the same disease. The concept of ET as a benign single-symptom disease has changed in recent years and, since it has been related to cognitive disorders and Lewy bodies in the central nervous system, it is now considered to be a neurodegenerative pathology. CONCLUSIONS. ET, PD and DLB could represent different points on the same clinical spectrum.