Epidemiology and Genetics of Essential Tremor

Abstract

Summary: Essential tremor (ET) is one of the most common movenient disorders. Howevcr. the etiology and pathogenesis are as yet unknown. Continued research will give us clues to understanding the impact o n society. identifying genetic and environmental contributors t o the disease, understanding the significance of a sporadic case. the phenotypic spectrum and timing of presentation. and the relationship with other neurologic disorders. Because the condition is both clinically and genetically heterogeneous and there is overlap with these other disorders, such as dystonia, parkinsonism. peripheral neuropathy. and migraine, the definition of phenotype plagues research in this area. Advances in understanding the genetic and molecular underpinnings of tremor should provide additional tools to unravel the clinical phenotype (including physiology). genotype-phenotype relationships, and the epidemiology of tremor.

Does Age of Onset in Essential Tremor Have a Bimodal Distribution? Data from a Tertiary Referral Setting and a Population-Based Study

“…Similar to what was observed in the current study, previous clinic-based samples of ET cases have noted the presence of large young-onset peaks [3][4][5] . By contrast, in epidemiological studies, a young-onset peak has been more difficult to appreciate.…”

“…For neurological disorders, however, such bimodality is relatively uncommon; furthermore, this bimodal distribution of age of onset seems at odds with limited data from epidemiological studies [6,8] . Summary statistics (e.g., mean, range) on age of onset are sometimes reported in ET case series, although the distributions themselves are rarely presented [3][4][5] . Indeed, until now, there has not been a study whose analyses were primarily focused on the age of onset of ET, nor has there been a study that assessed age of onset in different settings using the same evaluation and diagnostic tools.…”

“…In review articles [2,5] , the age of onset of ET is often said to be bimodally distributed. For neurological disorders, however, such bimodality is relatively uncommon; furthermore, this bimodal distribution of age of onset seems at odds with limited data from epidemiological studies [6,8] .…”

“…The age of onset of essential tremor (ET) is often said to have a bimodal distribution, with peaks occurring during the second or third decades and seventh or eighth decades of life [2][3][4][5] . For neurological disorders, such bimodality is relatively uncommon.…”

Dopamine receptor D3 gene and essential tremor in large series of German, Danish and French patients

“…1 Segregation analysis reveals that ET transmission might be compatible with an autosomal-dominant mode of inheritance. 2 However, a large proportion of ET patients present as isolated cases, and in that case, ET is considered not to be a single gene disorder but a complex disease requiring interactions of environmental and genetics factors with low penetrance. 3 -5 At least three chromosomal loci (ETM) have been identified by linkage analysis so far.…”