[Essential tremor and Parkinson's disease: are they associated?].
BACKGROUND
There is now growing evidence that essential tremor and Parkinson's disease are related.


OBJECTIVE
To present the main findings from epidemiologic, genetic, clinical, imaging and pathologic studies, contrasting evidences for and against an association between essential tremor and Parkinson's disease.


METHODS
We include a complete update of the latest findings regarding the overlap between these two disorders. There is current evidence that a history of essential tremor may herald the onset of Parkinson's disease in a subset of patients. Furthermore, the fact that the risk of essential tremor is significantly increased in relatives of patients with Parkinson's disease suggests the possibility that both conditions are genetically related, probably sharing common hereditary predisposition. Dopaminergic deficit among essential tremor patients in functional imaging studies and recent pathological studies describing Lewy bodies in some essential tremor patients, support further evidence for an overlap between both conditions, at least in a subset of patients.


CONCLUSIONS
The convergence of all the reviewed data suggests the possible existence of a mixed essential tremor-Parkinson's disease phenotype in some patients. However, further studies are needed to better understand this phenotype.
Servicio de Neurología, Hospital Universitario 12 de Octubre, Madrid, España.
Andrés
A
Labiano-Fontcuberta
Julián
J
Benito-León
D000367:Age Factors; D000368:Aged; D003863:Depression / Q000453:epidemiology / Q000209:etiology; D018450:Disease Progression; D020329:Essential Tremor / Q000150:complications* / Q000453:epidemiology / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D016631:Lewy Bodies / Q000648:ultrastructure; D008125:Locus Coeruleus / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics; D059906:Neuroimaging; D010300:Parkinson Disease / Q000150:complications* / Q000453:epidemiology / Q000235:genetics / Q000473:pathology / Q000503:physiopathology / Q000523:psychology; D020734:Parkinsonian Disorders / Q000453:epidemiology; D015995:Prevalence; D012306:Risk; D014202:Tremor / Q000145:classification / Q000453:epidemiology
C482293:LINGO1 protein, human; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins