Table 4.

Design recommendations for studies focused on genetic research of essential tremor (adapted from text of Reference [23]).

Selection of Index Patients and Controls
Index patients should have a positive family history of ET and be diagnosed with definite and ‘‘pure’’ or “monosymptomatic” ET according to standardized criteria.
Index patients could participate both in family studies and in case-control association studies or family studies.
Inclusion of controls in case-control association studies as “healthy” should imply the absence of a family history of tremor and other movement disorders and the neurological interview and examination to exclude the presence of tremor or other movement disorders.
Selection of Relatives
All available first-degree relatives of the index patient should undergo a clinical examination, including rating scales for tremor.
ET families should be divided into several subtypes, that should be sub-analyzed separately, according to the coexistence or not of other neurological diseases such as dystonia and PD (“pure ET”, “ET-dystonia”, “ET-PD”, “ET-dystonia”).
Study Design
Multicenter, multiethnic, and prospective design.
Long-term follow-up to assess further development of PD or other associated disorders in the index patients, in their relatives, or both, and development of ET during the follow-up period by relatives of ET patients who had no tremor in the initial assessment
Blood Collection
Obtention of blood for DNA extraction both from patients, their relatives, and healthy controls. The samples obtained will be used for future genetic studies attempting to establish the role of genetic factors in the different clinical subtypes of ET.