Essential tremor
This ailment affects men and women, being more frequent in people over 65 years of age. Although the exact cause of essential tremor is unknown, some work indicates that the part of the brain that controls muscle movements does not work correctly in patients with essential tremor. Half of the cases of essential tremor are the consequence of a genetic mutation, although the specific gene has not been identified.  This type is called familial tremor. It is unknown what causes essential tremor in people who do not have a genetic mutation.