Definition of Essential tremor:

Essential tremor is a type of involuntary shaking movement in which no cause can be identified. Involuntary means you shake without trying to do so.

See also:

• Drug-induced tremor
• Tremor

Causes, incidence, and risk factors:

Essential tremor is the most common type of tremor. Everyone has some tremor present, but the movements are often so small that they can't be seen. Essential tremors are most common in people older than 65.

The exact cause for essential tremor is unknown. Tremors occur when there is a problem with the nerves that supply certain muscles. Some research suggests that the part of the brain that controls muscles movements does not work correctly in patients with essential tremor.

Essential tremor can also occur with other brain and nervous system problems, such as dystonia, parkinsonism, and certain nerve conditions passed down through families.

If an essential tremor occurs in more than one member of a family, it is called a familial tremor. This type of essential tremor is passed down through families (inherited), which suggests that genes play a role in its cause.

Familial tremor is usually a dominant trait, which means that you only need to get the gene from one parent to develop the tremor. It often starts in early middle age, but may be seen in people who are older or younger.