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. In general, tremors occur when there is a problem with the nerves supplying certain muscles. However, everyone has some essential tremor but the movements are usually so small that they can't be seen.

The specific cause for essential tremor is unknown. Some research suggests that the cerebellum, the part of the brain that controls muscles movements, does not work correctly in patients with essential tremor.

Noticeable essential tremors can be seen at any age but are most common in people older than 65.

Essential tremor can also occur with other neurological conditions, including dystonia, parkinsonism, and certain inherited nerve conditions such as Charcot-Marie-Tooth disease.

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 disorder. It usually starts in early middle age, but may be seen in people who are older or younger.