Types of Tremor

Rest Tremor:

This is defined as a tremor which occurs in a body part in which the muscles are not being voluntarily contracted and which is completely supported against gravity e.g. the whole limb resting on a couch. Normally when the limb is moved, the rest tremor will attenuate or disappear. Like all tremors, it will be aggravated by stress or anxiety. Rest tremor is quite separate from other tremors. It is most commonly found in Parkinson's disease.

Action Tremor:

This is any tremor occurring when there is voluntary activation or contraction of muscles. For instance, holding an arm outstretched requires muscle activity to hold the limb against gravity. Action tremors include postural tremors, kinetic tremors (i.e. tremors during movement) and intention tremors.

Postural Tremor:

This is the tremor which is present while voluntarily maintaining a position against gravity, i.e. arm outstretched. Postural tremors require voluntary or purposive contraction of muscles. The commonest examples would be exaggerated physiological tremor and essential tremors. Sometimes postural tremors become exaggerated in specific postures. This has been given the name "position specific or position sensitive postural tremor".

Kinetic Tremor:

This is the tremor which occurs during movement of a body part (it could equally be called a movement tremor). Simple kinetic tremor can be brought out by the clinician by asking the subject to carry out simple rotary movements of the forearm or flexion and extension movements of the wrist. Those with postural tremors will often be shown to have tremor during movement.

Intention Tremor:

Complex kinetic tremor is normally referred to as "intention tremor" and is seen when tremor becomes exaggerated when the limb is directed towards a particular target. The subject will see this when they are asked by the examiner to reach out and touch the examiner's finger and then touch their own nose, so called "finger to nose testing". When tremors become exaggerated in this situation, they are called "intention tremors". This is important to the clinician as it may imply disturbance in a particular part of the brain known as the cerebellum and the cerebellum's connections to other parts of the nervous system.

Task Specific Kinetic Tremor:

These are tremors which appear only, or become very exacerbated with specific tasks or activities the individual is asked to carry out. They are sometimes called occupational tremors and the best example of this is "primary writing tremor". This is a condition in which tremor is largely or only seen during the act of writing or acts which mimic writing.