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.
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.
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".
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.
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.
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.
Although essential tremor is becoming increasingly acknowledged and diagnosed, awareness and understanding of dystonic tremor, although increasing, is considerably less. The term idiopathic dystonic tremor is used to describe a tremor that has developed spontaneously or due to an unknown cause, “idiopathic”, and occurs in conjunction with dystonia. Dystonia is often very difficult to describe and is essentially an increased activity of certain groups of muscles causing them to contract of their own accord resulting in body parts adopting abnormal postures, which can result in significant pain and discomfort.
People with dystonia often develop ‘geste antagoniste’, these are tricks e.g. touching side of the face/neck that helps to relieve the dystonic movement. Dystonic tremor, in a manner similar to essential tremor, can occur in two distinct age groups (20-30s) and an older group (50-70s), although there are of course always exceptions. In some cases it also appears to occur in families, such that several members of the same family may be affected but not necessarily in the same way. However, this needn’t always be the case with many individuals reporting no family history.
As is seen with essential tremor, dystonic tremor can affect multiple body parts. Most commonly affected are the hands, head and occasionally voice. Dystonic hand tremor is also described as “Writer’s cramp” where along with the tremor individuals often describe an aching or cramp-like sensation while performing tasks e.g. writing, which often causes them to rub their palms in an attempt to relieve the pain. Head involvement tends to cause the head to nod usually in a ‘no-no’, although sometimes a ‘yes-yes’ direction. In addition to the tremor, the dystonia may also cause the head and neck to adopt a position away from neutral: laterocollis describes the head being tilted to one side or the other, retrocollis refers to a backwards position and anterocollis forwards. Finally, the voice becomes involved when the muscles of the larynx or voicebox are affected, this can alter the tone of an individuals voice and cause it to fluctuate during the course of a conversation.
Dystonic tremor, no matter which part of the body is involved, can have a significant impact upon day-to-day living. As I’m sure most of you are aware the tremor itself can affect day-to-day tasks e.g. writing, pouring liquids, fastening buttons, zips, drinking a cup of tea etc. However, the dystonia itself can also cause significant discomfort and can have as big an impact upon quality of life. For example, pain and discomfort in the neck can make watching television, reading and even driving for any length of time difficult. Individuals with vocal dystonia can also describe some difficulty eating, finding softer foods easier to eat than the more ‘chewy’ variety.
Treatment of dystonic tremor, in many respects, is similar to that of essential tremor. General lifestyle advice such as avoiding stimulants e.g. caffeine, can help to improve symptoms. Stressful situations, or those which cause people to become anxious e.g. eating in restaurants or meeting new people, can also make symptoms worse and in these settings some people find a small quantity of alcohol may improve their symptoms. Doctors may prescribe oral medication i.e. tablets, to try to improve the tremor to some degree. Response to these treatments can vary significantly between individuals. Finally, Botulinum toxin, more commonly known as Botox and, favoured by Hollywood celebrities, can be used to improve the symptoms of dystonia. Small quantities are usually injected into the affected muscle to help to relieve some of the tension and attempt to improve the feelings of ache and discomfort.
Here in Cardiff we are currently looking at the genetic changes that may be responsible for tremor, in the hope that in the long term this may lead to improved therapies. We have spoken before about our research both at the NTF annual meeting and in the newsletter and have had a tremendous response on both occasions. I would like to take this opportunity to thank everyone who has taken part in our research to date. We are currently recruiting families with either essential or dystonic tremor where there are at least 3 or 4 individuals affected by tremor and who may be willing to take part. If you would like any further information please do not hesitate to contact us at PeallKJ@cardiff.ac.uk.