Essential tremor is a type of uncontrollable shake or tremble of part of the body.
It is a common movement disorder that for most people is a minor nuisance, however, it does get gradually worse with time. At its most severe, essential tremor is disabling and makes it very difficult to perform daily activities (see below).
Essential tremor usually affects the arms and hands, although it can also affect other body parts, including head, face, jaw, tongue and feet.
Sometimes, the voice can also sound shaky. Read more about symptoms of essential tremor.
There is no cure for essential tremor, but medicines can be used to help improve the symptoms in at least half of people with the condition. Read more about treatment of essential tremor.
Everyone has a very minor tremor when carrying out daily activities. For example, your hands will shake slightly when you hold them out in front of you. This is normal.
Sometimes, the everyday level of tremor can become more noticeable, particularly in older people. Noticeable tremor is also normal and it is often caused by a raised level of adrenaline in the body, which can happen when a person is stressed, anxious or angry.
It can also occur when a person is taking certain types of medication, such as inhalers for asthma.
When does a tremor become a disorder?
Essential tremor is more severe than normal tremor. It can be made worse by the same things that cause normal tremor, such as stress and anxiety.
Essential tremor gradually gets worse over the years. Eventually, the tremor may become so severe that carrying out normal, everyday activities can become difficult. For example, activities such as writing, drinking a glass of water or tying shoelaces may become particularly challenging.
When to see your doctor
It is important that you visit your doctor if you experience frequent or severe tremors. They will carry out a physical examination to check for tremor when you move.
They will also ask about your medical history and that of your immediate family to find out whether essential tremor runs in your family.
There is no specific test to diagnose essential tremor. The condition is usually diagnosed after clinical assessment.
Who is affected?
Essential tremor affects men and women equally. It can affect people of any age, although it becomes more common with advancing age. Around 4 out of 100 adults over 40 years of age have the condition.
Essential tremor can run in families. At least half of people with the condition have a family member who also has it.
Read more about the causes of essential tremor#a>.
The only symptom of essential tremor is the characteristic shaking. About 9 out of 10 affected people experience a trembling, up-and-down movement of the hands.
Other body parts can also be affected, including the:
- voice box (larynx)
Essential tremor can begin at any age from childhood onwards. The later the condition starts, the milder it is likely to be.
The tremor usually affects both sides of the body equally. It happens when you are trying to hold a position or do something with your hands, such as write. The tremor is not usually present in a body part if it's completely at rest.
The following factors can make the tremor more severe:
- strenuous activity
- caffeine (found in tea, coffee and some fizzy drinks)
- some prescribed medicines
Some people have a mild tremor, although most will find that their tremor gets gradually more severe over the years.
Research suggests that essential tremor may be caused by a change (mutation) in one of your genes. Genes are inherited units of information (DNA) that determine how your body grows and functions.
It is thought that the gene mutation affects the areas of the brain known as the cerebellum and the inferior olive, altering the signals sent along the nerves to the muscles.
Inherited and non-inherited essential tremor
At least half of essential tremor cases are inherited. This means that a faulty gene is responsible for the condition and is passed on to you from your parents. Conditions that are passed on in this way are known as autosomal dominant disorders.
If one of your parents has a faulty gene for essential tremor, you have up to a 50% chance of developing the disorder yourself. However, how old a person is when they first develop the condition and its severity can vary greatly between different family members.
Unfortunately, there is no simple test to determine whether your essential tremor is caused by one particular faulty gene.
There may not always be a family history of essential tremor as not everyone with the mutated gene will develop symptoms. Similarly, some people may develop the mutation without inheriting it from either parent.
Your tremor may be triggered or made worse by one or more of the following actions:
- making controlled or small, detailed movements, such as drinking a glass of water or writing
- putting on make-up
Being tired, anxious, hot or cold is also likely to make your symptoms worse.
Other causes tremor
There are a number of other conditions or factors that can cause a tremor. These include:
- overactive thyroid (hyperthyroidism)
- Parkinson's disease, a long-term condition that affects the way the brain co-ordinates body movements
- multiple sclerosis, a condition of the central nervous system (brain and spinal cord) that affects the senses and the body's actions
- dystonia, a range of movement disorders that cause involuntary muscle spasms
- stroke, which very rarely may result in tremor with few other symptoms
- peripheral neuropathy, where the peripheral nervous system is damaged
- withdrawal symptoms when you stop drinking alcohol, which may affect people who were dependant on alcohol and have stopped or reduced their alcohol intake
- amphetamines and other stimulants
- medications, such as some antidepressants and some medicines that are taken for asthma
- caffeine, in tea, coffee and some fizzy drinks
There is no cure for essential tremor. The aim of treatment is to reduce or remove the involuntary movements as much as possible.
If your tremor is mild and does not stop you from carrying out normal activities, your condition may simply be monitored. You should avoid things that make your tremor worse, such as:
- caffeine, found in coffee, tea and some fizzy drinks
- not getting enough sleep
If your tremor is more severe, your doctor may prescribe medication. The most effective medicines are propranolol and primidone. Between half and three quarters of people find that these medicines reduce their tremor.
Propranolol is a beta-blocker usually used to treat heart disease and high blood pressure (hypertension). It reduces tremors for a few hours after each dose. The possible side effects of taking propranolol include:
[Primidone] is an anticonvulsant, also used to treat epilepsy. Possible side effects include low blood pressure, drowsiness and feeling sick.
Another anticonvulsant, called topiramate, may also sometimes be used. If these medicines do not work on their own, a combination of propranolol and an anticonvulsant may be recommended.
If combining the above medicines does not work, there is some evidence that sedatives such as clonazepam and alprazolam can help. These may improve your tremor because they reduce anxiety, which can often make the tremor worse. However, sedatives can cause drowsiness and there is a risk you may become dependent on them.
In rare cases, if the medicines described above prove to be ineffective, botulinum toxin may be used to treat essential tremor. The botulinum toxin is injected directly into the trembling muscles to block nerve transmissions and relax the muscles.
Botulinum toxin type A is a powerful poison that is clinically safe when used in minute doses. It is sometimes used to treat dystonic tremor, which is a different type of tremor that causes involuntary muscle spasms and contractions (tightening).
Sometimes the essential tremor may be so severe that it significantly interferes with normal activity and does not respond to medication. In these rare cases, surgery may be considered. There are two types of surgery:
- deep brain stimulation
These procedures are described below.
Deep brain stimulation
Deep brain stimulation involves placing one or more electrodes (small metallic needles) in an area of your brain called the thalamus. This is done under general anaesthetic so you are unconscious, though you are woken up during the procedure to make sure that the electrodes are in the correct place.
Thin wires run from the electrodes to a pulse generator (a device similar to a pacemaker), which is implanted under the skin of your chest. The generator produces an electric current that helps regulate your brainwaves and controls your tremor.
Possible adverse effects of deep brain stimulation include:
- infection of the surgical scar site
- speech problems
- bleeding in the brain
- fluid in the brain
- stroke, a serious medical condition that occurs when the blood supply to part of the brain is cut off
- complications of general anaesthetic, such as nerve damage and numbness
Discuss these risks with your surgeon before deciding whether to have the procedure.
A thalamotomy involves making a small hole in the thalamus, which is the same area of the brain targeted for deep brain stimulation. The procedure has been shown to be effective in improving tremor.
Deep brain stimulation is often preferred to thalamotomy because it usually causes fewer side effects and some side effects can be reversed by adjusting the stimulation parameters or abandoning stimulation altogether.
However, thalamotomy has some advantages over deep brain stimulation, such as avoiding the need for follow up appointments to check the pulse generator and replace batteries.
Side effects of a thalamotomy can include:
- confusion and problems thinking
- speech and balance problems
- bleeding in the brain