Essential tremor is a type of uncontrollable shake or tremble of part of the body.
Most people with essential tremor experience a trembling, up-and-down movement of the hands.
The arms, head, eyelids, lips and other muscles can also be affected. A tremor in the voice box (larynx) may cause a shaky voice.
Essential tremor is usually more noticeable when you're trying to hold a position or do something with your hands, such as write. It doesn't always affect both sides of the body equally.
Essential tremor is a common movement disorder affecting around four out of 100 adults over 40 years of age. Some people only have a mild tremor at first, which usually gets more severe over time.
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's often caused by a raised level of adrenaline in the body, which can happen when a person is stressed, anxious or angry.
When does a tremor become a problem?
Essential tremor is more severe than normal tremor and it gradually gets worse over time. Eventually, the tremor may become so severe that carrying out normal, everyday activities can become difficult.
Certain things may temporarily increase any tremor, including:
tiredness caused by strenuous activity or lack of sleep
caffeine – from tea, coffee and some fizzy drinks
being very hot or cold
taking certain medicines – including some antidepressants and treatments for asthma
When to see your GP
It's important to visit your GP if you experience frequent or severe tremors.
Although there's no specific test to diagnose essential tremor, your GP can carry out a physical examination and may request further tests to rule out other conditions (see causes, below).
They'll also ask about your personal and family medical history as part of their assessment.
Treating essential tremor
There's no cure for essential tremor, but medicines can be used to help improve the symptoms in at least half of people with the condition.
In rare cases, a severe tremor may be treated with surgery if it doesn't respond to medication.
Inherited essential tremor
Essential tremor can run in families and research suggests it's passed on by a faulty gene. At least half of people with the condition have a family member who also has it.
However, the age at which a tremor develops and its severity can vary greatly between different family members. Some people may also develop the faulty gene without inheriting it from either parent.
Other causes of tremor
There are a number of conditions which may cause tremor, including:
overactive thyroid (hyperthyroidism)
Parkinson's disease, a long-term condition affecting the way the brain co-ordinates body movements
multiple sclerosis, a condition of the central nervous system (brain and spinal cord) affecting the senses and the body's actions
dystonia, a range of movement disorders which 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
A tremor can also be one of the withdrawal symptoms for people who are dependant on alcohol and have stopped or reduced their alcohol intake.
Treating essential tremor
Treatment for essential tremor aims to reduce or remove the involuntary movements as much as possible.
If your tremor is mild and doesn't stop you from carrying out normal activities, your condition may simply be monitored. Try to avoid things that may make your tremor worse, such as:
caffeine; found in coffee, tea and some fizzy drinks
not getting enough sleep
Speak to your GP if you're taking medicine which could be causing a tremor. You should only stop taking prescribed medication if your doctor specifically advises you to.
If your tremor is more severe, your doctor may prescribe medication to reduce your symptoms. The most effective medicines are propranolol and primidone. Between half and three quarters of people find 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:
worsening of pre-existing asthma or heart failure
Primidone is an anticonvulsant, used to treat epilepsy, which also seems to help reduce essential tremor. Possible side effects include low blood pressure, drowsiness and feeling sick.
Another anticonvulsant, called topiramate, may also sometimes be used. If these medicines don't work on their own, a combination of propranolol and an anticonvulsant may be recommended.
If combining the above medicines doesn't work, there's 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's 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's clinically safe when used in minute doses. It's sometimes used to treat dystonic tremor rather than essential tremor. Dystonic tremor is a different type of tremor which causes involuntary muscle spasms and contractions (tightening).
Surgery for severe tremor
Sometimes the essential tremor may be so severe it significantly interferes with normal activity and doesn't 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're unconscious, though you are woken up during the procedure to make sure 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 to help regulate your brainwaves and control your tremor.
The National Institute for Health and Care Excellence (NICE) published guidelines on deep brain stimulation for tremor in 2006. NICE concluded the treatment is effective in improving tremor, but more information is needed about how successful it is in the long-term. Other research has found deep brain stimulation can reduce tremor by around 90%.
Possible adverse effects of deep brain stimulation include:
infection of the surgical scar site
bleeding in the brain
fluid in the brain
stroke, a serious medical condition caused by the blood supply to part of the brain being 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.
In the research NICE looked at, side effects were relatively rare. More recent research has also concluded that deep brain stimulation is a relatively safe procedure. Certain side effects can be eliminated by adjusting the level of stimulation produced by the pulse generator.
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
If you're affected by essential tremor, you can call the National Tremor Foundation (NTF) for help and support.