Essential tremor is a condition where a part of a person’s body shakes or trembles uncontrollably when it is held up against gravity.

It is a common movement disorder that for most people is a minor nuisance, but 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 the:

• head
• jaw
• face
• feet
• tongue

Sometimes, the voice can also sound shaky. See symptoms of essential tremor for more information.

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. See treatment of essential tremor for more information.

'Normal' 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 factors 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.

How common is essential tremor?

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 are affected by the condition.

Essential tremor can run in families. At least half of people with the condition have a family member who also has it. See causes of essential tremor for more information.

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:

• arms
• head
• jaw
• face and eyelids
• voice box (larynx), which makes your voice sound shaky
• tongue
• legs or feet (although this is rare)

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 will not usually be present in a body part if it is completely at rest.

The following factors can make the tremor more severe:

• stress 
• anxiety 
• anger
• strenuous activity
• caffeine (found in tea, coffee and cola)
• 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 that are sent along the nerves to the muscles.

However, in some cases the genetic mutation does not always appear to be passed on through a person’s family. The exact cause of essential tremor in people without these gene changes is unknown.

Inherited 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 that you can have to determine whether your essential tremor is caused by one particular faulty gene.

Tremor triggers

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
• eating
• putting on make-up
• shaving

Being tired, anxious, hot or cold is also likely to make your symptoms worse.

Causes of ‘normal’ tremor

There are a number of other conditions or factors that can cause a tremor. These include:

• overactive thyroid (hyperthyroidism), a condition that affects your thyroid gland, which is located in your neck and produces hormones that help regulate important functions of the body, such as heart rate and temperature
• 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; the peripheral nervous system includes the motor nerves that your brain uses to control your muscles
• 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
• too much caffeine, in tea, coffee and cola

It is important that you visit your GP 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.

Ruling out other conditions

There is no specific test that can be used to diagnose essential tremor. Therefore, the condition is usually only diagnosed after your doctor has ruled out other possible causes of tremor, such as Parkinson’s disease (see causes of essential tremor).

You may also be sent to have the following tests to help rule out other possible causes:

• a computerised tomography (CT) scan of the brain, where high-energy radiation is used to produce images that highlight abnormalities in the body’s tissues
• a magnetic resonance imaging (MRI) scan,  where a strong magnetic field and radio waves are used  to produce detailed images of the inside of your body
• urine tests
• blood tests

Occasionally, your doctor may also recommend an electromyography (EMG) test to check the electrical activity of your muscles.

Electromyography (EMG)

Electromyography is a test that measures the health of the muscles and the nerves that control them. It involves inserting fine needles into your muscles. The needles detect any natural electrical activity that is given off by your muscles.

Electromyography provides useful information about how well your muscles are able to respond when a nerve is stimulated and it can indicate whether there is any nerve damage.

There is no cure for essential tremor. Therefore, the aim of treatment is to reduce or remove the involuntary movements as much as possible.

Mild tremor

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 fizzy drinks
• not getting enough sleep
• stress

Moderate tremor

If your tremor is more severe, your doctor may prescribe medication. The most effective medicines are propanolol and primidone. Between half and three quarters of people find that these medicines reduce their tremor.

Propanolol

Propanolol is a beta-blocker that is 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 propanolol include:

• feeling sick
• dizziness
• cold extremities
• impotence 
• worsening of pre-existing asthma or heart failure

Primidone

Primidone is an anticonvulsant and it is 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 propanolol and an anticonvulsant may be recommended.

Sedatives

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 that you may become dependent on them.

Botulinum toxin

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).

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. This procedure is rare.

Severe tremor

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
• thalamotomy

These procedures are described below.

Deep brain stimulation

Deep brain stimulation involves placing one or more electrodes (small metallic discs) in an area of your brain called the thalamus. The electrodes are placed in the brain by inserting fine needles through small holes in your skull. This is done under general anaesthetic, while you are asleep.

Thin wires run from the electrodes to a pulse generator (a device that is similar to a pacemaker), which is implanted under the skin somewhere in your chest. The generator produces an electric current that helps regulate your brainwaves and controls your tremor.

The National Institute for Health and Clinical Excellence (NICE) published guidelines on deep brain stimulation for tremor in 2006. NICE concluded that the treatment is effective in improving tremor, but that more information is needed regarding how successful it is in the long-term. Other research has found that deep brain stimulation can reduce tremor by around 90%.

Possible adverse effects of deep brain stimulation include:

• infection of the surgical scar site
• speech problems
• tingling
• 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, numbness and paralysis (inability to move the affected body part)

Discuss these risks with your surgeon before deciding whether to have the procedure.

In the research that was looked at by NICE, 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 that is produced by the pulse generator.

Thalamotomy

A thalamotomy involves making a small hole in the thalamus, which is the same area of the brain that is 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.