Essential tremor, also known as kinetic tremor, is the most common movement disorder. In 2012, it was estimated to affect around 2.2 percent of the population in the United States, or between 6.38 and 7.63 million people.
Over half of all cases are thought to be inherited.
It can start at any age, but it is more likely to affect older people, men and women alike.
Symptoms normally start in the hands and arms, and they gradually spread to other parts of the body.
Minor tremor is common as people get older, but essential tremor is more persistent and noticeable, and it tends to get worse gradually. Cognitive impairment and personality disorders have also been linked to the condition.
The hands are most often affected by essential tremor.
The main symptom of essential tremor is trembling, particularly of the hands, which tremble in an up-and-down movement.
Tremor may affect other parts of the body:
- Hands and arms
- Larynx, or voicebox
- Legs and feet, but this is rare.
Signs and symptoms tend to start later on in life. The earlier in life they begin, the worse the condition tends to be, and the worse it gets.
When the body part that is usually affected is at rest, there are no symptoms. The condition seems to be more noticeable when applying a force against gravity. Both sides of the body tend to be equally affected.
In severe cases this movement disorder can be disabling, making it hard for the patient to complete their daily activities, such as drinking a glass of water, tying things up, or writing.
Factors that make symptoms worse include:
- Consumptions of large amounts of caffeine
- Anxiety, stress, and feeling upset
- Strenuous activity
- Certain medications
Although symptoms tend are mild in most cases, they can worsen over time.
Research has linked genetic changes to a higher risk of developing essential tremor. Two genetic variations on different chromosomes have so far been identified, suggesting that the condition is associated with various genes.
The gene mutation is believed to have an impact on brain areas known as the cerebellum and the inferior olive. This alters the way the brain sends signals down the nerves to the muscles.
Around half of all cases of essential tremor are thought to be inherited. It is not known why some patients develop essential tremor when they have no family history or genetic mutation.
Writing is one of several activities that can trigger symptoms of essential tremor.
Some activities can trigger symptoms.
- Applying make-up
- Drinking a glass of water
A lack of sleep can worsen symptoms, and drinking three or more units a day of alcohol increases the risk.
Conditions that are associated with "normal" tremor have also been linked to essential tremor.
Examples are hyperthyroidism, or overactive thyroid, Parkinson's disease, peripheral neuropathy, stroke, dystonia, multiple sclerosis (MS), alcohol withdrawal, illegal drug abuse, and some medications.
When diagnosing essential tremor, the doctor will examine the patient's muscle strength and tendon reflexes among other things.
There is no test for essential tremor, so a physician will rule out possible illnesses and conditions, determine whether there is a family history, and carry out a physical exam.
The doctor will also check what medications the patient is taking.
There are some diagnostic tests for essential tremor. Not everyone undergoes these tests, but doctors sometimes order them to make sure they are not missing another underlying cause of tremor.
These tests may include a CT or MRI scan of the brain. An electromyography (EMG) can determine the electrical activity of the muscles, and it may reveal nerve damage.
A blood test may be carried out, for example, to make sure the thyroid hormone levels are normal.
To evaluate the tremor, the doctor may ask the patient to drink from a glass, hold their hands outstretched, write, or draw a spiral.
The doctor will also examine the patient's muscle strength and tone, tendon reflexes, gait, posture and coordination, and the ability to feel specific sensations.
If symptoms are mild, the doctor may advise no treatment, but if quality of life and the ability to carry out everyday tasks are affected, treatment may be recommended.
Medications for essential tremor
The following medications may help to reduce symptoms:
- Beta blockers, designed to treat hypertension, or high blood pressure, for example, propranolol, atenolol, nadolol, and metoprolol.
- Anticonvulsants, used to treat epilepsy, may be prescribed if beta blockers do not relieve symptoms, for example, primidone, topiramate, and gabapentin.
- Sedatives may be prescribed if the tremors are triggered by tension or anxiety and other medications have not worked, for example, include Valium, or diazepam.
- Botox injections may help if the head or voice are affected. However, treatment is only effective for about 3 months, and it may cause the muscles in the area may become weaker.
Surgery for essential tremor
In rare cases, symptoms may be severe enough to require surgery.
In deep brain stimulation, electrodes are placed in the thalamus, which is in the brain. Fine needles go through tiny holes in the skull, while the patient is under general anesthetic.
Thin wires connect the electrodes to a pulse generator device that is implanted under the skin in the chest. The generator helps regulate brainwaves and control tremor by sending electric currents.
Deep brain stimulation has been found to reduce tremor by 80 percent and to improve handwriting by 70 percent. The improvement appeared to be sustained long-term.
Side effects are rare, but they may include fluid in the brain, infection of the surgical scar, tingling, and bleeding in the brain. Stroke is also a very rare risk.
Thalamotomy involves making a small hole in the thalamus. This is considered as effective as deep brain stimulation in reducing tremors, but deep brain stimulation has fewer side effects.
Physical therapy can help some patients to control their tremors and improve their muscle control and coordination.
An occupational therapist may suggest some adaptations to make daily activities easier, such as using heavier cups and utensils, using thick pens and pencils, and using wrist weights.