Essential tremor (ET) generally presents as a rhythmic tremor that is present only when the affected muscle is exerting effort (ie, it is not present at rest). Any sort of physical or mental stress will tend to make the tremor worse, often creating the false impression that the tremor is of somatic origin. It is typical for the tremor to be worse in "performance" situations, eg, when making out a check at a checkout stand. This is due to the increased stress in such situations.
It may be found in more than one member of a family (familial tremor) in which case it is usually dominant in inheritance, or it may occur with no family history. The tremor may start as any age, from birth through advanced ages (senile tremor). Any voluntary muscle in the body may be affected, though it's most commonly seen in the hands and arms and slightly less commonly in the head, voice and eyelids. It is usually painless, though in some cases tremor of the head or neck may cause pain.
The cause of the disease is unknown, and there is no identifiable structural abnormality in the nervous system of the patients. Usually the diagnosis is established on clinical grounds, but in cases of suspect, other diseases causing tremor (excessive caffeine consumption, drugs, hyperthyroidism) might better be excluded. The tremors are usually evoked by anxiety and may lessen by alcohol. However using small amounts of alcohol for treatment may cause alcohol addiction.
Essential tremor is not related to Parkinson's disease. Though some statistics seem to indicate that there is a slightly increased chance of developing Parkinson's for people with ET, this statistical finding may be due to people with Parkinson's being initially misdiagnosed with essential tremor.
Essential tremor does sometimes occur in combination with other neurological disorders such as dystonia and benign fasciculation syndrome. However, there is no clear evidence that having ET predisposes a person to one of these diseases.
While essential tremor may be progressive (sometimes rapidly, sometimes very slowly), and can in severe cases be disabling, it is not life-threatening and does not affect lifespan.
Treatment of essential tremor may or may not be attempted, depending on the severity of the tremor and the physical and social handicaps that implies. Drug treatment may include tranquilizers, beta-blockers, and anti-seizure drugs. Surgical treatments (which are generally reserved for the most severe cases) include botulism toxin injections into the affected muscles, thalotomy, and "deep brain stimulation", the insertion of a "pacemaker" into the brain.