Wikipedia Definition

[Lynda29]

Essential tremor (ET) is a progressive neurological disease whose most
recognizable feature is a tremor of the arms that is apparent during
voluntary movements such as eating and writing. This type of tremor is
often referred to as "kinetic tremor". The tremor may also occur in
the head (neck), jaw and voice as well as other body regions, with the
general pattern being that the tremor begins in the arms and then
spreads to these other regions in selected patients. Women are more
likely to develop the head tremor than are men. Other types of tremor
may also occur, including postural tremor of the outstretched arms,
intentional tremor of the arms and rest tremor in the arms. Some
patients may have unsteadiness and problems with gait and balance that
are above and beyond that due to normal aging. In addition to these
motor problems, a variety of non-motor features have recently been
linked with ET. These include anxiety and depressive symptoms as well
as cognitive difficulty. Recent studies have demonstrated that old-
onset ET (onset > age 65) may be associated with an increased risk of
developing dementia. ET is one of the most common neurological
diseases, with a prevalence of approximately 4% in persons aged 40 and
older and considerably higher among persons in their 60s, 70s, 80s,
and 90s. Aside from enhanced physiological tremor, it is the most
common type of tremor and also one of the most commonly observed
movement disorders. Essential tremor was also previously known as
"benign essential tremor", but the adjective "benign" has been removed
in recognition of the sometimes disabling nature of the disorder.
Although often mild, patients with severe tremor have difficulty
performing many of their routine activities of daily living.

Cause:
The underlying etiology is not clear but many cases seem to be
familial. It has been estimated that approximately one-half of the
cases are due to a genetic mutation and the pattern of inheritance is
most consistent with autosomal dominant transmission. As of yet, no
genes have been identified but genetic linkage has been established
with several chromosomal regions. A number of environmental factors,
including toxins, are also under active investigation and these may
play a role in disease etiology. In terms of pathophysiology,
clinical, physiological and imaging studies point to an involvement of
the cerebellum and/or cerebellothalamocortical circuits. Recent
postmortem studies have demonstrated the presence of degenerative
changes in the ET brain, with these changes including Purkinje cell
axonal swellings and Purkinje cell loss in the majority of cases and
brainstem Lewy bodies in the remainder. These studies suggest that the
disease is both heterogeneous and degenerative. In other words, ET
might be a family of degenerative diseases rather than a single
disease.

Diagnosis:
Usually the diagnosis is established on clinical grounds. Tremors can
start at any age, from birth through advanced ages (senile tremor).
Any voluntary muscle in the body may be affected, although the tremor
is most commonly seen in the hands and arms and slightly less commonly
in the neck (causing the patient's head to shake), tongue, and legs. A
resting tremor of the hands is sometimes present.

ET does sometimes occur in combination with other neurological
disorders such as dystonia. In addition, there may be a link between
ET and Parkinson's disease, with one study showing ET patients having
an approximately 4 times greater likelihood of developing Parkinson's
disease.

Symptoms:
Essential tremor generally presents as a rhythmic tremor (4–12 Hz)
that is present only when the affected muscle is exerting effort (in
other words, 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 psychosomatic origin.

Tremor intensity can worsen in response to fatigue, strong emotions,
low blood sugar, cold, caffeine, lithium salts, some antidepressants
or other factors. It is typical for the tremor to worsen in
"performance" situations, such as when making out a check at a
checkout stand.

ET-related tremors do not occur during sleep, but patients sometimes
complain of an especially coarse tremor upon awakening that becomes
noticeably less coarse within the first few minutes of wakefulness.

In mild cases, ET can manifest as the inability to stop the tongue or
hands from shaking, the ability to only sing in vibrato, and
difficulty to do small precise tasks such as threading a needle. In
disabling cases, ET can interfere with a person's ability to perform
tasks of daily living, including feeding, dressing, and activities of
personal hygiene.

ET is generally progressive in most cases (sometimes rapidly,
sometimes very slowly), and can be disabling in severe cases.

Treatment:
Drug treatment may include tranquilizers, beta-blockers, or
antiepileptic drugs. Surgical treatments (which are generally reserved
for the most severe cases) include thalamotomy and deep brain
stimulation.

The two medications that are prescribed most commonly for control of
ET symptoms are the anticonvulsant Primidone (Mysoline) and the beta-
blocker propranolol (Inderal). Self medication with small amounts of
alcohol has been shown to give short term relief from tremor.

Minor cases of ET can be treated with physical therapy and development
of the muscles in the sections of the body that are severe in their
shaking.

There is evidence that ET can be resolved with acupuncture