We use our hands constantly. Every morning millions of people shower,
shave, get dressed, eat breakfast — tasks that would be incredibly
difficult without steady hands. For an estimated 10 million Americans
with a neurological disorder called essential tremor, shaking of their
arms and other body parts makes it difficult or even impossible to
perform the simplest of movements.
The condition, which affects the muscles of the hands, head, and voice,
is often mistaken for Parkinson's patients. But essential tremor is 5-10
times more common than Parkinson's disease. Most people diagnosed with
essential tremor have action tremor, which means they shake when they
move, and some develop a distinctive nodding or shaking of the head.
People with Parkinson's usually experience tremors at rest, along with
stiffness and slowness of movement.
But there's some overlap between the two conditions. Some studies show
that 90% of Parkinson's patients have action tremor and 20% of people
with essential tremor have tremor at rest. Both conditions cause a loss
of the sense of smell, but in essential tremor it's usually milder. Patients
with essential tremor can go on to develop Parkinson's disease, but how
many do so isn't known.
Katherine Hepburn had essential tremor. Medical historians believe the
playwright Eugene O'Neill and the American revolutionary Samuel Adams
may have also had the disease. Researchers have diagnosed Adams by analyzing
the handwriting in his letters.
Medical texts from ancient India and Greece mention tremors. Charles
Dana, the famous 19th-century neurologist, wrote detailed case histories
of people with tremors. Despite this long history, essential tremor isn't
fully understood. Most experts believe that it's caused by the death
or malfunction of brain cells in the cerebellum, the part of the brain
that controls movement and balance. But in contrast to Parkinson's, characterized
by a shortage of dopamine, a brain chemical involved in movement, essential
tremor doesn't seem to involve any neurotransmitter abnormalities.
Essential tremor runs in families; in fact, it's sometimes referred
to as familial tremor. But studies of identical twins have shown that
it's not completely inherited, suggesting an environmental factor may
trigger some cases, although what that might be is unknown.
Misdiagnosis of essential tremor is a problem. Doctors don't have a
definitive test, so some people are given Parkinson's medication when
they shouldn't be. The first steps in making the diagnosis are taking
a family history and ruling out other causes of tremors, which include
excessive caffeine, stress, fatigue, anxiety, and hyperthyroidism. There
are also some less common neurological disorders that cause shaking,
including dystonia and Wilson's disease.
Many people with essential tremor discover, sometimes inadvertently,
that alcohol eases the shaking. As a result, some people with the condition
end up drinking too much.
Beta blockers — especially a long-acting version of propranolol
(Inderal) — are one of two main medications used to treat essential
tremor. Adrenaline makes tremors worse, and beta blockers, which are
usually prescribed for high blood pressure and heart conditions, block
adrenaline. (The term "beta blocker" is shorthand for beta-adrenergic
blocker; "adrenergic" refers to compounds like adrenaline.) Studies show
that beta blockers help 45%-75% of patients.
The other main drug is primidone (Mysoline), an anticonvulsant. Anticonvulsants
work by reducing the excitability of nerve cells. Primidone is about
as effective as propranolol, but it can cause nausea, vomiting, and ataxia
(problems with movement). Studies of another anticonvulsant, topiramate
(Topamax), are promising, but a high proportion of patients experience
side effects. Many sufferers eventually need to take propranolol (the
beta blocker) and primidone together to get adequate relief, leading
some researchers to think the condition has multiple causes.
Surgery is an option for people with severe tremors, but operating on
the brain obviously carries risk. Thalamotomy, introduced in the 1950s
to help Parkinson's patients, destroys part of the thalamus, a region
of the brain involved in involuntary muscle movement. It's a fairly effective
operation, but possible side effects include difficulty swallowing or
talking and an increased risk of stroke.
Deep brain stimulation is another procedure. It involves placing electrodes
in the brain that are connected to a pacemaker-like device implanted
in the patient's chest. The device sends small electric impulses through
the electrode. The impulses interrupt the communication between cells
involved in tremors.
How treatment can help
A. Spiral drawn by essential tremor patient not receiving any
B. Essential tremor patient receiving trial dose of a drug
C. Essential tremor patient receiving more effective dose of
December 2004 Update
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