What type of medical conditions cause or are associated
with tremor ?
Tremor, in general, can be associated with a large number of
medical conditions. It is the only symptom in patient with benign
essential tremor and is often a prominent a symptom in patients
with Parkinson's disease. Patients can develop tremor following
a stroke and some patients who have multiple sclerosis may also
develop tremor. Tremor can also occur as a side effect of certain
medications or even from withdrawal of certain medications.
Some individuals have physiological tremor; this can occur when
an individual becomes anxious or stressed. In fact, anxiety
and stress can increase the severity of tremor regardless of
the cause.
How common is Essential Tremor (ET)?
Essential tremor or ET is the most common movement disorder.
In fact, it is nearly 20 times as common as Parkinson's disease.
Men and women are equally affected by ET. The exact prevalence
of ET is difficult to determine and the estimates are quite
variable. One study in which indicated the prevalence of ET
to be somewhere between 4 and 39 cases per 1,000 persons. The
prevalence of ET in persons over 60 years of age is somewhat
higher, between 13 to 50 cases per 1,000 persons. Another report
estimated that in the United States, the prevalence of ET was
300 to 415 per 100,000. ET may affect as many as 10 million
persons in the United States. ET can sometimes be inherited
and for this reasons has also been termed familial tremor.
How is ET inherited?
ET may occur sporadically or may be inherited in which case
it is termed familial tremor. ET is inherited as an autosomal
dominant genetic trait that has variable penetrance. In cases
of familial tremor, children of affected parents have a 50%
risk of inheriting the gene that causes ET and eventually developing
the disorder. In a study of 678 patients published by the Essential
Tremor Study Group, 60% of patients with ET reported a positive
family history. Researchers have been successful in identifying
two separate genes that are believed to be involved in this
disorder. Further characterization of these genes may will hopefully
provide additional information of how ET occurs and perhaps
may help produce additional information that will facilitate
the understanding of motor diseases in general.
What are the features of Essential Tremor (ET) ?
The average age of onset of ET is around 45 years and there
is an increasing incidence with advancing age. Although ET may
begin at any time during life, onset in early childhood is relatively
rare. In some patients, the tremor may begin during the teenage
years, disappear for several decades, and then reappear during
adulthood. ET is usually considered a chronic, slowly progressive
disorder, although in some patients the symptoms may remain
stable and relatively mild throughout life. However, in general,
the tremor tends to worsen with age and as this occurs, there
is a higher likelihood of functional disability leading to increasing
an increasing handicap in performing routine activities of daily
living.
ET usually begins on one side, most commonly involving the
upper extremity. At the beginning, the tremor may only occur
intermittently. As time passes and ET becomes established, it
usually involves both sides (one side is usually affected more
than the other). The tremor is usually absent at rest. It becomes
apparent with sustained posture, and in fact postural tremor
is a major component of ET. The tremor may sometimes be less
evident with movement, but then reappears and becomes worse
with performing goal-oriented tasks; this is a form of kinetic
tremor that is know as intention tremor (the tremor worsens
as the target of the movement is approached). ET as is the cases
with all types of tremor, disappears during sleep. Approximately
50% of patients with ET can suppress the tremor with small quantities
of alcohol. It was previously thought that patients with ET
have no other neurological abnormalities. However, some patients
with ET may also walk in an unsteady uncoordinated fashion.
This associated problem appears to be more common in older patients
who have had ET for more than 5 years.
What if I have tremor in both arms/hands?
Patients who have bilateral tremor have several options? The
first is to perform a thalamotomy on one side followed by a
DBS on the opposite side (generally 6 months apart). Alternatively,
one could first do DBS and later perform a thalamotomy. The
last option would be to place stimulators on both sides, again
about 6 months apart.
Can ET affect areas if the body other than the arm/hand?
Yes. ET most commonly involves the hand and arm. The next
most frequently affected areas in decreasing order are the head,
voice, tongue, lower extremities, and trunk. The tremor in these
other areas of the body may occur as an isolated symptom but
is often associated with hand/arm tremor.
How do I know if my tremor is ET?
It is important that the correct diagnosis of ET be made as
early as possible. Failure to establish the correct diagnosis
can lead to missed opportunities for potentially effective treatment
and may in fact lead to inappropriate treatment. ET is best
diagnosed by a physician who has experience in the diagnosis
and treatment of tremor and other movement disorders. However,
even for very experience movement disorder neurologists, there
are occasions when the diagnosis of ET can be very difficult.
Unfortunately, there is no test that can be done to make the
diagnosis. ET is a clinical diagnosis; in other words, the physician
must make the diagnosis based on the historical information
provided by the patient and the physical examination. It is
critical that the physician obtain a detailed and precise history
of the problem and perform a comprehensive neurological examination
since there are many other diseases that are associated with
tremor. A list of some of the other conditions in which tremor
may be a common symptom are listed below. This list is by no
means all inclusive. These conditions can usually be distinguished
from ET by other abnormal findings. The main point is that correct
diagnosis is also important for these other conditions as they
too require medical attention.
