Many people worry when they have a tremor that it may be a sign of Parkinson's disease. However, there is another more common cause of tremor that does not have the serious implications of Parkinson's. In essential tremor (ET), there is no worsening unsteadiness or rigidity as there is in Parkinson's disease. There is also no associated dementia. ET is more than ten times as common as Parkinson's disease.
Although it might be a relief to hear that your tremor isn't caused by Parkinson's disease, it doesn't necessarily make the tremor less annoying. For some people, essential tremor comes and goes and hardly bothers them. For others, essential tremor is so bad that tying shoes or eating with utensils is nearly impossible.
How Do I Recognize Essential Tremor?
Unlike a Parkinsonian tremor, essential tremor is usually (but not always) bilateral -- that is, it affects both sides at once. The hands tend to be the most involved part of the body, although the head can also be involved. Another distinction from Parkinson's is that the tremor tends to be worse when the hands are being used instead of when they're at rest.
Other clues include a family history of tremor. Essential tremor is often inherited in an autosomal dominant fashion, meaning that if you have it, there's a good chance at least one of your parents did, too. Another interesting hallmark of essential tremor is that it frequently improves after drinking a modest amount of alcohol.
How Common is Essential Tremor?
About 10 million Americans have essential tremor. That's about 5% of all people in the United States.
Like many health changes, essential tremor tends to increase as we get older. The tremor increases in amplitude, becoming larger and more noticeable with time. It may also spread to other body regions.
What Causes Essential Tremor?
The parts of the brain responsible for coordinating movement are something like different sections of an orchestra. Every section has its own rhythm, which is usually in synchrony with the other parts. The rhythm of essential tremor is about as fast as the natural rhythm produced by the thalamus and the inferior olivary nucleus of the brainstem, both of which are known to be involved with movement. These areas are also very active on PET scans during tremor.
It's not clear why these areas may become abnormally active. Despite there being a frequent family history of tremor in people with ET, no gene has been clearly identified. Some people have suggested that some environmental factors, like some chemicals found in well-cooked meat, might be involved. No association has been found with pesticides or organic solvents.
What Makes Essential Tremor Worse?
In addition to getting older, essential tremor can be worsened by things that we might experience every day. Fatigue, changes in temperature, emotional stresses, and even normal changes in how sleepy you are can change the severity of the tremor.
There's also a wide number of different drugs that worsen tremor. Those drugs include drugs that act on the central nervous system like antidepressants, Reglan, lithium, and alcohol, as well as stimulants like caffeine, bronchodilators or cocaine. Steroids can worsen tremor, as can thyroid hormones. In fact, there are so many different medications that can worsen tremor, it's probably best to just pay close attention to the timing of your tremor, and become familiar with the side effects of any medication that you're taking.
How Can the Neurologist Be Sure My Tremor Isn't Parkinson's Disease?
Usually, just talking to you and looking at your tremor will be enough for a neurologist to diagnose essential tremor. Sometimes it takes time to be sure. Essential tremor tends to change more slowly than Parkinson's disease.
In confusing cases, a test called a DaTscan can be done to look at the substantia nigra, which are parts of the brain that are worn down in Parkinson's disease. This scan uses a radioisotope to look at the activity of basal ganglia. In essential tremor, the scan will be normal.
How Can The Tremor be Treated?
There are many different ways to manage essential tremor. Depending on how severe the tremor is, the best option may be no medical therapy at all. Since every treatment comes with some risk of side effects, if the tremor isn't particularly bothersome, then there's no need to be aggressive with medications or other therapies.
However, if the tremor is getting in the way of day-to-day living, then medications, such as propranolol or primidone, may be helpful. If these don't work, other medications may be tried, including Botox injections for head or voice tremor. In the most severe cases, surgical options, such as deep brain stimulation, may be considered.
While essential tremor can be a nuisance, it is not life-threatening. If the symptoms are preventing you from doing things that you want or need to do, however, you should speak with a qualified physician about the best way to manage your symptoms.
ED Louis, Zheng W, Jurewicz EC, Watner D, Chen J, Factor-Litvak P, Parides M. Elevation of blood beta-carboline alkaloids in essential tremor. Neurology. 2002 Dec 24;59(12):1940-4.
ED Louis, Agnew A, Gillman A, Gerbin M, Viner AS.Estimating annual rate of decline: prospective, longitudinal data on arm tremor severity in two groups of essential tremor cases.J Neurol Neurosurg Psychiatry. 2011 Jul;82(7):761-5. Epub 2011 Mar 24.
Kathleen Poston, Overview of Common Movement Disorders, Continuum : Movement Disorders Volume 16, Number 1, February 2010