September 30, 2011
Dear Mayo Clinic:
I am suffering from orthostatic tremor and wonder if there are any clinical studies being conducted on this condition. I am taking .75 milligrams of clonazepam twice a day, but would like more help than it gives.
A tremor is an involuntary, rhythmic body movement. Orthostatic tremor affects the leg muscles when a person is standing and, to a lesser extent, when walking. It may radiate up from the legs to other parts of the body. Orthostatic tremor can be challenging to treat. Although medications help some people, they may not work for everyone. Research exploring new ways to treat orthostatic tremor is under way. At this time, though, drugs such as clonazepam are the most effective option.
"Orthostatic" refers to standing. Orthostatic tremor is characterized by lower limb tremor that is absent when sitting or lying down, but develops when standing. Typically the tremor decreases when a person is walking. Leaning on an object such as a chair or a countertop when standing also may help reduce the tremor.
Orthostatic tremor can significantly affect quality of life. Usually, the main sympton is leg shakiness and unsteadiness when standing. The condition can cause difficulties during daily activities that require free-standing. For example, standing in line at a store, at a kitchen counter to prepare a meal, or at a workbench to enjoy a hobby can be very hard.
Orthostatic tremor typically is not part of any other neurologic condition, such as Parkinson's disease. What causes orthostatic tremor is unknown. Testing, such as brain scanning, does not reveal abnormalities, apart from the tremor itself.
This condition is notorious for having a very high tremor frequency, with rhythmic muscle contractions occurring as quickly as 20 movements per second. This high frequency may sometimes mask the true appearance of tremor and can make the tremor hard to see and difficult to recognize. At Mayo Clinic, we use electrical recording (surface electromyography) to document the presence and frequency of the tremor when a doctor suspects orthostatic tremor.
Once the condition is diagnosed, the usual first-line treatment is clonazepam or a related drug. Clonazepam and other medications from the same drug class are the most consistently effective treatment available. Clonazepam moderately to markedly reduces orthostatic tremor in about one-third of people. In some cases, the condition is almost entirely eliminated.
Unfortunately, this drug may not help everyone, and even when it does, the response may only be partial. Doctors at Mayo Clinic have found that other medication classes are not predictably helpful for orthostatic tremor when clonazepam or related drugs fail, but they are often tried anyway. Hopefully, further research will find more effective drugs.
In rare cases, deep brain stimulation has been used to treat severe orthostatic tremor. Deep brain stimulation involves inserting a long, thin electrical probe into the part of the brain called the thalamus. A wire from the probe is tunneled under the skin to a pacemaker-like device that's placed in the chest. This device transmits painless electrical pulses to interrupt signals from the thalamus that may be causing the tremors. However, treating orthostatic tremor with deep brain stimulation is currently a work in progress. Not many of these procedures have been performed for this condition.
If you are interested in participating in a clinical research trial related to orthostatic tremor, talk to your doctor about studies that may be available in your area. You can refer to several online resources for information, too. Clinical trials available through the National Institutes of Health (NIH) are listed at clinicaltrials.gov. You can search for clinical trials offered through Mayo Clinic at clinicaltrials.mayo.edu.
— J. Eric Ahlskog, M.D., Ph.D., Gastroenterology, Mayo Clinic, Rochester, Minn.