Q: I have a primary orthostatic tremor, an extremely rare condition. Do you have any background working with this tremor?
A: No, however, perhaps I can shed some light on the condition and perhaps answer some questions you might have. A primary orthostatic tremor is a rare movement disorder characterized by a tremor that generally occurs in the legs while standing and markedly decreases or completely disappears when the individual sits, walks, or lies down. It causes an overwhelming feeling of unsteadiness, almost forcing affected individuals to move quickly or find a place to sit down to avoid falling. The tremor may not be visible to the naked eye; however, palpation of the thighs or calves or listening with the aid of a stethoscope will reveal a rhythmic contraction of the muscles involved. Some individuals may be able to stand for several minutes before the tremor begins, while others can only stand for a very brief period of time. Interestingly, the condition will not develop into a more serious condition, nor will it affect any other bodily systems. Further and while not as common, some individuals may have a tremor in the upper extremities instead of the legs.
Primary orthostatic tremor is sometimes referred to as “shaky legs syndrome”. It is a major problem for those individuals who suffer from the condition as it cannot be ignored, can cause falls, serious injuries and embarrassment and affects quality of life. The exact cause for it remains unknown. It was first described in 1984, some 30 years ago, and even today’s medical literature is controversial as to whether it is a variant of essential tremor or a separate entity. Some individuals so diagnosed are known to have a family history of tremor, suggesting that genetic factors may play a role but a great deal more research is necessary to determine the precise underlying cause(s) for the disorder. It is understandable that many cases of primary orthostatic tremor are misdiagnosed, making it difficult to determine how many individuals may actually be affected; however, more than 200 cases involving both men and women have been reported in medical literature over the past 30 years.
Diagnosis is based on a detailed patient history and thorough clinical evaluation and is further supported by tests such as electromyography that measures electrical impulses of the involved muscles during contraction and at rest. Misdiagnosis is rather common since many patients may be suspected of having a psychological cause for the tremor rather than a physical one.
Treatment is generally provided through oral medication such as clonazepam (Klonopin), yet not all individuals respond favorably to first-line drug therapy. Some patients may respond favorably to gabapentin (Neurontin), an anti-seizure drug, or to other prescription medications. Medical literature has also indicated that some cases have been successfully treated by thalamic deep brain stimulation, yet again, additional research is necessary before effectiveness and long-term safety can be properly determined.
Ongoing clinical trials are posted through www.clinicalatrials.gov. Beyond this, information on clinical trials can be checked through the National Institutes of Health Clinical Center by calling 1 800-411-1222 or through email at prpl@cc.nih.gov.
