About 10 years ago, Ruth Hochheiser began noticing an uncomfortable sensation in her legs while standing still. It wasn't pain exactly, just discomfort, and it progressed over the next six years. More and more often, she felt compelled to march after standing for brief periods of time. “My legs felt like wooden poles, and then like lead, and then my whole body felt like it was being pulled down to the center of the earth,” says Hochheiser, who is now 73 and lives in Wilmington, DE.

When the sensation worsened to the point where her balance and ability to walk were affected, she sought help from medical professionals. After her primary care doctor, a physiatrist, and a neurologist couldn't pinpoint the cause, Hochheiser was referred to a neurosurgeon on the presumption that the problem was in her back. “The neurosurgeon couldn't find anything wrong other than stenosis, which he said pretty much anyone my age would have.”

The doctor did refer Hochheiser to a colleague, a neurologist he described as a “troubleshooter.” While the troubleshooter couldn't solve the mystery, she knew enough to send Hochheiser to a movement disorder specialist. “Within 10 minutes, he knew what it was and told the resident to listen to the back of my knees with a stethoscope, because they sounded like the whirring of a helicopter,” Hochheiser says.

Her diagnosis was orthostatic tremor, a movement disorder that typically causes tremor in the legs when standing that partially or completely disappears when sitting or walking. The extreme speed of the tremor makes it almost invisible and produces a helicopter-like sound that can be heard with a stethoscope.

“The condition is characterized by high-frequency tremor of around 13 to 20 hertz per second,” says Robert Chen, MD, a movement disorder specialist and professor of neurology at the University of Toronto. “It happens when bearing weight or standing, though in some cases it can occur in the arms upon leaning.” In general, patients feel normal while sitting and experience symptoms when they stand, says Anhar Hassan, MB, BCh, FAAN, a movement disorder specialist at Mayo Clinic in Rochester, MN. As the disease progresses, she adds, symptoms begin almost immediately upon standing, and patients need to sit, lean, or walk to alleviate them.

The cause of orthostatic tremor is not well understood but may originate in the brain stem or cerebellum, Dr. Chen says. Unlike more common types of tremor, such as Parkinson's and essential tremor, orthostatic tremor is not usually degenerative. It differs in other ways as well. Parkinson's tremor and essential tremor present asymmetrically—each side of the body tremors at its own rate. And often, but not always, the tremor starts on one side, says Allan Wu, MD, FAAN, professor of neurology at the Northwestern University Feinberg School of Medicine in Chicago. “Orthostatic tremor is always synchronous—both sides of the body tremor at the same time, which reinforces the effect of the tremor,” Dr. Wu adds.

And while orthostatic tremor occurs during standing, “in Parkinson's, tremor happens when the patient is relaxed. Essential tremor occurs when someone stretches his or her arms or reaches for objects,” Dr. Chen says.

Few epidemiologic data exist on orthostatic tremor, so its incidence and prevalence are unknown. But it appears to be far rarer than Parkinson's-related tremor (which affects nearly 70 percent of the 1 million Americans who have the disease) or essential tremor (affecting about 10 million people in the United States).

Electrophysiologic studies of the leg muscles can confirm response and enable a physician to pick up the very fast tremor once the patient stands, says Dr. Hassan. This procedure is critical, she says, because other conditions can mimic orthostatic tremor. “There are many reasons people stand up and feel shaky, including orthostatic myoclonus, neuropathy, and other disorders that affect balance. All of those mimicking conditions can clearly be separated from orthostatic tremor by electrophysiologic studies.”

Some patients may not get tested for orthostatic tremor if they are perplexed by their symptoms or don't see a doctor with the right expertise. Hilda Nafarrate, 78, of Bow, NH, began having what she thought of as vibrations in her legs, followed by weakness, in 2011. When a neurologist first asked her whether the vibrations ceased when she sat down, she told him no. In hindsight, she realizes they stopped eventually after sitting. “I think my doctor was onto something, but I used the wrong terminology. If I'd described my symptoms differently, I might have been diagnosed then,” says Nafarrate.

An avid golfer, Nafarrate says her symptoms progressed for several years until she could no longer stand and hit through the ball. At home, she had to lean against the sink or sit on a stool when doing housework. In 2019, feeling very frustrated, Nafarrate searched the term “invisible leg tremors” on her computer. “Bingo—it came up,” she says. “I went to see a movement disorder specialist, who diagnosed me with orthostatic tremor.”

Varying Medications

The best treatment for orthostatic tremor is a benzodiazepine medication such as clonazepam (Klonopin), which is typically used to prevent and treat conditions such as seizures, anxiety, and other movement disorders, says Dr. Hassan. Possible side effects include sedation or worsening balance, especially in older people. Other treatments include beta-blockers and anticonvulsants like primidone (Mysoline), gabapentin (Horizant), and valproate (Depakote). However, Dr. Hassan says, “studies are lacking about the effectiveness of treatment.” And because orthostatic tremor is so rare, it's difficult to recruit enough patients for a large enough sampling to conduct a drug trial. 

Hochheiser began taking clonazepam shortly after her diagnosis and later added gabapentin; both medications improved her symptoms. “The combination was very successful for me,” she says. “Prior to COVID-19, my body was working, and my husband and I were doing a lot of traveling and hiking, though I kept trekking poles in my car in case I needed them.”

After the pandemic hit and Hochheiser began spending more time at home, her doctor lowered her dosage. When society began opening back up and life became more active, her doctor slowly increased the dosage; however, the drugs haven't had the same mitigating effect on her symptoms, and one of the side effects she's experienced from the drugs has been depression.

Nafarrate takes primidone, which only partially controls her symptoms. “I often use a cane for balance and grip the floor with my toes because I become unsteady so easily.” For now, her symptoms are manageable. “I feel that the medication has calmed my tremors considerably, but things aren't perfect,” Nafarrate says. “And I know it's a progressive syndrome, so who knows what's to come?”

Research into other types of treatments is ongoing, but uncertainty about the cause of orthostatic tremor complicates matters, says Dr. Hassan. “When we look at brain scans or blood tests of patients with this type of tremor, we don't see any obvious abnormality,” says Dr. Hassan. One theory suggests it stems from a problem in the cerebellum, which is the balance center at the back of the brain, but tremors from disorders of the cerebellum are usually slow, while orthostatic tremors are fast. “There seems to be some dysfunction there, but it still isn't completely understood,” Dr. Hassan says.

An option for people with symptoms uncontrolled by medication is deep brain stimulation (DBS), a procedure in which electrodes are implanted in the brain to deliver high-frequency stimulation. In some studies, the surgery provided a modest benefit. “It may increase standing time up to five minutes, and the tremor severity is lessened,” says Dr. Hassan. “This can allow patients to stand long enough to brush their teeth, take a shower, or pose for a family photo, where they could not do this activity before.” The long-term outcomes of DBS for orthostatic tremor are not yet known, she adds.

Today, Hochheiser's condition has worsened to the point where she can't dance, hike, or do other activities she once enjoyed. “This is a very difficult disease because it affects not only your physical body but your emotional world. I just feel sad that my body can't do what it used to do.” She's also fearful. “Occasionally my legs freeze up and I feel like I need to be rescued,” she says. “I use my trekking poles as security.”

Despite the challenges, Hochheiser continues to work out in her home gym. She also meditates to deal with the emotional challenges of living with the disorder. “I meditate on acceptance, gratitude, and connecting to the divinity of the universe and my deceased parents for watching out for me.”

In addition, Hochheiser has dedicated herself to raising awareness about orthostatic tremor so patients and physicians might recognize it when they see it. She's written letters to the National Organization of Rare Disorders and the National Institute of Neurological Disorders and Stroke. “We need more doctors to know about this disease, we need accurate diagnoses, and we need funds for research.”

Current Research on Orthostatic Tremor

Studies on orthostatic tremor are limited because the pool of people with the condition is so small, but research is focused mainly on improving treatment options, says Anhar Hassan, MB, BCh, FAAN, a movement disorder specialist at Mayo Clinic in Rochester, MN. Because of recruitment challenges, Dr. Hassan says, clinics must collaborate to get enough patients. Here are two studies that may provide important insight into the condition.

Topic: Thalamic Deep Brain Stimulation

• Summary: In this 2017 study, researchers analyzed the experiences of 17 patients—15 women and two men, ranging in age from 37 to 73—with medication-resistant orthostatic tremor who were treated with deep brain stimulation.
• Conclusion: The procedure was safe and well tolerated. Most patients reported some improvement in their daily lives in the short term, although that improvement gradually decreased among the eight patients who participated in long-term follow-up. Three patients reported no or minimal improvement after the procedure.
• For more information: Call Aristide Merola, MD, PhD, at the Ohio State University Wexner Medical Center, at 614-293-4969.

Topic: Literature on Orthostatic Tremor

• Summary: This 2016 review examined 219 studies published between 1966 and 2016 and accessed using the terms “orthostatic tremor” and “shaky leg syndrome.” The literature includes data on cause, physiological changes, diagnostic approaches, treatment strategies, and outcomes.
• Conclusion: Orthostatic tremor is a progressive disorder with varying symptoms depending on whether it's related to another condition. For example, a patient with Parkinson's disease and orthostatic tremor may have other symptoms, such as cognitive impairment and personality disturbances, while a person who has only orthostatic tremor will not.
• For more information: Email Julián Benito-León, MD, PhD, at University Hospital in Madrid, Spain, jbenitol67@gmail.com.

Resources for Patients with Orthostatic Tremor

• American Academy of Neurology: BrainandLife.org
• International Parkinson and Movement Disorder Society: movementdisorders.org; 414-276-2145
• National Institute of Neurological Disorders and Stroke: ninds.nih.gov; 800-352-9424
• National Organization for Rare Disorders: rarediseases.org; 617-249-7300
• National Tremor Foundation: tremor.org.uk
• Primary Orthostatic Tremor Facebook group: facebook.comr