After a 70-year-old woman started experiencing "pain and instability when she stood up," along with a "constant need to walk, once upright," she went to several doctors who couldn't determine the cause of her symptoms. But then, a doctor who had recently completed his training diagnosed her with a rare movement disorder, Lisa Sanders writes for the New York Times Magazine.

She was exhausted 'as if she'd run a marathon'

About 10 years ago, the 70-year-old woman started to notice that it was hard for her to stand still. "After a minute or two, she would get this overwhelming sensation that she had to either move or sit down," Sanders writes. "Around that time, she also noticed an ache deep in the muscles of her legs whenever she stood up."

The only thing that helped relieve the woman's pain was sitting or lying down. However, she tried to live her life normally, which included staying active and taking frequent trips.

Then, when the woman and her husband were preparing to travel to Europe for a cruise through the Rhine Valley, she noticed that she was having trouble walking.

The most difficult part of the trip for the woman was the walking tours, largely because the tour guides walked slowly. "It was almost as bad as standing still," Sanders writes. Even when the couple walked ahead of the group, the woman was exhausted, "as if she'd run a marathon," by early afternoon.

'He heard a flit-flit-flit'

After the onset of her symptoms, the woman saw around a half dozen doctors. Initially, she saw an orthopedic surgeon—he couldn't figure out why she was unable to stand still. When he evaluated her joints and muscles, he found that she had good range of motion and normal muscles. While an MRI found some spinal stenosis, the orthopedic surgeon told her there was nothing he could operate on.

A few years after she saw the orthopedic surgeon, the woman saw a neurologist. However, none of her symptoms pointed to a clear diagnosis. The neurologist did not find anything after a nerve-conduction study, and a new MRI only revealed more spinal stenosis.

Then, the woman saw a neurosurgeon. She told the neurosurgeon that the only abnormality any of her doctors could find was spinal stenosis.

When the patient asked if surgery could help her regain mobility and balance, the neurosurgeon said he did not know what was wrong with her legs but noted that he was confident the spinal stenosis was not causing her symptoms.

The neurosurgeon referred the woman to another neurologist, named Thomas Tropea, who specialized in movement disorders. Tropea had recently completed his training before joining the faculty at University of Pennsylvania's Perelman School of Medicine.

According to Sanders, as soon as the patient started describing her symptoms, including "the pain and instability when she stood up that was completely absent when she was off her feet and the constant need to walk, once upright," Tropea was intrigued.

He asked the woman to stand up and walk around the exam room—tasks she completed easily. "The pain and unsteadiness she felt while standing completely resolved with motion," Sanders notes.

When Tropea placed his stethoscope on the back of the patient's knees, "he heard a flit-flit-flit, almost like a helicopter's rotors."

He immediately recognized the condition—a rare disorder called orthostatic tremor (OT).

"The woman was amazed and confused" by Tropea's diagnosis. She noted that she felt unsteady and achy, but she said she did not feel like any part of her body was shaking.

"The muscle fibers in her leg, [Tropea] explained, weren't shaking so much as vibrating," Sanders writes. "When tested, the muscle fibers in people with this disorder flutter at a rate up to 18 beats a second. The fibers don't move far, just very, very fast. And it only happens while standing."

'She refuses to let it slow her down'

While OT often worsens with time, there are treatments that can help improve symptoms—but nothing can cure it or stop its progression. Typically, the condition responds to benzodiazepines, which are frequently prescribed to treat anxiety disorders.

After the woman started taking the medication, slowly increasing it to the most effective dose, she was able to stand again—just not as long as she used to.

"And she could walk; she could even stroll. The ache in her legs never totally went away, but it eased up," Sanders writes.

Since the woman's diagnosis four years ago, the medication has become less effective and her sense of instability more pronounced.

"These days, she has to use a walker," Sanders writes. "It was embarrassing at first, but she refuses to let it slow her down. She is a percussionist in a local concert band. And she hits the pool twice a week. She might need the walker for stability, but she's still strong, and she's hopeful that a new medication Tropea just started her on will help her stay that way." (Sanders, New York Times Magazine, 8/18)