ARTICLE IN BRIEF
A prototype for laser shoes, which project transverse lines on the floor as visual cues, significantly reduced freezing of gait in a pilot study of 21 patients with Parkinson's disease.
In an early proof of concept trial, researchers have tested a prototype for “laser shoes” that aim to facilitate stepping for Parkinson's disease patients who experience freezing of gait (FOG).
The laser shoes, which project transverse lines on the floor as visual cues, significantly reduced FOG in a pilot study of 21 patients with Parkinson's disease (PD), according to a paper in the December 20, 2017 online edition of Neurology.
The idea for the laser shoes grew out of frustration with the modest effects of deep brain stimulation, the senior author of the new paper, Murielle Ferraye, PhD, told Neurology Today.
“I was testing patients' freezing before and after these invasive brain procedures, and I was so disappointed, because it didn't help them that much,” said Dr. Ferraye, a postdoctoral researcher now at the Donders Institute for Brain, Cognition and Behavior in the department of neurology at Radboud University Medical Centre in Nijmegen, The Netherlands.
Like the lasers already available on a cane or a walker, the laser shoes are designed to exploit the intact brain circuits as a compensatory means to overcome FOG. Unlike those pre-existing devices, however, the laser shoes are automatically triggered by a patient's step, so that the weight of one foot stepping on the ground triggers a line to be projected to the contralateral foot.
After having five minutes to familiarize themselves with the shoes, patients were tested both off and on medication in a gait laboratory, following a standard walking protocol.
Compared to when the laser shoes were not in use, the number of FOG episodes was reduced by 45.9 percent when patients used the shoes while off medication, and by 37.7 percent when on medication. The percent of time frozen fell by 56 percent when off medication (95% CI [32.5 – 85.8]; p=0.004), and by 32.3 percent when on medication (95% CI [-41.8 – 91.5]; p=0.075).
Dr. Ferraye noted that the exact distance at which the line is projected by the laser shoes is adjustable according to patient preference. “Some patients prefer to step toward the line,” she said, “and some prefer to step over it.”
Dr. Ferraye said it would be ideal if the device would project lines only when the patient is on the verge of freezing.
“On-demand cueing would consist of having the device detect freezing before it occurs and only then project the laser line,” she said. “There is a sort of trembling of the leg that occurs, reflecting the efforts of the patient to try to break the freezing. We are to some extent able to detect this freezing, but so far applying the method in freely moving patients in their home has not proved reliable enough. Freezing is indeed a very complex phenomenon that varies a lot within and across patients.”
A follow-up study of the laser shoes used in patients' homes has already been completed and submitted for publication, Dr. Ferraye said, and longer trials involving larger numbers of patients are being planned. [For more about the study design and findings, read “Laser Shoes: The Study Design.”]
The study was funded by grants from Hersenstichting (to Dr. Ferraye) and the European Community's Seventh Framework Programme, but the authors reported no other relevant disclosures.
While using cues is not a new concept, the application of it in a close-loop system on a shoe is “quite witty,” said Alberto Espay, MD, FAAN, professor of neurology and the James J. and Joan A. Gardner Family Center Research Chair for Parkinson's Disease and Movement Disorders, who was not involved with the research.
“The simplest ideas are sometimes the ones that are most useful,” Dr. Espay said. “It's harnessing something everyone has: shoes. I'm quite impressed by the resourcefulness of the investigator who came up with this idea.”
Dr. Espay previously studied the use of goggles to project virtual-reality tiles on the floor, the benefits of which carried over for many days after the patient had used them. “The shoe is infinitely simpler compared to the goggle,” he said. “I wonder if patients could use it one or two days a week and see benefits for the rest of the week.”
Fay B. Horak, PhD, PT, professor of neurology at the Oregon Health Sciences University School of Medicine's Balance Disorders Laboratory, coauthored a 2016 paper in which a vibration was applied to the feet as tactile cue.
“My experience is that patients often habituate to a cue,” Dr. Horak said. “They benefit at first, but then if they use it over and over, even within an hour or two, they need to switch to another kind of cue. I have patients who are clever and use lots of different types of cues. They might turn on a march cadence if their laser cane stops working.”
While it's logical to think that the laser shoes might prove to be as effective as the laser cane, without the need to carry a cane around, “It's way too early to know if this is going to really help people at home,” Dr. Horak said. “What works in a lab doesn't necessarily work in real life.”
Even if the laser shoes are proved to work effectively in future trials, some patients will still never use them, due simply to cosmetic reasons, said Liana Rosenthal, MD, assistant professor of neurology and director of the Clinical Core of the Morris K. Udall Parkinson's Disease Research Center of Excellence at Johns Hopkins University School of Medicine.
“It's a fantastic idea,” Dr. Rosenthal said. “Further study is warranted. But there's going to be a subset of patients, no matter how bad their walking is, who will never use these shoes. They don't look cool, and for patients who already feel self-conscious about their disease, laser shoes won't help.”
A potential obstacle to widespread adoption of the laser shoes for most patients is the price currently quoted by the U.K. company, PathFinder, offering a version of them for sale, said Irene Litvan, MD, FAAN, the Tasch Endowed Professor of Neurology at the University of California, San Diego School of Medicine. The company's website quotes a price of £395 ($528 US).
“They're extremely expensive,” Dr. Litvan said. “It could be a reasonable solution if it would have a reasonable price.”
Even so, she added, “This solution of having a laser light in the shoes sounds very good. With the cane and the walker, the patient has to carry something around. The cleverness of the investigators in putting it in a shoe, something you wear anyway, is wonderful.”
The independent experts had no disclosures related to the laser shoe.
LASER SHOES: THE STUDY DESIGN
The laser shoe study involved two lab assessments, off and on medication, in randomized order on two separate mornings. The gait protocol consisted of five trials, including walking back and forth, undisturbed, over 10 meters, and more complex trials involving, for instance, turning on command while walking, including 180-degree and 360-degree right and left turns. Patients wore the laser shoes continuously, but a switch allowed the researchers to turn the visual cueing off or on. Their performance was videotaped and rated offline by independent raters blinded to the on or off medication status but not to the laser shoes.
The positive results seen on these objective measures were paralleled by patients' positive subjective experiences.
The researchers have tested the use of auditory cues (the sound of a marching tune, for instance), tactile cues (vibrations delivered to the hands or feet) or, more often, visual cues. But existing visual cue systems have shortcomings. The laser cane must be manually controlled, by pushing a button every time the patient wants to see a line projected, thereby increasing cognitive demands to the point where some patients cannot operate them, Dr. Ferraye said. The laser shoes, by contrast, incorporate a closed-loop system, in which the patients' natural movements automatically result in a line being projected just at the moment when the patient needs to see it.
“The laser line appears orthogonally in front of the contralateral foot that is about to enter the swing phase,” the study authors explained. “When the body weight is removed from the heel, the laser is deactivated. This cycle repeats itself step after step, delivering the cues alternately to each foot. This way, the cues are tuned exactly to the patient's motion.”