November 18, 2013

Will New Ankle Sensors Help Parkinsonians with Freezing of Gait?

Several posts on my Twitter feed recently mentioned a brief article on Scientific American's site with this title: “Could a Simple Ankle Sensor Help with Parkinson’s Symptoms?”

The particular symptom under consideration is “freezing of gait” (FOG), something that apparently affects – eventually -- about 60% of us with Parkinson’s. It’s not an issue (yet) for me, though several PWPs I know experience FOG regularly. When it happens, their feet suddenly seemed riveted to the floor, and forward motion comes to a halt.

FOG is more than a frustrating inconvenience; it can also lead to falls and injury.

The device is under development at the University of Alabama/ Huntsville and works this way: motion sensors are embedded in a shoe or attached at the ankle. When those sensors detect FOG, they send auditory cues to the PWP’s earpiece, perhaps a simple message like “walk.” The process seems awfully simple, but initial testing has apparently shown positive results.

Here's an image that was included in the researchers' patent application for their device. The nice lady is wearing the sensor on her shoe, listening to cues in her earpiece, moving forward, and smiling:


The article on the Scientific American site suggests the device will be available on the market in several years. But the concept isn’t new. A quick review of FOG study “abstracts” on NIH’s PubMed site reveals these details in the evolution of our understanding of the symptom and its potential treatment:

2006: “Freezing of gait in Parkinson's disease.”
From the Department of Neurology, Juntendo University Shizuoka Hospital, Shizuoka, Japan, this abstract clearly identifies various therapeutic approaches to FOG:
Freezing of Gait (FOG) is one of the most disabling and least understood symptoms in Parkinson's disease (PD), and is usually observed in the advanced stage of the disease. FOG can be experienced on turning, in narrow spaces, whilst reaching a destination, and in stressful situations. FOG is commonly observed in the "off" state, but it can also be observed in the "on" state. Dual tasking (cognitive load) aggravates FOG. Visual or auditory cues often resolve FOG. Analysis of gait revealed that the rhythm of stepping suddenly jumps into high frequency (4-5 Hz) in FOG (hastening), and that floor reaction forces are disregulated. Stride-to-stride variability is increased in FOG. . . . Treatment of FOG includes behavioural, medical, and surgical approaches. Tricks of all kinds (including external cues) are effective therapeutic approaches. If FOG occurs predominantly in the "off" state, dopaminergic therapy can be increased. For "on" freezing or if "on" response is otherwise optimised, the dose of the dopaminergic agent may be manipulated, but it could lead to the deterioration of parkinsonism. Deep brain stimulation of the STN often alleviates FOG in the "off" state.
2008: “Cueing for freezing of gait in patients with Parkinson's disease: a rehabilitation perspective.”
From the Department of Rehabilitation Sciences, Katholieke Universiteit, Leuven, Belgium, this abstract casts doubt on the usefulness of "cueing," and identifies flaws in studies to date:
Freezing of gait (FOG) has been known to respond favorably to sensory tricks and cues. However, FOG is a complex phenomenon with various motor control deficits at play. In this review, we examined and summarized the currently available evidence for the effectiveness of cueing for FOG to determine its value as a clinical method. The results showed that the immediate effects of cues have no consistent impact but longer periods of cued training may be beneficial. The review also showed (1) the limited statistical power and methodological weakness of the studies involved; (2) measurement difficulties of FOG, and (3) the need to better understand its underlying causal factors. Overall, the findings suggest a smaller capacity for compensation in patients suffering from FOG. Especially when attention is overloaded, the therapeutic window and the practical applicability of cueing seem more limited. These aspects need to be incorporated in the development of future cueing programs designed to alleviate FOG.
2009: "deFOG--A real time system for detection and unfreezing of gait of Parkinson's patients."
In this abstract, Emil Jovanov -- professor of computer and electrical engineering at the University of Alabama in Huntsville, Huntsville, Alabama and lead researcher on the new sensor device described at top of this post -- outlines the concept that he and his team are developing. Presumably, they've been refining the technology described here for almost five years. 
Freezing of gait (FOG) is a common complication in movement disorders, typically associated with the advanced stages of Parkinson's disease. Auditory cues might be used to facilitate unfreezing of gait and prevent fall related injuries. We present a wearable, unobtrusive system for real-time gait monitoring, which consists of an inertial wearable sensor and wireless headset for the delivery of acoustic cues. The system recognizes FOG episodes with minimum latency and delivers acoustic cues to unfreeze the gait. We present design of a system for the detection and unfreezing of gait (deFOG), and preliminary results with average latency of 332 milliseconds (.332 of a second), and maximum latency of 580 ms (.58 of a second).
2010: "A simple method to assess freezing of gait in Parkinson's disease patients."
From University of Belgrade, Serbia, this abstract describes a method for assessing FOG, not correcting it. Still, it’s part of the literature documenting scientific advances in this area of interest to PWPs. The more clearly and quickly scientists can detect FOG, the better treatments will be.
Freezing of gait (FOG) can be assessed by clinical and instrumental methods. Clinical examination has the advantage of being available to most clinicians; however, it requires experience and may not reveal FOG even for cases confirmed by the medical history. Instrumental methods have an advantage in that they may be used for ambulatory monitoring. The aim of the present study was to describe and evaluate a new instrumental method based on a force sensitive resistor and Pearson's correlation coefficient (Pcc) for the assessment of FOG. Nine patients with Parkinson's disease in the "on" state walked through a corridor, passed through a doorway and made a U-turn. We analyzed 24 FOG episodes by computing the Pcc between one "regular/normal" step and the rest of the steps . . . . The method was sensitive to various types of freezing; although no differences due to different types of freezing were detected. The study showed that Pcc analysis permitted the computerized detection of FOG in a simple manner analogous to human visual judgment, and its automation may be useful in clinical practice to provide a record of the history of FOG.

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