Case study of context-triggered acoustic cueing to assist walking of Parkinson’s disease patients

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Introduction

Parkinson’s disease (PD) is a common neurological disorder caused by a progressive loss of dopaminergic and other sub-cortical neurons. PD includes impaired motor skills as part of its symptoms. About 50% of patients in the advanced stages of the PD are affected by the freezing of gait (FOG) symptom. FOG is a sudden and transient inability to walk. FOG is associated with substantial social and clinical consequences for patients. It often causes falls, interferes with daily activities and significantly impairs quality of life. Patients, who experience FOG, report that during the freezing episode their feet are inexplicably glued to the ground.

Because gait deficits in PD patients are often resistant to pharmacologic treatment, effective non-pharmacologic treatments are of special interest.

Objectives

Goal of this study is to evaluate the concept of a wearable device that can obtain real-time data, processes them and provide alerts based on pre-determined specifications.

Previous work has shown that gait performance in PD can be improved by applying continuous external rhythmic auditory, visual or somatosensory cues. The main limitations of the previous external cueing approaches are the continuous nature of the cueing intervention, manually triggered cueing or cueing provided only during training session. In order to overcome these limitations, our objective is to develop and evaluate a system, that provides cueing automatically only in the context of impaired performance, i.e., only when most needed. In our study we focused on the actual FOG episodes and the perception of the patients and physiotherapists.

In detail the objectives of this study are:

• The development of a personal wearable system together with algorithms to detect FOG online and provide automatically acoustic cueing.
• The evaluation of our system in a study with PD patients.
• Evaluation of the systems performance of real-time freezing recognition in terms of accuracy, latency, etc.
• Evaluation of the PD patients’ and physiotherapists’ perceptions on the wearable, context aware technology.

Methods

We developed a real time wearable FOG detection system that automatically provides a cueing sound when FOG is detected and which stays until the subject resumes walking. We evaluated our wearable assistive technology in a study with 10 PD patients.

Results

Eight out of the ten patients exhibited FOG during the study; two patients did not have any FOG event. The walking distance and number of turns depended on the patients’ gait speed. Overall, 8 h 20 min of data have been recorded and 237 FOG events have been identified from the video recordings by the physiotherapists. The length of the FOG events ranged from 0.5 sec to 40.5 sec.

No technical malfunctions occurred during the study. 96.2% of the identified FOG episodes (n=237) were detected online by the wearable device. The user-independent frame based sensitivity and specificity of the online detected FOG using the ankle sensor were 73.1% and 81.6%, respectively.

The self-assessment indicates that the patients benefit from the system. Also the physiotherapists rated the influence of the automatic identification of the FOG events and the auditory feedback as beneficial, at least for those with severe freeze. Observations by the physiotherapists have shown that the patients used the cueing mainly in long turning freeze which are longer than 3 sec, and in tight quarters after they were stuck. The rhythmic sound helped them to take small steps to come out of the freezing. One physiotherapist differentiated between patients that are usually stable during the freeze and patients that seem more at risk of falling in case of FOG. Patients that usually are stable during the freeze will use the cues more while freezing to get out again. In comparison to patients with lesser stable gait, who will try to use the cues to prevent falling. In the latter case, the cueing should already assist these people while they are walking, as Rhythmic Auditory Stimulation (RAS), so that they can use the rhythm to improve their walking abilities. In this context we have to consider that one single system to address all the diversity of FOG is clearly not realistic - goal of this work is to show that it may help segments of that population.

Conclusion

To our knowledge our study is the first where FOG has been automatically detected online by a wearable system and acoustic cueing was provided automatically at the onset of the freeze. The system detected the FOG events with a sensitivity of 73.1% and a specificity of 81.6%.

The evaluations of the responses obtained from the patients were also positive. Some patients expressed their motivation to wear it even for several weeks. Also the answers regarding the influence and the effect of the automatic cueing were promising. At least half of the patients have seen a positive effect.

With this study we show that online assistive feedback for PD patients is possible. Our results demonstrate the benefit of such a context aware systems and motivate for further studies.

Further investigations are necessary to analyze and prove the real-world performance. Remaining open questions are: (i) How useful will the patient’s judge the system when using it for several days? (ii) During constant use, can the patients learn to rely on the system the way they rely on other walking aids? (iii) Can they even get used to it so much, that the cueing sound is not disturbing?

Acknowledgment

Publications

2010

• A Wearable System to Assist Walking of Parkinson's Disease Patients
  Marc Bächlin, Meir Plotnik, Daniel Roggen, Nir Giladi, Jeffrey M Hausdorff and Gerhard Tröster
  (2010), in: Methods of Information in Medicine, 49:1(88-95)
  [ BiBTeX RIS DOI URL ]
• Wearable assistant for Parkinson's disease patients with the freezing of gait symptom
  Marc Bächlin, Meir Plotnik, Daniel Roggen, Inbal Maidan, Jeffrey M Hausdorff, Nir Giladi and Gerhard Tröster
  (2010), in: IEEE Transactions on Information Technology in Biomedicine, 14:2(436 - 446)
  [ BiBTeX RIS DOI URL ]

2009

• A wearable system towards pervasive healthcare: Case study on Parkinson’s disease patients
  Marc Bächlin
  Talk at the International Workshop on Physiological Networks: Theory, Implementation and Application, 2009
  [ BiBTeX RIS ]
• Automated treatment of freezing of gait in Parkinson's disease using a wearable device that automatically detects freezing
  Meir Plotnik, Marc Bächlin, Daniel Roggen, Noit Inbar, Inbal Maidan, Talia Herman, Marina Brozgol, Eliya Shaviv, Gerhard Tröster and Jeffrey M Hausdorff
  in: Annual meeting of the Israeli Neurological Society, Israel, pages 63, 2009
  [ BiBTeX RIS ]
• Online Detection of Freezing of Gait in Parkinson's Disease Patients: A Performance Characterization
  Marc Bächlin, Daniel Roggen, Meir Plotnik, Jeffrey M Hausdorff, Nir Giladi and Gerhard Tröster
  in: Proceedings of the 4th International Conference on Body Area Networks, 2009
  [ BiBTeX RIS ]
• Parkinson patients' perspective on context aware wearable technology for auditive assistance
  Marc Bächlin, Meir Plotnik, Daniel Roggen, Noit Inbar, Nir Giladi, Jeffrey M Hausdorff and Gerhard Tröster
  in: Proceedings of the 3rd International Conference on Pervasive Computing Technologies for Healthcare, 2009
  [ BiBTeX RIS URL ]
• Potentials of enhanced context awareness in wearable assistants for Parkinson’s disease patients with freezing of gait syndrome
  Marc Bächlin, Daniel Roggen, Meir Plotnik, Noit Inbar, Inbal Maidan, Talia Herman, Marina Brozgol, Eliya Shaviv, Nir Giladi, Jeffrey M Hausdorff and Gerhard Tröster
  in: Proceedings of the 13th International Symposium on Wearable Computers (ISWC), pages 123-130, 2009
  [ BiBTeX RIS URL ]