Over 10 million people worldwide live with Parkinson’s disease (PD) which results in motor and nonmotor symptoms. Most commonly people will experience resting tremor, rigidity and bradykinesia. In addition to this, the postural instability and Freezing of Gait (FoG) experienced are risk factors for falls. This results in a decreased quality of life and is associated with multiple other comorbidities (Schrag et al., 2014)(Parkinson’s.org). 38-68% of PD patients will fall each year, of these around 35% will result in a fracture. One study looking at people with PD and falls found that 45% of its participants fell at last once and 80% of these occurred when walking, mostly due to FoG (Latt et al., 2009).
Path Finder is a shoe attachment containing a laser which projects visual cues onto the floor to guide subsequent stepping movement of the adjacent leg. This aims to reduce FoG and falls in PD patients which is thought to be due to FoG disturbing balance. FoG and falls have also shown to react poorly to medications which is why we have been interested in looking at the effect of visual cues with FoG (Bloem et al, 2004).
The effects of visual cues on FoG is well known and has been steadily reproduced in scientific literature (Table 1).
In Parkinson’s disease, sensory cueing such as visual and auditory has been long proven to improve gait (Lebold and Almeida, 2011). Two main mechanisms have been suggested to underlie this phenomenon. It has been demonstrated that in Parkinson’s patients, visual dependence is used to compensate an impaired kinaesthetic feedback. At the same time, attentional processing is also used to alleviate automaticity in walking. It is believed that both sensory and attentional dependence play a role in gait control (Azulay et al., 2006). Projection of a visual cue, through Path Finder, may allow the patient to by-pass deficits in their internal cueing system by augmenting both sensory and attentional abilities.
Although the literature agrees that sensory cues may result in improvements of gait, there was still a debate as to which type of sensory cue (e.g. auditory, visual and tactile rhythmic cues) may provide the optimal results. The level of gait improvement (via examining baseline walking speed and cadence) under the use of (i) metronome (auditory), (ii) laser (visual) and (iii) tactile cues was investigated. Results demonstrated that visual cues produced the highest level of gait improvement across all tested parameters. Conversely, auditory cues (metronome) resulted in the least level of gait improvement overall (Sejdic et al., 2012). This demonstrates a strong rationale for using visual over other available cues.
Having an automated visual cue such as Path Finder has shown to be more beneficial to patients than ‘on demand’ cues in reducing the FoG episodes occurring. Automated cues reduced episodes 43% and ‘on-demand’ only 9% (Velik et al., 2012). Additionally, these cues, when used in conjunction with traditional physiotherapy (treadmill walking exercises), displayed more mobility improvements compared to traditional physiotherapy administered alone (Frazzitta et al., 2009). These results suggest that the use of Path Finder along with normal physiotherapy exercises may be most beneficial compared to conventional methods.
Path Finder also has potential use with Multiple Sclerosis patients (MS). A visual cue was used to examine improvements in gait within MS patients. The experiment demonstrated that stride length improved on average – 14.01% across all tested patients (Baram et al., 2010).
Although Path Finder has only been tested with PD patient thus far, scientific literature suggests a potential benefit for a wider range of users (e.g. elderly, MS, stroke and other movement disorders).
Table 1. A list of studies investigating the use of visual cues against different ‘experimental arms’ (e.g. auditory cues, conventional physiotherapy exercises)
In-house Proof of Concept
The initial physical testing consisted of an experiment to verify the concept of using visual cues to overcome Freezing of Gait (FoG) in Parkinson’s disease. Black strips of tape were placed in a walking pattern and a Parkinson’s sufferer was asked to walk across. These results demonstrated a marked improvement in step length, overall gait stability and regularity, using only observation to evaluate the difference.
In July 2016, another in-house study demonstrated the efficacy of Path Finder in decreasing the number of freezing episodes in a given obstacle course, by two individuals diagnosed with Parkinson’s disease (off medication). Primary results demonstrated that the time taken to complete the course had decreased. Across repeated trials (n=3) per participant, there was an averaged 24.5% and 38.9% marked decrease in time of completion of obstacle course in Participants A and B, respectively. Additionally, the number of freezing episodes while using Path Finder had decreased from an average of 2.1 events to 0.
Path Feel is an insole that provides vibrational feedback to the soles of people at risk of falls, such as those with peripheral neuropathy (nerve damage) e.g. Multiple Sclerosis and diabetic neuropathy. Sensory deficits in these groups mean they are unable to feel the ground properly, making it harder to keep balance and walk. Amplification of sensory parameters under the foot will allow users to better identify foot sensation reducing the sense of imbalance and as a result less falls.
The use of vibrational feedback to improve gait is highly replicable in scientific literature (Table 2).
It’s hypothesized that the mechanism of action underlying the phenomenon includes increased stimulation under the foot, leading to increased amplitude of recorded muscle twitch in three primary areas of the lower leg; (a) Tibialis Anterior, (b) Soleus, and (c) lateral gastrocnemius. Additionally it was demonstrated that vibrational stimuli applied to the tibialis muscle (front of lower leg) causes improvements to balance, even when a person’s eyes are closed in a double leg quiescent standing. This demonstrates that although balance is dependent on visuo-sensory parameters, muscle proprioception is also vital (Han et al., 2013). Vibratory feedback from Path Feel acts to augment muscle stimulation, leading to improved balance. Use of a vibratory insole has already shown in a group of healthy elderly people to improve balance and gait as determined from gait analysis and timed Up and Go (TUG) tests (Lipsitz et al., 2015).
Path Feel has potential use in PD patients. Winfree and colleagues conducted a comparative study investigating the efficacy of vibratory feedback and deep brain stimulation in freezing of gait in Parkinson’s disorder. Vibratory feedback was administered to the bottom of the foot, via an engineered device, the PD Shoe. Results demonstrated that using the PD shoe (i.e. Vibrational feedback) for an extended period of two weeks, led to improvements in patients walking, more so than traditional DBS (Winfree et al., 2013). Path Feel also utilizes a vibrational feedback system, which can be used by PD patients to improve gait in those subjects.
In addition to PD vibrational feedback to the bottom of the foot can also improve quiet standing balance control (balance whilst stood still) and improve vibrotactile sensitivity in diabetic neuropathic and stroke patients (Liu et al., 2002). Priplata and colleagues (2005) demonstrated that when a frequency of 100 Hz was applied to the foot, sway parameters greatly improved in these patients. In a follow-up study, Hijmans and colleagues (2008) demonstrated that the best vibrating frequency in neuropathic patients is 128 Hz. Furthermore, the performance of increasingly attention-demanding tasks readily decreased balance. Results demonstrated that vibrating insoles improved balance in neuropathic patients only when attention was distracted (i.e. when they were performing a calculation task). This is advantageous as it demonstrates that the vibrational feedback (in Path Feel) only positively influences balance when patients are at their most vulnerable balance states.
Table 2. A list of studies investigating the use of vibrational (Haptic) feedback to improve balance parameters. These studies apply vibration to different parts of the body, namely (i) foot, (ii) localized vibrations and (iii) whole body vibrations.
In-house Proof of Concept
An in-house study investigated the efficacy of Path Feel as a device that can improve functional walking ability and gait through the administration of haptic feedback. Walking ability (experimental outcome) was evaluated by the Activity-specific Balance Confidence (ABC) questionnaire, the Berg Balance Scale (BBS) test, and the Timed Up and Go (TUG) test. The results demonstrated a significant improvement of BBS scores. This demonstrates that Path Feel acts to improve balance in an elderly cohort. Additionally, Path Feel yielded positive improvements in short-term use. Current research is 1) investigating the effects on balance by long-term use of Path Feel and 2) investigating the effects on balance in other population groups.