The Kinect™ is a motion-sensing input device that provides full-body 3D motion capture (Fig. 10.3a). This system is used to directly control computer games through body movement. One main strength of this system is that it is affordable and can be easily purchased. This system can be quickly set up anywhere and does not require markers to be placed on the body. Cancela et al. [31] developed a method for tracking gait performance in healthy subjects. They were able to track several features of the gait cycle with minimal error. Galna et al. [17] tested the Kinect system in 15 individuals diagnosed with PD. This group found that Kinect was able to track gross body segment movements very well, but fell short when attempting to track finer movements (such as toe tapping and tremor) [17]. Kinetic can currently be used to track bradykinesia quite well [17].

Currently, the system estimates the position of 20 anatomical landmarks (Fig. 10.3b). This estimation needs to be much more accurate and should have the capability to optimally adjust these landmarks for personalized use. The Kinect system is not portable, once it is set up the individual can only move a certain distance away and to the side of the sensor. However, this system is a viable option for at-home UPDRS assessment of patients. The patient can perform various motor assessment tasks in their own home while in front of the Kinect system.

Optotrak™ is a three-dimensional camera system used to track the motion of infrared emitting diode (IRED) markers (Fig. 10.4a). The IRED markers are placed on body segments of participants and the Optotrak camera tracks the movement of the markers in real time. The camera unit has a limited range within which participants have to stay for proper tracking (Fig. 10.4b). Optotrak has addressed this limitation and allows up to eight camera units to be used, which greatly expands the area of assessment. The Optotrak software provides kinematic data that are clinically relevant to individuals with PD, such as gait measures, tremor detection, and bradykinesia.

A recent study compared the gait measures extracted from the Optotrak system and the Kinect system. The agreement between the body measurements of the two systems was assessed using an intra-class correlation coefficient. It was found that gait parameters obtained from Kinect match well with the Optotrak system [31]. The Optotrak system is expensive, especially when acquiring more than one camera unit. The area of tracking for one camera unit is not sufficient for accurate body assessments and several units would need to be used for proper assessment. Although the Optotrak system has the advantage of being able to track finer movements, technology is quickly advancing and less expensive options may become available.

Wearable inertial sensors are commonly used to measure motion and physical activity associated with daily living [34, 35]. The small size and ease of use make them ideal for placement on various body segments for real-time portable capture of multi-segmental body movements. The gaming and film industry has made use of these sensors in the design and development of their products. The clinical application of these sensors is still in its infancy but this application is quickly garnering attention.

There are three classes of inertial sensors. The combined signals of all three sensors have been used to accurately determine the temporal and spatial measures of body movement. The sensors are:

Wearable inertial sensors have been useful for application in assessing MDs [1, 36–38]. Chang et al. [39] developed a fall detection system by using three sensors (containing an accelerometer and gyroscope) placed on both feet and the waist. This study was able to accurately predict fall risk in various terrains including: motionless, walking, running, walking up an incline and climbing stairs [39].

Several studies have compared the UPDRS with the inertial sensors [40, 41]. Salarian et al. [41] found a high correlation between the total UPDRS and the data collected from three sensors in ten PD participants. This group was interested in monitoring ambulatory activity in a population of individuals with PD. PD often presents as an asymmetric disorder, one side of the body being more severely affected than the other. Sant’Anna et al. [40] assessed asymmetry of both lower and upper limbs during ambulation. The study used four sensors (both legs and wrists) to track asymmetry in 15 PD participants. They found a strong correlation (0.949) between the asymmetry scores of the UPDRS and the asymmetry values from the body sensors [40].

The inertial sensors are able to detect very fine movements, which patients and clinicians’ do not notice. It is often argued that if patients do not notice the small changes in the parkinsonian state then employing these sensors is “overkill.” However, this attribute could be beneficial for early diagnosis of PD by providing data that the clinical scales cannot detect [42]. Furthermore, the ability to detect such fine changes in the parkinsonian state may be beneficial in evaluating the efficacy of new treatments. These claims have to be validated in terms of making a difference in the diagnosis and treatment of patients. As such they remain predominantly in the research domain.

The Kinesia™ system (Cleveland Medical Devices Inc., Cleveland, OH, USA) is marketed as a clinical deployable technology that tracks tremor and bradykinesia in individuals with PD. This device is worn on a single finger, making the device very compact (Fig. 10.5). It has three accelerometers to track linear acceleration and three gyroscopes to measure angular velocity [43]. The device has shown test–retest reliability over clinic-based assessment techniques [44].

Motor symptoms of PD affect the entire body, which is a major concern with the Kinesia device. While it may be useful for detecting tremor and bradykinesia in the hand, it can provide limited detail about the symptom severity in the contralateral lower limb. Furthermore, PD motor symptoms are commonly asymmetric and affect one side more than the other [45, 46]. The motor symptoms may present bilaterally, but the severity of the symptoms may not be symmetrical [45]. The asymmetry of the disease represents another drawback for the Kinesia system.

A full body sensor system is an appealing assessment technique that is gaining interest in the PD research field. Several motion capture suits have been used for research from animation companies such as Xsens™ and Synertial™ (Fig. 10.6a). These systems contain 16–19 inertial sensors that are located all over the body and provide information about all body segments (Fig. 10.6b). Research with the motion capture suit systems have shown reliability and validity at monitoring human movement [37, 47, 48]. These motion capture systems allow assessments to be completed outside of clinic and in the patients’ own home environment.

Motion capture suit systems provide large quantities of data that need to be properly assessed for clinical impact. The main concern of these types of systems is the ability to extract relevant features. As previously mentioned, these sensors can detect small changes in body movements, but extracting these data for clinical application is not yet possible.

In summary, portable and mobile assessment methods:

Currently, physical therapy is the most widely used rehabilitation technique for the management of PD, focusing on improvements in gait, physical capacity (i.e., strength and endurance), posture, and balance [52]. Morris [53] was to our knowledge the first to describe a model of physical therapy management for individuals with PD. He proposed that the ability to move is not lost in PD; rather, it is an activation problem [53]. Morris suggested that the deficit in activation forces individuals with PD to rely on cortical control mechanisms to initiate movement [53]. The model used task-specific strategies such as gait, sitting down, and turning in bed.

The model made use of external cues such as visual, auditory, and proprioceptive stimuli (rocking the body from side to side) [53]. In a healthy human brain, the BG are related to the triggering of internal cues for performing a desired motor function [54, 55]. In PD, such internal cued movements may be significantly affected because of the complex cortical–basal ganglionic dysfunction [54, 56, 57]. It is also possible that these cues are not used to select and modify the required motor response correctly. The results may be seen as a disruption of normal motor function in appendicular and axial systems, including gait. In this context of PD, the external cues used allow alternative brain circuits to be recruited, bypassing the defective BG circuitry [54]. Verschueren et al. [56] studied the influence of extern— cues on motor task performance In a population of PD participants, who were trained to perform a motor task that provided external feedback during the performance of the task. The PD participants were then asked to complete the motor task while blindfolded, eliminating the external feedback. It was found that performance was significantly reduced in PD participants when performing the task blindfolded [56]. It was concluded that providing the external feedback during the performance phase allowed PD participants to partially bypass the BG [54, 56]. A recent review of literature highlighted this fact that external cues access alternative neural pathways that remain intact in the PD brain, such as the cerebello-thalamo-cortical network [58].

The ability to put together a temporal order of task performance is thus very difficult for patients with PD, leading to task failure or “freezing.” Such difficulties can be seen in all aspects of motor performance. To address this, the training model discussed above also used cognitive movement strategies, which break complex movements into separate components [53]. Individuals with PD are trained to perform each component separately and to pay conscious attention to their execution. Morris [59] provided some updates to the physical therapy model focusing on adjusting the rehabilitation strategy based on years of diagnosis. Morris suggests that the tasks used in newly diagnosed individuals should be different from individuals who have been diagnosed for more than 5 years. This is because of the progressive death of substantia nigra cells, despite optimal pharmacological intervention [59].

A recent meta-analysis, conducted by Tomlinson et al. [13], examined the effectiveness of physical therapy in 33 randomized clinical trials with over 1,500 PD participants. Tomlinson et al. [13] found that physiotherapy intervention provides a transient benefit in the treatment of PD, regardless of the physiotherapy intervention. However, in the long term, benefit from physiotherapy remains elusive [13]. This meta-analysis states that an issue with current studies focused on physical therapy for PD is that outcome measures are drastically different [13]. They suggest employing relevant, reliable, and sensitive outcome measures, which hints at both measurement of the physical improvement using reliable tools (such as the systems mentioned above), but also functional improvements in the tasks that actually matter to the patient. Indeed, an improvement in the endurance or strength in a PD population may not matter to the performance of a task such as doing the laundry or crossing the street.

Another issue with current physical therapy models for PD stems from the symptomatic constraints in PD such as rigidity, bradykinesia, freezing, and impaired cognitive processing. Traditional rehabilitation techniques are not suitable for individuals with PD. King and Horak [60] developed an exercise program that was more suited to individuals with PD. However, the program was not adaptable to the various stages of the disease. A rehabilitation program, with functionally relevant tasks, that has direct applicability to the activities of daily living is a necessity. Providing a single space for rehabilitation for every patient is not ideal, as some patients may perform better in the contrived space [29]. Currently, PD patients are enrolled in standardized rehabilitation programs, in a contrived space, to carry out tasks that may not be applicable to their everyday life.

In summary, currently used rehabilitation techniques used for neurological diseases, especially PD:

The development of technologies that counter specific symptoms of PD, although not a cure, help to improve the quality of life of those affected. Tremor is one debilitating motor symptom of PD that affects daily activities. Tremor oscillates at a specific frequency range of 2–15 Hz, which can be measured using inertial sensors [61, 62]. The lower frequencies are indicative of a more severe tremor, whereas higher frequencies relate to mild tremor. The ability to measure the degree of tremor has led to the development of tremor cancellation devices. These devices measure the directionality of the tremor and move in the opposite direction to stabilize it.

Pathak et al. [62] designed a spoon that counteracts tremor in the hand, improving utensil accuracy for individuals with mild to moderate tremor (Fig. 10.7b). The study examined 15 participants diagnosed with essential tremor. The handheld device significantly reduced spoon tremor rated by the UPDRS and accelerometer data [62]. The main strength of this device is the non-invasive nature of the intervention; it is comfortable and easily adopted by its users. However, this device has not proven useful for individuals with severe tremor [62].

The GyroGlove™ is a new technology developed by Faii Ong that reduces tremor continuously (Fig. 10.7a) [63]. The glove is in development with a patent pending, but has the potential to reduce hand tremor in individuals with PD throughout the day. The glove makes use of gyroscopes that resist hand movement and thereby reduce tremors. However, tremor is often multijointed and involves the elbow and shoulder as well.

Freezing of gait (FOG) is a common symptom in individuals with PD that shows little or no response to pharmacological and surgical interventions [65]. FOG has been estimated to affect 32 % of all individuals diagnosed with PD [66]. Several auditory and visual cues have been used to counter FOG episodes in individuals with PD. Several studies have demonstrated that when PD participants walk across parallel lines on the floor there is an improvement in their FOG episodes [67–69].

The U-Step Laser Cane™ is a walking aid that projects a red laser line across the walking path, making use of the parallel line visual cue (Fig. 10.8). Donovan et al. [70] used the Laser Cane in a population of 26 individuals with PD and found a significant improvement in FOG after 1 month of usage. McCandless et al. [71] compared the Laser Cane with several other auditory and visual cueing interventions in a population of 20 individuals with PD. The Laser Cane was found to be the most effective cueing intervention for correcting FOG episodes [71].

In summary, disability-based rehabilitative approaches: