Use of smartphones and portable media devices for quantifying human movement characteristics of gait, tendon reflex response, and Parkinson's disease hand tremor

Smartphones and portable media devices are both equipped with sensor components, such as accelerometers. A software application enables these devices to function as a robust wireless accelerometer platform. The recorded accelerometer waveform can be transmitted wireless as an e-mail attachment through connectivity to the Internet. The implication of such devices as a wireless accelerometer platform is the experimental and post-processing locations can be placed anywhere in the world. Gait was quantified by mounting a smartphone or portable media device proximal to the lateral malleolus of the ankle joint. Attributes of the gait cycle were quantified with a considerable accuracy and reliability. The patellar tendon reflex response was quantified by using the device in tandem with a potential energy impact pendulum to evoke the patellar tendon reflex. The acceleration waveform maximum acceleration feature of the reflex response displayed considerable accuracy and reliability. By mounting the smartphone or portable media device to the dorsum of the hand through a glove, Parkinson's disease hand tremor was quantified and contrasted with significance to a non-Parkinson's disease steady hand control. With the methods advocated in this chapter, any aspect of human movement may be quantified through smartphones or portable media devices and post-processed anywhere in the world. These wearable devices are anticipated to substantially impact the biomedical and healthcare industry.

Motion analysis of normal patellar tendon reflex

BACKGROUND

Reflex assessment, an essential element in the investigation of the motor system, is currently assessed through qualitative description, which lacks of normal values in the healthy population. This study quantified the amplitude and latency of patellar tendon reflex in normal subjects using motion analysis to determine the factors affecting the reflex amplitude.

METHODS

100 healthy volunteers were recruited for patellar tendon reflex assessments which were recorded using a motion analysis system. Different levels of input strength were exerted during the experiments.

RESULTS

A linear relationship was found between reflex input and reflex amplitude (r = 0.50, P <0.001). The left knee was found to exhibit 26.3% higher reflex amplitude than the right (P <0.001). The Jendrassik manoeuvre significantly increased reflex amplitude by 34.3% (P = 0.001); the effect was especially prominent in subjects with weak reflex response. Reflex latency normality data were established, which showed a gradual reduction with increasing input strength.

CONCLUSION

The quantitative normality data and findings showed that the present method has great potential to objectively quantify deep tendon reflexes.

Analyse du mouvement du réflexe rotulien normal.

Influence of age on patellar tendon reflex response

Background

A clinical parameter commonly used to assess the neurological status of an individual is the tendon reflex response. However, the clinical method of evaluation often leads to subjective conclusions that may differ between examiners. Moreover, attempts to quantify the reflex response, especially in older age groups, have produced inconsistent results. This study aims to examine the influence of age on the magnitude of the patellar tendon reflex response.

Methodology/Principal Findings

This study was conducted using the motion analysis technique with the reflex responses measured in terms of knee angles. Forty healthy subjects were selected and categorized into three different age groups. Patellar reflexes were elicited from both the left and right patellar tendons of each subject at three different tapping angles and using the Jendrassik maneuver. The findings suggested that age has a significant effect on the magnitude of the reflex response. An angle of 45° may be the ideal tapping angle at which the reflex can be elicited to detect age-related differences in reflex response. The reflex responses were also not influenced by gender and were observed to be fairly symmetrical.

Conclusions/Significance

Neurologically normal individuals will experience an age-dependent decline in patellar reflex response.

The validity and reliability of motion analysis in patellar tendon reflex assessment

BACKGROUND

The deep tendon reflex assessments that are essential to the accurate diagnosis of neurological or neuromuscular disorders are conducted subjectively in clinical neurology. Our aim was to assess deep tendon reflexes objectively with a new reflex quantification method.

METHODOLOGY/PRINCIPAL FINDINGS

The present study used a motion analysis technique to collect quantitative measurements for both the input and output of normal patellar tendon reflex. Reflex responses were measured as knee angles. The patellar tendon reflexes of 100 healthy subjects were examined using 6 levels of tendon taps, where all the assessments were captured using motion capture system. A linear relationship was found between the experimental maximum tapping velocity and tapping angle (coefficient of determination = 0.989), which was consistent with the theoretical values. Tapping velocities were predictable according to tapping angles. The findings proved the reproducibility of tapping method in producing consistent input. The reflex amplitude was consistent between two randomly assigned groups, and linearly proportionate to the tapping velocity.

CONCLUSIONS/SIGNIFICANCE

The findings on reflex amplitude indicate that motion analysis is a valid and reliable method of assessing and measuring deep tendon reflexes.

WIRELESS THREE DIMENSIONAL ACCELEROMETER REFLEX QUANTIFICATION DEVICE WITH ARTIFICIAL REFLEX SYSTEM

Fundamental to the neurological examination is the deep tendon reflex. Two important tendon reflex parameters are response and latency. Response can be quantified by the NINDS Myotatic Reflex Scale; however, controversy exists with respect to the accuracy of the scale. Electrodiagnostic testing may derive parameters, similar to the validity of the reflex latency; however, such tests require highly specialized resources. Attempts have been made to develop quantified reflex devices. Two wireless three-dimensional (3D) accelerometers incorporating MEMS technology have been integrated into a device for quantifying reflex response and latency. The device is tested and evaluated using an artificial reflex system. The reflex quantification device obtained reflex response and latency parameters based on the artificial reflex device, which were bounded by a 98% confidence level with a 2% margin of error about the mean.

HUMAN REFLEXIVE RESPONSE AND ITS OBJECTIVE FUNCTION REGARDING BALANCE RECOVERY FROM PERTURBATION DURING WALKING

Balance recovery from perturbation plays a crucial role in preventing people from falling during walking. Understanding the underlying mechanism of balance recovery during walking could not only bring new insights into the motor control field, but also benefit the development of walking assist systems for daily living environment, where perturbations to walking are frequently caused by slips, uneven terrain, slopes, obstacles, etc.

It is evident that humans can cope with such perturbations, especially when the perturbations cannot be predicted or perceived in advance, by means of reflexes, which cause relatively fixed, unconscious muscular response patterns to perturbations within a short period of time ranging from several tens of ms to 200 ms. However, except for several hypotheses about the underlying neural mechanisms of the reflexes during walking, there is no widely accepted unified theory.

In our previous study, a muscular-reflexive pattern was defined using muscle activity recorded during reflexive responses to slip perturbation. This is one important step toward the understanding of the underlying mechanism, since the pattern could serve as the quantitative target in pursuit of the underlying mechanism. We can speculate that this pattern is the optimal balance recovery behavior to human muscular-skeletal system, as a result of long evolution; however, before we use this target to guide our pursuit, we should first prove its optimality, while making clear the objective functions for balance recovery and the effect of morphological factors.

Our approach includes (1) defining objective functions for balance recovery from a slip perturbation during walking; (2) using a bio-mimetic human walking simulator to perform evaluation according to the objective functions; (3) employing a genetic algorithm (GA) to search the optimal solutions, for different objective functions.

Results showed that the muscular-reflexive pattern is optimal to the balance recovery from slip perturbation during walking, in terms of a hybrid evaluation measure (HEM), which takes both static and dynamic aspects of balance recovery into consideration.

TENDON REFLEX AND STRATEGIES FOR QUANTIFICATION, WITH NOVEL METHODS INCORPORATING WIRELESS ACCELEROMETER REFLEX QUANTIFICATION DEVICES, A PERSPECTIVE REVIEW

The deep tendon reflex is a fundamental aspect of a neurological examination. The two major parameters of the tendon reflex are response and latency, which are presently evaluated qualitatively during a neurological examination. The reflex loop is capable of providing insight into the status and therapy response of both upper and lower motor neuron syndromes. Attempts have been made to ascertain reflex response and latency; however, these systems are relatively complex, resource intensive, with issues of consistent and reliable accuracy. The solution presented is a wireless quantified reflex device using tandem three-dimensional (3D) wireless accelerometers to obtain response based on acceleration waveform amplitude and latency derived from temporal acceleration waveform disparity. Three specific aims have been established for the proposed wireless quantified reflex device:

(1) Demonstrate the wireless quantified reflex device is reliably capable of ascertaining quantified reflex response and latency using a quantified input.

(2) Evaluate the precision of the device using an artificial reflex system.

(3) Conduct a longitudinal study respective of subjects with healthy patellar tendon reflexes, using the wireless quantified reflex evaluation device to obtain quantified reflex response and latency.

Aim 1 has led to a steady evolution of the wireless quantified reflex device from a singular 2D wireless accelerometer capable of measuring reflex response to a tandem 3D wireless accelerometer capable of reliably measuring reflex response and latency. The hypothesis for aim 1 is that a reflex quantification device can be established for reliably measuring reflex response and latency for the patellar tendon reflex, comprised of an integrated system of wireless 3D MEMS accelerometers. Aim 2 further emphasized the reliability of the wireless quantified reflex device by evaluating an artificial reflex system. The hypothesis for aim 2 is that the wireless quantified reflex device can obtain reliable reflex parameters (response and latency) from an artificial reflex device. Aim 3 synthesizes the findings relevant to aim 1 and 2, while applying the wireless accelerometer reflex quantification device to a longitudinal study of healthy patellar tendon reflexes. The hypothesis for aim 3 is that during a longitudinal evaluation of the deep tendon reflex the parameters for reflex response and latency can be measured with a considerable degree of accuracy, reliability, and reproducibility. Enclosed is a detailed description of a wireless quantified reflex device with research findings and potential utility of the system, inclusive of a comprehensive description of tendon reflexes, prior reflex quantification systems, and correlated applications.

ACCELEROMETERS FOR QUANTIFICATION OF GAIT AND MOVEMENT DISORDERS: A PERSPECTIVE REVIEW

Accelerometers have become increasingly integrated in the biomedical field, as they are highly portable and capable of objectively and reliably quantifying motion. Two specific applications for accelerometers are the quantification of gait and movement disorders, such as Parkinson's disease and essential tremor. The evolution of accelerometers to their present status is discussed. Accelerometry is contrasted with more traditional means for accessing gait and movement disorders. Advances in the research validation of accelerometers for the characterization of gait and movement disorders, such as essential tremor and Parkinson's disease, are addressed. The review concludes with the advancement of three-dimensional (3D) wireless accelerometers and pertinent future implications.

QUANTIFIED DEEP TENDON REFLEX DEVICE FOR RESPONSE AND LATENCY, THIRD GENERATION

Deep tendon reflex is fundamental for a neurological examination. A hyperactive reflex response is correlated with spasticity, which can also be associated with the degree of damage to the supraspinal input, essentially assessing the severity of traumatic brain injury. Clinical evaluation of the myotatic stretch reflex is provided by the National Institute of Neurological Disorders and Stroke (NINDS) Myotatic Reflex Scale (0 to 4); however, the results of the NINDS Myotatic Reflex Scale vary in terms of interpretation and lack temporal data. Deep tendon reflex can assess the severity and degree of peripheral neuropathy. Subsequent to the neurological examination, suspect patients are often referred to a specialist for definitive electrodiagnostic testing. A study by Cocito found that 28% of the prescriptions for testing were considered to be inappropriate. Therefore, the solution is a fully quantified tendon reflex evaluation system. The input force of the reflex hammer is derived from a predetermined potential energy setting. Tandem wireless three-dimensional (3D) microelectromechanical systems (MEMS) accelerometers quantify the output and latency time of the reflex. The wireless 3D MEMS accelerometers are positioned to a standard anchor point near the ankle and reflex hammer swing arm. Reflex response is quantified by the maximum and minimum components of the acceleration profile. The temporal disparity between hammer strike and response defines the latency of the reflex loop. The quantified data collected from wireless 3D MEMS accelerometers are conveyed to a portable computer. Enclosed are the initial test and evaluation and the description of such a device, which quantitatively evaluates the reflex response and latency using wireless 3D MEMS accelerometers, while demonstrating precision for reproducibility.

WIRELESS ACCELEROMETER ASSESSMENT OF GAIT FOR QUANTIFIED DISPARITY OF HEMIPARETIC LOCOMOTION

Assessment of locomotion quality subsequent to neurological trauma, such as stroke or traumatic brain injury is imperative for the correct allocation of therapy dosage and strategy. In light of the limited amount of medical professionals in contrast with the rising number of people with neurological disorders; a new paradigm for addressing therapeutic strategies for neurological trauma is advocated. An important aspect for therapy of neuro-motor disorders is the characterization of gait. There are devices presently used for evaluating gait, such as EMG, optical sensors, electrogoniometers, metabolic energy expenditure devices, foot stride analyzers, and ground reaction force sensors. These devices have inherent issues, such as spatial constraints, line of sight requirements, and specialization requirements. A solution for improved autonomy of gait assessment is demonstrated by the use of fully wireless 3D MEMS accelerometers, which are light weight and minimally intrusive. To minimize specialization issues, the accelerometers may be positioned at a standard anatomical anchor. The role of traumatic brain injury with respect to gait dysfunction is addressed. Enclosed is the initial test and evaluation of a wireless 3D MEMS accelerometer for gait analysis. The gait analysis is conducted in outdoor conditions, while walking on a sidewalk.

FOURTH GENERATION WIRELESS REFLEX QUANTIFICATION SYSTEM FOR ACQUIRING TENDON REFLEX RESPONSE AND LATENCY

An intrinsic aspect of the standard neurological examination is the deep tendon reflex. A clinician is tasked with qualitatively evaluating reflex parameters, such as reflex response and latency. The tendon reflex is capable of providing preliminary insight with respect to dysfunction of the central and peripheral nervous systems. The qualitative assessment of the tendon reflex can be classified through the implementation of an ordinal scale, such as the NINDS scale which spans five ordinal components from 0 to 4. The reliability and accuracy of the ordinal-scale method for classifying reflex characteristics have been demonstrated to be an issue of controversy. Ordinal scales lack the capacity to properly classify the temporal features of the tendon reflex. Electrodiagnostic testing traditionally provides higher fidelity evaluation of peripheral neuropathy; however, a study by Cocito et al., has discovered 28% of the prescriptions were inappropriate. The fourth-generation wireless reflex quantification system provides a less resource intensive, highly accurate, reliable, and reproducible alternative. The patellar tendon reflex is evoked through a predetermined potential energy derived swing arm attached to a standard reflex hammer. Tandem wireless 3D MEMS accelerometers quantify reflex response and latency. The reflex response maximum and minimum are acquired from the wireless 3D MEMS accelerometer positioned above the ankle joint. The latencies derived from the maximum and minimum of the reflex responses are derived from the temporal disparity relative to the acceleration waveforms of the reflex response and swing arm evoking the tendon reflex. The fourth-generation wireless reflex quantification system has been evolved with a more user-convenient wirelessly activated datalogger mode, which is subsequently downloaded to a local PC wirelessly. The wireless datalogger mode enables sampling at a greater rate relative to the real-time streaming data mode. An automated MATLAB software program is implemented for acquiring reflex parameters. Enclosed is the longitudinal study of the fourth-generation wireless reflex quantification system that demonstrates considerable precision for accuracy, reliability, and reproducibility. As a supplement to the research, a brief reflex modulation study is amended to the longitudinal study.