One of the hottest topics in rehabilitation robotics is that of proper control of prosthetic devices. Despite decades of research, the state of the art is dramatically behind the expectations. To shed light on this issue, in June, 2013 the first international workshop on Present and future of non-invasive peripheral nervous system (PNS)-Machine Interfaces (MI; PMI) was convened, hosted by the International Conference on Rehabilitation Robotics. The keyword PMI has been selected to denote human-machine interfaces targeted at the limb-deficient, mainly upper-limb amputees, dealing with signals gathered from the PNS in a non-invasive way, that is, from the surface of the residuum. The workshop was intended to provide an overview of the state of the art and future perspectives of such interfaces; this paper represents is a collection of opinions expressed by each and every researcher/group involved in it.
The risk of sustaining injuries increases with fatigue. The aim of this study was to analyze the influence of fatigue on dynamic postural control in jump landing and stabilization (ST) in athletes of different levels. In all, 18 high-performance ball sports athletes and 24 recreationally active subjects performed a jump test (JT) before and at 1, 5, 10, 15, and 20 minutes after a 30-minute treadmill run at the individual anaerobic threshold. An overhead ball switch hit during a forward jump triggered indicator lamps on either side of a force plate. After landing on the plate, ST on 1 leg (no light cue) or a second jump sideways (toward a light cue) was required. The ST force integral index was calculated for the ST trials. Dynamic postural control was significantly impaired in jump landing and ST in the first minute after the run: mean difference ± SD: 0.25 ± 0.48 m·s-1 (95% confidence interval: 0.10-0.40 m·s-1, p = 0.043; analysis of variance). No significant group differences were found. Under fatigued conditions, dynamic postural control in jump landing was impaired in an unexpected ST task. Not only recreational but also high-performance athletes were affected. Ball sports athletes could add a training exercise to their workout, which alternates between periods of high effort and neuromuscular training. Resistance to fatigue effects should be checked on a regular basis using JTs.
Background. The reliable stratification of homogeneous subgroups and the prediction of future clinical outcomes within heterogeneous neurological disorders is a particularly challenging task. Nonetheless, it is essential for the implementation of targeted care and effective therapeutic interventions. Objective. This study was designed to assess the value of a recently developed regression tool from the family of unbiased recursive partitioning methods in comparison to established statistical approaches (eg, linear and logistic regression) for predicting clinical endpoints and for prospective patients' stratification for clinical trials. Methods. A retrospective, longitudinal analysis of prospectively collected neurological data from the European Multicenter study about Spinal Cord Injury (EMSCI) network was undertaken on C4-C6 cervical sensorimotor complete subjects. Predictors were based on a broad set of early (<2 weeks) clinical assessments. Endpoints were based on later clinical examinations of upper extremity motor scores and recovery of motor levels, at 6 and 12 months, respectively. Prediction accuracy for each statistical analysis was quantified by resampling techniques. Results. For all settings, overlapping confidence intervals indicated similar prediction accuracy of unbiased recursive partitioning to established statistical approaches. In addition, unbiased recursive partitioning provided a direct way of identification of more homogeneous subgroups. The partitioning is carried out in a data-driven manner, independently from a priori decisions or predefined thresholds. Conclusion. Unbiased recursive partitioning techniques may improve prediction of future clinical endpoints and the planning of future SCI clinical trials by providing easily implementable, data-driven rationales for early patient stratification based on simple decision rules and clinical read-outs.
Brain computer interfaces (BCIs) are devices that measure brain activities and translate them into control signals used for a variety of applications. Among them are systems for communication, environmental control, neuroprostheses, exoskeletons, or restorative therapies. Over the last years the technology of BCIs has reached a level of matureness allowing them to be used not only in research experiments supervised by scientists, but also in clinical routine with patients with neurological impairments supervised by clinical personnel or caregivers. However, clinicians and patients face many challenges in the application of BCIs. This particularly applies to high spinal cord injured patients, in whom artificial ventilation, autonomic dysfunctions, neuropathic pain, or the inability to achieve a sufficient level of control during a short-term training may limit the successful use of a BCI. Additionally, spasmolytic medication and the acute stress reaction with associated episodes of depression may have a negative influence on the modulation of brain waves and therefore the ability to concentrate over an extended period of time. Although BCIs seem to be a promising assistive technology for individuals with high spinal cord injury systematic investigations are highly needed to obtain realistic estimates of the percentage of users that for any reason may not be able to operate a BCI in a clinical setting.
Incomplete spinal cord injury (iSCI) leads to motor and sensory deficits. Even in ambulatory persons with good motor function an impaired proprioception may result in an insecure gait. Limited internal afferent feedback (FB) can be compensated by provision of external FB by therapists or technical systems. Progress in computational power of motion analysis systems allows for implementation of instrumented real-time FB. The aim of this study was to test if individuals with iSCI can normalize their gait kinematics during FB and more importantly maintain an improvement after therapy.
The bilateral loss of the grasp function associated with a lesion of the cervical spinal cord severely limits the affected individuals ability to live independently and return to gainful employment after sustaining a spinal cord injury (SCI). Any improvement in lost or limited grasp function is highly desirable. With current neuroprostheses, relevant improvements can be achieved in end users with preserved shoulder and elbow, but missing hand function.
Suicides by self-poisoning are common in all parts of the world. Among these intoxications, gases are rarely used, especially carbon dioxide (CO2). Very few cases of self-inflicted and deliberate carbon dioxide poisonings have been reported. This paper presents two uncommon suicides by carbon dioxide intoxication. In one case, a 53-year-old man tightly sealed a small bathroom and locked himself in it likely with dry ice. Warning notices were tagged to the door. In another case, a 48-year-old man working in a restaurant committed suicide by closing himself in a walk-in refrigerator and opening the stored carbon dioxide containers intended for the beverage dispensing equipment. The limited possibilities of proving lethal CO2 intoxications post-mortem necessitate a close cooperation of the involved parties during investigation. Only the synopsis of all findings permits a sound assessment regarding the manner and cause of death.
A novel non-invasive technique for monitoring fluid content in the human bladder is described. Specifically, a precommercial electric impedance tomograph (EIT) was applied to measure and visualize impedance changes in the lower torso due to changes in bladder volume. Preliminary measurements were conducted during routine urodynamic tests of nine male paraplegic patients, in whom a contrast agent was slowly infused into the bladder for diagnostic purposes. In some patients, a good correlation between bladder volume and EIT measurements was found, whereas in others the correlation was still good but inverted, presumably due to a poor electrode positioning. These preliminary results indicate that a sufficiently accurate finite element modeling of the impedance distribution in the abdomen, and proper electrode positioning aids, are important prerequisites to enable this technology to be used for routine measurement of bladder volume.
The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), defined by the American Spinal Injury Association (ASIA), and particularly the ASIA Impairment Scale (AIS) are widely used for research and clinical purposes. Although detailed procedures for scaling, scoring, and classification have been defined, misclassifications remain a major problem, especially for cases with missing (i.e., not testable [NT]) data. This work aimed to implement computer-based classification algorithms that included rules for handling NT data. A consistent and structured algorithmic scoring, scaling, and classification scheme, and a computerized application have been developed by redefining logical/mathematical imprecisions. Existing scoring rules are extended for handling NT segments. Design criterion is a pure logical approach so that substitution of non-testability for all valid examination scores leads to concordant results. Nine percent of 5542 datasets from 1594 patients in the database of the European Multicenter Study of Human Spinal Cord Injury (EM-SCI) contained NT segments. After adjusting computational algorithms, the classification accuracy was equivalent between clinical experts and the computational approach and resulted in 84% valid AIS classifications within datasets containing NT. Additionally, the computational method is much more efficient, processing approximately 200,000 classifications/sec. Computational algorithms offer the ability to classify ISNCSCI subscores efficiently and without the risk of human-induced errors. This is of particular clinical relevance, since these scores are used for early predictions of neurological recovery and functional outcome for patients with spinal cord injuries.
The loss of the grasp function in cervical spinal cord injured (SCI) patients leads to life-long dependency on caregivers and to a tremendous decrease of the quality of life. This article introduces the novel non-invasive modular hybrid neuro-orthosis OrthoJacket for the restoration of the restricted or completely lost hand and arm functions in high tetraplegic SCI individuals. The primary goal of the wearable orthosis is to improve the paralysed upper extremity function and, thus, to enhance a patients independence in activities of daily living. The system combines the advantage of orthotics in mechanically stabilising joints together with the possibilities of functional electrical stimulation for activation of paralysed muscles. In patients with limited capacity, for force generation, flexible fluidic actuators are used to support the movement. Thus, the system is not only intended for functional restoration but also for training. Several sensor systems together with an intelligent signal processing allow for automatic adaptation to the anatomical and neurological individualities of SCI patients. The integration of novel user interfaces based on residual muscle activities and detection of movement intentions by real-time data mining methods will enable the user to autonomously control the system in a natural and cooperative way.
In this paper we show how healthy subjects can operate a non-invasive asynchronous BCI for controlling a FES neuroprosthesis and manipulate objects to carry out daily tasks in ecological conditions. Both, experienced and novel subjects proved to be able to deliver mental commands with high accuracy and speed. Our neuroprosthetic approach relies on a natural interaction paradigm, where subjects delivers congruent MI commands (i.e., they imagining a movement of the same hand they control through FES). Furthermore, we have tested our approach in a common daily task such as handwriting, which requires the user to split his/her attention to multitask between BCI control, reaching, and the primary handwriting task itself. Interestingly, the very low number of erroneous trials illustrates how during the experiments subjects were able to deliver commands just when they intended to do so. Similarly, the subjects could perform actions while delivering, or preparing to deliver, mental commands.
In incomplete spinal cord injured subjects, task-oriented training regimes are applied for enhancement of neuroplasticity to improve gait capacity. However, a sufficient training intensity can only be achieved during the inpatient phase, which is getting shorter and shorter due to economic restrictions. In the clinical environment, complex and expensive robotic devices have been introduced to maintain the duration and the intensity of the training, but up to now only a few exist for continuation of automated locomotion training at home. For continuation of the automated locomotion training at home prototypes of the compact, pneumatically driven orthosis MoreGait have been realized, which generate the key afferent stimuli for activation of the spinal gait pattern generator. Artificial pneumatic muscles with excellent weight-to-force ratio and safety characteristics have been integrated as joint actuators. Additionally, a Stimulative Shoe for generation of the appropriate foot loading pattern has been developed without the need for verticalization of the user. The first results of the pilot study in eight chronic incomplete spinal cord injured subjects indicate that the home-based therapy is safe and feasible. The therapy related improvements of the walking capacity are in the range of locomotion robots used in clinical settings.
Advanced tumor disease and metastatic spinal cord compression (MSCC) are two entities with a high impact on patients quality of life. However, prognostic factors on the outcome after primary decompressive surgery are less well-defined and not yet standardized. The aim of this review was to identify prognostic variables that predict functional or ambulatory outcomes in surgically treated patients with symptomatic MSCC.
Spinal cord injury (SCI) causes muscle atrophy, which is particularly severe, due to inability to perform tetanic contractions, when lower motor neurons (LMN) are involved. We performed a longitudinal study in 25 Europeans suffering from complete conus cauda syndrome from 0.7 to 8.7 years comparing functional and structural thigh muscle properties before and after 2 years of home-based daily training by functional electrical stimulation (FES). The mid-term results after 1 year and preliminary muscle biopsy observations at project end-point from a subset of subjects are here reported.
Spinal cord injury (SCI) results in deficits of sensory, motor and autonomous functions, with tremendous consequences for the patients. The loss of motor functions, especially grasping, leads to a dramatic decrease in quality of life. With the help of neuroprostheses, the grasp function can be substantially improved in cervical SCI patients. Nowadays, systems for grasp restoration can only be used by patients with preserved voluntary shoulder and elbow function. In patients with lesions above the 5th vertebra, not only the voluntary movements of the elbow are restricted, but also the overall number of preserved movements available for control purposes decreases. A Brain-Computer Interface (BCI) offers a method to overcome this problem. This work gives an overview of the Graz BCI used for the control of grasp neuroprostheses as well as a new control method for combining grasp and elbow function is introduced.
The purpose of this work was to reliably acquire and evaluate diffusion tensor data of the cervical spine. Thereto, we describe an optimized, time-efficient inner-volume echo planar imaging sequence. Multislice capability is achieved by restoring the magnetization in neighbouring slices early during the twice refocused diffusion preparation. The acquired diffusion images showed compelling image quality. To reduce the arbitrariness of conventional region of interest (ROI) analysis, a tissue classification algorithm was applied. The classification was independent of the ROI shape and hence, a reliable and stable evaluation of the diffusion tensor could be achieved. The mean fractional anisotropy (FA) of five healthy subjects decreased from C1 (FA = 0.81 +/- 0.03) to C7 (FA = 0.60 +/- 0.03), while the mean apparent diffusion coefficient (ADC) increased from C1 (ADC= 0.78 +/- 0.08 microm2/ms) to C7 (ADC = 1.08 +/- 0.08 microm2/ms). In subsequent measurements of the individual healthy subjects, the standard deviation of the FA was 0.024 +/- 0.011 and the standard deviation of the ADC was 0.045 +/- 0.017 microm2/ms. The FA values of a patient with acute ischemic spinal trauma were significantly lower and changed more drastically than ADC values. Here, absolute FA ranged from 0.23 to 0.42, showing that DTI of the spine may serve as surrogate marker for tissue integrity and therapy monitoring.
The neurological severity of a spinal cord injury (SCI) is commonly classified according to the American Spinal Injury Association (ASIA) Impairment Scale (AIS). The aim of this study was to assess the course of the AIS following SCI, and to discern the nature of any changes in the classification that occur. Assessments were performed in a European cohort of SCI patients within 2 weeks and at 1, 3, 6, and 12 months after the initial injury. Overall, about 70% of the patients initially diagnosed as AIS A did not convert, as did 90% of the AIS D patients. When only evaluating patients with complete datasets, 68% did not convert, while the AIS category improved in 30% of patients and deteriorated in 2%. A change in the last sacral segments (40%), motor improvement (31%), sensory improvement (19%), and a change in the neurological level of the SCI (10%) contributed to or accompanied the AIS conversion. When the AIS remained unchanged between successive assessment points, there was no change in the number of muscles graded three or more (NMG3(+)) in 73% of the transitions. An improvement in AIS was associated with a gain in NMG3(+) in 49% of the transitions, while an aggravation in AIS was accompanied by a loss in NMG3(+) in 10% of the transitions. These results, documenting a substantial amount of spontaneous AIS conversions, should be taken into consideration when designing clinical trials to assess the effects of potential new treatments for SCI.
A brain-computer interface (BCI) based on near-infrared spectroscopy (NIRS) could act as a tool for rehabilitation of stroke patients due to the neural activity induced by motor imagery aided by real-time feedback of hemodynamic activation. When combined with functional electrical stimulation (FES) of the affected limb, BCI is expected to have an even greater benefit due to the contingency established between motor imagery and afferent, haptic feedback from stimulation. Yet, few studies have explored such an approach, presumably due to the difficulty in dissociating and thus decoding the hemodynamic response (HDR) between motor imagery and peripheral stimulation. Here, for the first time, we demonstrate that NIRS signals elicited by motor imagery can be reliably discriminated from those due to FES, by first performing a univariate analysis of the NIRS signals, and subsequently by multivariate pattern classification. Our results showing that robust classification of motor imagery from the rest condition is possible support previous findings that imagery could be used to drive a BCI based on NIRS. More importantly, we demonstrate for the first time the successful classification of motor imagery and FES, indicating that it is technically feasible to implement a contingent NIRS-BCI with FES.
Over the last decade the improvement of a missing hand function by application of neuroprostheses in particular the implantable Freehand system has been successfully shown in high spinal cord injured individuals. The clinically proven advantages of the Freehand system is its ease of use, the reproducible generation of two distinct functional grasp patterns and an analog control scheme based on movements of the contralateral shoulder. However, after the Freehand system is not commercially available for more than ten years, alternative grasp neuroprosthesis with a comparable functionality are still missing. Therefore, the aim of this study was to develop a non-invasive neuroprosthesis and to show that a degree of functional restoration can be provided to end users comparable to implanted devices. By introduction of an easy to handle forearm electrode sleeve the reproducible generation of two grasp patterns has been achieved. Generated grasp forces of the palmar grasp are in the range of the implanted system. Though pinch force of the lateral grasp is significantly lower, it can effectively used by a tetraplegic subject to perform functional tasks. The non-invasive grasp neuroprosthesis developed in this work may serve as an easy to apply and inexpensive way to restore a missing hand and finger function at any time after spinal cord injury.
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