Evaluation of improved bi-manual endoscopic resection using a customizable 3D-printed manipulator system designed for use with standard endoscopes: a feasibility study using a porcine ex-vivo model

Background and study aims A major drawback of endoscopic en-bloc resection technique is its inability to perform bimanual tasks. Although endoscopic platforms that enable bimanual tasks are commercially available, they are neither approved for various locations nor adaptable to specific patients and indications. Methods Based on evolution of an adaptive 3D-printable platform concept, system variants with different characteristic properties were evaluated for ESD scenarios, ex-vivo in two locations in the stomach and colorectum. Results In total 28 ESDs were performed (7 antrum, 7 corpus in inversion, 7 cecum, 7 rectum) in a porcine ex-vivo setup. ESD was feasible in 21 cases. Investigated manipulator variants are differently well suited for performing ESD within the varying interventions scenarios. Dual-arm manipulators allowed autonomous ESD, while single-arm flexible manipulators could be used more universally due to their compact design, especially for lesions difficult to access. Pediatric scopes were too frail to guide the overtube-manipulators in extremely angled positions. Working in the rectum was impaired using long-sized manipulator arms. Conclusions The presented endoscopic platform based on 3D-printable and customizable manipulator structures might be a promising approach for future improvement of ESD procedure. With regard to localization, especially flexible manipulators attached to standard endoscopes appear to be most promising for further application of specific and individualised manipulator systems.

Corpus callosal microstructure predicts bimanual motor performance in chronic stroke survivors

Much of the research using diffusion tensor imaging (DTI) in stroke focuses on characterizing the microstructural status of corticospinal tracts and its utility as a prognostic biomarker. However, the ischemic event in the lesioned cortex also triggers structural and functional alterations in its contralateral homolog through the corpus callosum (CC), known as transcallosal diaschisis. The few studies that have characterized the microstructural status of the CC using DTI only examine its relationship with paretic limb performance. Given the well-established role of the CC for bimanual coordination, especially fibers connecting the larger sensorimotor networks such as prefrontal, premotor and supplementary motor regions, we examine the relationship between the microstructural status of the CC and bimanual performance in chronic stroke survivors (n = 41). We used movement times for two self-initiated and self-paced bimanual tasks to capture bimanual performance. Using publicly available control datasets (n = 52), matched closely for acquisition parameters, including sequence, diffusion gradient strength and number of directions, we also explored the effect of age and stroke on callosal microstructure. We found that callosal microstructure was significantly associated with bimanual performance in chronic stroke survivors such that those with lower callosal FA were slower at completing the bimanual task. Notably, while the primary sensorimotor regions (CC3) showed the strongest relationship with bimanual performance, this was closely followed by the premotor/supplementary motor (CC2) and the prefrontal (CC1) regions. We used multiple mixed regression to systematically account for loss of callosal axons (i.e., normalized callosal volume) as well as differences in lesion size and other metrics of structural damage. Chronic stroke survivors presented with significantly greater loss of callosal fiber orientation (lower mean FA) compared to neurologically intact, age-similar controls, who in turn presented with lower callosal FA compared to younger controls. The effect of age and stroke were observed for all regions of the CC except the splenium. These preliminary findings suggest that in chronic stroke survivors with relatively localized lesions, callosal microstructure can be expected to change beyond the primary sensorimotor regions and might impact coordinated performance of self-initiated and cooperative bimanual tasks.

Feasibility and Safety of Bilateral Hybrid EEG/EOG Brain/Neural–Machine Interaction

Cervical spinal cord injuries (SCIs) often lead to loss of motor function in both hands and legs, limiting autonomy and quality of life. While it was shown that unilateral hand function can be restored after SCI using a hybrid electroencephalography/electrooculography (EEG/EOG) brain/neural hand exoskeleton (B/NHE), it remained unclear whether such hybrid paradigm also could be used for operating two hand exoskeletons, e.g., in the context of bimanual tasks such as eating with fork and knife. To test whether EEG/EOG signals allow for fluent and reliable as well as safe and user-friendly bilateral B/NHE control, eight healthy participants (six females, mean age 24.1 ± 3.2 years) as well as four chronic tetraplegics (four males, mean age 51.8 ± 15.2 years) performed a complex sequence of EEG-controlled bilateral grasping and EOG-controlled releasing motions of two exoskeletons visually presented on a screen. A novel EOG command performed by prolonged horizontal eye movements (>1 s) to the left or right was introduced as a reliable switch to activate either the left or right exoskeleton. Fluent EEG control was defined as average “time to initialize” (TTI) grasping motions below 3 s. Reliable EEG control was assumed when classification accuracy exceeded 80%. Safety was defined as “time to stop” (TTS) all unintended grasping motions within 2 s. After the experiment, tetraplegics were asked to rate the user-friendliness of bilateral B/NHE control using Likert scales. Average TTI and accuracy of EEG-controlled operations ranged at 2.14 ± 0.66 s and 85.89 ± 15.81% across healthy participants and at 1.90 ± 0.97 s and 81.25 ± 16.99% across tetraplegics. Except for one tetraplegic, all participants met the safety requirements. With 88 ± 11% of the maximum achievable score, tetraplegics rated the control paradigm as user-friendly and reliable. These results suggest that hybrid EEG/EOG B/NHE control of two assistive devices is feasible and safe, paving the way to test this paradigm in larger clinical trials performing bimanual tasks in everyday life environments.

The Probability of Choosing Both Hands Depends on an Interaction Between Motor Capacity and Limb-Specific Control in Chronic Stroke

A goal of rehabilitation after stroke is to promote pre-stroke levels of arm use for everyday, frequently bimanual, functional activities. We reasoned that, after a stroke, the choice to use one or both hands for bimanual tasks might depend not only on residual motor capacity but also the specialized demands imposed by the task on the paretic hand. To capture spontaneous, task-specific choices, we covertly observed 50 pre-stroke right-handed chronic stroke survivors (25 left hemisphere damage, LHD) and recorded their hand use strategies for two pairs of bimanual tasks with distinct demands: one with greater precision requirements (photo-album tasks), and another with greater stabilization requirements (letter-envelope tasks). The primary outcome was the choice to use one or both hands. Logistic regression was used to test the hypothesis that the probability of choosing a bimanual strategy would be greater in those with less severe motor impairment and those with LHD. When collapsed across the four subtasks, we found support for this hypothesis. However, notably, the influence of these factors on bimanual choice varied based on task demands. For the photo-album task, the probability of a bimanual strategy was greater for those with LHD compared to RHD, regardless of the degree of motor impairment. For the letter-envelope task, we found a significant interaction between impairment and side of lesion in determining the likelihood of choosing both hands. Therefore, the manner in which side of lesion moderates the effect of impairment on hand use depends on the task.

Interaction between position sense and force control in bimanual tasks

Background Several daily living activities require people to coordinate the motion and the force produced by both arms, using their position sense and sense of effort. However, to date, the interaction in bimanual tasks has not been extensively investigated. Methods We focused on bimanual tasks where subjects were required: (Experiment 1) to move their hands until reaching the same position – equal hand position implied identical arm configurations in joint space - under different loading conditions;(Experiment 2) to produce the same amount of isometric force by pushing upward, with their hands placed in symmetric or asymmetric positions. The arm motions and forces required for accomplishing these tasks were in the vertical direction. We enrolled a healthy population of 20 subjects for Experiment 1 and 25 for Experiment 2. Our primary outcome was the systematic difference between the two hands at the end of each trial in terms of position for Experiment 1 and force for Experiment 2. In both experiments using repeated measure ANOVA we evaluated the effect of each specific condition, namely loading in the former case and hand configuration in the latter. Results In the first experiment, the difference between the hands’ positions was greater when they were concurrently loaded with different weights. Conversely, in the second experiment, when subjects were asked to exert equal forces with both arms, the systematic difference between left and right force was not influenced by symmetric or asymmetric arm configurations, but by the position of the left hand, regardless of the right hand position. The performance was better when the left hand was in the higher position. Conclusions The experiments report the reciprocal interaction between position sense and sense of effort inbimanual tasks performed by healthy subjects. Apart for the intrinsic interest for a better understanding of basic sensorimotor processes, the results are also relevant to clinical applications, for defining functional evaluation and rehabilitative protocols for people with neurological diseases or conditions that impair the ability to sense and control concurrently position and force.