Abstract-Functional electrical stimulation (FES) of upper limbs can be used for the recovery of some hand functions on patients with CNS lesions. This study deals with the control of FES by means of myoelectrical activity detected from voluntarily activated paretic muscles. The specific aim of this paper is to evaluate the accuracy of myoelectrical control in terms of produced force and movement.For this purpose, a specific device called myoelectrical controlled functional electrical stimulator (MeCFES) has been developed and applied to six tetraplegic patients with a spinal cord lesion and one stroke hemiplegic patient.Residual myoelectric signals from the paretic wrist extensor (m. extensor carpi radialis, ECR) have been used to control stimulation of either the wrist extension (i.e., the same muscle) or thumb flexion. A tracking test based on a visual feedback of the produced force or movement compared to a reference target trajectory was used to quantify control accuracy. A comparison was made between the tracking performances of each subject with and without the MeCFES and the learning process for two of the subjects were observed during consecutive sessions.Results showed that the wrist extension was improved in three out of five C5 SCI patients and the thumb flexion was largely increased in one incomplete C3 SCI patient. The hemiplegic patient showed limited thumb control with the MeCFES but indicated the possibility of a carry over effect. It was found that a low residual natural force resulted in a less accurate movement but also with a large increase (up to ten times) of the muscle output. On the contrary, persons with a medium residual force obtained a smaller amplification of muscle force with a higher tracking accuracy.
A new computerised test adopting touch-screen technology has been developed to assess the visuo-motor exploration of extra-personal space. The test was derived from well-known paper-and-pencil cancellation tasks used widely in the diagnosis and quantitative assessment of unilateral spatial neglect (USN), a neuropsychological syndrome that is more frequent and severe after damage to the right cerebral hemisphere. A main component deficit of USN is the defective visuo-motor exploration of the side of space contralateral to the side of the lesion (contralesional), namely, in right-sided brain-damaged patients it occurs on the left side and vice versa. The computer-based paradigm consisted of a visuo-motor spatial exploratory task: the subjects were instructed to touch, in any order they wished, all the targets they detected on a computer touch-screen. This measured the time of occurrence and the spatial co-ordinates of each touch event and forwarded the data to the computer for storage; the computer provided feedback to the subject by 'tagging' the touched target. The paradigm allowed the calculation of accuracy and latency indexes and recorded the exploratory pathway taken by each subject. A pilot study was performed in ten normal subjects and 15 brain-damaged patients, with and without psychometric evidence of USN; the results showed that the equipment was able to provide quantitative indexes related to the spatial-temporal aspects of exploratory ability, which are useful for diagnostic purposes, and revealed significant differences between the controls and patients with USN: the overall average values of latency and crossing indexes increased in patients with USN, compared with the controls (latency from 0.77 to 1.90s; path crossing index from 7.0% to 59.5%), and the significantly negative USN patient latency gradient (-2.79 against a null control value) evidenced a worsening of performance towards the left side.
The goal of the present work was to develop and test an innovative system for the training of paraplegic patients when they are standing up. The system consisted of a computer-controlled stimulator, surface electrodes for quadricep muscle stimulation, two knee angle sensors, a digital proportional-integrative-derivative (PID) controller and a mechanical device to support, partially, the body weight (weight reliever (WR)). A biomechanical model of the combined WR and patient was developed to find an optimum reference trajectory for the PID controller. The system was tested on three paraplegic patients and was shown to be reliable and safe. One patient completed a 30-session training period. Initially he was able to stand up only with 62% body weight relief, whereas, after the training period, he performed a series of 30 standing-up/sitting-down cycles with 45% body weight relief. The closed-loop controller was able to keep the patient standing upright with minimum stimulation current, to compensate automatically for muscle fatigue and to smooth the sitting-down movement. The limitations of the controller in connection with a highly non-linear system are considered.
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