Discrimination of phantom hand sensations elicited by afferent electrical nerve stimulation in below-elbow amputees.

The necessity for a sensory feedback system that would enhance patient acceptability of motorized hand prostheses is now generally acknowledged. Afferent electrical stimulation of the nerves in the amputation stump can convey sensory feedback from prostheses with the advantage of eliciting sensations in the phantom image of the lost hand. Experiments with percutaneous nerve stimulation of the amputation stump in below-elbow amputees showed that with stable electrode conditions, amplitude modulated stimulation was better than frequency modulated stimulation in terms of accuracy, delay, and transinformation both with intermittent and uninterrupted stimulation. With unstable electrode conditions, different results were noticed, since amplitude modulated stimulation is very sensitive even to minor changes in electrode position. It is concluded that afferent electrical nerve stimulation with adequate training and stable electrodes had characteristics of accuracy, transinformation and delay which are good enough to make it a suitable method of conveying information in a prosthesis feedback system.     

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Psychophysiological stress responses in amputees with and without phantom limb pain

The present experiment tested the hypothesis that phantom limb pain amputees show a different pattern of psychophysiological reactivity to stress compared with painfree amputees. Six phantom limb pain (PLP) and five painfree upper-extremity amputees were administered two groups of tasks: stressful and relaxing. The measured dependent variables were skin temperature recorded at both stump and intact site, heart rate, blood pressure, subjective pain and stress ratings. Phantom limb pain patients were characterized by higher stump temperature compared with phantom limb painfree patients. This effect was observed during the whole recording. Consistently with the between-subjects effect, when PLP patients exhibited higher skin temperature (during relaxation, compared with during stressful tasks), they perceived more pain. The experiment showed higher cardiovascular reactivity in PLP patients, specifically to the stressful free-speech task, which focused on recollection of the amputation event. As compared with the painfree patients, during the personal stressor, PLP patients' heart rate and systolic blood pressure increased, indicating a greater sympathetic response. Results indicate that peripheral factors, such as stump temperature reliably differentiate PLP from painfree patients. Moreover, the clear cardiovascular hyperreactivity observed in PLP patients during their report of amputation suggests that PLP is associated with a long-term emotional memory for the painful experience of that event. These results are consistent with most reports in the literature relating phantom pain development to the experience of preamputation pain.     

Neuromuscular electrical stimulation for pain management in combat‐related transtibial amputees during rehabilitation and prosthetic training

Military members with war‐related lower limb amputation experience a range of acute and chronic pain symptoms. The purpose of this study was to evaluate pain during 12 weeks of a military amputee rehabilitation program (MARP ) pre‐ and post‐prosthesis. The data for this study were drawn from a randomized clinical trial comparing MARP supplemented with neuromuscular electrostimulation (MARP  + NMES , n  = 23) to MARP alone (n  = 21) for service members with unilateral transtibial amputation. The McGill Pain Questionnaire (MPQ ) and phantom limb pain/sensations were assessed at baseline, 3, 6, 9, and 12 weeks. Changes within‐ and between‐groups were analyzed with generalized mixed models. Participants reported mild‐to‐moderate pain at all visits, and improved significantly on the MPQ and frequency of phantom limb pain/sensations (p  < .001 for effect of time). Group by time interactions were not significant, indicating both groups showed similar improvement. Univariate tests showed the NMES  + MARP group had lower pain intensity than MARP ‐only group at weeks 3 and 6. Participants in MARP demonstrated good overall pain control and reported reduced pain and fewer days with phantom limb pain/sensations over 12 weeks. Adding NMES to MARP may be beneficial in early rehabilitation, and NMES could potentially enhance physical therapy participation by decreasing pain.     

Motor control over the phantom limb in above-elbow amputees and its relationship with phantom limb pain

Recent evidence shows that the primary motor cortex continues to send motor commands when amputees execute phantom movements. These commands are retargeted toward the remaining stump muscles as a result of motor system reorganization. As amputation-induced reorganization in the primary motor cortex has been associated with phantom limb pain we hypothesized that the motor control of the phantom limb would differ between amputees with and without phantom limb pain. Eight above-elbow amputees with or without pain were included in the study. They were asked to produce cyclic movements with their phantom limb (hand, wrist, and elbow movements) while simultaneously reproducing the same movement with the intact limb. The time needed to complete a movement cycle and its amplitude were derived from the kinematics of the intact limb. Electromyographic (EMG) activity from different stump muscles and from the homologous muscles on the intact side was recorded. Different EMG patterns were recorded in the stump muscles depending on the movement produced, showing that different phantom movements are associated with distinct motor commands. Phantom limb pain was associated with some aspects of phantom limb motor control. The time needed to complete a full cycle of a phantom movement was systematically shorter in subjects without phantom limb pain. Also, the amount of EMG modulation recorded in a stump muscle during a phantom hand movement was positively correlated with the intensity of phantom limb pain. Since phantom hand movement–related EMG patterns in above-elbow stump muscles can be considered as a marker of motor system reorganization, this result indirectly supports the hypothesis that amputation-induced plasticity is associated with phantom limb pain severity. The discordance between the (amputated) hand motor command and the feedback from above-elbow muscles might partially explain why subjects exhibiting large EMG modulation during phantom hand movement have more phantom limb pain.     

Sensory feedback prosthesis reduces phantom limb pain: proof of a principle

Background

Constrained functionality and phantom limb pain (PLP) are major concerns for forearm amputees. Neuroscientific investigations of PLP suggest that behaviorally relevant stimulation of the stump can decrease PLP. Furthermore the prosthesis user could use feedback information of the prosthesis hand for optimizing prosthesis motor control when handling soft and fragile objects. Somatosensory feedback information from a prosthetic hand may therefore help to improve prosthesis functionality and reduce phantom limb pain.

Objectives

We wanted to find out whether a two weeks training on a hand prosthesis that provides somatosensory feedback may help to improve prosthesis functionality and reduce phantom limb pain.

Methods

Eight forearm amputees with phantom limb pain were trained for two weeks to use a hand prosthesis with somatosensory feedback on grip strength.

Results

The current study demonstrates a significant increase of functionality of the prosthesis in everyday tasks. Furthermore, the study shows that usage of a prosthesis that provides somatosensory feedback on the grip strength is effective to reduce phantom limb pain.

Conclusions

A prosthesis with a feedback function appears to be a promising therapeutic tool to reduce phantom limb pain and to increase functionality in everyday tasks. Future studies should further investigate the scope of application of that principle.     

Phantom pain following limb amputation in a paraplegic. A case report

The pain of the phantom limb remains a diagnostic and therapeutic challenge. A case is reported in which a paraplegic patient with full sensory ablation below T11 experienced phantom limb pain only after actual amputation of one of his legs. This suggests that the cause in this case could only be central in origin. Visual appreciation seems to be an important step in this process.     

Effects of short-term training on sensory and motor function in severed nerves of long-term human amputees

Much has been studied and written about plastic changes in the CNS of humans triggered by events such as limb amputation. However, little is known about the extent to which the original pathways retain residual function after peripheral amputation. Our earlier, acute study on long-term amputees indicated that central pathways associated with amputated peripheral nerves retain at least some sensory and motor function. The purpose of the present study was to determine if these functional connections would be strengthened or improved with experience and training over several days time. To do this, electrodes were implanted within fascicles of severed nerves of long-term human amputees to evaluate the changes in electrically evoked sensations and volitional motor neuron activity associated with attempted phantom limb movements. Nerve stimulation consistently resulted in discrete, unitary, graded sensations of touch/pressure and joint-position sense. There was no significant change in the values of stimulation parameters required to produce these sensations over time. Similarly, while the amputees were able to improve volitional control of motor neuron activity, the rate and pattern of change was similar to that seen with practice in normal individuals on motor tasks. We conclude that the central plasticity seen after amputation is most likely primarily due to unmasking, rather than replacement, of existing synaptic connections. These results also have implications for neural control of prosthetic limbs.     

大腿假肢支撑期有限元分析

目的分析大腿截肢患者的硅胶套材料属性,对支撑期残肢与接受腔之间接触面的力学分布的影响,为大腿假肢适配方案中硅胶套的选取提供参考。方法利用计算机断层扫描技术获取大腿截肢患者残端与接受腔的断层图像,通过影像学信息和工程学方法,分别获取接受腔、硅胶套、残肢、骨骼等结构的三维模型;根据角度变化调整模型,获得初始接触期、负荷反应期、站立中期、站立末期、摆动前期5个时相的组装模型;根据三维动作捕捉系统Motion和Kistler三维测力平台测得的地面反作用力及髋关节角度变化的结果,对5个时相下大腿假肢模型分别进行有限元非线性接触分析;在此基础上,模拟分析了硅胶套不同弹性模量的变化对残肢表面等效应力以及剪切应力分布的影响。结果穿戴不同弹性模量的硅胶套时,残肢所受最大等效应力以及最大剪切应力在初始接触期、负荷反应期、站立中期、站立末期时相时出现在残肢内侧和接受腔口型边缘对应的残肢位置,在摆动前期时相时则出现在残肢内侧、接受腔口型边缘对应的残肢位置和坐骨周围等位置。当硅胶套弹性模量在0.98~2.70 MPa范围内变化时,在摆动前期残肢所受等效应力变化范围为13.85~23.55 k Pa,最大剪切应力变化范围为7.82~13.46 k Pa,而其他时相基本一致。结论硅胶套的力学特性影响大腿假肢残肢与接受腔之间接触面的受力分布,摆动前期残肢所受最大等效应力与最大剪切应力随硅胶套弹性模量变化大,在实际适配过程中需注意。     

The relationship of perceptual phenomena and cortical reorganization in upper extremity amputees

In this study 16 unilateral upper extremity amputees participated in a comprehensive psychophysiological examination that included the assessment of painful and non-painful phantom and stump sensations, thermal and electric perception as well as two-point discrimination thresholds, the detailed analysis of referred sensation and the measurement of reorganizational changes in primary somatosensory cortex using neuroelectric source imaging. Reorganization of the primary somatosensory cortex was associated with increased habitual phantom limb pain, telescoping, non-painful stump sensations and painful referred sensation induced by painful stimulation. It was unrelated to non-painful phantom sensations, non-painful referred sensation elicited by painful or non-painful stimulation, painful referred sensation elicited by non-painful stimulation, perception thresholds and stump pain.These data substantiate the hypothesis that painful and non-painful phantom phenomena are mediated by different neural substrates.     

Cortical focusing is an alternative explanation for improved sensory acuity on an amputation stump

The ability to localize a sensory stimulus on the body surface (locognosia) has been investigated in normal subjects in a quest to find an explanation for the reported findings of improved sensory acuity on an amputation stump. We have shown that when attending to a smaller area of skin, during the testing procedure, locognosia improves (P<0.001) by a similar degree to that seen in amputees. Such selective attention is likely to occur in upper limb amputees as they have a reduced area of skin on which to focus during sensory testing. This represents a further explanation for improved sensory acuity on an amputation stump without implicating plasticity of connections within the somatosensory cortex.     

Electrical stimulation and myoelectric control. A theoretical and applied study relevant to prosthesis sensory feedback

Electrical nerve stimulation applied to an amputation stump to convey sensory feedback from a myoelectric hand prosthesis inevitably interferes with the prosthesis control system. The intention of this study is to investigate the extent of the interference to allow the implementation of a self-contained myoelectric prosthesis with electrical nerve stimulation feedback. The interference voltage sensed by two types of e.m.g. pick-up electrode units is studied as a function of the distance between the stimulating electrodes and the pick-up electrode units. Results obtained from experiments performed on human subjects andin vitro are supported by results based on electrical field theory. It is concluded that electrical nerve stimulation for prosthesis sensory feedback can be used close enough to myoelectric control systems to be in accordance with the principle of prothesis self-containment.     

Gating of tactile input from the hand

Summary Intraneural microstimulation within the median nerve of alert healthy subjects was used to evoke tactile sensations at threshold for conscious detection. The effect of movement on these sensations was studied by asking the subjects to estimate their magnitude before, during and after movement of the appropriate finger at different speeds. It was found that sensations of flutter and pressure were both attenuated by movement, as was the magnitude of spontaneous paraesthesiae. The degree of sensory inhibition correlated positively with speed of movement and was comparable to the previously reported reduction in cortical somatosensory evoked potentials by movement, using suprathreshold stimuli. These results indicate that (i) movement inhibits tactile sensations of different qualities, (ii) such inhibition is velocity-dependent, and (iii) threshold sensations are amenable to central modulation short of their abolition. It is likely that the mechanisms of inhibition of exteroceptive inputs during movement are contingent upon the character of the sensory stimulus and the nature of the motor task.     

Thalamic and cortical contributions to neural plasticity after limb amputation

Little is known about the substrates for the large-scale shifts in the cortical representation produced by limb amputation. Subcortical changes likely contribute to the cortical remodeling, yet there is little data regarding the extent and pattern of reorganization in thalamus after such a massive deafferentation. Moreover, the relationship between changes in thalamus and in cortex after injuries of this nature is virtually unexplored. Multiunit microelectrode maps were made in the somatosensory thalamus and cortex of two monkeys that had long-standing, accidental forelimb amputations. In the deprived portion of the ventroposterior nucleus of the thalamus (VP), where stimulation to the hand would normally activate neurons, new receptive fields had emerged. At some recording sites within the deprived zone of VP, neurons responded to stimulation of the remaining stump of the arm and at other sites neurons responded to stimulation of both the stump and the face. This same overall pattern of reorganization was present in the deprived hand representation of cortical area 3b. Thus thalamic changes produced by limb amputation appear to be an important substrate of cortical reorganization. However, a decrease in the frequency of abnormal stump/face fields in area 3b compared with VP and a reduction in the size of the fields suggests that cortical mechanisms of plasticity may refine the information relayed from thalamus.     

Unexpected reorganization of somatosensory cortex in a raccoon with extensive forelimb loss

Electrophysiological recordings were made from primary somatosensory cortex in a raccoon that had suffered a traumatic amputation of the forearm some time prior to its capture. Neurons in the affected forepaw region of sensory cortex were not silent but responded to cutaneous or neuroma activation of the remaining forearm stump. In addition, cells at many sites were responsive to tactile stimulation of the glabrous skin of the hindpaw ipsilateral to the damage. This indicates that the cortical plasticity following peripheral nerve damage can occur over much larger regions of cortex than was previously thought. An unmasking of silent thalamocortical terminals is not likely to be the mechanism underlying this plasticity in the raccoon.     

Secondary tactile hypoesthesia: a novel type of pain-induced somatosensory plasticity in human subjects

Quantitative sensory testing revealed that pain induced by intracutaneous capsaicin injection elicited secondary hyperalgesia coexisting with secondary tactile hypoesthesia. Mapping the areas of altered mechanical sensations adjacent to the capsaicin injection disclosed that the area of secondary hyperalgesia was always nested in a larger area of secondary hypoesthesia easily detected as numbness by most subjects. Psychometric functions revealed a twofold rightward shift of tactile detection (hypoesthesia), which coexisted with a more than fourfold leftward shift of pricking pain detection (hyperalgesia) in the same skin area. As a mechanism we propose a functional switch at the spinal level based on C-fibre-induced primary afferent depolarisation resulting in presynaptic inhibition of low threshold mechanoreceptor input and an ensuing loss of tactile sensitivity.     

Motor performance benefits of matched limb imitation in prosthesis users

Our previous work demonstrated that the action encoding parietofrontal network, which is crucial in planning and executing motor tasks, is less active in prosthesis users who imitate movements of intact actors (mismatched limb) versus prosthesis users (matched limb). Such activation could have behavioral consequences in prosthesis users rehabilitating with intact therapists. The goal was to identify behavioral effects of matched versus mismatched limb action imitation in naïve users of prostheses. Intact subjects donned a specially adapted prosthetic device to simulate the wrist and forearm movement that transradial amputees experience. While electrogoniometry was recorded, non-amputated prosthesis users (NAPUs) observed and imitated demonstrations of a skillful motor task performed by either an intact actor or NAPU. We hypothesized that NAPUs would elicit less motion variability when performing matched versus mismatched imitation. Matched imitation resulted in a significant decrease in shoulder motion variability compared with mismatched imitation. The matched group also developed elbow motion patterns similar to the NAPU demonstrator, while the mismatched group attempted patterns similar to the intact demonstrator. This suggests a behavioral advantage to matched imitation when adapting to a prosthetic device, as it yielded more consistent movements and facilitated development of new motor patterns. Further, these results suggest that when prosthesis users are faced with the impossible task of imitating movements of an intact hand, they perform this action with greater variability and poorer technique. This work has implications on how prosthetic device operation is conveyed to persons with amputation as their clinical interactions often involve mismatched limb imitation.     

A model for prediction of failure in amputation of the lower limb

A logistic regression analysis of eighteen variables in eighty-three lower limb amputations was performed in order to predict stump failure. Five variables were identified as having a significant effect on the logistic model: Age had an inverse relation to failure rate (p less than 0.005). This effect was mediated through a subgroup of 23 patients who had had a vascular operation (p less than 0.02), as this group had a higher failure rate and were younger than those without previous vascular surgery. Furthermore, the surgical experience (p less than 0.005) was of major importance for stump failure. Experienced surgeons had a failure rate of 2% while less experienced had a rate of 29% (p less than 0.001). In addition, it was confirmed that the higher the skin perfusion pressure (p less than 0.05) and the amputation level, (p less than 0.05) the better the healing. A model including "skin perfusion pressure," "previous vascular surgery," "amputation level" and "surgical experience" had a good predictive capability with a misclassification rate of 0.08-0.11. Therefore it is suggested that a logistic model including these variables could be a helpful tool to predict the risk of stump failure.     

A Case of Nonisland Pedicled Foot Fillet Flap for Below-Knee Amputation Stump Wound: Treatment Option for Compartment Syndrome after Fibular Free Flap Surgery

Despite the frequent use of the fibular free flap, there have been no reports of severe compartment syndrome of the donor leg that necessitated limb amputation. A 66-yr-old man had a fibular osseous free flap transfer from the left leg to the mandible that was complicated by postoperative compartment syndrome. An extensive chronic leg wound resulted, which was treated with multiple debridements and finally with below-knee amputation. Successful coverage of the below-knee amputation stump was accomplished with a nonisland pedicled foot fillet flap. Various foot fillet flaps may be used acutely as a free or an island pedicled flap, but dissection of the vascular pedicle may be difficult in a chronically inflamed wound because of inflammation and adhesions to surrounding tissue. The nonisland pedicled foot fillet flap may be considered as a useful option for treatment of a chronically inflamed stump wound after below-knee amputation.

Graphical Abstract

相似文献   

Asymmetry in the emotional content of lateralised multimodal hallucinations following right thalamic stroke

The thalamus has been described as a "relay station" for sensory information from most sensory modalities projecting to cortical areas. Therefore injury to the thalamus may result in multimodal sensory and motor deficits. In the present study, a 61-year-old woman suffered a right thalamic cerebral vascular accident (CVA; as evidenced by a computerised tomography [CT] scan). Secondary to this incident, she complained of altered sensations across multiple sensory modalities, including olfactory, visual, auditory, tactile, temperature, and pain sensation. Interestingly, during recovery from the thalamic CVA, the patient reported hallucinations in all the modalities cited above. Multimodal dysaethesias (odd sensations) and hallucinations showed reliable laterality in the affective valence across modalities with positive associations within right hemispace and negative associations within left hemispace. Overall, the results support multimodal role of the thalamus and provide evidence for lateralisation of positive and negative affect within the right and left hemispheres respectively.