Search

Summary: In clinical practice, signs of exaggerated tendon tap reflexes associated with muscle hypertonia are generally thought to be responsible for spastic movement disorders. Most antispastic treatments are, therefore, directed at the reduction of reflex activity. In recent years, however, researchers have noticed a discrepancy between spasticity as measured in the clinic and functional spastic movement disorders, which is primarily due to the different roles of reflexes in passive and active states, respectively. We now know that central motor lesions are associated with loss of supraspinal drive and defective use of afferent input with impaired behaviour of short-latency and long-latency reflexes. These changes lead to paresis and maladaptation of the movement pattern. Secondary changes in mechanical muscle fibre, collagen tissue, and tendon properties (eg, loss of sarcomeres, subclinical contractures) result in spastic muscle tone, which in part compensates for paresis and allows functional movements on a simpler level of organisation. Antispastic drugs can accentuate paresis and therefore should be applied with caution in mobile patients. [Copyright &y& Elsevier]

Abstract: Objective: Responses to afferent input during locomotion are organized at the spinal level but modulated by supraspinal centers. The study aim was to examine whether supraspinal influences affect the behavior of complex electromyographic (EMG) responses to single limb perturbations during walking. Methods: Subjects with motor-complete (MCSCI), motor-incomplete spinal cord injury (MISCI), and non-disabled (ND) subjects participated. Hip or knee joint trajectory was briefly arrested by a robotic device at early or late swing phase. EMG responses from muscles of both legs were analyzed. Results: Perturbation-induced EMG responses of spinal cord injured and ND individuals were similar in basic structure, with the exception that tibialis anterior onset times were delayed for SCI subjects. Across all groups, perturbations in late swing (i.e., near the swing-to-stance transition) were associated with shorter muscle onset times and higher EMG amplitudes. Knee perturbations were associated with shorter muscle response onset times, while hip perturbations elicited higher response amplitudes. EMG responses were also evoked in muscles contralateral to the perturbation. Conclusions: These data indicate that neuronal circuits within the spinal cord deprived of normal supraspinal input respond to swing phase perturbations in a manner that is similar to that of the intact spinal cord. Significance: The adult human spinal cord is capable of generating complex, phase-appropriate responses much as has been observed in studies of human infants and in spinal animals. [Copyright &y& Elsevier]

Abstract: Wirz M, van Hedel HJ, Rupp R, Curt A, Dietz V. Muscle force and gait performance: relationships after spinal cord injury. Objectives: To relate locomotor function improvement, within the first 6 months after spinal cord injury (SCI), to an increase in Lower Extremity Motor Score (LEMS) and to assess the extent to which the level of lesion influenced the outcome of ambulatory capacity. Design: Longitudinal and cross-sectional analyses. Setting: Seven SCI rehabilitation centers. Participants: Patients (N=178) were analyzed longitudinally (group A, motor complete; group B, motor incomplete; nonwalking or group C, motor incomplete and able to stand). The cross-sectional analysis included 86 patients (paraplegic, n=46; tetraplegic, n=40; group 1 with limited and group 2 with unrestricted walking function 6mo after SCI). Interventions: Not applicable. Main Outcome Measures: Walking Index for Spinal Cord Injury (WISCI), gait speed, and LEMS. Results: For group A, 24.8% of the patients improved in LEMS (median range, 0–10) and 7.7% in walking function (WISCI median range, 0–8; mean gait speed range, 0 to .14±.10m/s). For group B, LEMS improved in 93.5% of the patients (median range, 14–28) and walking function in 84.8% of the patients (WISCI median range, 0–10; mean gait speed range, 0 to .41±.45m/s) (P<.001). For group C, LEMS and walking function improved in 100% of the patients (LEMS median range, 29–41; WISCI median range, 8–16; mean gait speed range, .36±.29m/s to .88±.44m/s) (P=.001). In groups B and C, the improvement of walking function was greater than in LEMS. The cross-sectional analysis showed that group 1 patients with tetraplegia had more muscle strength (median LEMS, 31.5), and equal walking function (WISCI, 8; walking speed, 0.4±0.3m/s) compared with patients with paraplegia (LEMS, 23; P<.01; WISCI, 12; P=0.6; speed, 0.4±0.3m/s; P=.68). In group 2, patients with tetraplegia had slightly more strength (LEMS, 48) and equal walking function (WISCI, 20; walking speed, 1.4±0.4m/s) compared with patients with paraplegia (LEMS, 45; P<.05; WISCI, 20; P=1.0; speed, 1.4±0.3m/s; P=.89). Conclusions: An improvement in locomotor function does not always reflect an increase in LEMS, and LEMS improvement is not necessarily associated with improved locomotor function. LEMS and ambulatory capacity are differently associated in patients with tetra- and paraplegia. Functional tests seem to complement clinical assessment. [Copyright &y& Elsevier]

Summary: During the past few years, several approaches to spinal-cord repair have been successfully established in animal models. For their use in trials of spinal-cord injury (SCI) in human beings, specific difficulties that affect the success of clinical trials have to be recognised. First, transection of the spinal cord is commonly applied in animal models, whereas contusion, which generally leads to injury in two to three segments, represents the typical injury mechanism in human beings. Second, the quadrupedal organisation of locomotion in animals and the more complex autonomic functions in human beings, challenge translation of animal behaviour into recovery from SCI in people. Third, the extensive damage of motor neurons and roots associated with spinal-cord contusion is not addressed in current translational studies. This damage has direct implications for rehabilitation strategies and functional outcome. Fourth, there is increasing evidence for a degradation of neuronal function below the level of the lesion in chronic complete SCI. The relevance of this degradation for a regeneration-inducing treatment needs to be investigated. Fifth, the prerequisites to enable appropriate reconnection of regenerating tract fibres in a postacute stage have still to be established. [Copyright &y& Elsevier]

Examines the hypothesis that during locomotion, corticospinal excitation of upper limb motoneurons is mediate indirectly, via propriospinal neurons in the cervical spinal cord. Task-dependent neuronal linkage of cervical and thoraco-lumbar propriospinal circuits controlling leg and arm movements during human locomotor activities; Persistence of movement control.

In four eggs and four chicks of the North Island brown kiwi (Apteryx mantelli) we measured pre- and postnatal oxygen consumption rate (VO2) daily from day (d)−75 (prior to hatching) until d+25 (after hatching). The increase of embryonic VO2 reaches a plateau phase between d−22 and d−5 (0.113 ml O2/g/h=59.6% of allometrically expected value of a typical 416-g egg). Mean total O2 uptake per egg (43.01 l O2) corresponds to an energy turnover rate of 2.04 kJ/g during embryonic development. This is nearly identical to the expected value for all birds (2.00±0.8 kJ/g). Hence, the kiwi neither ‘gained nor lost energy’ (Calder, 1979.Biosci. 8, 461–467) by its extreme prolongation of incubation time; it is as efficient as other avian embryos. The kiwi embryo expends only approximately 17% (847 kJ) of the energy originally stored in the egg (4942 kJ). Forty-eight percent of the egg''s initial yolk mass can be found as spare yolk in the hatchling and can serve as the chick''s sole source of energy and substrate for tissue production for up to at least 17 days after hatching. [Copyright &y& Elsevier]

Summary: Background: Arm hemiparesis secondary to stroke is common and disabling. We aimed to assess whether robotic training of an affected arm with ARMin—an exoskeleton robot that allows task-specific training in three dimensions—reduces motor impairment more effectively than does conventional therapy. Methods: In a prospective, multicentre, parallel-group randomised trial, we enrolled patients who had had motor impairment for more than 6 months and moderate-to-severe arm paresis after a cerebrovascular accident who met our eligibility criteria from four centres in Switzerland. Eligible patients were randomly assigned (1:1) to receive robotic or conventional therapy using a centre-stratified randomisation procedure. For both groups, therapy was given for at least 45 min three times a week for 8 weeks (total 24 sessions). The primary outcome was change in score on the arm (upper extremity) section of the Fugl-Meyer assessment (FMA-UE). Assessors tested patients immediately before therapy, after 4 weeks of therapy, at the end of therapy, and 16 weeks and 34 weeks after start of therapy. Assessors were masked to treatment allocation, but patients, therapists, and data analysts were unmasked. Analyses were by modified intention to treat. This study is registered with ClinicalTrials.gov, number NCT00719433. Findings: Between May 4, 2009, and Sept 3, 2012, 143 individuals were tested for eligibility, of whom 77 were eligible and agreed to participate. 38 patients assigned to robotic therapy and 35 assigned to conventional therapy were included in analyses. Patients assigned to robotic therapy had significantly greater improvements in motor function in the affected arm over the course of the study as measured by FMA-UE than did those assigned to conventional therapy (F=4·1, p=0·041; mean difference in score 0·78 points, 95% CI 0·03–1·53). No serious adverse events related to the study occurred. Interpretation: Neurorehabilitation therapy including task-oriented training with an exoskeleton robot can enhance improvement of motor function in a chronically impaired paretic arm after stroke more effectively than conventional therapy. However, the absolute difference between effects of robotic and conventional therapy in our study was small and of weak significance, which leaves the clinical relevance in question. Funding: Swiss National Science Foundation and Bangerter-Rhyner Stiftung. [Copyright &y& Elsevier]