Motor learning after recovery from hemiparesis.

Twenty patients who had almost completely recovered from hemiparesis following unilateral cerebrovascular accident and 16 control subjects had to perform motor learning tasks including a three-dimensional motor problem and two standard precision tests. The ability of hemiparetic patients to solve simple spatial-motor problems and to gain by training was preserved with limitations concerning high precision control. However, hemiparetic patients had a higher demand for time and corrections, as well as a reduced consistency of performance. Thus recovery from hemiparesis was accompanied by reduced skillfulness and automaticity of motor control.

Control mechanisms for restoring posture and movements in paraplegics.

The control mechanisms underlying undisturbed movements were analysed in two series of experiments: (1) normal physiological responses were investigated in neurologically intact subjects; (2) an artificial motor control system for paraplegic patients using functional neuromuscular stimulation (FNS) of the paralysed leg muscles was developed and tested. In both series of experiments standing-up from a chair and sitting-down were studied. A three-link model of the human body was used for recording and processing biomechanical data. In 5 normal subjects ground reaction forces and the surface electromyogram of different leg muscles were also recorded. Basic physiological aspects of FNS such as muscle force regulation and fatigue could be documented. For the standing-up and sitting-down experiments in 2 paraplegic patients the gluteal and quadriceps muscles were stimulated. The best results were achieved with a combination of open-loop and closed-loop stimulation with position and velocity feedback. The importance of feedforward and feedback control during undisturbed movements is discussed for natural and artificial motor control systems. It is concluded that the control of knee joint angle during standing-up and sitting-down represents an unstable system which cannot be controlled open-loop only. Different aspects of sensory feedback including the regulated variables, gain and stability of the system are discussed on the basis of the experimental data and the literature.

Motor rehabilitation after traumatic brain injury and stroke - Advances in assessment and therapy.

A long-term goal in motor rehabilitation is that treatment is not selected on the basis of 'schools of thought', but rather, based on knowledge about efficacy and effectiveness of specific interventions for specific situations (e.g. functional syndromes). Motor dysfunction after stroke or TBI can be caused by many different functional syndromes such as paresis, ataxia, deafferentaion, visuo-perceptual deficits, or apraxia. Examples are provided showing that theory-based analysis of motor behavior makes it possible to describe 'syndrome-specific motor deficits'. Its potential implications for motor rehabilitation are that our understanding of altered motor behavior as well as specific therapeutic approaches might be promoted. A methodological prerequisite for clinical trials in rehabilitation is knowledge about test properties of assessment tools in follow-up situations such as test-retest reliability and responsiveness to change. Test-retest reliability assesses whether a test can produce stable measures with test repetition, while sensitivity to change reflects whether a test detects changes that occur over time. Exemplifying these considerations, a reliability and validity study of a kinematic arm movement analysis is summarized. In terms of new therapeutic developments, two examples of clinical therapeutic studies are provided assessing the efficacy of specific inter-ventions for specific situations in arm and gait rehabilitation: the Arm Ability Training for high functioning hemiparetic stroke and TBI patients, and the treadmill training for non-ambulatory hemiparetic patients. In addition, a new technical development, a machine-controlled gait trainer ist introduced.

Brain activation pattern as assessed with multi-modal EEG analysis predict motor recovery among stroke patients with mild arm paresis who receive the Arm Ability Training.

PURPOSE: Receiving the Arm Ability Training for three weeks improves motor function among stroke patients with mild arm paresis. There is, however, a considerable variability in recovery among patients receiving the Arm Ability Training. The study investigated whether intersubject differences in movement-related electric brain activity explain the variability in motor recovery. METHODS: In a sample of 9 patients receiving the Arm Ability Training both motor performance using a standardised arm function test (TEMPA) and movement-related electric brain activity, i.e. slow cortical potentials (DC) as well as event-related desynchronisation of alpha (alpha-ERD) and beta activity (beta-ERD), were assessed before the Arm Ability Training was started. Stepwise multiple regression was used to establish the best predictive model for motor improvement scores (TEMPA difference from pre to post test three weeks later). RESULTS: Stepwise multiple regression indicated that electric brain activity during movement preparation explained the variance of motor improvement scores completely. Further, electric brain activity during movement as well as baseline motor performance accounted each for 50% of the variance of motor improvement scores. CONCLUSIONS: Activation of sensorimotor areas during movement preparation and deactivation of other cortical areas during movement execution seem to be factors that predict a favourable outcome after training.

Stiffness regulation provided by short-latency reflexes in human triceps surae muscles.

The triceps surae muscles of normal human subjects were rapidly stretched and released by rotating the foot about the ankle joint with a torque motor. Following the initial intrinsic resistance, the yielding observed in incremental force records was more rapid for stretch than for release responses. Short-latency EMG responses elicited by stretch recruit force, to compensate for the yielding and to maintain the total (intrinsic plus reflex) resistance constant as the prior force level changes.

Motor aspects of cue-related neuronal activity in premotor cortex of the rhesus monkey.

Neurons in the premotor cortex of rhesus monkeys were studied under two conditions: (1) visuospatial cues were given to guide the amplitude, direction, and onset time of forearm movements or (2) physically identical visual cues were given when reward was contingent on withholding movement. Neurons with sustained activity following the cues were preferentially active when the cues triggered a movement. Thus, activity of certain neurons in this cortical field is linked to motor set, i.e. intention to make a movement in response to the cue, rather than the visual cue per se.

Short-term electrical stimulation enhances the effectiveness of Botulinum toxin in the treatment of lower limb spasticity in hemiparetic patients.

The study tested the spasmolytic effect of Botulinum toxin A in two groups of hemiparetic patients with lower limb spasticity: in the first group (n = 5) 2000 U Dysport were injected into the soleus, tibialis posterior and both heads of gastrocnemius muscles alone; the second (n = 5) received additional repetitive alternating electrical stimulation of M. tibialis anterior and plantar flexors for 30 min six times per day during the 3 days following the injection. Muscle tone, rated by the Ashworth spasticity score, and gait analysis including recording of vertical ground reaction forces, were assessed before and 4 weeks after injection. The combined treatment proved to be more effective with respect to the clinically assessed reduction of muscle tone, gait velocity, stride length, stance- and swing-symmetry (P < 0.05). The result is discussed with reference to animal experiments demonstrating enhanced toxin uptake and accelerated onset of its paralytic effect by electrical stimulation.

Cyclist's palsy: Neurological and EMG study in 4 cases with distal ulnar lesions .

Four cases of cyclist's palsy -- a distal compression syndrome of the ulnar nerve which can develop after long cycling tours -- are described. In two patients extensive neurological and electromyographic (EMG) studies were performed in order to document the degree and time course of recovery of the motor and sensory deficiencies. In contrast to either EMG-studies it could be demonstrated that not only the deep motor branch of the ulnar nerve is involved, but also that a severe lesion of the superficial branch supplying the skin of the 4th and 5th finger can occur, as indicated by a complete loss of the orthodromic sensory action potential recorded above the ulnar nerve in both cases. The results furthermore show that a functionally significant paresis of the hand muscles can persist for several months. The pathogenesis and some practical implications will be discussed.

Repetitive training of isolated movements improves the outcome of motor rehabilitation of the centrally paretic hand.

The effect of a standardized training on movements of the affected hand has been studied in 27 hemiparetic patients using a multiple baseline approach across individuals. The training consisted of repetitive hand and finger flexions and extensions against various loads and was carried out twice daily during 15-min periods. Grip strength (p < 0.006), peak force of isometric hand extensions (p < 0.05), peak acceleration (p < 0.05) of isotonic hand extensions as well as contraction velocities as indicators of motor performance significantly improved during the training period. In contrast to the standardized training of hand and finger movements, therapeutic strategies following the Bobath concept aim at reducing enhanced muscle tone without reinforcing the activity in centrally paretic distal muscle groups directly. Patients undergoing this treatment approach alone did not experience a significant improvement in the motor capacity of the hand. Therefore, the results of the present study emphasize the importance of frequent movement repetition for the motor rehabilitation of the centrally paretic hand and challenge conventional physiotherapeutic strategies that focus on spasticity reduction instead of early initiation of active movements.

Syndrome-specific deficits of performance and effects of practice on arm movements with deafferentation due to posterior thalamic lesion.

Aiming and tapping movements were analysed repeatedly over a three-week period in a patient who was hemideafferented due to an ischaemic posterior thalamic lesion. Contrasting behaviour observed in six healthy subjects, nine hemiparetic patients and one patient with hemianopic stroke, allowed the determination of behavioural deficits related to deafferentation. Finger tapping was not impaired specifically and did not improve with practice in the deafferented patient. When aiming movements were investigated, accuracy of the first, largely preprogrammed, phase of movement and timing of the late homing-in phase were impaired specifically in the deafferented patient. Practice led to a step-like change in preprogramming amplitude of the ballistic movement component, a gradual improvement of temporal efficiency of the early movement phase and a more marked improvement of the homing-in phase. Qualitatively comparable but quantitatively less marked effects of practice were documented for hemiparetic patients. These results demonstrated that deafferentation affects preprogrammed aspects of movement and those influenced by current control and that motor learning is possible with central deafferentation, even for aspects of performance that are impaired specifically. It is postulated that motor learning was mediated by changes in strategy (motor programming) and improved efficiency of intact motor control processes (visuomotor control).

Restoration of standing, weight-shift and gait by multichannel electrical stimulation in hemiparetic patients.

The effects of multichannel electrical stimulation of standing, weight-shift and gait were studied in hemiparetic patients. The ground reaction forces under both feet were assessed by two force plates during standing and weight-shift of 11 patients with and without three-channel stimulation of the pelvic and knee muscles. Stance symmetry and rate of the weight-shift significantly improved (p = 0.05) for 11.4% and 50.8% respectively during the stimulation. The gait of three hemiparetic patients was treated by adaptable, individually fitted four-channel stimulation. Besides peroneal nerve, knee extensor and flexor, hip extensor and abductor muscles, a shoulder-arm stimulation was introduced to elevate a depressed shoulder, initiate arm swing and erect the trunk. Gait parameters including symmetry improved consistently after the 25 stimulation sessions: velocity 33%, cadence 5%, stride length 26%, stance symmetry ratio from 0.62 to 0.97. Moreover the gait pattern was restored in all patients. The study investigated a possibility of neurophysiologically based treatment by the stimulation of standing, weight-shift and gait.

Gait function in spastic hemiparetic patients walking barefoot, with firm shoes, and with ankle-foot orthosis.

The purpose of the study was to investigate the effect of firm shoes and a particular type of a frequently prescribed ankle-foot orthosis in Germany, the Valens calliper, on functional gait parameters in hemiparetic patients with marked extensor spasticity and corresponding heel-strike problems. Cycle times, vertical ground reaction forces, trajectories of the centre of pressure (gait line) under the soles and the mode of initial contact were assessed in 19 hemiparetic patients walking barefoot, with firm shoes and the orthosis. With the shoes, significant improvements (p < 0.006) were observed for: walking velocity, stride length, initial double stance duration and gait line of the non-affected foot. The pattern of the vertical force diagram improved qualitatively in six patients. With the orthosis the following variables showed an even more marked improvement (p < 0.006): walking velocity, cadence, stride length, and gait line of both the affected and non-affected foot. Fourteen patients became rear-foot strikers and the vertical force pattern further improved in six patients. It is concluded that the ankle-foot orthosis (more than the shoes) provide a useful support in the early rehabilitation of hemiparetic patients with marked spasticity.

[Effect of music on gait symmetry of stroke patients on a treadmill]. / Die Wirkung von Musik auf die Symmetrie des Gehens von Schlaganfallpatienten auf dem Laufband.

The influence of rhythmic music on gait symmetry was investigated in 12 healthy subjects and 12 stroke patients with mild leg paresis walking on the treadmill. For the measurement, new insoles containing air-filled chambers developed by W.O.M were used. Symmetry deviation was determined as the mean signless difference between left and right swing phases of some 100 strides. In 6 patients, the symmetry deviation decreased by more than 1% of the stride duration some 40 steps after switching on the music. The improvement correlated with the initial symmetry (r2 = 0.61) exclusively in the healthy controls. In order to differentiate individual predictors of the improvement in symmetry, such as cognitive performance in terms of recognizing the beat of the music and the motor performance in terms of synchronizing the movements of the legs to the music, we analysed foot tapping with the patient in the seated position. For both patients and healthy subjects, the mean time difference between beat and foot movement was less than +/-1/32 beat. Individual scatter of mean 8% correspond in the case of healthy subjects to the figures found in the literature for finger movements, and the corresponding figures for the patients are more than twice this. The individual synchronisation performance during walking to music correlates to that during foot tapping (r2 = 0.47) exclusively in the group of healthy controls.

[A clinically applicable system for analysis of standing up using measurements of floor reaction forces]. / Klinisch einsetzbares System zur Analyse des Aufstehens mittels Messung der Bodenreaktionskräfte.

A system for clinical analysis of sit-to-stand transfer using two force plates is presented. Distinct time-events and phases are estimated. Illustrative parameters are also determined, such as the distribution of the vertical ground reaction forces, displacement of the center of gravity in the sagittal and frontal planes, and a comparison of the displacement of the center of gravity and the center of pressure. These parameters indicate a symmetrical raising while keeping the middle of the body. Future applications include the validation of therapy, biofeedback and the control of closed-loop FES.

Gait training in hemiparetic stroke patients.

The major goal of neurological rehabilitation includes restoration of mobility. In mobility we include walking, standing up, sitting down, weight shifting from one leg to the other, turning around, initiating and stopping locomotion, as well as climbing stairs. The therapeutic procedures include: different concepts of physiotherapy stressing different features, like force exercise, reduction of spasticity, gait symmetry, utilization of equilibrium reflexes, stepping automation, endurance training, repetition of rhythmic movements etc. The spectrum of available therapies was recently widened by treadmill training with partial body-weight support, gait machines, by functional electrical stimulation (FES), locomotor pharmacotherapy, selective reduction of spasticity by botulinum-toxin (BTX) injections, acoustic and visual cuing and biofeedback. These methods pertaining to gait improvement will also be described. Technical aids should be prescribed earlier, since their costs are usually almost negligible if compared to the costs for a prolonged inpatient treatment. Treadmill training with partial body-weight support in a parachute harness allows early training of postural reactions and stepping. The gait pattern can be considerably improved by FES. A new approach includes mechanical and computer controlled training machines to enable the repetitive training of complex gait cycles without overstressing therapists. First results demonstrate positive effects beyond the classical retraining procedures.