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Biomedical subjects

K H Mauritz

Publications and source records attributed to K H Mauritz.

At least 37 records · Page 2Linked to original sources
PubMed1994

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.

Adult↗
PubMed1994

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.

Adult↗
PubMed1994

Botulinum toxin treatment for lower limb extensor spasticity in chronic hemiparetic patients.

Twelve chronic hemiparetic outpatients with pronounced lower limb extensor spasticity were injected with 400 units of botulinum toxin A, EMG guided into the soleus, tibialis posterior, and both heads of the gastrocnemius muscles. Botulinum toxin A caused a definite reduction of plantar flexor spasticity, in 10 patients two weeks after the injection, as assessed by the Ashworth scale. Four of the patients were able to achieve active dorsiflexion of their affected ankle. Gait analysis including the measurement of vertical ground reaction forces showed a statistically significant (p < 0.01) improvement in velocity, stride length, stance symmetry, and the length of the force point of action under the affected foot. Qualitative improvements on the force diagrams indicated a better loading, advancement of the body, and push off of the affected limb in seven patients. Eight weeks after the injection the effects waned.

Adult↗
PubMed1994

Gait outcome in ambulatory hemiparetic patients after a 4-week comprehensive rehabilitation program and prognostic factors.

BACKGROUND AND PURPOSE: Although gait training is prominent in the rehabilitation of hemiparetic stroke patients, little is known about its outcome and prognostic factors in mildly affected patients. We therefore intended to assess gait in ambulatory stroke patients before and after a 4-week inpatient rehabilitation program based on the neurodevelopmental technique. METHODS: We measured vertical ground reaction forces by force plates in 148 stroke patients. Variables were stance durations, peak vertical ground reaction forces at heel strike (Fz1) and toe-off (Fz2), loading and deloading rates, time to Fz1, and time to Fz2. The absolute changes for both legs and symmetry outcome were calculated. In addition, we assessed maximal walking speed, walking endurance, stair climbing ability, and the Motricity Index. RESULTS: Stance duration, weight acceptance, push-off of both legs, and the stance duration symmetry improved independent of changes of gait velocity. The symmetry of the ground reaction forces did not improve. Results were even worse for Fz1 and the loading rate at the end of treatment. Sex, age, side of hemiparesis, motor strength, stroke interval, and sensory impairment had no influence on the outcome of symmetry. Functional performance did not improve considerably. CONCLUSIONS: The absolute changes of the ground reaction forces indicated better weight acceptance and push-off of both legs and thus confirmed the efficacy of the neurodevelopmental technique. The symmetry outcome and the functional performance at the end of treatment, however, challenge the efficacy of intensive rehabilitation therapy for 4 weeks in its attempts to restore physiological gait in these mildly affected patients.

Adolescent↗
PubMed1994

Quantitative analysis of rising from a chair in healthy and hemiparetic subjects.

In 15 healthy and 20 hemiparetic persons we studied standing-up by two force-plates. Phases before and after the seat-off, force distribution and centre of gravity displacement were assessed. The patients rose significantly slower. The force ratios after seat-off differed significantly between the groups (0.88 vs 0.68). Left/right hemiparetic patients put more weight on the affected limb in 18%/11% of the trials before seat-off, with its insufficient use after it mainly in the left patients. At seat-off, projection of the centre of gravity fell within the support area in hemiparetic patients, and 3 cm behind it in healthy subjects. With larger lateral displacement of the centre of gravity in the hemiparetic group, left hemiparetic patients mostly shifted their weight to the non-affected side and right hemiparetic patients to both sides. Weight distribution and mediolateral displacement of the centre of gravity in the left and right hemiparetic patients were considered.

Activities of Daily Living↗
PubMed1993

[The neurophysiological basis of exercise physical therapy in patients with central hemiparesis].

According to everyday experience in rehabilitation, stroke patients suffering from central hemiparesis physiotherapy is efficacious in reducing the degree of motor impairment. This paper describes the various therapeutic techniques used in the traditional physiotherapeutic concepts (Rood, Bobath, Brunnstrom, proprioceptive neuromuscular facilitation, Vojta) and their basic neurophysiological mechanisms, as far as they are known today. Furthermore, the significant role of treating impaired sensation and perception for movement execution is discussed and various therapeutic concepts (traditional sensibility training, methods according to Affolter and Perfetti, forced use) are described.

Cerebrovascular Disorders↗
PubMed1993

[A clinically applicable system for analysis of standing up using measurements of floor reaction forces].

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.

Biomechanical Phenomena↗
PubMed1989

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.

Electric Stimulation Therapy↗
PubMed1988

Visual and mechanical control of postural and kinetic tremor in cerebellar system disorders.

The influence of alterations in visual guidance and somaesthetic sensory inputs was studied in five patients with kinetic and postural tremor characteristic of cerebellar impairment. The patients performed wrist flexion-extension movements or movements about the shoulder with or without visual guidance. Different types of mechanical loads were applied to oppose the wrist movements. The tremor was greatest when the patients used visual cues to guide movements. Kinetic tremor was substantially suppressed during performance of similar movements that were not guided directly by vision. Viscous loads suppressed the tremor nearly linearly, whereas constant loads opposing extension enhanced the tremor. The postural tremor was not observed during isometric contractions. These results support the view that processing of visual information contributes to the impairment of movement in disorders with cerebellar-type tremor and that certain somaesthetic inputs can selectively influence the generation of postural tremor.

Adult↗
PubMed1986

Premotor cortex of the rhesus monkey: neuronal activity in anticipation of predictable environmental events.

The activity of premotor cortex neurons was studied in macaque monkeys that were operantly conditioned to perform a visually guided motor task. The monkeys were given a visuospatial instruction stimulus (IS) that provided the target for a limb movement, but the monkey was not allowed to execute the movement until the later presentation of a trigger stimulus (TS). The IS was sometimes removed or the target changed during the interval between the IS and TS. Certain neurons became active before the IS, appearing to anticipate its location or time of occurrence, some of these and other neurons increased or decreased their discharge prior to a possible change in the IS, and other cells showed neuronal modulation that preceded the TS. The properties of some of these neurons were examined when the timing of the behavior-guiding visual signals or their probability of occurrence was made less predictable. In general, the neuronal activity described here was strongly influenced by changes in event predictability. These findings suggest that neuronal activity within the premotor cortex reflects the anticipation of predictable environmental events.

Animals↗
PubMed1985

Set-related neuronal activity in the premotor cortex of rhesus monkeys: effects of changes in motor set.

Previous studies have suggested that the premotor cortex plays a role in motor preparation. We have tested this hypothesis in macaque monkeys by examining neuronal activity during an enforced, 1.5-3.0 s delay period between the presentation of an instruction for movement and the onset of that movement. Two targets for movement were available to the monkey, one on the left and one on the right. Illumination of one of the targets served as the instruction for a forelimb movement. It is known that there are cells in the premotor cortex that have directionally specific, sustained activity increases or decreases following such instructions. If the premotor cortex is involved in the preparation for movement in a particular direction, then changing the target from one to the opposite side during the delay period should lead to a pronounced change in sustained neuronal activity. Further, removing the instruction, while still requiring movement to the target, should have little or no sustained effect. Seventy cells showed the predicted activity patterns, thus supporting the view that the premotor cortex plays a role in motor preparation.

Animals↗
PubMed1985

Chronic transformation of muscle in spasticity: a peripheral contribution to increased tone.

Mechanical properties of relaxed lower leg muscles were assessed by torque measurements during imposed constant velocity dorsiflexion-plantarflexion cycles. At low angular velocities, they exhibited an elastic and an energy-consuming, velocity-independent (plastic) resistance. In most patients with long-standing spasticity, both of these were enhanced. The results support the hypothesis of secondary structural changes of muscles in spasticity.

Adult↗
PubMed1985

Motor control in humans with large-fiber sensory neuropathy.

Upper limb motor control was evaluated in a series of patients with a large-fiber sensory neuropathy associated with impaired position, vibration and cutaneous sensation and absence of deep tendon reflexes. Muscular strength was normal or only minimally affected. In studies of wrist movement it was found that both postural maintenance and accuracy of wrist displacement were heavily dependent on visual guidance. Without vision the limb would drift in almost random directions, and during intended movements both the trajectory and movement end-point were abnormal. The defects in posture and voluntary movement control were reflected in the inability of patients to maintain consistent levels or emit consistent patterns of muscle activity. It is concluded that whereas central motor commands are sufficient to initiate movements proprioceptive afferent inputs are important for accurate postural maintenance and the fine control of movement.

Adult↗
PubMed1984

Motor deficits in patients with large-fiber sensory neuropathy.

The issue of whether brain signals in the absence of peripheral feedback are sufficient to specify accurate movement was evaluated by studying motor performance in patients with loss of somesthetic afferent input as a result of acquired large-fiber sensory neuropathy. With visual guidance, movements and postures were impaired relatively little, but when visual guidance was unavailable, the patients exhibited postural drift and gross inaccuracy of movement. Impairments were more apparent for smaller (3 degrees) than for larger (15 degrees) movements. Previous studies that have failed to show major motor impairments in deafferented subjects examined movements involving rather large joint displacements, and this may have been a factor in the failure of these studies to reveal severe deficits. The present results demonstrate a critical role for somesthetic feedback in regulating centrally generated levels of motor output and show that central motor programs deprived of such feedback are unable to subserve accurate motor control.

Afferent Pathways↗