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Biomedical subjects

M Bacher

Publications and source records attributed to M Bacher.

At least 91 records · Page 5Linked to original sources
PubMed1989

[Secondary prevention of mesial bite in infants with maxillary clefts by correcting early deciduous prenormal incisors].

A new application of the inclined plane principle for the management of mesial bite in a child aged 14 months is reported. It was of interest to note that, inspite of the presence of Robin's sequence associated with cleft palate and postnormal mandible and inspite of posteriorly directed stresses on the mandible generated by sucking, the deciduous incisors were prenormal at the very time of their eruption. In light of the growth arresting effect of palatal clefts the authors emphasize the importance of regular orthodontic care in cleft patients beyond early orthodontic treatment throughout dental development in order to prevent the occurrence of developmental anomalies.

Cleft Palate↗
PubMed1988

Twenty-four-hour tremor recordings in the evaluation of the treatment of Parkinson's disease.

A new method of prolonged recording of EMG provides a good estimate of spontaneous and induced diurnal variations in resting tremor in Parkinson's disease. It provides a record and a measure of the effects of treatment. Tremor intensity shows considerable variations even over short periods of time. Therefore short-term measurements of tremor are unhelpful. Long-term recordings agree better with the patient's assessment than with the clinical rating score. Repeated recordings over a similar 10-h period on 3 consecutive days in one patients showed fairly constant measures of occurrence and intensity of tremor. In contrast to accelerometer measurements of tremor, artefacts caused by movements and general activity of the patient do not materially interfere with tremor evaluation using surface EMG.

Adult↗
PubMed1987

Medium and long latency EMG responses in leg muscles: Parkinson's disease.

Short, medium, and long latency EMG responses to muscle stretch from triceps surae and anterior tibialis muscles were recorded in normals and in 33 patients with Parkinson's disease. The latencies of all EMG responses except short latency were normal in patients with Parkinson's disease. The integrals of the medium latency responses in the stretched triceps surae muscle were significantly increased in patients. This result indicates a modulatory influence of the basal ganglia on medium latency EMG responses.

Adult↗
PubMed1987

Long latency EMG responses in hand and leg muscles: cerebellar disorders.

Electromyographic responses to stretches of hand muscles (first dorsal interosseus) and leg muscles (triceps surae, tibialis anterior) were investigated in patients with cerebellar disorders of different locations. Stimuli consisted of short dorsiflexions of the index finger during background force and in tilting (toe up) of a movable platform on which the subject stood. The most important findings were increased long latency responses in upper and lower extremities. For hand muscles it was the late part of the long latency complex, which was increased. For leg muscles it was the long latency response in the anterior tibialis muscle, the antagonist of the stretched triceps surae. The medium latency response in the triceps surae was unaffected. Latencies of the early segmental reflexes and the long latency responses were normal except for cases with peripheral neuropathy (moderate increase in latency of all EMG responses) and diseases affecting both the peripheral nerves and the dorsal columns (for example Friedreich's ataxia). The latter leads to a pronounced delay of the short latency response and a massive delay of the long latency complex in the first dorsal interosseus and of the long latency response in the anterior tibialis muscle.

Atrophy↗
PubMed1986

Development of postural control in children: short-, medium-, and long latency EMG responses of leg muscles after perturbation of stance.

Short (SL), medium (ML), and long (LL) latency EMG responses of leg muscles were recorded after perturbation of stance by means of a sudden toe-up tilt of a movable platform. 56 healthy children varying in age between 14 months and 15 years were investigated. All three responses were present when children were able to stand on the recording platform. The SL-response in the triceps surae muscle, which corresponds to the mono- and oligo-synaptic spinal stretch reflex, showed a decreasing latency up to the age of 5 years. This reflects the increasing peripheral nerve conduction velocity. The ML-response in the triceps surae muscle, which as the SL-response has no stabilizing effect in this experiment, showed somewhat delayed maturational changes. The LL-response in the relaxed anterior tibial muscle helps to restore upright posture even in the youngest children. Its maturational changes in terms of latency by far exceed the range that can be explained by the increase of peripheral and spinal conduction velocities. Its mechanisms of maturation, besides the biophysical optimalization of a polysynaptic network, may include learning in terms of selecting the shortest pathways by way of synaptic potentiation within structures involved in the supposedly transcortical pathway of the LL-response. Qualitative observations made during the trials showed that the pattern of postural adaptation changed with age, suggesting the development of additional intersegmental mechanisms.

Adolescent↗
PubMed1986

Role of visual and static vestibular influences on dynamic posture control.

Postural stabilization in altered visual and vestibular conditions was investigated in humans subjected to fast transient disturbances and during sinusoidal movement of the standing support. Visual inputs were varied by applying stroboscopic illumination, stabilizing the visual surround in respect to head movements, inducing apparent body movement in pitch by continuously moving stripe patterns up or down and by eye closure. Static vestibular input was modified by bending the head forwards or backwards, or to the right or left shoulder (eyes closed). Neither biomechanical parameters of standing nor EMG responses of the anterior tibial and triceps surae muscles were modified by the different visual and vestibular conditions during fast transient (80 degrees/s) platform movements 4 degrees toe-up. Continuous regulation of upright stance during sinusoidal movements (1 Hz, 0.3 Hz), however, clearly depended on the different modifications of visual and vestibular inputs. Fast transient disturbances are easily compensated in a reflex-like manner independent of visual and vestibular feedback. Continuous regulation of upright posture during slow disturbances, however, clearly depends on the evaluation of afferent information from the visual, vestibular, and proprioceptive systems.

Adolescent↗
PubMed1984

Early stabilization of human posture after a sudden disturbance: influence of rate and amplitude of displacement.

The functional role of short-, medium- and long-latency responses for the maintenance of upright posture was investigated in twenty healthy subjects standing on a platform which could be rotated in pitch around the subject's ankle joints. Tilting the platform toe-up evokes a stretch reflex in the triceps surae muscle (TS, latency 55-65 ms) and at higher speeds and amplitudes of platform displacement a medium-latency response (latency 108-123 ms). Both responses functionally destabilize posture, since they enforce the induced backward displacement of the body. Compensation of body displacement in this situation is achieved by a long-latency EMG response in the anterior tibial muscle (TA 130-145 ms). Platform movement toe-down elicits a rather small medium-latency response in TA (103-118 ms), but no short-latency response. A late compensatory response occurs in the triceps surae muscle (latency 139-170 ms). The mean latency of the late antagonistic EMG response was significantly shorter than that of a voluntary movement triggered by a somatosensory stimulus. Integrals of rectified EMG responses from the two muscles were linearly related to the amplitude and to a smaller degree to the velocity of platform displacement. The slope of this function (gain) varied depending on the direction of ankle displacement and the functional importance of the subsequent EMG responses. Destabilizing short- and medium-latency responses of the stretched muscle had a lower gain relative to amplitude than the late stabilizing response of the antagonist. This functionally adaptive modulation of gain was not seen in relation to the rate of platform displacement.

Adult↗
PubMed1984

Improvement of ataxia in alcoholic cerebellar atrophy through alcohol abstinence.

Postural instability was measured and short, medium and long latency EMG responses to angular displacement of the ankle were recorded from leg muscles in a group of 17 alcoholics who presented with clinical signs of cerebellar atrophy of the anterior lobe. Recordings were performed twice (average interval 18.5 months) to determine the effects of continued drinking versus abstinence on the signs of the cerebellar damage. Patients who were abstinent (n = 11) exhibited a significant, sometimes dramatic decrease of body sway whereas patients who continued drinking (n = 6) showed increased body sway when the eyes were closed. Short and medium latency EMG responses were unaltered in both groups of patients. The integral of the long latency response of the antagonist tended to increase with continued abuse and to decrease in abstinent patients.

Adult↗
PubMed1984

The significance of delayed long-loop responses to ankle displacement for the diagnosis of multiple sclerosis.

The present study compares the results of sensory evoked potentials after stimulation of the tibial nerve with measurements of short (M1), medium (M2) and long-loop latency (M3) responses of leg muscles in 42 patients suffering from multiple sclerosis. EMG responses were elicited by a movable platform which was tilted in pitch toe-up around the subject's ankle joint. The short latency response of the triceps surae muscle was nearly always normal in latency. The M2 response was lacking in about 30% of the patients and 10% of normals. The long latency response (M3) in the antagonistic anterior tibial muscle was significantly delayed (beyond 162 msec = AM + 2.5 S) in 69% of the patients. The delayed M3 response was found to indicate demyelination as reliably as the delayed somatosensory evoked potential (66% of the patients). The frequency of coincident results in the entire group was 86%. Additional information is gained in cases where SEPs are normal, but M3 is delayed (7%). Furthermore, patients lacking P40 of the SEP still exhibit M3 responses, the latency of which may be measured (24%). The results favour the assumption that M3 is mediated by a supraspinal pathway.

Ankle↗
PubMed1984

Quantification of postural sway in normals and patients with cerebellar diseases.

Posturography was performed in 41 patients with cerebellar diseases by means of a force measuring platform using an on-line computer program which calculated sway path, sway area, antero-posterior and lateral sway components and the amount of visual stabilization. Postural ataxia was quantitatively studied in 8 patients with spinal ataxia (Friedreich's), 6 patients with vestibulocerebellar lesions, 11 patients with anterior lobe atrophy, 7 patients with hemispheral cerebellar lesions, and 9 patients with a disease affecting all parts of the cerebellum. Patients with lesions of the cerebellar hemispheres could not be separated from normals by means of posturography. Lesions of the spino-cerebellar afferents (Friedreich' ataxia) caused an omnidirectional low frequency sway with preserved visual stabilization. Patients with anterior lobe atrophy showed a predominant antero-posterior sway, often with a spontaneous high frequency body tremor around 3 Hz. Vestibulo-cerebellar lesions exhibited omnidirectional low frequency sway poorly stabilized by vision. Quantitative posturography helps to localize cerebellar lesions and allows for quantitative follow-up studies of cerebellar diseases.

Adult↗
PubMed1984

Characteristic alterations of long-loop "reflexes" in patients with Friedreich's disease and late atrophy of the cerebellar anterior lobe.

Sudden tilting of a platform around the axis of the human ankle joint causes a regular pattern of short and medium latency EMG responses in the stretched triceps surae muscle and a long latency response in its antagonist, the anterior tibial muscle. This paper reports alterations of these EMG responses in 41 patients with cerebellar lesions. Patients with anterior lobe atrophy exhibited normal latencies of all EMG responses, but an increase in duration and amplitude of the long latency response. This may at least partially explain the 3 Hz postural tremor, which can be evoked in these patients through a toe-up tilt of the platform. Patients with lesions restricted to the vestibulocerebellum and to the cerebellar hemispheres exhibited normal latencies of all EMG responses. The most specific finding in all of the patients suffering from Friedreich's ataxia (affecting spinal afferents) was the massive delay of the stabilising response of the anterior tibial muscle. The fact that the patients with lesions restricted to the cerebellum invariably exhibited normal latencies of postural "reflexes" indicates that the exact "timing" of these responses is independent of the cerebellum. The duration and amplitude of the long latency response of the antagonist, however, seems to be controlled by the cerebellum.

Afferent Pathways↗
PubMed1983

A new method for the simulation of electric fields, generated by electric fish, and their distorsions by objects.

Among the many species of fishes endowed with electric organs Mormyriformes and Gymnotoidei are known to emit and receive electric signals for the purposes of intraspecific communication and recognition of objects. Models which have been proposed for this electro-sensory system generally assume steady-state conditions. On the other hand, the very character of the signals itself and the idea that the cerebellum might be working as a clock point to the importance of the signal dynamics. Therefore a new approach to the simulation of electric fields is described in the paper. The basic idea is to superpose the fields of point charges in a way that the sum is in accordance with the fish's electric field. The same technique could be used to simulate the influence of objects on the electric field. Following a suggestion of Dr. E. Kasper I used a simpler but equal effective approach for object simulation consisting in the use of a dipole instead of point charges. The model described is easily applied to diverse situations and allows one to estimate the influence of various parameters (size, shape, and position) on the "electric image" of an object. Furthermore, the well-known behaviour of tailbending and its consequences in object recognition can be simulated. The results underline the importance of signal dynamics for species with pulse-type discharges.

Animals↗