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Biomedical subjects

N Mai

Publications and source records attributed to N Mai.

53 records · Page 3Linked to original sources
PubMed1990

[Life-threatening complications and death in anorexia nervosa].

The medical complications of anorexia nervosa may endanger the patient in several ways; the severity of somatic complications may be underestimated; medical findings may be assigned to other diagnoses than anorexia nervosa or complications may indicate an emergency, leading to therapeutic activities which may result in a life-threatening situation for the patient. There are some indications that phosphate depletion is involved in medical complications in anorexia nervosa, even in those cases with fatal outcome. Acute hypophosphatemia may be induced by hyperalimentation.

Anorexia Nervosa↗
PubMed1990

[Comments on specific early rehabilitation of patients with severe craniocerebral trauma].

The considerable advances made in the rescue and intensive care fields have entailed drastically increased numbers of survivors of severe head injury. Because of ethical reasons alone, the call for early rehabilitation of patients with persistent vegetative state post-trauma appears justified. Aside lifesaving intensive medical care in the acute phase, available empirical studies have so far not been able to provide evidence for the superiority of specific early rehabilitation measures. Clinicians lack pragmatic decision-making aids in the question of how long patients should be treated in the acute clinic. Nursing homes currently are no alternative, as they will hardly ever be equipped in a manner enabling them to cope with the considerable nursing requirements posed by these patients.

Brain Damage, Chronic↗
PubMed1989

Residual control of isometric finger forces in hemiparetic patients. Evidence for dissociation of performance deficits.

Dissociation of performance in the control of isometric finger forces was observed in 6 patients with left-sided unilateral lesions involving sensorimotor areas. In a precision task subjects had to maintain, under visual feedback, a low constant force (2.5 N) while holding a force transducer between thumb and index finger. Performance was compared with that in a speed task, where changes had to be produced, as rapidly as possible, between two prescribed forces (6.25 and 18.75 N). While there were severe deficits in fast force changes corresponding to the functional impairment of the right hand in all patients, right hand maintenance of low isometric force remained intact in the same patients.

Cerebral Cortex↗
PubMed1989

On the role of feedback in maintaining constant grip force in patients with cerebellar disease.

The effect of visual feedback on maintaining low finger forces was investigated in patients with chronic cerebellar disease. Precise information about deviation from target force was compared with discrete feedback signaling only 3 states of performance and a condition of withdrawal of feedback. Forces were produced under isometric conditions and against a spring load (anisometric condition). Large performance differences were observed dependent on feedback condition. Maintenance of anisometric force was found to be nearly normal in patients with severe deficits in controlling isometric force.

Biofeedback, Psychology↗
PubMed1988

Fast repetitive force changes in hemiparetic and cerebellar patients.

A method for the continuous registration of rapid isometric force changes was investigated in 24 healthy control persons, 10 hemiparetic patients and 10 cerebellar patients. Though the selection of both patient groups involved comparable deficits with respect to the number of force changes attained, the analysis of the underlying force-velocity patterns revealed considerable differences in the performance of hemiparetic and cerebellar patients. Hemiparetic patients showed gross deficits in both the force increasing and decreasing phases. In contrast to this, most cerebellar patients were able to release force as fast as normal controls, while marked slowness was only found for the force increasing phases.

Adult↗
PubMed1988

Control of isometric finger force in patients with cerebellar disease.

Control of isometric forces during grasping or handling of objects is an essential feature of all skilled manual performances. Previous studies of hand function in cerebellar patients were restricted to movements; force control was only investigated under isotonic conditions in combination with movements. Control of isometric forces during voluntary contraction of finger muscles was investigated in 31 patients with chronic cerebellar disease and in 20 normal controls. Eight patients with Friedreich's ataxia were considered to be typical for a disease affecting the afferents to the cerebellum; 4 patients with anterior lobe atrophy, which affects leg movements to a greater extent than finger movements, were compared with 3 patients with hemisphere lesions; 16 patients suffered from diffuse cerebellar atrophy. Using a recently developed microcomputer system for the continuous measurement of finger force, control of isometric force was studied in several tasks within the same subjects. The tasks included the maintenance of constant force output at different force levels with and without visual feedback, fast repetitive force changes, tracking of a sinusoidal target presented visually, and measurement of maximum grip force. The amount of voluntary contraction in terms of muscular power was normal in all patients; in all other tasks clear deficits were observed. The extent of the disturbances was highly variable between patients even within the same clinical subgroup. The detailed analysis of force traces revealed a great variety in types of disturbance. The frequently observed slowing of the speed in repetitive force changes can be attributed to different components in different patients and not only to difficulties at turning points as might be predicted from comparable movement studies. In addition, performance deficits across different tasks were not uniform, indicating dissociation of impairment. Deficits in maintaining force, which may be interpreted as dysmetria or due to tremor, do not necessarily imply an abnormality in diadochokinesis, as measured in fast repetitive force changes, nor does the converse apply.

Adolescent↗
PubMed1985

Maintenance of low isometric forces during prehensile grasping.

A specially designed microcomputer-controlled force measurement system was tested in 24 normal adults. The task was to maintain a prescribed low isometric grip-force (2.5 Newton) under different visual feedback conditions. The performance variability across subjects and conditions was surprisingly low. Normal adults can maintain low isometric forces with great accuracy. No left/right hand differences could be found in the subjects investigated. These results seem to qualify our procedure for the clinical examination of neurologically impaired patients.

Adult↗
PubMed1985

A microcomputer system for the measurement of finger forces.

In the analysis of hand functions, the production and control of forces exerted during voluntary contraction of the finger muscles plays an important role; unfortunately such an analysis is rarely seen in routine clinical examinations of neurological patients. A microcomputer controlled system for the measurement and analysis of finger forces is described. The system consists of a modified Z80 based microcomputer, a commercially available high precision force transducer, a specially designed force signal amplifier and a suite of menu-driven user interactive programs. A variety of tasks is implemented by means of the computer programs. In addition to the measurement of maximum hand grip force, the system is able to record forces continuously as a function of time. Task characteristics and the type of feedback presented to the subject are under user control; they can be varied to meet clinical or experimental requirements. Examples of programs and clinical applications are presented and discussed.

Biomechanical Phenomena↗
PubMed1984

Action of the benzodiazepine antagonist Ro 15-1788 in humans after sleep withdrawal.

Subsequent to one night of sleep withdrawal the specific benzodiazepine antagonist Ro 15-1788 was infused to 5 healthy volunteers using a double-blind placebo-controlled cross-over design. Using several standardized psychological tests (viso-motor tracking task, complex choice reaction time, trail making test, visual attention and concentration), no performance-improving effects of Ro 15-1788 could be demonstrated. The results are discussed regarding the possible existence of endogenous benzodiazepine ligands.

Adult↗
PubMed1983

Selective disturbance of movement vision after bilateral brain damage.

A patient who suffered bilateral posterior brain damage exhibited disturbance of movement vision in a rather pure form. The patient had no impression of movement in depth, and could only discriminate between a stationary and a moving target in the periphery of her otherwise intact visual fields. She had some movement vision in the central part of her visual fields, provided that target velocity did not exceed 10 deg/s. Neither did she possess visual movement after effects nor apparent (phi) visual movement. In addition, visually guided eye and finger movements were impaired. In contrast to the disturbance of movement perception in the visual modality, movement perception elicited by acoustic and tactile stimuli was not impaired. On the basis of the localization of the cerebral damage (as judged by CT scanning and neuropsychological testing) it is concluded that the observed disorder in movement vision is due to bilateral cerebral lesions affecting the lateral temporo-occipital cortex and the underlying white matter. The selectivity of the visual disturbance supports the idea that movement vision is a separate visual function depending on neuronal mechanisms beyond the primary visual cortex.

Adult↗
PubMed1979

Preprocessing in computed tomography picture analysis: a "bone-deleting" algorithm.

A procedure for automatic deletion of extracranial parts and bone in computed tomography (CT) pictures is presented. Such a procedure is a prerequisite for many types of quantitative image analysis. The algorithm can delineate complex bone contours and is completely independent of information outside the skull. Special options allow, in addition, the deletion of calcified parts of the brain and of some artifacts. The program is implemented in a general program system (PICPRO) developed for CT image analysis and picture manipulation.

Brain↗
PubMedDate not supplied

Evaluation of precision grip using pneumatically controlled loads.

Precise control of grip force and finger movement is a fundamental aspect of motor tasks in which an object is held and manipulated between the subject's fingers. A new device to measure motor performance which simultaneously records grip force and finger movement is described. The subject holds a small, compressible cylinder between thumb and index finger. The load opposing finger movements is controlled pneumatically and may be altered with computer software. Different types of loads (e.g., constant load, spring load) may be applied. In addition, reactions to perturbing stimuli (e.g., fast changes of load) may be measured. Construction principles and examples of tasks investigating different aspects of hand function are presented in the paper.

Anthropometry↗
PubMedDate not supplied

Disturbed grip-force control following cerebral lesions.

Clinical routine examinations of grip force are usually restricted to measurements of strength; however, more detailed evaluations of grip-force control provide essential information about the characteristics of impaired hand function following cerebral lesions. A device for continuous recording of isometric grip force produced in a precision grip between thumb and index finger was used to develop a method that might be used for routine assessment of grip-force control. Performance was tested in five different tasks involving the evaluation of static and dynamic precision, use of vision in force control, speed, variability, and strength. The authors describe the tasks and present clinical examples demonstrating the method's precision and subtle characterization of disturbed and preserved aspects of force control, which may vary substantially within and between patients.

Brain Diseases↗