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Biomedical subjects

L Gransberg

Publications and source records attributed to L Gransberg.

7 recordsLinked to original sources
PubMed1997

Influences of muscle stretch reflexes on voluntary, velocity-controlled movements in spastic paraparesis.

We studied voluntary, velocity-controlled knee movements in 22 patients with spastic paraparesis (11 male, 11 female) and 22 healthy controls (11 male, 11 female). Torque and EMG activity of the quadriceps and the hamstring muscles were determined in maximal voluntary concentric (shortening) and eccentric (lengthening) actions of knee extensor and flexor muscles at constant movement velocities of 30, 60, 120 and 180 degrees/s, using an active, isokinetic dynamometer. In the spastic patients, the voluntary strength and the agonist EMG activity were reduced in all movements. The reduction was largest in concentric actions at high velocity. The antagonist EMG activity was reduced in the same proportion as the agonist EMG activity in eccentric actions. In concentric actions when stretch is imposed upon antagonists, the antagonist EMG activity increased with the velocity of stretch, indicating stretch reflex activation. In parallel with the stretch reflex activation of antagonists, there was reduced activation of the agonists compatible with Ia reciprocal inhibition of agonist motoneurons. When agonists were stretched in eccentric actions, stretch reflexes appeared to support the voluntary, agonist activation of knee flexor muscles but not knee extensors.

Adult↗
PubMed1995

Localisation of epileptic foci with multichannel magnetoencephalography, MEG.

With the development of multichannel magnetoencephalographs biomagnetic signals can be recorded over large areas at the same time. It allows determination of the magnetic field outside the head generated by spontaneous epileptic discharges. From the maxima of outward and inward magnetic fluxes the locations of the sources of epileptic discharges can be calculated. The biomagnetic signals originating from an epileptic discharge is, however, mixed with biomagnetic signals generated by the background activity of the brain. A localisation based on a single discharge will therefore be influenced by the background activity. To diminish this influence, the biomagnetic signals during repeated identical epileptic discharges have been averaged. It gives a source localisation common to all discharges instead of a widely spread cluster of dipole sources. The error of epileptic dipole source localisations varies with the site of the dipole in the head as judged from studies with implanted dipole sources but also with the direction of the dipole as seen in studies with artificial dipoles in real head volumes. The error is relatively small in areas where the head has a spherical surface if the dipole direction is tangential. At other sites or dipole directions, the error can be very large. Since the site and direction of an epileptic dipole source is unknown it is not possible to estimate the error of localisations except by using models of individual head volumes.

Artifacts↗
PubMed1986

Three-dimensional electrogoniometric gait recording.

Gait recordings of twenty healthy subjects were made on a treadmill and on level ground by means of a light-weight computerised electrogoniometer. The angular excursions in three planes were recorded simultaneously with regard to hip, knee and ankle joints in both legs. Determinations of the mean values and dispersions were then made. In order to establish the reliability of the method tests and retests were performed. Also its validity was checked by comparing the goniometric recordings with concomitant measurements obtained by other methods. The reliability and validity of the method was found to be satisfactory. Apart from flexion of the hip and knee joints during stance phase (i.e. a difference of 2 and 2.4 degrees respectively), no difference was ascertained between walking on a treadmill and walking on level ground.

Adult↗
PubMed1982

Antiparetic and antispastic effects induced by tizanidine in patients with spastic paresis.

The effects of tizanidine were studied in patients with spastic paresis. The study consisted of 4 parts: I, double-blind cross-over trial at maximal dosage 10 mg/day in 13 patients; II, open trial at maximal dosage 32 mg/day in 10 patients; III, long-term medication at dosage 32 mg/day for 6-15 months in 4 patients; IV, single dose (12 mg) administration in 3 patients. The effects were evaluated from clinical examinations, subjective assessments, EMG, gait analysis and quantitative determinations of passive resistance and voluntary strength in isokinetic extensions and flexions of the knee and plantar and dorsal flexions of the ankle at different speeds of motion. At 3-10 mg/day, no effects were observed except for increased prime mover EMG activity in voluntary knee flexions. At 12-32 mg/day, passive resistance decreased significantly in 3 of the movements tested. The maximal voluntary strength increased significantly in 3 movements, frequently associated with enlarged activation of prime mover muscles, less frequently with reduced antagonist co-activation. Functional disability was subjectively reduced and verified by improved gait capacity in 4 patients. Sustained effects on motor performance during long-term medication were verified by withdrawal in 3 patients. Single dose administration resulted in reduced passive resistance and increased voluntary strength, associated with an increased activation of the prime mover muscles. The results indicate that tizanidine exerts its effects in part by reducing spastic restraint, in part by enhancing the capacity to activate paretic muscles.

Adult↗
PubMed1981

Automatic analysis of electro-oculographic (EOG) recordings. Application to audio-vestibular diagnosis.

An automatic, computerized system for analysis of the ocular movements in nystagmus, slow pursuit and saccades is presented. The performance of the system has been tested in healthy subjects, as well as in patients with peripheral or brainstem audio-vestibular disorders. The automatized procedure enables an extended application of opto-motor tests in the clinical examination of patients with suspected retrocochlear and brainstem involvement.

Computers↗