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Biomedical subjects

E Knutsson

Publications and source records attributed to E Knutsson.

At least 19 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↗
PubMed1995

Dynamic muscle strength training in stroke patients: effects on knee extension torque, electromyographic activity, and motor function.

The effects of training with isokinetic maximal voluntary knee extensions were studied in stroke patients. Two groups of 10 patients each trained twice a week for 6 weeks. One group trained exclusively eccentric movements and the other exclusively concentric movements. The effects were evaluated from the following tests before and after the training period. The maximal voluntary strength in concentric and eccentric actions of the knee extensor and flexor muscles was recorded together with surface electromyography at constant velocities of 60, 120, and 180 deg.s-1 on three different days. The body weight distribution on the legs while rising and sitting down was measured with two force plates. The self-selected and maximal walking speeds and the swing to stride ratio of the paretic leg were measured. After the training period, the knee extensor strength had increased in eccentric and concentric actions in both groups (p < .05). The eccentric and the concentric strength in the paretic leg relative to that of the nonparetic leg increased in the eccentrically trained group (p < .05) but not in the concentrically trained group. The restraint of the antagonistic muscles in concentric movements increased after concentric (p < .05) but not eccentric training. A nearly symmetrical body weight distribution on the legs in rising from a sitting position was noted after eccentric (p < .05) but not concentric training. Changes in walking variables were not significantly different between the groups. Eccentric knee extensor training was thus found to have some advantages as compared to concentric training in stroke patients.

Aged↗
PubMed1993

Effect of taping the patella on concentric and eccentric torque and EMG of knee extensor and flexor muscles in patients with patellofemoral pain syndrome.

The acute effect of patella taping on torque and electromyographic (EMG) activity in maximal voluntary concentric and eccentric action of the knee extensor and flexor muscles in patients with patellofemoral pain syndrome was studied in 48 patients (62 knees). The patients (28 female, 20 male) were tested concentrically and eccentrically on a Kin-Com dynamometer with simultaneous EMG recording with the patella untaped and medially or laterally taped. Patients with clinically normal patellar mobility did not improve their quadriceps performance by taping of the patella; after medial taping they decreased their muscle torque during concentric work at 60 degrees/s (P < 0.05) and eccentric work at 180 degrees/s (P < 0.05). After lateral taping they decreased their muscle torque during concentric work at 60 degrees/s (P < 0.05) and eccentric work at both 60 degrees/s (P < 0.01) and 180 degrees/s (P < 0.05). Moreover, these patients also decreased their agonist EMG activity during concentric work at 60 degrees/s (P < 0.05) and 180 degrees/s (P < 0.05) and their antagonist EMG activity during eccentric work at 60 degrees/s (P < 0.01). Patients with a clinical lateral patellar hypermobility increased their knee extensor torque after medial taping at 60 degrees/s during both eccentric work (P < 0.01) and concentric work (P < 0.05). The greatest improvement in quadriceps performance, however, was in patients with a clinical medial patellar hypermobility. They increased their knee extensor torque after lateral taping during eccentric work at both 60 degrees/s (P < 0.001) and 180 degrees/s (P < 0.001) and during concentric work at 60 degrees/s (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Treatment of spasticity in children with low dose benzodiazepine.

In an attempt to investigate whether benzodiazepines at low dosage have a significant effect in reducing spasticity among children with cerebral palsy, we carried out a double-blind, placebo-controlled, cross-over study. Twelve children with either spastic diplegia or hemiplegia participated in this study. The mean age was 14 years. The restraint of passive knee movements was determined with a dynamic dynamometer and spastic stretch reflexes were measured as EMG activity in muscles stretched. Clonazepam was given at low dosage (0.02 mg/kg body weight). In each child measurements of passive restraint were made on 2 different days immediately before and 3 h after an i.m. injection of either clonazepam or placebo in randomized order. Clonazepam significantly reduced spastic restraint (P < 0.001) compared to non-significant reduction with placebo. The mean plasma concentration of clonazepam at time of spasticity evaluation was 21 mmol/l which is in the low dose range, far below conventional doses. The study thus shows a positive effect of low dose clonazepam in reducing spasticity in children when given as a single dose.

Adolescent↗
PubMed1993

Long-term results of recurrent laryngeal nerve resection for adductor spasmodic dysphonia.

From a total of 43 adductor spasmodic patients over a 10-year period, 11 underwent resection of a portion of the recurrent laryngeal nerve on one side. The initial results were excellent but a varying degree of recurrence took place in 8 patients. In 4, a reoperation was done. At the final follow-up, 2-8 years after the primary operation, 4 patients were no longer suffering from spasmodic dysphonia, another 5 were better off than before surgery, and 1 remained unchanged. Only 1 was worse off. Electromyographic findings indicated that the recurrence of symptoms was due to regeneration of the nerve fibers.

Adult↗
PubMed1993

MEG localization of interictal epileptic focal activity and concomitant stereotactic radiosurgery. A non-invasive approach for patients with focal epilepsy.

Two patients with complex partial epilepsy and tumour of the temporal lobe scheduled for gamma knife radiosurgery were evaluated pre- and postoperatively by multichannel magnetoencephalography (MEG). Centers of epileptic dipole activity found preoperatively disappeared after the focal irradiation as did the epileptic seizures. Thus, to combine stereotactic MEG and gamma knife radiosurgery seems to be a non-invasive alternative to the conventional neurosurgery in focal epilepsy.

Adult↗
PubMed1993

Isokinetic strength, macro EMG and muscle biopsy of paretic foot dorsiflexors in chronic neurogenic paresis.

Ten ambulatory patients with chronic dorsiflexor paresis due to prior poliomyelitis or lumbar root (LV) lesion and without recent decline of the foot dorsiflexor strength were examined with isokinetic strength measurement, macro EMG and muscle biopsy. Isokinetic strength measurement showed peak torques at 30 degrees/s angular velocity ranging 6-44 Nm and at 240 degrees/s 1-10 Nm. Mean of individual median macro EMG motor unit potential amplitudes was 2020 microV (SD 1040) which was 5-10 times higher than expected values in healthy subjects. Muscle biopsies showed a mean type 1 fibre proportion of 91% (SD 14) and a mean type 1 fibre area of 8561 microns 2 (SD 2773) which was about 2 times larger than those observed in healthy subjects. Peak torque and both motor unit potential amplitude and area were inversely correlated at 30 (p < 0.01 and p < 0.025), 60 (p < 0.025 and p < 0.025) and 120 (p < 0.05 and p < 0.05) degrees/s angular velocity, as were peak torque and type 1 muscle fibre proportion at 30 (p < 0.05) and 60 (p < 0.05) degrees/s angular velocity. Peak torque or macro EMG parameters were not correlated to muscle fibre area. The data suggest that the remaining muscle strength was directly correlated to the degree of collateral sprouting and that about half of it could be attributed to compensatory muscle fibre hypertrophy.

Aged↗
PubMed1992

Preliminary report: validity of symptom analysis and daytime polysomnography in diagnosis of sleep apnea.

The aim of this study was twofold: first, to see if the prevalence of the sleep apnea syndrome (SAS) in a given population could be fairly estimated by our patient questionnaire, mainly based upon the 1979 American Sleep Association definition of SAS; and second, to investigate whether the severity of SAS could be similarly accurately measured by daytime polysomnography (DPSG), as an alternative to the more demanding all-night polysomnography (NPSG). Of 42 patients consecutively examined due to rhonchopathy, 18 had the clinical diagnosis of SAS, which was based on the three symptoms--snoring, sleep disturbances and diurnal hypersomnia--if reported to occur habitually. In 11 patients the diagnosis was established by NPSG [apnea index (AI) greater than 10]. However, in only 10 of the 18 cases NPSG indicated the diagnosis giving a positive predictive value of 56%. When comparing DPSG versus NPSG in 36 patients, the AI ranged from -23 to +65, and the mean AI value was found to be twice as high in the former (mean difference 9.0 +/- 18.4; p less than 0.01). The positive predictive value of DPSG was 63% (10/16). Both the self-report and DPSG were burdened with some 25% false-positive results, and DPSG gave far too variable AI values to be reliable in staging the disease. On the other hand, the negative predictive values were high, 96% (23/24) and 100% (20/20), respectively, indicating their usefulness for screening purposes.

Adult↗
PubMed1992

Torque-velocity relation and muscle fibre characteristics of foot dorsiflexors after long-term overuse of residual muscle fibres due to prior polio or L5 root lesion.

Isokinetic foot dorsiflexion strength and muscle biopsy data from eight patients with overuse of tibialis anterior muscle (TA) fibres due to weakness after prior polio or L5 root lesion were compared to data from age and sex matched, healthy subjects. Concentric peak torque at an angular velocity of 30 degrees/s was 6-24 Nm in the patients and 15-34 Nm in the controls (p < 0.01). Muscle biopsies from TA showed a significantly higher proportion of type 1 fibres in the patients as compared to the controls (p < 0.005). The type 1 fibres in the patients had a significantly larger cross-sectional area than in the controls (p < 0.005). The type 1 fibre proportion and relative area were inversely correlated to the relative concentric torque produced at 180 degrees/s (p < 0.05) and 240 degrees/s (p < 0.05) compared to that produced at 30 degrees/s in the controls but not in the patients. However, the relative concentric torque produced at 180 degrees/s and 240 degrees/s compared to that produced at 30 degrees/s was not significantly different in the patients and the controls. This indicates that the contractile properties of the overused muscle fibres do not change in parallel with the histochemical fibre type.

Aged↗
PubMed1991

Early neurological and electroencephalographic changes after coronary artery surgery in low-risk patients younger than 70 years.

Between September 1986 and January 1988 neurological examination and electroencephalography (EEG) was performed before and one week after coronary artery bypass grafting in 66 patients younger than 70 years. Twenty patients were randomized to a bubble oxygenator without an arterial line filter (Group I), 22 patients to a bubble oxygenator with a depth adsorption filter (Group II), and 24 patients to a membrane oxygenator without a filter (Group III). No patient suffered a major stroke but early central nervous system dysfunction occurred after the operation in four patients (20%) in Group I, in four patients (18%) in group II and in two patients (8%) in group III. The difference between group I and III was not statistically significant but a larger number of patients in the groups might alter this. Our prospective study demonstrated a significant incidence of neurologic dysfunction in a low risk patient population undergoing standard coronary artery bypass surgery.

Adult↗
PubMed1991

The effect of excessive weight loss on skeletal muscle in man. A study of obese patients following gastroplasty.

Lean body mass, muscle biochemistry, enzymehistochemistry and muscle strength were analyzed before and after 10% and 18% body weight loss following gastroplasty in 16 obese patients. Subjective fatigue was also determined, using an arbitrary scale, before and after the operation. Lean body mass and alkali-soluble proteins (non-collagenic proteins) per DNA decreased significantly in the postoperative period. The proportions of type I and type II muscle fibers remained normal postoperatively. The muscle fiber area decreased significantly at 10% body weight loss, with a tendency towards restoration at 18% weight loss, despite continuing loss of lean body mass. Preoperatively the muscle strength, determined as maximum voluntary concentric and eccentric action of the knee extensor and flexor muscles, was not significantly different from that in sedentary, age-matched subjects, but was less than expected from the lean body mass, content of alkali-soluble proteins and muscle fiber size. Muscle strength was not significantly changed postoperatively. According to the fatigue scale, the patients' wellbeing was improved at 18% body weight loss compared with the preoperative status.

Adult↗
PubMed1990

Physical and psychological capabilities during substitution therapy with recombinant growth hormone in adults with growth hormone deficiency.

In a double-blind cross-over study with recombinant methionyl growth hormone (GH) and placebo during 12 weeks, the effect of GH substitution therapy (0.5-06 IU.kg-1.week-1) on physical performance, muscle strength, bone mineral density, and mood and cognitive functions was investigated in 6 GH-deficient adults. During GH substitution serum concentrations of insulin-like growth factor-I and procollagen-III peptide increased in all 6 patients, whereas concentrations of serum urea decreased. Five of the patients identified the GH period and reported improved well-being with increased mental alertness and vitality and improved physical capacity and muscle strength. There was, however, no change of the isokinetic muscle strength during GH substitution therapy, and the working capacity on the bicycle ergometer was just slightly improved in some patients. The bone mineral density was low and unchanged in all patients. Mood and cognitive functions did not change during GH therapy. A reversible fluid retention was observed in one patient during the GH period. In conclusion, short-term GH substitution therapy to GH-deficient adults induced a subjective improvement of general well-being. Longer treatment periods will be necessary to establish the effect on physical capacity, muscle strength, bone mineral density, and mood and cognitive functions.

Adult↗
PubMed1988

Changes in voluntary muscle strength, somatosensory transmission and skin temperature concomitant with pain relief during autotraction in patients with lumbar and sacral root lesions.

Earlier clinical observations of rapid changes of certain neurological dysfunctions after autotraction treatment of patients with lumbar and sacral root affections have been evaluated by objective registration methods. Isokinetic recordings of maximal voluntary strength showed that in 6 out of 8 patients, weakness of the foot dorsal flexor muscles could be more or less completely restored after one session of autotraction resulting in pain relief. In a group of patients with clinical signs of impaired sensibility, the low or abolished SEP responses to nerve stimulation on the affected side were restituted in 4 out of 5 cases during autotraction. The asymmetric leg skin temperatures in 10 patients with sciatic pain levelled off in the 6 cases obtaining pain relief by the traction. The results suggest a causal relationship between pain relief and restitution of certain neurological deficits.

Adult↗
PubMed1988

The effect of voluntary diaphragmatic activation on back lifting.

The effect of increased intraabdominal pressure upon the activation of the erector spinae muscles during back lifting was studied in 10 healthy volunteers. The intraabdominal pressure was increased by voluntary prelifting coactivation of the diaphragm and the abdominal muscles. EMG was recorded with surface electrodes over the diaphragm and the erector spinae, abdominal and intercostal muscles. The EMG signals were rectified and averaged from 20 lifts of 10 kg with and without pressurization to give mean level of activity during 2 s before lifting and during successive angular positions of the trunk during lifting. In 7 of the 10 subjects the pre-lifting coactivation of diaphragm and abdominal muscles reduced erector spinae activity at lift-off and/or during the trunc erecting movement. An increased intraabdominal pressure thus often has an unloading effect on the erector spinae muscle during back lifting.

Abdomen↗
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↗
PubMed1986

Reduction of pain inhibition on voluntary muscle activation by epidural analgesia.

The influence of postoperative pain on muscle function, and the possible effect of local anesthetics on the normal muscle function are discussed. The integrated EMG (IEMG) during maximum voluntary contraction of the quadriceps muscle was registered in ten patients the day after undergoing reconstruction of the anterior cruciate ligament. Recordings were taken before, 5, 12, and 20 min to 25 min after epidural injection of 20 ml of 0.25% lidocaine with adrenaline (2.5 micrograms/ml). As pain gradually subsided, IEMG increased a mean of 2,728% 20 min to 25 min after injection (range 425% to 10,068%), compared to initial recordings before anesthesia. This indicates that pain relief plays a significant role in the ability to normally activate the quadriceps muscle after open knee surgery. Neither the Hoffman (H-)reflex, nor maximum voluntary isokinetic muscle torque was appreciably affected by epidural injection of dilute local anesthetics, as tested on two healthy volunteers. Infiltrations of local anesthetics into the distal part of the quadriceps muscle did not affect maximum voluntary isokinetic knee extension torque. From the experiments performed we conclude that it is possible to selectively block pain by injections of local anesthetics into the epidural space, without interfering with normal muscle function. It might thus be possible to prevent some of the postoperative muscle atrophy by using a continuous epidural analgesia for two to three days following surgery, and starting an early active physical therapy program.

Adolescent↗