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Biomedical subjects

B Klemar

Publications and source records attributed to B Klemar.

14 recordsLinked to original sources
PubMed1995

A new high-frequency magnetic stimulator with an oil-cooled coil.

A new high frequency magnetic stimulator, Labmag, is described which may be used in clinical neurophysiology and for the treatment of spasticity in multiple sclerosis. In order to avoid heating of the coil during repetitive stimulation, an oil/air cooling system was employed. The magnetic stimulus waveform is a half cosine with a rise time of 200 microseconds and a pulse width of 400 microseconds induced by alternating capacitor voltage. The Labmag product was compared with a commercially available high frequency stimulator, MagPro. The electric fields induced by Labmag were half the size of those induced by MagPro at identical stimulus intensities. Using a leaky integrator to simulate the effects on neurons, only minor differences in integrated electric fields were observed. There were no changes of the electric fields in relation to coil geometry. A minor difference in electric fields (1.0 +/- 0.8%) was observed when the polarity of the capacitor voltage alternated. Compound muscle action potentials (CMAPs) evoked by transcranial magnetic stimulation were recorded from the first dorsal interosseous muscle (FDI) in eight subjects. Threshold intensities of CMAPs evoked by Labmag (58 +/- 7%) were significantly smaller (p < 0.05) than threshold intensities obtained with MagPro (63 +/- 8%). Peak-to-peak amplitudes, P-Pamps, of CMAPs were significantly smaller after single stimulations with Labmag at stimulation intensities of 130 and 140% of threshold intensity.

Adult↗
PubMed1994

Anal sphincter maximum functional electrical stimulation in detrusor hyperreflexia.

Evaluation of maximal electrical sphincter stimulation in 13 patients with detrusor hyperreflexia showed no change in volume at first or duration of hyperreflexia, or bladder capacity during a stimulation period of 4 times 30 minutes, when compared single blind to a similar registration without sphincter stimulation. After 12 days of stimulation 30 minutes twice daily, 10 of 12 patients reported improvement in irritative bladder symptoms but no significant changes were seen in the cystometric findings and only 2 patients wanted to continue treatment. The anal plug stimulator had 4 separate electrodes, 1 stimulating at a time. Despite this, significant fatigue of the sphincter activity was measured after the stimulation period. In conclusion, we found that the efficacy of sphincter stimulation in patients with detrusor hyperreflexia and irritative bladder symptoms was limited.

Adult↗
PubMed1988

Selective sacral rootlet neurectomy in the treatment of detrusor hyperreflexia. Technique and long-term results.

Selective sacral neurectomy was performed in 12 patients with intractable urge incontinence of long duration (mean 12 years) caused by detrusor hyperreflexia. There was great variation in the innervation of the bladder, but resection of an S-3 root or rootlet was carried out in all patients. Six of the patients, who were followed for a mean period of 5.8 years, were cured, and symptoms recurred in two patients after 1 1/2 and 2 years. In patients whose detrusor hyperreflexia recurred, the amplitude of the bladder contractions was significantly lower. This treatment appears reasonable in patients with severe intractable voiding dysfunction caused by detrusor hyperreflexia.

Adult↗
PubMed1986

Experimental electrical stimulation of the bladder using a new device.

Repeated bladder contractions were evoked during a six month period in three unanaesthetized female minipigs by using unipolar carbon fiber electrodes embedded in the bladder wall adjacent to the ureterovesical junction. In contrast to bipolar and direct bladder muscle stimulation unipolar electrodes at each ureterovesical junction evoked bladder pressure increase similar to those produced in previous investigations in dogs. Sacral nerve stimulation of S2 evoked bladder contraction at a minimal current. Microscopic examination revealed no cellular reactions to the carbon fibers but a subcutaneous reaction to the receivers was seen and was thought to be due to mechanical irritation. The clinical implication of the findings is discussed.

Animals↗
PubMed1982

Anal sphincter responses after perianal electrical stimulation.

By perianal electrical stimulation and EMG recording from the external anal sphincter three responses were found with latencies of 2-8, 13-18 and 30-60 ms, respectively. The two first responses were recorded in most cases. They were characterised by constant latency and uniform pattern, were not fatigued by repeated stimulation, were most dependent on placement of stimulating and recording electrodes, and always had a higher threshold than the third response. The third response was constantly present in normal subjects. It had the longest EMG response and the latency decreased with increasing stimulation to a minimum of 30-60 ms. This response represented the clinical observable spinal reflex, "the classical anal reflex". The latencies of the two first responses were so short that they probably do not represent spinal reflexes. This was further supported by the effect of epidural anaesthesia which left the first responses unaffected but abolished the classical anal reflex. The origin of the two first responses is discussed and models involving antidromal impulse propagation in the efferent fibre as the afferent limbs of the responses are proposed.

Anal Canal↗
PubMed1981

A new electronic device for quantitation of EMG activity.

A description is given of a new electronic device capable of analysing and converting the EMG response in a small volume of muscle in such a way that two output signals are obtained: one as an analogue voltage proportional to the instantaneous firing rate, the other as a number of impulses counted in a preselectable measurement-time window. The method thus allows quantitative measurements of reflex responses and has proved its value, especially in the investigation of reflex reactions in the pelvic sphincters.

Electromyography↗
PubMed1981

Standardisation of the electrical elicitation of the human flexor reflex.

The threshold and latency of the human flexor reflex were recorded by different kinds of electrical stimuli in order to find the optimal stimulus, defined as the lowest amount of currency and the shortest possible duration. Stimulation was given over the posterior tibial nerve of the foot. The reflex response was recorded from the tibialis anterior muscle and the number and duration of the pulses and the inter-phase interval were varied. A train of five square wave pulses with a duration of 0.5 ms separated by 1 ms were found most suitable in quantitative studies of the reflex. Twenty-four normal persons were investigated in this way as a basis for normal values. The day-to-day variations of the reflex were small in normal subjects.

Adolescent↗
PubMed1980

Effect of the alpha-adrenergic blocking agent thymoxamine on the neurogenic bladder and urethra.

The effect of the alpha-adrenergic blocking agent thymoxamine by intravenous administration was studied in 25 patients with spastic paraplegia and uninhibited neurogenic bladder. By cystometry a shift to the right of the first desire to void, the threshold of the first uninhibited contraction and a reduction of the pressures of the uninhibited contractions was found, but the bladder capacity was unchanged. The urethral pressure profile studied in 10 patients showed reduction in most and the peak value in all the patients. EMG from the external urethral sphincter in five patients showed damping of anal reflexes in all cases and in basic activity and cough reflexes when appropriate for studies. The site of action on the bladder is most likely adrenergic receptors in the bladder and the unchanged bladder capacity may be related to a too-short duration of the effect of thymoxamine. The effect on the spastic striated pelvic sphincters may be central, whereas the effect on the smooth muscle may be peripheral. Feedback from the drug relaxed proximal part of the urethra to the bladder might also be of importance.

Adolescent↗
PubMed1979

Counting of flexor spasms.

A method is described which is able to convert muscular contraction to a top, which can be counted electronically or visually. Such contractions are found much more frequently in patients with flexor spasms than in normal subjects during studies over 6-9 hours during the night. The method is of value in long-term recording, in evaluating antispastic therapy and in analyzing factors influencing flexor spasms.

Adolescent↗
PubMed1978

Effect of dantrolene sodium on the spastic external urethral sphincter recorded by sphincterometry.

An improved method of sphincterometry is described, which is easy to perform in men and also may be used in women. It gives reproducible results in the individual patient. The maximum pressure was found by radiographic and reflexological examinations of the external urethral sphincter. When 0.5 mg./kg. body weight dantrolene sodium was injected intravenously the resistance of the external urethral sphincter was found to be reduced significantly, presumably reflecting a reduction of reflex activity.

Dantrolene↗
PubMed1978

Human anal reflexes.

By perianal electrical stimulation and EMG recording from the external anal sphincter the anal reflex was constantly present in normal subjects. The latency decreased within certain limits with increasing stimulation to an average minimum latency of 50 ms (SD 10.5). There was no difference between the minimum latency in normal subjects and patients with suprasegmental lesions of the CNS. The latency may be prolonged in patients with lesion of the reflex arc. By stimulation over the posterior tibial nerve behind the medial malleolus a reflex reaction could be picked up constantly from the anal sphincter in normal subjects. This reflex had a longer latency but a lower threshold than the reflex reaction from the tibialis anterior muscle. The average minimum latency from the anal sphincter was 93 ms (SD 21.1) and from the tibialis anterior muscle 64 ms (SD 7.9). In the absence of the anal reflex it may be possible to localise the defect to the afferent or efferent parts of the reflex by using types of stimulation. Preliminary studies of spinal shock revealed a perianally elicited anal reflex in all cases, but also a response to peripheral stimulation in some of the cases, more frequently found in the anal sphincter than in the tibialis anterior muscle.

Anal Canal↗