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Biomedical subjects

Z Rodi

Publications and source records attributed to Z Rodi.

6 recordsLinked to original sources
PubMed2001

Neurophysiological mechanisms underlying motor evoked potentials in anesthetized humans. Part 2. Relationship between epidurally and muscle recorded MEPs in man.

OBJECTIVE AND METHODS: Direct (D) and transynaptic, (i.e. indirect) (I) corticospinal tract (CT) discharges were simultaneously recorded epidurally with muscle motor evoked potentials (MEPs) in patients under different levels of anesthesia. The effects of the one, two or more equal electrical stimuli, applied transcranially or directly to the motor cortex, were studied at different interstimulus intervals (ISIs) to determine the optimal conditions for eliciting I and MEP responses. RESULTS AND CONCLUSION: At anesthetic levels permiting large D and I responses to single stimuli, optimal D and I wave facilitation and MEPs occurred with two stimuli at ISIs greater than 4 ms (e.g. at 5.9 and 8 ms). When single electrical stimuli elicit only a D response, optimal MEP responses are determined by the number of stimuli and the recovery of CT fibers excitability (e.g. at an ISI of 4 ms).

Anesthesia↗
PubMed2001

Intraoperative monitoring of the bulbocavernosus reflex: the method and its problems.

OBJECTIVES: This study evaluates the method of intraoperative neurophysiological monitoring of the bulbocavemosus reflex (BCR) with reference to stimulation and detection. METHODS: The study was performed on a group of 65 patients, 53 men and 12 women, who underwent surgery for lower thoracic and lumbar spinal trauma, with no neurological deficit prior to or following surgery. Stimulating electrodes were placed on the dorsum of the penis or the clitoris. Single and double stimuli were used, as well as trains of 3, 4 and 5 stimuli. Detecting wire electrodes were introduced into the perianal region. RESULTS: A single stimulus elicited the BCR in 50%, pairs in 75%, trains of 3 in 95%, and trains of 4 and 5 in 100% of patients. With placement of the detecting electrodes 2.5 cm deep to the skin, the BCR was detected in 13% of hemisphincters in women, and in 81% of hemisphincters in men. With controlled intramuscular placement of detecting electrodes, the BCR was detected in 97% of hemisphincters in men. With bifocal detection the BCR amplitudes were 30-312 mV (median 90), and interside amplitude ratio was 0.05-1 (median 0.66); with monofocal detection, amplitudes and interside amplitude ratio were 30-560 mV (median 200) and 0.15-1 (median 0.86), respectively. CONCLUSIONS: A train of 4 electrical stimuli is optimal in eliciting the BCR in anesthetized patients. The low rate of elicitability in women was most probably due to inefficient stimulation. Detection was improved by controlled intramuscular placement of electrodes. Monofocal detection yielded higher BCR amplitudes. Interside difference and interindividual variability of the BCR amplitude were considerable.

Adolescent↗
PubMed1999

Standardization of anal sphincter EMG: technique of needle examination.

The external anal sphincter (EAS) anatomy is complex, and no exact technique of needle electrode insertion into it for electromyography (EMG) has been described. To define optimal positions for needle electrode insertions, EAS muscle topography was studied by concentric needle EMG. Fifteen women without uroneurological disorders were examined. Perpendicular insertions were made superficially (just under the mucosa) at the mucocutaneous junction, 5 and 10 mm more proximally (toward the anus), and at the anal orifice. In addition, at the anal orifice, deeper insertions were made. Superficially, EMG activity was detected at the mucocutaneous junction in 9 (60%) subjects. In the remaining 6, the muscle was found either 5 mm (in 5) or 10 mm (in 1) more centrally. At the anal orifice, superficial EMG activity was present in 67% of women. On deep insertion (15-25 mm) at the anal orifice, muscle was always present. It is suggested that, in further studies, the portions of the EAS muscle examined should be specified.

Adult↗
PubMed1997

A method of uroneurophysiological investigation in children.

Characteristics and reproducibility of bulbocavernosus reflex (BCR) and pudendal somatosensory evoked potentials (PSEP) elicited by mechanical stimulation in children were tested. Twenty-five male children aged 5-14 years without uroneurological complaints were enrolled in the study. In addition to electrical stimulation, a specially constructed electromechanical hammer triggered by an oscilloscope was used for mechanical stimulation of distal penis. All responses were detected by surface electrodes. The latencies and amplitudes of averaged as well as latencies of single BCR on single and double electrical stimuli were determined. Mechanical stimulation was described as much less unpleasant than electrical stimulation. Both mechanical/electrical stimulation elicited consistent and reproducible responses in high percentages of children (BCR: average, 80%/71%, single, 94%/100%; PSEP: 96%/96%, respectively). BCR latencies were significantly longer and PSEP amplitudes were significantly higher on mechanical stimulation. The compliance with mechanical was much better than with the electrical stimulation and the former can be recommended for clinical use. The effective mechanical stimulus delivered by a particular mechanical stimulator has a characteristic 'delay' (as to the actual point of triggering the oscilloscope ray) which influences the latency reading of responses; appropriate control data are therefore necessary.

Adolescent↗
PubMed1996

Motor evoked potentials during brain surgery.

In order to obtain a robust method for intraoperative monitoring of motor pathways, different stimulation patterns to elicit muscle motor evoked potentials (MEPs) were studied during neurosurgical procedures in 3 patients. MEPs were recorded by a catheter electrode in the subdural space and/or by needle electrodes in limb muscles. For stimulation single pulses and trains consisting of two to five pulses were used. Muscle MEPs were only obtained after trains of at least 3 stimuli while single/double stimuli were inefficient. Simultaneous subdural recordings showed that single and double stimuli only elicited D-waves, whereas trains of 3 or more stimuli generated I-waves, as well. We propose that train stimulation can overcome the depressive effects of anesthesia on cortical motoneurons.

Brain↗