Biomedical subjects

J Belsh

Publications and source records attributed to J Belsh.

3 recordsLinked to original sources

PubMed1995

Magnetic brain stimulation: safety studies.

We describe short-term and long-term safety studies after low repetition rate magnetic brain stimulation in 10 normal subjects. We obtained quantitative EEG data, psychometric test results, serum prolactin and cortisol levels before and after brain stimulation. EEG and psychometric data were also obtained in 5 of these subjects 16-24 months after the initial experiment. Short- and long-term studies did not show any deleterious effects. Randt delayed recalls, however, showed a transient reduction in the score immediately after stimulation which resolved on retesting in 2 weeks. To address the question of fatigue we repeated Randt tests in 4 subjects before and after magnetic brain stimulation but without the other extensive psychometric, EEG and blood tests. Pre- and post-stimulation scores on this occasion showed no significant difference in these 4 subjects suggesting that the transient changes in the previous Randt score were related to fatigue. We conclude that single-pulse magnetic brain stimulation has no deleterious effects after magnetic brain stimulation.

Adult↗

PubMed1995

Percutaneous magnetic coil stimulation of the phrenic nerve roots and trunk.

We describe a technique of percutaneous magnetic coil (MC) stimulation of the phrenic nerve trunk on one side of the neck and phrenic roots over the upper cervical vertebral column in 10 normal subjects and 2 patients. We were able to obtain compound muscle action potentials (CMAPs) from the diaphragm at two sites (xiphoid process and 7th intercostal space) after stimulation of the phrenic nerve trunk and roots. We noted that the onset latencies after phrenic root stimulation remained fixed despite increasing the stimulus intensity from 50% to 100% and on moving the MC vertically or laterally, suggesting that stimulation of the fastest conducting fibers was occurring at a fixed site, most likely at the intervertebral foramina. Absent responses unilaterally in one and prolonged latencies to diaphragmatic CMAPs in another patient confirmed phrenic neuropathy in these patients.

Action Potentials↗

PubMed1993

Magnetic coil stimulation of the human lumbosacral vertebral column: site of stimulation and clinical application.

We describe the technique of magnetic coil (MC) stimulation of the lumbosacral roots and the possible site of stimulation in 22 control subjects, and the clinical usefulness of MC stimulation in 5 patients with low back pain. We observed 2 components in the compound muscle action potential of the soleus muscle following MC stimulation over the lumbosacral region. The second component had the physiological properties of the H reflex. The conduction time from the anterior horn cells of the lumbosacral spinal cord to the site of nerve root stimulation over the lumbosacral vertebral column was indirectly calculated as between 3.9 and 4.1 msec. Assuming a conduction velocity of 50 m/sec this would represent a distance of approximately 20 cm from the spinal motor neurons. Based on our control and patient data we conclude that the MC stimulation may be an useful technique for the diagnosis of lumbosacral radiculoplexopathy.

Adult↗