Neurosurgery
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A case of acute posttraumatic myelopathy resulting from hemorrhage into synovial cysts bilaterally at the C-6, C-7 facet joints is presented. The pathogenesis of synovial cysts remains unclear, although reports in the literature have implicated trauma leading to cyst enlargement. ⋯ Radiographic analysis including plain films, computed axial tomography, and metrizamide myelography are of value in establishing a neurological diagnosis. Surgical decompression and excision of the lesion may result in significant neurological improvement.
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The possibility of neural damage during extracranial brain stimulation for motor evoked potentials (MEPs) is discussed from the perspective of animal studies in which the stimulating electrodes were in direct contact with the brain. These data indicate that the charge per phase used in most of the extracranial MEP protocols is sufficient to induce neural damage if the stimulation is applied continuously for several hours. ⋯ The possibility of such focusing may be less with magnetic field than with direct electrical field stimulation. We stress the need for additional animal studies designed to delineate a range of safe stimulus parameters for this particular technique.
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Somatosensory evoked potentials (SSEPs) and corticomotor evoked potentials (CMEPs) were utilized to study acute and chronic blunt spinal cord trauma. Rats, anesthetized with ketamine hydrochloride, were subjected to parasagittal craniectomies and midthoracic laminectomies. SSEPs were cortically recorded and CMEPs were transcortically produced using epidural ball and disc electrodes. ⋯ The results of this study suggest that the CMEP is a reliable indicator of the initial degree of loss of neurological motor function in acute blunt spinal cord injury in the rat, as well as an accurate measure of the degree and extent of recovery. The rat model as outlined here is a simple and inexpensive system for evaluation both clinically and electrophysiologically of the degree of motor recovery from spinal cord injury. This model should prove useful in the evaluation of promising pharmacological agents for potential use in the treatment of acute spinal cord injury.
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The anatomical basis of the pyramidal tract is reviewed with respect to its proposed role in the conduction of the motor evoked potential. The fiber diameter profiles are discussed in relation to the measured conduction velocities of the corticospinal tract in humans. Stimulus parameters utilized to obtain the motor evoked potential are reviewed in relation to the laterality of response, response threshold, and properties of spatial and temporal summation. A discussion of the major descending tracts involved with walking as opposed to fine distal use of the digits is undertaken in the context of the possible prognostic capabilities of the motor evoked potential.