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Biomedical subjects

C Biro

Publications and source records attributed to C Biro.

4 recordsLinked to original sources
PubMed1990

Urologic changes after cauda equina compression in dogs.

Relative degrees (25%, 50% or 75%) of constriction of the entire cauda equina at the seventh lumbar level were performed on eighteen pure bred female beagle hounds by surgically implanting a circular polyethylene loop with an imbedded stainless steel wire. The wire was mechanically constricted by external control and the degree of compression was confirmed by pre- and postoperative magnetic resonance imaging or computed tomography scanning. A control group of two dogs had laminectomy only. Neurologic function was evaluated daily. Cystometrics were performed on each dog after constriction had been present for three months. Cortical evoked potentials (CEPs) were obtained on all dogs preoperatively, immediately following constriction and at monthly intervals for three months. Dogs were sacrificed at three months and the cauda equina and spinal cord were examined histopathologically. Cystometric tracings were noted to become a flat line with 75% compression of the cord. Less compression had minimal effect on the cystometric curves. The mean latency, determined by cortical evoked potentials, was noted to increase by 3.2%, 7.8%, and 17.2% immediately after 25%, 50% and 75% constriction, respectively. Histologic changes ranged from occasional enlargement of the axons on the periphery of the cauda equina with 25% constriction to severe loss of all axons and atrophic roots at the level of the constricting band with 75% constriction.

Animals↗
PubMed1990

Urologic function after experimental cauda equina compression. Cystometrograms versus cortical-evoked potentials.

Twenty female beagle dogs underwent an L6-7 laminectomy and six dogs each had 25, 50 or 75% constriction of the cauda equina and 2 control dogs had laminectomy only. Cystometrograms were performed pre- and post-operatively and three months after constriction. Cortical evoked potentials were monitored pre- and post-operatively and monthly for three months. After three months of constriction, the cauda equina of these dogs in each group was examined histologically and vascular circulation was examined by latex and India ink injection (Spalteholz technique). The control dogs had normal CMGs and CEPs. Twenty-five percent constriction caused no CMG changes and mild CEP changes. Fifty percent constriction caused no statistically significant CMG changes, major CEP changes and venous congestion of the nerve roots and dorsal root ganglia. Seventy-five percent constriction produced severe CMG changes with detrusor areflexia, increased bladder capacity and clinical incontinence. CEPs also had marked deterioration. Vascular analysis revealed severe arterial narrowing at the level of constriction and venous congestion of the nerve roots and dorsal root ganglia. Blockage of axoplasmic flow and nerve root atrophy was seen in all dogs with 75% constriction. Cortical evoked potentials were the most sensitive predictor of neural compression. CMGs were not sensitive until severe compression was achieved. Bladder dysfunction, i.e., detrusor areflexia, appears to occur with blockage of axoplasmic flow and early sensory changes occur with neurovenous congestion.

Animals↗
PubMed1990

Experimental lumbar spinal stenosis. Analysis of the cortical evoked potentials, microvasculature, and histopathology.

An animal model of lumbar spinal stenosis was developed in which the pathophysiology of this condition could be examined. Four experimental groups, each containing six dogs, were studied. One group had a laminectomy of the sixth and seventh lumbar vertebrae only; these animals served as controls. In the three other groups, a laminectomy was performed and the cauda equina was constricted by 25, 50, or 75 per cent to produce chronic compression. Cortical evoked potentials were recorded preoperatively, immediately after constriction, and at one, two, and three months postoperatively. Daily neurological examinations were carried out, and the neurological deficits were graded using the Tarlov system. After three months of constriction, the cauda equina of three dogs in each group was examined histologically, and the vascular circulation was examined by latex and India-ink injection with a modification of the Spalteholz technique. The animals in the control group showed no neurological abnormalities, no changes in cortical evoked potentials, normal microvascularity, and no histopathological changes in the nerve roots or the spinal cord. The dogs in which the cauda equina had been constricted 25 per cent had no neurological deficits, mild changes in cortical evoked potentials, slight histological changes, and venous congestion of the root and dorsal root ganglion of the seventh lumbar nerve. The dogs in which the cauda equina had been constricted 50 per cent had mild initial motor weakness, major changes in cortical evoked potentials, edema and loss of myelin in the root of the seventh lumbar nerve, and moderate or severe venous congestion of the root and dorsal root ganglion of the seventh lumbar nerve. The dogs in which the cauda equina had been constricted 75 per cent had significant weakness, paralysis of the tail, and urinary incontinence; two dogs recovered by the third month, but all had neurogenic claudication for three months. All six dogs had dramatic changes in cortical evoked potentials and had complete nerve-root atrophy at the level of the constriction. There was blockage of axoplasmic flow and wallerian degeneration of the motor nerve roots distal to the constriction and of the sensory roots proximal to the constriction, as well as degeneration of the posterior column. Severe arterial narrowing at the level of the constriction and venous congestion of the roots and dorsal root ganglia of the seventh lumbar and first sacral nerves were also present. Cortical evoked potentials revealed neurological abnormalities before the appearance of neurological signs and symptoms.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗