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At least 433 records · Page 24Linked to original sources
PubMed1989

Edema formation in spinal nerve roots induced by experimental, graded compression. An experimental study on the pig cauda equina with special reference to differences in effects between rapid and slow onset of compression.

Edema formation in spinal nerve roots of the pig cauda equina was studied following experimental compression at various pressure levels, durations, and rates of onset, using a fluorescence microscopic technique. The time-pressure thresholds for the occurrence of edema in the nerve roots were: following rapid onset of compression (0.05-0.1 seconds), 2 minutes at both 50 mm Hg and 200 mm Hg, and following slow onset of compression (the pressure was slowly increased during 15-20 seconds), 2 hours at 50 mm Hg and 2 minutes at 200 mm Hg. Generally, the edema formation was more pronounced after rapid than after slow onset of compression. The data in this study also indicate that intraneural edema might be more easily formed in nerve roots than in peripheral nerves after compression injury.

Animals↗
PubMedDate not supplied

Nerve, spinal cord and brain somatosensory evoked responses: a comparative study during electrical and magnetic peripheral nerve stimulation.

Somatosensory evoked potentials (SEPs) and compound nerve action potentials (cNAPs) have been recorded in 15 subjects during electrical and magnetic nerve stimulation. Peripheral records were gathered at Erb's point and on nerve trunks at the elbow during median and ulnar nerve stimulation at the wrist. Erb responses to electrical stimulation were larger in amplitude and shorter in duration than the magnetic ones when 'electrical' and 'magnetic' compound muscle action potentials (cMAPs) of comparable amplitudes were elicited. SEPs were recorded respectively at Cv7 and on the somatosensory scalp areas contra- and ipsilateral to the stimulated side. SEPs showed a statistically significant difference in amplitude only for the brachial plexus response and for the 'cortical' N20-P25 complex; differences were not found between the magnetic and electrical central conduction times (CCTs) or for the peripheral nerve response latencies. Magnetic stimulation preferentially excited the motor and proprioceptive fibres when the nerve trunks were stimulated at motor threshold intensities.

Action Potentials↗
PubMed1982

Lumbar spinal nerve lateral entrapment.

In past years, lumbar nerve lateral entrapment seldom has been diagnosed. A presumptive preoperative diagnosis has been made based on clinical findings and radiographs demonstrating disc resorption. The Computed Tomography scan has made it possible to diagnose the lesion with certainty and accuracy. Treatment for patients who do not respond to conservative measures is a bilateral minimal partial laminectomy. The lateral canal is enlarged by removing the medial and anterior parts of the superior articular process. Adhesion formation is prevented by placing a free fat graft posterior to the dura. Instability is diagnosed by examining stress radiographs and, when present, is treated by a one level posterolateral fusion. After operation, marked improvement was obtained in 62% of patients and slight improvement in another 21%; 17% were unimproved. Sixty-two per cent of patients reported no pain or mild pain. Sixty-six per cent resumed their previous occupation.

Adult↗
PubMed2004

Central sprouting of uninjured small fiber afferents in the adult rat spinal cord following spinal nerve ligation.

Partial nerve injury results in chronic pain that is difficult to treat effectively. To investigate the anatomic basis of this phenomenon we used wheat germ agglutinin-horseradish peroxidase (WGA-HRP) to label the central projections of uninjured small fibers (Adelta and C) in a well-established model of neuropathic pain created by selective spinal nerve ligation in the adult. We found extensive sprouting of uninjured WGA-HRP-labeled afferents into the central termination field in lamina II of dorsal horn normally occupied by L5 afferents whose peripheral axons had been ligated distal to the dorsal root ganglion. The formation of new projections by uninjured fibers into a functionally but not anatomically deafferented field in the adult may play a role in the development of chronic pain.

Afferent Pathways↗
PubMed2006

Time course of substance P expression in dorsal root ganglia following complete spinal nerve transection.

Recent evidence suggests that substance P (SP) is up-regulated in primary sensory neurons following axotomy and that this change occurs in larger neurons that do not usually produce SP. If this is so, then the up-regulation may allow normally neighboring, uninjured, and nonnociceptive dorsal root ganglion (DRG) neurons to become effective in activating pain pathways. By using immunohistochemistry, we performed a unilateral L5 spinal nerve transection on male Wistar rats and measured SP expression in ipsilateral L4 and L5 DRGs and contralateral L5 DRGs at 1-14 days postoperatively (dpo) and in control and sham-operated rats. In normal and sham-operated DRGs, SP was detectable almost exclusively in small neurons (< or =800 microm2). After surgery, the mean size of SP-positive neurons from the axotomized L5 ganglia was greater at 2, 4, 7, and 14 dpo. Among large neurons (>800 microm2) from the axotomized L5, the percentage of SP-positive neurons increased at 2, 4, 7, and 14 dpo. Among small neurons from the axotomized L5, the percentage of SP-positive neurons was increased at 1 and 3 dpo but was decreased at 7 and 14 dpo. Thus, SP expression is affected by axonal damage, and the time course of the expression is different between large and small DRG neurons. These data support a role for SP-producing, large DRG neurons in persistent sensory changes resulting from nerve injury.

Animals↗
PubMed1991

Spinal nerve root compression. Nutrition and function of the porcine cauda equina compressed in vivo.

A model for experimental studies of acute, graded compression of the cauda equina in pigs was presented (Olmarker et al. 1991a). Detailed analyses of the neural and vascular anatomy demonstrated a close resemblance to the human cauda equina. There were structural and vascular differences between spinal nerve roots and peripheral nerves that could contribute to differences in compression susceptibility between these two parts of the nervous system. The pressure transmission from the balloon to the nerve roots showed to have a high accuracy. The occlusion-pressures for the arterioles, capillaries and venules of the cauda equina were determined (Olmarker et al. 1989a). Arteriolar blood flow was stopped at a pressure close to the mean arterial blood pressure. Capillary blood flow was found to be dependent upon flow in the connected venules. The blood flow in some venules was found to be stopped at 5-10 mm Hg. However, venular occlusion pressures ranged from 5 to 60 mm Hg. Compression up to 200 mm Hg for 2 hours did not induce a "no-reflow" phenomenon when the compression was ended. However, a transient hyperemia was noted at all pressure/time relations studied, indicating nutritional deficit in the compressed segment during compression. Signs of edema were seen in nerve roots exposed to compression for 2 hours at either 50 or 200 mm Hg. The nutritional supply to the cauda equina was found to be impaired at low pressure levels (less than 10 mm Hg; Olmarker et al. 1990a). Diffusion from adjacent tissues with a better nutritional supply, including the cerebrospinal fluid, could thus not compensate completely for compression-induced effects on the transport of nutrients. However, a certain nutritional supply to the compressed segment was present even at 200 mm Hg compression. There were more pronounced effects on the nutritional supply induced by a rapid (0.05-0.1 sec.) than a slow (20 sec.) compression onset rate. Nutritional impairment was noted both within and outside the compressed nerve segment. An increase in vascular permeability was induced by compression at 50 mm Hg for 2 minutes (Olmarker et al. 1989b). The magnitude of this permeability increase was dependent on both the magnitude and the duration of compression. The permeability increase was more pronounced for the rapid than for the slow compression onset rate at all pressure/time relations studied. Reduction of muscle action potential (MAP) amplitude in tail muscles, after stimulation cranial to the compression zone, was induced by compression at 100 and 200 mm Hg for 2 hours (Olmarker et al. 1990b).(ABSTRACT TRUNCATED AT 400 WORDS)

Acute Disease↗