Effect of mechanical compression on the lumbar nerve root: localization and changes of intraradicular inflammatory cytokines, nitric oxide, and cyclooxygenase

Synapse involvement of the dorsal horn in experimental lumbar nerve root compression: a light and electron microscopic study

STUDY DESIGN

This study was aimed at investigating changes in the dorsal horn of the lumbar cord induced by mechanical compression using an in vivo model.

OBJECTIVE

To determine the effect of axonal flow disturbance in the dorsal horns induced by nerve root compression.

SUMMARY OF BACKGROUND DATA

Few studies have looked at changes of synapses within the dorsal horn caused by disturbance of axonal flow and the axon reaction as a result of mechanical compression of the dorsal root.

METHODS

In mongrel dogs, the 7th lumbar nerve root was compressed for 1 week, or 3 weeks using a clip. After intravenous injection of Evans blue albumin, they were observed under a fluorescence microscope for the purpose of clarifying the function of the blood-spinal cord barrier. Morphologic changes of the synapses in the dorsal horns secondary to the nerve fiber degeneration were examined by light and electron microscope. Changes on immuno-staining for substance P, calcitonin gene-related peptide, and somatostatin in the dorsal horn were also examined.

RESULTS

Light microscope observation conducted 1 week after compression of the nerve roots revealed Wallerian degeneration of the myelinated nerve in the dorsal horn, and fluorescence microscope observation of these areas demonstrated edema formation resulting from damage of the blood-spinal cord barrier. Three weeks after the compression, electron microscope observation revealed shrinkage of the axon terminals, ubiquitous presence of high electron density degeneration and presence of synapses whose contact with synapses was disrupted. Immuno-histochemical studies showed a marked decrease of substance P, calcitonin gene-related peptide, and somatostatin staining in substance gelatinosa with Wallerian degeneration after compression of nerve root.

CONCLUSION

It is important to recognize that compressive disturbance of the nerve roots caused Wallerian degeneration not only at the site of compression of nerve roots but also at the synapses of spinal cord dorsal horns.

Continuous positive airway pressure (CPAP) induces early nasal inflammation

STUDY OBJECTIVES

To assess whether noninvasive application of nCPAP is a mechanical stimulus inducing early nasal inflammation.

DESIGN

Prospective controlled animal study.

SETTING

University laboratory.

PATIENTS OR PARTICIPANTS

32 male Sprague-Dawley rats (250-300 g).

INTERVENTIONS

The rats were anesthetized and subjected to nCPAP=10 cm H2O and sham-CPAP through a mask for 3 h and 5 h (n=8 each).

MEASUREMENTS AND RESULTS

After nCPAP or sham, nasal scraping was carried out to detect neutrophils, and septum and dorsal nasal concha were excised to assess gene expression of inflammatory markers by real time PCR. Percentage of neutrophils in nucleated cells in the nasal scrapings was significantly (P = 0.006) higher after 5 h of nCPAP (3.51% +/- 0.73%; m +/- SEM) than in the sham group (1.12% +/- 0.39%). When compared with sham, the mRNA of macrophage inflammatory protein-2 (MIP-2) in nasal tissue was significantly overexpressed after both 3 h (2.28-fold +/- 0.43-fold; P = 0.034) and 5 h (5.56-fold +/-1.88-fold; P = 0.002) of nCPAP=10 cm H2O. No significant changes were found in the gene expressions of tumor necrosis factor-alpha, nerve growth factor and tachykinin-1 receptor.

CONCLUSIONS

The compression applied by nCPAP (10 cm H2O, 5 h) on the nasal wall of healthy rats is a mechanical stimulus that triggers an early inflammatory process mediated by MIP-2, resulting in neutrophil extravasation.

Asymmetric atrophy of multifidus muscle in patients with unilateral lumbosacral radiculopathy

STUDY DESIGN

Prospective case-control study of multifidus muscle atrophy in 39 patients with unilateral lumbosacral radiculopathy and lumbosacral disc herniation and 20 controls.

OBJECTIVE

To evaluate quantitatively the asymmetry of multifidus muscles in unilateral lumbosacral radiculopathy with disc herniation (herniated intervertebral disc; HIVD) by using magnetic resonance imaging (MRI).

SUMMARY OF BACKGROUND DATA

Histologic and morphologic changes of multifidus muscles have been reported in lumbosacral disc herniation, but there are few imaging studies on the changes of multifidus muscles in unilateral radiculopathy.

METHODS

Bilateral multifidus muscles in L3-L4, L4-L5, and L5-S1 levels were detected in fast spin-echo T1 axial MRI images. The total cross-sectional area (CSA) of multifidus muscles (TMA) and the density of pure muscle CSA (PMA) were measured by a computerized analysis program, and the ratios of PMA to TMA (PMA/TMA) and the PMA ratios of involved to uninvolved sides (IMA/UMA) were calculated. The patients were divided into 2 groups according to the electrodiagnosis results: a radiculopathy (RAD) group and an HIVD group without definite radiculopathy.

RESULTS

Fourteen patients had lumbosacral radiculopathies (RAD group) while 25 had no radiculopathy (HIVD group). No significant difference was found between the RAD and HIVD groups in TMA, PMA, and PMA/TMA. In terms of the criteria for the upper limit of IMA/UMA, 78.6% in the RAD group had an abnormal IMA/UMA ratio in at least 1 level, compared with 24% in the HIVD group and 10% in the control group. Thus, more cases with less muscle volume in the involved side were seen in the RAD group than in the HIVD and control groups.

CONCLUSION

Asymmetry of the multifidus muscles as seen in MRI was a useful finding to assess patients who had unilateral lumbosacral radiculopathy with HIVD. This may reflect the denervation of multifidus muscles in lumbosacral radiculopathy.

A case of nerve root heat injury induced by percutaneous laser disc decompression performed at an outside institution: technical case report

OBJECTIVE

In recent years, percutaneous laser disc decompression (PLDD) has become a routine surgical procedure because it can be performed under local anesthesia and is minimally invasive. However, there is a risk of nerve root and endplate injury owing to heat generated by laser irradiation during PLDD. We recently performed salvage surgery on a patient with heat injury to the L5 nerve root that developed after PLDD.

CLINICAL PRESENTATION

One month before presenting to our hospital, the patient underwent two sessions of PLDD for lumbar vertebral disk herniation at another institution. The patient developed worsening sciatica, as well as bowel and urinary problems after the PLDD.

INTERVENTION

We performed salvage surgery after PLDD. The intraoperative findings in the present case included carbon spots in the dura mater of the nerve root and a disc herniation strongly adherent to the nerve roots. These findings indicate that the area adjacent to the nerve roots was damaged by excessive heat during laser irradiation.

CONCLUSION

When salvage surgery is performed after a PLDD procedure, disc and nerve root injuries owing to laser heat energy must be considered.

Lumbar ligamentum flavum hypertrophy is due to accumulation of inflammation-related scar tissue

STUDY DESIGN

A histologic, biologic, and immunohistochemical assessment using human samples of the lumbar ligamentum flavum.

OBJECTIVE

To prove our hypothesis that hypertrophy of the ligamentum flavum is caused by accumulation of inflammation-related scar tissue.

SUMMARY OF BACKGROUND DATA

Lumbar spinal canal stenosis is 1 of the most common spinal disorders in elderly patients. Canal narrowing, in part, results from hypertrophy of the ligamentum flavum. The hypertrophy mechanism remains unclear. Based on our preliminary analyses, we have previously proposed that the hypertrophy may be due to accumulation of scar tissue in the ligament. Scar tissue is reported to develop after inflammation; however, there is no report, including our previous study, on inflammation in the ligamentum flavum. There is a need for an in-depth investigation of any relationship between inflammation and scar formation in the ligamentum flavum. If inflammation is related to hypertrophy, we may control/delay the hypertrophy by inhibiting the inflammation.

METHODS

Twenty-one ligamentum flavum samples were obtained for the histologic study. Trichrome and Verhoeff-van Gieson stains were used to assess the degree of fibrosis (scarring) and content of elastic fibers, respectively. Two ligamentum flavum samples, hypertrophied and thin control ligaments, were used for a global genetic assessment by oligonucleotide gene array technology with gene chips. Messenger ribonucleic acid expression of cyclooxygenase (COX)-2 was quantitatively measured from 16 ligamentum flavum samples using real-time reverse transcriptase polymerase chain reaction. Immunohistochemistry evaluated the cellular location of COX-2 in ligamentum flavum.

RESULTS

In the hypertrophied ligament, severe fibrosis (scarring) was observed in the entire area of the ligamentum flavum, and the severity of scarring showed a significant (r = 0.79; P < 0.0001) and positive linear correlation with ligamentum flavum thickness. Gene array results showed in both thin/control and hypertrophied ligaments expression of inflammation-related genes such as COX-2, tumor necrosis factor-alpha, and interleukin-1, 6, 8, and 15. Real-time polymerase chain reaction showed COX-2 messenger ribonucleic acid expression in all ligamentum flavum samples. Its expression showed weak positive linear correlation with the thickness of ligament. COX-2 was released from vascular endothelial cells in ligamentum flavum as per the immunohistochemical analysis.

CONCLUSIONS

Accumulation of fibrosis (scarring) causes hypertrophy of the ligamentum flavum. Inflammation-related gene expression is found in the ligamentum flavum. It might be possible to prevent the hypertrophy of ligamentum flavum with antiinflammatory drugs.

Motor neuron involvement in experimental lumbar nerve root compression: a light and electron microscopic study

STUDY DESIGN

The aim of this study is to investigate changes in lumbar motor neurons induced by mechanical nerve root compression using an in vivo model. This study is to investigate the changes of lumbar motor neuron induced by mechanical nerve root compression using in vivo model.

OBJECTIVES

The effect of axonal flow disturbance induced by nerve root compression was determined in lumbar motor neuron.

SUMMARY OF BACKGROUND DATA

The lumbar motor neuron should not be overlooked when considering the mechanism of weakness, so it is important to understand the morphologic and functional changes that occur in motor neurons of the spinal cord as a result of nerve root compression. However, few studies have looked at changes of neurons within the caused by disturbance of axonal flow, the axon reaction, chromatolysis, and cell death as a result of mechanical compression of the ventral root.

METHODS

In mongrel dogs, the seventh lumbar nerve root was compressed for 1 week, or 3 weeks using a clip. Morphologic changes of the motor neurons secondary to the axon reaction were examined by light and electron microscopy.

RESULTS

Light and electron microscopy showed central chromatolysis of motor neurons in the lumbar cord from 1 week after the start of compression. After 3 weeks, some neurons undergoing apoptosis were seen in the ventral horn.

CONCLUSION

It is important to be aware that, in patients with nerve root compression due to lumbar disc herniation or lumbar canal stenosis, dysfunction is not confined to degeneration at the site of compression but also extends to the motor neurons within the lumbar cord as a result of the axon reaction. Patients with weakness of lower leg should therefore be fully informed of the fact that these symptoms will not resolve immediately after surgery.