Shinichi Kikuchi

Lumbosacral transitional vertebrae and nerve-root symptoms

Transitional vertebrae (TV) may be one of the risk factors for lumbar disc herniation. It is not clear, however, whether the presence of TV can affect the development of nerve-root symptoms. Our aim was to clarify this relationship. A total of 501 patients with lumbar degenerative disease and nerve-root symptoms was studied in respect of their level and the presence of TV. As a control group, 508 patients without low back pain or nerve-root symptoms were studied to establish the incidence of TV. In patients with disc herniation, the incidence was statistically higher and the mean age lower in patients with TV than in those without. In most patients, the symptomatic disc level was just above the TV. Similarly, in those with stenosis of the spinal canal without spondylolisthesis, the symptomatic disc level was most commonly just above the TV.

Epidural application of nucleus pulposus enhances nociresponses of rat dorsal horn neurons.

Study Design. An electrophysiologic study to examine responses of dorsal horn neurons in the rat L5 spinal cord to noxious stimuli after disc herniation or application of the nucleus pulposus to the L5 nerve root. Objectives. To investigate the pathogenic role of nucleus pulposus in the neural mechanism underlying sciatica and low back pain. Summary of Background Data. Application of the nucleus pulposus to the lumbar nerve root induced morphologic, vascular, and functional changes in the nerve root, suggesting that some factors in the nucleus pulposus may be implicated in the pathogenesis of chronic changes. However, it has not been studied whether the epidural application of nucleus pulposus enhances nociresponses of pain-processing neurons in the superficial dorsal horn of the spinal cord. Methods. Extracellular recordings were made from the L5 dorsal horn neurons in 20 Wistar rats. The wide-dynamic-range (WDR) neurons activated by electric stimulation of the ipsilateral footpad of hindpaw were selected, and their responses to noxious and innocuous stimulation were examined after L5–L6 disc herniation onto the L5 nerve root (Group A) and application of the autologous nucleus pulposus (Group B) or fat tissues (Groups C and D). Results. The herniation of the nucleus pulposus (Group A) and application of the autologous nucleus pulposus (Group B) to the nerve root remarkably enhanced responses of WDR neurons to noxious stimuli for hours, whereas application of fat tissue scarcely enhanced nociresponses (Groups C and D). Conclusions. Results suggest that somewhat pathogenic factors in the nucleus pulposus may have a crucial role in the induction of hyperalgesia. This may help to elucidate the reason why a severe pain is sometimes induced without a visually identified protrusion.

Presence and Distribution of Antigen-antibody Complexes in the Herniated Nucleus Pulposus

STUDY DESIGN Herniated tissue was studied by immunohistochemistry in eight patients with lumbar disc herniation. The results were compared with those of control subjects. OBJECTIVE To assess the presence and distribution of possible antigen-antibody complexes in herniated disc tissue. SUMMARY OF BACKGROUND DATA It has been suggested that the nucleus pulposus may be recognized as a foreign-body by the immune system and that this will lead to secondary nerve root disturbance. Such immunologic events should be initiated by binding of antibodies to a specific antigen in the disc tissue. However, the presence of antigen-antibody complexes in the herniated disc tissue has not been assessed. METHODS Amplification of the peroxidase reaction produced in avidin-biotin-peroxidase complex immunostaining by diaminobenzidine was used to visualize antigen-antibody complexes in the herniated tissue. The authors used herniated tissue from eight patients with lumbar disc herniation and nucleus pulposus from five control subjects with nonlumbar disc herniation. Thin paraffin sections, prefixed in 4% paraformaldehyde, were incubated with anti-human IgG antibody to allow visualization of antigen-antibody complexes in the specimens. RESULTS A brown deposit, indicating antigen-antibody complexes, could be observed in the pericellular capsule in herniated disc tissue but not in control discs or in the residual discs of the herniation patients. CONCLUSION Antigen-antibody complexes seem to be commonly present in herniated disc tissue, but not in healthy discs. However, the pathophysiologic and clinical significance of this observation has to be elucidated further.

Prospective study of surgical treatment of degenerative spondylolisthesis: comparison between decompression alone and decompression with graf system stabilization.

Study Design. A prospective study of patients with degenerative spondylolisthesis who underwent decompression of the spine, with and without stabilization using the Graf system. Objectives. To assess the clinical result of decompression alone and decompression using the Graf system. Summary of Background Data. The clinical outcome of lumbar stabilization for degenerative spondylolisthesis remains uncertain. There is no prospective study of differences in clinical outcome between patients who undergo decompression alone and those who undergo decompression and stabilization using the Graf system. Methods. Eighty-eight patients with degenerative spondylolisthesis were included in this study. All patients reported leg symptoms. Decompression alone (Group D) was performed in 42 patients during a 5-year period from 1988 through 1992. Decompression and stabilization with the Graf system (Group G) was performed in 46 patients during a 4-year period from 1993 through 1996. There was no statistical difference regarding sex, the age at operation, compensable cases, and preoperative duration between two groups. The two groups were evaluated at follow-up examinations 1 and 3 years after surgery. The clinical results were evaluated for all patients by means of a 4-grade scale, visual analog scale, recurrence of leg symptoms, and persistent low back pain. The radiographic and clinical findings were examined by an independent investigator. Results. The results according to the 4-grade scale deteriorated with time in both groups. There was no statistical difference between the two groups in the 4-grade scale, visual analog scale, or recurrence of leg symptoms at each follow-up time. Persistent low back pain in Group G was significantly lower than that in Group D at both the 1- and 3-year follow-ups. Conclusions. Although lumbar Graf stabilization had no effect in preventing the recurrence of leg symptoms, there was a significant effect on reduction of low back pain at the 1- and 3-year follow-ups.

Experimental disc herniation: evaluation of the natural course.

Study Design. Changes in L7 nerve root conduction velocity and changes in appearance on magnetic resonance study of the L6‐L7 intervertebral disc in the dog were assessed for 2‐6 months after an experimental disc herniation was performed. Objectives. To assess the time‐related changes of nerve conduction velocity and magnetic resonance changes of the invertebral discs. Summary of Background Data. It is known that nucleus pulposus may induce nerve root morphologic and functional changes when applied epidurally. However, it is not known whether such changes are reversible. Methods. The spinal canal was opened by laminotomy of the upper part of the L7 lamina and the lower part of the L6 lamina on the left side. The L7 nerve root was gently retracted (sham) or the disc was punctured and injected with saline to produce herniation of the nucleus pulposus during the retraction time (herniation). After 1 day to 2 months, nerve root conduction velocity was determined by local electrical stimulation. Six dogs had the herniation or the sham procedure, and the L6‐L7 disc was studied by magnetic resonance imaging at various times up to 6 months after the procedure. Results. Decrease in nerve conduction velocity reached a maximum after 7 days and recovered to baseline level fully within 2 months. Although there was a clear reduction‐recovery pattern, the difference in conduction velocity compared with that of the sham group was statistically significant after only 7 days. Disc degeneration started in the herniated discs within 7 days after the herniation procedure. However, none of the experimentally induced disc herniations were visualized by magnetic resonance imaging 7 days after the procedure. In no case was there subsequent nerve root compression. In one case, disc protrusion was visible 6 months after the herniation procedure. Conclusions. The results demonstrate for the first time that nucleus pulposus‐induced nerve root injury reverses in 2 months and that it may be present without simultaneous nerve root compression, as confirmed by findings in magnetic resonance imaging. The previously described nucleus pulposus‐induced nerve root changes may therefore be of clinical importance, and experimental studies of these mechanisms will probably be relevant for expanded understanding of the pathophysiologic mechanism behind sciatica that is caused by disc herniation.

Nucleus pulposus-induced nerve root injury: relationship between blood flow and motor nerve conduction velocity.

OBJECTIVE It is well known that nucleus pulposus induces nerve root injury. The aim of this study was to assess the relationship between intraneural blood flow and motor nerve conduction velocity (NCV) after incision of the adjacent disc. METHODS A total of 65 dogs were used. A left hemilaminotomy was performed, the annulus fibrosus of the L6-L7 intervertebral disc was incised, and nucleus pulposus was gently pushed into the epidural space by saline solution injection. A left hemilaminotomy without disc incision was used as the sham operation. Seven dogs were used for incision and five dogs for sham treatment for each of the following time points: 1 day, 3 days, 1 week, 1 month, and 2 months of exposure. Five additional dogs were used to establish baseline data. Blood flow in the nerve root was measured in the left L7 nerve root with a tissue blood flowmeter, using an electrolytic hydrogen clearance method. Motor NCV over the exposed area of the nerve root was measured using a neurophysiological technique. RESULTS There was a reduction in blood flow in the nerve root after disc incision that began after 1 day and was maximal after 1 week. This reduction had resolved by 1 month, however. The motor NCV showed a reduction pattern similar to that for blood flow in the nerve root, but reduction did not begin until 3 days after disc incision and was not fully resolved until 2 months. CONCLUSION This study demonstrates that the reduction and recovery of motor NCV are related to, and preceded by, a reduction in blood flow in the nerve root. The data might provide important information regarding the basic pathophysiological mechanisms of nucleus pulposus-induced nerve root injury.

Combined laminectomy and thoracoscopic resection of dumbbell-type thoracic cord tumor.

Study Design. A study of five patients whose dumbbell or paraspinal tumors of the thoracic spine were managed by using thoracoscopic surgery is reported. Objectives. To report on the use of combined laminectomy and thoracoscopic resection for the management of dumbbell-type thoracic cord tumor. Summary of Background Data. Some posterior mediastinal tumors can be resected safely with video-assisted thoracic surgery. However, there are few reports on thoracoscopic resection of dumbbell and paraspinal tumors of the thoracic spine. Methods. Five patients who received treatment for thoracic spine dumbbell tumors and paraspinal tumors were studied retrospectively. Three patients had dumbbell tumors, and two had paraspinal tumors of the thoracic spine. Preoperative evaluation of each patient included plain chest radiography, magnetic resonance imaging, and computed tomography. All patients underwent total resection by means of a combined posteroanterior approach, with thoracoscopic surgery for dumbbell tumors and thoracoscopic surgery alone for paraspinal tumors. In all patients, a gross total resection was achieved with this approach. All patients were observed for a minimum of 3 years. Results. All patients regained their ability to walk 2 days after surgery, except for one patient who had a hemothorax. A gross total tumor resection, documented by magnetic resonance imaging, was performed on all patients. Follow-up imaging at 6 weeks, 1 year, 2 years, and 3 years after surgery did not show residual tumor or recurrence in any patient. To date, spinal instability has not developed in any patient. Conclusions. Combined laminectomy and thoracoscopic surgery may be a good alternative method for managing thoracic dumbbell tumors.

Localisation of the level of symptomatic cervical disc degeneration

There are many difficulties associated with the localisation of the symptomatic segment in patients presenting with cervicobrachial pain with no evidence of impaired conduction in the nerve root. Ancillary radiological investigations such as myelography, epidural phlebography, and epidural myelograms are of unreliable diagnostic value. However, discography can be of value if the technique described here is used. Infiltration of the cervical nerve root with local anaesthetic has also proved useful in the localisation of the symptomatic segment. The techniques used in cervical discography and infiltration of the nerve root are described and their reliability is assessed.

Chronic double-level cauda equina compression : An experimental study on the dog cauda equina with analyses of nerve conduction velocity

Study Design. Nerve conduction velocity was studied in the dog cauda equina subjected to chronic double‐level compression. Objectives. To analyze the effects of chronic double‐level cauda equina compression. Summary of Background Data. Double‐level cauda equina compression produces more symptoms in patients and more changes in acute experimental set‐ups than does single‐level compression. However, there have been no controlled, experimental studies on chronic double‐level compression. Methods. A total of 20 dogs were anesthetized. Two balloons were placed under the lamina of the seventh lumbar vertebra and the first sacral vertebra, respectively. One week (10 mm Hg, n = 5; 0 mm Hg, n = 5) and 1 month (10 mm Hg, n = 5; 0 mm Hg, n = 5) after inflation with a viscous substance, nerve conduction velocity was studied by local electrical stimulation and recording of muscle action potentials in the tail muscles. Results. Nerve conduction velocity was determined over the cranial balloon, the caudal balloon, and both balloons. The data were similar for all three recordings. After 1 week there was a significant reduction in nerve conduction velocity induced by 10 mm Hg, compared with that induced by 0 mm Hg, which showed normal conditions. However, after 1 month this initial reduction in nerve conduction velocity had recovered partially. The reduction was similar to that described for single‐level compression in a previous study in which the same compression model was used. Conclusions. Unlike the acute situation, chronic double‐level compression does not induce more changes than single‐level compression after 1 week, although the recovery after 1 month of compression is less complete after double‐level compression. This less complete recovery may be a result of an adaptation of the nerve tissue and the vascularization of the cauda equina nerve roots to the applied pressure.

Nerve vasculature changes induced by serotonin under chronic cauda equina compression.

Study Design. An analysis of nerve vascular changes in nerve roots induced by serotonin in chronically compressed nerve roots. Objectives. To assess the hypotheses that serotonin might have a vasoconstrictive effect in chronically compressed nerve roots. Summary of Background Data. The 5-hydroxytryptamine 2A receptor is involved in serotonin-induced activation or sensitization of sensory nerve terminals. Serotonin exerts complex effects on pain and hyperalgesia through various receptor subtypes located at various levels of the pain transmission system. Serotonin induces endothelium-dependent contraction in vascular diseases. However, there is no knowledge regarding a response of nerve vasculature induced by serotonin in chronically compressed nerve roots. Methods. A total of 45 dogs were used. A plastic balloon was placed under the lamina L7 and inflated to 10 mm Hg and left for 1 week. Four experimental groups were used: no operation (Group A, n = 15), the balloon was placed under the lamina but not inflated (Group B, n = 10), the balloon was inflated to 10 mm Hg for 1 week and the pressure was released just before the measurement (Group C, n = 10), and the balloon was inflated to 10 mm Hg for 1 week and inflation was maintained during the measurements (Group D, n = 10). The blood vessels of the second or third sacral nerve were defined after an intra-arterial injection of 0.5 &mgr;mol/L or 1.0 &mgr;mol/L serotonin using a specially designed operation microscope equipped with a video camera. In all groups 0.5 &mgr;mol/L serotonin (each group, n = 5) or 1.0 &mgr;mol/L serotonin (each group, n = 5) was injected. In Group A (n = 5) saline was injected. The measurements of diameter of observed blood vessels and blood flow index were performed on video recordings. All statistical assessments were performed by Wilcoxon signed-ranks test and Fisher’s PLSD. Results. In Group A, the diameter of blood vessels and blood flow did not change after administration of saline. In the noncompression groups (Groups A and B) the diameter of blood vessels and blood flow increased after injection of 0.5 &mgr;mol/L serotonin. In compression groups (Groups C and D) the blood vessels contracted after injecting 0.5 &mgr;mol/L serotonin and blood flow decreased. There was a significant difference in the diameter of blood vessels and blood flow between noncompression and compression groups (P < 0.01). There was no difference regarding diameter of blood vessels between releasedcompression (Group C) and maintained compression during measurement group (Group D). In all groups blood vessels contracted and blood flow decreased after injecting 1.0 &mgr;mol/L. In electron microscopic observation tight junction of endothelial cells was destroyed in chronically compression nerve roots. Discussion. The present study demonstrated that serotonin had a vasodilative effect on the intact nerve roots, whereas there was a vasoconstrictive effect to the chronically compressed nerve roots. There was no difference in the diameter of blood vessels between released compression and maintained compression during measurement group. Results suggested that dysfunction of endothelial cells induced by serotonin rather than mechanical compression itself might lead to contraction of blood vessels under chronic compression. Conclusion. Serotonin had a vasoconstrictive effect on the chronically compressed nerve roots.