Spinal cord and nerve root blood flow in acute double level spinal stenosis

Qualitative and quantitative computed tomographic characteristics of the lumbosacral spine in German Shepherd military working dogs with versus without lumbosacral pain

Lumbosacral (LS) stenosis is a cause of lower back pain, loss of mission readiness, and early retirement in military working dogs (MWDs). Aims of the present two-part study were to evaluate a sample of German Shepherd MWDs using standard clinical criteria for LS pain, standard qualitative computed tomographic (CT) criteria for LS stenosis, novel quantitative CT criteria for LS stenosis, and novel behavioral classification criteria for LS pain. Data were retrieved from archives of a tertiary referral MWD hospital. Study 1 was a retrospective, observational, two-group design with a hypothesis that there would be a significant difference in the percentage of affected German Shepherd MWDs with multilevel stenosis (affecting ≥ 3 vertebrae) between LS pain groups, based on standard clinical and qualitative CT criteria. Study 2 was a retrospective, observational, cross-sectional, two- and three-group study design with a hypothesis that quantitative CT measurements would significantly differ between LS pain groups, assigned based on 3 classification systems. The 1st classification system used standard clinical criteria, while the 2nd and 3rd novel classifications included behavioral signs of LS pain. The following quantitative CT measures were recorded without knowledge of behavioral classification: vertebral foramen area, vertebral foramen volume, vertebral foramen fat area; and ratios of vertebral foramen area/vertebral body area (foramen area ratio), cranial vertebral foramen area/caudal vertebral foramen area (cranial:caudal foramen area ratio), and vertebral fat area/vertebral body area (fat area ratio). Study 1 findings did not support the hypothesis in that there was no significant difference in the percentage of dogs affected with multilevel stenosis between LS pain groups (P = 0.6567). Findings for study 2 supported the hypothesis in that dogs with LS pain were significantly more affected by multilevel stenosis (P = 0.0273). Significant differences occurred between LS pain groups in select vertebral locations for all measurements (P ≤ 0.05) except vertebral foramen area and vertebral foramen volume (P > 0.05). Comparisons using novel quantitative CT measures and behavioral classification criteria identified significant differences between LS pain groups that were not detected using standard qualitative criteria. These novel quantitative and behavioral classification criteria may be helpful in future research on causes for early retirement in German Shepherd MWDs.

Changes in nerve microcirculation following peripheral nerve compression

Following peripheral nerve compression, peripheral nerve microcirculation plays important roles in regulating the nerve microenvironment and neurotrophic substances, supplying blood and oxygen and maintaining neural conduction and axonal transport. This paper has retrospectively analyzed the articles published in the past 10 years that addressed the relationship between peripheral nerve compression and changes in intraneural microcirculation. In addition, we describe changes in different peripheral nerves, with the aim of providing help for further studies in peripheral nerve microcirculation and understanding its protective mechanism, and exploring new clinical methods for treating peripheral nerve compression from the perspective of neural microcirculation.

Real-time direct measurement of spinal cord blood flow at the site of compression: relationship between blood flow recovery and motor deficiency in spinal cord injury

STUDY DESIGN

An in vivo study to measure rat spinal cord blood flow in real-time at the site of compression using a newly developed device.

OBJECTIVES

To evaluate the change in thoracic spinal cord blood flow by compression force and to clarify the association between blood flow recovery and motor deficiency after a spinal cord compression injury.

SUMMARY OF BACKGROUND DATA

Until now, no real-time measurement of spinal cord blood flow at the site of compression has been conducted. In addition, it has not been clearly determined whether blood flow recovery is related to motor function after a spinal cord injury.

METHODS

Our blood flow measurement system was a combination of a noncontact type laser Doppler system and a spinal cord compression device. The rat thoracic spinal cord was exposed at the 11th vertebra and spinal cord blood flow at the site of compression was continuously measured before, during, and after the compression. The functioning of the animal's hind-limbs was evaluated by the Basso, Beattie and Bresnahan scoring scale and the frequency of voluntary standing. Histologic changes such as permeability of blood-spinal cord barrier, microglia proliferation, and apoptotic cell death were examined in compressed spinal cord tissue.

RESULTS

The spinal blood flow decreased on each increase in the compression force. After applying a 5-g weight, the blood flow decreased to <40% of the precompression level. Complete ischemia was reached using a 20-g weight. After decompression, the blood flow level in the 20-minute complete ischemia group was significantly higher than that in the 40-minute complete ischemia group. The hind-limb motor function in the 40-minute complete ischemia group was significantly less than that in the sham group (without compression), while no significant difference was observed between the 20-minute ischemia group and the sham group. In the 20-minute ischemia group, the rats whose spinal cord blood flow recovery was incomplete showed significant motor function loss compared with rats that completely recovered blood flow. Extensive breakdown of blood-spinal cord barrier integrity and the following microglia proliferation and apoptotic cell death were detected in the 40-minute complete ischemia group.

CONCLUSION

Duration of ischemia/compression and blood flow recovery of the spinal cord are important factors in the recovery of motor function after a spinal cord injury.

The relationship between the cross-sectional area of the cauda equina and the preoperative symptoms in central lumbar spinal stenosis

STUDY DESIGN

A cross-sectional registry and imaging cohort study.

OBJECTIVES

To study the association between typical symptoms and signs of central spinal stenosis and the minimum cross-sectional area (mCSA) of the cauda equina in patients subsequently undergoing surgery.

SUMMARY OF BACKGROUND DATA

Relations between mCSA and the symptoms of spinal stenosis have not been studied before.

SUBJECTS AND METHODS

The preoperative walking ability, pain in the leg(s) and back, duration of symptoms and quality of life in 82 men and women subsequently operated for spinal stenosis were related to the digitally determined CSA of the single most constricted level, mCSA of their lumbar spines.

RESULTS

A smaller mCSA was directly related to a shorter walking distance before claudication. A small mCSA meant more leg and back pain and a lower health-related quality of life. For those with a walking ability <100 m, the average mCSA was around 53 mm; whereas it was just <69 mm for those able to walk >500 m. The average mCSA did not differ depending on gender, age, or vertebral level.

CONCLUSIONS

The mCSA was a strong predictor of the preoperative walking ability, leg and back pain, and was directly related to the quality of life of patients with central spinal stenosis.

Femoral head blood flow reduction and hypercoagulability under 24 h megadose steroid treatment in pigs

The pathogenesis of corticosteroid-induced femoral head necrosis is assumed to be ischemia. The purpose of this study was to investigate the perfusion pattern of the femoral head and plasma coagulability during 24 h corticosteroid megadose treatment, as recommended by the National Acute Spinal Cord Injury Studies (NASCIS), in the awake big animal model. Blindedly, 9 animals underwent megadose methylprednisolone infusion (30 mg/kg intravenously as an initial bolus, followed by 5.4 mg/kg/h for further 23 h) while 9 animals served as placebo treated controls. Regional blood flow of the systematically subdivided femoral head, proximal femur, acetabulum, and soft tissue hip regions was investigated by the microsphere technique at steady state (phase 1), after the initial bolus infusion (phase 2), and after the completed treatment (phase 3). Plasma coagulability was examined in phases 1 and 3. Blood flow of the femoral head epiphysis and metaphyseal cancellous bone was unchanged after one hour of steroid infusion, but decreased after the completed treatment at 24 h in the experimental group. Femoral head blood flow reduction was global without a tendency to more pronounced blood flow decrease in any subregion. Plasma fibrinogen was significantly higher after 24 h of steroid infusion than in the placebo control group. 24 h high dose methylprednisolone treatment causes femoral head blood flow reduction and hypercoagulability of plasma in the normal awake immature pig. These findings may be pathogenetic factors in the early stage of steroid-induced osteonecrosis.

Spinal blood flow in 24-hour megadose glucocorticoid treatment in awake pigs

OBJECT

Because of the controversy regarding the benefits of 24-hour administration of methylprednisolone in patients with spinal cord injury (SCI), it is important to investigate its mechanism of action and side effects. This study was conducted to determine if high-dose methylprednisolone modulates neural and vertebral blood flow in an awake large-sized animal model without SCI.

METHODS

From a group of 18 immature female domestic pigs born to nine different litters, nine animals were randomly allocated to receive methylprednisolone treatment, whereas their nine female siblings served as controls. Drug or placebo was applied in a blinded fashion by a third person not involved in the study. The following treatment for SCI, as suggested by the North American Spinal Cord Injury Study, was administered to the awake pig: methylprednisolone (30 mg/kg of body weight) was infused into the jugular vein during a 15-minute period, followed by a 45-minute pause, and the infusion was maintained over a 23-hour period at a dose of 5.4 mg/kg body weight/hour. By means of the radioactive tracer microsphere technique, spinal cord blood flow (SCBF) was measured in the awake standing pig in the cerebrum, and in spinal gray and white matter, nerve roots, endplates, cancellous bone, cortical shell, and T12-L2 discs. Blood flow was measured before, 1 hour after initiation of infusion, and 24 hours postinfusion. Examination of blood flow in the neural and vertebral tissue samples, as well as of central hemodynamics, revealed no significant difference between the experimental and control groups, and this parity was maintained throughout the experimental phases.

CONCLUSIONS

In the awake pig model, 24-hour methylprednisolone treatment does not modulate cerebral or SCBF, nor does it increase the risk for vertebral osteonecrosis by producing vertebral ischemia.

Intraoperative measurements of nerve root blood flow during discectomy for lumbar disc herniation

STUDY DESIGN

Nerve root blood flow was intraoperatively measured before and after discectomy for lumbar disc herniation and compared with clinical features.

OBJECTIVE

To investigate the relation between nerve root blood flow changes and symptoms associated with lumbar disc herniation.

SUMMARY OF BACKGROUND DATA

Several authors have reported that recovery of intraneural blood flow, which restores the supply of oxygen and other nutrients to the nerve tissue, is strongly related to the rapid improvement of nerve function after discectomy for lumbar disc herniation. However, no previous study has quantitatively assessed blood flow in the human nerve root.

METHODS

Nerve root blood flow was monitored in 21 patients with lumbar disc herniation using laser Doppler flowmetry (ALF 21 N; ADVANCE, Tokyo, Japan) during discectomy. Possible correlations were investigated between the blood flow rates and the following clinical features: age, duration of sciatica, presence or absence of neurologic deficits, latency to pain relief, and morphology of herniated discs.

RESULTS

The blood flow rate in 16 patients who reported immediate relief after discectomy was much greater than in 5 patients whose pain was not relieved immediately after surgery (141% 8%, = 0.0364). The increase in the blood flow rate after discectomy was five times greater in patients with neurologic deficits than in patients without neurologic deficits (158% 36%, = 0.0638).

CONCLUSIONS

The results of the current study suggest that immediate relief from pain and resolution of neurologic deficits soon after surgery are the result of early recovery from nerve root ischemia after discectomy, and that ischemia caused by mechanical nerve root compression is mainly related to the mechanisms underlying sciatic pain production and neurologic deficits.

Blood flow measurement in experimental chronic cauda equina compression in dogs: changes in blood flow at various conditions

The purpose of this study was to present a simple method of measurement of blood flow in the nerve root, assess the reliability of this method, and examine the changes of blood flow in chronic cauda equina compression in an experimental setting. A total of 15 dogs were used to determine the blood flow of cauda equina in normal (n = 5), sham (n = 5), and 10 mm Hg compressed cauda equina for 1 week (n = 5). The speed of blood flow was calculated using a specially designed microscope supplied with a video camera. Blood flow in chronic 10 mm Hg compression decreased compared with the sham and normal groups. The kappa value was between 0.75 and 0.96. We conclude that this method might be useful for measurement of blood flow in the nerve root and for confirming the reduction in blood flow of compressed cauda equina.

Vertebral blood flow and bone mineral density during long-term corticosteroid treatment: An experimental study in immature pigs

STUDY DESIGN

Bone mineral density and regional blood flow were measured in pigs during long-term methylprednisolone treatment.

OBJECTIVES

To investigate possible changes in bone mineral density and vertebral blood flow during long-term glucocorticoid treatment.

SUMMARY OF BACKGROUND DATA

Steroid-induced vertebral osteonecrosis preferentially involves endplates and adjacent cancellous bone. The precise etiology of vertebral osteonecrosis during long-term glucocorticoid treatment is unknown.

METHODS

Twenty-four 10-week-old female Danish landrace sister pigs from 12 litters were treated in two groups. Twelve animals received oral methylprednisolone for 3 months at a daily dose of 100 mg. The 12 sister pigs received no steroid treatment and served as controls. Regional blood blow was measured by means of microspheres in predefined regions of the C6, T11, and L6 vertebrae. In vitro DEXA scanning of the L2-L4 vertebra was performed to assess bone mineral density.

RESULTS

Vertebral cancellous bone and endplate regional blood flow were decreased in the C6 and L6 vertebrae among corticosteroid-treated pigs compared with that of controls.- Width-adjusted lumbar vertebral bone mineral density (g/cm3) was unchanged, whereas projectional lumbar vertebral bone mineral density (g/cm2) was decreased in corticosteroid-treated pigs.

CONCLUSIONS

Long-term methylprednisolone treatment decreases vertebral bone blood flow mainly in cancellous bone and endplates. This may be an important factor in the pathogenesis of osteonecrosis secondary to glucocorticoid treatment. Lumbar vertebral bone mineral density was unchanged in growing pigs on long-term glucocorticoid treatment when expressed as volumetric bone density. The effect of glucocorticoid treatment on vertebral bone mineral density appears to depend on whether it is expressed as projectional (g/cm2) or volumetric bone mineral density (g/cm3). Vertebral and longbone growth was reduced during methylprednisolone treatment.