Magnetic resonance angiography of collateral blood supply to spinal cord in thoracic and thoracoabdominal aortic aneurysm patients

Postsurgical dural supply to the spinal cord arteriovenous malformation in spinal arteriovenous metameric syndrome

Dural supply from the external carotid system in cerebral arteriovenous malformations (AVMs) is well known, but actual angiographic evidence of dural supply to spinal cord AVMs (SCAVMs) has not been reported. Here, we report a case of dural supply to the conus SCAVM in the spinal arteriovenous metameric syndrome segment 25-30. Thirteen years after spinal surgery (T12-L2 laminoplasty), spinal angiography showed multiple dural supplies from the dorsal somatic branches, prelaminar arteries, and radiculomeningeal arteries to the SCAVM at the level of the previous spinal surgery. To the best of our knowledge, this is the first reported case with dural supply to the spinal cord. This case demonstrates that the extradural and extraspinal branches can supply the spinal cord in rare instances of spinal dural adhesions following repeated hemorrhages and surgical intervention under a metameric link background.

Comparison of single- and multistage strategies during fenestrated-branched endovascular aortic repair of thoracoabdominal aortic aneurysms

OBJECTIVE

The aim of this study was to compare outcomes of single or multistage approach during fenestrated-branched endovascular aortic repair (FB-EVAR) of extensive thoracoabdominal aortic aneurysms (TAAAs).

METHODS

We reviewed the clinical data of consecutive patients treated by FB-EVAR for extent I to III TAAAs in 24 centers (2006-2021). All patients received a single brand manufactured patient-specific or off-the-shelf fenestrated-branched stent grafts. Staging strategies included proximal thoracic aortic repair, minimally invasive segmental artery coil embolization, temporary aneurysm sac perfusion and combinations of these techniques. Endpoints were analyzed for elective repair in patients who had a single- or multistage approach before and after propensity score adjustment for baseline differences, including the composite 30-day/in-hospital mortality and/or permanent paraplegia, major adverse event, patient survival, and freedom from aortic-related mortality.

RESULTS

A total of 1947 patients (65% male; mean age, 71 ± 8 years) underwent FB-EVAR of 155 extent I (10%), 729 extent II (46%), and 713 extent III TAAAs (44%). A single-stage approach was used in 939 patients (48%) and a multistage approach in 1008 patients (52%). A multistage approach was more frequently used in patients undergoing elective compared with non-elective repair (55% vs 35%; P < .001). Staging strategies were proximal thoracic aortic repair in 743 patients (74%), temporary aneurysm sac perfusion in 128 (13%), minimally invasive segmental artery coil embolization in 10 (1%), and combinations in 127 (12%). Among patients undergoing elective repair (n = 1597), the composite endpoint of 30-day/in-hospital mortality and/or permanent paraplegia rate occurred in 14% of single-stage and 6% of multistage approach patients (P < .001). After adjustment with a propensity score, multistage approach was associated with lower rates of 30-day/in-hospital mortality and/or permanent paraplegia (odds ratio, 0.466; 95% confidence interval, 0.271-0.801; P = .006) and higher patient survival at 1 year (86.9±1.3% vs 79.6±1.7%) and 3 years (72.7±2.1% vs 64.2±2.3%; adjusted hazard ratio, 0.714; 95% confidence interval, 0.528-0.966; P = .029), compared with a single stage approach.

CONCLUSION

Staging elective FB-EVAR of extent I to III TAAAs was associated with decreased risk of mortality and/or permanent paraplegia at 30 days or within hospital stay, and with higher patient survival at 1 and 3 years.

Simultaneous Endovascular Repair Is Not Associated With Increased Risk for Thoracic and Abdominal Aortic Pathologies: Early and Midterm Outcomes

Coexisting multilevel aortic pathologies were caused by atherosclerosis and hypertension and presented in a small subgroup of patients. Endovascular repair is a safe and effective treatment for a variety of aortic pathologies. However, fewer small series and cases were reported using simultaneous thoracic endovascular repair (TEVAR) and endovascular aneurysm repair (EVAR) for both aortic segments. To determine the outcomes of simultaneous and separately TEVAR and EVAR treating for multilevel aortic pathologies. Between 2010 and 2020, 31 patients and 22 patients were treated by one-staged and two-staged repair, respectively at a single center. All patients had the concomitant thoracic and abdominal aortic disease (aortic dissection, aneurysms, and penetrating aortic ulcers). Compared with the patients with two-staged aortic repair, the one-staged repair patients were older (mean age, 68 vs. 57 years; P < 0.001) and had a larger preoperative maximal aortic diameter (67.03 ± 10.65 vs. 57.45 ± 10.36 mm; p = 0.002). The intraoperative and postoperative outcomes show that the procedure times and length of hospital stay (LOS) were longer in the two-staged group. There is no significant difference in postoperative complications between the two groups. In the follow up, the freedom from re–intervention and the mean survival rate for the one-staged group were 100 vs. 100%, 92.4 vs. 95%, and 88 vs. 88% at one, two, and 5 years, respectively, whereas the mean survival rate for the two-staged group was 86.4 vs. 90.5%, 87 vs. 90.5%, and 76 vs. 84% at one, two, and 5 years, respectively, all with no statistical difference. Combined TEVAR and EVAR can be performed successfully with minimal morbidity and mortality. The one-staged repair was not associated with the increased risk for multilevel aortic pathologies treatment.

Prior Infrarenal Aortic Surgery is Not Associated with Increased Risk of Spinal Cord Ischemia Following Thoracic Endovascular Aortic Repair and Complex Endovascular Aortic Repair

OBJECTIVES

Patients with prior infrarenal aortic intervention represent an increasing demographic of patients undergoing thoracic endovascular aortic repair (TEVAR) and/or complex EVAR. Studies have suggested that prior abdominal aortic surgery is a risk factor for spinal cord ischemia (SCI). However, these results are largely based on single-center experiences with limited multi-institutional and national data assessing clinical outcomes in these patients. The objective of this study was to evaluate the effect of prior infrarenal aortic surgery on SCI.

METHODS

The Society for Vascular Surgery Vascular Quality Initiative database was retrospectively reviewed to identify all patients ≥18 years old undergoing TEVAR/complex EVAR from January 2012 to June 2020. Patients with previous thoracic or suprarenal aortic repairs were excluded. Baseline and procedural characteristics and postoperative outcomes were compared by group: TEVAR/complex EVAR with or without previous infrarenal aortic repair. The primary outcome was postoperative SCI. Secondary outcomes included postoperative hospital length of stay (LOS), bowel ischemia, renal ischemia, and 30-day mortality. Multivariate regression was used to determine independent predictors of postoperative SCI. Additional analysis was performed for patients undergoing isolated TEVAR.

RESULTS

A total of 9506 patients met the inclusion criteria: 8691 (91.4%) had no history of infrarenal aortic repair and 815 (8.6%) had previous infrarenal aortic repair. Patients with previous infrarenal repair were older with an increased prevalence of chronic kidney disease (p=0.001) and cardiovascular risk factors including hypertension, chronic obstructive pulmonary disease, and smoking history (p<0.001). These patients presented with larger maximal aortic diameters (6.06±1.47 cm versus 5.15±1.76 cm; p<0.001) and required more stent grafts (p<0.001) with increased intraoperative blood transfusion requirements (p<0.001), and longer procedure times (p<0.001). Univariate analysis demonstrated no difference in postoperative SCI, postoperative hospital LOS, bowel ischemia, or renal ischemia between the two groups. Thirty-day mortality was significantly higher in patients with prior infrarenal repair (p=0.001). On multivariate regression, prior infrarenal aortic repair was not a predictor of postoperative SCI, while aortic dissection (odds ratio [OR] 1.65; 95% confidence interval [CI] 1.26-2.16, p<0.001), number of stent grafts deployed (OR 1.45; 95% CI 1.30-1.62, p<0.001), and units of packed red blood cells transfused intraoperatively (OR 1.33; 95% CI 1.03-1.73, p=0.032) were independent predictors of SCI.

CONCLUSIONS

Although TEVAR/complex EVAR patients with prior infrarenal aortic repair constituted a sicker cohort with higher 30-day mortality, the rate of SCI was comparable to patients without prior repair. Previous infrarenal repair was not associated with risk of SCI.

Ischemic spinal cord injury - experimental evidence and evolution of protective measures

BACKGROUND

Paraplegia remains one of the most devastating complications of descending and thoracoabdominal aortic repair. The aim of this review is to outline the current state of art in the rapidly developing field of spinal cord injury (SCI) research.

METHODS

A review of PubMed and Web of Science databases was performed using the following terms and their combinations: spinal cord, injury, ischemia, ischemia-reperfusion, ischemic spinal cord injury, paraplegia, paraparesis. Articles published before July 2019 were screened and included if considered relevant.

RESULTS

The review focuses on the topic of SCI and the developments concerning methods of monitoring, diagnostics and prevention of SCI.

CONCLUSIONS

Translation of novel technologies from bench to bedside and into everyday clinical practice is challenging, however each of the developing areas hold great promise in SCI prevention.

3D Digital Anatomic Angioarchitecture of the Rat Spinal Cord: A Synchrotron Radiation Micro-CT Study

Comprehensive analysis of 3D angioarchitecture within the intact rat spinal cord remains technically challenging due to its sophisticated anatomical properties. In this study, we aim to present a framework for ultrahigh-resolution digitalized mapping of the normal rat spinal cord angioarchitecture and to determine the physiological parameters using synchrotron radiation micro-CT (SRμCT). Male SD rats were used in this ex vivo study. After a proportional mixture of contrast agents perfusion, the intact spinal cord covered the cervical spinal from the upper of the 1st cervical vertebra to the 5th lumbar vertebra was harvested and cut into proper lengths within three distinct regions: Cervical 3–5 levels, Thoracic 10–12 levels, Lumbar 3–5 levels spinal cord and examined using SRμCT. This method enabled the replication of the complicated microvasculature network of the normal rat spinal cord at the ultrahigh-resolution level, allowing for the precise quantitative analysis of the vascular morphological difference among cervical, thoracic and lumbar spinal cord in a 3D manner. Apart from a series of delicate 3D digital anatomical maps of the rat spinal cord angioarchitecture ranging from the cervical and thoracic to the lumbar spinal cord were presented, the 3D reconstruction data of SRμCT made the 3D printing of the spinal cord targeted selected microvasculature reality, that possibly provided deep insight into the nature and role of spinal cord intricate angioarchitecture. Our data proposed a new approach to outline systematic visual and quantitative evaluations on the 3D arrangement of the entire hierarchical microvasculature of the normal rat spinal cord at ultrahigh resolution. The technique may have great potential and become useful for future research on the poorly understood nature and function of the neurovascular interaction, particularly to investigate their pathology changes in various models of neurovascular disease.

SRμCT Reveals 3D Microstructural Alterations of the Vascular and Neuronal Network in a Rat Model of Chronic Compressive Thoracic Spinal Cord Injury

The complex pathology of chronic thoracic spinal cord compression involves vascular and neuroarchitectural repair processes that are still largely unknown. In this study, we used synchrotron radiation microtomography (SRμCT) to quantitatively characterize the 3D temporal-spatial changes in the vascular and neuronal network after chronic thoracic spinal cord compression in order to obtain further insights into the pathogenesis of this disease and to elucidate its underlying mechanisms. Direct 3D characterization of the spinal cord microvasculature and neural microstructure of the thoracic spinal cord was successfully reconstructed. The significant reduction in vasculature and degeneration of neurons in the thoracic spinal cord visualized via SRμCT after chronic compression were consistent with the changes detected by immunofluorescence staining. The 3D morphological measurements revealed significant reductions of neurovascular parameters in the thoracic spinal cord after 1 month of compression and became even worse after 6 months without relief of compression. In addition, the distinct 3D morphological twist and the decrease in branches of the central sulcal artery after chronic compression vividly displayed that these could be the potential triggers leading to blood flow reduction and neural deficits of the thoracic spinal cord. Our findings propose a novel methodology for the 3D analysis of neurovascular repair in chronic spinal cord compression, both qualitatively and quantitatively. The results indicated that compression simultaneously caused vascular dysfunction and neuronal network impairment, which should be acknowledged as concurrent events after chronic thoracic spinal cord injury. Combining neuroprotection with vasoprotection may provide promising therapeutic targets for chronic thoracic spinal cord compression.

Analysis of spinal cord blood supply combining vascular corrosion casting and fluorescence microsphere technique: A feasibility study in an aortic surgical large animal model

INTRODUCTION

Spinal cord ischemia after cardiovascular interventions continues to be a devastating problem in modern surgery. The role of intraspinal vascular networks and anterior radiculomedullary arteries (ARMA) in preventing spinal cord ischemia is poorly understood.

MATERIALS AND METHODS

Landrace pigs (n = 30, 35.1 ± 3.9 kg) underwent a lateral thoracotomy. Fluorescent microspheres were injected into the left atrium and a reference sample was aspirated from the descending aorta. Repeated measurements of spinal cord and renal cortical blood flow from the left and right kidneys with three different microsphere colors in five pigs were taken to validate reproducibility. Spinal cord blood flow to the upper thoracic (T1-T4), mid-thoracic (T5-T8), lower thoracic (T9-T13), and lumbar (L1-L3) levels were determined. After euthanasia, we carried out selective vascular corrosion cast and counted the left and right ARMAs from levels T1-T13.

RESULTS

Blood flow analysis of the left and right kidneys revealed a strong correlation (r = .94, p < .001). We detected more left than right ARMAs, with the highest prevalence at T4 (p < .05). The mean number of ARMAs was 8 ± 2. Their number in the upper thoracic region ranged from 2 to 7 (mean of 5 ± 1), while in the lower thoracic region they ranged from 0 to 5 (mean of 3 ± 1 [p < .001]).

CONCLUSIONS

This study shows that combining fluorescence microsphere technique and vascular corrosion cast is well suited for assessing the blood flow and visualizing the arteries at the same time.

Arteriogenesis of the Spinal Cord-The Network Challenge

Spinal cord ischemia (SCI) is a clinical complication following aortic repair that significantly impairs the quality and expectancy of life. Despite some strategies, like cerebrospinal fluid drainage, the occurrence of neurological symptoms, such as paraplegia and paraparesis, remains unpredictable. Beside the major blood supply through conduit arteries, a huge collateral network protects the central nervous system from ischemia—the paraspinous and the intraspinal compartment. The intraspinal arcades maintain perfusion pressure following a sudden inflow interruption, whereas the paraspinal system first needs to undergo arteriogenesis to ensure sufficient blood supply after an acute ischemic insult. The so-called steal phenomenon can even worsen the postoperative situation by causing the hypoperfusion of the spine when, shortly after thoracoabdominal aortic aneurysm (TAAA) surgery, muscles connected with the network divert blood and cause additional stress. Vessels are a conglomeration of different cell types involved in adapting to stress, like endothelial cells, smooth muscle cells, and pericytes. This adaption to stress is subdivided in three phases—initiation, growth, and the maturation phase. In fields of endovascular aortic aneurysm repair, pre-operative selective segmental artery occlusion may enable the development of a sufficient collateral network by stimulating collateral vessel growth, which, again, may prevent spinal cord ischemia. Among others, the major signaling pathways include the phosphoinositide 3 kinase (PI3K) pathway/the antiapoptotic kinase (AKT) pathway/the endothelial nitric oxide synthase (eNOS) pathway, the Erk1, the delta-like ligand (DII), the jagged (Jag)/NOTCH pathway, and the midkine regulatory cytokine signaling pathways.

Artery of Adamkiewicz: a meta-analysis of anatomical characteristics

PURPOSE

The artery of Adamkiewicz (AKA) provides the major blood supply to the anterior thoracolumbar spinal cord and iatrogenic injury or inadequate reconstruction of this vessel during vascular and endovascular surgery can result in postoperative neurological deficit due to spinal cord ischemia. The aim of this study was to provide comprehensive data on the prevalence and anatomical characteristics of the AKA.

METHODS

An extensive search was conducted through the major electronic databases to identify eligible articles. Data extracted included study type, prevalence of the AKA, gender, number of AKA per patient, laterality, origin based on vertebral level, side of origin, morphometric data, and ethnicity subgroups.

RESULTS

A total of 60 studies (n = 5437 subjects) were included in the meta-analysis. Our main findings revealed that the AKA was present in 84.6% of the population, and patients most frequently had a single AKA (87.4%) on the left side (76.6%) originating between T8 and L1 (89%).

CONCLUSION

As an AKA is present in the majority of the population, caution should be taken during vascular and endovascular surgical procedures to avoid injury or ensure proper reconstruction. All surgeons operating in the thoracolumbar spinal cord should have a thorough understanding of the anatomical characteristics and surgical implications of an AKA.

Thoracoabdominal Aortic Aneurysm in a Patient With Takayasu Arteritis

We report a successful treatment of extent III thoracoabdominal aortic aneurysm complicated with stenoocclusive visceral and iliac arteries in a 27-year-old woman with Takayasu arteritis. Distal first technique and a bypass to the left femoral artery was performed to maintain the pelvic circulation for spinal cord protection as the patient had right external iliac artery occlusion and left common iliac artery occlusion. In addition, we performed endarterectomy of the visceral branch orifices during the extent III thoracoabdominal aortic aneurysm repair. The patient recovered without spinal cord injury and serum creatinine improved from 1.22 to 0.53 mg/dL.

A Systematic Review of the Use of Biochemical Markers in the Assessment of Spinal Cord Ischemia in Thoracoabdominal Aortic Aneurysm Repair

Introduction:

Despite advances in perioperative critical care and surgical technique, spinal cord ischemia remains a devastating complication of thoracic and thoracoabdominal aortic aneurysm repair. Biochemical markers present in peripheral blood and cerebrospinal fluid (CSF) may be useful in assessing spinal cord injury. We systematically analyze and report the role of all reported biochemical markers that have been used in assessing and diagnosing spinal cord ischemia in thoracic and thoracoabdominal aortic aneurysm repair.

Methods:

Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were used for this review. Published literature was searched to identify all studies reporting on the use of biochemical markers in thoracoabdominal aortic aneurysm repair in the assessment of spinal cord ischemia. Marker-specific and patient-specific data were extracted from all studies and where possible, subgroup analysis was performed on marker-specific data sets.

Results:

Fourteen studies of 321 patients undergoing thoracic and thoracoabdominal aortic aneurysm repair were eligible for further analysis. Seven distinct biochemical markers were used in both CSF and blood samples: S100B proteins (S100B), neurone-specific enolase, lactate dehydrogenase, glial fibrillary acidic protein (GFAp), neurofilament triplet protein (NFL) and Tau protein, and glucose. There was substantial evidence demonstrating the heightened levels of S100, NFL, and GFAp in CSF in patients with spinal cord ischemia. There is however, wide variability in the correlation of the same 6 biochemical markers in peripheral blood and spinal cord ischemia.

Conclusions:

In patients with spinal cord injury, dramatic rises occur with S100B, NFL, and GFAp in CSF. However, further work is needed if biochemical markers are to impact on the future of thoracoabdominal aortic aneurysm repair.

Advantages of 70-kV CT Angiography for the Visualization of the Adamkiewicz Artery: Comparison with 120-kV Imaging

BACKGROUND AND PURPOSE

Preprocedural identification of the Adamkiewicz artery is crucial in patients with aortic diseases. This study aimed to compare 70-kV CTA with conventional 120-kV CTA for the identification of the Adamkiewicz artery, examining differences in radiation dose and image quality.

MATERIALS AND METHODS

We retrospectively analyzed 2 equal groups of 60 patients who had undergone 70-kV or 120-kV CTA to detect the Adamkiewicz artery before aortic repair. Size-specific dose estimate, the CT number of the aorta, and the contrast-to-noise ratio of the anterior spinal artery to the spinal cord were recorded. Furthermore, detectability of the Adamkiewicz artery was evaluated by using a 4-point continuity score (3, definite to 0, undetectable).

RESULTS

There was significantly lower radiation exposure with 70-kV CTA than 120-kV CTA (median size-specific dose estimate, 23.1 versus 61.3 mGy, respectively; P < .001). CT number and contrast-to-noise ratio were both significantly higher in the 70-kV CTA group than the 120-kV group (999.1 HU compared with 508.7 HU, and 5.6 compared with 3.4, respectively; P < .001 for both). Detectability of the Adamkiewicz artery was not impaired in the 70-kV CTA group (90.0% versus 83.3% in the 120-kV group, P = .28). Moreover, the Adamkiewicz artery was detected with greater confidence with 70-kV CTA, reflected by a significantly superior continuity score (median, 3) compared with 120-kV CTA (median, 2; P = .001).

CONCLUSIONS

Seventy-kilovolt CTA has substantial advantages for the identification of the Adamkiewicz artery before aortic repair, with a significantly lower radiation exposure and superior image quality than 120-kV CTA.

Development of Collaterals to the Spinal Cord after Endovascular Stent Graft Repair of Thoracic Aneurysms

OBJECTIVES

In thoracic and thoraco-abdominal aortic aneurysm repair, spinal cord injury (SCI) is devastating. Detection of the Adamkiewicz artery might be important for preventing SCI. Although thoracic endovascular stent grafts often occlude the segmental artery, the incidence of SCI in thoracic endovascular aortic repair is thought to be low compared with open repair. This study aimed to evaluate how the Adamkiewicz artery is supplied after segmental arteries are occluded by stent grafts.

METHODS

From March 2007 to August 2015, 32 patients were enrolled whose segmental arteries that were connected to the Adamkiewicz arteries were occluded by stent grafts. Segmental arteries, Adamkiewicz arteries, collateral circulation into the Adamkiewicz arteries, and anterior spinal arteries were pre- and post-operatively evaluated by computed tomography angiography.

RESULTS

Post-operatively, Adamkiewicz arteries were detected in 24 (75%) patients, except for two patients with paraplegia and six without paraplegia. Post-operative Adamkiewicz arteries were the same as pre-operative Adamkiewicz arteries, except for one Adamkiewicz artery that was located at two vertebral levels below the pre-operative level. SCI occurred in two (6.3%) patients. The distribution of feeding arteries into the Adamkiewicz artery post-operatively was divided into three patterns as follows: a segmental artery below the distal landing zone of the stent graft (53%), branches of the left subclavian artery (33%), and a branch of the left external iliac artery (13%).

CONCLUSIONS

The length of the stent graft should be as short as possible. Blood supply to the left subclavian artery should be maintained because segmental arteries below the segmental artery occluded by the stent graft and branches of the left subclavian artery can become collaterals post-operatively.

Modification of a Standard Thoracoabdominal Incision to Preserve Collaterals to Adamkiewicz Artery

We report a case of a 35-year-old male who underwent thoracoabdominal aortic repair of a chronic dissecting aortic aneurysm, Crawford extent II. Preoperative computed tomography showed thrombosis of almost all intercostal arteries. Precise diagnostic assessment demonstrated the Adamkiewicz artery originating from the left lateral thoracic artery and subscapular artery, which would have been at risk after using a standard Stoney's incision, thus potentially causing paraplegia or paraparesis due to spinal cord ischemia. We modified the lateral thoracic incision anteriorly and successfully preserved the collateral arteries without impairing the spinal cord function.

Is There Any Benefit of Neuromonitoring during Descending and Thoracoabdominal Aortic Aneurysm Repair?

Objective

Paraplegia remains the most feared and a devastating complication after descending and thoracoabdominal aneurysm operative repair (DTA and TAAAR). Neuromonitoring, particularly use of motor-evoked potentials (MEPs), for this surgery has gained popularity. However, ambiguity remains regarding its use and benefit. We systematically reviewed the literature to assess the benefit and applicability of neuromonitoring in DTA and TAAAR.

Methods

Electronic searches were performed on 4 major databases from inception until February 2014 to identify relevant studies. Eligibility decisions, method quality, data extraction, and analysis were performed according to predefined clinical criteria and end points.

Results

Among the studies matching our inclusion criteria, 1297 patients had MEP monitoring during DTA and TAAAR. In-hospital mortality was low (6.9% ± 3.6). Immediate neurological deficit was low (3.5% ± 2.6). In one third of patients (30.4% ± 14.2), the MEPs dropped below threshold, which were 30.4% and 29.4% with threshold levels of 75% and 50%, respectively. A range of surgical techniques were applied after reduction in MEPs. Most patients whose MEPs dropped and remained below threshold had immediate permanent neurological deficit (92.0% ± 23.6). Somatosensory-evoked potentials were reported in one third of papers with little association between loss of somatosensory-evoked potentials and permanent neurological deficit (16.7% ± 28.9%).

Conclusions

We demonstrate that MEPs are useful at predicting paraplegia in patients who lose their MEPs and do not regain them intraoperatively. To date, there is no consensus regarding the applicability and use of MEPs. Current evidence does not mandate or support MEP use.

Ginsenoside Rd attenuates mitochondrial permeability transition and cytochrome C release in isolated spinal cord mitochondria: involvement of kinase-mediated pathways

Ginsenoside Rd (Rd), one of the main active ingredients in Panax ginseng, has multifunctional activity via different mechanisms and neuroprotective effects that are exerted probably via its antioxidant or free radical scavenger action. However, the effects of Rd on spinal cord mitochondrial dysfunction and underlying mechanisms are still obscure. In this study, we sought to investigate the in vitro effects of Rd on mitochondrial integrity and redox balance in isolated spinal cord mitochondria. We verified that Ca²⁺ dissipated the membrane potential, provoked mitochondrial swelling and decreased NAD(P)H matrix content, which were all attenuated by Rd pretreatment in a dose-dependent manner. In contrast, Rd was not able to inhibit Ca²⁺ induced mitochondrial hydrogen peroxide generation. The results of Western blot showed that Rd significantly increased the expression of p-Akt and p-ERK, but had no effects on phosphorylation of PKC and p38. In addition, Rd treatment significantly attenuated Ca²⁺ induced cytochrome c release, which was partly reversed by antagonists of Akt and ERK, but not p-38 inhibitor. The effects of bisindolylmaleimide, a PKC inhibitor, on Rd-induced inhibition of cytochrome c release seem to be at the level of its own detrimental activity on mitochondrial function. Furthermore, we also found that pretreatment with Rd in vivo (10 and 50 mg/kg) protected spinal cord mitochondria against Ca²⁺ induced mitochondrial membrane potential dissipation and cytochrome c release. It is concluded that Rd regulate mitochondrial permeability transition pore formation and cytochrome c release through protein kinases dependent mechanism involving activation of intramitochondrial Akt and ERK pathways.

Neurologic complications of aortic diseases and aortic surgery

Aortic disease processes have a wide range of clinical manifestations. The inflammatory disease process of Takayasu's arteritis differs dramatically from the visceral ischemia of aortic dissection. The catastrophic event of aortic rupture tends to overshadow life-altering events such as stroke and paraplegia. However, these neurologic manifestations of aortic diseases have dramatic effects that extend beyond the individual patient to include both social and financial ramifications. This chapter focuses on the major aortic disease processes and how they can initiate, both directly and indirectly, adverse neurologic events. The chapter concludes with a brief discussion of aortic surgery, how interventions on the aorta can cause neurologic complications, and techniques to avoid these feared adverse neurologic outcomes.

A coupled hydrodynamic model of the cardiovascular and cerebrospinal fluid system

Coupling of the cardiovascular and cerebrospinal fluid (CSF) system is considered to be important to understand the pathophysiology of cerebrovascular and craniospinal disease and intrathecal drug delivery. A coupled cardiovascular and CSF system model was designed to examine the relation of spinal cord (SC) blood flow (SCBF) and CSF pulsations along the spinal subarachnoid space (SSS). A one-dimensional (1-D) cardiovascular tree model was constructed including a simplified SC arterial network. Connection between the cardiovascular and CSF system was accomplished by a transfer function based on in vivo measurements of CSF and cerebral blood flow. A 1-D tube model of the SSS was constructed based on in vivo measurements in the literature. Pressure and flow throughout the cardiovascular and CSF system were determined for different values of craniospinal compliance. SCBF results indicated that the cervical, thoracic, and lumbar SC each had a signature waveform shape. The cerebral blood flow to CSF transfer function reproduced an in vivo-like CSF flow waveform. The 1-D tube model of the SSS resulted in a distribution of CSF pressure and flow and a wave speed that were similar to those in vivo. The SCBF to CSF pulse delay was found to vary a great degree along the spine depending on craniospinal compliance and vascular anatomy. The properties and anatomy of the SC arterial network and SSS were found to have an important impact on pressure and flow and perivascular fluid movement to the SC. Overall, the coupled model provides predictions about the flow and pressure environment in the SC and SSS. More detailed measurements are needed to fully validate the model.

Simultaneous Evaluation of the Whole Aorta and Artery of Adamkiewicz by MDCT

Recent technical advancement has allowed simultaneous visualization of the artery of Adamkiewicz and whole aorta by multidetector-row-CT (MDCT). Although we could visualize the artery of Adamkiewicz in a high percentage of patients with thoracoabdominal aortic diseases, CT scanning with an adequate protocol and careful post-processing are necessary for accurate evaluation. Noninvasive evaluation of the artery of Adamkiewicz is useful in planning surgery. Preoperative evaluation of the intercostal arterial level from which the artery of Adamkiewicz originates is reportedly important for preventing postoperative spinal cord ischemia. Although, the usefulness of preoperative information on the artery of Adamkiewicz is still controversial, preoperative identification of the artery of Adamkiewicz by imaging has gradually spread since our first report, and has been included in preoperative evaluation items at many institutions, revealing its contribution to improvement in surgical results. (*English Translation of J Jpn Coll Angiol, 2004, 44: 693-699.).

Preoperative mapping of arterial spinal supply using 3.0-T MR angiography with an intravasal contrast medium and high-spatial-resolution steady-state

INTRODUCTION

Preoperative mapping of the arterial spinal supply prior to thoracoabdominal aortic aneurysm repair is highly relevant because of high risk for postoperative ischemic spinal cord injuries such as paraparesis or paraplegia.

METHODS

Twenty-four consecutive patients prior to surgical thoracoabdominal aortic aneurysm repair were investigated. All patients underwent steady-state MR angiography (MRA) of the spinal vasculature with 3-T MRI. The sequence used was a steady-state coronary 3D FLASH with 0.7-mm isotropic voxels. MRA was performed using an intravasal contrast agent. Studies were evaluated by three readers including delineation of arterial spinal supply including both aortic origin and spinal canal entry by three readers.

RESULTS

Identification and localization of the Adamkiewicz artery and its spinal canal entry was successful in all patients. Overall depiction of the vascular anatomy was graded as very good in 3 (12.5%), good in 14 (58.4%), sufficient in 5 (20.8%), and poor in 2 (8.3%) patients. Depiction of segmental artery aortic exit level was graded as good in 6 (25.0%), sufficient in 10 (41.7%), poor in 4 (16.7%) and not identifiable in 4 (16.7%) patients. Delineation of segmental artery entry level into the spinal canal was graded as very good in 4 (16.7%), good in 11 (45.8%), sufficient in 6 (25.0%), and poor in 3 (12.5%) patients.

CONCLUSIONS

The use of 3-T MRA with an intravascular contrast agent and steady-state enables AKA localization including its segmental arteries with regard to the level of aortic origin and spinal canal entry in most patients.

MR angiography of collateral arteries in a hind limb ischemia model: comparison between blood pool agent Gadomer and small contrast agent Gd-DTPA

The objective of this study was to compare the blood pool agent Gadomer with a small contrast agent for the visualization of ultra-small, collateral arteries (diameter<1 mm) with high resolution steady-state MR angiography (SS-MRA) in a rabbit hind limb ischemia model. Ten rabbits underwent unilateral femoral artery ligation. On days 14 and 21, high resolution SS-MRA (voxel size 0.49×0.49×0.50 mm³) was performed on a 3 Tesla clinical system after administration of either Gadomer (dose: 0.10 mmol/kg) or a small contrast agent (gadopentetate dimeglumine (Gd-DTPA), dose: 0.20 mmol/kg). All animals received both contrast agents on separate days. Selective intra-arterial x-ray angiograms (XRAs) were obtained in the ligated limb as a reference. The number of collaterals was counted by two independent observers. Image quality was evaluated with the contrast-to-noise ratio (CNR) in the femoral artery and collateral arteries. CNR for Gadomer was higher in both the femoral artery (Gadomer: 73±5 (mean ± SE); Gd-DTPA: 40±3; p<0.01) and collateral arteries (Gadomer: 18±4; Gd-DTPA: 9±1; p = 0.04). Neither day of acquisition nor contrast agent used influenced the number of identified collateral arteries (p = 0.30 and p = 0.14, respectively). An average of 4.5±1.0 (day 14, mean ± SD) and 5.3±1.2 (day 21) collaterals was found, which was comparable to XRA (5.6±1.7, averaged over days 14 and 21; p>0.10). Inter-observer variation was 24% and 18% for Gadomer and Gd-DTPA, respectively. In conclusion, blood pool agent Gadomer improved vessel conspicuity compared to Gd-DTPA. Steady-state MRA can be considered as an excellent non-invasive alternative to intra-arterial XRA for the visualization of ultra-small collateral arteries.

Excessively high systemic blood pressure in the early phase of reperfusion exacerbates early-onset paraplegia in rabbit aortic surgery

OBJECTIVE

We have demonstrated that therapeutic augmentation of systemic blood pressure during spinal cord ischemia plays an important role in minimizing spinal cord injury in both experimental and clinical aortic surgery. However, there remain concerns that excessively high blood pressure during spinal cord reperfusion may aggravate the reperfusion injury. The purpose of this study is to investigate the effect of high blood pressure during spinal cord reperfusion on postoperative neurologic outcomes after aortic surgery in rabbits.

METHODS

Experiments were performed using a rabbit spinal cord ischemia-reperfusion model in 2 randomly divided groups: (1) In the HR group, the mean blood pressure was maintained at a high level (121 +/- 1.3 mm Hg) during reperfusion with intravenously administered phenylephrine; and (2) in the CR group, the mean blood pressure was not medically controlled (75 +/- 9.1 mm Hg) during reperfusion. Neurologic and histologic assessments and evaluation of early reperfusion injury were performed.

RESULTS

In the HR group, slow and incomplete recovery of transcranial motor-evoked potentials (P = .02) and low neurologic scores (P < .005) were observed during spinal cord reperfusion compared with the CR group. At 48 hours of reperfusion, there were significantly fewer viable neuron cells, more apoptosis, and more perivascular edema with gray matter vacuolation in the HR group (P < .001 for each). At 3 hours, myeloperoxidase activity (P = .0021), vascular permeability (P = .0012), and superoxide generation (P < .0001) were significantly increased in the HR group.

CONCLUSION

Excessively high blood pressure in the early phase of spinal cord reperfusion increased reperfusion injury in the spinal cord, leading to exacerbation of early-onset paraplegia. Avoidance of spinal cord reperfusion with high blood pressure may be one management strategy in thoracoabdominal aortic surgery.