Time varying characteristic in somatosensory evoked potentials as a biomarker of spinal cord ischemic-reperfusion injury in rat

Spinal cord ischemic-reperfusion injury (SCIRI) could occurs during surgical procedures without detection, presenting a complex course and an unfavorable prognosis. This may lead to postoperative sensory or motor dysfunction in areas innervated by the spinal cord, and in some cases, permanent paralysis. Timely detection of SCIRI and immediate waring can help surgeons implement remedial intervention to prevent irreversible spinal cord injury. Therefore, it is crucial to develop a precise and effective method for early detection of SCIRI. This study utilized rat models to simulate intraoperative SCIRI and employed somatosensory evoked potentials (SEP) for continuous monitoring during surgery. In this study, SEP signal changes were examined in six groups with varying severities of SCIRI and one normal control group. SEP signal changes were examined during operations in different groups and correlated with postoperative behavioral and histopathological data. The result demonstrated specific changes in SEP signals during SCIRI, termed as time-varying characteristics, which are associated with the duration of ischemia and subsequent reperfusion. Time-varying characteristics in SEP could potentially serve as a new biomarker for the intraoperative detection of SCIRI. This finding is significant for clinical surgeons to identify and guide early intervention of SCIRI timely. Additionally, this measurement is easily translatable to clinical application.

Systematic review and meta-analysis of association of prophylactic cerebrospinal fluid drainage in preventing spinal cord ischemia after thoracic endovascular aortic repair

OBJECTIVE

We conducted a systemic review and meta-analysis to compare the association between prophylactic cerebrospinal fluid drainage (CSFD) vs non-CSFD in preventing spinal cord ischemia (SCI) after thoracic endovascular aortic repair (TEVAR) for aneurysm and dissection.

METHODS

The MEDLINE, Embase, and Cochrane databases were systematically searched to identify all relevant studies reported before April 1, 2020. A systematic review and meta-analysis were performed. We assessed the association between CSFD strategies, including routine CSFD vs selective CSFD or no CSFD, and the SCI rates after TEVAR for patients with aortic dissection (AD), solitary thoracic aortic aneurysm (TAA), or thoracoabdominal aortic aneurysm (TAAA). Subgroup analyses were conducted to assess the association between different aortic pathologies, including AD and thoracic aneurysms, and SCI rates after TEVAR with and without prophylactic CSFD. The data are presented as the pooled event rates (ERs) and 95% confidence intervals (CIs).

RESULTS

A total of 34 studies of 3561 patients (2671 with TAA or TAAA and 890 with type B AD) were included in the present analysis. The data are presented as the pooled ERs and 95% CIs. The overall SCI rate for patients who had undergone TEVAR with prophylactic CSFD for AD (ER, 1.80%; 95% CI, 0.88%-2.72%) was significantly lower than that for the aortic aneurysm group (ER, 5.73%; 95% CI, 4.20%-7.27%; P < .0001). The SCI rate after TEVAR with prophylactic CSFD was not significantly different from that without CSFD for AD (P = .51). No association was found between the rates of SCI after TEVAR with routine prophylactic CSFD vs selective prophylactic CSFD for aortic aneurysms (P = .76) and AD (P = .70). The SCI rate after TEVAR without CSFD for aortic aneurysms, including isolated TAA and TAAA (ER, 3.49%; 95% CI, 0.23%-6.76%) was not significantly different from that for AD (ER, 3.20%; 95% CI, 0.00%-7.20%; P = .91). For the patients with TAAAs, the rate of SCI after TEVAR with routine prophylactic CSFD was significantly lower than that with selective prophylactic CSFD (P = .04).

CONCLUSIONS

Our systematic review and meta-analysis has shown that SCI occurs more often after TEVAR for aortic aneurysms than for AD. Routine prophylactic CSFD, compared with selective CSFD, was associated with a lower rate of postoperative SCI after TEVAR for TAAAs. No significant association was found between the SCI rate and routine prophylactic CSFD for patients undergoing TEVAR for isolated TAA or AD.

A systematic review and meta-analysis of the occurrence of spinal cord ischemia following endovascular repair of thoraco-abdominal aortic aneurysms

OBJECTIVE

The rates of endovascular repair of thoracoabdominal aortic aneurysms (TAAA-ER) have increased considerably in the last years. While mortality and morbidity rates have improved, spinal cord ischemia (SCI) rates have not declined significantly. The aim of this systematic review and meta-analysis was to examine SCI rates with respect to the efficacy of the different approaches.

METHODS

Cohort studies and case series (>20 patients) reporting SCI rates after TAAA-ER were eligible for inclusion. The primary outcome was the evaluation of SCI. Moderators considered were primarily the staged/non-staged approach, the use of cerebrospinal fluid drainage (CSFD) and TAAA extension. Permanent SCI and mortality rates were extracted.

RESULTS

Twenty-seven studies (n=2333 patients) were included in the meta-analysis. The pooled estimate for SCI was 11% (95% confidence interval [CI]: 8%-15%; I²:80%). For extent I,II,III and V TAAA, the pooled SCI rate was 13% (95% CI: 10%-17%; I²=71%), while for extent IV TAAA it was 6% (95% CI: 3%-10%; I²=62%). A staged TAAA-ER approach was used in 18 studies and a non-staged approach in 6 (one study included both). A lower pooled SCI rate was identified following staged compared with non-staged TAAA-ER (9% vs. 18%, respectively; P=.02). Staging was accomplished in >1 month in 9 studies and ≤1 month in 2, leading to similar SCI rates (7% vs. 11%, respectively; P=.29). The method of staging (thoracic-endoprosthesis or temporary aortic sac perfusion) did not affect SCI rates. Symptomatic CSFD was associated with a similar pooled rate of SCI compared with prophylactic CSFD (10% vs. 10%, respectively; P=.95). Pooled permanent SCI was 5% (6% following extent I,II,III and V TAAA; 3% following extent IV TAAA). Prophylactic or symptomatic CSFD have a similar rate of SCI (10% vs. 10%, respectively; P=.89). The pooled rate of 30-day mortality was 7%, with a similar incidence for the staged and non-staged approaches (6% vs. 9%, respectively). The inter-stage mortality was reported in 10 studies, with a pooled estimate rate of 1.6%.

CONCLUSIONS

SCI occurs in 11% of TAAA-ER and half of these cases are permanent. A staged approach can reduce SCI rates independently from the timing and the method adopted. The overall mortality rate for staged TAAA-ER is 6%, with one fourth of deaths (1.6%) occurring between stages.

New Preoperative Spinal Cord Ischemia Risk Stratification Model for Patients Undergoing Thoracic Endovascular Aortic Repair

PURPOSE

Our objective was to determine significant predictors of spinal cord ischemia (SCI) following Thoracic Endovascular Aortic Repair (TEVAR) and to further develop a simple and clinically orientated risk score model.

METHODS

A retrospective review of data from the Society of Vascular Surgery/Vascular Quality Initiative national data set was performed for all patients undergoing TEVAR from January, 2014 to June 2018. Preoperative demographics, procedure-related variables, and clinical details related to SCI were examined. A SCI risk score was developed utilizing a multivariable logistic regression model.

RESULTS

For the 7889 patients in the final analysis who underwent TEVAR during the study period, the mean age was 67.6 ± 13.9, range 18 to 90 years, and the majority was male (65%). Postoperative outcomes included stroke (3.0%), myocardial infarction (2.9%), inhospital mortality (5.4%), transient SCI (1.5%), and permanent SCI (2.1%). Nearly half of the overall cases were performed in high volume centers. Predictors of increased risk for SCI included age by decade (odds ratio [OR]: 1.2), celiac coverage (OR: 1.5), current smoker (OR: 1.6), dialysis (OR: 1.9), 3 or more aortic implanted devices (OR: 1.7), emergent or urgent surgery (OR: 1.5), adjunct aorta-related procedure (OR: 2.5), adjunct not related (OR: 2.6), total estimated length of aortic device (19-31 cm, OR: 1.9 and ≥32 cm, OR: 3.0), ASA class 4 or 5 (OR: 1.6), and procedure time ≥154 minutes (OR: 1.8). Two predictors decreased the risk of SCI, cases from high-volume centers (OR: 0.6) and eGFR ≥ 60 (OR: 0.6). To evaluate the risk score model, probabilities of SCI from the original regression, raw score, and raw score categories resulted in area under the curve statistics of 0.792, 0.786, and 0.738, respectively.

CONCLUSIONS

Spinal cord ischemia remains one of the most feared complications of TEVAR. Incidence of SCI in this large series of patients with TEVAR was 3.6% with nearly 60% being permanent. The proposed model provides an assessment tool to guide clinical decisions, patient consent process, risk-assessment, and procedural strategy.

Endovascular Treatment for Thoracoabdominal Aortic Aneurysm and Complex Abdominal Aortic Aneurysm Using Fenestrated and Branched Grafts

Fenestrated and branched endovascular aneurysm repair (F/B-EVAR) is a less invasive treatment for thoracoabdominal aortic aneurysm (TAAA) and complex abdominal aortic aneurysm. Fenestrated and branched (cuff) grafts facilitate safe and durable repair, and bail-out maneuvers for target vessel cannulation and stenting have been established; however, the available bridging stent grafts have differences. The present article discusses the optimal selection of fenestrated or branched grafts, the cannulation of target vessels that have difficult anatomies, and the advantages and disadvantages of various bridging stents. We review the causes and risk factors of spinal cord injury (SCI), the protocol for prevention of SCI, and the outcomes of target vessel stent grafting, including patency and endoleak.

Although conventional open surgery is the gold standard for the repair of thoracoabdominal aortic aneurysm (TAAA), it is highly invasive. To reduce invasiveness, hybrid surgery that combines open surgery and endovascular therapy has been developed [1, 2], and fenestrated and branched endovascular aneurysm repair (F/B-EVAR) is frequently performed at centers in the USA, Europe, and Japan [3-5]. Additionally, a hostile neck may be an independent factor for sac enlargement after EVAR for abdominal aortic aneurysm (AAA) [6], but a previous study reported that 41% of AAA cases presented with neck lengths outside the range prescribed by the traditional instruction for use [7]. Stark et al. showed that extending the graft above the highest renal artery would create an augmented neck length in 90% of patients with AAA [7]. F/B-EVAR is based on this principle. However, there are some technical tips for, and limitations of, fenestrated and/or branched graft. F/B-EVAR for TAAA and complex AAA will be reviewed in the present article.

Late-Onset Paraplegia After Endovascular Repair of Type B Aortic Dissection Managed by Urgent Left Subclavian Artery Revascularization: A Case Report

Spinal cord ischemia is one of the most unpredictable and feared complications after open surgical or endovascular thoracic aortic repair. Protection of collateral network branches that contribute blood supply to spinal cord is fundamental in the prevention of this catastrophic condition. We report the case of a patient who underwent emergent endovascular treatment for a type B aortic dissection complicated by rupture of the false lumen, with intentional coverage of the left subclavian artery without revascularization. The patient developed paraplegia on the 10th postoperative day, which did not significantly improve with immediate cerebrospinal fluid drainage but fully recovered after urgent left carotid-subclavian bypass.

Targeting the blood-spinal cord barrier: A therapeutic approach to spinal cord protection against ischemia-reperfusion injury

One of the principal functions of physical barriers between the blood and central nervous system protects system (i.e., blood brain barrier and blood-spinal cord barrier) is the protection from toxic and pathogenic agents in the blood. Disruption of blood-spinal cord barrier (BSCB) plays a key role in spinal cord ischemia-reperfusion injury (SCIRI). Following SCIRI, the permeability of the BSCB increases. Maintaining the integrity of the BSCB alleviates the spinal cord injury after spinal cord ischemia. This review summarizes current knowledge of the structure and function of the BSCB and its changes following SCIRI, as well as the prevention and cure of SCIRI and the role of the BSCB.

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.