Flat panel catheter angiotomography of the spinal venous system: an enhanced venous phase for spinal digital subtraction angiography

Efficacy of preoperative embolization for metastatic spinal tumor surgery using angiographic vascularity assessment

OBJECTIVES

Preoperative embolization (PE) for metastatic spinal tumors is a method of minimizing intraoperative blood loss during aggressive surgery. This study specified angiographic standards and investigated the influence of these and other factors on blood loss in patients with spinal metastases and various pathologies.

METHODS

The cohort comprised 126 consecutive patients receiving PE from 2015 to 2021. Their clinical, surgical, and angiographic characteristics were reviewed. Standard angiographic grading was used for vascularity assessment. Degree of embolization was divided into complete (≥ 90%), near complete (67 to < 90%), and partial (< 67%). Logistic regression analysis was used to investigate factors predictive of massive blood loss (> 2500 mL). A proportional odds model was used to assess factors predictive of the degree of embolization.

RESULTS

Mean intraoperative blood loss was 1676 mL. Among the patients, 62 had hypervascular tumors and 64 had nonhypervascular tumors, according to the angiographic classification. Intraoperative blood loss differed significantly with embolization degree, both overall (p < 0.001) and in the hypervascular and nonhypervascular groups (p = 0.01 and 0.03). Angiographic hypervascularity, spinal metastasis invasiveness index, and embolization degree were significant predictors of massive blood loss in univariate analysis, but only embolization degree was significant in multivariate analysis. Only the presence of the radiculomedullary artery at the target level was significant in both the univariate and multivariate analyses for embolization degree.

CONCLUSIONS

In addition to pathological classification, angiographic vascularity assessment is valuable. Although complete embolization is a reasonable goal, it is challenging to achieve in cases of visible radiculomedullary artery.

KEY POINTS

• Angiography has a supplementary role in vascularity assessment for spinal metastatic surgery. • Better embolization degree is associated with less intraoperative blood loss in both angiographic hypervascular and nonhypervascular groups. • Presence of radiculomedullary artery in the target level causes worse embolization outcome.

Spinal Epidural Lipomatosis Associated with Intrathecal Flow Voids: Demonstration of Engorged Veins Using Flat Panel Catheter Angiotomography

We present a case of a 54-year-old male with spinal epidural lipomatosis who had associated flow voids on magnetic resonance imaging with dilated intrathecal vessels. During spinal angiogram, 20s DynaCT (flat panel catheter angiotomography) was utilized to demonstrate the intrathecal engorged veins. Venous engorgement of epidural venous plexus has been previously described in epidural lipomatosis; however, dilated intrathecal perimedullary veins have not been demonstrated by imaging. We have described the utility of flat panel catheter angiotomography in understanding venous disorders in such patients.

Spinal vascular malformations: Angiographic evaluation and endovascular management

Spinal vascular malformations (SVM) are classified based on their location (intramedullary, perimedullary, radicular, extradural) and flow pattern (high-flow, low-flow, no arteriovenous shunt). High-flow SVMs are generally congenital lesions diagnosed in children and young patients without gender predominance. They present with hemodynamic disturbances, mass effect, or hemorrhages, but may also be discovered incidentally. Low-flow SVMs tend to be acquired lesions presenting in older men with progressive myelopathy caused by spinal venous hypertension. They are rarely associated with vascular syndromes but may accompany prothrombotic conditions. The sensitivity and specificity of conventional MRI are excellent for high-flow SVMs but poor for low-flow lesions, which are frequently diagnosed with extensive delays reducing the potential for favorable outcomes. The sensitivity of advanced MRI techniques remains unclear, notably for the detection of low-flow shunts without flow voids on conventional MRI. Catheter angiography remains the gold standard modality for the evaluation of the spinal vasculature and its disorders. SVMs can be treated by surgical or endovascular means. Initially plagued by high recurrence rates due to inadequate embolization material, endovascular techniques represent nowadays a valid alternative to surgery, thanks notably to the introduction of liquid embolic agents.

The antireflux mechanism - Angiographic anatomy and clinical implications

BACKGROUND

Early anatomists suspected that the radiculomedullary veins draining the spinal cord had valves preventing their retrograde filling with anatomical casting material. Modern investigations have discarded the presence of true valves and introduced instead the notion of a pseudo-valvular configuration for which the term antireflux mechanism was coined in the 1970s. The angiographic anatomy of the antireflux mechanism has not been well documented so far.

METHODS

This article discusses anatomical and clinical features of the antireflux mechanism with a series of 12 angiographic observations documenting the antireflux mechanism under normal and pathological circumstances.

RESULTS

The antireflux mechanism divides radiculomedullary veins into intradural and extradural segments. While the structure of the antireflux mechanism is not yet fully clarified, it includes at least a tight narrowing of the radiculomedullary vein at its point of passage through the thecal sac, which is angiographically detectable and likely protects the intradural venous system from transient or persistent surges in venous pressure (e.g. sneezing, pregnancy). This tight narrowing of the antireflux mechanism likely also represents an obstacle to normal anterograde flow, potentially leading to venous stagnation and thrombosis.

CONCLUSIONS

The antireflux mechanism includes at least a tight narrowing of the radiculomedullary vein, which likely influences the development and clinical expression of low-flow spinal arteriovenous fistulas and might impact the spinal venous drainage even in the absence of arteriovenous shunts.

Introduction to Diagnostic and Therapeutic Spinal Angiography

This article describes the basic principles of diagnostic and therapeutic spinal angiography as practiced by the author, including catheterization and radioprotection techniques, the selection of endovascular devices and embolization agents, and procedural complications.

Advances in 3D angiography for spinal vascular malformations

Spinal vascular malformations are difficult to diagnose lesions that can be associated with significant permanent morbidity. The angioarchitecture of spinal vascular anatomy and the associated pathologies have only recently been illuminated by the advent of spinal angiography. However, conventional spinal digital subtraction angiography is often limited by significant variability, overlapping vessels, as well as an inability to understand the precise location of the nidus or fistula in relation to the spinal cord and spine. In this study, we present 4 unique cases wherein 3-dimensional rotational angiography (3DRA) with dual volume acquisition was useful in defining the anatomy of spinal fistulas as well as planning treatment.

The Transdural Course of Radicular Spinal Cord Veins--A Microangiographical and Microscopical Study

PURPOSE

This study focuses on the following questions: What are the morphological features at the transdural course of radiculomedullary veins? How are these short transdural segments that may harbour pathological arteriovenous shunts connected to the internal vertebral venous plexus? Is the conception of a reflux-impeding mechanism at the transdural segment indispensable and convincing?

METHODS

A total of 102 radiculospinal veins were studied microscopically at various levels of the spinal canal using serial paraffin and semi-thin sections. In addition, 26 vessels were investigated microangiographically following orthograde (12) or attempted retrograde (14) opacification of the intradural venous segment with barium sulphate. After paraplast-embedding, contact-microradiographs were taken using high-resolution spectroscopic plates.

RESULTS

At their transdural course, the veins showed narrowing of their lumen accompanied by changes in the vessel wall composition and a tortuous course. Two structurally distinct arrangements of the transdural segment could be identified: A slit type was seen in 60% of the veins studied and a bulge- or nodular type was seen in 35% of the veins. In total, 5% of cases could not be assigned to either one of these types. Reflux to radicular veins from the outside of the dura mater could be produced in 2 out of 14 specimens. The extradural venous plexus, which primarily receives the radicular vein, was composed more frequently of lacunar spaces rather than plexiform blood vessel convolutions. Rare observations were fibrotic, blind ending radiculomedullary veins and continuation of a distinct venous blood vessel after crossing the dura.

CONCLUSIONS

Reflux from the epidural plexus to radicular veins is not reliably stopped at the dural level and possibly physiological. Different arrangements of the transdural course of the veins appear to be at least appropriate to modulate flow. The purpose for two different types of radicular vein exit is unclear. The clinical impact of disturbed reflux-control is uncertain, which is in stark contrast to the severe consequences resulting from dural arteriovenous shunts. The functional role of the probably predominant epidural venous plexus for the spinal cord blood circulation remains poorly understood.

Transmedullary Venous Anastomoses: Anatomy and Angiographic Visualization Using Flat Panel Catheter Angiotomography

Flat panel catheter angiotomography, a recently developed angiographic technique, offers a spinal equivalent to the venous phase obtained during cerebral angiography. This report of 8 clinical cases discusses the flat panel catheter angiotomography appearance of a type of spinal venous structure until now principally known through the analysis of postmortem material, transmedullary venous anastomosis. The illustrated configurations include centrodorsolateral, median anteroposterior, median anteroposterior with duplicated origin, and combined centrodorsolateral/median anteroposterior transmedullary venous anastomoses, while a pathologic example documents the potential role of transmedullary venous anastomoses as collateral venous pathways. Two of the reported configurations have not been previously documented. Transmedullary venous anastomoses are normal venous structures that need to be differentiated from spinal cord anomalies, such as intramedullary vascular malformations.

Periconal arterial anastomotic circle and posterior lumbosacral watershed zone of the spinal cord

BACKGROUND

The existence of spinal cord watershed territories was suggested in the 1950s. Segmental infarcts within the junctional territories of adjacent radiculomedullary contributors and isolated spinal gray matter ischemia constitute two well-recognized types of watershed injury. This report describes the existence of another watershed territory related to the particular configuration of the spinal vasculature in the region of the conus medullaris.

METHODS

The anatomical bases underlying the concept of a posterior lumbosacral watershed zone are demonstrated with angiographic images obtained in a 16-year-old child. The clinical importance of this watershed zone is illustrated with MRI and angiographic data of three patients with a conus medullaris infarction.

RESULTS

In all three cases of spinal ischemia an intersegmental artery providing a significant radiculomedullary contribution for the lower cord was compromised by a compressive mechanism responsible for decreased spinal cord perfusion (diaphragmatic crus syndrome in two cases, disk herniation in one). The ischemic injury, located at the junction of the anterior and posterior spinal artery territories along the dorsal aspect of the conus medullaris, was consistent with a watershed mechanism. This zone is at risk because of the caudocranial direction of flow within the most caudal segment of the posterior spinal arterial network which, from a functional standpoint, depends on the anterior spinal artery.

CONCLUSIONS

The posterior thoracolumbar watershed zone of the spinal cord represents an area at increased risk of ischemic injury, particularly in the context of partial flow impairment related to arterial compression mechanisms.

The arrow-tipped loop is a marker of radiculomedullary vein thrombosis linked to the anti-reflux mechanism--angiographic anatomy and clinical implications

INTRODUCTION

This article proposes that the "arrow-tipped" loop or anastomosis classically described as an anatomic variant represents in fact a pathological phenomenon resulting from the partial thrombosis of a radiculomedullary vein (RMV) with a duplicated origin (double-rooted RMVs).

METHODS

The arrow-tip loop concept proposed in this report is illustrated with angiographic observations of patients with underlying pathologies of the spinal venous system, three cases of spinal arteriovenous fistulas, and one case of spinal venous insufficiency.

RESULTS

In each clinical case, the presence of arrow-tip loops was associated with diffuse alteration of the perimedullary venous system, including the lack of detectable RMVs. The angiographic appearance of the arrow-tip loops suggested partially thrombosed double-rooted RMVs, with rootlets originating either from the anterior or posterior spinal veins, or from both.

CONCLUSION

While a thrombosed single-rooted RMV typically becomes anatomically and angiographically undetectable, double-rooted MRVs keep a flowing proximal segment made of their two rootlets of origin. This residual proximal segment takes the appearance of an arrow-tip loop, which therefore be seen as an indicator of spinal venous thrombosis.

Angiographic detection and characterization of "cryptic venous anomalies" associated with spinal cord cavernous malformations using flat-panel catheter angiotomography

BACKGROUND

Spinal cord cavernous malformations (CMs) are associated with 2 types of angiographically occult "cryptic venous anomalies," which differ in location with respect to the spinal cord. The anatomic distinction between superficial and intramedullary is important in that the latter heighten the risks of CM resection.

OBJECTIVE

To report the observations of both types of cryptic venous anomalies documented during spinal digital subtraction angiography enhanced with flat-panel catheter angiotomography (FPCA).

METHODS

Spinal digital subtraction angiography enhanced with FPCA was performed in 2 adult patients with magnetic resonance imaging--documented intramedullary spinal cord CMs and prominent, nonspecific flow voids at the same levels. FPCA was obtained by selective injection of left T4 (case 1) and left T9 (case 2) with 5F Cobra 2 catheters (Terumo, Japan) during a 20-second rotational acquisition. Thirty milliliters of a 75% saline and 25% contrast solution (Omnipaque 300; GE) was administered. The rotational data set was reconstructed on a dedicated workstation (Leonardo; Siemens, Erlangen, Germany) through the use of regular and high-resolution matrixes, 0.4- and 0.1-mm voxel size, respectively.

RESULTS

Spinal digital subtraction angiography was unremarkable in both cases. In case 1, FPCA findings indicated an atypical network of prominent posterior perimedullary veins. In case 2, FPCA identified radially oriented channels forming a caput medusae pattern collecting into an enlarged intramedullary vein.

CONCLUSION

The unique ability of FPCA to image the spinal venous system enables the angiographic detection and characterization of abnormal spinal veins associated with CMs. Differentiating between the types of associated cryptic venous malformations may aid in surgical planning because the intramedullary type is associated with a higher risk of surgical complication.