Indocyanine Green Videoangiography in Negative: Spinal Dural Arteriovenous Fistula

Introduction

Indocyanine green videoangiography (IGV) in negative, so called because its first phase is performed with occlusion of the vessel suspected of being pathological, has been defined in spinal and intracranial dural arteriovenous fistula. ¹ , ² In the present work, the authors show the first case of IGV in negative published with video support, which was used for the diagnosis of a spinal arteriovenous fistula (sDAVF). This procedure avoids some of the limitations of conventional IGV and facilitates its interpretation. ³

Case Report

A 68-year-old man had acute paraparesis and sphincter control disturbances. T2-weighted magnetic resonance imaging showed intramedullary hyperintensity and flow voids within the spinal canal. Selective spinal digital subtraction angiography (DSA) confirmed the diagnosis of sDAVF, fed by the right T7 segmentary artery (Fig. 1). The surgical treatment (Video 1) was performed in the prone position under general anesthesia, with monitoring by motor evoked potentials. After patient consent was obtained, a T7 right hemilaminectomy and midline durotomy were performed. The right-sided T7 nerve root and arterial periradicular network were identified extradurally. Intradurally, we observed a vein that hung from the dura mater, which drained into a serpiginous and dilated venous network. This venous vessel with suspected arterialization was temporarily clipped. Some seconds after the clipping, an IGV in negative was performed, with intravenous administration of a bolus of 25-mg ICG diluted in 5 mL under a Pentero surgical microscope (Carl Zeiss Co., Oberkochen, Germany). During the first phase, filling of the venous and arterial medullary vessels was observed, but no filling was seen in the serpiginous venous network. In the second phase (1 minute after the administration of ICG), after the removal of the temporary clip, rapid filling of the serpiginous venous network was observed, which is typical of sDAVF. After this vessel was identified as pathological, we proceeded to perform coagulation and cutting, with subsequent darkening of the serpiginous venous network on imaging. During intraoperative monitoring, no changes were observed. The patient experienced a significant motor improvement. Immediate postoperative DSA ruled out the existence of dural arteriovenous fistulae.

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Fig. 1

(A) Sagittal T2-weighted magnetic resonance imaging showed intramedullary hyperintensity (arrowhead) and flow voids (arrow) in the spinal canal. (B) Digital subtraction angiography showing a spinal arteriovenous fistula fed by the right T7 segmentary artery.

Discussion

IGV in negative has been developed for the diagnosis of spinal and intracranial dural arteriovenous fistulae. ¹ , ² Conventional IGV involves the intravenous administration of indocyanine green. Subsequently, vascular filling is visualized using specific optical systems that are integrated in current surgical microscopes. IGV has primarily been compared with intraoperative arteriography, ⁴ which is the gold standard in the context of neurovascular pathology. The fundamental limitations of IGV are that the vascular structures to be analyzed must be exposed within the surgical field. As a result, blood vessels that are blocked by a clot, atheroma, or brain parenchyma, as well as blind angles, are invisible using this technique. In the case presented, negative IGV as applied to the sDAVF provided both diagnostic and postexclusion control in a single procedure that took less than 1 minute. ⁵ Reversibility was enabled by the shortened vascular exclusion time. Conversely, conventional IGV comprises two procedures, one for diagnosis and one for the postexclusion control. Conventional IGV often requires repeated visualizations, which makes the procedure longer and more difficult to perform.

IGV in negative is an extremely visual and intuitive procedure, and, more importantly, it is reversible and avoids repeated IGV visualizations and other complex intraoperative procedures. ⁴ The procedure excludes the possible presence of multiple shunts in cases where there is filling of the arterialized venous system after transient occlusion. Additionally, this procedure can be performed with minimally invasive approaches as only a short durotomy and microscope view are required.

Conclusion

In conclusion, IGV in negative is an improvement over conventional IGV methods, as the technique can provide more information in a shorter period of time and in a more intuitive way. ² Studies with larger samples will be necessary to determine whether IGV in negative can further reduce the need for postoperative DSA.