In recent decades, increasing number of neurosurgeons have realized the importance of venous preservation because the injury or occlusion of important intracranial venous structures might lead to severe complications, such as hematoma, epilepsy, cerebral edema, hemiplegia, and aphasia. Instead of depending heavily on their own surgical experience, neurosurgeons took advantage of neuroimaging tools such as DSA, MRA, MRV and TCD preoperatively to analyze the vascular structures surrounding the lesion. In addition, the development of intraoperative microvascular Doppler (MVD) and ICG-VA has made the visualization of intraoperative blood flow possible. These technics that help neurosurgeons to understand the dynamic flow of the venous system and how to preserve them are welcoming.
Groups of veins were treated differently after neurosurgeons made surgical judgement, considering whether to preserve them. As for the superficial cerebral veins, they are strongly interconnected, making it acceptable to sacrifice one of them. Additionally, once the terminal ends of the Sylvian left the fissure and entered the sphenobasal, sphenoparietal, or cavernous sinus, they can be sacrificed safely. However, known as central group of veins, bridging veins should not be stretched, injured or sacrificed in avoidance of devastating consequences including contralateral hemiplegia. When it came to the vein of Labbe, surgeons usually preserved it to avoid venous infarction of the temporal lobe at all costs. As injury to the deep venous system led to diencephalic edema, hyperpyrexia and death, preservation of deep veins like the vein of Galen aroused great concern.[15-18] However, there were no clear guidelines for venous preservation. And it was important to make surgical judgment on a case-by-case basis with the help of imaging tools.
In patients undergoing craniotomy for tumor resection, thrombosis of the cerebral veins and sinuses happened from time to time. The symptoms were highly variable including headaches, seizures and delirium, which resulted in the difficulty of timely diagnosis. When the infarcts were associated with increased intracranial pressure, patients might die because of cerebral herniation. In order to clarify the formation of vein thrombosis and take treatment as soon as possible, it was important to use ICG-VA integrated with FLOW 800 during the surgical process.
As the first to report the use of microscope-integrated quantitative analysis of ICG-VA for blood flow assessment, Kamp et al. showed the great value of the maps and promoted clinical applications of FLOW 800 analysis. However, few articles reported the use of ICG-VA along with FLOW 800, especially in the field of surgery for brain tumors, cerebral and spinal hemangioblastomas.[20-22] In present case reports, we described our experience with using ICG-VA integrated with FLOW 800 in brain tumor resection to observe venous flux and detect obstruction of venous reflux timely. All of our patients had good prognosis after surgery.
There were several limitations of our study. First, we included a small number of participants. Second, the use of ICG-VA with Flow 800 was subjective based on the experience of the surgeon. We have not reached an optimal protocol to use it routinely throughout the procedure. In addition, quantitative data of Flow 800 was not collected and analyzed systemtically. Furthermore, long-term follow up investigation was needed.
Comparison between ICG-VA integrated with FLOW 800 and other techniques of blood flow monitoring was needed in order to demonstrate the sensitivity and specificity. We believe the application of ICG-VA integrated with FLOW 800 will be expanded in the future.