To the Editor:
We read with great interest the recent article by Nussbaum et al on the application of indocyanine green angiography to delineate venous system before dural opening in the parasagittal region. Although we agree with the authors that indocyanine green angiography is useful to localize veins or sinuses through the dura mater, we already reported that we had developed a near-infrared surgical microscope and applied it in clinical cases 10 years ago.2 Venous sinuses and bridging veins were observed through the dura mater. This was the first report that indocyanine green angiography was intraoperatively performed through a surgical microscope in neurosurgery. We used an excitation filter, a barrier filter, and a CCD camera to record indocyanine green angiography with the surgical microscope. After 10 years, the surgical microscope and its applications have been developed well and indocyanine green videoangiography is able to visualize these vessels clearer than indocyanine green angiography by the microscope we reported. However, the authors should have referred to and discussed the sequence of indocyanine green angiography in the neurosurgical history.
In any case, there is no doubt that the application of indocyanine green angiography before dural opening is an important issue in clinical neurosurgery. We have considered that indocyanine green angiography can be used for other surgical approach sites. For example, it is helpful for delineating the existence or the localization of the occipital sinuses in the posterior fossa. It could expedite dural opening and minimize venous bleeding. We also have an interest in the visualization of the anatomic structures on the cortical surface by each surgical approach site. The surgical approach sites would differ in how small cortical veins or arteries are delineated through the dura. The thickness of the dura mater could be attributed to its visualization.
Furuse, Motomasa; Hiramatsu, Ryo; Kuroiwa, Toshihiko
1. Nussbaum ES, Defillo A, Nussbaum L. The use of indocyanine green videoangiography to optimize the dural opening for intracranial parasagittal lesions [published online ahead of print July 25, 2011]. Neurosurgery. doi: 10.1227/NEU.0b013e31822ecfebv.
2. Kuroiwa T, Kajimoto Y, Ohta T. Development and clinical application of near-infrared surgical microscope: preliminary report. Minim Invasive Neurosurg. 2001;44(4):240–242.