The marked heterogeneity in glioblastoma (GBM) may be induced through dynamic differentiation and dedifferentiation process of glioma cells. The hypothesis that environmental stimuli induce these phenotypic changes, including dedifferentiation into the stem cell phenotype which contributes to the high invasiveness and resultant poor outcome in GBM patients, is recently being proven. In the process of cancer invasion and metastasis, the phenotypic change has also been described as epithelial-mesenchymal transition (EMT). This biological process is mainly dependent on hypoxic stimuli and also on transforming growth factor-β (TGF-β) released from glioma stem cells, mesenchymal stem cells, and myeloid cells recruited by hypoxia. The tumor microenvironment, especially hypoxia, inducing such dynamic phenotypic changes can be a good therapeutic target in the treatment of GBM.

Indocyanine green (ICG) emits fluorescence in the far-red domain under light excitation. ICG video angiography (ICG-VA) has been established as a useful method to evaluate blood flow in the operative field. We report the usefulness of ICG-VA for Sylvian fissure dissection in patients with subarachnoid hemorrhage (SAH). Subjects comprised 7 patients who underwent ICG-VA before opening the Sylvian fissure during neck clipping for ruptured cerebral aneurysm. We observed contrasted Sylvian veins before opening the Sylvian fissure using surgical microscopes. This procedure was termed “Sylvian ICG”. We observed ICG fluorescence quickly in all cases. Sylvian veins that appeared unclear in the standard microscopic operative field covered with subarachnoid hemorrhage were extremely clearly depicted. These Sylvian ICG findings were helpful in identifying entry points and the dissecting course of the Sylvian fissure. At the time of clipping, no residual fluorescence from Sylvian ICG was present, and aneurysm clipping was not impeded. Sylvian ICG for SAH patients is a novel technique to facilitate dissection of the Sylvian fissure. We believe that this technique will contribute to improved safety of clipping surgery for ruptured aneurysms.

The advent of magnetic resonance imaging (MRI) enables noninvasive measurement of cerebrospinal fluid (CSF) motion, and new information about CSF motion has now been acquired. The driving force of the CSF has long been thought to be choroid plexus (CP) pulsation, but to investigate whether this phenomenon actually occurs, CSF motion was observed in the ventricular system and subarachnoid space using MRI. Eleven healthy volunteers, ranging in age from 23 to 58 years, participated in this study. The MRI sequences used were four-dimensional phase-contrast (4D-PC) and time-spatial labeling inversion pulse (t-SLIP). The 4D-PC images included sagittal images in the cranial midline, coronal images focusing on the foramen of Monro (FOM), and oblique coronal images of the trigone to quantify CSF velocity and acceleration. These values were compared and analyzed as non-parametric data using the Kolmogorov-Smirnov test and the Mann-Whitney U test. 4D-PC showed that the median CSF velocity was significantly lower in the posterior part of the lateral ventricle than in other regions. The quantitative analysis of velocity and acceleration showed that they were decreased around the CP in the trigone. Image analysis of both velocity mapping and t-SLIP showed suppressed CSF motion around the CP in the trigone. These findings cast doubt on CP pulsation being the driving force for CSF motion.