Treatment of WHO grade Ⅱ and Ⅲ meningiomas is challenging, and the number of grade Ⅱ meningiomas has increased after the recent revision of the WHO classification. In terms of surgical treatment, the benefit of gross total resection (GTR) to subtotal resection (STR) for grade Ⅱ meningiomas is well established, but it has not been established for grade Ⅲ meningiomas. In terms of postoperative radiotherapy (PORT), PORT is effective after STR but not after GTR for grade Ⅱ meningiomas. However, PORT benefits after GTR for grade Ⅱ meningiomas have been recently reported and these techniques are currently being investigated in ongoing phase Ⅲ clinical trials. There have also been reports that high-dose irradiation and particle beam irradiation, including boron neutron capture therapy, can benefit conventional radiotherapy, and their effectiveness is also being investigated in ongoing clinical trials. Despite poor prognoses, there have been reports about the benefits of radiotherapy for grade Ⅲ meningioma. The use of systemic therapy should only be considered for refractory tumors as salvage therapy because its effectiveness has been shown to be limited in clinical trials.

  Recently, the treatment of metastatic brain tumors has evolved dramatically owing to rapid advances in radiation and medical therapy. In the case of radiation therapy, stereotactic radiotherapy is expanding and the maximum number of treatable metastases has increased. In addition, standard radiotherapy after surgical tumor resection is shifting from whole-brain irradiation to stereotactic/local irradiation. In the case of medical therapy, molecular-targeted therapy has been reported to be effective against brain metastases from non-small cell lung cancer, melanoma, and breast cancer with specific genetic abnormalities. The usefulness of immune checkpoint inhibitors has also been demonstrated in large-scale clinical trials. As drug therapy based on genetic abnormalities evolves, the importance of genetic testing is increasing and the treatment for metastatic brain tumors is advancing in line with the development of cancer genomic medicine. A combination of multiple modalities is required for the effective treatment of metastatic brain tumors, which means that the need for multidisciplinary teams will increase in the future.

  Diffuse gliomas account for approximately 80% of malignant central nervous system tumors and are classified by the World Health Organization (WHO) into grades Ⅱ-Ⅳ according to their histopathology and clinical behavior. WHO grade Ⅱ diffuse gliomas used to be referred to as low-grade gliomas (LGGs), while WHO grades Ⅲ and Ⅳ gliomas were high-grade gliomas. LGGs are generally less aggressive tumors with a longer and indolent clinical course. Adding radiotherapy to surgery has been suggested for LGG. LGGs are responsive to radiotherapy plus chemotherapy. However, the timing of these therapies after surgery is controversial. On the other hand, several mutant IDH1 inhibitors have been clinically investigated. The mutant IDH1 inhibitors could be a promising option to suppress clonal evolutions and prolong the malignant transformation-free survival.

  Genetic/epigenetic analysis and transcriptome analysis using next-generation sequencing have revealed many of the biological characteristics of glioblastoma. In glioblastoma, three core pathway abnormalities : the receptor tyrosine kinase (RTK) pathway, the p53 pathway, and the retinoblastoma (RB) pathway, are the main abnormal pathways, and there are three subtypes : proneural, classical, and mesenchymal, depending on gene expression. However, a single-cell RNA-seq analysis revealed that there are various subtypes with different gene expressions within the same glioblastoma in the same patient. The results also showed that cell subtypes have plasticity that can be changed by genetic and chromosomal abnormalities and the microenvironment around the tumor. In addition, on recurrence after treatment, many glioblastomas have subtypes that are switched and have different properties. Currently, the main standard treatments for glioblastoma are surgery, radiation therapy, and chemotherapy. However, immunotherapy, including immune checkpoint inhibitors, is expected to be added in the future. It is very important to analyze the biological characteristics of the glioblastoma cells themselves. However, as a direction for future research, it will be necessary to longitudinally analyze the interaction between glioblastoma cells and the various cells that form the microenvironment, that is, immune cells, such as macrophages/microglia and lymphocytes, vascular endothelial cells, and neurons, in the context of the time axis.

  We attempted to elucidate the pathophysiology of artery-to-artery embolism during carotid exposure when undertaking carotid endarterectomies. The absence or presence of collateral pathways in the cerebrum, along with cerebrovascular dysautoregulation due to reduced perfusion pressure and the wash-out hypothesis, explained why low blood flow velocity in the cerebral artery impairs clearance of the emboli and the potential development of ischemic lesions in the cerebrum when emboli develop. In addition to the properties of plaque (hemorrhage, etc.), the degree of wall shear stress in the stenotic portion may cause emboli to develop from the surgical site for cervical carotid stenosis.

  In the surgical treatment of hypertensive intracerebral hemorrhage, endoscopic surgery is a single-perforation procedure that is less invasive, shorter, and safer compared with conventional craniotomy. However, the area that can be manipulated within the operative field is limited, which may lead to inadequate hemostasis and cause posterior bleeding. FloSeal^® (Baxter), a gelatinous hemostatic agent containing human thrombin, is an effective local hemostatic agent that has a low reported rate of complications. Here we describe a case of intracerebral cyst formation following endoscopic hematoma removal using FloSeal^®. We suspected that placement of gelatinous material in the cystic component of the hematoma may have caused an inflammatory reaction in the cavity. FloSeal^® material should be washed, which is presumably the cause of the inflammatory reaction thoroughly.