The WHO classification of Tumours of the Central Nervous System was updated as per the revised 4th edition in 2016.

  The main change was that molecular parameters in addition to histology are now used to define many tumor entities. Therefore, the 2016 edition presents a major restructuring of the diffuse gliomas, ependymomas, medulloblastomas and other embryonal tumours.

  The new entities defined by both histology and molecular features include diffuse astrocytoma, IDH mutant and diffuse astrocytoma IDH-wildtype ; oligodendroglioma IDH mutant and 1p19q-codeleted ; glioblastoma, IDH-wildtype and glioblastoma, IDH-mutant ; diffuse midline glioma, H3 K27M-mutant ; RELA fusion-positive ependymoma ; medulloblastoma, WNT-activated and medulloblastoma, SHH-activated ; and embryonal tumour with multilayered rosettes, C19MC-altered.

  However, most of these molecular markers adopted for diagnosis could be surrogated by immunohistochemical studies. As such, this update may present a big challenge and in the transition period.

   “Maximal safe resection” is required for glioma surgery. Technological advances in intraoperative brain function and tumor location evaluation have led to a more aggressive approach to glioma resection while still maintaining functional preservation. However, basic neurosurgical techniques still play the most key role in obtaining “maximal safe resection”. Dissection of the fissure, sulcus, and cerebral vessel as well as unfolding the gyrus and lobe are important techniques to remove gliomas. When taking the biological characteristics of gliomas, especially their invasiveness, in mind, the extent of resection should be decided in view of the displaced vessels, neurotract, eloquent area, original site and spreading mode of the tumor. For neurosurgeons, the three main points to notice are : do not rely on surgical support systems and techniques, keep a clear operative view, and cultivate your surgical intuition.

  The right frontal lobe functions as the social brain and enables humans to engage in social life smoothly. The right frontal lobe is also involved in motor function and higher brain functions such as working memory, nonlinguistic semantic memory, spatial cognition, social cognition, attention, and executive function. Cerebral white matter in the right frontal lobe contains fiber networks affecting the pyramidal tract, frontal aslant tract, fronto-striatal tract, superior longitudinal fasciculus, arcuate fasciculus, cingulum, inferior fronto-occipital fasciculus, and uncinate fascicle. Each fasciculus affects motor, motor initiation, motor control, spatial cognition, mentalizing, attention, nonlinguistic semantic memory, and episodic memory, respectively. In awake surgery for lesions in the right frontal lobe, suitable tasks should be chosen based upon this knowledge concerning the function of gray matter and fiber networks close to the lesion.

  Prognostic factors for patients with brain metastases vary by diagnosis, implying considerable heterogeneity in outcome even within a single tumor type. Evidence-based clinical practice guidelines have rapidly evolved into critically important tools for optimizing individualized care for patients. Guidelines have become particularly relevant for the treatment of brain metastasis given the importance of the multidisciplinary coordination of care with neuro-oncology and radiation oncology, in addition to neurosurgery. Our clinical practice guideline 2016 can help by providing a starting point where a systematic evidence review leads to practice recommendations formulated by a multidisciplinary panel of experts. Partial updating is now in progress, and must be followed by full updating with the GRADE system.

  A carotid-vertebral anastomosis is known to develop from stenosis or occlusion of the carotid or vertebral artery. We report a case with an internal carotid artery stenosis and an extra-cranial vertebral artery stenosis combined with a carotid-vertebral anastomosis. Upon treatment of the internal carotid artery stenosis, we were concerned about a hemodynamic ischemia of the posterior circulation through the anastomosis. Therefore, we performed a percutaneous transluminal angioplasty for the vertebral artery stenosis to secure the posterior circulation blood flow. As a result, the carotid-vertebral anastomosis disappeared in the left common carotid angiography. Then, we could perform a carotid endarterectomy for the internal carotid artery stenosis with no adverse events. It is necessary to prevent hemodynamics ischemia when treating carotid artery stenosis with a carotid-vertebral anastomosis. And, it is important to verify the treatment in each patient.

  A 76-year-old woman presented with sudden onset of headache and vomiting, then transferred to our hospital. She suffered from a subarachnoid hemorrhage (SAH) resulting from ruptured intrameatal aneurysms of the right distal anterior inferior cerebellar artery (AICA). We treated her by trapping the AICA, ultimately. After the operation, the patient experienced a hearing disturbance in her right ear that did not improve.

  Aneurysms at the meatal loop inside the internal auditory meatus are extremely rare. Damage to the 8th cranial nerve often occurs as a complication of ruptured intrameatal aneurysms or their surgical treatments, a condition from which it is difficult to recover. Many treatments have been applied, such as clipping, trapping, endovascular therapy and occipital artery-AICA bypass with aneurysm trapping to treat them. We presented a review of the literature, and referred to features and treatment techniques for intrameatal aneurysms.

  Tumefactive multiple sclerosis (MS) shows imaging features that are not typical of MS. Because extensive edema and mass effects are seen, differentiation from brain tumor is difficult. We present a case of tumefactive MS diagnosed preoperatively as malignant glioma. Case : A 66-year-old man presented with convulsions of the right half of the body. Magnetic resonance imaging (MRI) of the brain showed an annular enhancing mass measuring 4 cm×5 cm×6 cm with substantial edema in the left frontal lobe. Computed tomography (CT) showed hemorrhagic changes, and arterial spin labeling (ASL) MRI showed no increased blood flow in the lesion. We suspected malignant glioma and resected the mass lesion. Histopathological examination was consistent with demyelinating disease, and tumefactive MS was diagnosed. The patient was treated with corticosteroid therapy and plasma exchange therapy postoperatively. Although few imaging findings are specific for tumefactive MS, a lack of increased blood flow in the lesion may be a point of differentiation from malignant glioma.