Since 2003, five prospective studies on unruptured intracranial aneurysms have demonstrated their natural course (i.e. annual rupture rates) in detail. Recently, in addition, several meta-analyses, pooled analyses, risk scoring studies have been reported. Because there are many quotations of clinical data between these kinds of analyses, one must understand precisely where the pooled data come from. The risk factors for aneurysmal rupture proposed in the five prospective studies differ greatly from each other, and one must also understand these differences as well.

  UCAS, which is the prospective multicenter study across Japan published in 2012, has marked the milestone in the field of intracranial aneurysm research especially in the Japanese cohort. To make reasonable judgements in daily clinical activities, physicians should read the UCAS manuscript and its supplementary appendix carefully and understand the true natural course of unruptured intracranial aneurysms in Japan.

  Clipping is established as the most reliable method for the obliteration of cerebral saccular aneurysms. For surgical safety, anatomical structures around an aneurysm should be visualized under intracranial pressure control, and dissection of an aneurysm circumferentially is essential to provide the aneurysm with mobility and to secure a wide operative field. The procedure to detach perforators from a cerebral aneurysm wall is the most critical technique in the appropriate clipping strategy. Non-invasive preoperative evaluation using high-resolution MRI including 3T and 7T MRI is useful for the evaluation of the aneurysmal wall and perforators, respectively. Intraoperative monitoring of cerebral cortical blood flow and middle cerebral artery pressure may be useful, along with preoperative balloon test occlusion, for patients with unclippable internal carotid artery aneurysms, including thrombosed or blister-like aneurysms. The best treatment strategies for complex dissection in the posterior circulation that require artery occlusion with revascularization should be discussed between the surgical team and the endovascular team. The current status and future prospects of the surgical treatment of cerebral aneurysms are reviewed.

  Flow diverters (FDs) have recently been developed as innovative endovascular devices to treat intracranial aneurysms. FDs can alter and reduce the blood flow into the aneurysmal sac, and subsequently induce progressive aneurysmal thrombosis while preserving the patency of the surrounding small vessels and perforators. Because FD therapy is superior to conventional endosaccular coil embolization with its high complete occlusion rate and low risk of recurrence, it is expected to be one of the most important breakthroughs in the treatment of large and giant intracranial aneurysms. But because there are the continuing risks of morbidity and neurological mortality, appropriate case selection is mandatory for the effective use of FDs.

  Unruptured cerebral arteriovenous malformations (AVMs) have diverse pathological conditions in individual cases. There are multiple treatment strategies, and treatment risks vary greatly from case to case. Therefore, it is difficult to determine an uniform treatment policy. Intermediate analysis of the ARUBA trial reported that conservative medical treatment is superior to invasive treatment for the purpose of preventing death and new stroke in patients with unruptured AVMs. Since its analysis includes minor changes on image examinations accompanied by minor symptoms in new symptomatic stroke, which is the main endpoint, its interpretation and application to clinical practice should be carefully performed. Due to the racial differences in AVM’s natural history, original research is needed in Japan, in which medical treatment group is set as standard treatment and the primary endpoint as long-term prognosis.

  When clinical deterioration caused by delayed cerebral ischemia occurs in patients with aneurysmal subarachnoid hemorrhage, Japanese neurosurgeons often call it symptomatic cerebral vasospasm. However, it is well known that many factors contribute to the development of ischemic symptoms or cerebral infarction in patients with angiographic vasospasm, while delayed cerebral ischemia that is not associated with angiographic vasospasm can occur. Thus, the term ‘symptomatic cerebral vasospasm’ is no longer used in the guidelines published by the American Stroke Association since 2012. In a clinical setting, as accurate, reliable, and sensitive tests are not available to measure delayed cerebral ischemia yet, the guidelines recommend that delayed cerebral ischemia be assessed by the combination of the presence of clinical neurological deterioration and morphologically defined vasospasm, after excluding any identical cause on clinical assessment, computed tomography, magnetic resonance imaging or laboratory studies. To improve subarachnoid hemorrhage patient outcomes, we need to better understand the pathophysiology of delayed cerebral ischemia and to develop novel therapies to augment modern standard treatments.

  Approximately 1% of all professional musicians have musician’s dystonia (MD), and half of them give up their careers because they can’t be cured even when treated with botulinum toxin therapy and medication. For these patients, our hospital performs an operation that thermocoagulates the ventro-oral (Vo) nucleus of the thalamus (Vo-thalamotomy) which provides a dramatic and long-lasting improvement. But this treatment can’t be adapted to people who have a high surgery risk. Often Gamma Knife Vo-thalamotomy is adopted to treat medically refractory tremor. But the treatment has not been used for MD. Therefore, in one such surgically risky patient we decided to try Gamma Knife Vo-thalamotomy for MD and we obtained a good surgical outcome.

  The solitary fibrous tumor (SFT) is a relatively rare tumor among primary brain tumors. The NAB2-STAT6 fusion gene is a driver mutation of SFT and has genetic changes similar to those of hemangiopericytoma (HPC). Recently, various NAB2-STAT6 genotypes have been confirmed, and the relationship between genotypes and malignancy has been reported.

  A 49-year-old woman was referred to our department because of a 2-week history of left occipital headache and nausea. Brain magnetic resonance imaging (MRI) showed a well-demarcated and strongly enhanced mass with multi cystic compartments in the left occipital region. The mass was approximately 40 mm in diameter. A subarachnoid space was found between the tumor and the left occipital lobe, suggesting a extramedullary situated tumor. However, there was no dural tail sign. Surgical resection of the tumor was performed. The tumor was mildly elastic and hard and bleed easily. The tumor was grayish, with a clear boundary between the tumor and the brain surface. The tumor was resected sub-totally because it had invaded into the left transverse sinus. Histological examination showed moderate cellularity with round or oval nuclei, collagenous stroma, 1 mitosis per 10 high-power fields, and no necrotic areas. Immunohistochemical examination showed diffuse positivity for STAT 6 and CD 34. Genetic analysis showed NAB2 exon 6-STAT6 exon 17 fusion gene. We finally diagnosed SFT.