Management strategy of the unruptured intracranial aneurysms (UIA) should be made by balancing rupture risk and management risk of aneurysms as well as patient’s physical and mental conditions. Rupture risks and its prediction models of UIA have been recently reported, but treatment risks needs to be further defined. In the meantime, unruptured intracranial aneurysms treatment score, which is a consensus decision tool whether individual aneurysms should be treated or conservatively managed, was also reported. These various tools can be used to support management decisions.

  However, each patient’s attitude, understanding of the natural history of aneurysms and treatment risks vary significantly, and, hence, risk communication method between patients and doctors needs to be improved. Other problems to be solved include : 1) Poor natural course and higher mortality of patients with UIA not due to UIA rupture, 2) Further clarification of modifiable factors influencing development and rupture of the aneurysms and development of medical treatment of aneurysms, 3) Developing guidelines of management of UIA in elderly, which carries higher rupture risk and poorer prognosis when ruptures. In this article, these issues are discussed.

  Selection of either direct surgery or endovascular treatment for patients with an intracranial aneurysm depends on individualized factors such as shape and location of the aneurysm in view of an advantage and a disadvantage of each therapeutic modality. Surgical clipping has the advantage of being able to deform an aneurysm into an appropriate shape under direct vision and shows its superiority in a complex-shaped aneurysm or an aneurysm from which a branch or a perforator originates. In order to achieve this purpose, surgeons must visualize all anatomical structures around an aneurysm, dissect an aneurysm circumferentially to provide the aneurysm with mobility and secure a wide operative field for the inspection from various angles. On the other hand, as surgeons cannot directly observe the blood flow in intracranial arteries during surgery, intraoperative monitoring such as doppler ultrasonography, indocyanine green (ICG) videoangiography and motor-evoked potential (MEP) monitoring is mandatory. Recently, large or broad-neck aneurysms have become indicated for endovascular treatment with advances in intracranial stents. However, surgical clipping is still an attractive therapeutic option for large aneurysms as it can completely block the blood flow at the neck. Another advantage of direct surgery is brought about revascularization by bypass surgery. Bypass surgery also plays an important role in combined treatment with endovascular therapy for complex aneurysms. To understand and utilize maximally the advantages of direct surgery will further improve the therapeutic result of patients with intracranial aneurysms.

  Intracranial aneurysms are a result of pathological damage to the normal arterial wall, which mainly consist of breakdown of the muscular middle layer and the internal elastic lamina. Therefore, the repair or reinforcement of the damaged arterial wall is necessary to achieve the improvement of the durability and curability in the intracranial aneurysm treatments. Because the endosaccular coil embolization simply occludes a part of the saccular dilation, the recurrence risk is very high in large or giant intracranial aneurysms with a large area of damaged arterial wall. Furthermore, the aneurysm induced mass effect may deteriorate due to the coil mass. Because flow diverter embolization has benefits, such as the repair of damaged arterial walls, preservation of the surrounding small, perforator vessels, and resolution of aneurysm-induced mass effect, it could be the first-line therapy of large intracranial aneurysms, with the exception of those acutely ruptured. However, the risks of procedure-related complications are relatively not low, and the long-term efficacy in the prevention of aneurysm rupture or recurrence has not yet been elucidated. Therefore, the decision of interventional strategies for large intracranial aneurysms requires an accurate assessment of the risks of existing treatment modalities compared with those of flow diverter embolization.

  Moyamoya disease is a chronic cerebrovascular disease with unknown etiology characterized by steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Increasing evidence suggests that surgical revascularization such as direct extracranial-intracranial bypass has potential roles not only for preventing ischemic stroke, but also for reducing the risk of re-bleeding in adult patients with hemorrhagic-onset. Based on these observations, we performed direct/indirect combined revascularization surgery for eleven affected hemispheres of ten adult patients presenting with intracranial hemorrhage. The results of revascularization surgeries were favorable in all patients, and no patient suffered cerebrovascular event during the follow-up period.

  After the ARUBA trial result were published, the surgical treatment of brain arteriovenous malformations (AVM) faces a new era. In this manuscript, the results of the ARUBA trial are summarized and the criticisms against this study are reviewed. The surgical skills required for safely removing of AVMs are summarized. Finally, the current and future status of the AVM surgery are mentioned.

  The front line treatment for dural arteriovenous fistulas (dAVF) is discussed. Source images from time of flight MRI give the definite diagnosis of dAVF. Additionally, maximum intensity projection/multi-planar reconstruction images of 3D-digital subtraction angiography provide the localization of the dAVF. Regarding transvenous embolization, we must consider the development of instruments and techniques to allow the superselective obliteration of the dAVF with preservation of the involved sinus. Onyx is another consideration, which would improve the obliteration rate in difficult cases.

  Chronic encapsulated intracerebral hematoma (CEIH) is a rare clinicopathological entity. Two cases of putaminal hemorrhage with CEIH are presented. Case 1 : A 54-year-old man who had sudden onset of left hemiparesis, left hypoesthesia, and dysphasia was admitted to our hospital. Computed tomography (CT) scan showed a right putaminal hemorrhage. Delirium, disorientation, and left hemiparesis worsened with progressive enlargement of the hematoma and peripheral edema. There was ring-like enhancement with gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). Despite aspiration of the hematoma liquid, marked peripheral edema continued. After a second operation, the hematoma and edema decreased gradually, and recurrence has not been observed for seven years after onset. Case 2 : A 36-year-old man who had a sudden onset of right hemiparesis and hypoesthesia was admitted to our hospital. CT scan showed a left putaminal hemorrhage. A left frontotemporal craniotomy was performed on the 27th day after admission. After thorough dissection of the sylvian fissure and a small corticotomy to the insula, a capsule was seen, containing. There was blood in various stages of organization in the capsule. A histological examination showed similarities to the membrane of chronic subdural hematoma. Postoperatively, the patient improved, and he was discharged ambulatory, and recurrence has not been observed as of three years from onset.

  The cause of CEIH is unknown. This unusual entity mimics brain tumors or abscess because of gradual growth and slowly progressive neurological deficits. The relevant literature was reviewed, and the pathogenesis of CEIH is discussed.

  We report a case of brain edema immediately after cranioplasty. A 57-year-old woman underwent surgical clipping for subarachnoid hemorrhage and decompressive craniectomy. She had cranioplasty on the 83rd hospital day.

  Although the surgery was completed uneventfully, CT of the head showed brainstem edema immediately after the cranioplasty. The brainstem edema developed into cerebral and cerebellar edema, and ultimately brain death. We considered that a bone defect and midline shift may have caused asymptomatic sinking skin flap syndrome (SSFS). We considered further that the cause of the brain edema could have been deterioration of autoregulation, reperfusion, negative pressure by subgaleal drain, venous stasis, or SSFS. The fatality rate due to brain edema that occurs immediately after cranioplasty is high. Cranioplasty is a relatively simple surgery ; however, complications include seizure, infection, and epidural hematoma. It should also be kept in mind that brain edema may occur, and these complications must be explained to the families as an informed consent before surgery.