The pathophysiology of an intracranial aneurysm (IA) lies in the degenerative changes accompanied by thinning and weakening in vascular walls, which is modulated by macrophage-mediated inflammation and hemodynamic stress. Vessel wall imaging is a promising diagnostic tool for evaluating the property of the vascular wall. Although clipping is a treatment which enables us to reconstruct the normal vascular walls in IA patients, clipping is sometimes impracticable depending on the property of the IA wall. In such cases, proximal occlusion of the parent artery with bypass is selected as a treatment choice. However, remaining issues on this treatment are perforator thrombosis and incomplete occlusion of IAs. Complete intraaneurysmal thrombosis leads to a radical cure, but incomplete thrombosis is an aggravating factor for inducing inflammation and degenerative changes in the IA wall.

  Spontaneous intracranial hemorrhage, which is classified into intraparenchymal and intraventricular hemorrhage, are caused by hypertension or abnormal vessels, such as arteriovenous malformations and Moyamoya disease. Various types of surgical treatment are performed on patients with spontaneous intracranial hemorrhage. However, how surgical interventions contribute to disease prognosis remains unknown to date. The minimally invasive catheter evacuation followed by thrombolysis (MISTIE) Ⅲ trial, which was a multicenter phase Ⅲ trial, demonstrated that a greater hematoma reduction was associated with a more favorable prognosis, indicating that minimally invasive techniques performed during the acute phase may be useful for the successful treatment of intracranial hemorrhages. Neuroendoscopic surgery, which is also a minimally invasive technique, was recently developed. Surgical candidates for neuroendoscopic surgery at our institution are defined as patients having putaminal hemorrhage with a hematoma of more than 30ml, an intraventricular hematoma with a mass effect, and thalamic hemorrhage causing hydrocephalus, in accordance with the operative criteria of the guidelines of The Japan Stroke Society. Regarding the neuroendoscope, a 2.7-mm or 4-mm rigid scope with a high-definition or 4K camera, together with a flexible scope (fiber or video scope), is used. As a brain retractor, a transparent sheath (Neuroport) is used. For hard hematomas, which are usually detected in patients being treated with anticoagulants or who are receiving dialysis, a large tubular retractor (ViewSite) is used. Furthermore, an important surgical instrument is irrigation suction with a cauterization terminal for monopolar coagulation. For hemostasis, oxidized cellulose with fibrin glue, or the recently developed flowable hemostatic matrix with thrombin are useful. In the wet field, complete hemostasis is possible, and the hematoma cavity and ventricle can be washed using artificial cerebrospinal fluid. For hematomas in the third ventricle or in the posterior part of the lateral ventricle, aspiration using a flexible scope is effective, and third ventriculostomy may also be performed for obstructive hydrocephalus. Our cases of intraventricular hemorrhage indicated that the outcomes of patients with caudate hemorrhage tended to be better than those with thalamic hemorrhage. In cases of bleeding from an abnormal blood vessel, endoscopic surgery should be performed carefully after confirming hemostasis. In the future, more detailed outcome evaluations regarding the higher brain functions of patients, the standardization of operations, development of a flexible scope, and new techniques to stop bleeding from abnormal vessels, such as endoscopic neck clipping in the wet field, are expected to be performed.

  Recently, recommendations of managing cerebral arteriovenous malformations (AVMs) with multimodal treatment in conjunction with the completion of the ARUBA study have significantly reduced the number of direct surgeries for AVMs. Nevertheless, favorable safety profiles and cure rates can still be achieved with appropriate patient selection and judicious use of intraoperative support devices. In this article, we present our experience in the direct surgery of AVMs in the present setting, and discuss the central role of surgery to promote treatment outcomes. In addition, it is important to utilize practice-based data to establish indication criteria that reflects surgical outcomes.

  An understanding of the pathophysiology and angioarchitecture is essential to determine appropriate treatment for patients with dural arteriovenous fistulas (DAVFs). Presentations of DAVF can vary according to the location and venous drainage pattern, and the indication for treatment of DAVF should take the natural history of the condition into account. Most cases of DAVF can be treated with endovascular therapy whose treatment outcome has been improved in parallel with the advances in imaging, catheters, and embolic materials. Recently, Onyx has been approved as an embolic agent for DAVF in Japan. However, the current treatment strategy for DAVF is not uniform. Therefore, it is important to consider individualized treatment strategy that involves an understanding of the vascular anatomy and hemodynamics of each case.

  Pipeline embolization device (PED) has grown in popularity as an alternative to both microsurgery and coil embolization for the treatment of large unruptured symptomatic internal carotid artery (ICA) aneurysms. However, little is known about its efficacy.

  We retrospectively evaluated patients with compressional symptoms caused by large unruptured ICA aneurysms who underwent endovascular treatment with the PED at our institution from January 2016 to September 2018. During the 12-month clinical follow-up, 10 patients (55.6%) had resolution or significant improvement of their cranial neuropathies.

  Patients who received treatment with PED within 180 days after onset were significantly more likely to demonstrate neurological improvement at follow-up (OR 56 ; 95%CI 2.93-1071.69).

  Endovascular treatment with PED for symptomatic ICA aneurysm is useful for improving neurological symptoms. Time from onset to treatment appears to be an important factor for good neurological outcome.

  Few clinical reports in the available literature have described thrombectomy for occlusion of a small cerebral artery.

  Case : A 61-year-old woman presented with impaired consciousness, aphasia and right-sided hemiparesis. The last known well to arrival time was 4 hours. CT and MRI revealed acute ischemia of the left thalamus and left occipital lobe and subacute ischemia of the right occipital lobe. MR angiography revealed occlusion of the left posterior cerebral artery. DSA revealed that the left posterior cerebral artery originated from the left posterior communicating artery, and we detected a small aneurysm in the left internal carotid artery-left posterior communicating artery. We performed thrombectomy via the left posterior communicating artery using the Penumbra system^® to avoid aneurysmal injury by a stent retriever. The Penumbra 3MAX^TM was placed at the site of occlusion in the left posterior cerebral artery and aspiration was performed leading to cerebral infarction (TICI) grade 3 recanalization of the left posterior cerebral artery. The patient's symptoms improved, and she was discharged with a modified Rankin Scale score of 2.