The prevalence of unruptured cerebral aneurysms (UCAs) in elderly patients is increasing in our aging population. UCA management in elderly patients has some difficulties, such as reduced life expectancy, increased comorbidities and treatment risks, and poor prognosis in case of rupture. In this review article, we summarize the most recent findings on the natural history, therapeutic options and treatment results for UCAs exclusively in elderly patients, and describe possible medical treatments for patients with UCAs.

The efficacy of mechanical thrombectomy with stent retrievers for emergent large vessel occlusion has been proved by randomized trials. Mechanical thrombectomy is increasingly being adopted in Japan since stent retrievers were first approved in 2014. An urgent clinical task is to offer structured systems of care to provide this treatment in a timely fashion to all patients with emergent large vessel occlusion. Treatment with flow-diverting stents is currently a preferred treatment option worldwide for large and giant unruptured aneurysms. Initial studies reported high rates of complete aneurysm occlusion, even in large and giant aneurysms, without delayed aneurysmal recanalization and/or growth. The Pipeline Embolic Device is a flow diverter recently approved in Japan for the treatment of large and giant wide-neck unruptured aneurysms in the internal carotid artery, from the petrous to superior hypophyseal segments. Carotid artery stenting is the preferred treatment approach for carotid stenosis in Japan, whereas it remains an alternative for carotid endarterectomy in Europe and the United States. Carotid artery stenting with embolic protection and plaque imaging is effective in achieving favorable outcomes. The design and conclusions of a randomized trial of unruptured brain arteriovenous malformations (ARUBA) trial, which compared medical management alone and medical management with interventional therapy in patients with an unruptured arteriovenous brain malformation, are controversial. However, the annual bleeding rate (2.2%) of the medical management group obtained from this study is worthy of consideration when deciding treatment strategy.

There are several anomalies of the middle cerebral artery (MCA) in humans, such as accessory MCA, duplicated MCA, fenestration of MCA, and duplicated origin of MCA. Recently, unfused or twig-like MCA, which indicates MCA trunk occlusion with collateral plexiform arterial network, have been reported. During the embryonic stage, MCA is thought to generate from plexiform arterial twigs arising from the anterior cerebral artery, and these twigs form the definitive MCA by fusion and regression at the end of the development stage. Any interruption during the fusion of the arterial twigs may result in MCA anomalies, and the unfused or twig-like MCA, especially, is hypothesized to be the persistent primitive arterial twigs. Clinically, it is challenging to differentiate the unfused or twig-like MCA from unilateral moyamoya disease, in which stenotic change begins at the MCA. The knowledge of the anomalies of the MCA is important to perform a safe surgical or endovascular intervention.

The primitive carotid-vertebrobasilar anastomoses are primitive embryonic cerebral vessels that temporarily provide arterial supply from the internal carotid artery to the longitudinal neural artery, the future vertebrobasilar artery in the hindbrain. Four types known are the trigeminal, otic, hypoglossal, and proatlantal intersegmental arteries. The arteries are accompanied by their corresponding nerves and resemble an intersegmental pattern. These vessels exist in the very early period of cerebral arterial development and rapidly involute within a week. Occasionally, persistence of the carotid to vertebrobasilar anastomosis is discovered in the adult period, and is considered as the vestige of the corresponding primitive embryonic vessel. The embryonic development and the segmental property of the primitive carotid-vertebrobasilar anastomoses are discussed. This is followed by a brief description of the persisting anastomoses in adults.

As the safety and effectiveness of urgent carotid artery stenting (CAS) for neurologically progressing patients remain controversial, we retrospectively analyzed the outcome of urgent CAS based on the patients’ pathophysiological condition and neuroimaging findings. We divided 71 patients who underwent CAS within 14 days of stroke onset into two groups. Group 1 (n = 35) was comprised of patients with progressing neurologic signs and a reversible ischemic penumbra on magnetic resonance images (MRI). They were treated by urgent CAS. Group 2 (n = 36) was neurologically stable and underwent prophylactic CAS. In all patients we recorded the National Institutes of Health Stroke Scale (NIHSS) score and the modified Rankin scale (mRS). Urgent CAS resulted in significant improvement in the NIHSS score, when compared before and after CAS in group 1 (5.3 ± 4.3, P < 0.01). The rate of good outcomes (mRS 0–2 at 3 months post-CAS) was 48.6% in group 1, and 75% in group 2. The cumulative incidence of ipsilateral stroke between 31 days and 1 year was 5.9% in group 1, and 0% in group 2. The procedural complication rate was similar in both groups (group 1: 5.7%, n = 2; group 2: 5.6%, n = 2). No patient suffered a symptomatic intracerebral hemorrhage. When the pathophysiological status and neuroimaging findings are used to determine patient eligibility for urgent CAS, this treatment improve neurologic outcome and can be performed as safely as prophylactic CAS in our cohort of patients with acute ischemic stroke.

Occipital artery (OA) to the posterior inferior cerebellar artery (PICA) bypass is indispensable for the management of complex aneurysms of the PICA that cannot be reconstructed with surgical clipping or coil embolization. Although OA-PICA bypass is a comparatively standard procedure, the bypass is difficult to perform in some cases because of the location and situation of the PICA. We describe the usefulness of the unilateral trans-cerebellomedullary fissure (CMF) approach for OA-PICA bypass. Thirty patients with aneurysms in the vertebral artery (VA) or PICA were treated using OA-PICA bypasses between 2010 and 2015. Among them, the unilateral trans-CMF approach was used for OA-PICA anastomosis in 13 patients. The surgical procedures performed on and the medical records of all the patients were retrospectively reviewed. The unilateral trans-CMF approach was performed for two reasons depending on the PICA location or situation: either because the caudal loop could not be used as a recipient artery because of arterial dissection (3 patients) or because the tonsillo-medullary segment that was located in the upper part of the CMF did not have a caudal loop that was large enough (10 patients). The trans-CMF approach provided a good operative field for the OA-PICA bypass and the anastomosis were successfully performed in all patients. When the recipient artery was located in the upper part of the CMF, the unilateral trans-cerebello-medullary fissure approach provided a sufficient operative field for OA-PICA anastomosis.

Characterization of vessels distal from occluded site is important when considering endovascular revascularization therapy (EVT) for acute ischemic stroke. The goal of this study was to assess the clinical value of intra-arterial contrasted high-resolution cone-beam computed tomography from the ascending aorta (Ao-CBCT) for visualization of the vessels distal from occluded site. Acute ischemic stroke patients with large vessel occlusion who were to undergo EVT were evaluated. In EVT, digital subtraction angiography (DSA) and Ao-CBCT were performed with local anesthesia. Ao-CBCT images were acquired in a 20-second rotational scan. Contrast medium was injected (1 mL/s for a total of 30 seconds using a 4-Fr catheter and an imaging delay of 10 seconds) from the ascending aorta. We assessed the image quality of Ao-CBCT and compared the visualization of the vessels distal from occluded site among magnetic resonance angiography (MRA), DSA and Ao-CBCT. We analyzed 14 patients (mean age, 66 years; three female patients). Stroke subtypes were cardiogenic (n = 6), atherothrombotic (n = 5) and others/unknown (n = 3). Occluded sites were middle cerebral artery (MCA) M1 (n = 8), MCA M2 (n = 2), internal carotid artery (ICA) (n = 2), MCA M4 (n = 1) and basilar artery (BA) (n = 1). All obtained Ao-CBCT images successfully characterized the vessels distal from occluded site, and 11 images (79%) were excellent. In all cases, Ao-CBCT images could depict distal vessels with more detail when compared with MRA and DSA. Ao-CBCT is an efficient method to obtain detailed information regarding vessels distal from occluded site when compared with conventional examination methods.