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Introduction: Fenestration, early bifurcation, and duplication of the posterior cerebral artery (PCA) and the so-called hyperplastic anterior choroidal artery (AChA), considered a variation of the PCA, are rare. We evaluated the prevalence and characteristic features of these PCA variations on magnetic resonance (MR) angiography. Methods: We reviewed intracranial MR angiographic images of 2402 patients examined using a 3-tesla scanner. Images from the skull base to the intracranial region were obtained using the standard time-of-flight technique. We excluded images of 52 patients with insufficient image quality or occlusion of the PCA(s) and retrospectively evaluated the images of 2350 patients using a picture archiving and communication system. Results: We observed PCA fenestration in eight (0.34 %) patients, most at the P1 segment and P1-P2 junction and all small in size, early bifurcation at the P1-P2 junction or proximal P2A segment in eight (0.34 %) patients, complete duplication in one patient, and hyperplastic AChA in 13 (0.55 %) patients. Eleven of the 13 hyperplastic AChAs supplied only the territory of the temporal branch of the PCA, and the remaining two supplied the entire territory of the PCA. Conclusion: We observed PCA variations in 30 (1.28 %) patients. We believe the name 'hyperplastic AChA' inaccurately describes variations of the PCA in which the AChA supplies part of or all of the territory of the PCA and propose 'accessory PCA' to describe an AChA that supplies part of the territory of the PCA or 'replaced PCA' to describe that vessel that supplies the territory all branches of the PCA. [ABSTRACT FROM AUTHOR]

Introduction: Persistent hypoglossal artery (PHA) is the second most common anastomosis between the carotid and vertebrobasilar systems and demonstrates some variations. We evaluated the prevalence of PHA on computed tomography (CT) angiography. We also evaluated characteristic features of PHA and its variants on magnetic resonance (MR) angiography. Methods: We retrospectively reviewed our database of 2,074 CT angiographic images obtained using either of two 64-slice multidetector CT scanners. We also reviewed our database of 7,646 MR angiographic images obtained using either of two 1.5-T or one 3.0-T imager. We could not determine the exact number of patients whose MR angiography included the hypoglossal canal. Most patients had or were suspected of having cerebrovascular diseases. Results: We found six usual PHAs arising from the cervical internal carotid artery on CT angiography among 2,074 patients. On MR angiography, we also found six additional usual PHAs (total 12, right/left = 6/6, male/female = 3/9), three right PHAs originating from the external carotid artery (ECA), and two posterior inferior cerebellar arteries (PICAs) arising from the ECA without connection to the vertebral artery. Conclusions: The prevalence of usual PHA diagnosed by CT angiography was 0.29 %, slightly higher than that reported for angiography and may be due to selection bias in the examined patients. We propose naming usual PHA 'type 1 PHA'; PHA originating from the ECA, of which we found three, 'type 2 PHA'; and PICA arising from the ECA, of which we found two, 'type 2 PHA variant.' [ABSTRACT FROM AUTHOR]

Introduction: Fenestrations of cerebral arteries are most common in the vertebrobasilar (VB) system, and magnetic resonance (MR) angiographic studies of these variations are sparse. Methods: We retrospectively reviewed MR angiographic images of 3,327 patients; images were obtained using two 1.5-T imagers and picked up fenestrations of the intracranial vertebral artery (VA), VB junction, and basilar artery (BA) for evaluation. Results: In 92 patients, we found 93 fenestrations (2.80%), which included 18 of the intracranial VA (0.54% prevalence), 6 of the VB junction (0.18%), and 69 of the BA (2.07%). Most VA fenestrations were large, and the posterior inferior cerebellar artery arose from the fenestrated segment in 10 patients (56%). Fenestrations of the VB junction were small and triangular. Sixty-five (94%) of the 69 BA fenestrations were located at the proximal segment and had small slit-like configurations. The anterior inferior cerebellar artery arose from the fenestrated segment in 27 patients (37%). We found 18 cerebral aneurysms in 16 (17%) of the 92 patients with fenestration but detected only one aneurysm at the fenestration. Conclusion: The overall prevalence of fenestrations of the intracranial VB system was 2.77%. We found associated cerebral aneurysms relatively frequently but rarely at the fenestration. [ABSTRACT FROM AUTHOR]

Introduction: The craniovertebral junction is clinically important. The vertebral artery (VA) in its several variations runs within this area. We report the prevalence of these VA variations on magnetic resonance angiography (MRA). Methods: We retrospectively reviewed MRA images, obtained using two 1.5-T imagers, of 2,739 patients, and paid special attention to the course and branching of the VA at the level of the C1-2 vertebral bodies. Results: There were three types of VA variation at the C1-2 level: (1) persistent first intersegmental artery (FIA), (2) VA fenestration, and (3) posterior inferior cerebellar artery (PICA) originating from the C1/2 level. The overall prevalence of these three variations was 5.0%. There was no laterality in frequency, but we found female predominance ( P < 0.05). We most frequently observed the persistent FIA (3.2%), which was sometimes bilateral. We found VA fenestration (0.9%) and PICA of C1/2 origin (1.1%) with almost equal frequency. Two PICAs of C1/2 origin had no normal VA branch. Conclusions: We frequently observed VA variations at the C1-2 level and with female predominance. The persistent FIA was most prevalent and sometimes seen bilaterally. Preoperative identification of these variations in VA is necessary to avoid complications during surgery at the craniovertebral junction. [ABSTRACT FROM AUTHOR]