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The vertebral arteries represent in the adult the main blood supply of the posterior cranial fossa, even if they appear relatively late during the embryological life. We reviewed all the most important steps of the vertebral artery's embryological development and the most common variants that can occur in the adult. The aim of this review is to summarize the main events of the development of this artery and to give an embryological explication for the most common variants of this artery., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Background and Purpose: Internal carotid artery (ICA) agenesis is a rare anatomical variant that can involve different segments of the ICA. Although many authors proposed their own classifications of this variant basing on different criteria, none of these allows to include all the cases described in the literature. The aim of the authors is to propose a new classification that allows to include all cases of ICA agenesis described until now., Materials and Methods: The study is based on the review of all the cases of ICA agenesis described in the literature and of the classifications already proposed. After the analysis of these cases, we looked for the limits of each classification to elaborate a new more complete one., Results: We found 228 cases of ICA agenesis. Among them 40 were not includible in the existing classifications. For this reason, we proposed a new classification based on the type of flow compensation and on the embryological events that determine the different variants. The flow is compensated in Type I by the Circle of Willis; in Type II by the non-regression of an embryonic artery; in Type III by the presence of an arterio-arterial anastomosis and in Type IV by external-internal carotid arteries anastomoses., Conclusion: After the literature review, we proposed a new comprehensive classification based on the detailed analysis of arterial embryology. Even if all the embryological details that determine this complex variant are not completely understood yet, this classification allows to include all the cases described in literature., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Objective: Acute hydrocephalus is a frequent complication after aneurysmal subarachnoid hemorrhage (aSAH). Among patients needing CSF diversion, some cannot be weaned. Little is known about the comparative neurological, neuropsychological, and health-related quality-of-life (HRQOL) outcomes in patients with successful and unsuccessful CSF weaning. The authors aimed to assess outcomes of patients by comparing those with successful and unsuccessful CSF weaning; the latter was defined as occurring in patients with permanent CSF diversion at 3 months post-aSAH., Methods: The authors included prospectively recruited alert (i.e., Glasgow Coma Scale score 13-15) patients with aSAH in this retrospective study from six Swiss neurovascular centers. Patients underwent serial neurological (National Institutes of Health Stroke Scale), neuropsychological (Montreal Cognitive Assessment), disability (modified Rankin Scale), and HRQOL (EuroQol-5D) examinations at < 72 hours, 14-28 days, and 3 months post-aSAH., Results: Of 126 included patients, 54 (42.9%) developed acute hydrocephalus needing CSF diversion, of whom 37 (68.5%) could be successfully weaned and 17 (31.5%) required permanent CSF diversion. Patients with unsuccessful weaning were older (64.5 vs 50.8 years, p = 0.003) and had a higher rate of intraventricular hemorrhage (52.9% vs 24.3%, p = 0.04). Patients who succeed in restoration of physiological CSF dynamics improve on average by 2 points on the Montreal Cognitive Assessment between 48-72 hours and 14-28 days, whereas those in whom weaning fails worsen by 4 points (adjusted coefficient 6.80, 95% CI 1.57-12.04, p = 0.01). They show better neuropsychological recovery between 48-72 hours and 3 months, compared to patients in whom weaning fails (adjusted coefficient 7.60, 95% CI 3.09-12.11, p = 0.02). Patients who receive permanent CSF diversion (ventriculoperitoneal shunt) show significant neuropsychological improvement thereafter, catching up the delay in neuropsychological improvement between 14-28 days and 3 months post-aSAH. Neurological, disability, and HRQOL outcomes at 3 months were similar., Conclusions: These results show a temporary but clinically meaningful cognitive benefit in the first weeks after aSAH in successfully weaned patients. The resolution of this difference over time may be due to the positive effects of permanent CSF diversion and underlines its importance. Patients who do not show progressive neuropsychological improvement after weaning should be considered for repeat CT imaging to rule out chronic (untreated) hydrocephalus.

The anterior cerebral artery (ACA) and the anterior communicating artery (AComA) are important arteries of the telencephalon and are prominent location for cerebral aneurysms. Their embryological development is closely linked, and explains the possible variants seen in adults. In this paper, we present details related to the development of these two arteries, focusing on some variants such as the infra-optic course of the ACA, the unpaired ACA, and the persistent primitive olfactory artery., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Objective: While prior retrospective studies have suggested that delayed cerebral ischemia (DCI) is a predictor of neuropsychological deficits after aneurysmal subarachnoid hemorrhage (aSAH), all studies to date have shown a high risk of bias. This study was designed to determine the impact of DCI on the longitudinal neuropsychological outcome after aSAH, and importantly, it includes a baseline examination after aSAH but before DCI onset to reduce the risk of bias., Methods: In a prospective, multicenter study (8 Swiss centers), 112 consecutive alert patients underwent serial neuropsychological assessments (Montreal Cognitive Assessment [MoCA]) before and after the DCI period (first assessment, < 72 hours after aSAH; second, 14 days after aSAH; third, 3 months after aSAH). The authors compared standardized MoCA scores and determined the likelihood for a clinically meaningful decline of ≥ 2 points from baseline in patients with DCI versus those without., Results: The authors screened 519 patients, enrolled 128, and obtained complete data in 112 (87.5%; mean [± SD] age 53.9 ± 13.9 years; 66.1% female; 73% World Federation of Neurosurgical Societies [WFNS] grade I, 17% WFNS grade II, 10% WFNS grades III-V), of whom 30 (26.8%) developed DCI. MoCA z-scores were worse in the DCI group at baseline (-2.6 vs -1.4, p = 0.013) and 14 days (-3.4 vs -0.9, p < 0.001), and 3 months (-0.8 vs 0.0, p = 0.037) after aSAH. Patients with DCI were more likely to experience a decline of ≥ 2 points in MoCA score at 14 days after aSAH (adjusted OR [aOR] 3.02, 95% CI 1.07-8.54; p = 0.037), but the likelihood was similar to that in patients without DCI at 3 months after aSAH (aOR 1.58, 95% CI 0.28-8.89; p = 0.606)., Conclusions: Aneurysmal SAH patients experiencing DCI have worse neuropsychological function before and until 3 months after the DCI period. DCI itself is responsible for a temporary and clinically meaningful decline in neuropsychological function, but its effect on the MoCA score could not be measured at the time of the 3-month follow-up in patients with low-grade aSAH with little or no impairment of consciousness. Whether these findings can be extrapolated to patients with high-grade aSAH remains unclear. Clinical trial registration no.: NCT03032471 (ClinicalTrials.gov).

Background: Pericallosal artery aneurysms differ from other cerebral aneurysms for the difficulty in establishing proximal vascular control during surgical clipping. A frontomedial craniotomy with combined pterional and interhemispheric approach allows obtaining a better proximal control., Materials and Methods: We present our surgical technique to achieve a proximal vessel control in pericallosal artery aneurysm clipping using a combined pterional and interhemispheric approach through frontomedial craniotomy. This surgical technique is illustrated by an intraoperative video., Conclusion: Proximal control for pericallosal artery aneurysm clipping can be challenging. In selected cases, a single craniotomy allows performing two approaches and obtaining a safer proximal control for surgical clipping., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background: Dorsal pons cavernoma can be approached through telo-velar approach instead of transvermian approach, with lower risk of neurological deficits since it uses natural clefts to reach the floor of the fourth ventricle., Materials and Methods: We present our surgical technique for telo-velar approach to address pathologies of the dorsal pons, assisted by neuronavigation and neuromonitoring. This surgical technique is illustrated by a surgical video of a dorsal pons cavernoma., Conclusion: Dorsal pons cavernomas can be reached through telo-velar approach after suboccipital midline craniotomy. The accurate patient positioning, cisternal dissection, and neuromonitoring use are mandatory to avoid neural injuries and identify the safe entry points into the brainstem.

The ophthalmic artery has one of the most fascinating embryologic developments among the craniofacial arteries. Most of the ophthalmic artery orbital branches develop from the formation and regression of the stapedial artery and share their origin with dural branches of the ophthalmic artery. The concomitant embryologic development of the ophthalmic artery and middle meningeal artery explains adequately the important varieties of anastomosis between these 2 arteries. It also explains the presence of many dural branches from the ophthalmic artery. In this review, we focused on dural branches of the ophthalmic artery with the description of rare variations possible, in particular the ophthalmic artery origin of the middle meningeal artery and the ophthalmic artery origin of the marginal tentorial artery., (© 2021 by American Journal of Neuroradiology.)

Background: The middle cerebral artery (MCA) bifurcation represents the most frequent location for intracranial aneurysms. Often, the aneurysmal dome can hide the origin of perforating arteries from the M1 segment during the surgical clipping causing ischemic lesions and worse clinical outcome. The aim of this paper is to analyze the association between the orientation of the aneurysm sac and the clinical and radiological outcomes after surgical clipping., Methods: Data from 50 MCA bifurcation clipped aneurysms in 47 patients were collected retrospectively. Three different groups were identified according to the aneurysmal sac orientation: anterior-inferior, posterior and superior. A possible association between the aneurysmal sac projection and the outcome was searched through a univariable logistic regression analysis., Results: Statistical analysis showed significant correlation between the radiologic evidence of post-operative ischemia in the posterior group (p = 0.046, RR = 1.65) and an increased risk in the superior orientation group (p = 0.145, RR = 1.38). The anterior-inferior group was, instead, significantly associated with no evidence of radiologic ischemia (p = 0.0019, RR = 0.58)., Conclusion: The orientation of the aneurysmal dome and sac represents a fundamental feature to be considered during the surgical clipping of the MCA aneurysms. Indeed, its posterior and superior projection is associated with a higher incidence of radiologic ischemic lesions due to the origin of perforating arteries from M1 segment behind the aneurysmal sac. The anterior-inferior orientation, on the contrary, is associated with a lower risk., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Paroxysmal diplopia could be the expression of a multitude of clinical or anatomical conditions. Both ophthalmological and neurological pathologies could be responsible of this symptom. Rarely, a neurovascular conflict involving the oculomotor nerve is the etiology. We present the case of a 75-year-old man who presented for a 20-year history of transient vertical diplopia. The radiological exams demonstrated the presence of a neurovascular conflict between the right oculomotor nerve and a fetal-type posterior communicating artery. This fetal posterior communicating artery had an aberrant downward course that compressed the third cranial nerve. Few cases of neurovascular conflict interesting the third cranial nerve were described in the literature whom the responsible artery was generally the superior cerebellar artery. No case of oculomotor nerve compression by the posterior communicating artery was published. Authors have reviewed the literature and discuss the embryology of the posterior communicating artery, pathophysiology, radiological findings, and therapeutic possibility.

The middle meningeal artery is the major human dural artery. Its origin and course can vary a great deal in relation, not only with the embryologic development of the hyostapedial system, but also because of the relationship of this system with the ICA, ophthalmic artery, trigeminal artery, and inferolateral trunk. After summarizing these systems in the first part our review, our purpose is to describe, in this second part, the anatomy, the possible origins, and courses of the middle meningeal artery. This review is enriched by the correlation of each variant to the related embryologic explanation as well as by some clinical cases shown in the figures. We discuss, in conclusion, some clinical conditions that require detailed knowledge of possible variants of the middle meningeal artery., (© 2020 by American Journal of Neuroradiology.)

The stapedial artery is an embryonic artery that represents the precursor of some orbital, dural, and maxillary branches. Although its embryologic development and transformations are very complex, it is mandatory to understand the numerous anatomic variations of the middle meningeal artery. Thus, in the first part of this review, we describe in detail the hyostapedial system development with its variants, referring also to some critical points of ICA, ophthalmic artery, trigeminal artery, and inferolateral trunk embryology. This basis will allow the understanding of the anatomic variants of the middle meningeal artery, which we address in the second part of the review., (© 2020 by American Journal of Neuroradiology.)

Purpose: The recurrent artery of Heubner (RAH) is a very fascinating artery for various reasons. The first one is its early development in the embryologic and phylogenic life. The second one is the discrepancy between its diameter and its functional importance and the last but not least reason is the many variations of origin and course of this artery., Methods: For more than a century, numerous studies furnished important information about variations in origin, course, and parenchymal territory of the RAH. The most important anomaly concerning the RAH is the accessory middle cerebral artery and well-illustrates the complexity of its embryologic development., Conclusion: For these reasons, authors provide a review of anatomical variations of this artery that could be encountered with a particular attention given to the history and embryological knowledge.

Purpose: The ophthalmic artery (OA) has one of the most complex anatomy and the most fascinating embryological development., Methods: The complexity of the embryologic development of the OA resides in the implication of three different embryological systems: the carotid system, the stapedial system, and the ventral pharyngeal system., Results: This explains very well the numerous variations in origin of the OA and the importance of vascular anastomoses developed with branches of the external carotid artery and with the middle meningeal artery., Conclusion: In this review, authors propose a comprehensive description of different hypotheses on the embryologic development of the OA and, in a second part, explain all anatomical variations and clinical implications of this artery.

Background and Purpose: Moyamoya disease is a chronic neurovascular steno-occlusive disease of the internal carotid artery and its main branches, associated with the development of compensatory vascular collaterals. Literature is lacking about the precise description of these compensatory vascular systems. Usually, the posterior circulation is less affected, and its vascular flow could compensate the hypoperfusion of the ICA territories. The aim of this study was to describe these natural connections between the posterior cerebral artery and the anterior cerebral artery necessary to compensate the lack of perfusion of the anterior cerebral artery territories in the Moyamoya population., Materials and Methods: All patients treated for Moyamoya disease from 2004 to 2018 in 4 neurosurgical centers with available cerebral digital subtraction angiography were included. Forty patients (80 hemispheres) with the diagnosis of Moyamoya disease were evaluated. The presence of anastomoses between the posterior cerebral artery and the anterior cerebral artery was found in 31 hemispheres (38.7%)., Results: Among these 31 hemispheres presenting with posterior cerebral artery-anterior cerebral artery anastomoses, the most frequently encountered collaterals were branches from the posterior callosal artery (20%) and the posterior choroidal arteries (20%). Another possible connection found was pio-pial anastomosis between cortical branches of the posterior cerebral artery and the anterior cerebral artery (15%). We also proposed a 4-grade classification based on the competence of these anastomoses to supply retrogradely the territories of the anterior cerebral artery., Conclusions: We found 3 different types of anastomoses between the anterior and posterior circulations, with different abilities to compensate the anterior circulation. Their development depends on the perfusion needs of the territories of the anterior cerebral artery and can provide the retrograde refilling of the anterior cerebral artery branches., (© 2019 by American Journal of Neuroradiology.)