Congenital and acquired anomalies of the basilar artery: A pictorial essay

INTRODUCTION

The basilar artery is one of the two cases in our body where an arterial vessel is formed by the union of two others - the vertebral arteries. It provides vascular supply to essential structures for the main vital functions; the posterior cerebral arteries originate from it as terminal branches, and form part of the anastomotic circle of Willis.

IMAGING FINDINGS

Congenital and acquired anomalies of the basilar trunk are described. We provide a schematic and detailed representation of normal anatomical variants - mainly represented by the fenestrated basilar artery or the persistence of carotid-basilar anastomosis; course anomalies are also illustrated, with reference to neuro-vascular conflicts and dolichoectasia. Among congenital anomalies, this pictorial review also shows the variants of the basilar origin, such as in the case of basilar trunk arising from only one of the two vertebral arteries, and the calibre changes - which are represented by aneurysm and hypoplasia. The latter appears to be a risk factor for posterior circulation stroke, when associated with a bilateral posterior foetal variant.Among the acquired forms, this pictorial essay describes some clinical cases of dissections, non-congenital aneurysms, thrombosis and tumour with vascular encasing or compression of basilar artery.

CONCLUSION

CT angiography and MRI allow us to study the posterior intracranial circulation in detail, providing useful pre-treatment information. Therefore, knowledge of congenital or acquired anomalies of the basilar artery is essential for radiologists, neuroradiologists and neurosurgeons.

[Vertebrobasilar insufficiency caused by extravasal compression of the vertebral artery in the second segment]

OBJECTIVE

To develop indications for surgical treatment for positional disorders of blood flow in the vertebral-basilar territory caused by the damage to the V2-V3 segment of the vertebral artery (VA).

MATERIAL AND METHODS

One hundred and fourteen patients with systemic and non-systemic dizziness were studied. To assess the state of the VA, blood circulation of the posterior cranial fossa and the base of the brain, ultrasound duplex scanning of blood vessels, selective angiography, MRI, single photon emission computed tomography (SPECT) of the brain and neuropsychological testing were performed. Patients were divided into three groups according to the severity of clinical manifestations of vertebrobasilar insufficiency (VBI).

RESULTS

According to ultrasound data, patients of the third group with severe VBI had signs of extravasal compression in 94.3% of cases. In the same group, there was an increase in the systolic-diastolic (S/D) ratio by more than 2.5-3 times, as well as an increase in the resistive index (RI) by more than 1.75 units and pulsation index (PI) more than 2.2 units in V2-V3 segments of VA. In 42.9% of patients of the third group, zones of a decrease in the accumulation of 99mTc-ECD by more than 20% were found in the occipital region during the De Klein test. A direct correlation was established between the clinical manifestations of VBI and a decrease in perfusion during SPECT by 20% or more with the De Klein test (r=0.7). We developed an algorithm for diagnosing high-grade VBI with subsequent identification of a causal relationship with extravasal component effects on VA in the second segment. Indications for surgical intervention were determined in 33 patients with clinical manifestations of blood flow decompensation in the posterior cranial fossa.

CONCLUSION

Decreased blood flow velocity in the vertebral or basilar artery by more than 50% with a decrease in PI, breath holding index <0.7 in the hypercapnic test, and no increase in blood flow velocity in a phototest and, in addition, the >20% defect of 99mTc-ECD accumulation in the posterior parts of the brain during SPECT with a De Klein test are the criteria for decompensation of blood flow in the vertebral-basilar territory, requiring surgical correction.

Anomalous vasculature in the neck diagnosed by ultrasound

Anomalous vascular anatomy was detected in the neck of a 52-year-old female with a Klippel-Feil anomaly. Ultrasound identified three separate arteries in the left carotid sheath without any branching or bifurcations. The vascular waveforms were used to identify the vessels as the internal carotid artery, external carotid artery and vertebral artery. This rare vascular anomaly was confirmed with CT angiography.

Assessing the Relationship between Atherosclerotic Cardiovascular Disease Risk Score and Carotid Artery Imaging Findings

BACKGROUND AND PURPOSE

To characterize the relationship between computed tomography angiography (CTA) imaging characteristics of carotid artery and the 10-year risk of atherosclerotic cardiovascular disease (ASCVD) score.

METHODS

We retrospectively identified all patients who underwent a cervical CTA at our institution from January 2013 to July 2016, extracted clinical information, and calculated the 10-year ASCVD score using the Pooled Cohort Equations from the 2013 ACC/AHA guidelines. We compared the imaging features of artery atherosclerosis derived from the CTAs between low and high risk.

RESULTS

One hundred forty-six patients met our inclusion criteria. Patients with an ASCVD score ≥7.5% (64.4%) had significantly more arterial stenosis than patients with an ASCVD score <7.5% (35.6%, P < .001). Maximal plaque thickness was significantly higher (mean 2.33 vs. .42 mm, P < .001) and soft plaques (55.3% vs. 13.5%, P < .001) were significantly more frequent in patients with an ASCVD score ≥7.5%. However, among patients with a 10-year ASCVD score ≥7.5%, 33 (35.1%) had no arterial stenosis, 35 (37.2%) had a maximal plaque thickness less than. 9 mm, and 42 (44.7%) had no soft plaque. Furthermore, among the patients with a 10-year ASCVD score <7.5%, 8 (15.4%) had some arterial stenosis, 8 (15.4%) had a maximal plaque thickness more than. 9 mm, and 7 (13.5%) had soft plaque.

CONCLUSION

There is some concordance but not a perfect overlap between the 10-year ASCVD risk scores calculated from clinical and blood assessment and carotid artery imaging findings.

The cerebral basal arterial network: morphometry of inflow and outflow components

The aim of this project was to study how the morphology of the incoming and outgoing arterial components of the cerebral basal arterial network influence the blood flow to the brain. The cerebral basal arterial network consists of the circulus arteriosus cerebri anteriorly and the basilar artery posteriorly. Diameters of inflow vessels (bilateral vertebral and internal carotid arteries), connecting vessels (anterior communicating, basilar and bilateral posterior communicating arteries) and outflow vessels (anterior, middle and posterior cerebral arteries) were measured and cross-sectional areas calculated in 51 cadaveric brain specimens. The individual and the average cross-sectional areas of inflow arteries (51.43 mm² ) were significantly bigger than the major outflow arteries (37.76 mm² ) but smaller than the combined cross-sectional areas of outflow (37.76 mm² ) and connecting (25.33 mm² ) arteries. The difference in the size of arterial cross-sectional area and the presence of the connecting arteries in the cerebral basal arterial network provides a mechanism for lowering peaks in pressure, and demonstrates a function of the cerebral basal arterial network.