Prevalence and Clinical Implications of the Primitive Trigeminal Artery and its Variants: A Meta-Analysis.

BACKGROUND: The primitive trigeminal artery (PTA) is the most common and the largest persistent carotid-basilar anastomosis. Primitive trigeminal artery variants (PTAVs) are anastomoses between the internal carotid artery and cerebellar arteries. These vessels pose a risk of hemorrhagic or ischemic complications during neurosurgical procedures in the parasellar and intrasellar regions. The aim of this study was to determine the prevalence of both PTA and PTAVs and their clinically important anatomic features. METHODS: Major electronic databases were thoroughly searched for studies on PTA and PTAV. References in the included articles were also evaluated. Data regarding prevalence, laterality, origin, course patterns, and associated anomalies were extracted and pooled into a meta-analysis. RESULTS: A total of 39 studies (110,866 patients) were included in the meta-analysis. The total pooled prevalence estimate of PTA and PTAVs combined was 0.4% (95% confidence interval [CI], 0.3-0.5). Individually, PTA was present in 0.3% of patients and PTAV in 0.2%. Both arteries most often originated from the C4 internal carotid artery and took a course lateral to the dorsum sellae. The anterior inferior cerebellar artery type was the predominant PTAV (72.1%). Basilar artery hypoplasia was found in 42.5% of patients with a PTA. CONCLUSIONS: PTA and PTAVs are rare vessels, but they are clinically important because they can contribute to trigeminal neuralgia. Knowledge of the potential course of these arteries is essential in neuroradiology and neurosurgery, especially in minimally invasive procedures such as the endoscopic endonasal transsphenoidal approach to the pituitary gland and the percutaneous gasserian ganglion procedure.

Normal subtypes of the posterior part of the cerebral arterial circle in human fetuses.

BACKGROUND: Although centuries of the human CAC research are behind us, still there is a stimulus for the authors to describe something new or to add to the "archive" of already known facts about its angioarchitecture. METHODS: With normal configurations of the posterior part of the CAC in early prenatal status, 172 brains of human fetuses from the 13th to the 24th week were used in the purpose of investigation. Brain arteries were injected and microdissected using a surgical microscope. RESULTS: According to diameter values of vascular components in the posterior part of the CAC, 6 basic types and the corresponding number of their subtypes are formed. Incidences of bilateral transitory (18.6%), fetal (9.3%), and adult (33.1%) types, as well bilateral asymmetric types (fetal-transitory in 5.8%, adult-transitory in 14.5%, and adult-fetal in 18.6% of cases), proved that dominant configuration of posterior part had not been present in the period from the fourth to the sixth gestational month. CONCLUSION: The finding of normal subtypes of the posterior part of the CAC, as well as the absence of some subtypes, is a challenge for future studies of the posterior arterial pattern within vascular abnormalities or diseases.

Embryological basilar apex disposition as a risk factor of basilar apex aneurysm.

The pathogenesis of basilar apex aneurysm (BAA) are still poorly understood. Embryologically, basilar apex anatomical disposition is formed by the fusion of both caudal internal carotid divisions on the midline. To compare basilar apex morphology by embryological classification among patients with BAAs, anterior circulation aneurysms (ACAs), and controls. Prospectively collected data of 47 consecutive patients with unruptured BAAs (42 females and five males), age- and gender-matched 47 patients with unruptured ACAs, and 47 controls without any aneurysms were analyzed. Based on embryology, basilar apex morphology was classified into symmetric cranial fusion (SCrF), symmetric caudal fusion, and asymmetric fusion type. Posterior communicating artery (Pcom) was classified into hypoplastic, adult, or fetal type. The asymmetrical Pcom was defined as bilaterally different type Pcom. The ACAs located at the anterior communicating artery (n = 18), paraclinoid portion (n = 12), middle cerebral artery (n = 8), anterior cerebral artery (n = 5), the top of internal carotid artery (n = 2), and anterior choroidal artery (n = 2). Compared with the ACA group and controls, smoking, asymmetrical Pcom (fetal and adult type), and SCrF type were more prevalent in patients with BAAs by residual analysis. The multinomial logistic regression comparative analysis demonstrated that SCrF type was associated with BAAs (vs. ACA group; odds ratio, 13; 95% confidence interval, 3.8-41 and vs. controls; odds ratio, 25; 95% confidence interval, 5.4-121). The assessment of basilar apex morphology may aid in the understanding of the pathogenesis of BAA and the prediction of BAA formation.

Bilateral segmental agenesis of the vertebrobasilar junction: developmental and angiographic anatomy.

BACKGROUND AND PURPOSE: Bilateral vertebrobasilar junction agenesis is an exceptional anatomic variation. This article explores the angiographic characteristics of this variant and its embryologic mechanisms. MATERIALS AND METHODS: Two observations of bilateral agenesis of the vertebrobasilar junction are reported. A case of atheromatous disease of the vertebrobasilar junction is shown to highlight characteristics distinguishing such a lesion from the reported variant. RESULTS: In the 2 reported cases, the distal segment of both vertebral arteries (VAs) and the proximal portion of the basilar artery (BA) were absent. In addition, distal connections of the BA with the posterior cerebral arteries (PCA) were also lacking. As a consequence, the remaining portion of the BA was isolated from its usual sources of blood supply, which was provided by a persistent carotid-basilar anastomosis. CONCLUSION: The developmental mechanism underlying bilateral agenesis of the vertebrobasilar junction likely involves the anterior radicular artery of C1. This branch of the proatlantal artery normally becomes the adult distal VA and the proximal BA. The lack of cranial connection of the BA with the PCA may be secondary to the proximal vertebrobasilar agenesis and the resulting paucity of antegrade flow within the BA. Alternatively, the absence of both the proximal and distal connections of the BA could be the result of a similar, yet unknown, developmental mechanism. From a clinical standpoint, this vascular anomaly was discovered incidentally in our 2 patients, a finding consistent with the assumed congenital nature of the variant.

Basilar trunk aneurysms with associated fenestration treated by using Guglielmi detachable coils: two cases reports.

Basilar trunk saccular aneurysms associated with fenestration are infrequent. Surgical treatment of a basilar trunk aneurysm is difficult because of its anatomic environment and complicated surgical exposure. We experienced two cases of basilar fenestration aneurysm, and the patients were treated using Guglielmi detachable coils. The usefulness of 3-dimensional digital subtraction angiography and efficacy of endovascular treatment for basilar trunk aneurysms with associated fenestration is discussed in this article, and the relevant literature is reviewed.

Carotid-vertebrobasilar Anastomoses with Reference to Their Segmental Property.

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.

Transabdominal Insonation of Fetal Basilar Artery: A Feasibility Study.

BACKGROUND: Fetal anterior, middle, and posterior cerebral arteries have been studied using transabdominal Doppler ultrasound. We performed a feasibility study to determine whether basilar artery can be identified and blood flow velocities measured using transabdominal fetal Doppler ultrasound. METHODS: The basilar artery was identified in sagittal plane behind the clivus bone using directional color Doppler with 6-2 and 7-4 MHz curved array probes. The clivus was identified by hyperechoic linear signal anterior to junction of vertebral processes and occipital bone and superior to first vertebral body. The flow direction was away from the probe in the basilar artery consistent with caudo cephalic orientation. The Doppler ultrasound probe was placed at insonation angles of less than 30° at the visualized segment of the basilar artery. Peak systolic and end diastolic velocities were measured. RESULTS: We attempted insonation of the basilar artery in 20 fetuses. The basilar artery was adequately insonated in 18 fetuses with a mean gestational age of 27 weeks (range 19 to 38 weeks). The mean value (±SD) of peak systolic velocity of the basilar artery was 22.1 ± 8.5 cm/second (range 10.4-36.7 cm/second). The mean value (±SD) of end diastolic velocity was 6.8 ± 2.8 cm/second (range 3.5-13.5 cm/second). There was an increase in peak systolic velocity values according to gestational age of fetus. CONCLUSIONS: We demonstrate the feasibility of fetal basilar artery insonation using directional color Doppler ultrasound via transabdominal approach.

Chronic hypoxia modulates relations among calcium, myosin light chain phosphorylation, and force differently in fetal and adult ovine basilar arteries.

The present study tests the hypothesis that age-related differences in contractility of cerebral arteries from hypoxic animals involve changes in myofilament Ca2+ sensitivity. Basilar arteries from term fetal and nonpregnant adult sheep maintained 110 days at 3,820 m were used in measurements of cytosolic calcium concentration ([Ca2+]i), myosin light chain phosphorylation, and contractile tensions induced by graded concentrations of K+ or serotonin (5-HT). Slopes relating [Ca2+]i to tension were similar in fetal (0.83 +/- 0.07) and adult (1.02 +/- 0.08) arteries for K+ contractions but were significantly greater for fetal (3.77 +/- 0.64) than adult (2.00 +/- 0.13) arteries for 5-HT contractions. For both K+ and 5-HT contractions, these relations were left shifted in fetal compared with adult arteries, indicating greater Ca2+ sensitivity in fetal arteries. In contrast, slopes relating [Ca2+]i and %myosin phosphorylation for K+ contractions were less in fetal (0.37 +/- 0.08) than adult (0.81 +/- 0.07) arteries, and the fetal curves were right shifted. For 5-HT contractions, the slope of the Ca2+-phosphorylation relation was similar in fetal (0.33 +/- 0.09) and adult (0.33 +/- 0.23) arteries, indicating that 5-HT depressed Ca2+-induced myosin phosphorylation in adult arteries. For slopes relating %myosin phosphorylation and tension, fetal values (K+: 1.52 +/- 0.22, 5-HT: 7.66 +/- 1.70) were less than adult values (K+: 2.13 +/- 0.30, 5-HT: 8.29 +/- 2.40) for both K+- and 5-HT-induced contractions, although again fetal curves were left shifted relative to the adult. Thus, in hypoxia-acclimatized basilar arteries, a downregulated ability of Ca2+ to promote myosin phosphorylation is offset by an upregulated ability of phosphorylated myosin to produce force yielding an increased fetal myofilament Ca2+ sensitivity. Postnatal maturation reprioritizes the mechanisms regulating hypoxic contractility through changes in the source of activator Ca2+, the pathways governing myosin light chain phosphorylation, and its interaction with actin.

The development of noradrenaline-, acetylcholinesterase-, neuropeptide Y- and vasoactive intestinal polypeptide-containing nerves in human cerebral arteries.

The development of cerebrovascular nerves containing noradrenaline (NA), acetylcholinesterase (AChE), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) in the basilar artery was histochemically or immunohistochemically studied in human fetuses of various gestational ages. At the 12th week of gestation, nerve fibers containing NA and AChE appeared. Both types of nerve fibers consisted exclusively of the longitudinal nerve fibers (LNF) running along the basilar arteries. Subsequently, the circular nerve fibers (CNF) gradually increased and such development was then completed by the 20th week of gestation. NPY- and VIP-containing nerve fibers were detected in human fetal cerebral arteries in the 16th week of gestation, in the form of LNF. Subsequently, CNF gradually increased and development was completed by the 24th week of gestation. These results indicate that neuropeptide-containing nerve fibers, together with NA- and AChE-containing nerves, therefore contribute to the control of cerebral circulation in the later stages of embryogenesis in human cerebral arteries.

Complete duplication or extreme fenestration of the basilar artery.

We describe a 42-year-old man with complete duplication or extreme fenestration of the basilar artery. We review the developmental anatomy and embryology and discuss the possible clinical implications and associated findings of this anomaly.

Persistent nonfused segments of the basilar artery: longitudinal versus axial nonfusion.

Embryologic development of the basilar artery occurs along two axis systems: longitudinal fusion and axial fusion. Longitudinal fusion consists of midline fusion of paired ventral arteries and reflects the simplified pattern of arterial anatomy found in the spinal cord. Axial fusion consists of fusion of the distal basilar artery, which arises from the caudal division of the internal carotid artery, to the midbasilar agenesis to the posterior inferior cerebellar artery termination of the vertebral arteries. Persistent longitudinal nonfusion (or complete duplication) of the basilar artery is very rare, and persistent axial nonfusion is even rarer. We report one case of persistent longitudinal nonfusion of the basilar artery in a 3-year-old boy and a case of persistent axial nonfusion of the basilar artery in a 43-year-old man.

Saccular aneurysm associated with segmental duplication of the basilar artery. A morphological study.

Saccular aneurysm associated with segmental duplication (also called "fenestration") of the basilar artery is an anomaly that results from an embryonic fault. Reports of the treatment of the aneurysmal component have only recently appeared in the neurosurgical literature, and little has been written on the morphology of this anomaly. This study answers the need for information about its structure to the extent permitted by the examination of a single specimen. The specimen was obtained at postmortem examination. A cast of its interior features was made with a synthetic rubber. After the cast was removed, the entire anomaly was serially sectioned for histological study. Defects in the wall of the basilar artery were seen microscopically at each end of the fenestration. At the extensive proximal defect, a saccular aneurysm arose that bulged into the window between the two limbs of the segmental duplication and also presented dorsally and ventrally. It had fatally ruptured. The manner in which the fenestration was formed by intraluminal septa was also revealed.

Anatomy of segmental duplication in the human basilar artery. Possible site of aneurysm formation.

Segmental duplications of the basilar artery, previously reported exclusively as anatomical variations, owe their clinical interest to the possible association with aneurysms localized at the junctions of the fenestrated segments. The morphological characteristics of 5 cases of basilar artery segmental duplication without aneurysms, found at autopsy, are reported. In 3 of these the proximal junction of the fenestrated segment was studied with scanning electron microscopy and morphometry. In all cases the tunica media of the medial wall of the 2 branches showed a progressive thinning towards the junctions of the fenestrated segments and a small muscular gap at their apex. The limited medial defect might be embryologically ascribed to the persistence of the morphological individuality of the tunica media of the 2 branches at the point where the fusion of the primitive longitudinal neural arteries stopped. The review of the literature shows that the morphology of the junctions of the fenestrated segments is in conformity with that of the intracranial arterial bifurcations. For this reason the basilar artery fenestration exposes to the blood flow a new distal bifurcation where the same etiologic factors that are still under discussion in the origin of saccular intracranial aneurysms may be active.

[The primitive otic artery, a very rare, persistent, primitive artery (author's transl)]. / Die Arteria primitiva otica, eine sehr seltene persistierende Primitivarterie.

A very rare carotid-basilar anastomosis, the primitive otic artery, is described. In the presence of hypoplasia of the vertebral and basilar arteries and dorsal interruption of the circle of Willis, an attempt is made to explain the situation embryologically and to discuss the disadvantages associated with this condition.

Persistent primitive hypoglossal artery complicated by atrial septal defect and congenital intrahepatic shunts.

During early embryogenesis, anastomoses are formed between the carotid artery and the basilar or the vertebral artery, and subsequently, these anastomoses regress. In some cases, these anastomoses remain as persistent carotid-basilar or carotid-vertebral anastomoses. Atrial septal defect (ASD), a communication between the atria at the septal level, is a congenital heart anomaly. Intrahepatic venous shunts between the portal and hepatic veins are very rare and only some are considered congenital. We present the first case report of a patient with an ASD, a persistent primitive hypoglossal artery, and congenital portahepatic shunts.

Persistent primitive hypoglossal artery aneurysms--report of two cases.

The authors present two patients with subarachnoid hemorrhage caused by ruptured intracranial saccular aneurysms of the persistent primitive hypoglossal artery. A standard unilateral suboccipital approach in one patient resulted in incomplete neck clipping since the operative field was restricted by a protruding jugular tubercle. Successful aneurysmal neck clipping was achieved in the second patient via a unilateral-transcondylar-suboccipital approach with resection of the jugular tubercle and rim of the foramen magnum.

[Frequency of potential anastomoses in the posterior communicating branches of the circle of Willis]. / Frequência de anastomoses potenciais nos ramos comunicantes posteriores do círculo arterial do cérebro.

This neuroanatomic study has been performed to establish the frequency of potencials anastomosis in the posterior portion of the cerebral arterial circle in 87 brains from northeasterner brazilians without any aparent clinical manifestations of neural dysfunction. The fetal pattern of the posterior communicating branch was present in the 46% (40/87) of the cases. The frequency with regard to side was the following: 21,8% (19/87) on the right side; 12,8% (12/87) on the left side and 10,4% (9/87) bilateral. The bilateral and unilateral potencials anastomosis at level of the posterior communicating branches, with fetal pattern or with gross caliber (Padget, 19483), were present in the 71,2% (62/87) of the arterial circles. The bilateral potencials anastomosis were formed by two posterior communicating branches with fetal pattern in the 10,4% (9/87) of the cases, by two of those vessels of gross caliber in the 11,5% (10/87) of the circles, and by one fetal posterior communicating branch, and one contralateral posterior communicating branch of gross caliber in the 13,8% (12/87) of the cases. Unilateral potencials anastomosis constituted by fetal posterior communicating branch (21,8%) or by posterior communicating branch with gross caliber (13,8%) ocurred in the 35,6% (31/87) of the arterial circles.

Human basilar artery abnormalities in the prenatal and postnatal period.

OBJECTIVE: Although complex and varied, adult cerebral angioarchitecture has its origins in embryologic development, where normal components, variations, and abnormalities evolve from modifications of primitive vessels. Therefore, the aim of this report was the study of the morphologic features of the basilar fenestrations in prenatal and postnatal period and associated variants and/or pathologies. METHODS: We studied the brain vessels of 120 fetuses microscopically (i.e., with an operative microscope) and 112 adult cadavers macroscopically. RESULTS: We described 10 cases of basilar abnormalities, five fetal and four adult fenestrations, as well as one adult case with a basilar aneurysm. The location of the vertebrobasilar junction on a caudal myelencephalon and a prolongation of the basilar trunk followed both fetal and adult forms of fenestrations. The same caliber values of the basilar and internal carotid arteries, a variation in the number and origin of some of the basilar side branches, and a tendency of fenestrations to be multiple in number, as particular fetal features, were mostly present in adults. CONCLUSION: The fact that basilar fenestrations in adult specimens shared similar features with fetal ones and without aneurysms, as well as the fact that a basilar aneurysm was without fenestration in its base, lead us to hypothesis that the basilar fenestration is a vascular developmental variant related to the maintenance of vascular symmetry in the midline of the human brain base.

Middle meningeal artery arising from the basilar artery: report of a case and its probable embryological mechanism.

An extremely rare variation of the (left) middle meningeal artery (MMA) originating from the basilar artery, detected incidentally during cerebral angiography, is reported. The right MMA was normal and an accessory meningeal artery arising from the maxillary artery was present on both the sides. The foramen spinosum on the variant side was absent. This abnormal origin of the MMA can be explained by the presence of a perineural arterial network in the region of the Gasserian ganglion, formed by branches of the developing basilar and stapedial arterial systems; the middle meningeal-basilar arterial channel opening up in the absence of a normally developing MMA.