The anterior communicating artery variants: a meta-analysis with a proposed classification system

Morphological and morphometric variants of the anterior communicating artery (AComA) have been described by multiple studies; however, a complete classification system of all possible morphological variants with their prevalence is lacking. The current systematic review with meta-analysis combines data from different databases, concerning the AComA morphological and morphometric variants (length and diameter). Emphasis was given to the related clinical implications to highlight the clinical value of their knowledge. The typical AComA morphology occurs with a pooled prevalence (PP) of 67.3%, while the PP of atypical AComA is 32.7%. The identified AComA morphological variants (artery's hypoplasia, absence, duplication, triplication, differed shape, fenestration, and the persistence of a median artery of the corpus callosum- MACC) were classified in order of frequency. The commonest presented variants were the AComA hypoplasia (8%) and the anterior cerebral artery (ACA) fusion (5.9%), and the rarest ones were the MACC persistence (2.3%), and the AComA triplication (0.7%). The knowledge of those variants is essential, especially for neurosurgeons operating in the area. Given the high prevalence of AComA aneurysms, an adequate and complete classification of those variants is of utmost importance.

Anatomical Variations and Anomalies of the Anterior Communicating Artery Complex

BACKGROUND

Intracranial arteries have a high rate of variation, but a clear schematic overview is lacking. In this pictorial review we classify and depict all variations and anomalies within the anterior communicating artery complex.

METHODS

PubMed was searched with the terms "Anterior Communicating Artery" AND "Variations" OR "Anomalies." Articles were selected based on their description of variants. Cross-referencing was used to broaden the range of variations. Surgical view during pterional craniotomy and transsylvian approach was used as a baseline for schematic drawings of the variations.

RESULTS

A total of 42 variants were identified, schematically drawn and classified into A1-A2 segment, anterior communicating artery, and the recurrent artery of Heubner.

CONCLUSIONS

The anterior communicating artery complex consists of the anterior cerebral artery, anterior communicating artery and the recurrent artery of Heubner. An overview of these variations may be helpful in distinguishing pathology from anatomical variations, assist neurosurgeons during clipping of cerebral aneurysms, and support interventional radiologists during endovascular treatments. This article summarizes the current knowledge of anatomical variations within the anterior communicating artery complex, their prevalence and clinical relevance. A total of 42 variants were identified and schematically depicted. We encourage all who diagnose, treat, and study the anterior communicating artery complex to use this overview for a uniform and better understanding of its anatomy.

Magnetic Resonance Angiographic Study of the Anatomical Variations of the Anterior Communicating Artery Complex in a Turkish Population

AIM

To provide a definition of arterial anomalies in the anterior communicating artery complex (ACoAC), determine their prevalence and investigate their relationship with aneurysms.

MATERIAL AND METHODS

The three-dimensional time-of-flight magnetic resonance angiography images of 1,857 adult patients who presented to our hospital between January 2020 and September 2022 were evaluated retrospectively. The images of 1,537 cases were subsequently classified according to their ACoAC anatomical variants. The patients were further grouped as those with no pathology, those with ACoAC aneurysms and those with pathologies other than ACoAC, and the relationship between the ACoAC anatomical variants of each group was investigated using statistical methods. Rare variants such as trifurcations of the A2 segments, single A2 segments, fenestrations of the A1 segment and double AComAs were evaluated in separate groups.

RESULTS

The results of the classification of the 1,537 cases revealed the classical anatomical variant in 39.2% of the cases without ACoAC pathologies and 53.3% of the cases with ACoAC aneurysms. There was no significant difference between the sexes in terms of variant distribution (p=0.09), and no significant relationship between the presence of ACoAC aneurysms and sex (p=0.5).

CONCLUSION

ACoAC anatomical variants of the cerebral arterial system were detected in 60% of the cases. The most common anterior circulation (AC) vascular variants (VV) were A1 segment hypoplasia and aplasia. No clear relationship was found between intracranial aneurysms and anatomical variation.

Left anterior cerebral artery arising from a right internal carotid artery: a rare case of carotid-anterior cerebral artery anastomosis

Carotid-anterior cerebral artery anastomosis (carotid-ACA anastomosis) is described as infrequent vascular connections between the pre-ophthalmic segment of the internal carotid artery (ICA) and the A1 segment of the anterior cerebral artery (ACA). The embryological origin of these variant is still unclear and they are often associated to other vascular anomalies of the circle of Willis, as well as to the presence of aneurysms. Carotid-ACA anastomosis is often right-sided although left and bilateral cases have also been described. We report a rare case by MR angiography of a carotid-ACA anastomosis in which the abnormal vessel arises from the right ICA and takes an infraoptic course to join the A2 segment of the contralateral ACA, making this vascular anomaly function as a 'left ACA with an origin at the right ICA'. The A1 segment of the left ACA is absent and both A2 segments of the ACAs present fenestration. To our knowledge, no similar cases have been reported in English literature so far.

Fenestrated Anterior Cerebral Artery, Anterior Communicating Artery, with Accessory Middle Cerebral Artery-A Conglomeration of Embryologically Different Entities in a Single Individual

Cerebral arterial fenestrations are anatomic variants of undetermined significance where there is a division of a single vessel into at least 2 channels, each having endothelial and muscular layers, that coalesce to a single lumen in the distal course of the vessel. The basilar artery is the most common site, followed by the anterior communicating artery. The accessory middle cerebral artery is defined as the anomalous origin of the vessel from the anterior cerebral artery and its further course along the sylvian fissure parallel to the middle cerebral artery. The embryologic basis of all these has been explained by studies on human embryological development by Padget et al. However, simultaneous existence of all 3 anomalies in a single individual has never been reported. Here we present a case of medial sphenoid wing meningioma with these incidental findings during workup and further delineation of anatomy following surgical resection of meningioma.

Combined rare anatomic variants: persistent primitive olfactory artery and azygos pericallosal artery

The persisting primitive olfactory artery (PPOA) is a rare anatomic variation of the anterior cerebral artery (ACA), being encountered in less than 1% of cases. Different morphological types were reported previously. In type 3, only once reported previously, the PPOA gives off two branches, a nasal one which courses in the olfactory sulcus to supply the territory of the anterior ethmoidal artery, and the callosomarginal artery. It is reported here a combination of rare anatomic variants found in a 71-year-old male patient investigated by computed tomography angiography. A left PPOA left the A1 segment of the ACA and was classified as subtype 3b, as its branches were the nasal one and a frontal trunk, not the callosomarginal artery. That PPOA had a characteristic hairpin turn applied on the anterior fossa floor. The ACA continued as azygos pericallosal artery, which is also a rare finding. As the nasal branch of the PPOA and its hairpin turn is closely related to the anterior fossa floor, such variant should be carefully documented when combined approaches of the skull base are planned by rhinologists and neurosurgeons.

Combined Pterional Transsylvian and Bifrontal Interhemispheric Approach to Ruptured Subcallosal and Pericallosal Brain Arteriovenous Malformation with Skeletonization of the Entire A2 ACA Segment

A 39-year-old man presented with a large left paramedian frontal lobe intracerebral hemorrhage. Computed tomography angiography and magnetic resonance imaging revealed a tangle of vessels arising from the anterior cerebral arteries (ACAs) and dilated draining veins entering the superior sagittal sinus. Angiography confirmed a Spetzler-Martin grade 3, supplemented 2 arteriovenous malformation (AVM) with predominant supply from branches of the left ACA with superficial and deep drainage (Video 1). The case illustrates an unusual cerebrovascular pathology involving the entire A2 ACA segment. The AVM extended from the A1/2 junction along the entire A2 segment past the genu of the corpus callosum (A3 segment). A combined pterional transsylvian and bifrontal interhemispheric approach was performed. The proximal sylvian fissure and opticocarotid cistern were opened to expose the A1/2 junction. Once proximal control was obtained, the hematoma was evacuated to define the lateral border of the AVM. The interhemispheric fissure was then opened to identify the draining vein and the distal pericallosal arteries. The interhemispheric approach also defined the medial border of the AVM. The A2 ACAs were then skeletonized from the AVM from the A1/2 junction to the pericallosal arteries. Aneurysm clips were used to interrupt large AVM feeders from the A2 arteries, which avoids cautery and heat transmission to the parent vessel. Once the AVM was disconnected and skeletonized from the A2s, the draining vein was clipped and the nidus was removed. Indocyanine green angiography confirmed patency of the A2s and pericallosal arteries. Postoperative angiography demonstrated no residual shunting, and the patient was discharged in good condition.

Variations of the anterior communicating artery complex and occurrence of anterior communicating artery aneurysm: A2 segment consideration

INTRODUCTION

The anterior communicating artery (ACoA) is the most frequent site of intracranial aneurysm location. Despite many studies the frequency of aneurysm occurrence with anatomical anomalies is still poorly described. Moreover the significance of the A2 segment of anterior cerebral artery anomalies has been neglected. The aim of this study was to determine the frequency and types of variations of the anterior cerebral circulation in patients with ACoA aneurysms and to analyze their relation to aneurysm occurrence in the Polish population.

MATERIALS AND METHODS

We studied 50 patients with an established radiological diagnosis of ACoA aneurysm and 100 healthy age- and sex-matched controls using Computed Tomgraphy Angio- graphy. Maximum Intensity and Volume Rendering Projections were used to examine the cerebral arterial circulation. Univariate logistic regression was used to determine the statistical association between ACoA complex anomalies and aneurysm occurrence.

RESULTS

Patients in the study group had a significantly higher incidence of hypoplastic A1 seg- ment of the anterior cerebral artery (24% vs. 7%; p <0.01) and aplastic A1 segment of the anterior cerebral artery (12% vs. 3%; p = 0.03). The frequency of A1 segment hypoplasia or aplasia in the study group was 36%. There was a statistical trend regarding A2 segment aplasia/hypoplasia as a potential predictor of ACoA aneurysm (6% vs. 1%; p = 0.07).

CONCLUSION

Occurrence of an ACoA aneurysm is associated with hypoplasia or aplasia of the A1 segment of the anterior cerebral artery. A2 segment anomalies may potentially be associated with aneurysm formation.

[Microsurgical anatomy importance of A1-anterior communicating artery complex]

BACKGROUND

The anterior cerebral artery originates from the bifurcation of the internal carotid artery lateral to the optic chiasm, then joins with its contralateral counterpart via the anterior communicating artery. A1-anterior communicating artery complex is the most frequent anatomical variants and is the major site of aneurysms between 30 to 37%.

OBJECTIVE

Know the anatomy microsurgical, variants anatomical and importance of complex precommunicating segment-artery anterior communicating in surgery neurological of the pathology vascular, mainly aneurysms, in Mexican population.

METHODS

The study was performed in 30 brains injected. Microanatomy was studied (length and diameter) of A1-anterior communicating artery complex and its variants.

RESULTS

60 segments A1, the average length of left side was 11.35 mm and 11.84 mm was right. The average diameter of left was 1.67 mm and the right was 1.64 mm. The average number of perforators on the left side was 7.9 and the right side was 7.5. Anterior communicating artery was found in 29 brains of the optic chiasm, its course depended on the length of the A1 segment. The average length of the segment was 2.84 mm, the average diameter was 1.41 mm and the average number of perforators was 3.27. A1-anterior communicating artery complex variants were found in 18 (60%) and the presence of two blister-like aneurysms.

CONCLUSION

It is necessary to understand the A1-anterior communicating artery complex microanatomy of its variants to have a three-dimensional vision during aneurysm surgery.

[AICA anatomic variation as a factor of worse prognosis for the surgical treatment of hemi-facial spasm]

Hemifacial spasm is a neurovascular compression syndrome. These consist in a contacting vessel (most often an artery) to a cranial nerve in cerebelar-pontine angle. The most common is trigeminal neuralgia caused by contact between the superior cerebellar artery and the trigeminal nerve, and less commonly hemifacial spasm, vertiginous syndrome by contact of the antero inferior cerebelar artery with the eighth cranial nerve, glossopharyngeal neuralgia by contact of the postero inferior cerebelar artery and the IX cranial nerve, etc. These syndromes typically occur after the fifth decade of life, when the arterial tortuosity increases due to the arteriosclerosis process. They are however associated anatomical variations of the origin and course of the arteries, which facilitate contact with the nerves of the cerebellar-pontine angle. In hemifacial spasm, the vessel most often related is antero inferior cerebelar and the authors describe a case of a rare anatomical variant in the course of the artery that motivated the development of the disease, which was identified intraoperatively on a surgical approach to the cerebellar-pontine for vascular microdescompression.

The inter-optic course of a unique precommunicating anterior cerebral artery with aberrant origin of an ophthalmic artery: an anatomic case report

BACKGROUND AND IMPORTANCE

Some variations of the cerebral arterial circle of Willis, such as an inter-optic course of the anterior cerebral artery are exceedingly rare. Imaging of very rare anatomical features may be of interest.

CLINICAL PRESENTATION

In a 67-year-old male individual, the unique precommunicating part of the left anterior cerebral artery was found to course between both optic nerves. There was an agenesis of the right precommunicating cerebral artery. This variation was associated with an aberrant origin of the ophthalmic artery, arising from the anterior cerebral artery. The anatomic features, the possible high prevalence of associated aneurysms of the anterior communicating artery complex as well as implications for surgical planning or endovascular treatments are outlined and embryologic considerations are discussed.

CONCLUSION

To the best of our knowledge, this is a very rare illustrated case of an inter-optic course of a unique precommunicating anterior cerebral artery with aberrant origin of an ophthalmic artery.

Potent risk factor for aneurysm formation: termination aneurysms of the anterior communicating artery and detection of A1 vessel asymmetry by flow dilution

BACKGROUND AND PURPOSE

There is a high incidence of intracranial aneurysms of the AcomA suggesting the possibility of an anatomic risk factor. There also exists an association of termination-type aneurysms with anatomic variations of 1 anterior cerebral artery trunk (A1) as the exclusive or dominant supply to both pericallosal arteries (A2). This yields the hypotheses of aneurysm formation from straight jets of A1 blood.

MATERIALS AND METHODS

The anatomy and contrast filling of A1 and A2 segments and AcomAs were studied for a subset of cases entered into the Cerecyte Coil Trial for patients with AcomA (n = 105) and other aneurysms (n = 123) that were selected from imaging available at the Cerecyte Core Trial angiographic Core Lab. These cases were analyzed for A1 vessel dominance by measurement of the vessel diameter and dilution of angiographic contrast agent in A2s due to the differential flow source on selective angiography. A control group without aneurysms was assessed anatomically, using a large sequential CTA series (n = 159), acquired during acute stroke assessment.

RESULTS

A1 dominance configuration is strongly associated with the presence of AcomA aneurysms for patients with intracranial aneurysms (odds ratio, 17.8). This association is also present compared with the incidence of A1 dominance in the large sequential control series of patients without aneurysms undergoing CTA for other reasons (odds ratio, 7.5). Outflow dilution of selective angiographic images augments anatomic information.

CONCLUSIONS

A flow-based assessment of contrast flowing from the A1 to the A2 segments after injection pressure is superior to an A1 diameter based categorization when A1 vessel diameters are not strikingly different. The anatomic variant of asymmetric A1 configurations likely facilitates the development of AcomA aneurysms by flow stresses, providing further evidence to support the role of biophysical factors in intracranial aneurysm development.

Morphometry of A1 segment of the anterior cerebral artery and its clinical importance

BACKGROUND AND AIM

Anterior cerebral artery, one of the terminal branches of the internal carotid artery is an important vessel taking part in the formation of circle of Willis. It supplies a large part of the medial surface of the cerebral hemisphere containing the areas of motor and somatosensory cortices of the lower limb. Aim of this study was the morphometry of A1 segment of the anterior cerebral artery.

MATERIALS AND METHODS

93 formalin fixed brain specimen of either sex and of Indian origin were studied. The mean length, mean external diameter and the anomalies present in A1 segment of the vessel were studied in detail and photographed.

RESULTS

The mean length of A1 segment of the vessel was 14.49+/-0.28 mm and 14.22+/-0.22 mm on right and left side respectively. The mean external diameter of the vessel on right and left side was 2.12+/-0.07 mm and 2.32+/-0.06 mm respectively. Narrowing, aneurysm formation, buttonhole formation and median anterior cerebral artery were the anomalies seen with an occurrence of 15.05%, 5.37%, 3.22% and 12.9%, respectively. The above anomalies did not have any sex or side predilection.

CONCLUSION

Knowledge of morphometry of the vessel will be of use to neurosurgeons while performing the shunt operation, in assessing the feasibility of such operations and in the choice of patients. From this study we infer that the morphometry of anterior cerebral artery varies in different population and that the neurosurgeons operating should have a thorough knowledge of the possible variations.

Fenestration of the anterior cerebral artery detected by magnetic resonance angiography

BACKGROUND

Fenestration of the proximal anterior cerebral artery (ACA) A1 segment is a rare anatomic variation. The purpose of the this study was to report the incidence of fenestration in the proximal segment of the anterior cerebral artery and to delineate its configurations on cranial MR angiography.

METHODS

Magnetic resonance angiography (MRA) was performed in 762 patients using 1.5 T imagers during the period July 2007 through September 2008. All images were obtained by the three-dimensional time-of-flight (3D TOF) technique. Volume rendering (VR) images in the horizontal rotation view were displayed stereoscopically. The presence of fenestration in the proximal segment of the anterior cerebral artery was identified and evaluated retrospectively by MRA.

RESULTS

Six patients (four men and two women, 15 to 63 years of age, median age 50 years) had proximal ACA fenestration. The appearance rate of ACA fenestration was 0.8% (6/762). All 6 fenestrations were located at the A1 segment: three of them were with a slit-like shape and three were with a convex-lens-like shape, 5 of the right A1 segment, 1 of the left A1 segment.

CONCLUSION

Recognizing ACA fenestration is important to interpret cranial MR angiographys and helpful to make a plan for neurosurgical procedures or neurological intervention.

Aberrant internal carotid artery in the middle ear with a deficiency in the origin of the anterior cerebral artery: a case report

An aberrant internal carotid artery (ICA) in the middle ear is rare and difficult to diagnose, and may lead to severe complications. We present here a case of aberrant ICA with a deficiency in the origin of the anterior cerebral artery. The only symptom was aural fullness, and a nonpulsatile and white tympanic mass in the anteroinferior area was noted. Computed tomography (CT) and magnetic resonance angiography (MRA) are useful tools that provide excellent visualization of the temporal bone for the diagnosis of aberrant ICA by the following features: intratympanic mass, enlarged inferior tympanic canaliculus, absence of the vertical segment of the ICA canal, and absence of bone covering the tympanic portion of the ICA. In addition, in this case, a deficiency in the origin of the anterior cerebral artery on the same side was identified by MRA, and cerebral arteriography and a carotid occlusion test were performed. Because of the deficiency in the origin of the anterior cerebral artery, the ICA compression revealed that there was almost no cross flow from the other ICA. Our experience illustrates that after confirmation of the diagnosis of aberrant ICA, localized treatment and/or surgical procedures should be considered carefully.

Infraoptic anterior cerebral artery: review, report of two cases and an anatomical classification

INTRODUCTION

Infraoptic course of the pre-communicating anterior cerebral artery (A1) is a rare anomaly. In total, there are 42 examples reported in the literature. We report two further patients. The first had an intradural cerebral aneurysm at the low bifurcation of an internal carotid artery (ICA) with bilateral infraoptic course of A1. The second had right infraoptic course of A1 with associated left parietal cerebral arteriovenous malformation and is the first report of such an association.

DISCUSSION AND CONCLUSION

Overall, 59% of the examples were associated with cerebral aneurysms. Different terminology such as carotid-anterior cerebral artery anastomosis and infraoptic anterior cerebral artery has been used. Having analyzed the reports of infraoptic A1, we found the vascular configurations of the A1 could be better described by classifying them into four types. Such a classification can facilitate analysis of the embryogenesis explanation for this anomaly and the pathogenesis of the associated aneurysms. Besides, such a classification also has some practical implications.

Agenesis of the left internal carotid artery associated with anterior communicating artery aneurysm: case report

We present a rare case of agenesis of the left internal carotid artery in a 43-year old woman, associated with an aneurysm of the anterior communicating artery and presenting with subarachnoid hemorrhage. The left internal carotid artery was not visualized on the left carotid angiogram. The left middle cerebral artery was perfused from the basilar artery via the dilated posterior communicating artery on vertebral angiogram. Absence of the left carotid canal was proven on temporal bone computed tomography. Absence of the left internal carotid artery was verified at operation. Absence of internal carotid artery is discussed in relation to aneurysm formation.

Infraoptic course of anterior cerebral arteries associated with abnormal gyral segmentation

✓ The authors report the case of a 34-year-old woman who presented with increasing headaches. Neuroimaging revealed bilateral anomalous vessels arising at the level of each ophthalmic artery, coursing rostromedially to join the anterior communicating artery (ACA), which harbored an aneurysm. Intraoperatively, the authors identified an abnormal gyral segmentation of the frontoorbital region, with a median gyrus separated from the olfactory tracts on each side by the gyrus rectus. No interhemispheric fissure was observed in the exposed area. This is the first report in the literature of an abnormal gyral segmentation in association with an infraoptic course of an ACA. Recognition of this possible gyral abnormality in association with this vascular anomaly is relevant for surgical exposure and treatment of aneurysms by clip placement.

Some variations of the circle of Willis, important for cerebral protection in aortic surgery — a study in Eastern Europeans

BACKGROUND

During unilateral selective cerebral perfusion (SCP), via cannulation of the brachiocephalic trunk, the brain receives blood only through the right common carotid artery and the right vertebral artery. For perfusion of the contralateral (left) hemisphere it is counted on the competence of the circle of Willis (CoW). It is well known that variations of CoW are present in more than 50% of the people. Furthermore, these variations usually affect more than one vessel of the circle. The aim of the present work was to study the variations of CoW, which could have an impact on cerebral blood supply during unilateral SCP.

METHODS AND MATERIALS

We study 112 CoWs obtained from cadavers via routine dissection in the Department of Forensic Medicine of Medical University, Sofia. The external diameter of both vertebral arteries and all arteries that form CoW was measured with a caliper-gauge.

RESULTS

We identify the variations of CoW such as significant hypoplasy and/or lack of a branch of the circle. Bearing in mind the characteristics of the blood flow during unilateral SCP some of these variations were classified as significant during unilateral SCP. They were subdivided into groups according to most probable stroke site after unilateral SCP.

CONCLUSIONS

Because of the high percent of the variations, hemodynamically significant during unilateral SCP, a suggestion for routine preoperative CT-angio of CoW could be made. Furthermore, an intraoperative follow-up with NIRO, transcranial Doppler, EEG, and so forth could also be recommended.

Anterior Cerebral Artery A1 Segment Hypoplasia May Contribute to A1 Hypoplasia Syndrome

Anterior cerebral artery A1 segment hypoplasia is an uncommon fetal variant of the circle of Willis. The frequency of this congenital variation is 1-13% as derived from angiograms and autopsy reports. Impaired collateral blood flow through the circle of Willis is a recognized risk factor for ischemic stroke. The A1 segment of the anterior cerebral artery is a principal supplier of anterior collateral blood flow. The aim of our study was to determine whether A1 segment hypoplasia may be responsible for acute ischemic stroke. We consecutively examined 280 acute ischemic stroke patients (aged 66.9 +/- 14.2 years). Cerebral magnetic resonance angiography was performed within 72 h of ischemic stroke onset. The overall incidence of A1 variation in our experimental group was 15.0% (n = 42, agenesis/hypoplasia = 18/24), which was statistically higher than in the control group (n = 12). The majority (n = 30, 71.42%) had ipsilateral striatal lacunar infarctions. Based on our results, A1 agenesis/hypoplasia appears to be a risk factor contributing to ischemic stroke, especially to strokes in arteries penetrating the striatal area.

Anomalous origin of the callosomarginal artery from the A1 segment with an associated saccular aneurysm

Although anatomic variations are well known in the A1 segment of the anterior cerebral artery (ACA), anomalous origin of a cortical artery from the A1 segment is extremely rare. The only reported cortical branch to arise from the A1 segment is the fronto-orbital artery. We report a case of anomalous origin of the callosomarginal artery (CMA) in association with a saccular aneurysm from the A1 segment of the left ACA in a 35-year-old man who presented with intracerebral hemorrhage. To our knowledge, this is the first report of anomalous origin of the CMA from the A1 segment.

Anterior cerebral artery variations detected by MR angiography

INTRODUCTION

From anatomical and angiographic studies, it is well known that there are several variations of the anterior cerebral artery (ACA). However, ACA variations have rarely been studied by magnetic resonance (MR) angiography. The purpose of this study was to investigate not only the type, location, configuration, and incidence of ACA variations, but also coexisting arterial pathology such as aneurysms detected by cranial MR angiography.

METHODS

We retrospectively reviewed cranial MR angiography images of 891 patients at our institution. All images were obtained with one of two 1.5-T scanners using the three-dimensional time-of-flight technique. Maximum intensity projection (MIP) images in the horizontal rotation view were displayed stereoscopically. We reviewed these horizontal MIP images, inferosuperior MIP images, and source images, and identified variations of the ACA.

RESULTS

We found 50 instances (5.6%) of unilateral A1 segment aplasia, 27 (3.0%) of three A2 segments, 18 (2.0%) of an unpaired A2 segment, and 11 (1.2%) fenestrations of the A1 and/or A2 segment. Seven anterior communicating artery (ACoA) aneurysms and one ACA territory embolic infarction were found among the 50 patients with unilateral A1 segment aplasia. One ACoA aneurysm and one pericallosal infarction were found in the 27 patients with three A2 segments. Two distal ACA aneurysms were detected among the 18 patients with an unpaired A2 segment. No associated aneurysm was seen at the fenestrations.

CONCLUSION

Although the clinical significance of ACA variations is usually minor, an associated aneurysm is found relatively frequently. Thus, recognizing ACA variations during the interpretation of cranial MR angiograms is important.

Gomez-Lopez-Hernandez syndrome

We describe a case of Gomez-Lopez-Hernandez syndrome in an 18-month-old boy. Imaging findings included rhombencephalosynapsis with a single dentate nucleus. In addition, MR angiography revealed an azygous anterior cerebral artery. The clinical presentation, MRI findings and pathogenesis are discussed.

Ruptured fusiform aneurysm of fenestrated A1 segment of the anterior cerebral artery

We present a case report of a 56-year-old woman with a ruptured fusiform aneurysm of a fenestrated A(1) segment of the anterior cerebral artery (ACA). Fenestrated A(1) segments are rare and only a few case reports have been published of a saccular type aneurysm formation. To the best of our knowledge, there have been no documented cases of fusiform aneurysms in these segments.

[Two cases of distal anterior cerebral artery aneurysm associated with accessory anterior cerebral artery]

An accessory anterior cerebral artery (accessory ACA) is a rare anomalous vessel arising from the anterior communicating artery as a median artery of triplicated ACA. It is considered a large median artery of the corpus callosum and distributes to one or both hemispheres. The cases of an accessory ACA aneurysm are extremely rare; however, we experienced two cases of unruptured aneurysm growing at the distal portion of an accessory ACA. Two females, aged 66 and 67 years, respectively, separately consulted our hospital as a result of chronic headaches. Brain MR angiography and following DSA in the first patient demonstrated a triplicated ACA and an aneurysm located just above the corpus callosum growing from the distal portion of the accessory ACA. MRI and MR angiography in the second patient depicted a triplicated ACA and an aneurysm from the accessory ACA as with the first case. Neck clipping of the aneurysm was performed using an interhemispheric approach in both cases. These aneurysms appeared to present the same intraoperative findings as other unruptured aneurysms growing at the usual positions.

Fetal azygos pericallosal artery

An unpaired trunk forming part of the anterior cerebral arteries, the so-called azygos pericallosal artery, was found in a male fetus among a collection of 200 fetuses. The morphological characteristics of the trunk and the anterior cerebral arteries at the "preazygos" and the "postazygos" segments were examined using an operating microscope. The azygos pericallosal artery distributes into three postazygos segments of which only the median postazygos segment or median callosal artery had a bihemispheric distribution of its branches to the medial telencephalic surfaces.

Anomalous internal carotid anastomosis to contralateral anterior cerebral artery

BACKGROUND

Many anomalies and variants in vascular anatomy have been reported in relation to the anterior cerebral artery (ACA).

PATIENTS AND METHODS

We encountered an apparently novel anomaly in a 30-year-old man admitted for disturbance of consciousness following a traffic accident. Computed tomography revealed an acute subdural hematoma and subarachnoid hemorrhage.

RESULTS AND CONCLUSIONS

No vascular abnormalities related to the hemorrhage were detected by conventional angiography, so we concluded that the bleeding was of traumatic origin. Anomalous origin of the ACA was disclosed incidentally, with both A1 segments arising from the right internal carotid artery; no normal A1 segment of the left ACA was visualized. We discuss possible bases for this anomalous origin.

Unique anomalous origin of the left anterior cerebral artery

We present the case of an anomalous origin of the left anterior cerebral artery (ACA) from the supraclinoid segment of the right internal carotid artery. Because of improved imaging quality, anomalies of the ACA-anterior communicating artery (AComA) complex are increasingly recognized on transaxial images. Although most of these anomalies are incidental findings of little clinical significance, some ACA-AComA complex anomalies are clinically significant. Recognition of these anomalies may be instrumental in developing a differential diagnosis or for improved surgical planning.

Normal variants of the intracranial circulation demonstrated by MR angiography at 3T

Magnetic resonance angiography (MRA) at 3T offers increased signal to noise ratio with better background suppression, leading to exquisite depiction of the intracranial circulation. We present a pictorial review of the normal variations and anomalies of the intracranial circulation detected on MRA performed on a high field 3T clinical scanner using parallel imaging techniques. The salient imaging features of these anomalies and normal variations are discussed with relevance to clinical practice.

[Ruptured aneurysm of bihemispheric anterior cerebral artery bifurcation: case report]

It is well known that distal anterior cerebral artery (ACA) aneurysms are often associated with the anomalies of the ACA, of which azygos ACA and triple ACA have frequently been described. In this report, we present a rare case with a ruptured aneurysm arising from the bifurcation of the bihemispheric ACA, a rare anomaly of the ACA. A 63-year-old male suddenly developed severe headache, consciousness disturbance, and left hemiparesis, and was admitted to our hospital. Plain CT scans revealed subarachnoid clots that were densely distributed in the supracallosal cistern. Cerebral angiography demonstrated that the left pericallosal artery supplied blood flow to the bilateral parietal lobes through the bihemispheric arteries. A saccular aneurysm was found at their bifurcation. He underwent clipping surgery through interhemispheric approach. Postoperative course was uneventful. Special care should be taken not to occlude the bihemispheric arteries supplying to the bilateral parietal lobes during surgery.

Unusual Variant of the Anterior Cerebral Artery-Case Report-

A rare abnormality of the A1 segment of the anterior cerebral artery (ACA) is reported. The right ACA bifurcated into two parts at the middle point of the A1 segment, and these segments did not rejoin. The superior right A1 segment connected with the left A1 and formed a single pericallosal artery. The inferior right A1, from which the right ophthalmic artery originated, had no connection with the left A1.

Bilateral anterior cerebral artery territory infarction associated with unilateral hypoplasia of the A1 segment: report of two cases

We report two cases of bilateral anterior cerebral artery (ACA) territory infarction. On magnetic resonance (MR) angiograms, the A1 segment of the ACA was unilaterally hypoplastic in both cases, suggesting that unilateral hypoplasia of A1 is a significant predisposing factor for this rare type of cerebral infarction. When the contralateral A1 is dominant, embolic materials may enter into it more easily.

Ruptured cerebral aneurysm in the early stage of life--a congenital origin?

We report the case of a large fusiform aneurysm of the anterior cerebral artery in a 3-month-old girl presenting with generalized seizures and complicated by a cardiorespiratory arrest needing resuscitation. The native cerebral CT scan revealed a diffuse subarachnoid hemorrhage (Fischer III grade); CT angiography showed an aneurysm of the distal A1 segment of the anterior cerebral artery (ACA). Successful treatment was achieved through surgical trapping of the aneurysm and sacrifice of the distal A1 segment. A histological study of the aneurysmal wall revealed the absence of elastic fibers in an otherwise fibromuscular media and showed no signs of previous hemorrhage. Intracranial aneurysms of the ACA are very rare in the early stage of life and their pathogenesis is not clear. This case is of interest as the location and shape of the aneurysm, the absence of relevant familial and medical history, and the histopathological findings raise the hypothesis of a congenital origin. It further describes the value of CT angiography for studying aneurysms in the very young.

Lysosome abnormalities and lipofucsin content of nerve cells of oedematous human cerebral cortex

Lysosome alterations and lipofucsin content of nerve cells, capillary endothelial cells and pericytes were examined in the anoxic-ischaemic brain parenchyma of thirty two patients with congenital hydrocephalus, complicated brain traumatic injuries, brain tumours and vascular anomalies. Cortical biopsies of frontal, parietal and temporal cortex were processed for transmission electron microscopy. In oedematous non pyramidal and pyramidal nerve cells, lysosomes showed fragmentation of their limiting membranes and an associated dense granulation. Areas of cytoplasmic focal necrosis were observed surrounding the lysosomes. Lipofucsin granules were also observed in neonate and infant patients with congenital hydrocephalus, suggesting that lipofucsin formation is a life span process. Lysosomes coexisting with an increased amount of lipofucsin granules were observed in young and adult patients with brain trauma, tumours and vascular anomalies. Phagocytic astrocytes and activated oligodendroglial cells showed the overall spectrum of an altered endosomal/lysosomal system. Lipofucsin granules and multivesicular bodies also were distinguished in endothelial and pericyte cells. The role of released and activated lysosomal enzymes is discussed in relation with the cytoplasmatic focal necrosis of nerve cells and the genesis of moderate and severe oedema.

Nerve cell nuclear and nucleolar abnormalities in the human oedematous cerebral cortex. An electron microscopic study using cortical biopsies

Cerebral cortical biopsies of 17 patients with clinical diagnosis of congenital hydrocephalus, complicated brain trauma, cerebellar syndrome and vascular anomaly were examined with the transmission electron microscope to study the nuclear and nucleolar abnormalities induced by moderate and severe brain oedema, and the associated anoxic-ischemic conditions of brain tissue. In infant patients with congenital hydrocephalus and Arnold-Chiari malformation two different structural patterns of immature chromatin organization were found: the clear type characterized by a clear granular and fibrillar structure of euchromatin, scarce heterochromatin masses and few perichromatin granules, and a dense granular and fibrillar euchromatin with abundant and scattered heterochromatin masses, and increased number of perichromatin granules. The lobulated nuclei exhibited an irregularly dilated and fragmented perinuclear cistern, and areas of apparently intact nuclear pore complexes alternating with regions of nuclear pore complex disassembly. In moderate traumatic brain injuries some nucleoli exhibit apparent intact nucleolar substructures, and in severe brain oedema some nucleoli appeared shrunken and irregularly outlined with one or two fibrillar centers, and others were disintegrated. The nuclear and nucleolar morphological alterations are discussed in relation with oxidative stress, peroxidative damage, hemoglobin-induced cytotoxicity, calcium overload, glutamate excitotoxicity, and caspase activation.

Microsurgically critical anomaly of the anterior communicating artery complex during the pterional approach to a ruptured aneurysm: double fenestration of the proximal A2 segments

A 50-year-old man presented with a ruptured aneurysm of the anterior communicating artery (ACoA) complex anomaly with the neck of the aneurysm located in the upper ACoA. The right pterional approach was performed 2 days after admission. Retraction of the frontal lobe exposed the lower half of the ACoA complex consisting of the origins of the bilateral A2 segments, and the apparent neck of the aneurysm was clipped. However, further exposure of the bilateral A2 segments revealed double fenestration of the proximal A2 segments, a subtype of duplication of the ACoA accompanied by a bridging artery between the upper and lower ACoA. The limited visualization of this ACoA complex anomaly with an aneurysm had led to the proximal origin of the bridging artery being mistaken for the neck of the aneurysm. Such double fenestration of the proximal A2 segments is a microsurgically critical anomaly of the ACoA complex, because the bridging artery mimics the neck of an aneurysm when visualized by the pterional approach.

Persistent stapedial artery: MR angiographic and CT findings

A 2-year-old girl was found to have a pink pulsatile mass behind the right tympanic membrane on physical examination. We report the high-resolution CT and MR angiographic findings of persistent stapedial artery with hypoplasia of the A1 segment of the right anterior cerebral artery.

Coil embolization of an aneurysm associated with an infraoptic anterior cerebral artery in a child

We report an unusual case of a ruptured aneurysm from an infraoptic anterior cerebral artery in an 11-year-old child. To our knowledge, this is the second such case treated with Guglielmi detachable coils in the pediatric population that has been described in the literature, excluding that of a vein of Galen aneurysm that resulted in remarkable recovery. We conclude that the endovascular technique is a feasible treatment option for children with ruptured cerebral aneurysms, especially when more complex vascular anomalies are present.

Absence of the common carotid artery: a rare vascular anomaly

Although absence of the common carotid artery (CCA) is a rare anomaly, the specific configuration in our case makes it extremely rare. Clinical, angiographic, ultrasonographic, and embryologic correlations of this anomaly are discussed after the case report.

Fenestrated anterior cerebral artery

Two rare cases of fenestrated anterior cerebral artery associated with aneurysms are described. The importance of identifying this unusual anatomical anomaly and its implication during surgery is discussed.

Recognition and importance of an infraoptic anterior cerebral artery: case report

Although variations of the anterior cerebral artery (ACA)-anterior communicating artery complex are commonly identified on imaging studies, an infraoptic course of the ACA is exceedingly rare. What is believed to be the first case of an infraoptic course of the ACA discovered with MR angiography and further characterized with conventional angiography is presented. The high prevalence of associated aneurysms and the implications for surgical planning make preoperative recognition of this anomaly critical.