Anatomical evaluation of P1 segment of posterior cerebral artery and posterior communicanting artery in 340 human hemispheres: a proposal for morphological classification.

PURPOSE: The aim of our study is to examine the morphometry of the P1 segment of the posterior cerebral artery (P1) and the posterior communicating artery (PcomA) and to present a descriptive classification according to morphometric findings. METHODS: 340 hemispheres from 170 cadavers were included. The outer diameters of P1 and PcomA were measured with ImageJ software. Then, the configurations of the posterior cerebral artery were revealed as fetal, adult and transitional. The findings were correlated with the demographic information of the cadavers such as gender, body mass index (BMI), age. RESULTS: According to the morphometric findings, 83.75%, 13.85% and 2.40% of the posterior cerebral arteries were found to be adult, fetal and transitional, respectively. The fetal type was more common in cadavers aged 60 years and older (13.73%) compared to the 18-39 and 40-59 age groups. In addition, P1 and PcomA diameters also increased with age. Fetal and transtional types showed a similar low distribution in people with low (< 18.5), normal (18.5-24.9), overweight (25-29.9) and obese (> 30) BMI, whereas adult type was found in cadavers with a normal BMI of 140/303. CONCLUSION: We believe that the findings of our study will contribute to the planning of neurointerventional procedures, the development of endovascular devices, the success of invasive procedures and the reduction of complications.

Anatomical Features of Posterior Cerebral Arteries and Basilar Artery in 170 Anatolian Fresh Cadavers: Implications for Surgical Planning and Intervention.

BACKGROUND: The posterior cerebral arteries (PCAs) are terminal branches of the basilar artery (BA) and are responsible for the primary supply of the occipital lobe. Saccular aneurysm is most commonly seen close to the bifurcation of the BA. Various surgical interventions are performed for aneurysms. Therefore, the anatomy and localization of the BA and PCA are crucial. The aim of this study was to determine the characteristics of these arteries in a large Anatolian population. METHODS: The study included 170 Anatolian fresh cadavers. The diameters of the BA and PCA were measured. Correlations according to sex and age groups were analyzed. The Q1, Q2, and Q3 angles between the right and left PCA, between the right PCA and BA, and between the left PCA and BA, respectively, were measured. The location of the PCA relative to the sulcus pontocruralis (pontocrural groove) was also evaluated. RESULTS: The diameter of the artery increased with age and was higher in males than in females. Q1 and Q2 diameters were larger in males, while the Q3 diameter was larger in females. The Q1 angle between the right and left PCAs was found to be higher in age range 40-59 years with a mean of 87.33 ± 17.91 mm. Finally, the bifurcation point of the PCA was most frequently located above the sulcus pontocruralis (pontocrural groove) and least frequently located on the sulcus pontocruralis (pontocrural groove). CONCLUSIONS: The findings of our study will contribute to the planning of surgical approaches, the development of endovascular devices, the success of invasive procedures, and the reduction of complications.

Association of brain arterial diameters with demographic and anatomical factors in a multi-national pooled analysis of cohort studies.

BACKGROUND AND PURPOSE: Brain arterial diameters are markers of cerebrovascular disease. Demographic and anatomical factors may influence arterial diameters. We hypothesize that age, sex, height, total cranial volume (TCV), and persistent fetal posterior cerebral artery (fPCA) correlate with brain arterial diameters across populations. METHODS: Participants had a time-of-flight MRA from nine international cohorts. Arterial diameters of the cavernous internal carotid arteries (ICA), middle cerebral arteries (MCA), and basilar artery (BA) were measured using LAVA software. Regression models assessed the association between exposures and brain arterial diameters. RESULTS: We included 6,518 participants (mean age: 70 ± 9 years; 41% men). Unilateral fPCA was present in 13.2% and bilateral in 3.2%. Larger ICA, MCA, and BA diameters correlated with older age (Weighted average [WA] per 10 years: 0.18 mm, 0.11 mm, and 0.12 mm), male sex (WA: 0.24 mm, 0.13 mm, and 0.21 mm), and TCV (WA: for one TCV standard deviation: 0.24 mm, 0.29 mm, and 0.18 mm). Unilateral and bilateral fPCAs showed a positive correlation with ICA diameters (WA: 0.39 mm and 0.73 mm) and negative correlation with BA diameters (WA: -0.88 mm and -1.73 mm). Regression models including age, sex, TCV, and fPCA explained on average 15%, 13%, and 25% of the ICA, MCA, and BA diameter interindividual variation, respectively. Using height instead of TCV as a surrogate of head size decreased the R-squared by 3% on average. CONCLUSION: Brain arterial diameters correlated with age, sex, TCV, and fPCA. These factors should be considered when defining abnormal diameter cutoffs across populations.

The Posterior Inferior Cerebellar Artery (PICA): An Anatomical and Clinical Analysis.

AIM: To study the operative approaches for posterior inferior cerebellar artery (PICA) aneurysms or understanding the different pathologies that can affect this artery, and to present detailed knowledge of this artery?s anatomy. MATERIAL AND METHODS: The present study analyzed the different variations of the PICA?s first two segments, the anterior medullary and lateral medullary segments, regarding the number of trunks, their emergency site, and the presence or absence of hypoplasia of this artery, through microsurgical dissection of 23 fresh cadaver brains. RESULTS: Some striking variations were found, such as the absence of the left vertebral artery in one of the brains and the emergence of any PICA in another two brains studied. Moreover, variations such as hypoplastic arteries, missing trunks on one side and double or triple trunks, different emergence sites, significant PICA emergence from the superior part of the vertebral artery (59% of the trunks), and asymmetries between the right and left sides were recorded. The double origins of non-hypoplastic PICAs were found in 17% (n = 4) of patients. CONCLUSION: The results obtained in the present study indicated the great importance of the studies and reviews on the different topographies of PICA; these studies and reviews expand the knowledge and consensus on the characteristics and implications of PICA?s variations. The clinical implication of this knowledge and consensus is obtaining the best surgical strategies for clipping aneurysms and, in addition, the best choices for occlusion of the vessel affected if the territory of the main vessel has an adequate collateral circulation. From the results of the present study, it is evident that there was a significant PICA emergence from the superior part of the vertebral artery and that the double origin of non-hypoplastic trunks was also found in some patients; the latter is associated with a greater chance of aneurysms and other additional complications.

Delayed mesencephalic venous infarction after endovascular treatment of a giant aneurysm of the posterior cerebral artery: Case report and anatomical review.

A 54-year old male patient underwent stent reconstruction of the P1-2 segment of the left posterior cerebral artery (PCA) and concomitant coil embolization of a symptomatic giant partially thrombosed P1 segment aneurysm. After an uneventful postinterventional period, on the 7th day the patient developed severe disturbance of consciousness. The imaging workup demonstrated acute venous infarction in the midbrain, caused by the compressive occlusion of the median anterior pontomesncephalic vein by the aneurysm in the interpeduncular fossa.

Arterial Supply of the Thalamus: A Comprehensive Review.

The thalamus is a deep cerebral structure that is crucial for proper neurological functioning as it transmits signals from nearly all pathways in the body. Insult to the thalamus can, therefore, result in complex syndromes involving sensation, cognition, executive function, fine motor control, emotion, and arousal, to name a few. Specific territories in the thalamus that are supplied by deep cerebral arteries have been shown to correlate with clinical symptoms. The aim of this review is to enhance our understanding of the arterial anatomy of the thalamus and the complications that can arise from lesions to it by considering the functions of known thalamic nuclei supplied by each vascular territory.

Morphological and clinical risk factors for the rupture of posterior communicating artery aneurysms: significance of fetal-type posterior cerebral artery.

BACKGROUND: Posterior communicating artery (PcomA) aneurysm can be classified into sidewall or bifurcation types based on the anatomical variation of fetal-type posterior cerebral artery (fPCA). The aims of this study were to investigate the significance of fPCA as an independent risk factor for the rupture of PcomA aneurysm and to evaluate other associated morphological and clinical risk factors. METHODS: We retrospectively reviewed clinical and radiological findings of 255 patients with PcomA aneurysms, which were treated in a single tertiary institute between January 2009 and December 2016. Univariate and multivariate analyses were performed to evaluate the associations between morphological and clinical variables and rupture status. Subgroup analysis was also performed based on the aneurysms with and without fPCA. RESULTS: Fifty-five out of 255 PcomA aneurysms (21.6%) were associated with fPCA. Multivariate logistic regression analysis showed that the superior direction of aneurysm dome (OR 9.106, p = 0.007), the presence of a bleb (OR 4.780, p < 0.001), a high aspect ratio (OR 1.878, p = 0.045), and fPCA (2.101, p = 0.040) were significantly associated with PcomA aneurysm rupture. In the fPCA group, only the presence of a bleb varied significantly between ruptured and unruptured PcomA aneurysms. However, in the non-fPCA group, larger aneurysms, the superior direction of dome, the presence of a bleb, and a high aspect and dome-to-neck ratio were significantly higher in the ruptured aneurysm group than in the unruptured aneurysm group. CONCLUSIONS: The results demonstrate that fPCA may be an independent risk factor for rupture, especially together with the presence of a bleb.

The Parieto-Occipital Artery Revisited: A Microsurgical Anatomic Study.

BACKGROUND: The parieto-occipital artery (PoA) is the terminal posterior cerebral artery branch, which typically runs in the parieto-occipital sulcus. Previous studies have highlighted variation in the PoA origin and branching pattern and their clinical implications. Nevertheless, PoA anastomoses have not been systematically investigated. The present study aimed to assess whether putative variation in PoA origin and its branching as well as anastomotic pattern is associated with differences in demographic/anthropometric variables. METHODS: In 15 cadaveric heads, PoA anatomic features were quantified and assessed in relation to demographic/anthropometric variables. RESULTS: The mean distance of PoA origin from the posterior limit of the splenium and the occipital pole (OP) is 3.1 and 53.1 mm, respectively. The latter is significantly longer in taller individuals. The PoA supplies a mean of 10.5 and 9.1 branches to the precuneus and cuneus, respectively. PoA anastomoses primarily involve the precuneal artery complex (PAc) and the calcarine artery. The analysis indicated significant, positive correlations between the distance of PoA origin from the OP and the number of PoA anastomoses and between the number of PoA precuneal and cuneal branches. CONCLUSIONS: Although the PoA invariably supplies the precuneus and almost always the cuneus, its direct contribution to the former seems inferior to PAc. Nevertheless, the PoA frequently shows putative collateral supply networks to the precuneus and cuneus via anastomoses with the PAc and calcarine artery, respectively. The distance between PoA origin and OP varies with an individual's height; the frequency of intrahemispheric PoA anastomoses varies with its site of origin.

The segmentation of the posterior cerebral artery: a microsurgical anatomic study.

There are still different descriptions of the segmentation of the posterior cerebral artery, although there is a radiological and anatomical consensus on the segmentation of the anterior and the middle cerebral artery. This study aims to define the most appropriate localization for origin and end points of the segments through reviewing the segmentation of the posterior cerebral artery. The segments and the cortical branches originating from those segments of the 40 posterior cerebral arteries of 20 cadaver brains were examined under operating microscope. In this research, the P1, P2, P3, P4, and P5 classification of the segmentation of the posterior cerebral artery is redefined. This redefinition was made to overcome the complexities of previous definitions. The P1 segment in this research takes its origin from the basilar tip and ends at the junction with the posterior communicating artery. The average diameter of this segment at the origin was 2.21 mm (0.9-3.3), and the average length was 6.8 mm (3-12). The P2 segment extends from the junction with the posterior communicating artery to the origin of the lateral temporal trunk. This point usually situates on one level of posterior of the cerebral peduncle. The average diameter of this segment at the origin was 2.32 mm (1.3-3.1), and the average length was 20.1 mm (11-26). The P3 segment extends from the origin of the lateral temporal trunk to the colliculus where both the posterior cerebral arteries are the nearest to each other (quadrigeminal point) and is located at the anterior-inferior of the splenium. The average diameter of this segment at the origin was 1.85 mm (1.2-2.7), and the average length was 16.39 mm (9-28). The P4 begins at the quadrigeminal point and ends at the top of the cuneus. The average diameter of this segment at the origin was 1.55 mm (1.1-2.2). While the P5 segment is named as the terminal branches of the major terminal branches of the posterior cerebral artery, no definite border was found between the P4 and the P5 segments. In this study, the segmentation of the posterior cerebral artery, developed by Krayenbühl and Yasargil, was redefined to be more appropriate for radiological and anatomical purposes.

Morphological Characteristics of the Posterior Cerebral Circulation: An Analysis Based on Non-Invasive Imaging.

AIM: To provide measurements of the posterior cerebral circulation using a non-invasive imaging modality. MATERIAL AND METHODS: One-hundred and twenty patients aged from 12 to 76 years were analyzed using computed tomography (CT) angiography. Measurements of vertebral arteries (VA), basilar artery, posterior cerebral arteries (PCA) and posterior communicating arteries were obtained. Basilar artery appearance and curvature were also noted. Differences between sides, genders and age groups were evaluated. RESULTS: Mean diameter of left VA was 2.36±0.81 mm, and mean diameter of right VA was 2.14 ± 0.79 mm. Mean length of basilar artery was 34.07 ± 5.53 mm in males, and 30.79 ± 4.18 mm in females. There was a significant difference in basilar artery length between genders: males had a longer basilar artery (p < 0.01). There was significant difference in basilar artery diameters between patients younger and older than 60 years: older patients had a statistically larger diameter, 3.17 ± 0.76 mm, than the 2.87 ± 0.57 mm in younger patients (p < 0.05). The basilar artery was straight in 36.7%, convex to the right in 47.5% and convex to the left in 14.2% of the patients. Mean diameter of the left P1 was 1.80 ± 0.58 mm, and of the right 1.87 ± 0.54 mm. There was no statistically significant difference between the diameters of the left and right P1 segments of the PCA and also between genders (p > 0.05). CONCLUSION: Modern non-invasive imaging modalities can provide precise and useful information for vessels analysis. This information may be useful for planning and performing neuro-interventional procedures as well as posterior cranial fossa surgeries.

A comparison of basilar artery diameters measured by T2WI and TOF MR angiography.

PURPOSE: The purpose of our study is to compare basilar artery diameters (BAD) measured by T2WI to diameters measured by TOF MR angiography (MRA). By doing this, we hope to understand how compatible these two methodologies are with each other. METHODS: We used data from 100 patients (59 females, 41 males) who underwent a session of both T2W MRI and TOF MRA at the same time (ages between 18 and 83). We measured BAD by both T2WI and TOF MRA in three different levels. We then compared these diameters measured by two different methodologies to each other. RESULTS: In an area between the vertebrobasilar junction and posterior cerebral artery, all data measured by T2WI and TOF MRA in three different levels were analyzed. Average diameters measured by T2WI and TOF MRA turned out to be 79.5% correlated with each other. As a result of our mathematical model that we came up with through regression analysis, we calculated that measurements taken by T2WI on mid-pontine levels could predict TOF MRA measures with 78.3% accuracy. In T2WI and TOF MRA, average diameters measured were 2.982 ± 0.4717 and 3.205 ± 0.4281 mm, respectively. Statistical analyses showed that images measured by T2W series were significantly smaller than those measured by TOF MRA (p < 0.05). CONCLUSION: Our study showed that BAD measured by T2WI were smaller than those measured by TOF MRA. We think that it will be beneficial to refer our results to avoid T2WI and TOF MRA mismatch when evaluating BAD.

The cisternal segments of the oculomotor nerve: a magnetic resonance imaging study.

PURPOSE: The cisternal segments of the oculomotor nerve (OMN), which courses through the interpeduncular and oculomotor cisterns (OMC) have not been well delineated on neuroimages. The present study aimed to explore the cisternal segments of the OMN using magnetic resonance (MR) imaging. METHODS: A total of 92 patients were enrolled in this study. A constructive interference in steady-state sequence was performed in coronal and axial sections. RESULTS: On coronal images, cisternal portions of the OMN were entirely delineated in 97 % on the right and in 98.5 % on the left. Most of the OMCs were of a round shape, with a centrally located OMN, while 9 % were ectatic with the OMN located eccentrically. In 5.3 % of cases, fetal-type posterior communicating arteries (PCoAs), which coursed adjacent to the superior surfaces of the OMNs at the oculomotor triangle (OMT), were observed. On axial images, cisternal portions of the OMN were identified in all cases. The OMN segment passing through the OMT showed medial, central, and lateral courses. The PCoAs and P2 segments of the posterior cerebral artery (PCA) were adjacent to the OMNs in 17 and 19 % of cases, respectively. CONCLUSIONS: The OMN most frequently courses in the medial part of the OMT and enters into the OMC. These findings indicate that OMN paresis can be caused by vascular compression at any site of the interpeduncular cistern and OMT.

Lateral Thalamic Infarction and the Vascular Geometry of the Posterior Cerebral Artery.

BACKGROUND: The geometric properties of the parental artery affect the development of local atherosclerosis and perforator infarction. In this study, we aimed at investigating the association between vascular geometry of the posterior cerebral artery (PCA) and the development of isolated lateral thalamic infarction (LTI), the most frequent type of thalamic infarction. METHODS: The geometric properties of the corresponding PCA in LTI patients were assessed and they include the diameters of the distal basilar artery (BA) and proximal PCA, distal BA - PCA angle, first PCA angle (angle between P1 and P2), and the presence of the posterior communicating artery (Pcom). These parameters obtained from the ipsilesional PCA were compared with the contralesional PCA and the corresponding PCA in age- and sex-matched controls. RESULTS: Forty-five LTI patients were enrolled. The ipsilesional PCA in LTI patients demonstrated a greater ipsilesional P1 - P2 angle (81.4 ± 22.6 vs. 71.3 ± 23.2°, respectively; p = 0.04) and a higher prevalence of Pcom (42.2 vs. 13.3%; p = 0.002) when compared to control subjects. In comparison with the contralesional PCA, ipsilesional PCA demonstrated a smaller diameter, larger angle between P1 and P2 segment, and a higher prevalence of Pcom. The presence of hyperlipidemia (OR 3.548 (1.283-9.811); p = 0.02) and Pcom (OR 3.507 (1.104-11.135); p = 0.03) was a factor that was independently associated with LTI. CONCLUSIONS: Local hemodynamics in the PCA may be influenced by the P1 - P2 angle and the presence of Pcom, which are associated with the development of LTI.

Microsurgical Approaches to the Ambient Cistern Region: An Anatomic and Qualitative Study.

OBJECTIVE: We used microscopy to conduct qualitative and quantitative analysis of 4 surgical approaches commonly used in the surgery of the ambient cistern: infratentorial supracerebellar (SC), occipital interhemispheric, subtemporal (ST), and transchoroidal (TC). In addition, we performed a parahippocampal gyrus resection in the ST context. METHODS: Each approach was performed in 3 cadaveric heads (6 sides). After the microscopic anatomic dissection, the parahippocampal gyrus was resected through an ST approach. The qualitative analysis was based on anatomic observation and the quantitative analysis was based on the linear exposure of vascular structures and the area of exposure of the ambient cistern region. RESULTS: The ST approach provided good exposure of the inferior portion of the cistern and of the proximal segments of the posterior cerebral artery. After the resection of the parahippocampal gyrus, the area of exposure improved in all components, especially the superior area. A TC approach provided the best exposure of the superior area compared with the other approaches. The posterolateral approaches (SC/occipital interhemispheric) to the ambient cistern region provided similar exposure of anatomic structures. There was a significant difference (P < 0.05) in linear exposure of the posterior cerebral artery when comparing the ST/TC and ST/SC approaches. CONCLUSIONS: This study has demonstrated that surgical approaches expose dissimilarly the different regions of the ambient cistern and an approach should be selected based on the specific need of anatomic exposure.

Temporal branch of the posterior cerebral artery arising from the posterior communicating artery diagnosed by MR angiography.

We report a case in which the temporal branch of the posterior cerebral artery (PCA) arose from the posterior communicating artery (PCoA) and was diagnosed by magnetic resonance (MR) angiography. The PCoA arose from its normal point on the supraclinoid internal carotid artery and fused with the PCA at its normal point of the P1-P2 junction. We believe this is the first report of such a variation. Careful review of MR angiographic images is important to detect rare arterial variations, and partial maximum-intensity-projection images aid their identification on MR angiography.

Clinical significance of blood supply to the internal capsule and basal ganglia.

Although the general vascular supply of the basal ganglia and internal capsule is well known, precise data are lacking regarding the variations of the vascular territories in the two regions. Twelve hemispheres were studied following an injection of coloured ink into the main cerebral arteries, namely the anterior cerebral (ACA), middle cerebral (MCA), anterior choroidal (AChA) and posterior cerebral artery (PCA). Serial sections of the injected hemispheres were taken in the axial or coronal plane. In 75% of the hemispheres, ACA perforators were seen to supply the inferomedial part of the head of the caudate nucleus and the anterior limb of the internal capsule, as well as the anterior and inferior portions of the putamen and globus pallidus. The MCA vessels perfused the superolateral part of the head and body of the caudate nucleus, the superior part of the entire internal capsule, most of the putamen and part of the globus pallidus. The AChA perforators perfused the medial segment of the globus pallidus, the inferior part of the posterior limb, the retrolenticular and sublenticular portions of the internal capsule, and occasionally its genu. The same segment of the globus pallidus and the inferior part of the genu of the internal capsule were most likely supplied by the perforators of the internal carotid artery. A predominance of ACA territory was noticed in one specimen (8.33%) and a predominance of MCA territory in two specimens (16.67%). The obtained anatomical data may help radiologic determination of perforators involved in ischemic events, as well as a better understanding of the neurological deficits in the same events.

Association Between Vascular Anatomy and Posterior Communicating Artery Aneurysms.

OBJECTIVE: Hemodynamic stress, conditioned by the geometry and morphology of the vessel trees, plays an important role in the formation of intracranial aneurysms. The aim of this study was to identify image-based location-specific morphologic parameters that are associated with posterior communicating artery (PCoA) aneurysms. METHODS: Morphologic parameters obtained from computed tomography angiography of 56 patients with PCoA aneurysms and 23 control patients were evaluated with 3D Slicer, an open-source image analysis software, to generate 3-dimensional models of the aneurysms and surrounding vasculature. Segment lengths, diameters, and vessel-to-vessel angles were examined. To control for genetic and clinical risk factors, the unaffected contralateral side of patients with unilateral PCoA aneurysms was used as a control group for internal carotid artery (ICA)-related parameters. A separate control group with visible PCoAs and aneurysms elsewhere was used as a control group for PCoA-related parameters. RESULTS: Internal carotid artery-related parameters were not statistically different between the PCoA aneurysm and control groups. Univariate and multivariate subgroup analysis for patients with visualized PCoAs demonstrated that a larger PCoA diameter was significantly associated with the presence of a PCoA aneurysm (odds ratio = 12.1, 95% confidence interval = 1.3-17.1, P = 0.04) after adjusting for other morphologic parameters. CONCLUSIONS: Larger PCoA diameters are associated with the presence of PCoA aneurysms. These parameters may provide objective metrics to assess aneurysm formation and growth risk stratification in high-risk patients.

Variations and morphometric analysis of the proximal segment of the superior cerebellar artery.

INTRODUCTION: The superior cerebral artery is a clinically significant vessel, but little is known about its radiological anatomy. The aim of this study was to describe the anatomical variations of the proximal segment of the superior cerebellar artery using Computed Tomography Angiography. MATERIALS AND METHODS: The study group consisted of 200 subjects (54.5% female, mean age ± SD 56.2 ± 17.2 years) that had undergone head Computed Tomography Angiography. Subjects with any intracranial pathologies were excluded. Images in Maximum Intensity Projections were used to study the anatomical anomalies of the superior cerebellar artery. RESULTS: In 200 subject 388 superior cerebellar arteries were found. Twelve (3.09%) SCAs were duplicated in 11 patients and all originated from the basilar artery. In 8 (4.00%) patients the superior cerebellar artery was absent. The origin of the SCA was most often bilateral, mainly from the basilar artery (76.29%). The superior cerebellar artery diameter, measured at the site of the origin, was statistically significantly different depending on the place of the origin: wider when originating from the basilar artery as a single vessel (1.48 ± 0.42 mm vs. 1.34 ± 0.52 mm; p=0.03) and narrower when originating as duplicated one (1.38 ± 0.48 mm vs. 1.46 ± 0.44 mm; p=0.55). CONCLUSION: Superior cerebellar artery usually originates bilaterally from the basilar artery as a single trunk. Its diameter is significantly wider in that type in comparison to other anatomical variations.