The Fetal Type of Posterior Cerebral Artery

"Complete" duplication of the posterior cerebral artery: a rare variant detected on computed tomography angiography

The cerebral arterial circle morphologic variability has been extensively studied. The posterior cerebral artery (PCA) variants are rarely identified, except from the first segment (P1) hypoplasia or absence. Due to its unique morphology, the computed tomography angiography (CTA) of a 34-year-old female patient was further investigated. On the right side, the typical PCA originated as the terminal branch of the basilar artery. An accessory PCA was also identified originating from the right internal carotid artery (ICA), while the right posterior communicating artery was absent. This variant corresponds to the "complete" duplication of the PCA. The left-sided PCA originated from the ICA, while the P1 was hypoplastic, representing the "partial fetal-type PCA." The rest of the cerebral arterial circle was typical. The present case of PCA "complete" duplication corresponds to a scarce variant, with a reported prevalence of 0.04%, while the fetal-type PCA is the most commonly observed variant.

The prevalence of the fenestrated left renal vein

PURPOSE

The left renal vein (LRV) is typically a single preaortic vein. The discovery of fenestrated LRVs (FLRVs), a rare occurrence previously reported only twice, has piqued our interest. We aimed to determine the prevalence of such variants using an angioCT batch.

METHODS

We meticulously studied archived angioCT files of 95 men and 55 women. The morphology of the LRVs was carefully checked on planar sections and by three-dimensional volume renderings, ensuring the accuracy of our findings.

RESULTS

In 3.34% of cases, four males and one female were found FLRVs. Their posterior projections on the aorta were variable. The FLRVs were either partly preaortic, immediately to the left side of the aorta, or at a distance to the left side of the aorta. There were three true FLRVs, with a single vein attached at the lateral end and two pseudo-fenestrations, with two veins attached laterally. The left suprarenal and gonadal veins drained, respectively, in the superior and inferior arms of the fenestrations. In 2/5 cases, the second left lumbar vein drained into the inferior arms of the fenestrations. In one case, the FLRV was traversed by the inferior segmental branch of the renal artery.

CONCLUSION

Our findings have significant implications for surgical procedures targeting the left renal pedicle. The FLRV, with its morphological and topographical variability, should be considered among the anatomical variations of the LRV that may impede or endanger such procedures. However, it can be accurately discriminated on angioCT scans, providing a potential solution to this challenge.

Morphology and Variations of the Posterior Cerebral Artery: A Literature Review

The human brain is supplied by a complex network of vessels, including the circle of Willis (CoW), which provides collateral circulation to ensure optimal perfusion during vascular blockages. An essential component of the CoW is the posterior cerebral artery (PCA), which supplies blood to the occipital lobe, visual cortex, and other cortical brain areas. The PCA typically originates from the bifurcation of the basilar artery but can show variations, such as "fetal-type" PCA. These variations, including hypoplasia, aplasia, duplication, and fenestration, can considerably impact cerebral vasculature and increase the risk of ischemic stroke, aneurysms, and visual impairment. The PCA is divided into multiple segments (P1, P2, P3, P4, and sometimes P5), each with diverse anatomical and morphological variations. Variations in PCA morphology can complicate cerebrovascular management and influence surgical approaches. Understanding these variations is crucial for accurate diagnosis and effective treatment of PCA-related complications. This literature review explores the anatomy of the PCA, including its embryological development, the implications of its variations, and the possible clinical outcomes related to these anomalies.

The Incidence and Variants of the Reno-Hemiazygos Connection

Background/Objectives: Although common anomalies of the left renal vein (LRV) are pretty well documented in the literature, the drainage of the left renal blood via the hemiazygos vein lacks comprehensive support. We, therefore, aimed to study the incidence of the reno-hemiazygos connection (RHC). Methods: A total of 150 computed tomography scans (85 men and 65 women) were documented for the origin of an RHC from the LRV. Results: RHCs were found in 14/150 cases (9.34%). They were more prevalent in women (71.43%). In 11/14 cases, type 1 RHCs ascended directly along the postero-lateral left side of the aorta (direct hemiazygos flow). In 3/14 cases, type 2 RHCs (indirect hemiazygos flow) had a lumbar segment corresponding to the second lumbar vein and a pretransversary segment corresponding to an ascending lumbar vein. In 9/14 cases (64.29%), the RHC was connected to a typical LRV. In 1/14 cases (7.14%), the RHC was connected to the junction between the LRV and a left retropelvic tributary. In another case (7.14%), the RHC was connected to a retroaortic LRV and, in three cases (21.43%), to a circumaortic LRV. Triple left renal arteries were found in type 1 and, respectively, type 2 cases. The vertebral level of the inferior end of the RHC was variable, from the L1/L2 disc level to the L3 level. Conclusions: When present, the RHC serves to connect the superior and inferior caval systems. This may be physiologically of use or not, but surgically, it is a major anatomical risk factor for bleeding if its presence is not checked preoperatively.

Understanding external carotid artery collateralisation after cerebral revascularisation in moyamoya disease: insights from quantitative analysis

BACKGROUND

This study aims to quantitatively evaluate collateralisation angiogenesis ratio (CAR) of external carotid artery and intracranial arterial residual volumes (ARV) postcerebral revascularisation in moyamoya disease (MMD) and elucidate the factors influencing external carotid artery collateralisation.

METHODS

The study retrospectively analysed 297 patients diagnosed with MMD who underwent cerebral revascularisation at our University's Hospital, between January 2015 and May 2023. The clinical data, imaging results and surgical specifics for the patients were collected. Using a newly proposed digital subtraction angiography-based evaluation system, the CAR of external carotid artery and the intracranial ARV were evaluated quantitatively following standardised protocols.

RESULTS

The study included 136 male and 161 female patients. The severity of ischaemic (r=-0.297) and haemorrhagic (r=-0.270) MMD, as assessed by the Suzuki stage, demonstrated a significant negative correlation with intracranial ARV (p<0.001). However, no significant correlation was observed between the intracranial ARV and the modified Rankin Scale scores. Patients with fetal-type posterior cerebral arteries exhibited greater intracranial ARV compared with those without (p=0.003). Additionally, a positive correlation was observed between external carotid artery collateralisation and intracranial ARV post-revascularisation (r=0.340, p<0.001). The CAR of external carotid artery following cerebral revascularisation in patients with MMD remained independent correlation of the intracranial ARV (β=0.385, 95% CI (0.921 to 1.669), p<0.001) and Suzuki stage (β=0.211, 95% CI (0.009 to 0.030), p<0.001).

CONCLUSIONS

This study showed a complex association between ARV, the Suzuki stage and the collateralisation of the external carotid artery in patients with MMD who are undergoing revascularisation. These findings provide insights into MMD progression and revascularisation outcomes and may guide clinical decision-making to improve patient care.

A Prevalence Anatomic-Imaging Study of the Posterior Inferior Cerebellar Artery's Origin

Background and Objectives: Typically, the vertebral arteries (VAs) enter the posterior fossa through dural rings and further unite, forming the basilar artery. The posterior inferior cerebellar artery (PICA) is usually a branch of the V4 segment of the VA (intradural origin). It may also leave the V3 suboccipital segment of the VA (extradural origin). The transdural origin of the PICA within the VA's dural ring has been consistently overlooked. A study was designed to determine the topographical patterns of the PICA's origin. Materials and Methods: Determinations were performed in a retrospective sample of 225 computed tomography angiograms. Four types of PICA origin were documented: type 0, absent PICA; type 1, the extradural origin of the PICA from the V3 segment of the VA; type 2, the transdural origin of the PICA within the dural ring; and type 3, the intradural origin of the PICA from the V4 segment of the VA. The bilateral symmetry of types was also investigated. Results: Out of 450 VAs, type 0 (absent PICA) was found in 36%, type 1 (extradural) in 0.44%, type 2 (transdural) in 5.56%, and typical type 3 in just 58%. In types 1 and 2, the PICA entered the posterior fossa through the dural ring and the marginal sinus. In the overall group (N = 225), the type combinations 1_1, 1_2 and 1_3 were not found. Bilaterally absent PICAs occurred in 18.67%. The bilateral combinations 0_1/0_2/0_3/2_2/2_3/3_3 were found, respectively, in 0.89%/3.11%/30.67%/1.78%/4.44%/40.44%. Four of the seventy-eight PICAs opposite to an absent one, three intradural and one transdural, were true bihemispheric PICAs. Conclusions: The PICAs with extradural or transdural origins are facultative contents of the dural ring and are at risk during neurosurgical approaches in the foramen magnum. Rare bihemispheric PICAs could originate either intradurally or within the dural ring.

Rare simultaneous fetal posterior cerebral artery and conventional posterior cerebral artery duplication in a patient with a ruptured posterior communicating artery aneurysm: illustrative case

BACKGROUND

The fetal-type posterior cerebral artery (PCA) is defined as a variant anatomy in which the posterior communicating artery (PCOM) is larger than the hypoplastic or aplastic P1 segment of the PCA. The authors present the novel case of a patient with a duplicated right PCA in parallel with fetal-type and conventional PCAs supplying adjacent components of the PCA cerebral territory.

OBSERVATIONS

A 59-year-old woman presented with a modified Fisher Scale score 4 subarachnoid hemorrhage. A right irregular PCOM aneurysm that measured 9.5 mm × 4.5 mm × 4.5 mm arose from the base of a variant branch supplying a portion of the PCA, rather than a conventional PCOM, and was found on digital subtraction angiography. Following endovascular coil embolization, the patient was discharged home.

LESSONS

The fetal-type variant has implications for thromboembolic events. If an embolism occludes the anterior circulation in a patient with a fetal-type PCA, it may result in an infarct in the PCA territory. Awareness of cerebral arterial anatomy, including an atypical collateral supply, informs a treating team's latitude in tolerance of which sites must be preserved and which can be safely sacrificed. https://thejns.org/doi/10.3171/CASE23735.

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.

The Vertebrobasilar Trunk and Its Anatomical Variants: A Microsurgical Anatomical Study

BACKGROUND

The trunk of the basilar artery has not been included in microanatomy studies. Anatomical variants of the perforant branches of the vertebrobasilar trunk and their relationship with neural structures are very important in surgical approaches. Surgical dissection for the treatment of vascular lesions requires a perfect knowledge of the microsurgical anatomy.

METHODS

We conducted a descriptive analysis of 50 brains, which were fixed with formalin at 10% for 2 weeks, and the arterial system was injected with colored latex. After microsurgical dissection, it was divided into three segments: the lower portion went from the anterior spinal artery to the anteroinferior cerebellar artery, the middle segment was raised from the upper limit of the lower portion to the origin of the superior cerebellar artery, and the upper segment ranged from the previous portion until the origin of the posterior cerebral artery.

RESULTS

The basilar artery had an average length of 30 mm. The average diameter at its junction with the vertebral arteries was 4.05 mm. The average middle segment was 3.4 mm in diameter and 15.2 mm in length. The diameter of the upper segment was 4.2 mm, and its average length was 3.6 mm. The average number of bulbar arteries was three, and their average diameter was 0. 66 mm. The number of caudal perforator arteries were five on average, with a diameter of 0.32 mm. We found three rare cases of anatomical variants in the vertebra-basilar junction.

CONCLUSIONS

The basilar artery emits penetrating branches in its lower, middle, and upper portions. The origin of penetrating branches was single or divided after forming a trunk. However, we observed long branches from perforant arteries.

An Update on the Superior Cerebellar Artery Origin Type

Background and Objectives: The microanatomy of the superior cerebellar artery (SCA) is clinically significant. We, thus, aimed at patterning unilateral and bilateral possibilities of SCA origin. Materials and Methods: In total, 205 archived records of computed tomography and magnetic resonance angiograms were used. There were defined types of SCA origin from the basilar artery (BA): "0"-absent SCA, "1"-preterminal, "2"-collateral SCA, with SCA appearing as a terminal branch of BA, and "3"-SCA from the posterior cerebral artery (PCA) of the cerebral type. Fenestrations and duplications of SCA were recorded. Bilateral combinations of types were recorded as follows: A (1 + 0), B (1 + 1), C (1 + 2), D (1 + 3), E (1 + duplicated SCA), F (2 + 2), G (2 + 3), H (3 + 3), I (3 + duplicated SCA), J (1 + fenestrated SCA). Results: Type 0 SCAs were found in 0.25%, type 1 in 71.29%, type 2 in 19.06%, and type 3 in 9.41%. Absent and fenestrated SCAs were each found in a single case. The most frequent combinations were B (58.05%), C (13.17%) and F (13.17%). Bilateral symmetrical types occurred in 70.7% of cases. Fetal types of PCA and the artery of Percheron modified the BA ends. Combinations of C, F, and G changed the BA ends or tips; thus, different subtypes resulted in five BA bifurcation patterns, including five BA trifurcations and one BA quadrifurcation. BA trifurcation was also found in cases with duplicated SCAs. Conclusions: The SCA has various anatomical possibilities of origin and bilateral combinations that are not presented in anatomical lectures. Details on the specific end of the BA should be gathered on a case-by-case basis.

Bihemispheric Right Anterior Cerebral Artery, Fenestrated Origin of the Left Pericallosal Artery, Fenestrated Basilar Artery, Double Right Posterior Cerebral Artery

Anatomical variations of the cerebral vasculature are frequently encountered. The archived magnetic resonance angiogram of a 62-year-old male patient was studied anatomically on planar slices and 3-dimensional volume renderings. Numerous anatomical variants were found in that single case. In the vertebrobasilar system were found: the proximal basilar artery fenestration, with a unilateral origin from that fenestration of an anterior inferior cerebellar artery, and the unilateral origin of the superior cerebellar artery from the P1 segment of the main posterior cerebral artery (PCA). There were also unilateral variants of the right internal carotid artery (ICA): a subvariant of an accessory PCA leaving the ICA as a hyperplastic anterior choroidal artery and united to the main PCA by a short communicating branch, distinctive of the posterior communicating artery in that side (unilateral double PCA); a right bihemispheric anterior cerebral artery (ACA) but with complete agenesis of the contralateral A1 ACA segment; from the right ACA continued an anatomically normal ipsilateral A2 segment and a short transverse contralateral A2 that, in turn, sent off long pericallosal and callosomarginal arteries; and fenestrated origin of the left pericallosal artery. Therefore, an arterial variant in one of the main cerebral circulations could not exclude anatomical variants in the other cerebral circulatory beds.