Infundibular dilations of the posterior communicating arteries: pathogenesis, anatomical variants, aneurysm formation, and subarachnoid hemorrhage

Replaced posterior cerebral artery

PURPOSE

Replaced posterior cerebral artery (PCA), defined as a hyperplastic anterior choroidal artery (AChA) supplying all branches of the PCA, is an extremely rare anatomical variation. To the best of our knowledge, there are only a few reports of replaced PCA.

METHODS

Herein, we report a case of replaced PCA diagnosed by digital subtraction angiography.

RESULTS

A 76-year-old woman visited a neurosurgical clinic because of headache and vertigo. Magnetic resonance imaging and magnetic resonance angiography incidentally revealed a left internal carotid artery aneurysm. She was referred to our hospital for further examination and treatment of the unruptured intracranial aneurysm. Left internal carotid angiography revealed a paraclinoid aneurysm. We also incidentally found an anomalous hyperplastic AChA distal to the aneurysm. This hyperplastic AChA supplied not only the AChA territory but also the entire PCA territory. No vessels that could be a normal AChA or posterior communicating artery were identified along the left internal carotid artery. Vertebral angiography demonstrated that the left PCA was not visualized. With these findings, we diagnosed anomalous hyperplastic AChoA in this case as replaced PCA.

CONCLUSION

Careful imaging assessment is important to identify replaced PCA. Both direct findings of a hyperplastic AChA course and perfusion territory and indirect findings of the absence of the original PCA are useful in the diagnosis of replaced PCA.

Infundibular Widening of Angiographically Invisible Duplicate Anterior Choroidal Artery Mimicking Typical Anterior Choroidal Artery Aneurysm

A diagnosis of an intracranial aneurysm depends on the angiographic configuration and should be cautiously differentiated from aneurysm mimics. In cases of duplicate anterior choroidal arteries (AChAs), infundibular widening of the distal minor AChA can be an aneurysm mimic. If the minor AChA with a smaller diameter is obscured angiographically due to poor contrast filling, an associated infundibular widening beside the proximal large AChA can misinterpreted as a typical AChA aneurysm in angiograms. The authors report on two such cases of duplicate AChAs with infundibular widening presenting like a typical AChA aneurysm in angiograms. Surgical exploration revealed a perforating artery emitting from the dome of the saccular lesion, confirming infundibular widening of a duplicate AChA. No reparative procedure was applied to the infundibular widening in a 48-year-old man, while two vascular outpouchings from the infundibular widening were clipped preserving the duplicate AChA in a 55-year-old woman.

Flow Diversion for the Management of Ruptured Intracranial Arterial Infudibular Dilatation: Proof of Principle and Therapeutic Protocol

Thought to be benign anatomical variants, cerebral infundibular dilatations (ID) are most commonly encountered at the junction of the internal carotid artery (ICA) and the posterior communicating artery (PcomA). The true nature of this entity remains controversial, as some literature reports suggest they should be considered preaneurysmal lesions and a potential source of devastating subarachnoid hemorrhage. This report describes cases of presumably ruptured IDs and their therapeutic endovascular management. We retrospectively reviewed and analyzed patients with isolated subarachnoid hemorrhage (SAH) where the only potential cause was ruptured cerebral IDs, treated or not, between January 2012 and June 2021. Morphological and radiological features, treatment and procedural considerations, clinical and angiographic outcomes were also reviewed. Natural history of the ID is poorly understood, and its relation to SAH remains controversial. Ruptured cerebral IDs can be the suspected cause of bleeding if no other vascular lesion is present during multimodal examinations. Endovascular flow diversion stenting is safe and effective for the proper treatment of ruptured IDs. Pending further validations with longitudinal data are needed to legitimate the natural course of these mysterious lesions.

Epidemiologic and anatomic aspects comparing incidental and ruptured intracranial aneurysms: A single centre experience

The feasibility of multicentric international data such as integrated in the PHASES score for patient counseling in unruptured intracranial aneurysms has recently been challenged. To determine, whether this data is applicable to local populations in a restricted catchment area, we performed a retrospective mono-centric analysis comparing patients with ruptured aneurysms to patients with incidental aneurysms. 200 patients with unruptured aneurysms and 197 patients after aneurysmal subarachnoid hemorrhage were analyzed for risk factors differing between the groups and to the general German population. Subgroup analysis was performed for 25 patients harboring multiple aneurysms, in 19 patients with intracavernous aneurysms and in 77 women of childbearing potential. While the preponderance of female patients was confirmed, significantly more men figured in the patient group with subarachnoid hemorrhage (36.4%) than among unruptured aneurysms (25%). Patients with bleeding events were significantly younger (51.6 years) than patients with incidental aneurysms (57.8 years). The rupture risk prediction of the PHASES score concerning aneurysm size below 7 mm and patient age over 70 years could not be confirmed, instead score points correlated to the clinical outcome after rupture. In our population, pregnant women were not overrepresented. Intracavernous carotid aneurysms contributed to the low risk profile of giant aneurysms. Thus, recommendations from pooled international data have to be adapted cautiously to local circumstances. We retained seven items with predictive value for outpatient counseling: age, smoking, hypertonus and concurrent vascular aberrations as patient characteristics and irregular shape, (increasing) largest diameter and the harboring vessel for the aneurysm.

Aneurysms of the communicating segment of the internal carotid artery with posterior communicating artery agenesis are associated with perforator infarction after embolization

BACKGROUND

While anatomic features associated with the risk of posterior communicating artery (PcoA) occlusion after embolization of aneurysms of the PcoA segment of the internal carotid artery (ICA) are well known, the link between perforator origin and perforator infarction has only been reported following neurosurgical clipping. The aim of this study was to determine the origin of anterior thalamic perforators and correlate it with risk of perforator infarction after embolization of PcoA segment aneurysms.

METHODS

One-hundred-and-ninety consecutive patients treated for PcoA segment aneurysms between 2017 and 2019 were included. PcoA and anterior thalamic perforator origin anatomy was assessed with computed tomography (CT) angiography, digital subtracted angiography, and high-resolution three-dimensional rotational cone-beam CT angiography (CBCT-A) by two independent interventional neuroradiologists. The presence of perforator infarction after embolization was ascertained from the patient's notes and follow-up imaging.

RESULTS

CBCT-A was superior in demonstrating the origin of perforators (P<0.001). The prevalence of perforator origin was estimated at 86% (95% CI 81%-92%) for PcoA, 8% (95% CI 4%-13%) for aneurysm wall, and 5% (95% CI 2%-9%) for ICA. The aneurysm wall origin was exclusively associated with PcoA agenesis, as well as higher risk of perforator infarction after aneurysm coiling compared with other variants (OR=14, 95% CI 2-88, P=0.006).

CONCLUSIONS

Our study suggests that anterior thalamic perforators may arise from aneurysm wall when there is no PcoA. Anatomic association between PcoA agenesis and perforator arising from ICA could underlie such findings, and careful consideration is essential before aneurysm repair to anticipate the risk of thalamic infarction in such cases.

Infundibulum of Accessory Anterior Cerebral Artery: Rare, Likely Benign Malformation of Anterior Communicating Artery Complex to Keep in Mind

BACKGROUND

Infundibular dilations (IDs) are funnel-shaped enlargements located at the origin of cerebral arteries. Neuroradiologists and neurosurgeons are familiar with IDs of the posterior communicating artery, which are relatively common. Other locations, being unexpected sites of IDs, can pose diagnostic and therapeutic challenges.

CASE DESCRIPTION

In this paper, we describe a case of infundibulum of the accessory anterior cerebral artery, diagnosed with 3-dimensional reconstructions of computed tomography angiography, which is to our knowledge the first report of an ID of this anatomic variant.

CONCLUSIONS

Anterior communicating artery represents a rare location for infundibular dilations. Differential diagnosis between them and true aneurysms can be sometimes challenging, especially when associated with anatomic variants; thus neurosurgeons and radiologists must be aware of these pathologic entities.

A Novel Scoring System for Rupture Risk Stratification of Intracranial Aneurysms: A Hemodynamic and Morphological Study

Objective: The aim of the present study is to investigate the potential morphological and hemodynamic risk factors related to intracranial aneurysms (IAs) rupture and establish a system to stratify the risk of IAs rupture to help the clinical decision-making. Methods: Patients admitted to our hospital for single-IAs were selected from January 2012 and January 2018. A propensity score matching was conducted to match patients. The morphological parameters were obtained from high solution CTA images, and the hemodynamic parameters were obtained in accordance with the outcomes of computational fluid dynamics (CFDs) simulation. Differences in the morphologic and hemodynamic parameters were compared. The significant parameters were selected to establish a novel scoring system (Intracranial Aneurysm Rupture Score, IARS). The comparison was drawn between the discriminating accuracy of IARS and the Rupture Resemblance Score (RRS) system to verify the value of IARS. Then, a group of patients with unruptured IAs was stratified into the high risk and low risk groups by IARS and RRS system separately and was followed up for 18-27 months to verify the value of IARS. The outcome of different stratifications was compared. Results: The matching process yielded 167 patients in each group. Differences of statistical significance were found in aneurysm length (p = 0.001), perpendicular height (H) (p < 0.001), aspect ratio (AR) (p < 0.001), size ratio (SR) (p < 0.001), deviated angle (DA) (p < 0.001), normalized average wall shear stress (NWSSa) (p < 0.001), wall shear stress gradient (WSSG) (p < 0.001), low shear area ratio (LSAR) (p = 0.01), and oscillatory shear index (OSI) (p = 0.01). Logistic regression analysis further demonstrated that SR, DA, NWSSa, LSAR, and OSI were the independent risk factors of IAs rupture. SR, DA, LSAR, and OSI were finally selected to establish the IARS. Our present IARS showed a higher discriminating value (AUC 0.81 vs. 0.77) in comparison with the RRS (SR, NWSSa, and OSI). After follow-up, seven patients were subject to IAs rupture. 5/26 in high risk group stratified by IARS, yet 7/57 in high risk group stratified by RRS. The accuracy of IARS was further verified (19.2% vs. 12.3%, AUC for the IARS and the RRS was 0.723 and 0.673, respectively). Conclusion: SR, DA, NWSSa, LSAR, and OSI were considered the independent risk factors of IAs rupture. Our novel IARS showed higher accuracy in discriminating IA rupture in comparison with RRS.