[Anatomical Variations to the Vertebral Artery and Posterior Inferior Cerebellar Artery are Associated with the Partial Persistence of Primitive Lateral Basirovertebral Anastomosis].

The angioarchitecture of the hindbrain is homologous to that of the spinal cord, and its vascular system can be analyzed at the longitudinal and axial structures. During embryonic development, there are two main longitudinal arteries: the longitudinal neural artery and the primitive lateral basilovertebral anastomosis. Commonly observed variations are formed by the fenestration and duplication of either the vertebrobasilar artery, or cerebellar artery, which can be observed when the primitive lateral basilovertebral anastomosis partially persists. Understanding the pattern and development of blood supply to the hindbrain provides useful information of various anomalies in the vertebrobasilar junction and cerebellar arteries.

[Basilar Artery, Anterior Inferior Cerebellar Artery, Superior Cerebellar Artery].

The basilar artery(BA)is formed by the fusion of two longitudinal arteries, and incomplete development may lead to BA fenestration. The BA provides many short perforating arteries and long lateral pontine arteries to the brain stem. The anterior inferior cerebellar artery(AICA)usually branches from the proximal third of the BA and primarily perfuses the ventral, inferior and lateral aspect of the cerebellum and inner ear organ. However, there are many variations to the AICA that depend on the degree of posterior inferior cerebellar artery development. The superior cerebellar artery(SCA)branches into not only to the rostral, ventral aspect of the cerebellar hemisphere, but also to the deeper cerebellar nucleus and brain stem. Duplications within this vessel are frequently identified, but it is not missing.

Perivascular neurons instruct 3D vascular lattice formation via neurovascular contact.

The vasculature of the central nervous system is a 3D lattice composed of laminar vascular beds interconnected by penetrating vessels. The mechanisms controlling 3D lattice network formation remain largely unknown. Combining viral labeling, genetic marking, and single-cell profiling in the mouse retina, we discovered a perivascular neuronal subset, annotated as Fam19a4/Nts-positive retinal ganglion cells (Fam19a4/Nts-RGCs), directly contacting the vasculature with perisomatic endfeet. Developmental ablation of Fam19a4/Nts-RGCs led to disoriented growth of penetrating vessels near the ganglion cell layer (GCL), leading to a disorganized 3D vascular lattice. We identified enriched PIEZO2 expression in Fam19a4/Nts-RGCs. Piezo2 loss from all retinal neurons or Fam19a4/Nts-RGCs abolished the direct neurovascular contacts and phenocopied the Fam19a4/Nts-RGC ablation deficits. The defective vascular structure led to reduced capillary perfusion and sensitized the retina to ischemic insults. Furthermore, we uncovered a Piezo2-dependent perivascular granule cell subset for cerebellar vascular patterning, indicating neuronal Piezo2-dependent 3D vascular patterning in the brain.

Ruptured aneurysm in collateral arteries with blood-flow impairment of posterior inferior cerebellar artery: a report of three cases.

Herein, we report three cases of cerebellar hemorrhage due to a ruptured small aneurysm located on a collateral artery compensating for one or more stenotic or occluded major cerebellar arteries. In each case, endovascular distant parent artery occlusion of both the collateral artery and aneurysm was performed to prevent rebleeding. A ruptured small aneurysm in a collateral artery may be observed in patients with hemorrhage in an atypical cerebellar region, especially in cases of stenosis or occlusion of the vertebral artery or posterior inferior cerebellar artery. Thus, cerebral angiography is recommended to rule out collateral artery aneurysm.

Posterior Inferior Cerebellar Artery-Posterior Inferior Cerebellar Artery Bypass versus Occipital Artery-Posterior Inferior Cerebellar Artery Bypass for Treating Posterior Circulation Aneurysms: A Systematic Review and Comparative Meta-Analysis.

BACKGROUND: When traditional therapies are unsuitable, revascularization becomes essential for managing posterior inferior cerebellar artery (PICA) or vertebral artery aneurysms. Notably, the PICA-PICA bypass has emerged as a promising option, overshadowing the occipital artery-PICA (OA-PICA) bypass. The objective was to compare the safety and efficacy of OA-PICA and PICA-PICA bypasses. METHODS: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we conducted a systematic review and meta-analysis to evaluate the safety and efficacy of OA-PICA and PICA-PICA bypasses for treating posterior circulation aneurysms. RESULTS: We analyzed 13 studies for the PICA-PICA bypass and 16 studies on the OA-PICA bypass, involving 84 and 110 patients, respectively. The median average follow-up for PICA-PICA bypass was 8 months (2-50.3 months), while for OA-PICA, it was 27.8 months (6-84 months). The patency rate for OA-PICA was 97% (95% confidence interval [CI]: 92%-100%) and 100% (95% CI: 95%-100%) for PICA-PICA. Complication rates were 29% (95% CI: 10%-47%) for OA-PICA and 12% (95% CI: 3%-21%) for PICA-PICA. Good clinical outcomes were observed in 71% (95% CI: 52%-90%) of OA-PICA patients and 87% (95% CI: 75%-100%) of PICA-PICA patients. Procedure-related mortality was 1% (95% CI: 0%-6%) for OA-PICA and 1% (95% CI: 0%-10%) for PICA-PICA. CONCLUSIONS: Both procedures have demonstrated promising results in efficacy and safety. PICA-PICA exhibits slightly better patency rates, better clinical outcomes, and fewer complications, but with a lack of substantial follow-up and a smaller sample size. The choice between these procedures should be based on the surgeon's expertise and the patient's anatomy.

Posterior Inferior Cerebellar Artery Aneurysm Shaped Like a "Calabash Gourd" and Mimicking a Tumor.

Posterior inferior cerebellar artery aneurysms are likely to be fusiform, yet they hardly enlarge to mimic a tumor in the posterior fossa on radiology. They constitute about 3%-4% of all cerebral aneurysms. A 65-year-old woman presented with tremor in her right upper limb for 1 year and intermittent dizziness for 8 months. Interestingly, magnetic resonance imaging revealed 2 unanimously enhanced masses like mother and daughter located in the right cerebellum hemisphere. The lesion was resected via surgery, and histopathology established the diagnosis of an aneurysm. Her tremor and dizziness subsided 3 months after the surgery, and at her 2-year follow-up she was well with no further neurologic deficits.

Flow Diversion for Treatment of Anterior Inferior Cerebellar Artery Aneurysms: Mechanism and Pitfalls from a Novel Management Strategy.

BACKGROUND: Anterior inferior cerebellar artery (AICA) aneurysms present a challenge for neurosurgeons and neurointerventionalists alike. METHODS: Cases of AICA aneurysms managed with endovascular flow diversion at our institute are reviewed with their angiographic outcomes. RESULTS: Both direct and indirect flow diversion provide complete aneurysm occlusion at follow-up. We propose a stratified method of approaching AICA aneurysms based on location, rupture status, and neck size. CONCLUSIONS: Careful evaluation of preoperative parameters is paramount in deciding between a surgical or a neuroendovascular approach. Low-profile stents in the future may assist in direct flow diversion of AICA trunk aneurysms. In addition, neurosurgeons need to be well versed in endovascular approaches.

Formation of a Large Fusiform Aneurysm near a Medullary Infarction Caused by Dissection of the Posterior Inferior Cerebellar Artery.

Infarction of the posterior inferior cerebellar artery (PICA) can lead to ischemic stroke in the lateral medullary oblongata. PICA dissection can also elicit an ischemic event in this region, but its detection on radiological images is difficult because of the small diameter of the vessel. We report a case of Wallenberg syndrome due to PICA dissection in a 48-year-old man, which was difficult to diagnose on first admission. He reported sudden onset of sensory disturbance on the right side of his face, ataxic gait, and headache. Brain magnetic resonance imaging (MRI) revealed a fresh cerebral infarct in the right lateral medulla oblongata. Magnetic resonance angiography (MRA) performed at the time of his admission showed no cerebral vessel abnormalities. An MRI study 18 months after the event revealed a fusiform aneurysm on the lateral medullary segment of the PICA, which was extremely close to the cerebral infarct. We concluded that the infarct was due to PICA dissection because of the sudden onset of symptoms and because the infarcted territory of the occluded penetrating branch of the dissecting aneurysm was consistent with Wallenberg syndrome. The aneurysm was trapped and an occipital artery-PICA bypass was placed. At the latest follow-up, 1 year after the procedure, he had no neurological symptoms. Imaging findings at the time of his first admission indicated that the PICA was intact. However, 18 months later, MRI revealed enlargement of an aneurysm at the site of the dissection. A cerebral infarct with headache may indicate PICA dissection.

Preserving the cerebellar hemispheric tentorial bridging veins through a novel tentorial cut technique for supracerebellar approaches.

OBJECTIVE: The objective of this study was to describe the distribution pattern of cerebellar hemispheric tentorial bridging (CHTB) veins on the tentorial surface in a case series of perimedian or paramedian supracerebellar approaches and to describe a novel technique to preserve these veins. METHODS: A series of 141 patients with various pathological processes in different locations was operated on via perimedian or paramedian supracerebellar approaches by the senior author from July 2006 through October 2022 and was retrospectively evaluated. During surgery, the number and locations of all CHTB veins were recorded to establish a distribution map on the tentorial surface, divided into nine zones. Patients were classified into four groups according to the surgical technique used to manage CHTB veins: 1) group 1 consisted of CHTB veins preserved without intervention during surgery or no CHTB veins found in the surgical route; 2) group 2 included CHTB veins coagulated during surgery; 3) group 3 included CHTB veins preserved with arachnoid and/or tentorial dissection from the cerebellar or tentorial surface, respectively; and 4) group 4 comprised CHTB veins preserved using a novel tentorial cut technique. RESULTS: Overall, 141 patients were included in the study. Of these 141 patients, 38 were in group 1 (27%), 32 in group 2 (22.7%), 47 in group 3 (33.3%), and 24 in group 4 (17%). The total number of CHTB veins encountered was 207 during surgeries on one side. According to the distribution zones of the tentorium, zone 5 had the highest density of CHTB veins, while zone 7 had the lowest. Of the patients in group 4, 6 underwent the perimedian supracerebellar approach and 18 had the paramedian supracerebellar approach. There were 39 CHTB veins on the surface of the 24 cerebellar hemispheres in group 4. The tentorial cut technique was performed for 27 of 39 CHTB veins. Twelve veins were not addressed because they did not present any obstacles during approaches. During surgery, no complications were observed due to the tentorial cut technique. CONCLUSIONS: Because there is no way to determine whether a CHTB vein can be sacrificed without complications, it is important to protect these veins in supracerebellar approaches. This new tentorial cut technique in perimedian or paramedian supracerebellar approaches makes it possible to preserve CHTB veins encountered during supracerebellar surgeries.

Bypass Surgery for Vertebral Artery and Posterior Inferior Cerebellar Artery Fusiform Aneurysms: Surgical Technique and Key Lessons.

Fusiform vertebral artery (VA) aneurysms are challenging to treat due to their pathophysiology, morphology, and anatomic location.1,2 Endovascular treatments are considered to be a widely adopted safe option for this pathology.1 Open microsurgical treatment is considered for complex anatomy, important branch involvement, poor collateral flow, or failed endovascular therapy.3-7 This report aims to show the flow-replacement strategy and bypass technique for a VA aneurysm with complex anatomy and branch involvement. A 24-year-old man presented to our clinic with a bilateral fusiform VA aneurysm discovered during workup of progressive headaches. Further investigation revealed that the left-side aneurysm was mostly thrombosed and the posterior inferior cerebellar artery arose from the aneurysm dome with a fusiform enlargement within a few millimeters from the branching point. After evaluating all management options, the patient decided on surgical treatment of the left VA aneurysm. We performed an occipital artery to posterior inferior cerebellar artery end-to-side anastomosis distal to the fusiform enlargement, followed by trapping of the aneurysm and dome resection (Video 1). Antegrade flow to the distal VA was reestablished using a radial artery interposition graft, thus preventing any flow alterations that may cause growth or rupture of the contralateral aneurysm caused by increased hemodynamic stress if the ipsilateral VA flow is not preserved.8 After in-hospital physical rehabilitation, the patient was discharged with a modified Rankin Scale score of 1. The contralateral aneurysm is managed with serial imaging and treatment will ensue if there is clinical-radiologic evolution. The patient consented to the procedure and publication of his image.

Endoscopic endonasal transclival clipping of a cerebellar arteriovenous malformation feeding vessel and associated aneurysm; a 2D operative video.

Positioned along the ventral surface of the pons, proximal superior cerebellar artery (SCA) aneurysms account for only 1.7% of all intracranial aneurysms [1]. Unlike more commonly encountered basilar artery aneurysms, patients often experience good outcomes when treated via endovascular coiling or surgical clipping [1,2]. These lesions frequently have a lateral projection and paucity of perforator arteries [2]. With further development of endoscopic endonasal techniques, access to this region is possible via a direct frontal exposure to the ventral brainstem, basilar artery and branching vessels. To date, there are only a limited number of reports describing an endoscopic endonasal transclival (EETC) approach for surgical clipping [3-5]. In this operative video, we detail the surgical clipping of a cerebellar arteriovenous malformation feeding vessel and an associated aneurysm using the EETC approach in a 59-year-old woman who presented with sudden onset of a severe headache. The feeding vessel and aneurysm's midline location, just below the take-off of the SCA made it a good candidate for this surgery. Major steps included in this video include 1) transsphenoidal exposure of and subsequent drilling of the clivus, 2) dural opening into the pre-pontine cistern and dissection of the aneurysm, 3) clipping of the aneurysm, and 4) multi-layered closure of the skull base defect. Overall, the patient tolerated the procedure well and was found to have no residual filling of the aneurysm or the AVM feeding vessel at 2-year follow-up. EETC is a viable surgical option for the treatment of aneurysm located along the midline of the pre-pontine cistern.

Ring-shaped Dandy's superior petrosal vein.

BACKGROUND: Dandy's superior petrosal vein (SPV) anatomy is highly relevant for neurosurgeons. The SPV drains into the superior petrosal sinus (SPS), closely related to the trigeminal and internal auditory pores. METHOD: The archived enhanced MRI files of a male patient were studied. RESULTS: An infratentorial ring-shaped (RS) SPV was found on the petrosal surface of the right cerebellar hemisphere. It was inserted in the SPS above the internal auditory pore, postero-lateral to the trigeminal pore. The anterior arm of that venous ring received a delicate supratrigeminal plexus of veins from the pontine surface and continued as a single venous trunk on the cerebellar surface. CONCLUSION: Such previously unreported RS-SPV is of utmost importance to be identified before subtemporal transtentorial and retrosigmoid approaches for different neurosurgical reasons.

Use of Proximal Suboccipital Segment of Occipital Artery as Donor for Posterior Circulation Revascularization Surgery: Technical Note.

BACKGROUND: The distal suboccipital segment of the occipital artery is commonly used as a donor vessel for aneurysms of the posterior circulation requiring revascularization techniques. Isolating this segment of vessel can be challenging due to its course in and out of the various layers of the suboccipital musculature. METHODS: We describe the use of the proximal suboccipital segment of the occipital artery within the occipital groove at the lateral skull base as a donor segment for an interposition graft in revascularization surgery. We present a case detailing the use of this technique for treatment of a dissecting PICA aneurysm and photographs from cadaveric dissections demonstrating relevant anatomy. RESULTS: Our patient is a 62-year-old man who presented with a high-grade subarachnoid hemorrhage from a proximal dissecting-type aneurysm of the posterior inferior cerebellar artery (PICA). Endovascular options were limited to coil sacrifice of the parent vessel, and thus the patient was taken for a far lateral craniotomy, trapping of the aneurysm, and revascularization of the PICA territory via a saphenous vein interposition graft sewn proximally and distally to the occipital artery within the occipital groove and a cortical segment of the affected PICA, respectively. Postoperative imaging demonstrated filling of the PICA territory via the graft, and the patient ultimately recovered from his subarachnoid hemorrhage. CONCLUSIONS: The use of the proximal suboccipital segment of the occipital artery is a viable option for a donor in posterior fossa revascularization surgery.

Bilateral duplicated hypoplastic superior cerebellar arteries one of which originates from a full-type fetal posterior cerebral artery.

PURPOSE: The association of bilateral duplication of the superior cerebellar artery with an origin from the posterior cerebral artery is rare but of great interest to anatomists, radiologists, and surgeons. This article reports bilateral duplicated hypoplastic superior cerebellar arteries, one of which arises from a full-type fetal cerebral artery. MATERIAL AND METHOD: A 59-year-old woman admitted to the neurosurgery department for a subarachnoid hemorrhage underwent a brain CTA with 3D reconstruction using «3D slicer 4.11¼ software. Brain CTA and the 3D model were used to analyze the configuration of the posterior circulation. RESULTS: CTA images and the 3D model showed an unusual configuration of the posterior circulation. The basilar artery prolonged the left vertebral artery, while the right vertebral artery ended in the right posterior inferior cerebellar artery. On both sides, a full-type fetal posterior cerebral artery and duplicated hypoplastic superior cerebellar artery were observed. Three cerebellar arteries arose from the basilar artery, while the fourth one emerged from the right fetal posterior cerebral artery. CONCLUSION: Knowledge of such a configuration of the posterior circulation and others is necessary before radiological and surgical procedures. It helps to understand hemodynamic events, and neurovascular conflicts, improve revascularization procedures, and avoid surgical arterial and nervous injuries.

Medullary branches of the vertebral artery: microsurgical anatomy and clinical significance.

BACKGROUND: Since the medullary arteries are of a great neurologic and neurosurgical significance, the aim was to perform a detailed microanatomic study of these vessels, as well as of the medullary infarctions in a group of patients. METHODS: The arteries of 26 halves of the brain stem were injected with India ink and gelatin, microdissected and measured with an ocular micrometer. Neurologic and magnetic resonance imaging (MRI) examinations were performed in 11 patients. RESULTS: The perforating medullary arteries, averaging 6.7 in number and 0.26 mm in diameter, most often originated from the anterior spinal artery (ASA), and rarely from the vertebral (VA) (38.5%) and the basilar artery (BA) (11.6%). They supplied the medial medullary region. The anterolateral arteries, 4.8 in number and 0.2 mm in size, most often arose from the ASA and PerfAs, and nourished the anterolateral region. The lateral arteries, 2.2 in number and 0.31 mm in diameter, usually originated from the VA and the posterior inferior cerebellar artery (PICA). They supplied the lateral medullary region. The dorsal arteries, which mainly arose from the PICA and the posterior spinal artery (PSA), nourished the dorsal region, including the roof of the 4th ventricle. The anastomotic channels, averaging 0.3 mm in size, were noted in 42.3%. Among the medullary infarctions, the lateral ones were most frequently present (72.8%). CONCLUSION: The obtained anatomic data, which can explain the medullary infarctions symptomatology, are also important in order to avoid damage to the medullary arteries during neurosurgical and neuroradiologic interventions.

Microsurgical anatomical vascular study of the PICA-PICA bypass.

OBJECTIVE: To assess the posterior inferior cerebellar artery (PICA)-PICA bypass possibility. METHODS: Fifteen adult cadaver heads were used for surgical simulation, and the far-lateral approach was used to expose the surgical field. The bilateral PICA course, diameter, and perforators were observed and measured to evaluate the possibility of a PICA-PICA bypass. RESULTS: The PICA-PICA bypass was performed in seven (46.7 %) of the 15 specimens; the procedure was performed easily in three specimens, a little difficult in two, and was difficult in two specimens because of the relationship between the tonsil and the short parallel length of the bilateral tonsillomedullary (p3) segment. In eight (53.3 %) of the 15 specimens, PICA-PICA bypass was not feasible for reasons including 1) the caliber of the bilateral p3 was unmatched for bypass, 2) the distance of bilateral p3 in the midline was > 7 mm, 3) the middle segment of p3 perforating direct arteries limited the buffer length, and 4) single caudal loops. CONCLUSION: The possibility of PICA-PICA bypass was determined by the proximity of the bilateral p3, caliber match, and mobilization of the bilateral caudal loop due to the perforators. The difficulty of the PICA-PICA bypass mainly depends on the relationship between the cerebellar tonsil and the parallel length of the bilateral PICA in the midline.

Occipital artery-posterior inferior cerebellar artery bypass: a cadaveric feasibility study.

PURPOSE: To demonstrate that occipital artery (OA)-p1 posterior inferior cerebellar artery (PICA) bypass can be an alternative for complex posterior circulation aneurysms. METHODS: A far-lateral approach to craniotomy was performed on 20 cadaveric specimens, and the OA was obtained 'in-line.' Its length, diameter, and the number of p1/p2 and p3 segmental perforators were determined, and the relationship between the caudal loop and cerebellar tonsil position was also assessed. The distance between the PICA's origin and the cranial nerve XI (CN XI), the buffer length above the CN XI after dissection, the OA length required to complete the OA-p1/p3 PICA bypass, and the p1 and p3 segment diameters were all measured. A bypass training practical scale (TSIO) was used to evaluate the quality of the anastomosis. RESULTS: All specimens underwent OA-p1 PICA end-to-end bypass and had favorable results for the TSIO score, 15 sides underwent OA-p3 PICA end-to-side bypass, and the other bypass protocols were less common. The buffer length above the CN XI after dissection, the distance between the PICA's origin and the CN XI, and the first perforator were all of sufficient length. The direct length of the OA needed to complete the OA-p1 PICA end-to-end bypass was significantly less than the available length and the OA-p3 PICA end-to-side bypass, with the OA matching the p1 segment diameter. The number of p1 perforators was less than that of p3, and the OA diameter was equal to that of the p1 segment. CONCLUSION: OA-p1 PICA end-to-end bypass is a feasible alternative in cases in which p3 segment has high caudal loops or anatomic anomalies.

A posterior inferior cerebellar artery of C2 transverse foramen level origin that entered the spinal canal via the C1/2 intervertebral space demonstrated by computed tomography angiography.

PURPOSE: To describe a case of a posterior inferior cerebellar artery (PICA) of C2 transverse foramen level vertebral artery (VA) origin that entered the spinal canal via the C1/2 intervertebral space. CASE REPORT: A 48-year-old man with posterior neck pain underwent computed tomography (CT) angiography and selective left vertebral angiography. Arterial dissection was found at the distal V2 segment of the left VA on subtracted CT angiography. The left PICA arising from the VA at the level of C2 transverse foramen was identified on CT angiography with bone imaging. This PICA of extracranial origin entered the spinal canal via the C1/2 intervertebral space, just like a PICA of C1/2 level origin. DISCUSSION: The origins of PICAs show several variations. PICAs originating at the extracranial C1/2 level VA are relatively rare, with a reported prevalence of approximately 1%. Our patient had a left PICA arising from the VA at the level of the C2 transverse foramen. No similar cases have been reported in the relevant English-language literature. We speculated that the proximal short segment of the PICA arising from the C1/2 level VA regressed incidentally and that the distal segment of the PICA was supplied by the muscular branch of the VA arising from the level of the C2 transverse foramen. CONCLUSION: We reported the first case of PICA arising from the C2 transverse foramen level VA. CT angiography with bone imaging is useful for identifying a PICA arising from the extracranial VA.