Vertebral artery-posterior inferior cerebellar artery bypass using a radial artery graft for hemorrhagic dissecting vertebral artery aneurysms: surgical technique and report of 2 cases

Vascular reconstruction related to the extracranial vertebral artery: the presentation of the concept and the basis for the establishment of the bypass system

The intracranial vertebrobasilar artery system has a unique hemodynamic pattern (vessel trunk converged bilateral flow with three groups of perforators directly arising from it), is embedded within intense osseous constraints, and is located far from conventional donor vessels. Two major traditional modalities of posterior circulation revascularization encompass the superficial temporal artery to the superior cerebellar artery and the occipital artery to the posteroinferior cerebellar artery anastomosis, which are extracranial-intracranial low-flow bypass with donor arteries belonging to the anterior circulation and mainly supply focal perforators and distal vascular territories. As our understanding of flow hemodynamics has improved, the extracranial vertebral artery-related bypass has further evolved to improve the cerebral revascularization system. In this article, we propose the concept of "vascular reconstruction related to the extracranial vertebral artery" and review the design philosophy of the available innovative modalities in the respective segments. V1 transposition overcomes the issue of high rates of in-stent restenosis and provides a durable complementary alternative to endovascular treatment. V2 bypass serves as an extracranial communication pathway between the anterior and posterior circulation, providing the advantages of high-flow, short interposition grafts, orthograde flow in the vertebrobasilar system, and avoiding complex skull base manipulation. V3 bypass is characterized by profound and simultaneous vascular reconstruction of the posterior circulation, which is achieved by intracranial-intracranial or multiple bypasses in conjunction with skull base techniques. These posterior circulation vessels not only play a pivotal role in the bypass modalities designed for vertebrobasilar lesions but can also be implemented to revascularize the anterior circulation, thereby becoming a systematic methodology.

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.

Case Report: Curative effect of OA-PICA protected bypass in severe PICA-complicated vertebral artery stenosis treatment: Results in 3 cases

Objectives

We aimed to explore the results of OA-PICA-protected bypass grafting in patients with severe stenosis of the vertebral artery combined with PICA.

Methods

Three patients with vertebral artery stenosis involving the posterior inferior cerebellar artery, treated by the Department of Neurosurgery of Henan Provincial People's Hospital from January 2018 to December 2021, were retrospectively analyzed. All the patients underwent Occipital Artery-Posterior Inferior Cerebellar Artery (OA-PICA) bypass surgery followed by elective vertebral artery stenting. Intraoperative indocyanine green fluorescence angiography (ICGA) showed patency of the bridge-vessel anastomosis. Postoperatively, the ANSYS software was used to assess the flow pressure changes and vascular shear in combination with the reviewed DSA angiogram. CTA or DSA was reviewed 1-2 years postoperatively, and the prognosis was evaluated by the modified Rankin Scale (mRS) one year postoperatively.

Results

OA-PICA bypass surgery was completed in all patients, with intraoperative ICGA showing a patent bridge anastomosis, followed by stenting of the vertebral artery, and a review of the DSA angiogram. We also employed ANSYS software evaluation of the bypass vessel, which showed stable pressure and low turnover angle, suggesting a low rate of long-term occlusion of the vessel. All patients had no procedure-related complications during their hospitalization, and were followed up for a mean of 24 months postoperatively, with a good prognosis (mRS score of 1) at 1 year postoperatively.

Conclusion

OA-PICA-protected bypass grafting is an effective treatment for patients with severe stenosis of the vertebral artery combined with PICA.

Microsurgical treatment of posterior inferior cerebellar aneurysms based on angioarchitecture supplemented by high-resolution vessel wall MRI: a case series report

BACKGROUND

Surgical treatment of posterior inferior cerebellar artery (PICA) aneurysms is challenging because many are nonsaccular and atherosclerotic. We report our tailored approach to PICA aneurysms, which is based on angioarchitecture supplemented by high-resolution vessel wall MRI (HR-VW MRI) findings.

METHODS

From March 2010 to September 2020, 27 patients with 29 PICA aneurysms underwent surgical treatment in our institution. Since October 2016, HR-VW MRI has been used for aneurysmal wall assessment. Clinical characteristics, radiological data and surgical outcomes were analysed.

RESULTS

Nineteen proximal PICA aneurysms (vertebral artery (VA), P1, P2 and P3) were treated using the far-lateral approach. Ten distal PICA aneurysms (P4, P5) were treated using the suboccipital midline approach. Direct clipping or clip reconstruction was achieved in 19 aneurysms. Ten were trapped in conjunction with extracranial-intracranial or intracranial-intracranial bypass, including three occipital artery-PICA reimplantations, three PICA-VA reimplantations, two PICA-PICA side-to-side anastomoses, one PICA-PICA reimplantation and one PICA-PICA reanastomosis. All aneurysms were eventually completely obliterated and all bypasses remained patent. At the last follow-up, 26 patients (96.2%) achieved a good outcome (modified Rankin Scale score <3). Eight patients underwent HR-VW MRI. Among these, the six aneurysms with focal wall enhancement required bypass and the two with negative enhancement were successfully clipped.

CONCLUSION

PICA aneurysms have a higher frequency of complex features such as large or giant size and fusiform or dissecting morphology. Favourable outcomes were achieved with individualised microsurgical strategies based on angioarchitecture. HR-VW MRI may be used as a promising technique to predict aneurysmal atherosclerosis.

Microsurgical treatment of posterior inferior cerebellar aneurysms based on angioarchitecture supplemented by high-resolution vessel wall MRI: a case series report

BACKGROUND

Surgical treatment of posterior inferior cerebellar artery (PICA) aneurysms is challenging because many are nonsaccular and atherosclerotic. We report our tailored approach to PICA aneurysms, which is based on angioarchitecture supplemented by high-resolution vessel wall MRI (HR-VW MRI) findings.

METHODS

From March 2010 to September 2020, 27 patients with 29 PICA aneurysms underwent surgical treatment in our institution. Since October 2016, HR-VW MRI has been used for aneurysmal wall assessment. Clinical characteristics, radiological data and surgical outcomes were analysed.

RESULTS

Nineteen proximal PICA aneurysms (vertebral artery (VA), P1, P2 and P3) were treated using the far-lateral approach. Ten distal PICA aneurysms (P4, P5) were treated using the suboccipital midline approach. Direct clipping or clip reconstruction was achieved in 19 aneurysms. Ten were trapped in conjunction with extracranial-intracranial or intracranial-intracranial bypass, including three occipital artery-PICA reimplantations, three PICA-VA reimplantations, two PICA-PICA side-to-side anastomoses, one PICA-PICA reimplantation and one PICA-PICA reanastomosis. All aneurysms were eventually completely obliterated and all bypasses remained patent. At the last follow-up, 26 patients (96.2%) achieved a good outcome (modified Rankin Scale score <3). Eight patients underwent HR-VW MRI. Among these, the six aneurysms with focal wall enhancement required bypass and the two with negative enhancement were successfully clipped.

CONCLUSION

PICA aneurysms have a higher frequency of complex features such as large or giant size and fusiform or dissecting morphology. Favourable outcomes were achieved with individualised microsurgical strategies based on angioarchitecture. HR-VW MRI may be used as a promising technique to predict aneurysmal atherosclerosis.

Bypass Surgery Management of Complex Proximal and Distal Posterior Inferior Cerebellar Artery Aneurysms

BACKGROUND

For the complex posterior inferior cerebellar artery (PICA) aneurysms, standard microsurgical or endovascular technical options were not feasible. To determine the efficacy and outcomes of bypass surgery for complex PICA aneurysms, the authors herein review our recent surgical experience for complex PICA aneurysms.

METHODS

The authors retrospectively reviewed our experience of extracranial-intracranial bypass and intracranial-intracranial bypass surgery in treatment of proximal and distal complex PICA aneurysms at our institution from 2016 to 2020.

RESULTS

Twelve patients harboring 12 complex PICA aneurysms received bypass surgery at our institution. Seven (58.3%) patients with proximal PICA aneurysms underwent extracranial-intracranial bypass. Five (41.7%) patients with distal PICA aneurysms accepted intracranial-intracranial bypass. The postoperative symptom improvement: Of the 6 patients with preoperative hypoperfusion or ischemic of the cerebellar hemisphere, the symptom resolved in 5 patients, improved in 1 patient, of 5 patients with preoperative mass effect, the symptom resolved in 5 patients. During the follow-up period, ten patients had a modified Rankin scale (mRS) score of 0 to 1, and 1 patient had an mRS score of 2. One patient had an mRS score of 3. The long-term graft patency rate was 91.7%. All patients had no recurrence of intracranial aneurysm.

CONCLUSIONS

Base on the complexity of anatomy structure and the vascular architecture, an individualized strategy was proposed for each patient. The use of different types of bypass procedures (occipital artery-PICA end-to-end bypass, PICA-PICA end-to-end anastomosis, and/or occipital artery graft) can safely and effectively manage these complex PICA aneurysms.

A Ruptured Vertebral Artery Dissecting Aneurysm that Grew Immediately: Case Report

The etiology of the vertebral artery dissecting aneurysm (VADA) is unknown and they frequently occur in relatively healthy young men. Therefore, the pathological mechanism by which VADAs occur has not been accurately identified. In this paper, we will examine a case in which a young man complaining of a simple headache became unconscious due to the rupture of a VADA in grew immediately.

Revascularization of the Posterior Inferior Cerebellar Artery Using the Occipital Artery: A Cadaveric Study Comparing the p3 and p1 Recipient Sites

BACKGROUND

Revascularization of the posterior inferior cerebellar artery (PICA) is typically performed with the occipital artery (OA) as an extracranial donor. The p3 segment is the most accessible recipient site for OA-PICA bypass at its caudal loop inferior to the cerebellar tonsil, but this site may be absent or hidden due to a high-riding location.

OBJECTIVE

To test our hypothesis that freeing p1 PICA from its origin, transposing the recipient into a shallower position, and performing OA-p1 PICA bypass with an end-to-end anastomosis would facilitate this bypass.

METHODS

The OA was harvested, and a far lateral craniotomy was performed in 16 cadaveric specimens. PICA caliber and number of perforators were measured at p1 and p3 segments. OA-p3 PICA end-to-side and OA-p1 PICA end-to-end bypasses were compared.

RESULTS

OA-p1 PICA bypass with end-to-end anastomosis was performed in 16 specimens; whereas, OA-p3 PICA bypass with end-to-side anastomosis was performed in 11. Mean distance from OA at the occipital groove to the anastomosis site was shorter for p1 than p3 segments (30.2 vs 48.5 mm; P < .001). Median number of perforators on p1 was 1, and on p3, it was 4 (P < .001).

CONCLUSION

Although most OA-PICA bypasses can be performed using the p3 segment as the recipient site for an end-to-side anastomosis, a more feasible alternative to conventional OA-p3 PICA bypass in cases of high-riding caudal loops or aberrant anatomy is to free the p1 PICA, transpose it away from the lower cranial nerves, and perform an end-to-end OA-p1 PICA bypass instead.

Clinical Importance of the Posterior Inferior Cerebellar Artery: A Review of the Literature

The posterior inferior cerebellar artery (PICA), with its unique anatomical complexity, is of great clinical importance and involved in many diseases including aneurysm, ischemic stroke, neurovascular compression syndrome (NVCS), arteriovenous malformation (AVM), and brain tumor. However, a comprehensive systematic review of the importance of the PICA is currently lacking. In this study, we perform a literature review of PICA by searching all the associated papers in the PUBMED database hoping to provide a better understanding of the artery. The PICA has tortuous and variable course and territory, divided into 5 segments. Various aneurysms involving PICA were not uncommon, of which the treatment is challenging. The PICA infarct typically manifests lateral medullary syndrome (LMS) and is more likely to cause mass effects. The PICA frequently compresses the medulla and the cranial nerves resulting in various neurovascular compression syndromes (NVCS). Arteriovenous malformation (AVM) fed by PICA are associated with aneurysm and dissection which have high risk of rupture and worse outcome. PICA injured by head trauma can cause fatal SAH. VA terminating in PICA probably cause Bow hunter's syndrome (BHS). The PICA supplies many brain tumors and can be used in intracerebellar chemotherapy. The PICA can be exposed and injured during surgeries especially in telovelar approach, and it also plays an important role in bypass surgeries, hinting the surgical importance of PICA. In conclusion, PICA is very important in clinical practice.

Endovascular treatment of vertebral artery dissecting aneurysm: A single-center experience

The aim of the present study was to explore the optimal treatment strategy for patients with vertebral artery dissecting aneurysms via the endovascular approach. A total of 47 patients (50 aneurysms, including 28 ruptured and 22 unruptured) underwent endovascular treatment between January 2012 and March 2018. Of these aneurysms, 18 were treated by parent artery occlusion, 11 by stent implantation and 21 by stent-assisted coiling. The complete occlusion rate was 100% (18/18) in aneurysms treated by parent artery occlusion and 46.9% (15/32) for stent implantation with or without coiling. External drainage was performed in 8 patients with ruptured aneurysms. Post-operative bleeding occurred in 2 patients treated by stent-assisted coiling. Ventriculo-peritoneal shunt was performed in 4 patients due to delayed hydrocephalus. Post-operative frontal hematoma occurred in one patient treated by stent-assisted coiling. The mortality was 6.4% (3/47) prior to discharge. The recurrence rate was 8.3% (1/12) in aneurysms treated by parent artery occlusion and 13.6% (3/22) in those treated by stent implantation with or without coiling. A total of 39 patients were followed up for 14.56±14.91 months. The good outcome rates were 100% (28/28) in patients with unruptured aneurysms and a Hunt-Hess grade of 1–3, and 72.7% (8/11) in patients with a Hunt-Hess grade of 4 or 5. In conclusion, the present study indicated that endovascular treatment is a safe and efficient method for patients with vertebral artery aneurysm. The treatment strategy should be based on the patient's condition and aneurysmal characteristics. Parent artery occlusion may be suitable for selected patients with ruptured vertebral artery aneurysms.

Surgical microanatomy of the occipital artery for suboccipital muscle dissection and intracranial artery reconstruction

Background:

The occipital artery (OA) is an important donor artery for posterior fossa revascularization. Harvesting the OA is difficult in comparison to the superficial temporal artery because the OA runs between suboccipital muscles. Anatomical knowledge of the suboccipital muscles and OA is essential for harvesting the OA during elevation of the splenius capitis muscle (SPL) for reconstruction of the posterior inferior cerebellar artery. We analyzed the running pattern of the OA and its anatomic variations using preoperative and intraoperative findings.

Methods:

From April 2012 to March 2018, we surgically treated 162 patients with suboccipital muscle dissection by OA dissection using the lateral suboccipital approach. The running pattern and relationship between the suboccipital muscles and OA were retrospectively analyzed using the operation video and preoperative enhanced computed tomography (CT) images. The anatomic variation in the running pattern of the OA was classified into two types: lateral type, running lateral to the muscle and medial type, running medial to the longissimus capitis muscle (LNG).

Results:

The medial pattern was observed in 107 (66%) patients and the lateral pattern in 54 (33.3%); 1 (0.6%) patient had the OA running between the LNGs.

Conclusion:

Preoperative CT is effective in determining the running course of the OA, which is important for safely harvesting the OA during SPL elevation. There is a risk of causing OA injury in patients with the lateral pattern. This is the first report showing that the OA rarely runs in between the LNGs.

Treatment of intracranial vertebral artery dissecting aneurysms involving the posterior inferior cerebellar artery origin

Background

Vertebral artery dissecting aneurysm (VADA) involving the origin of the posterior inferior cerebellar artery (PICA) is a complex disease entity in which the dual goals of preventing future rebleeding and maintaining perfusion of the lateral medulla must be considered. We present an illustrative case and review the literature surrounding treatment strategies.

Case Description

We report a patient presenting with extensive subarachnoid hemorrhage due to rupture of an intracranial VADA involving the PICA origin. After consideration of the patient's cerebral vasculature and robustness of collaterals, a flow-diverting stent was placed with angiographic resolution of the lesion and maintenance of antegrade PICA flow. Ultimately, the patient experienced a contralateral intraparenchymal hemorrhage leading to death. Review of the literature identified 124 cases of VADA involving the PICA origin described over the past decade. The methods of surgical and endovascular treatment of these cases were reviewed, with particular focus on the rationale of treatment, outcomes, and complications.

Conclusion

Numerous treatment options for VADA involving PICA have been reported with different risk and benefit profiles. Flow-diverting stents appear to offer the most favorable balance of securing the aneurysm and avoiding medullary infarction, but the risks and optimal anti-thrombotic treatment strategy are incompletely understood. In select cases, in which the surgical risk is low or in which the anatomy is favorable (e.g., nondominant parent vessel or robust collateral circulation in the involved territories), parent artery trapping with or without microsurgical revascularization can be considered.

National trends in cerebral bypass for unruptured intracranial aneurysms: a National (Nationwide) Inpatient Sample analysis of 1998–2015

OBJECTIVE

The development and recent widespread dissemination of flow diverters may have reduced the utilization of surgical bypass procedures to treat complex or giant unruptured intracranial aneurysms (UIAs). The aim of this retrospective cohort study was to observe trends in cerebral revascularization procedures for UIAs in the United States before and after the introduction of flow diverters by using the National (Nationwide) Inpatient Sample (NIS).

METHODS

The authors extracted data from the NIS database for the years 1998–2015 using the ICD-9/10 diagnostic and procedure codes. Patients with a primary diagnosis of UIA with a concurrent bypass procedure were included in the study. Outcomes and hospital charges were analyzed.

RESULTS

A total of 216,212 patients had a primary diagnosis of UIA during the study period. The number of patients diagnosed with a UIA increased by 128% from 1998 (n = 7718) to 2015 (n = 17,600). Only 1328 of the UIA patients (0.6%) underwent cerebral bypass. The percentage of patients who underwent bypass in the flow diverter era (2010–2015) remained stable at 0.4%. Most patients who underwent bypass were white (51%), were female (62%), had a median household income in the 3rd or 4th quartiles (57%), and had private insurance (51%). The West (33%) and Midwest/North Central regions (30%) had the highest volume of bypasses, whereas the Northeast region had the lowest (15%). Compared to the period 1998–2011, bypass procedures for UIAs in 2012–2015 shifted entirely to urban teaching hospitals (100%) and to an elective basis (77%). The median hospital stay (9 vs 3 days, p < 0.0001), median hospital charges ($186,746 vs $66,361, p < 0.0001), and rate of any complication (51% vs 17%, p < 0.0001) were approximately threefold higher for the UIA patients with bypass than for those without bypass.

CONCLUSIONS

Despite a significant increase in the diagnosis of UIAs over the 17-year study period, the proportion of bypass procedures performed as part of their treatment has remained stable. Therefore, advances in endovascular aneurysm therapy do not appear to have affected the volume of bypass procedures performed in the UIA population. The authors’ findings suggest a potentially ongoing niche for bypass procedures in the contemporary treatment of UIAs.

Descending Branch of the Lateral Circumflex Femoral Artery Graft for Posterior Inferior Cerebellar Artery Revascularization

BACKGROUND

Posterior inferior cerebellar artery (PICA) revascularization can be achieved with relative ease when a contralateral PICA is present. However, without a contralateral PICA, identification of a suitable vessel alternative can be challenging due to a size mismatch.

OBJECTIVE

To propose the descending branch of the lateral circumflex femoral artery (DLCFA) to be an acceptable, if not preferred, arterial graft for PICA revascularization.

METHODS

Data from patients who underwent PICA revascularization with DLCFA grafts were obtained from an institutional review board-approved prospectively maintained database with informed consent from the patients.

RESULTS

Three patients, all presenting with ruptured aneurysms, were treated with PICA revascularization using the DLCFA. All cases achieved bypass patency and no ischemic events occurred during the bypass procedures. Graft spasm occurred in 2 patients. Two patients that presented with neurological deficits achieved excellent neurological outcomes and 1 suffered an anterior spinal artery stroke during a repeat endovascular treatment 1 wk after revascularization.

CONCLUSION

The DLCFA is favorable for PICA revascularization when a contralateral PICA is not a viable option.

Flow Alteration Therapy for Ruptured Vertebral Artery Dissecting Aneurysms Involving the Posterior Inferior Cerebellar Artery

Surgery for- and endovascular treatment of vertebral artery (VA) dissecting aneurysms involving the origin of the posterior inferior cerebellar artery (PICA) remain challenging. Their ideal treatment is complete isolation of the aneurysm by surgical or endovascular trapping plus PICA reconstruction. However, postoperative lower cranial nerve palsy and medullary infarction are potential complications. We report four patients with VA dissecting aneurysms involving the PICA origin who were treated by occipital artery (OA)-PICA bypass followed by proximal occlusion of the VA and clip ligation of the PICA origin instead of trapping. There were no procedural or ischemic complications. In all patients, angiography performed 2–3 weeks later showed good patency of the bypass graft and complete obliteration of the aneurysm. During the follow-up period ranging from 1 to 14 years, none experienced bleeding. Although retrograde blood flow to the dissecting aneurysm persisted in the absence of trapping, iatrogenic lower cranial nerve injury could be avoided. The decrease in aneurysmal flow might elicit spontaneous thrombosis and prevent aneurysmal rerupture. Our technique might be less invasive than aneurysmal trapping and help to prevent rebleeding.

The V3 segment of the vertebral artery as a robust donor for intracranial-to-intracranial interpositional bypasses: technique and application in 5 patients

The V₃ segment of the vertebral artery (VA) has been studied in various clinical scenarios, such as in tumors of the craniovertebral junction and dissecting aneurysms. However, its use as a donor artery in cerebral revascularization procedures has not been extensively studied. In this report, the authors summarize their clinical experience in cerebral revascularization procedures using the V₃ segment as a donor. A brief anatomical description of the relevant techniques is also provided.

Ruptured intracranial vertebral artery dissecting aneurysms: An evaluation of prognostic factors of treatment outcome

Objective Intracranial spontaneous vertebral artery dissecting aneurysms commonly occur in the third to fifth decades of life, and are mostly associated with hypertension. Patients present with intracranial haemorrhage or thromboembolic events. Patients who present with intracranial haemorrhage carry about a 70% risk of recurrent bleeding. Patients with a posterior-inferior cerebellar artery (PICA) or ipsilateral dominant vertebral artery involve selecting which parent vessel could not be sacrificed. Recent reconstructive techniques such as stent-assisted coiling embolisation and flow-diverting stents are effective treatments of choice. Methods Seventeen patients presented subarachnoid haemorrhage and nine patients with other symptoms. Sacrificing the parent vertebral artery was the first choice for surgical or endovascular methods. Endovascular reconstructive treatment by stent-assisted coiling embolisation was indicated in dissecting vertebral artery aneurysms with ipsilateral dominant vertebral artery or PICA involvement. Clinical outcomes were determined using the modified Rankin Score (mRS) at 90 days, with favourable outcomes defined as 0 to 2. Results Of the patients presenting with ruptured aneurysms, 11 (61.1%) had a good clinical outcome, with a mRS of 0-2. Favourable Hunt and Hess grading (65%), mild to moderate GCS (65%) and total occlusion of aneurysms after treatment (65%) were significantly good prognostic factors in patients with ruptured vertebral artery dissecting aneurysms. Conclusion Endovascular parent vessel sacrifice could be the first choice to treat a ruptured vertebral artery dissecting aneurysm. Stent-assisted coiling to preserve the patency of the parent artery and its branches is a promising treatment for vertebral artery dissections.

Early Localization of the Third Segment of the Vertebral Artery: The Atlanto-Mastoid Line

Supplemental Digital Content is Available in the Text.

BACKGROUND

The third segment of the vertebral artery (V3) is vulnerable to injury during surgical approaches to the posterolateral craniovertebral junction. Despite numerous efforts, a roadmap to localize this segment of the artery is still lacking.

OBJECTIVE

To delineate the topographic anatomy of the V3 and to facilitate a safe and fast exposure during transcranial surgical approaches to the posterior craniovertebral junction.

METHODS

The distances between the most posteriorly prominent point (bulge) of the vertebral artery and the surrounding bony and muscular landmarks were measured in 10 cadaveric heads bilaterally (20 sides). The relative position of the vertebral artery bulge projected on the atlanto-mastoid line was calculated using trigonometric equations. Two clinical vignettes were reported to provide examples of clinical application of the described technique.

RESULTS

The vertebral artery bulge was found within 10.8 mm of the atlanto-mastoid line. The projected position of the vertebral artery bulge on the atlanto-mastoid line lay within 40th and 50th percentiles of its length measured from the mastoid process in 16 (89%) specimens. The close relationship between the V3 segment and superior oblique capitis muscle makes this muscle another useful guide for localization of the V3 segment.

CONCLUSION

The atlanto-mastoid line is a reliable guide for fast and safe exposure of the vertebral artery in the suboccipital triangle. Using this clue together with the belly of the superior oblique capitis muscle can lead the surgeon to the V3 segment safely, as illustrated in the clinical vignettes.

Posterior inferior cerebellar artery reimplantation: buffer lengths, perforator anatomy, and technical limitations

OBJECTIVE

Reimplantation of the posterior inferior cerebellar artery (PICA) to the vertebral artery (VA) is a safe and effective bypass option after deliberate PICA sacrifice during the treatment of nonsaccular and dissecting aneurysms at this location. However, the anatomy and limitations of this technique have not been studied. The goal of this study was to define the surgical anatomy and buffer lengths specific to the proximal segment of the PICA related to 2 variations of PICA reimplantation: 1) reimplantation “along-VA” (simulating a dissecting VA aneurysm), and 2) reimplantation “across-VA” (simulating a nonclippable, proximal PICA aneurysm).

METHODS

Ten cadaver heads (20 sides) were prepared for surgical simulation. Twenty far-lateral approaches were performed. The PICA was mobilized and reimplanted onto the VA according to 2 different paradigms: 1) transposition along the axis of the VA (along-VA) to simulate a dissecting VA, and 2) transposition perpendicular to the axis of the VA (across-VA) to simulate a nonclippable, proximal PICA aneurysm. The buffer lengths provided by mobilization of the artery in each paradigm were measured and the anatomy of perforator branching on the proximal PICAs was analyzed.

RESULTS

The PICA was reimplanted in all surgical simulations. The most common perforating artery on the P1 and P2 segments was the short circumflex type. No direct perforator was found on the P1 segment. The mean buffer length with reimplantation along the VA axis was 13.43 ± 4.61 mm, and it was 6.97 ± 4.04 mm with reimplantation across the VA. The PICA was less maneuverable when it was reimplanted across the VA, due to perforator branches of the PICA (P3 segment).

CONCLUSIONS

The buffer lengths measured in this study describe the limitations of PICA reimplantation as a revascularization procedure for nonsaccular aneurysms in this location. PICA reimplantation is a revascularization option for dissecting VA aneurysms incorporating the PICA origin that are < 13 mm in length, and for nonsaccular proximal PICA aneurysms that are < 6 mm in diameter. The final decision to reimplant the PICA depends on careful inspection of perforator anatomy that is not visible preoperatively on angiography, as well as an assessment of technical difficulty intraoperatively.

State-of-art in surgical treatment of dissecting posterior circulation intracranial aneurysms

Vertebrobasilar (VB) intracranial dissecting aneurysms (IDAs) pose difficult therapeutic issues and are especially among the most difficult to manage surgically. There are, however, some cases where selective aneurysm obliteration by endovascular approach is impossible or is associated with an unacceptable risk of morbidity. This is particularly true when the aneurysm is dissecting, giant, or has a large neck. In such cases, surgical treatment may be the only alternative. Optimal management of these lesions is therefore challenging and treatment decisions have to be made on a case-by-case basis. Ideal treatment should be a complete surgical excision of the lesion; however, this procedure might only be possible after distal and proximal vessel wall occlusion which might not be tolerated by the patient depending on the location of the aneurysm. Therefore, formulation of recommendations concerning the surgical strategy remains still difficult due to inconsistency of surgical outcomes. The literature describing surgical strategy of VB IDAs is varying in quality and content, and many studies deal with only a few patients. In the presented review, the authors summarize the current knowledge on the incidence, pathogenesis, clinical presentation, and diagnostic procedures with special emphasis on surgical treatment of IDAs in posterior circulation.

Therapeutic Progress in Treating Vertebral Dissecting Aneurysms Involving the Posterior Inferior Cerebellar Artery

Among the variations of vertebral artery dissecting aneurysms (VDAs), VDAs involving the posterior inferior cerebellar artery (PICA), especially ruptured and high-risk unruptured aneurysms, are the most difficult to treat. Because the PICA is an important structure, serious symptoms may occur after its occlusion. Retained PICAs are prone to re-bleeding because VDAs are difficult to completely occlude. There is therefore confusion regarding the appropriate treatment for VDAs involving the PICA. Here, we used the PubMed database to review recent research concerning VDAs that involve the PICA, and we found that treatments for VDAs involving the PICA include (i) endovascular treatment involving the reconstruction of blood vessels and blood flow, (ii) occluding the aneurysm using an internal coil trapping or an assisted bypass, (iii) inducing reversed blood flow by occluding the proximal VDA or forming an assisted bypass, or (iv) the reconstruction of blood flow via a craniotomy. Although the above methods effectively treat VDAs involving the PICA, each method is associated with both a high degree of risk and specific advantages and disadvantages. The core problem when treating VDAs involving the PICA is to retain the PICA while occluding the aneurysm. Therefore, the method is generally selected on a case-by-case basis according to the characteristics of the aneurysm. In this study, we summarize the various current methods that are used to treat VDAs involving the PICA and provide schematic diagrams as our conclusion. Because there is no special field of research concerning VDAs involving the PICA, these cases are hidden within many multiple-cases studies. Therefore, this study does not review all relevant documents and may have some limitations. Thus, we have focused on the mainstream treatments for VDAs that involve the PICA.

Tailored PICA Revascularization for Unusual Ruptured Fusiform Vertebro-PICA Origin Aneurysms: Rationale and Case Illustrations

Ruptured fusiform aneurysms of the vertebral artery involving posterior inferior cerebellar artery (PICA) origin are difficult to manage without sacrificing PICA. In this report, two very unusual cases are described which highlight different revascularization strategies that may be required. The first case initially appeared to be a small saccular PICA origin aneurysm, but detailed angiography showed a serpentine recanalization of a fusiform aneurysm. This was treated with PICA-PICA anastomosis and trapping of the aneurysm. The second case is a dissecting vertebral aneurysm with both PICA and the anterior spinal artery originating from the dome. PICA was found to be a bihemispheric variant, so no in situ bypass was available, and an occipital artery to PICA bypass was performed. The vertebral artery was occluded proximally only and follow-up angiography showed remodeling of the distal vertebral artery with the anterior spinal artery filling by retrograde flow from the distal vertebral artery. These cases illustrate both the anatomic variability of this region as well as the need to be familiar with multiple treatment strategies including revascularization techniques to be able to successfully treat these aneurysms.

How I do it: occipital artery to posterior inferior cerebellar artery bypass

BACKGROUND

Aneurysms located at the proximal posterior inferior cerebellar artery (PICA) may need to be addressed by trapping and concomitant bypass. An anastomosis of the Occipital Artery (OA) to PICA is one bypass option in these cases. This bypass is highly challenging and its technical description is seldom cited in the literature.

METHODS

We describe the technical nuances of an OA-PICA end-to-side bypass in a 63-year-old man with a dissecting ruptured aneurysm of the third segment (tonsilomedullary) of the PICA.

CONCLUSION

OA-PICA bypass option should remain as a treatment modality in the armamentarium of neurovascular surgeons.

Advances in Open Microsurgery for Cerebral Aneurysms

BACKGROUND:

Endovascular techniques introduced strong extrinsic forces that provoked reactive changes in aneurysm surgery. Microsurgery has become less invasive, more appealing to patients, lower risk, and efficacious for complex aneurysms, particularly those unfavorable for or failing endovascular therapy.

OBJECTIVE:

To review specific advances in open microsurgery for aneurysms.

METHODS:

A university-based, single-surgeon practice was examined for the use of minimally invasive craniotomies, surgical management of recurrence after coiling, the use of intracranial-intracranial bypass techniques, and cerebrovascular volume-outcome relationships.

RESULTS:

The mini-pterional, lateral supraorbital, and orbital-pterional craniotomies are minimally invasive alternatives to standard craniotomies. Mini-pterional and lateral supraorbital craniotomies were used in one-fourth of unruptured patients, increasing from 22% to 28%, whereas 15% of patients underwent orbital-pterional craniotomies and trended upward from 11% to 20%. Seventy-four patients were treated for coil recurrences (2.3% of all aneurysms) with direct clip occlusion (77%), clip occlusion after coil extraction (7%), or parent artery occlusion with bypass (16%). Intracranial-intracranial bypass (in situ bypass, reimplantation, reanastomosis, and intracranial grafts) transformed the management of giant aneurysms and made the surgical treatment of posterior inferior cerebellar artery aneurysms competitive with endovascular therapy. Centralization maximized the volume-outcome relationships observed with clipping.

CONCLUSION:

Aneurysm microsurgery has embraced minimalism, tailoring the exposure to the patient's anatomy with the smallest possible craniotomy that provides adequate exposure. The development of intracranial-intracranial bypasses is an important advancement that makes microsurgery a competitive option for complex and recurrent aneurysms. Trends toward centralizing aneurysm surgery in tertiary centers optimize results achievable with open microsurgery.

Intracranial vertebral artery dissections: evolving perspectives

Intracranial vertebral artery dissection (VAD) represents the underlying etiology in a significant percentage of posterior circulation ischemic strokes and subarachnoid hemorrhages. These lesions are particularly challenging in their diagnosis, management, and in the prediction of long-term outcome. Advances in the understanding of underlying processes leading to dissection, as well as the evolution of modern imaging techniques are discussed. The data pertaining to medical management of intracranial VADs, with emphasis on anticoagulants and antiplatelet agents, is reviewed. Surgical intervention is discussed, including, the selection of operative candidates, open and endovascular procedures, and potential complications. The evolution of endovascular technology and techniques is highlighted.

Reconstructive endovascular treatment of a ruptured vertebral artery dissecting aneurysm using the Pipeline embolization device

BACKGROUND

The Pipeline embolization device has been used successfully to treat intracranial aneurysms with difficult morphologies. However, the need for dual antiplatelet therapy has limited its use after subarachnoid hemorrhage.

CASE REPORT

A 42-year-old woman with a ruptured dissecting aneurysm of her dominant vertebral artery (V4) was successfully treated by Pipeline embolization with preservation of flow through a covered posterior inferior cerebellar artery. This strategy preserved endovascular access for the treatment of severe posterior circulation vasospasm. She was a non-responder to thienopyridine agents and was thus maintained on aspirin and heparin, which was transitioned to warfarin following ventricular drain removal. The aneurysm remains angiographically obliterated at 6 months. Despite a moribund presentation and an extended hospitalization, she has made a remarkable neurological recovery.

CONCLUSIONS

Pipeline embolization may be used to treat a ruptured dissecting aneurysm in selected cases where parent vessel preservation is paramount.