History, Evolution, and Continuing Innovations of Intracranial Aneurysm Surgery

The Management of Intracranial Aneurysms: Current Trends and Future Directions

Intracranial aneurysms represent a major global health burden. Rupture of an intracranial aneurysm is a catastrophic event. Without access to treatment, the fatality rate is 50% in the first 30 days. Over the last three decades, treatment approaches for intracranial aneurysms have changed dramatically. There have been improvements in the medical management of aneurysmal subarachnoid haemorrhage, and there has been an evolution of treatment strategies. Endovascular therapy is now the mainstay of the treatment of ruptured intracranial aneurysms based on robust randomised controlled trial data. There is now an expansion of treatment indications for unruptured intracranial aneurysms to prevent rupture with both microsurgical clipping and endovascular treatment. Both microsurgical and endovascular treatment modalities have evolved, in particular with the introduction of innovative endovascular treatment options including flow diversion and intra-saccular flow disruption. These novel therapies allow clinicians to treat more complex and previously untreatable aneurysms. We aim to review the evolution of treatment strategies for intracranial aneurysms over time, and discuss emerging technologies that could further improve treatment safety and functional outcomes for patients with an intracranial aneurysm.

Correlation Between Aneurysm Dome Direction and Patient Outcomes Following Surgery for Ruptured Anterior Communicating Artery Aneurysms

Background Anterior communicating (Acom) artery aneurysms are the most common type of intracranial aneurysms. Despite the enormous advancements in the field of endovascular surgery for intracranial aneurysms, open surgical clipping of aneurysms remains the most durable management of Acom aneurysms. There have been various studies based on the clinical-radiological profile and outcome of open clipping for intracranial aneurysms, but the correlation of the direction of the aneurysm with the surgical outcome remains incompletely defined. Aim To analyze the correlation between the direction of the aneurysm dome and patient outcomes after surgery for ruptured Acom artery aneurysms. Materials and methods  CT angiography of the brain was done in all patients pre-operatively as part of the standard treatment protocol. Retrospective data was collected from an inter-departmental computerized database, which included the patient's details, history, investigations, a course in the hospital from admission to discharge, and an operative note by the surgeon. Prospective data was collected from patients with ruptured Acom artery aneurysms. We analyzed the relationship between the direction of the dome of the Acom aneurysm and preoperative, intraoperative, and postoperative variables. Results Of the 48 patients who underwent surgery for ruptured aneurysms, 34 (70.8%) were female and 14 (29.2%) were male. Among the 27 cases with anteriorly projecting aneurysms, 11 (40.7%) experienced postoperative complications. Of the five cases with posteriorly projecting aneurysms, two (40%) experienced postoperative complications. One-third of cases of the inferior dome direction and 10% of cases of the superior direction of the dome of aneurysm were also found to have postoperative complications. However, using the chi-square test, the association between postoperative complications and the direction of the aneurysm was determined to be statistically non-significant (p-value = 0.93). Conclusion The findings of our investigation indicate that aneurysms with superior projection exhibit the lowest likelihood of experiencing intraoperative rupture. However, it was seen that the outcome was influenced by dome projection throughout the three-month follow-up. The findings of our study indicate that aneurysms with a superior orientation exhibit the least likelihood of experiencing intraoperative rupture.

Supraorbital eyebrow approach and pterional approach in surgical treatment of ruptured and unruptured aneurysms: a propensity score-matched analysis

The aim of this study is to reveal efficacy and efficiency of the supraorbital eyebrow approach (SEA) in clipping ruptured and unruptured aneurysms where both SEA and pterional approach (PA) are considered feasible by comparing SEA and PA using propensity score matching. A total of 229 patients who underwent surgical clipping of an aneurysm from 2013 to 2022 and met inclusion criteria were recruited in the study. A study group of 67 patients treated via the SEA and a comparison group of 162 patients treated via the PA were formed. Then, the subgroups of 66 patients each, with balanced incoming factors, were analyzed using the propensity score technique. The safety and efficacy endpoints were compared. Successful clipping was achieved in all cases of both groups. There were no patients in the SEA group who required conversion to the standard craniotomy. There were no procedure-related deaths in this series. No patient experienced early or late rebleeding in either group. Mean blood loss volume in the SEA group was lower than in the PA group by approximately 77.5 ml (p < 0.001). There were favorable differences in the SEA group regarding postoperative neurological deficit (p = 0.016), postoperative epileptic seizure rate (p = 0.013), ischemic and hemorrhagic complications (p = 0.028 and 0.0009, respectively), and outcomes (p < 0.001). Patients' satisfaction with cosmetic results measured by the visual analog scale was rated highly in both groups (p = 0.081). For patients where SEA provides adequate exposure, it results in safety and cosmetic outcomes not inferior to the PA.

Complications of Endovascular and Open Aneurysm Surgery in the Era of Flow Diversion

The techniques used for treatment of intracranial aneurysms have progressed dramatically over the decades. The introduction of modern endovascular techniques and the continued refinement of progressively less invasive neurosurgical approaches have contributed to steadily improving clinical outcomes. Moreover, innovations such as flow-diverting stents have achieved dramatic success and have gained rapid widespread adoption. Particularly in lesions for which the application of conventional treatment techniques is difficult, flow diversion technology has revolutionized aneurysm management. This review provides a discussion on the morbidity and mortality encountered in the treatment of intracranial aneurysms in the modern era. Common adverse events faced in the management of these lesions with open surgery and various endovascular techniques are highlighted.

Evolution and Revolution of Imaging Technologies in Neurosurgery

We understand only a small fraction of the events happening in our brains; therefore, despite all the progress made thus far, a whole array of questions remains. Nonetheless, neurosurgeons invented new tools to circumvent the challenges that had plagued their predecessors. With the manufacturing boom of the 20th century, technological innovations blossomed enabling the neuroscientific community to study and operate upon the living brain in finer detail and with greater precision while avoiding harm to the nervous system. The purpose of this chronological review is to 1) raise awareness among future neurosurgeons about the latest advances in the field, 2) become familiar with innovations such as augmented reality (AR) that should be included in education given their ready applicability in surgical training, and 3) be comfortable with customizing these technologies to real-life cases like in the case of mixed reality.

Microsurgery for intracranial aneurysms: A qualitative survey on technical challenges and technological solutions

Introduction

Microsurgery for the clipping of intracranial aneurysms remains a technically challenging and high-risk area of neurosurgery. We aimed to describe the technical challenges of aneurysm surgery, and the scope for technological innovations to overcome these barriers from the perspective of practising neurovascular surgeons.

Materials and Methods

Consultant neurovascular surgeons and members of the British Neurovascular Group (BNVG) were electronically invited to participate in an online survey regarding surgery for both ruptured and unruptured aneurysms. The free text survey asked three questions: what do they consider to be the principal technical barriers to aneurysm clipping? What technological advances have previously contributed to improving the safety and efficacy of aneurysm clipping? What technological advances do they anticipate improving the safety and efficacy of aneurysm clipping in the future? A qualitative synthesis of responses was performed using multi-rater emergent thematic analysis.

Results

The most significant reported historical advances in aneurysm surgery fell into five themes: (1) optimising clip placement, (2) minimising brain retraction, (3) tissue handling, (4) visualisation and orientation, and (5) management of intraoperative rupture. The most frequently reported innovation by far was indocyanine green angiography (84% of respondents). The three most commonly cited future advances were hybrid surgical and endovascular techniques, advances in intraoperative imaging, and patient-specific simulation and planning.

Conclusions

While some surgeons perceive that the rate of innovation in aneurysm clipping has been dwarfed in recent years by endovascular techniques, surgeons surveyed highlighted a broad range of future technologies that have the potential to continue to improve the safety of aneurysm surgery in the future.

Clinical Trials of Microsurgery for Cerebral Aneurysms: Past and Future

BACKGROUND

New findings and research regarding the microsurgical treatment of intracerebral aneurysms (IAs) continue to advance even in the era of endovascular therapies. Research in the past 2 decades has continued to revolve around the question of whether open surgery or endovascular treatment is preferable. The answer remains both complex and in flux.

OBJECTIVE

This review focuses on microsurgery, reflects on the research decisions of previous landmark studies, and proposes future study designs that may further our understanding of IAs and how best to treat them.

RESULTS

The future of IA research may include a combination of pragmatic trials, artificial intelligence integrated tools, and mining of large data sets, in addition to the publication of high-quality single-center studies.

CONCLUSIONS

The future will likely emphasize testing innovative techniques, looking at granular patient data, and considering every patient encounter as a potential source of knowledge, creating a system in which data are updated daily because each patient interaction contributes to answering important research questions.

Single-Center Experience Using a 3D4K Digital Operating Scope System for Aneurysm Surgery

BACKGROUND

In recent years, 3D4K exoscope systems (EXs) have been introduced to microneurosurgery and reported to be an alternative to conventional operating microscopes (OMs). This study reviews our single-center experience using an 3D4K EX in intracranial aneurysm surgery.

OBJECTIVE

To investigate the applicability of a novel 3D4K EX for intracranial aneurysm surgery.

METHODS

A retrospective analysis of patients who underwent microsurgical repair of incidentally or ruptured cerebral aneurysms between August 2018 and August 2020 was performed. Patient and aneurysm characteristics and technical features, including 3-dimensional indocyanine green fluorescence, were evaluated. Data on surgery duration were statically assessed for a time trend and comparability with the OM cohort.

RESULTS

Overall, we collected 185 aneurysm cases in which the exoscope was used in 44 cases. The mean duration of surgery using the EX was in similar range to those using the OM (165.5 ± 45.8 minutes vs 160.5 ± 39.2 minutes, P > .05). Routine postoperative computed tomography angiography showed comparable rates of complete aneurysm occlusion (95.5% vs 92.2%, P > .05) and postoperative complications (9.1% vs 9.7%, P > .05). There was no necessity to revert to the OM from the EX. Three-dimensional indocyanine green fluorescence was used in all procedures without any malfunction.

CONCLUSION

The 3D4K EX for vascular microsurgical cases proved to be as useful as the OM. Because of the ease of use and comparable surgical results, the EX has the potential to become an accepted and additional visualization tool in vascular microsurgery next to the OM.

Long non-coding RNA NORAD induces phenotypic regulation of vascular smooth muscle cells through regulating microRNA-136-5p-targeted KDM1A

OBJECTIVE

Effect of long non-coding RNAs (lncRNAs) on intracranial aneurysm (IA) development has been identified, while the role of noncoding RNA activated by DNA damage (NORAD) in IA remains unexplored. We aimed to verify the impact of NORAD on IA through sponging microRNA-136-5p (miR-136-5p).

METHODS

Ruptured and unruptured IAs were harvested from IA patients, and expression of NORAD, miR-136-5p, and KDM1A was determined. The vascular smooth muscle cells (VSMCs) were cultured and, respectively, transfected with altered NORAD, miR-136-5p, or lysine-specific demethylase 1 (KDM1A) to observe their effect on biological functions, as well as on contraction and synthesis-specific indices of VSMCs. Interactions between NORAD and miR-136-5p, and between miR-136-5p and KDM1A were confirmed.

RESULTS

NORAD and KDM1A were upregulated while miR-136-5p was downregulated in IA, especially in ruptured IA. NORAD overexpression or miR-136-5p inhibition accelerated proliferation and migration, and decelerated phenotypic switching and apoptosis of VSMCs. The effects of overexpressed NORAD on VSMCs were reserved by miR-136-5p upregulation or KDM1A knockdown. NORAD functioned as a competing endogenous RNA of miR-136-5p and miR-136-5p targeted KDM1A.

CONCLUSION

NORAD suppressed miR-136-5p, thus upregulating KDM1A to participate in IA formation and rupture by inducing phenotypic regulation of VSMCs.

Cerebral Autoregulation in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype with a high rate of mortality and morbidity. The poor clinical outcome can be attributed to the biphasic course of the disease: even if the patient survives the initial bleeding emergency, delayed cerebral ischemia (DCI) frequently follows within 2 weeks time and levies additional serious brain injury. Current therapeutic interventions do not specifically target the microvascular dysfunction underlying the ischemic event and as a consequence, provide only modest improvement in clinical outcome. SAH perturbs an extensive number of microvascular processes, including the “automated” control of cerebral perfusion, termed “cerebral autoregulation.” Recent evidence suggests that disrupted cerebral autoregulation is an important aspect of SAH-induced brain injury. This review presents the key clinical aspects of cerebral autoregulation and its disruption in SAH: it provides a mechanistic overview of cerebral autoregulation, describes current clinical methods for measuring autoregulation in SAH patients and reviews current and emerging therapeutic options for SAH patients. Recent advancements should fuel optimism that microvascular dysfunction and cerebral autoregulation can be rectified in SAH patients.

Trends in Hospital-to-Hospital Transfers for Aneurysmal Subarachnoid Hemorrhage: A Single-Institution Experience from 2006 to 2017

BACKGROUND

Despite evidence to support that aneurysmal subarachnoid hemorrhage (aSAH) is best treated at high-volume centers, it is unknown whether clinical practice reflects these findings.

METHODS

We analyzed patients transferred to our high-volume center for aSAH between 2006 and 2017. Data collection included number of transfers, demographic data, Hunt and Hess score, Fisher score, comorbid conditions, length of stay (LOS), discharge disposition, in-hospital mortality rates, insurance status, and hospital charges. Comparisons were made across 3 time periods (2006-2009, 2010-2013, and 2014-2017) and included subgroup analyses by treatment modality (endovascular vs. microsurgical).

RESULTS

aSAH transfers declined from 213 in 2006-2009 to 160 in 2014-2017. While there was no change in presenting Hunt and Hess scores, the percentage of modified Fisher scores of 4 increased from 2006-2009 to 2014-2017. Transferred patients had a greater comorbidity index and decreased predicted 10-year survival. Despite this, the average LOS decreased. In-hospital mortality decreased from 2006-2009 to 2014-2017, especially in the endovascular cohort. The proportions of patients who were either self-pay or Medicaid did not change. Overall inflation-adjusted hospital charges decreased from $76,975 in 2006-2009 to $59,870 in 2014-2017.

CONCLUSIONS

Between 2006 and 2017, transfers to our center for aSAH declined. However, transferred patients had greater levels of complexity, more comorbidities, and were at greater risk for vasospasm based on their presenting Fisher score. Nonetheless, average LOS, in-hospital mortality, and cost declined. These changing referral patterns have implications for outcome data, quality reporting, resident education, and developing systems of care to optimize outcomes.

Comparison Between Minipterional Craniotomy Associated With Focused Sylvian Fissure Opening and Standard Pterional Approach With Extended Sylvian Fissure Dissection for Treatment of Unruptured Middle Cerebral Artery Aneurysms

BACKGROUND

In our institution, standard pterional craniotomy (PC) with an extended Sylvian fissure opening (ESFO) represented the standard approach for unruptured middle cerebral artery (MCA) aneurysm clipping until 2014, when we progressively started to prefer minipterional craniotomy (MPC) associated with a focused Sylvian fissure opening (FSFO). In the present study, we compared our results in terms of the efficacy of clipping and the rate of complications with these 2 different techniques.

METHODS

We included patients with small- and medium-size unruptured MCA aneurysms from January 2008 to December 2018 with follow-up of >12 months. The clinical and radiologic data were reviewed from the medical records. The outcomes were measured in terms of efficacy (aneurysmal exclusion rate) and safety (intracranial complication rate).

RESULTS

Overall, 134 patients who had presented with unruptured MCA aneurysms <1.5 cm were treated at our institution from January 2007 to December 2018: PC and ESFO were used in 73 patients and MPC and FSFO in 61. The demographics and angioarchitectural features were comparable between the 2 groups, except for age, which was older in the FSFO group. The aneurysm exclusion rate was not different between the 2 groups. The intracranial complication rate was, overall, significantly lower in the FSFO group (P < 0.001), especially for the rate of postoperative seizures. Finally, the FSFO group had had shorter postoperative hospitalization and better short- and long-term clinical outcomes.

CONCLUSIONS

The association between MPC and FSFO should represent the standard of treatment of unruptured MCA aneurysms in all referral cerebrovascular centers, allowing for the achievement of the same efficacy of standard PC with ESFO and minimizing the complications.

Application of the Endoscopic Micro-Inspection Tool QEVO® in the Surgical Treatment of Anterior Circulation Aneurysms-A Technical Note and Case Series

Introduction: The application of neuro-endoscopes in cerebral aneurysm surgery may help to avoid unintended aneurysm remnants and the accidental clipping of perforating arteries and aid the detection of blood collecting in the subdural spaces. Here, we present our experience with the novel endoscopic micro-inspection tool QEVO® (Carl Zeiss Meditec, Germany) in aneurysm surgery.

Materials and Equipment: In all patients the surgical microscope KINEVO® (Carl Zeiss Meditec, Germany) and the Microinspection tool QEVO® were applied.

Methods: The case series comprises 22 unruptured cerebral aneurysms of the anterior circulation. All aneurysms were treated surgically. All patients routinely underwent computed tomography and digital subtraction angiography within 10 days after surgery.

Results: No aneurysm remnants, cerebral ischemic deficits, or subdural hematomas were detected.

Discussion: In this technical note, we discuss the benefits and limitations of the QEVO® tool and illustrate the major paradigms by means of intraoperative photographs.

ANXA3 Silencing Ameliorates Intracranial Aneurysm via Inhibition of the JNK Signaling Pathway

Intracranial aneurysm (IA) rupture is a major cause of stroke death. Alteration of vascular smooth muscle cell (VSMC) function and phenotypic modulation plays a role in aneurysm progression. In the present study, we investigated the role of Annexin A3 (ANXA3) silencing in IA with the interaction of the c-Jun N-terminal kinase (JNK) signaling pathway. In IA and VSMCs of IA, the relationship between ANXA3 and the JNK signaling pathway was verified. To investigate the specific mechanism of ANXA3 silencing in IA, we transfected VSMCs with the overexpressed or small interfering RNA (siRNA) of ANXA3, or treated them with an inhibitor of the JNK signaling (SP600125). Cell counting kit-8 (CCK-8) assay was conducted to detect cell viability, and flow cytometry was conducted to assess cell cycle and apoptosis so as to evaluate the gain- and loss-of-function of ANXA3 and investigate the involvement of the JNK signaling pathway. The aneurysm wall of IA cells demonstrated an elevated level of ANXA3 expression and an activated JNK signaling pathway. VSMCs treated with siRNA-ANXA3 or SP600125 showed decreased expression of JNK, caspase-3, osteopontin (OPN), Bax, and matrix metalloproteinase-9 (MMP-9), as well as phosphate (p)-JNK, but increased the expression of α smooth muscle actin (α-SMA), β-tubulin, and Bcl-2. ANXA3 silencing or inactivation of the JNK signaling pathway also enhanced proliferation and repressed apoptosis of VSMCs. Collectively, this study shows that the silencing of ANXA3 can rescue VSMC function in IAs by inhibiting the phosphorylation and activation of the JNK signaling pathway. These findings may provide a potential therapy for the molecular treatment of IAs.

The Changing Landscape of Treatment for Intracranial Aneurysm

There has been a significant transformation in the treatment of intracranial aneurysms (IAs) over the past century, with the most pivotal changes occurring in the past three decades. To characterize this evolution, we assessed the number of articles published on various procedures for the treatment of IA as a measure of their interest and usage over time. We separated our analysis into two main areas: surgical and endovascular approaches. We further subdivided these two main categories into clipping and bypass for surgery, and coiling, flow diversion, and liquid material embolization for endovascular approaches. We found 5956 publications on open surgical approaches in the 70-year period from 1947 to 2017, with papers on clipping (n = 4204), being the most common. We found 8602 endovascular publications beginning in 1964, with most of the activity taking place in the late 1990s and beyond. Coiling had the most publications of the endovascular approaches (n = 5436). In 1999, the number of annual publications on endovascular treatments surpassed those of open surgery, signaling a crossover point in the IA literature. The same trend continues to this date.