Sex Difference and Rupture Rate of Intracranial Aneurysms: An Individual Patient Data Meta-Analysis.

BACKGROUND AND PURPOSE: In previous studies, women had a higher risk of rupture of intracranial aneurysms than men, but female sex was not an independent risk factor. This may be explained by a higher prevalence of patient- or aneurysm-related risk factors for rupture in women than in men or by insufficient power of previous studies. We assessed sex differences in rupture rate taking into account other patient- and aneurysm-related risk factors for aneurysmal rupture. METHODS: We searched Embase and Pubmed for articles published until December 1, 2020. Cohorts with available individual patient data were included in our meta-analysis. We compared rupture rates of women versus men using a Cox proportional hazard regression model adjusted for the PHASES score (Population, Hypertension, Age, Size of Aneurysm, Earlier Subarachnoid Hemorrhage From Another Aneurysm, Site of Aneurysm), smoking, and a positive family history of aneurysmal subarachnoid hemorrhage. RESULTS: We pooled individual patient data from 9 cohorts totaling 9940 patients (6555 women, 66%) with 12 193 unruptured intracranial aneurysms, and 24 357 person-years follow-up. Rupture occurred in 163 women (rupture rate 1.04%/person-years [95% CI, 0.89-1.21]) and 63 men (rupture rate 0.74%/person-years [95% CI, 0.58-0.94]). Women were older (61.9 versus 59.5 years), were less often smokers (20% versus 44%), more often had internal carotid artery aneurysms (24% versus 17%), and larger sized aneurysms (≥7 mm, 24% versus 23%) than men. The unadjusted women-to-men hazard ratio was 1.43 (95% CI, 1.07-1.93) and the adjusted women/men ratio was 1.39 (95% CI, 1.02-1.90). CONCLUSIONS: Women have a higher risk of aneurysmal rupture than men and this sex difference is not explained by differences in patient- and aneurysm-related risk factors for aneurysmal rupture. Future studies should focus on the factors explaining the higher risk of aneurysmal rupture in women.

SORG algorithm to predict 3- and 12-month survival in metastatic spinal disease: a cross-sectional population-based retrospective study.

PURPOSE: In this study, we wished to compare statistically the novel SORG algorithm in predicting survival in spine metastatic disease versus currently used methods. METHODS: We recruited 40 patients with spinal metastatic disease who were operated at Geneva University Hospitals by the Neurosurgery or Orthopedic teams between the years of 2015 and 2020. We did an ROC analysis in order to determine the accuracy of the SORG ML algorithm and nomogram versus the Tokuhashi original and revised scores. RESULTS: The analysis of data of our independent cohort shows a clear advantage in terms of predictive ability of the SORG ML algorithm and nomogram in comparison with the Tokuhashi scores. The SORG ML had an AUC of 0.87 for 90 days and 0.85 for 1 year. The SORG nomogram showed a predictive ability at 90 days and 1 year with AUCs of 0.87 and 0.76 respectively. These results showed excellent discriminative ability as compared with the Tokuhashi original score which achieved AUCs of 0.70 and 0.69 and the Tokuhashi revised score which had AUCs of 0.65 and 0.71 for 3 months and 1 year respectively. CONCLUSION: The predictive ability of the SORG ML algorithm and nomogram was superior to currently used preoperative survival estimation scores for spinal metastatic disease.

Surgical challenges in posterior cervicothoracic junction instrumentation.

The cervicothoracic junction (CTJ) is a region of the spine submitted to significant mechanical stress. The peculiar anatomical and biomechanical characteristics make posterior surgical stabilization of this area particularly challenging. We present and discuss our surgical series highlighting the specific surgical challenges provided by this region of the spine. We have analyzed and reported retrospective data from patients who underwent a posterior cervicothoracic instrumentation between 2011 and 2019 at the Neurosurgical Department of the Geneva University Hospitals. We have discussed C7 and Th1 instrumentation techniques, rods design, extension of constructs, and spinal navigation. Thirty-six patients were enrolled. We have preferentially used lateral mass (LM) screws in the subaxial spine and pedicle screws (PS) in C7, Th1, and upper thoracic spine. We have found no superiority of 3D navigation techniques over 2D fluoroscopy guidance in PS placement accuracy, probably due to the relatively small case series. Surgical site infection was the most frequent complication, significantly associated with tumor as diagnosis. When technically feasible, PS represent the technique of choice for C7 and Th1 instrumentation although other safe techniques are available. Different rod constructs are described although significant differences in biomechanical stability still need to be clarified. Spinal navigation should be used whenever available even though 2D fluoroscopy is still a safe option. Posterior instrumentation of the CTJ is a challenging procedure, but with correct surgical planning and technique, it is safe and effective.

Foramen magnum meningiomas: a systematic review and meta-analysis.

Foramen magnum meningiomas (FMMs) account for 1.8-3.2% of all meningiomas. With this systematic review and meta-analysis, our goal is to detail epidemiology, clinical features, surgical aspects, and outcomes of this rare pathology. Using PRISMA 2015 guidelines, we reviewed case series, mixed series, or retrospective observational cohorts with description of surgical technique, patient and lesion characteristics, and pre- and postoperative clinical status. A meta-analysis was performed to search for correlations between meningioma characteristics and rate of gross total resection (GTR). We considered 33 retrospective studies or case series, including 1053 patients, mostly females (53.8%), with a mean age of 52 years. The mean follow-up was of 51 months (range 0-258 months). 65.6% of meningiomas were anterior, and the mean diameter was of 29 mm, treated with different surgical approaches. Postoperatively, 17.2% suffered complications (both surgery- and non-surgery-related) and 2.5% had a recurrence. The Karnofsky performance score improved in average after surgical treatment (75 vs. 81, p < 0.001). Our meta-analysis shows significant rates of GTR in cohorts with a majority of posterior and laterally located FMM (p = 0.025) and with a mean tumor less than 25 mm (p < 0.05). FMM is a rare and challenging pathology whose treatment should be multidisciplinary, focusing on quality of life. Surgery still remains the gold standard and aim at maximal resection with neurological function preservation. Adjuvant therapies are needed in case of subtotal removal, non-grade I lesions, or recurrence. Specific risk factors for recurrence, other than Simpson grading, need further research.

Compressive cervicothoracic pseudomeningocele as a rare manifestation of idiopathic intrathecal hypotension after past trauma: a review.

PURPOSE: Spontaneous intracranial or intrathecal hypotension (SIH) is an underdiagnosed phenomenon predominantly presenting with low cerebrospinal fluid (CSF) pressure and postural headache in the setting of CSF leak. Extrathecal CSF collections causing compression of the spinal cord or nerve roots present an even rarer subset of this disease. We aim to describe this pathology in a comprehensive manner while illustrating with a case of our own. METHODS: We present a literature review on spinal idiopathic pseudomeningoceles and their neurological implications illustrated with a case of an anterior compressive pseudomeningocele between C2 and D7. Further investigations through a myelography and myelo-CT were able to postulate a CSF leak through a discogenic osteophytic microspur at the level C5-C6. RESULTS: Spinal manifestations are uncommon in cases of idiopathic or spontaneous CSF leak, occurring in about 6% of patients, but myelopathy and radiculopathy involving all spinal segments do occur. In contrast to the cranial complaints, the spinal manifestations usually are not positional and are caused by mass effect from an extradural CSF collection. CONCLUSION: The utility of multiple imaging modalities such as dynamic myelography and the use of epidural blood patches and fibrin glue polymers should be explored, and surgery is an option if the symptoms persist despite other measures.

Ergonomics and musculoskeletal disorders in neurosurgery: a systematic review.

BACKGROUND: Work-related musculoskeletal disorders (WMSDs) are a growing and probably undervalued concern for neurosurgeons and spine surgeons, as they can impact their quality of life and career length. This systematic review aims to ascertain this association and to search for preventive measures. METHODS: We conducted a PRISMA-P-based review on ergonomics and WMSDs in neurosurgery over the last 15 years. Twelve original articles were included, of which 6 focused on spine surgery ergonomics, 5 cranio-facial surgery (mainly endoscopic), and one on both domains. RESULTS: We found a huge methodological and content diversity among studies with 5 surveys, 3 cross-sectional studies, 2 retrospective cohorts, and 2 technical notes. Spine surgeons have sustained neck flexion and neglect their posture during surgery. In a survey, low back pain was found in 62% of surgeons, 31% of them with a diagnosed lumbar disc herniation, and 23% of surgery rate. Pain in the neck (59%), shoulder (49%), finger (31%), and wrist (25%) are more frequent than in the general population. Carpal tunnel syndrome showed a linear relationship with increasing cumulative hours of spine surgery practice. Among cranial procedures, endoscopy was also significantly related to shoulder pain while pineal region surgery received some attempts to optimize ergonomics. CONCLUSIONS: Ergonomics in neurosurgery remains underreported and lack attention from surgeons and authorities. Improvements shall target postural ergonomics, equipment design, weekly schedule adaptation, and exercise.

PHASES Score for the Management of Intracranial Aneurysm: A Cross-Sectional Population-Based Retrospective Study.

BACKGROUND AND PURPOSE: The aim of this study is to assess whether the PHASES score allows to (1) match decisions taken by multidisciplinary team whether to observe or intervene, (2) classify patients being diagnosed with a ruptured versus unruptured intracranial aneurysm (UIA), and (3) discriminate patients at low risk of rupture from the population of patients diagnosed with intracranial aneurysm. METHODS: Population-based prospective and consecutive data were collected between 2006 and 2014. Patients (n=841) were stratified into 4 groups: stable UIA; growing observed UIA; immediately treated UIA; and aneurysmal subarachnoid hemorrhage (aSAH). All patients initially observed were pooled in a follow-up UIA group; patients from growing observed UIA, immediately treated UIA, and aSAH were pooled in a high risk of rupture group. Results are expressed as median [quartile 1, quartile 3]. RESULTS: PHASES scores of immediately treated UIA patients were significantly higher than follow-up UIA group (5 [3, 7] versus 2 [1, 4]). Patients diagnosed with UIA and PHASES score of >3 were more likely to be treated, and the score ≤3 was predictive for observation (areas under these curves=0.74). Odds of being diagnosed with an aSAH were associated with PHASES score of >3 (UIA, 4 [2, 6]; aSAH, 5 [4, 8]; areas under these curves=0.66). Scores of stable UIA patients were significantly lower than high risk of rupture group (2 [1, 4] versus 5 [4, 7]; stable UIA outcome prediction by PHASES score of ≤3: areas under these curves=0.76). CONCLUSIONS: There is a progression of PHASES score between stable UIA, growing observed UIA, immediately treated UIA, and aSAH groups. PHASES score of ≤3 is associated with a low but not negligible likelihood of aneurysm rupture, and specificity of the classifier is low.

Unruptured intracranial aneurysm follow-up and treatment after morphological change is safe: observational study and systematic review.

BACKGROUND: The management of small unruptured incidentally discovered intracranial aneurysms (SUIAs) is still controversial. The aim of this study is to assess the safety of a management protocol of SUIAs, where selected cases with SUIAs are observed and secured only if signs of instability (growth) are documented. METHODS: A prospective consecutive cohort of 292 patients (2006-2014) and 368 SUIAs (anterior circulation aneurysms (ACs) smaller than 7 mm and posterior circulation aneurysms smaller than 4 mm without previous subarachnoid haemorrhage) was observed (mean follow-up time of 3.2 years and 1177.6 aneurysm years). Factors associated with aneurysm growth were systematically reviewed from the literature. RESULTS: The aneurysm growth probability was 2.6±0.1% per year. The rate of unexpected aneurysm rupture before treatment was 0.24% per year (95% CI 0.17% to 2.40%). The calculated rate of aneurysm rupture after growth was 6.3% per aneurysm-year (95% CI 1% to 22%). Aneurysms located in the posterior circulation and aneurysms with lobulation were more likely to grow. Females or patients suffering hypertension were more likely to have an aneurysm growing. The probability of aneurysms growth increased with the size of the dome and was proportional to the number of aneurysms diagnosed in a patient. CONCLUSIONS: It is safe to observe patients diagnosed with SUIAs using periodic imaging. Intervention to secure the aneurysm should be performed after growth is observed.

Safety of Nitrous Oxide Anesthesia in a Selected Group of Patients Undergoing Neurosurgery: An Exploratory Subgroup Analysis of the ENIGMA Trials.

BACKGROUND: The Evaluation of Nitrous Oxide in the Gas Mixture for Anesthesia (ENIGMA)-I and ENIGMA-II were randomized clinical trials that assessed the safety of nitrous oxide anesthesia in patients undergoing noncardiac surgery. In this study, we performed an exploratory pooled analysis of both ENIGMA trials to assess the safety of nitrous oxide in a selected group of patients undergoing neurosurgery. METHODS: Data from each ENIGMA trial were collated into a single database. Information regarding patient demographics, comorbidities, medication use, anesthesia, surgical procedure, and postoperative complications was extracted. Multivariate logistic regression was conducted for postoperative complications to assess the risk associated with nitrous oxide. RESULTS: A total of 830 patients were included in our analysis: 417 received nitrous oxide anesthesia, and 413 received nitrous oxide-free anesthesia. Baseline patient and perioperative characteristics were comparable. Procedural data were available for 535 patients (64%); of these, 507 (95%) underwent spinal neurosurgery and 28 (5%) underwent cranial neurosurgery. Patients in the nitrous oxide group had lower inspired oxygen concentration (30% vs. 38%; P<0.001) and end-tidal volatile agent concentration (0.56 vs. 0.89 minimal alveolar concentration equivalents; P<0.001) compared with the nitrous oxide-free group. Use of nitrous oxide was not associated with increased risk of postoperative complications (myocardial infarction, cardiac arrest, stroke, infection, severe vomiting, fever, pneumonia, pneumothorax, blood transfusion, venous thromboembolism, or death) (odds ratio: 1.22; 95% confidence interval: 0.89-1.65; P=0.22) or prolonged length of hospital stay (median 5.0 vs. 4.2 d for nitrous oxide and nitrous oxide-free groups; P=0.28). CONCLUSION: Nitrous oxide did not increase the risk of postoperative complications or prolonged length of hospital stay in the neurosurgical cohort enrolled in the ENIGMA-I and ENIGMA-II trials.

Chronic Subdural Hematoma (cSDH): A review of the current state of the art.

Introduction: Incidence of Chronic Subdural Hematoma (cSDH) is rising worldwide, partly due to an aging population, but also due to increased use of antithrombotic medication. Many recent studies have emerged to address current cSDH management strategies. Research question: What is the state of the art of cSDH management. Material and methods: Review. Results: Head trauma, antithrombotic use and craniocerebral disproportion increase the risk of cSDH development. Most patients present with disorientation, GCS 13-15, and symptoms arising from cortical irritation and increased intracranial pressure. cSDH occurs bilaterally in 9-22%. CT allows assessment of cerebral compression (herniation, hematoma thickness, ventricle collapse, midline shift), hematoma age and presence of membranes, factors that ultimately determine treatment urgency and surgical approach. Recurrence remains the principle complication (9-33%), occurring more commonly with older age and bilateral cSDHs. Discussion and conclusion: While incompletely understood, it is generally believed that injury in the dural cell layer results in bleeding from bridging veins, resulting in a hematoma formation, with or without a preceding hygroma, in a potential space approximating the junction between the dura and arachnoid. Neovascularization and leaking from the outer membrane are thought to propagate this process. Evidence that MMA embolization may reduce recurrence rates is a potentially exciting new treatment option, but also supports the theory that the MMA is implicated in the cSDH pathophysiology. The use of steroids remains a controversial topic without clear treatment guidelines. cSDH represents a common neurosurgical problem with burr-hole treatment remaining the gold standard, often in conjunction with subgaleal drains. MMA embolization to stop recurrence may represent an important evolution in understanding the pathophysiology of cSDH and improving treatment.

Meningiomas and Cognitive Impairment after Treatment: A Systematic and Narrative Review.

Clinical outcomes after surgery for intracranial meningiomas might be overvalued as cognitive dimensions and quality of life are probably underreported. This review aims to summarize the current state of cognitive screening and treatment-related outcomes after meningioma surgery. We present a systematic review (Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA-P) 2015-based) of cognitive outcomes after intracranial meningioma surgery. A total of 1572 patients (range 9-261) with a mean age of 58.4 years (range 23-87), and predominantly female (n = 1084, 68.9%) were identified. Mean follow-up time after treatment was 0.86 ± 0.3 years. Neuropsychological assessment was very heterogeneous, but five dimensions of cognition were described: memory (19/22); attention (18/22); executive functions (17/22); language (11/22); flexibility (11/22 studies). Cognitive abilities were impaired in 18 studies (81.8%), but only 1 showed deterioration in all dimensions simultaneously. Memory was the most affected. with significant post-therapy impairment in 9 studies (40.9%). Postoperatively, only 4 studies (18.2%) showed improvement in at least one dimension. Meningioma patients had significantly lower cognitive scores when compared to healthy subjects. Surgery and radiotherapy for meningiomas were associated with cognitive impairment, probably followed by a partial recovery. Cognition is poorly defined, and the assessment tools employed lack standardization. Cognitive impairment is probably underreported in meningioma patients.

Does Spondylolisthesis Affect Severity and Outcome of Degenerative Cervical Myelopathy? A Systematic Review and Meta-analysis.

STUDY DESIGN: This was a systematic review and meta-analysis. OBJECTIVES: Degenerative cervical myelopathy (DCM) with spondylolisthesis remains not well defined, poorly studied, and underreported and plays a minor role in the therapeutic decision-making. Spondylolisthesis, however, is not uncommon and may result in dynamic injury to the spinal cord. We aim to describe the impact of spondylolisthesis in DCM severity and postoperative outcomes. METHODS: Two independent reviewers conducted a Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA 2015)-based review between 1970 and May 2020 for articles reporting outcome of DCM in patients with degenerative cervical spondylolisthesis. Patient clinical and radiological data was recorded at baseline and during postoperative follow-up (FU). A meta-analysis comparing surgical outcome between DCM patients with and without spondylolisthesis assessed by the regular/modified Japanese Orthopaedic Association Assessment Scale (mJOA) recovery ratio was completed. RESULTS: A total of 3 studies were included (1 ambispective and 2 retrospective cohorts); 607 patients with DCM were identified, 102 (16.8%) of whom also had spondylolisthesis. DCM patients with spondylolisthesis were significantly older (P < .05), presented with worse baseline mJOA and Nurick grades (P < .05 in 2 studies), and were more commonly operated via posterior approaches (P < .05). All groups experienced a (m)JOA and/or Neck Disability Index score improvement during FU. In the pooled meta-analysis, spondylolisthesis patients showed a significantly lower functional recovery ratio at 2 years compared with other DCM patients (P = .05). CONCLUSIONS: Spondylolisthesis is frequent in older DCM patients and may be a predictor of a more advanced degeneration and subsequent worse baseline conditions and postoperative outcome.

Sensitivity and Negative Predictive Value of Motor Evoked Potentials of the Facial Nerve.

OBJECTIVE: The objective of this study was to determine the performance of the standard alarm criterion of motor evoked potentials (MEPs) of the facial nerve in surgeries performed for resections of vestibular schwannomas or of other lesions of the cerebellopontine angle. METHODS: This retrospective study included 33 patients (16 with vestibular schwannomas and 17 with other lesions) who underwent the resection surgery with transcranial MEPs of the facial nerve. A reproducible 50% decrease in MEP amplitude, resistant to a 10% increase in stimulation intensity, was applied as the alarm criterion during surgery. Facial muscular function was clinically evaluated with the House-Brackmann score (HBS), pre- and postsurgery at 3 months. RESULTS: In the patient group with vestibular schwannoma, postoperatively, the highest sensitivity and negative predictive values were found for a 30% decrease in MEP amplitude, that is, a criterion stricter than the 50% decrease in MEP amplitude criterion, prone to trigger more warnings, used intraoperatively. With this new criterion, the sensitivity would be 88.9% and the negative predictive value would be 85.7%. In the patient group with other lesions of the cerebellopontine angle, the highest sensitivity and negative predictive values were found equally for 50, 60, or 70% decrease in MEP amplitude. With these criteria, the sensitivities and the negative predictive values would be 100.0%. CONCLUSION: Different alarm criteria were found for surgeries for vestibular schwannomas and for other lesions of the cerebellopontine angle. The study consolidates the stricter alarm criterion, that is, a criterion prone to trigger early warnings, as found previously by others for vestibular schwannoma surgeries (30% decrease in MEP amplitude).

Neuropsychological Outcomes after Surgery for Olfactory Groove Meningiomas.

BACKGROUND: In recent years, several studies have reported abnormal pre- and postoperative neuropsychological functioning in patients with meningiomas located in the prefrontal cortex (notably the ventromedial region). In the case of olfactory groove meningiomas, the tumor is in direct contact with the inferior aspect of the prefrontal cortex, a cortical region with crucial roles in decision-making, cognition and memory functions, potentially negatively impacting neuropsychological functions. MATERIALS AND METHODS: We retrospectively compared pre- and post-operative neuropsychological testing of 17 patients undergoing surgical removal of olfactory groove meningiomas in our institution between January 2013 and December 2018. Neuropsychological results were obtained from the patients' medical history and normalized as z-scores of their respective cognitive functions. RESULTS: Assessment of cognitive follow-up showed an important heterogeneity among patients. Pre-operative cognitive impairment was observed in most patients, particularly in cognitive flexibility (mean z-score: -1.35). Immediate post-operative cognitive status showed an overall impairment in all domains of cognition, significant for the domains of attention (p = 0.0273) and flexibility (p = 0.0234) and almost significant for the domain of language (p = 0.0547). The late follow-up at one year showed a trend towards general improvement, although attention and flexibility remained impaired. DISCUSSION: Olfactory groove meningiomas impact pre-frontal cortex cognitive functions, particularly in the domain of cognitive flexibility. After an initial postoperative worsening, patients tended to improve in most aspects after one year, aside from cognitive flexibility and attention.

Degenerative Cervical Myelopathy and the Aging Spine: Introduction to the Special Issue.

Degenerative Cervical Myelopathy (DCM) is the most common cause of spinal cord injury in the world, but despite this, there remains many areas of uncertainty regarding the management of the condition. This special issue was dedicated to presenting current research topics in DCM. Within this issue, 12 publications are presented, including an introductory narrative overview of DCM and 11 articles comprising 9 research papers and 2 systematic reviews focusing on different aspects, ranging from genetic factors to clinical assessments, imaging, sagittal balance, surgical treatment, and outcome prediction. These articles represented contributions from a diverse group of researchers coming from multiple countries, including Switzerland, Germany, Italy, United Kingdom, United States, South Korea, and Canada.

Hemodynamics of Focal Versus Global Growth of Small Cerebral Aneurysms.

BACKGROUND AND PURPOSE: Hemodynamics play a driving role in the life cycle of brain aneurysms from initiation through growth until eventual rupture. The specific factors behind aneurysm growth, especially in small aneurysms, are not well elucidated. The goal of this study was to differentiate focal versus general growth and to analyze the hemodynamic microenvironment at the sites of enlargement in small cerebral aneurysms. MATERIALS AND METHODS: Small aneurysms showing growth during follow-up were identified from our prospective aneurysm database. Three dimensional rotational angiography (3DRA) studies before and after morphology changes were available for all aneurysms included in the study, allowing for detailed shape and computational fluid dynamic (CFD) based hemodynamic analysis. Six patients fulfilled the inclusion criteria. RESULTS: Two different types of change were observed: focal growth, with bleb or blister formation in three, and global aneurysm enlargement accompanied by neck broadening in other three patients. Areas of focal growth showed low shear conditions with increased oscillations at the site of growth (a low wall shear stress [WSS] and high oscillatory shear index [OSI]). Global aneurysm enlargement was associated with increased WSS coupled with a high spatial wall shear stress gradient (WSSG). CONCLUSION: For different aneurysm growth types, distinctive hemodynamic microenvironment may be responsible and temporal-spatial changes of the pathologic WSS would have the inciting effect. We suggest the distinction of focal and global growth types in future hemodynamic and histological studies.

Correlating Clinical Risk Factors and Histological Features in Ruptured and Unruptured Human Intracranial Aneurysms: The Swiss AneuX Study.

Pathogenesis of intracranial aneurysm is complex and the precise biomechanical processes leading to their rupture are uncertain. The goal of our study was to characterize the aneurysmal wall histologically and to correlate histological characteristics with clinical and radiological factors used to estimate the risk of rupture. A new biobank of aneurysm domes resected at the Geneva University Hospitals (Switzerland) was used. Histological analysis revealed that unruptured aneurysms have a higher smooth muscle cell (SMC) content and a lower macrophage content than ruptured domes. These differences were associated with more collagen in unruptured samples, whereas the elastin content was not affected. Collagen content and type distribution were different between thick and thin walls of unruptured aneurysms. Classification of aneurysm domes based on histological characteristics showed that unruptured samples present organized wall rich in endothelial and SMCs compared with ruptured samples. Finally, aneurysm wall composition was altered in unruptured domes of patients presenting specific clinical factors used to predict rupture such as large dome diameter, dome irregularities, and smoking. Our study shows that the wall of aneurysm suspected to be at risk for rupture undergoes structural alterations relatively well associated with clinical and radiological factors currently used to predict this risk.