Pterional vs. lateral supraorbital approach in the management of middle cerebral artery aneurysms: insights from a phantom model study.

The pterional approach has traditionally been employed for managing middle cerebral artery (MCA) aneurysms. With potential benefits like reduced surgical morbidity and improved postoperative recovery, the lateral supraorbital approach (LSO) should be considered individually based on aneurysm morphology, location and patient-specific variations of the MCA anatomy, which requires considerable technical expertise traditionally acquired through years of experience. The goal of this study was the development and evaluation of a novel phantom simulator in the context of clinical decision-making in the managmement of MCA aneurysms. For this purpose, high-fidelity simulators inclusive of MCA models with identical M1- and bifurcation aneurysms were manufactured employing 3D reconstruction techniques, additive manufacturing and rheological testings. Medical students, neurosurgical residents, and seasoned neurosurgeons (n = 22) tested and evaluated both approaches. Participants' performances and progress over time were assessed based on objective metrics. The simulator received positive ratings in face and content validity, with mean scores of 4.9 out of 5, respectively. Objective evaluation demonstrated the model's efficacy as a practical training tool, particularly among inexperienced participants. While requiring more technical expertise, results of the comparative analysis suggest that the LSO approach can improve clipping precision and outcome particularly in patients with shorter than average M1-segments. In conclusion, the employed methodology allowed a direct comparison of the pterional and LSO approaches, revealing comparable success rates via the LSO approach while reducing operation time and complication rate. Future research should aim to establish simulators in the context of clinical decision making.

Anterior interhemispheric vs. pterional approach in the microsurgical management of anterior communicating artery aneurysms: a comparative analysis employing a novel multidimensional matching-tool.

The surgical management of anterior communicating artery aneurysms (AcomA) is challenging due to their deep midline position and proximity to complex skull base anatomy. This study compares the pterional craniotomy with the interhemispheric approach based on the specific aneurysm angulation. A total of 129 AcomA cases were analyzed, with 50 undergoing microsurgical clipping via either the pterional or interhemispheric approach. All selected cases had computed tomography-angiography with sagittal imaging slices and 2D-angiography. Using an interactive tool, 14 cases treated via the interhemispheric approach were matched with 14 cases approached pterionally based on clinical and morphological parameters, emphasizing intracranial aneurysm (IA) dome angulation relative to the frontal skull base. Outcomes included IA occlusion, temporary clipping incidence, intraoperative rupture, postoperative strokes, hemorrhages, hydrocephalus, vasospasm, and patient functionality. Matched cohorts had consistent demographics. Both approaches resulted in similar IA occlusion rates, but the interhemispheric approach led to improved clinical outcomes, measured by the modified Rankin Scale. It also had a lower incidence of hydrocephalus and reduced need for permanent ventriculoperitoneal shunt placement. Vasospasms and postoperative infarction rates were comparable between the groups. Our findings suggest potential advantages of the interhemispheric approach in managing AcomA, depending on aneurysm angulation. Despite a small sample size, the results highlight the importance of customized surgical decision-making based on the unique traits of each aneurysm and the surgeon's expertise.

Unveiling rupture risk and clinical outcomes in midline aneurysms: A matched cohort analysis investigating the impact of localization within the anterior or posterior circulation.

Intracranial aneurysms (IAs) located in the anterior and posterior circulations of the Circle of Willis present differential rupture risks. This study aimed to compare the rupture risk and clinical outcomes of anterior communicating artery aneurysms (AcomA) and basilar tip aneurysms (BAs); two IA types located along the midline within the Circle of Willis. We retrospectively collected data from 1026 patients presenting with saccular IAs. Only AcomA and BAs with a 3D angiography were included. Out of 186 included IAs, a cohort of 32 BAs was matched with AcomA based on the patients' pre-existing conditions and morphological parameters of IAs. Clinical outcomes, including rupture risk, hydrocephalus development, vasospasm incidence, and patients' outcome, were compared. The analysis revealed no significant difference in rupture risk, development of hydrocephalus, need for ventricular drainage, or vasospasm incidence between the matched AcomA and BA cohorts. Furthermore, the clinical outcomes post-rupture did not significantly differ between the two groups, except for a higher Fisher Grade associated with BAs. Once accounting for morphological and patient factors, the rupture risk between AcomA and BAs is comparable. These findings underscore the importance of tailored management strategies for specific IA types and suggest that further investigations should focus on the role of individual patient and aneurysm characteristics in IA rupture risk and clinical outcomes.

Theranostic applications of optical coherence tomography in neurosurgery?

In light of our own experiences, we value the existing literature to critically point out possible "near" future applications of optical coherence tomography (OCT) as an intraoperative neurosurgical guidance tool. "Pub Med", "Cochrane Library", "Crossref Metadata Search", and "IEEE Xplore" databases as well as the search engine "Google Scholar" were screened for "optical coherence tomography + neurosurgery", "optical coherence tomography + intraoperative imaging + neurosurgery", and "microscope integrated optical coherence tomography + neurosurgery". n = 51 articles related to the use of OCT as an imaging technique in the field of neurosurgery or neurosurgical research. n = 7 articles documented the intraoperative use of OCT in patients. n = 4 articles documented the use of microscope-integrated optical coherence tomography as a neurosurgical guidance tool. The Results demonstrate that OCT is the first imaging technique to study microanatomy in vivo. Postoperative analysis of intraoperative scans holds promise to enrich our physiological and pathophysiological understanding of the human brain. No data exists to prove that OCT-guided surgery minimizes perioperative morbidity or extends tumor resection. But results suggest that regular use of microscope-integrated OCT could increase security during certain critical microsurgical steps like, e.g., dural dissection at cavernous sinus, transtentorial approaches, or aneurysm clip placement. Endoscopy integration could aid surgery in regions which are not yet accessible to real-time imaging modalities like the ventricles or hypophysis. Theranostic instruments which combine OCT with laser ablation might gain importance in the emerging field of minimal invasive tumor surgery. OCT depicts vessel wall layers and its pathologies uniquely. Doppler OCT could further visualize blood flow in parallel. These abilities shed light on promising future applications in the field of vascular neurosurgery.

Aneurysm Architecture: First in vivo Imaging of Human Cerebral Aneurysms with Extravascular Optical Coherence Tomography.

OBJECTIVE: The present study was conducted to explore the value of 3-dimensional microscope integrated extravascular optical coherence tomography (OCT) as the first suitable intraoperative imaging modality of cerebral aneurysm (CA) and parent vessel wall morphology. METHODS: Incidental CAs (n = 16) of the anterior circulation with indication for microsurgical clipping were scanned. RESULTS: Analysis revealed that intraoperative OCT achieved to delineate the microstructural composition of the parent vessel in all cases and the CA wall in 68.8%. Clinical relevant characteristics such as thickness, calcification, residual tunica media, and atherosclerotic plaque of CA wall could be demonstrated with high image quality approaching the spatial resolution of histopathology. CONCLUSION: Our findings demonstrate that intraoperative OCT may hold promise as an additional imaging tool during neurovascular procedures.

Evaluation of the risk of rupture of intracranial aneurysms in patients with aneurysmal subarachnoid hemorrhage according to the PHASES score.

The PHASES score was developed to determine the risk of rupture of un-ruptured intracranial aneurysms (UIAs). The purposes of the current study were to apply this score on patients with actually ruptured intracranial aneurysms and to analyze the hypothetically prediction of the risk in this particularly patient group. We extracted the data of 100 recently treated patients (23 male, 77 female, mean age 56.4 years, range 17-93 years) with ruptured saccular intracranial aneurysms from our prospectively maintained neurovascular database according to the parameters used in the PHASES score (population, hypertension, age, earlier SAH, size and site of the aneurysm). Descriptive statistical analysis was performed using SPSS for Windows version 18.0 (SPSS Inc., Chicago, Illinois, USA). Ninety-nine percent of the patients were European and 1% Japanese in our series. Pre-existing arterial hypertension was found in 59%. Fifteen percent of the patients were > 75 years. Earlier SAH was found in 1%. The site of the aneurysms were the internal carotid artery (ICA) in 10%, the middle cerebral artery (MCA) in 14%, and arteries of the anterior and posterior circulation (PC) including the posterior communicating artery (PCOM) in 76%. Sixty-six percent of the aneurysms were smaller than 7 mm, 18% ranged between 7 and 9.9 mm, 14% were between 10 and 19.9 mm, and 2% were larger than 20 mm. European population, aneurysm size < 7 mm, and age < 75 years scored with 0 point in the PHASES study occurred most frequently in our series. The distribution of the aneurysm site to the anterior and posterior circulation scored with 4 points occurred most frequently. Considering the 5-year risk of rupture, 70% of our patient collective would have an estimated risk of < 2%. Interestingly, 70% of the patients with aneurysmal SAH had a low risk profile and would have a low risk of rupture according to the PHASES score in our series. This observation underlines the discrepancy of the estimated low risk of rupture for UIAs in young and healthy patients and the obvious fact the majority of the SAH patients are actually young with low risk factors. Parameters beyond the features of the PHASES score are needed to determine the risk of rupture of intracranial aneurysms.

CCM1/KRIT1 mutation in monozygotic twins of a polyzygotic triplet birth: genetic, clinical and radiological characteristics.

Cerebral cavernous malformations are focal vascular lesions of the brain, occurring sporadically or as an autosomal dominant familial form. The genetic background influences not only the clinical course but also patients' consultation and the indication to treat. We here present the rare case of monozygotic male twins of a polyzygotic triplet birth, carrying a CCM1 mutation, inherited from the mother. Both twins showed an identical site and size of a large frontobasal lesion. The genetic segregation and the clinical course in affected family members are presented and discussed.

Brain arteriovenous malformations: implications of CEACAM1-positive inflammatory cells and sex on hemorrhage.

Brain arteriovenous malformations (bAVMs) are severe conditions which, upon rupture, cause debilitating neurological deficits and even death. The exact cellular and molecular mechanisms associated with bAVM rupture are currently unclear. The objective of this study was to explore the potential role of CEA-related cell adhesion molecule-1 (CEACAM1) in bAVM pathophysiology. Expression and localization of CEACAM1 were assessed immunohistochemically in tissue microarrays from bAVM patients (n = 60). The association of CEACAM1 with clinical parameters was analyzed with Spearman's rank correlation coefficient and chi-square test. The predictive value of CEACAM1 was tested using logistic regression analysis. CEACAM1 was highly expressed in tissue-infiltrating neutrophil granulocytes. High levels of CEACAM1-positive cells were associated with bAVM rupture (hemorrhage), but not with arteriovenous malformation (AVM) size, preoperative embolization, or seizure. This association was significant (p = 0.029, chi-square) in male but not in female patients, and high CEACAM1-positive immune infiltration showed predictive significance for hemorrhage in male bAVM patients only (OR = 6.50, 95 % CI 1.09-38.63, p = 0.040). Within the ruptured bAVM group, patients with a short hemorrhage to surgery (HTS) time interval had higher levels of CEACAM1 immune infiltration than patients with long HTS. This decrease in the levels of CEACAM1 immune infiltration between the HTS short and HTS long groups was, however, significant only in female patients (p = 0.022, chi-square). Our findings substantiate the role of inflammation in the pathophysiology of bAVM and suggest the presence of sexual dimorphism in this disease.

Is an Elevated Preoperative CRP Level a Predictive Factor for Wound Healing Disorders following Lumbar Spine Surgery?

Postoperative wound infections are a prevalent concern among the hospital-associated infections in Europe, leading to prolonged hospital stays, increased morbidity and mortality, and substantial patient burdens. Addressing the root causes of this complication is crucial, especially given the rising number of spine surgeries due to aging populations. METHODS: A retrospective analysis was conducted on a cohort of 3019 patients who underwent lumbar spine surgery over a decade in our department. The study aimed to assess the predictors of wound healing disorders, focusing on laboratory values, particularly inflammatory parameters. RESULTS: Of the 3019 patients, 2.5% (N = 74) experienced deep or superficial wound healing disorders, showing the significant correlation between C-reactive protein (CRP) levels and these disorders (p = 0.004). A multivariate analysis identified several factors, including age, sex, hypertension, diabetes, cardiac comorbidity, surgical duration, dural injury, and blood loss, as being correlated with wound healing disorders. CONCLUSION: Demographic factors, pre-existing conditions, and perioperative variables play a role in the occurrence of adverse effects related to wound healing disorders. Elevated CRP levels serve as an indicator of increased infection risk, though they are not a definitive diagnostic tool for wound healing disorders.

Late Relapse of Previous Pulmonary Cryptococcosis With Symptoms Resembling Cerebral Infarction: A Case Report.

Cryptococcosis, an infection caused by Cryptococcus neoformans and Cryptococcus gattii, predominantly targets the central nervous system (CNS) in patients with AIDS but is not limited to this group. The disease can also occur in individuals with various immunosuppressive conditions, frequently involving the brain or lungs. Cryptococcal meningitis (CM) is the most common form of fungal meningoencephalitis, leading to intracerebral infections, cerebral infarction, or hydrocephalus. The clinical presentation of CM is nonspecific, and imaging features can vary significantly. This case report presents a patient with cerebral infarction, who was HIV-negative but had been on long-term cortisone therapy. Notably, the patient had a history of pulmonary cryptococcosis 15 years prior to cerebral involvement. When initially at our clinic, histology and culture results from brain biopsies were negative and the earlier pulmonary cryptococcosis history was unknown. Subsequently, cryptococcal antigen was detected in both serum and cerebrospinal fluid (CSF), and C. neoformans was cultivated from CSF. This case highlights the critical importance of maintaining a high index of suspicion for CM, particularly in patients with a history of previous cryptococcal infections, and it also demonstrates the possibility of false-negative brain biopsy results due to secondary vascular events associated with CM.

Intracranial Aneurysms and Cerebral Small Vessel Disease: Is There an Association between Large- and Small-Artery Diseases?

Background/Objectives: Intracranial aneurysms (IAs) may be connected to interactions between large and small intracranial vessels. We aimed to investigate the association between IAs and cerebral small-vessel disease (CSVD) and assess CSVD impact on IA patient management. Methods: This retrospective study analyzed clinical data and MRI features of CSVD in 192 subarachnoid hemorrhage (SAH) patients: 136 with incidental IA, 147 with severe CSVD without SAH/IA, and 50 controls without SAH, IA, or severe CSVD. MRI assessments followed the Standards for Reporting Vascular Changes on Neuroimaging (STRIVE), with a total burden of small-vessel disease (TBSVD) score calculated. Statistical analyses included forward selection and binary logistic regression. Results: TBSVD differed significantly across groups (p < 0.001), except between SAH and IA groups (p = 0.8). Controls had the lowest TBSVD (1.00; 1.22 ± 0.996), followed by SAH (2.00; 2.08 ± 1.013) and IA groups (2.00; 2.04 ± 1.141), with the highest in the CSVD group (1.00; 1.22 ± 0.996). White-matter hyperintensity (WMH) patterns varied with IA rupture status (p = 0.044); type A was prevalent in SAH patients and type D in the IA group. Incorporating MRI CSVD features and TBSVD into risk assessments did not enhance IA prediction or outcome models. Conclusions: IA patients exhibit a higher CSVD burden than controls, suggesting a link between small and large intracranial vessels. WMH patterns distinguish between ruptured and unruptured IA patients, offering potential markers for IA rupture risk assessment and signaling a paradigm shift in understanding IAs and CSVD.

Virtual Reality vs Phantom Model: Benefits and Drawbacks of Simulation Training in Neurosurgery.

BACKGROUND AND OBJECTIVES: Traditional neurosurgical education has relied heavily on the Halstedian "see one, do one, teach one" approach which is increasingly perceived as inefficient in contemporary settings marked by a steady decline in surgical caseload. In recent years, simulation training has emerged as an effective and accessible training alternative. To date, however, there is no standardized criterion pertaining to the quality and implementation of simulators in neurosurgical education and training. This research aims to compare the efficacy of virtual reality (VR) and Phantom-based simulation training in the context of neurosurgical skill acquisition, with a focus on middle cerebral artery aneurysm clipping. METHODS: An immersive VR clipping tool and a haptic clipping simulator incorporating 3-dimensional printing, additive manufacturing, and rheological analyses were developed. Twenty-two participants, comprising 12 medical students, 6 neurosurgical residents, and 4 experienced neurosurgeons, tested and evaluated both simulators for face and content validity. Construct and predictive validity of the simulators were assessed using an objective structured assessment scale for aneurysm clipping, measuring participants' performances and progress. RESULTS: Both modalities were deemed highly advantageous for educational purposes. Objective evaluations, however, revealed measurable differences in usability, efficacy, and transferability of the learned skills with VR excelling in procedural planning and visualization while Phantom simulation being noticeably superior in conveying surgical skills. CONCLUSION: Simulation training can accelerate the neurosurgical learning curve. The results of this study highlight the importance of establishing standardized criteria for the implementation and assessment of simulation modalities, ensuring consistent quality and efficacy in neurosurgical education.

Lactococcus garviae in Lumbar Spondylodiscitis With Spinal Epidural Abscess Causing Paraparesis: A Case Report.

Spinal epidural abscess (SEA) can lead to a subacute onset of neurological deficits of the extremities and is commonly accompanied by spondylodiscitis if located anterior to the dura. Lactococcus garviae is a fish pathogen that is occasionally found in poultry, cattle, and swine. It is a rare cause of infection in humans. Most commonly it is associated with endocarditis. Until 2019, less than 30 cases of human Lactoccous garviae infection have been published. To the best of our knowledge, we present the second reported case of SEA with spondylodiscitis caused by Lactococcus garviae. How Lactococcus garviae caused SEA, remains unclear in this case.

The Roles of AGTRAP, ALKBH3, DIVERSIN, NEDD8 and RRM1 in Glioblastoma Pathophysiology and Prognosis.

This study determined the expression of five novel biomarker candidates in IDH wild-type glioblastoma (GBM) tissues compared to non-malign brain parenchyma, as well as their prognostic relevance for the GBM patients' outcomes. The markers were analysed by immunohistochemistry in tumour tissues (n = 186) and healthy brain tissues (n = 54). The association with the patients' overall survival (OS) and progression-free survival (PFS) was assessed by Kaplan-Meier and log-rank test. The prognostic value of the markers was determined using multivariate Cox proportional hazard models. AGTRAP, DIVERSIN, cytoplasmic NEDD8 (NEDD8c) and RRM1 were significantly overexpressed in tumour tissues compared to the healthy brain, while the opposite was observed for ALKBH3. AGTRAP, ALKBH3, NEDD8c and RRM1 were significantly associated with OS in univariate analysis. AGTRAP and RRM1 were also independent prognostic factors for OS in multivariate analysis. For PFS, only AGTRAP and NEDD8c reached significance in univariate analysis. Additionally, AGTRAP was an independent prognostic factor for PFS in multivariate models. Finally, combined analysis of the markers enhanced their prognostic accuracy. The combination AGTRAP/ALKBH3 had the strongest prognostic value for the OS of GBM patients. These findings contribute to a better understanding of the GBM pathophysiology and may help identify novel therapeutic targets in this type of cancer.

Sex Differences in Intracranial Aneurysms: A Matched Cohort Study.

Background: Aneurysmal subarachnoid hemorrhage (SAH) predominantly affects women, accounting for 65% of cases. Women have a 1.3 times higher relative risk than men, with the incidence rising particularly in women aged 55-85 years. Women also have a higher prevalence of unruptured intracranial aneurysms (IAs), especially after the age of 50 years, and are at greater risk of aneurysm growth and rupture. This study aimed to isolate the influence of sex on rupture rate, bleeding severity, functional outcomes, and complications by using a matched cohort, while also examining the impact of sex on aneurysm localization and multiplicity. Methods: We utilized a retrospectively collected database of 300 patients with 511 IAs. Inclusion criteria included the availability of clinical data and 3D angiography for semi-automatic reconstruction of IA morphology. Female patients and their IA were matched with male patients according to clinical parameters and 21 morphological characteristics using an interactive visual exploration tool for multidimensional matching. Results: Contrary to previously published results, our study found no significant sex differences in rupture rates or vasospasm rates between male and female patients. The severity of SAH, functional outcomes, and complications such as hydrocephalus were also similar in women and men. However, women exhibited a higher prevalence of multiple aneurysms and distinct localization patterns. Conclusions: This study underscores the complex role of sex in IA development and rupture. Although sex-specific biological factors influence aneurysm characteristics, they do not necessarily translate into differences in clinical outcomes. Further research is needed to explore these factors and their impact on aneurysm development and management.

Impact of Perioperative Acetylsalicylic Acid (ASA) Administration on Postoperative Intracranial Hemorrhage (pICH) and Thromboembolic Events in Patients with Intracranial Meningiomas.

Background: In routine medical practice, patients are increasingly using ASA for primary and secondary prevention. Although many of these patients discontinue ASA prior to elective intracranial surgery, there are limited data to support whether perioperative ASA use raises the risk of postoperative hemorrhage. This study aimed to investigate the implications of continuing or stopping ASA around the time of surgery in patients with intracranial meningiomas, focusing on postoperative hemorrhage and thromboembolic events. Methods: For this purpose, medical records and radiological images of 1862 patients who underwent cranial neurosurgical procedures for brain tumors over a decade at our neurosurgical institute were retrospectively analyzed. The risk of postoperative hemorrhage was evaluated by comparing meningioma patients who received ASA treatment with those who did not. Furthermore, we investigated other factors that influence postoperative hemorrhage and thromboembolic events, particularly in patients receiving ASA treatment. Results: A total of 422 patients diagnosed with meningiomas underwent surgical intervention. Among the patients who received ASA preoperatively, 4 out of 46 (8.69%) experienced postoperative hemorrhage requiring surgical intervention, whereas the same complication occurred in only 4 out of 376 patients (1.06%) in the non-ASA group (p = 0.007). There was no significant difference in the incidence of thromboembolic events between the two groups. Conclusions: Our analysis revealed an increased risk of postoperative hemorrhage in patients using ASA.

Enlarged tumefactive perivascular, or Virchow-Robin, spaces and hydrocephalus: do we need to treat? Illustrative cases.

BACKGROUND: Perivascular spaces (PVSs) are spaces in brain parenchyma filled with interstitial fluid surrounding small cerebral vessels. Massive enlargements of PVSs are referred to as "giant tumefactive perivascular spaces" (GTPVSs), which can be classified into three types depending on their localization. These lesions are rare, predominantly asymptomatic, and often initially misinterpreted as cystic tumor formations. However, there are several reported cases in which GTPVSs have induced neurological symptoms because of their size, mass effect, and location, ultimately leading to obstructive hydrocephalus necessitating neurosurgical intervention. Presented here are three diverse clinical presentations of GTPVS. OBSERVATIONS: Here, the authors observed an asymptomatic case of type 1 GTPVS and two symptomatic cases of type 3 GTPVS, one causing local mass effect and the other hydrocephalus. LESSONS: GTPVSs are mostly asymptomatic lesions. Patients without symptoms should be closely monitored, and biopsy is discouraged. Hydrocephalus resulting from GTPVS necessitates surgical intervention. In these cases, third ventriculostomy, shunt implantation, or direct cyst fenestration are surgical options. For patients presenting with symptoms from localized mass effect, a thorough evaluation for potential neurosurgical intervention is imperative. Follow-up in type 3 GTPVS is recommended, particularly in untreated cases. Given the infrequency of GTPVS, definitive guidelines for neurosurgical treatment and subsequent follow-up remain elusive.

Postoperative Acute Intracranial Hemorrhage and Venous Thromboembolism in Patients with Brain Metastases Receiving Acetylsalicylic Acid Perioperatively.

Cranial operations are associated with a high risk of postoperative intracranial hemorrhage (pICH) and venous thromboembolic events, along with increased mortality and morbidity. With the use of acetylsalicylic acid (ASA) for prophylaxis becoming more prevalent, the risk of bleeding when ASA is administered preoperatively is unknown, as are the effects of discontinuation upon the occurrence of thromboembolic events, especially in societies with aging demographics. To address these questions, a retrospective analysis was performed using medical records and radiological images of 1862 patients subjected to brain tumor surgery over a decade in our department. The risk of pICH was compared in patients with metastases receiving ASA treatment versus patients not receiving ASA treatment. The occurrence of venous thromboembolic events after surgery was also evaluated. The study group consisted of 365 patients with different types of brain metastases. In total, 20 patients suffered pICH and 7 of these were associated with clinical neurological deterioration postoperatively. Of the 58 patients who took ASA preoperatively, 2 patients experienced pICH, compared with 5 patients in the non-ASA impact group (p = 0.120). Patients who took ASA were not at significantly higher risk of pICH and therefore a worse outcome compared to the group without ASA. Therefore, these data suggest that in patients at high cardiovascular risk, ASA can be safely continued during elective brain tumor surgery.

Extravascular optical coherence tomography of cerebral vessel walls in vivo.

PURPOSE: Evaluation of extravascular, microscope integrated OCT (iOCT) as an in vivo imaging modality of cerebral blood vessels and as an intraoperative imaging method. METHODS: Microscope integrated optical coherence tomography of major cerebral arteries (n = 13) and superficial sylvian veins (n = 5) and one incidental cerebral vasospasm (n = 1) in (n = 10) patients. Post procedural analysis of OCT volume scans, microscopic images and videos during the time of scan as well as measurements of the diameter of vessel walls and its layers with an accuracy of 7.5 µm. RESULTS: iOCT was feasible during vascular microsurgical procedures. In all scanned arteries a clear delineation of the physiological three layered vessel wall composition could be achieved. Pathological arteriosclerotic alterations of cerebral artery walls could precisely be demonstrated. Major superficial cortical veins conversely presented a mono layered composition. First in vivo measurements of vascular mean diameters were possible. Cerebral artery walls showed a diameter of 296 µm, tunica externa 78 µm, media 134 µm and interna 84 µm. CONCLUSION: For the first time the microstructural composition of cerebral blood vessels could be illustrated in vivo. Due to an outstanding spatial resolution a clear definition of physiological and pathological characteristics was possible. Therefore, microscope integrated optical coherence tomography holds promise for basic research in the field of cerebrovascular arteriosclerotic diseases and for intraoperative guidance during microvascular surgery.

VR-based training of craniotomy for intracranial aneurysm surgery.

PURPOSE: Intracranial aneurysms can be treated micro-surgically. This procedure involves an appropriate head position of the patient and a proper craniotomy. These steps enable a proper access, facilitating the subsequent steps. To train the access planning process, we propose a VR-based training system. METHOD: We designed and implemented an immersive VR access simulation, where the user is surrounded by a virtual operating room, including medical equipment and virtual staff. The patient's head can be positioned via hand rotation and an arbitrary craniotomy contour can be drawn. The chosen access can be evaluated by exposing the aneurysm using a microscopic view. RESULTS: The evaluation of the simulation took place in three stages: testing the simulation using the think-aloud method, conducting a survey and examining the precision of drawing the contour. Although there are differences between the virtual interactions and their counterparts in reality, the participants liked the immersion and felt present in the operating room. The calculated surface dice similarity coefficient, Hausdorff distance and feedback of the participants show that the difficulty of drawing the craniotomy is appropriate. CONCLUSION: The presented training simulation for head positioning and access planning benefits from the immersive environment. Thus, it is an appropriate training for novice neurosurgeons and medical students with the goal to improve anatomical understanding and to become aware of the importance of the right craniotomy hole.