3D Printing of the Cerebral Vasculature Exceptionally using Freeware: A Quick and Easy Guide Technical Note

High-resolution 3D reconstructions of the cerebral vasculature are essential for preoperative planning of complex interventions in vascular neurosurgery. Quick-segmentation algorithms provided by expensive radiology applications often result in unsatisfactory 3D reconstructions. Here we show how to quickly segment and print a detailed 3D model of the cerebral vasculature without extensive knowledge in 3D modeling. Exceptionally using freeware, the total costs for the generation of a real size model of the circle of Willis are less than $10. The 3D models will be particularly valuable during preoperative planning and for patient information

Rôles des aquaporines dans le cerveau

Il y a maintenant plus d’une dizaine d’années que l’aquaporine 1 (AQP1) a été mise en évidence et clonée à partir des globules rouges. Cette découverte majeure pour le monde du vivant a été récompensée en 2003 par le Prix Nobel de Chimie décerné au Professeur Peter Agre. Les aquaporines (AQP) sont des canaux à eau. Cette famille de protéines est composée actuellement de onze sous-types différents exprimés chez les mammifères. Les trois AQP principales caractérisées dans le cerveau des mammifères sont l’AQP1, l’AQP4 et l’AQP9. Les travaux récents montrent que ces canaux sont impliqués dans différentes fonctions physiologiques. L’AQP1 serait importante dans la formation du liquide céphalorachidien, tandis que l’AQP4 aurait un rôle dans l’homéostasie de l’eau et de la pression osmotique du tissu nerveux. L’AQP9 serait impliquée dans le métabolisme énergétique. En condition physiologique, le niveau d’expression de ces AQP est finement régulé. Dans différentes maladies du système nerveux, le niveau d’expression de ces canaux est modifié, ce qui peut avoir des conséquences sur la formation de l’oedème cérébral en modifiant la perméabilité à l’eau. Actuellement, le rôle de chacune de ces AQP dans ce phénomène n’est pas encore compris. L’AQP4 semble avoir un rôle très important dans le développement de l’oedème après un traumatisme crânien, une lésion ou un accident vasculaire cérébral. Une meilleure compréhension des mécanismes de régulation des AQP permettra d’envisager de nouvelles stratégies thérapeutiques pour prévenir la formation de l’oedème cérébral. La découverte récente de l’AQP9 dans les neurones catécholaminergiques a modifié la vision du rôle des AQP dans le système nerveux, avec une implication possible de cette dernière dans le métabolisme énergétique cérébral.It is now over 10 years ago that aquaporin 1 (AQP1) was discovered and cloned from the red blood cells, and in 2003 the Nobel price in Chemistry was awarded to Pr. Peter Agre for his work on AQPs, highlighting the importance of these proteins in life sciences. AQPs are water channels. To date this protein family is composed of 11 sub-types in mammalians. Three main AQPs described in the mammalian brain are AQP1, AQP4 and AQP9. Several recent studies have shown that these channels are implicated in numerous physiological functions. AQP1 has a role in cerebrospinal fluid formation, whereas AQP4 is involved in water homeostasis and extracellular osmotic pressure in brain parenchyma. AQP4 seems also to have an important function in oedema formation after brain trauma or brain ischemia. AQP9 is implicated in brain energy metabolism. The level of expression of each AQP is highly regulated. After a trauma or an ischemia perturbation of the central nervous system, the level of expression of each AQP is differentially modified, resulting in facilitating oedema formation. At present, the exact role of each AQP is not yet determined. A better understanding of the mechanisms of AQP regulation should permit the development of new pharmacological strategies to prevent oedema formation. AQP9 has been recently specifically detected in the catecholaminergic neurons of the brain. This new result strengthens the hypothesis that the AQPs are not only water channels, but that some AQPs may play a role in energy metabolism as metabolite channels

Aquaporins in the brain: from aqueduct to "multi-duct”

The aquaporin channel family was first considered as a family of water channels, however it is now clear that some of these channels are also permeable to small solutes such glycerol, urea and monocarboxylates. In this review, we will consider AQP4 and AQP9 expressed in the rodent brain. AQP4 is present on astrocytic end-feet in contact with brain vessels and could be involved in ionic homeostasis. However, AQP4 may also be involved in cell adhesion. AQP4 expression is highly modified in several brain disorders and it can play a key role in the cerebral edema formation. However, the exact role of AQP4 in edema formation is still debated. Recently, AQP4 has been shown to be also involved in astrocyte migration during glial scar formation. AQP9 is expressed in astrocytes and in catecholaminergic neurons. Two isoforms of AQP9 are expressed in brain cells, the shortest isoform is localized in the inner membrane of mitochondria and the longest in the cell membrane. The level of expression of AQP9 is negatively regulated by high concentrations of insulin. Taken together, these results suggest that AQP9 could be involved in brain energy metabolism. The induction of AQP9 in astrocytes is observed with time after stroke onset suggesting participation in the clearance of excess lactate in the extracellular space. These recent exciting results suggest that AQPs may not only be involved in water homeostasis in the brain but could also participate in other important physiological function

Optimization of signal-to-noise ratio in short-duration SEP recordings by variation of stimulation rate

Objective: The intraoperative averaging of the somatosensory evoked potential (SEP) requires reliable recordings within the shortest possible duration. We here systematically optimized the repetition rate of stimulus presentation. Methods: We recorded medianus and tibial nerve SEP during 22 surgeries and varied the rate of stimulus presentation between 2.7 Hz and 28.7 Hz. We randomly sampled a number of sweeps corresponding to recording durations up to 20 s and calculated the signal-to-noise ratio (SNR). Results: For the medianus nerve at 5 s recording duration, SEP stimulation rate at 12.7 Hz obtained the highest median SNR = 22.9 for the N20, which was higher than for rate 4.7 Hz (p = 1.5e-4). When increasing the stimulation rate, latency increased and amplitude decayed for cortical but not for peripheral recording sites. For the tibial nerve, the rate 4.7 Hz achieved the highest SNR for all durations. Conclusions: We determined the time-dependence of SNR for N20 and elucidated the underlying physiology. For short recordings, rapid reduction of noise through averaging at high stimulation rate outweighs the disadvantage of smaller amplitude. Significance: For a short duration of medianus nerve SEP recording only, it may be advantageous to stimulate with a repetition rate of 12.7 Hz. Keywords: Erb’s point; High frequency oscillation; Intraoperative neuromonitoring; Neurosurgery; Peripheral nerve conduction; Stimulation frequency

Posterior auricular artery as an alternative donor vessel for extracranial-intracranial bypass surgery

Background: Sometimes the superficial temporal artery (STA) is not available for an extracranial-intracranial (EC-IC) bypass procedure. An alternative vessel for an EC-IC bypass is the posterior auricular artery (PAA) if it extends to the temporoparietal area with a diameter large enough. We assessed the prevalence of an appropriate PAA as an alternative donor vessel and report three illustrative cases in which the PAA was used for EC-IC bypass surgery. Methods: A literature search was performed on the use of the PAA as a donor vessel for bypass surgery. Secondly, a prospective database of bypass surgeries was reviewed to calculate the prevalence of a PAA with a diameter of at least 1mm in the parietotemporal area. Finally, three illustrative cases are reported that describe various indications for the revascularisation procedures with their clinical, surgical and imaging features. Results: Two articles have previously described the use of the PAA for bypass surgery and their results are summarised. The prevalence of a PAA that would be appropriate for an EC-IC bypass in patients with intracranial vascular pathology is 5.7%. The presented cases demonstrate that the PAA can be successfully used for EC-IC bypass surgery with good flow velocities and patency. Conclusions: The PAA is a rarely described as an appropriate donor vessel for an EC-IC bypass. Its prevalence is 5.7% and it can successfully be used as an alternative donor vessel. The awareness among cerebrovascular surgeons about the presence of a PAA and knowledge about its anatomy may be valuable

The History of Stereotactic and Functional Neurosurgery in Zurich

Zurich's stereotactic and functional neurosurgery (SFN) has a rich legacy beginning with the studies of the physiologist and Nobel prize winner Walter Rudolf Hess over the efforts of the neurosurgeons Hugo Krayenbühl and Mahmut Gazi Yaşargil up to the work of the functional surgeon Jean Siegfried and the modern era of SFN and neuromodulation. A comprehensive review and synthesis of data acquired from institutional archives and personal interviews as well as from journal articles, included references, proceedings of scientific meetings, staff biographies, and book publications were performed to gain insight into Zurich's long journey toward contemporary SFN and to highlight its stereotactic and functional history with special reference to the development of deep brain stimulation. Zurich's history of medicine includes decisive moments for the fundamentals and development of SFN. After an early period of innovation and research later followed by a long time of clinical application during the 20th century, it became quieter at the turn of the century. Since the end of the 2000s, an impressive renaissance occurred in Zurich that revived its rich SFN tradition

How we do it: the Zurich Microsurgery Lab technique for placenta preparation

BACKGROUND Perfused placentas provide an excellent and accessible model for microvascular dissection, microsuturing and microanastomosis training - particularly in the early microsurgical learning curve. This way, a significant amount of live animals can be spared. METHOD We present the Zurich Microsurgery Lab protocol, detailing steps for obtaining, selecting, cleaning, flushing, cannulating, and preserving human placentas - as well as microsurgical training examples - in a tried-and-true, safe, cost-effective, and high-yield fashion. CONCLUSION Our technique enables highly realistic microsurgical training (microdissection, microvascular repair, microanastomosis) based on readily available materials. Proper handling, preparation, and preservation of the perfused placenta models is key

DeepEOR: automated perioperative volumetric assessment of variable grade gliomas using deep learning

PURPOSE Volumetric assessments, such as extent of resection (EOR) or residual tumor volume, are essential criterions in glioma resection surgery. Our goal is to develop and validate segmentation machine learning models for pre- and postoperative magnetic resonance imaging scans, allowing us to assess the percentagewise tumor reduction after intracranial surgery for gliomas. METHODS For the development of the preoperative segmentation model (U-Net), MRI scans of 1053 patients from the Multimodal Brain Tumor Segmentation Challenge (BraTS) 2021 as well as from patients who underwent surgery at the University Hospital in Zurich were used. Subsequently, the model was evaluated on a holdout set containing 285 images from the same sources. The postoperative model was developed using 72 scans and validated on 45 scans obtained from the BraTS 2015 and Zurich dataset. Performance is evaluated using Dice Similarity score, Jaccard coefficient and Hausdorff 95%. RESULTS We were able to achieve an overall mean Dice Similarity Score of 0.59 and 0.29 on the pre- and postoperative holdout sets, respectively. Our algorithm managed to determine correct EOR in 44.1%. CONCLUSION Although our models are not suitable for clinical use at this point, the possible applications are vast, going from automated lesion detection to disease progression evaluation. Precise determination of EOR is a challenging task, but we managed to show that deep learning can provide fast and objective estimates

Mortality in Patients with Brainstem Cavernous Malformations

OBJECTIVE Brainstem cavernous malformations (BSCM)-associated mortality has been reported up to 20% in patients managed conservatively, whereas postoperative mortality rates range from 0 to 1.9%. Our aim was to analyze the actual risk and causes of BSCM-associated mortality in patients managed conservatively and surgically based on our own patient cohort and a systematic literature review. METHODS Observational, retrospective single-center study encompassing all patients with BSCM that presented to our institution between 2006 and 2018. In addition, a systematic review was performed on all studies encompassing patients with BSCM managed conservatively and surgically. RESULTS Of 118 patients, 54 were treated conservatively (961.0 person years follow-up in total). No BSCM-associated mortality was observed in our conservatively as well as surgically managed patient cohort. Our systematic literature review and analysis revealed an overall BSCM-associated mortality rate of 2.3% (95% CI: 1.6-3.3) in 22 studies comprising 1,251 patients managed conservatively and of 1.3% (95% CI: 0.9-1.7) in 99 studies comprising 3,275 patients with BSCM treated surgically. CONCLUSION The BSCM-associated mortality rate in patients managed conservatively is almost as low as in patients treated surgically and much lower than in frequently cited reports, most probably due to the good selection nowadays in regard to surgery