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Yuichi Murayama, Soichiro Fujimura, Tomoaki Suzuki and Hiroyuki Takao

OBJECTIVE

The authors reviewed the clinical role of computational fluid dynamics (CFD) in assessing the risk of intracranial aneurysm rupture.

METHODS

A literature review was performed to identify reports on CFD assessment of aneurysms using PubMed. The usefulness of various hemodynamic parameters, such as wall shear stress (WSS) and the Oscillatory Shear Index (OSI), and their role in aneurysm rupture risk analysis, were analyzed.

RESULTS

The authors identified a total of 258 published articles evaluating rupture risk, growth, and endovascular device assessment. Of these 258 articles, 113 matching for CFD and hemodynamic parameters that contribute to the risk of rupture (such as WSS and OSI) were identified. However, due to a lack of standardized methodology, controversy remains on each parameter’s role.

CONCLUSIONS

Although controversy continues to exist on which risk factors contribute to predict aneurysm rupture, CFD can provide additional parameters to assess this rupture risk. This technology can contribute to clinical decision-making or evaluation of efficacy for endovascular methods and devices.

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Sirin Gandhi, Tsinsue Chen, Justin R. Mascitelli, Claudio Cavallo, Mohamed A. Labib, Michael J. Lang and Michael T. Lawton

This video illustrates a contralateral supracerebellar transtentorial (cSCTT) approach for resection of a ruptured thalamic cavernous malformation in a 56-year-old woman with progressive right-sided homonymous hemianopsia. The patient was placed in the sitting position, and a torcular craniotomy was performed for the cSCTT approach. The lesion was resected completely. Postoperatively, the patient had intact motor strength and baseline visual field deficits with moderate right-sided paresthesias. The cSCTT approach maximizes the lateral surgical reach without the cortical transgression seen with alternative transcortical routes.1 Contralaterality is a defining feature, with entry of the neurosurgeon’s instruments from the craniotomy edge of the craniotomy, contralateral to the lesion, allowing access to the lateral aspect of the lesion. The sitting position facilitates gravity-assisted cerebellar retraction and enhances the superior reach of this approach (Used with permission from Barrow Neurological Institute, Phoenix, Arizona).

The video can be found here: https://youtu.be/lqB9mu_T8NQ.

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Florian Roser, Luigi Rigante and Mohamed Samy Elhammady

Procedures on cavernous malformations of the brainstem are challenging due to their eloquent location. This accounts especially for recurrent cavernomas as surgical scars, adhesions, and functional shift might have occurred since primary surgery. We report on a 38-year-old female patient with a large recurrent brainstem cavernoma, who underwent previous successful surgery and experienced recurrent bleeding about 2 years later. She harbored a large associated developmental venous anomaly (DVA) traversing the cavernoma through the midline of the brainstem. In order to visualize complete resection and preservation of the DVA at the same time, endoscopic-assisted resection within the brainstem after decompression in the semisitting position was performed.

The video can be found here: https://youtu.be/K1p-Sx7jUpA.

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Lucas Ramos Lima, Jarbas Carvalhais Reis, Gerival Vieira Junior, Tiago Fraga Vieira, Lucidio Duarte de Souza Filho, Tiago Silva e Carvalho, Fabricio Nery Marques, Ramon Souza Lago and Thiago Vinícius Muniz Santana

Symptomatic cavernous malformations in the ventral region of the pons are difficult to access surgically. The authors present a case of a 46-year-old woman with a 10-year history of sudden and transitory diplopia and right hemiparesis, followed by five more episodes of mild right hemiparesis. Brain MRI showed a 2.6-cm cavernous malformation in the pons with an exophytic portion in the prepontine cistern. The patient underwent an endoscopic endonasal transclival approach for a complete resection of the lesion. CSF leak was noted and corrected on the sixth postoperative day. The patient progressed with complete motor deficit recovery.

The video can be found here: https://youtu.be/ePgpyij2Wpo.

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Matteo Zoli, Giacomo Sollini, Sofia Asioli, Clarissa Ann Elisabeth Gelmi, Angelo Gianluca Corradini, Ernesto Pasquini and Diego Mazzatenta

We present the case of a 47-year-old man with left exophthalmus. MRI showed a left intraorbital intraconal cavernous malformation, located in the superoesternal quadrant and medially displacing the optic nerve. An endoscopic transpalpebral approach was performed and total removal was achieved after dissection of the lesion from the optic nerve and other orbital structures. Pathology confirmed the diagnosis of cavernous malformation. The patient was discharged neurologically intact on the second postoperative day free of complications. Follow-up MRI demonstrated radical resection of the cavernoma and resolution of the exophthalmus with an excellent esthetic result.

The video can be found here: https://youtu.be/o1a1tneZ6qk.

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Dallas L. Sheinberg, David J. McCarthy, Omar Elwardany, Jean-Paul Bryant, Evan Luther, Stephanie H. Chen, John W. Thompson and Robert M. Starke

Endothelial cell (EC) dysfunction is known to contribute to cerebral aneurysm (CA) pathogenesis. Evidence shows that damage or injury to the EC layer is the first event in CA formation. The mechanisms behind EC dysfunction in CA disease are interrelated and include hemodynamic stress, hazardous nitric oxide synthase (NOS) activity, oxidative stress, estrogen imbalance, and endothelial cell-to-cell junction compromise. Abnormal variations in hemodynamic stress incite pathological EC transformation and inflammatory zone formation, ultimately leading to destruction of the vascular wall and aneurysm dilation. Hemodynamic stress activates key molecular pathways that result in the upregulation of chemotactic cytokines and adhesion molecules, leading to inflammatory cell recruitment and infiltration. Concurrently, oxidative stress damages EC-to-EC junction proteins, resulting in interendothelial gap formation. This further promotes leukocyte traffic into the vessel wall and the release of matrix metalloproteinases, which propagates vascular remodeling and breakdown. Abnormal hemodynamic stress and inflammation also trigger adverse changes in NOS activity, altering proper EC mediation of vascular tone and the local inflammatory environment. Additionally, the vasoprotective hormone estrogen modulates gene expression that often suppresses these harmful processes. Crosstalk between these sophisticated pathways contributes to CA initiation, progression, and rupture. This review aims to outline the complex mechanisms of EC dysfunction in CA pathogenesis.

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Felicitas J. Detmer, Sara Hadad, Bong Jae Chung, Fernando Mut, Martin Slawski, Norman Juchler, Vartan Kurtcuoglu, Sven Hirsch, Philippe Bijlenga, Yuya Uchiyama, Soichiro Fujimura, Makoto Yamamoto, Yuichi Murayama, Hiroyuki Takao, Timo Koivisto, Juhana Frösen and Juan R. Cebral

OBJECTIVE

Incidental aneurysms pose a challenge for physicians, who need to weigh the rupture risk against the risks associated with treatment and its complications. A statistical model could potentially support such treatment decisions. A recently developed aneurysm rupture probability model performed well in the US data used for model training and in data from two European cohorts for external validation. Because Japanese and Finnish patients are known to have a higher aneurysm rupture risk, the authors’ goals in the present study were to evaluate this model using data from Japanese and Finnish patients and to compare it with new models trained with Finnish and Japanese data.

METHODS

Patient and image data on 2129 aneurysms in 1472 patients were used. Of these aneurysm cases, 1631 had been collected mainly from US hospitals, 249 from European (other than Finnish) hospitals, 147 from Japanese hospitals, and 102 from Finnish hospitals. Computational fluid dynamics simulations and shape analyses were conducted to quantitatively characterize each aneurysm’s shape and hemodynamics. Next, the previously developed model’s discrimination was evaluated using the Finnish and Japanese data in terms of the area under the receiver operating characteristic curve (AUC). Models with and without interaction terms between patient population and aneurysm characteristics were trained and evaluated including data from all four cohorts obtained by repeatedly randomly splitting the data into training and test data.

RESULTS

The US model’s AUC was reduced to 0.70 and 0.72, respectively, in the Finnish and Japanese data compared to 0.82 and 0.86 in the European and US data. When training the model with Japanese and Finnish data, the average AUC increased only slightly for the Finnish sample (to 0.76 ± 0.16) and Finnish and Japanese cases combined (from 0.74 to 0.75 ± 0.14) and decreased for the Japanese data (to 0.66 ± 0.33). In models including interaction terms, the AUC in the Finnish and Japanese data combined increased significantly to 0.83 ± 0.10.

CONCLUSIONS

Developing an aneurysm rupture prediction model that applies to Japanese and Finnish aneurysms requires including data from these two cohorts for model training, as well as interaction terms between patient population and the other variables in the model. When including this information, the performance of such a model with Japanese and Finnish data is close to its performance with US or European data. These results suggest that population-specific differences determine how hemodynamics and shape associate with rupture risk in intracranial aneurysms.

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Georgios A. Zenonos, Samir Sur, Maximiliano Nuñez, David T. Fernandes-Cabral and Jacques J. Morcos

In this 3D video we review the case of a lower pontine cavernous malformation in a 31-year-old man who presented with hemiparesis and an abducens palsy. The cavernous malformation was completely resected through a far lateral approach and a peritrigeminal brainstem entry zone, with a significant improvement in the patient’s hemiparesis. The relevant anatomy is reviewed in detail through multiple anatomical brainstem dissection specimens, as well as high-definition fiber tractography images. The rationale for the approach is analyzed relative to other possible options, and a number of technical pearls are provided.

The video can be found here: https://youtu.be/fH2Q7RjlBKQ.