Sylvian fissure splitting revisited: Applied arachnoidal anatomy and proposition of a live practice model

Development and Assessment of a High-Fidelity Simulator for the Microsurgical Dissection of the Sylvian Fissure

BACKGROUND

The dissection of the Sylvian fissure (SF) is a crucial technique requiring considerable expertise and skills traditionally acquired through years of experience. The continuous decline in surgical case-load necessitates the development of efficient alternative training opportunities. However, building a realistic and effective training simulator for the microsurgical dissection of the SF as an integral part of the neurosurgical curriculum remains a challenging endeavor. This work aims to develop and evaluate a high-fidelity phantom simulator for effective and transferable training of the SF dissection with a focus on middle cerebral artery aneurysm clipping.

METHODS

A phantom simulator replicating the anatomy and tactile properties of the human skull, brain, and meninges was developed that incorporates additive manufacturing, neurosurgical expertise, and tissue engineering. Neurosurgical residents and experienced vascular neurosurgeons (n = 16) tested and rated the simulator's face and content validities and answered questions on the model's educational usefulness.

RESULTS

The resulting SF model was found to be anatomically and haptically faithful, reusable, and modifiable. The simulator overwhelmingly received positive ratings in face and content validity, with mean scores of 4.8 and 4.7 of 5, respectively. Neurosurgeons deemed the simulator as highly accurate with respect to anatomical and tactile accuracy. Neurosurgical residents and neurosurgeons rated the simulator as superior in comparison with traditional teaching and training methods.

CONCLUSIONS

The presented methodology demonstrates that the development and assessment of a high-fidelity hands-on simulator for the focused training of one of the most delicate neurosurgical procedures is achievable in a timely manner and without extensive investments.

Training in Sylvian Arachnoid Dissection: The Art of Using Kamiyama Scissors and a Simple Novel Model for Practice Sylvian Arachnoid Dissection Using Cotton Fiber with Brain Model

Background  Transsylvian approach is one of the main approaches for a variety of vascular, tumor, and skull-base lesions. Sylvian fissure harbors a lot of critical structures including the middle cerebral artery and many venous structures. If not done properly, the transsylvian approach could cause several complications. Up to now, there is no simple training model for practicing Sylvian fissure dissection. In this article, we describe the technique of using microscissors for the sharp dissection of arachnoid trabeculae. We also propose a new model for practicing Sylvian arachnoid dissection using a three-dimensional (3D) brain model with cotton fiber. Materials and Method  We inserted cotton fiber into the Sylvian fissure of the brain model (aneurysm box from UpsurgeOn) and covered the Sylvian fissure with a cotton sheet, then sprayed the water over it. We dissected this model under a microscope by using Kamiyama scissors in the right hand and suction in the left hand. Result  Under the microscope, our model appears comparable with the real Sylvian fissure. We can use this model for practicing arachnoid dissection with Kamiyama scissors. Conclusion  The arachnoid dissection model by using a 3D brain model with cotton fiber is a simplified and novel approach for practicing the Sylvian fissure dissection.

Current Role of Surgery in the Treatment of Neurocysticercosis

Neurocysticercosis (NCC) is a common parasitic disease of the central nervous system (CNS) in low- and middle-income countries. The infection is pleomorphic, caused by the larval form of the cestode, Taenia solium, and part of the heterogeneity of its clinical presentations is associated with the localization of the parasite within the CNS. Changes in the current epidemiological trends of NCC indicate that extra-parenchymal NCC is proportionally becoming more frequent. Extraparenchymal NCC is commonly accompanied by raised intracranial hypertension due to hydrocephalus, which is an emergency requiring cyst extirpation by surgical intervention to relieve the symptoms. Although less frequent, parenchymal cysts may also reach giant sizes requiring urgent surgical treatment. Finally, there is an advancement in the comprehension of the association between NCC and epilepsy-and patients with drug-resistant seizures are candidates for surgical treatment. In this narrative review, we summarize the present state of knowledge to update the current trends in the role of surgery in the treatment of NCC.

The Spatial Patterns and Determinants of Cerebrospinal Fluid Circulation in the Human Brain

The circulation of cerebrospinal fluid (CSF) is essential for maintaining brain homeostasis and clearance, and impairments in its flow can lead to various brain disorders. Recent studies have shown that CSF circulation can be interrogated using low b-value diffusion magnetic resonance imaging (low-b dMRI). Nevertheless, the spatial organization of intracranial CSF flow dynamics remains largely elusive. Here, we developed a whole-brain voxel-based analysis framework, termed CSF pseudo-diffusion spatial statistics (C Ψ SS ), to examine CSF mean pseudo-diffusivity (M Ψ ), a measure of CSF flow magnitude derived from low-b dMRI. We showed that intracranial CSF M Ψ demonstrates characteristic covariance patterns by employing seed-based correlation analysis. Importantly, we applied non-negative matrix factorization analysis to further elucidate the covariance patterns of CSF M Ψ in a hypothesis-free, data-driven way. We identified distinct CSF spaces that consistently displayed unique pseudo-diffusion characteristics across multiple imaging datasets. Our study revealed that age, sex, brain atrophy, ventricular anatomy, and cerebral perfusion differentially influence M Ψ across these CSF spaces. Notably, individuals with anomalous CSF flow patterns displayed incidental findings on multimodal neuroradiological examinations. Our work sets forth a new paradigm to study CSF flow, with potential applications in clinical settings.

The Microcisternal Drainage Technique

BACKGROUND

Microsurgical dissection of arachnoid cisterns requires a combination of anatomic knowledge and microsurgical skill. The latter relies on experience and microsurgical dexterity, which depend on visual identification of cisternal microvasculature. We describe a novel standardized operative sequence to allow for bloodless arachnoid dissection when cisternal anatomy is challenging.

METHODS

We used the reported technique in 1928 cases over the past 5 years (2018-2022). The outer arachnoid was incised to enter the cisternal space. A cotton pledget was placed in contact with an inner membrane and gently pushed laterally and superficially with the suction cannula at medium suction power. When the arachnoid membranes dried, arachnoid trabeculae were cut and microvasculature were released at the convexity of their loops and gently transposed off the dissection trajectory. The same principle was used to release parent and perforating arteries from the aneurysm dome.

RESULTS

The microcisternal drainage technique enabled safe and efficient access through adhered arachnoid in all cases. A complex anterior communicating artery aneurysm in a 52-year-old lady demonstrated the use of the microcisternal drainage technique during access through the pericallosal cistern. This technique was used in all cases where cisternal dissection was needed.

CONCLUSIONS

The microcisternal drainage technique uses deliberate and strategic suction, dynamic retraction, and nuanced scissor cuts to enable precise and bloodless microdissection of adherent arachnoid cisterns. This technique combines common neurosurgical maneuvers in a novel standardized sequence to improve efficiency and safety during arachnoid dissection.

A Novel Surgical Classification of the Sylvian Fissure and Its Implications on the Clinical and Radiological Outcomes of Patients Undergoing Clipping for Unruptured Middle Cerebral Artery Aneurysms

BACKGROUND

The main access route for middle cerebral artery (MCA) aneurysms is the transsylvian approach. Although Sylvian fissure (SF) variations have been assessed, none have examined how this affects MCA aneurysm surgery. The objective of this study is to investigate how SF variants affect clinical and radiological outcomes for surgically-treated unruptured MCA aneurysms.

METHODS

This retrospective study examined consecutive unruptured MCA aneurysms in 101 patients undergoing SF dissection and aneurysm clipping. SF anatomical variants were categorized using a novel functional anatomical classification: Type I: Wide straight, Type II: Wide with frontal and/or temporal opercula herniation, Type III: Narrow straight, and Type IV: Narrow with frontal and/or temporal opercula herniation. The relationships between SF variants and postoperative edema, ischemia, hemorrhage, vasospasm, and Glasgow Outcome Scale (GOS) were analyzed.

RESULTS

Study included 101 patients (53.5% women), 60.9 ± 9.4 (range 24-78) years. SF types were 29.7% Type I, 19.8% Type II, 35.6% Type III, and 14.9% Type IV. The SF type with the highest proportion of females was Type IV (n = 11, 73.3%), while it was Type III for males (n = 23, 63.9%) (P = 0.03). There were significant differences between SF types, ischemia, and edema (P < 0.001, P = 0.008, respectively). Although narrow SF types had poorer GOS scores (P = 0.055), there were no significant differences between SF types and GOS, postoperative hemorrhage, vasospasm, or hospital stay.

CONCLUSIONS

Sylvian fissure variants may impact intraoperative complications during aneurysm surgery. Thus, presurgical determination of SF variants can predict surgical difficulties, thereby potentially reducing morbidity for patients with MCA aneurysms and other pathologies requiring SF dissection.

Three types of end-to-side microvascular anastomosis training models using rat common iliac arteries

Background

: Instead of only practicing these perfectly matched end-to-side anastomoses in microsurgical laboratories, we must learn how to perform these so-called “imperfect” end-to-side anastomoses in the laboratory.

Methods

Three types of end-to-side microvascular anastomoses using the rat common iliac artery (CIA), one with the proximal end of the CIA to the contralateral side of the CIA, another with the distal end of the CIA to the contralateral side of the CIA, and the third with the distal end of the CIA to the ipsilateral side of the common iliac vein (CIV), were presented to simulate different end-to-side anastomosis situations in a microsurgical laboratory. Diameters of CIA and CIV, distances between temporary clips, the length of arteriotomy or venotomy, and the distribution of stitches were recorded. The patency rates were evaluated immediately after the anastomosis was completed and 30 min later. After animal euthanasia, the donor vessel was cut close to the anastomotic site, and the orifice size and intimal attachment were evaluated by inspecting them through inside the vessel.

Results

The diameters of the CIA and CIV were 0.8–1.2 mm and 1.2–1.5 mm, respectively. The end-to-side microvascular anastomosis arteriotomy or venotomy is approximately 2.00–2.50 mm, the distance between the aneurysm clips on the recipient CIA or CIV is approximately 4.00–7.00 mm, and the distance between the corner of the arteriotomy or venotomy and the temporary aneurysm clip was 1.00–3.00 mm. Three types of end-to-side anastomoses using the CIA were successfully performed, and 100% patency rates were achieved immediately and 30 min postoperatively. Good distribution of stitches, wide orifice, and intimal attachment were recorded in the study in all groups.

Conclusions

Three types of end-to-side anastomoses using rat CIAs could be efficiently used to mimic three different anastomotic situations.

Best Practices Using Ex Vivo Animal Brain Models in Neurosurgical Education to Assess Surgical Expertise

BACKGROUND

Ex vivo animal brain simulation models are being increasingly used for neurosurgical training because these models can replicate human brain conditions. The goal of the present report is to provide the neurosurgical community interested in using ex vivo animal brain simulation models with guidelines for comprehensively and rigorously conducting, documenting, and assessing this type of research.

METHODS

In consultation with an interdisciplinary group of physicians and researchers involved in ex vivo models and a review of the literature on the best practices guidelines for simulation research, we developed the "ex vivo brain model to assess surgical expertise" (EVBMASE) checklist. The EVBMASE checklist provides a comprehensive quantitative framework for analyzing and reporting studies involving these models. We applied The EVBMASE checklist to the studies reported of ex vivo animal brain models to document how current ex vivo brain simulation models are used to train surgical expertise.

RESULTS

The EVBMASE checklist includes defined subsections and a total score of 20, which can help investigators improve studies and provide readers with techniques to better assess the quality and any deficiencies of the research. We classified 18 published ex vivo brain models into modified (group 1) and nonmodified (group 2) models. The mean total EVBMASE score was 11 (55%) for group 1 and 4.8 (24.2%) for group 2, a statistically significant difference (P = 0.006) mainly attributed to differences in the simulation study design section (P = 0.003).

CONCLUSIONS

The present findings should help contribute to more rigorous application, documentation, and assessment of ex vivo brain simulation research.

Changing Hands: A Rising Role of the Tumor Surgeon in Teaching Sylvian Fissure Dissection

OBJECTIVE

The landscape of microneurosurgery has changed considerably over the past 2 decades, with a decline in indications for open surgery on cerebrovascular pathology and ever-increasing indications for open resection of brain tumors. This study investigated how these trends in case volume affected residents' training experiences in microsurgery and, specifically, Sylvian fissure dissection.

METHODS

Resident case logs were reviewed, identifying open cerebrovascular operations and craniotomies for tumor. Operations involving Sylvian fissure dissection were identified through operative reports. Changes in case number by resident were plotted over time, and linear regression was applied.

RESULTS

Among 23 chief residents, 3045 operations were identified, 1071 of which were for cerebrovascular pathology and 1974 for tumor. Open cerebrovascular experience decreased (P < 0.0001) while tumor volume remained unchanged (P = 0.221). The number of Sylvian fissure dissections per resident did not change over time overall (P = 0.583) or within cerebrovascular operations (P = 0.071). The number of Sylvian fissure dissections in tumor operations increased (P = 0.004). This effect was predominated by an increase in intraaxial tumors approached via Sylvian fissure dissection (P = 0.003). The proportion of Sylvian fissure dissections in tumor surgery increased from 15% in 2009 to 34% by 2019 (P = 0.003).

CONCLUSIONS

Residents are seeing an increasing proportion of their Sylvian fissure dissection experience during tumor operations. The distribution of this experience will continue to evolve as surgical indications change but suggests a growing role for tumor surgeons in resident training in microsurgery.