The Sylvian fissure, cistern and arachnoid membrane

The microanatomy of the Sylvian fissure

PURPOSE

Microsurgical anatomy of the Sylvian fissure is still a popular research topic for neurosurgeons. It is important for surgeons who perform skull base and Sylvian fissure surgical procedures to master the anatomy of the region. In our study, we aimed to review the current literature on the subject.

METHODS

We reviewed the literature concerning the Sylvian fissure. In addition, we made a microdissection of four human cadaveric brains in order to take images of relevant anatomic structures.

RESULTS

The Sylvian fissure includes both superficial and deep compartments. From the beginning of the surface structures and variable thickened subarachnoid membrane to the vascular structures located at the operculo-insular compartment, the surgical technique requires meticulous dissection in all stages of the surgery.

CONCLUSIONS

From the view of neurosurgery, novel anatomical knowledge should enhance the success of the surgery. From the view of neuroscience, the Sylvian fissure and the Sylvian cistern have unique anatomical, vascular, and genotypical properties to the other areas of the cerebrum, making them complex and special.

Delineation of Subarachnoid Cisterns Using CT Cisternography, CT Brain Positive and Negative Contrast, and a Three Dimensional MRI Sequence: A Pictorial Review

The basic anatomy and morphology of subarachnoid cisterns of the brain are interesting and challenging topics with high clinical significance. These enlarged CSF-filled expansions are important as they transmit various neurovascular structures. The cisterns can be classified based on their location as supratentorial, at the level of the tentorium, and infratentorial. They are also classified as paired and unpaired cisterns. The anatomical and radiological information about the cisterns is clinically and surgically relevant in diagnosing and managing many neurological disorders. It is also essential in medical teaching. This pictorial essay reviews the radiological images where the subarachnoid cisterns are delineated in four unique circumstances.

Introducing a Realistic, Low-Cost Simulation Model for Clipping of Brain Aneurysms

BACKGROUND

The current trend toward endovascular treatment of brain aneurysms may have a negative impact on young neurosurgeons who are less exposed to these lesions, thus affecting the acquisition of surgical skills in the field. Different training models have emerged to help cope with this issue, but these have specific pitfalls. Training models based on live animals or cadaveric specimens face increasing restrictions as regulations become a barrier in accessibility for everyday skills development. We introduce a novel, realistic, and inexpensive simulation model using a fresh bovine brain, and we assess its face and content validity as a training tool.

METHODS

A fresh bovine brain is used to simulate microsurgical fissure dissection. Arterial and aneurysmal components are created with arteries and veins harvested from chicken thigh. A 12-item questionnaire using the Likert numeric scale (grades 1 - 5) was used to assess the validity of model in 10 surgeons.

RESULTS

Ten neurosurgeons performed the simulated clipping of the aneurysm and completed a questionnaire. All surgeons surveyed responded "agree" or "strongly agree" that the simulator, and the skills trained with it, are comparable to clipping brain aneurysms. All respondents believed that this simulator could improve patient safety.

CONCLUSIONS

We present a novel, realistic, and inexpensive simulation model for the clipping of brain aneurysms. This model was partially validated by the opinion of field experts. We believe this model has the potential to become a useful training tool for young neurosurgeons who have little exposure to real aneurysm cases.

Better Screening Value of Sylvian Fissure Ratio on Cognitive Decline Among Female Compared to Male: An Observational Study in Elderly Patients With Cerebral Small Vessel Disease in Soochow

Background: Cognitive decline (CD) occurs frequently in elderly patients with cerebral small vessel disease (CSVD). In China, elderly patients are more likely to enter healthcare in community hospitals where no magnetic resonance imaging (MRI) is available. This study aimed to explore the screening value of Sylvian fissure ratio (SFR) on CD and compare its gender difference from community-transferred patients.

Methods: We performed a single-center, observational study (collected between April 1, 2016, and March 1, 2019) to evaluate the association between Montreal Cognitive Assessment (MoCA) and SFR in 203 eligible community-transferred patients. Baseline characteristics of patients were collected during hospitalization. Multiple linear regression analyses were used to estimate the effect of variables on MoCA, and interactions between select variables were analyzed in different models. Receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminative effect of SFR to severe CD.

Results: We identified that a meaningful SFR cutoff of 0.05 had important screening value (likelihood ratio test, p = 0.067) on CD. The ratio had a lower screen value in males when compared to females (adjusted β, −5.54; 95% CI, −8.78 to −2.30 vs. adjusted β, −1.01; 95% CI, −2.84 to 0.82). The gender difference was further verified by ROC curve analysis, in which this discriminative effect was more potent in females (from 0.878 to 0.948) compared to males (from 0.838 to 0.837).

Conclusion: An SFR of 0.05 may be more useful to distinguish CD in female patients with CSVD than male patients in whom the syndrome is suspected clinically.

Contemporary Management of Increased Intraoperative Intracranial Pressure: Evidence-Based Anesthetic and Surgical Review

Increased intracranial pressure (ICP) is frequently encountered in the neurosurgical setting. A multitude of tactics exists to reduce ICP, ranging from patient position and medications to cerebrospinal fluid diversion and surgical decompression. A vast amount of literature has been published regarding ICP management in the critical care setting, but studies specifically tailored toward the management of intraoperative acute increases in ICP or brain bulk are lacking. Compartmentalizing the intracranial space into blood, brain tissue, and cerebrospinal fluid and understanding the numerous techniques available to affect these individual compartments can guide the surgical team to quickly identify increased brain bulk and respond appropriately. Rapidly instituting measures for brain relaxation in the operating room is essential in optimizing patient outcomes. Knowledge of the efficacy, rapidity, feasibility, and risks of the various available interventions can aid the team to properly tailor their approach to each individual patient. In this article, we present the first evidence-based review of intraoperative management of ICP and brain bulk.

Morphology of the lateral fossa of the brain (sylvian valley): anatomo-radiological aspects and surgical application

INTRODUCTION

The knowledge acquired on the lateral fossa of the brain (LFB) is heterogeneous and incomplete. Our goal was to provide a morphological description of the LFB and analyze the impact of these descriptions on the surgical approach of the region.

METHODS

The morphology of LFB was studied on 40 cerebral hemispheres of 20 right-handed subjects aged 18-55 years with an MRI of 1.5 T. The anatomo-radiological identification of the two section levels preceded the description of the shapes of the LFB. From these landmarks, the forms presented by the LFB were identified and described on each of the transverse, sagittal and frontal planes. The comparison of the proportion of shapes made it possible to identify the typical shapes at each section level and on each section plane.

RESULTS

The average age of the subjects was 33 years with extremes of 19 and 54 years including 7 women and 13 right-handed men. According to the plane and the level of section, 6 typical morphologies of the LFB have been described, 2 of which were identical. The forms did not vary according to the cerebral hemisphere or the sex of the subject. The set of typical morphologies made it possible to determine a reference subject called NSK which presented the greatest number of typical morphological characteristics.

CONCLUSION

Knowledge of LFB anatomical imaging is of paramount importance in the pre-surgical evaluation of pathologies in this region. The reference subject will be used for our future biometric and three-dimensional manual reconstruction work in this region.