A review of brain retraction and recommendations for minimizing intraoperative brain injury

A comparison of brain retraction mechanisms using finite element analysis and the effects of regionally heterogeneous material properties

Finite element (FE) simulations of the brain undergoing neurosurgical procedures present us with the great opportunity to better investigate, understand, and optimize surgical techniques and equipment. FE models provide access to data such as the stress levels within the brain that would otherwise be inaccessible with the current medical technology. Brain retraction is often a dangerous but necessary part of neurosurgery, and current research focuses on minimizing trauma during the procedure. In this work, we present a simulation-based comparison of different types of retraction mechanisms. We focus on traditional spatulas and tubular retractors. Our results show that tubular retractors result in lower average predicted stresses, especially in the subcortical structures and corpus callosum. Additionally, we show that changing the location of retraction can greatly affect the predicted stress results. As the model predictions highly depend on the material model and parameters used for simulations, we also investigate the importance of using region-specific hyperelastic and viscoelastic material parameters when modelling a three-dimensional human brain during retraction. Our investigations demonstrate how FE simulations in neurosurgical techniques can provide insight to surgeons and medical device manufacturers. They emphasize how further work into this direction could greatly improve the management and prevention of injury during surgery. Additionally, we show the importance of modelling the human brain with region-dependent parameters in order to provide useful predictions for neurosurgical procedures.

Brain retraction injury: systematic literature review

Cerebral retraction is frequently required in cranial surgery to access deep areas. Brain retractors have been systematically used in the past, but they have been associated with brain injury. Nonetheless, they are still used and, even recently, new systems have been advocated. The aim of this study is to provide a systematic and critical review of brain retraction injury. A systematic literature review was performed in February 2023 according to PRISMA statement. Search terms included brain retraction and injury, with their variations and pertinent associations. Studies reporting qualitative and quantitative data on brain retraction injury were included. Out of 1689 initially retrieved articles, 90 and 26 were included in the systematic review for qualitative and quantitative data, respectively. The definition of brain retraction injury varies and its reported incidence in clinical studies is 5-10%, up to 47% if cerebral edema is considered. Some studies have hypothesized threshold values of pressures to be respected in order to prevent complications, with most data deriving from animal studies. At present, there are no instruments for brain retraction that can guarantee full safety. Some form of cerebral retraction might always be necessary for specific scenarios. Further studies are needed to collect quantitative and, ideally, clinical and comparative data on pressure thresholds to develop retraction systems that can reduce injury to a minimum.

Endoscopy-assisted resection of a sphenoid-wing meningioma using a 3D-printed patient-specific pointer in a dog: A case report

A 9-year-old female mixed-breed dog presented for treatment of a presumed sphenoid-wing meningioma. Clinical signs included tonic-clonic seizures lasting <1 min, which had started 3 months previously. The physical examination results were unremarkable. An eccentrically located neoplastic cystic structure in the right sphenoid bone region suggestive of a meningioma and peritumoural brain oedema was observed in pre-operative magnetic resonance imaging (MRI). Prior to surgery, a three-dimensional (3D) patient-specific pointer (PSP) was designed using computed tomography (CT) images and computer-aided 3D design software. After a targeted approach and exposure of the lateral part of the right temporal lobe by a craniectomy guided by the 3D-PSP, complete macroscopic piecemeal resection of the meningioma could be performed using endoscopy-assisted brain surgery. Post-operative MRI confirmed complete excision of the tumor. Anticonvulsive therapy was discontinued after 90 days, and the dosage of anticonvulsants was tapered 2 weeks after surgery. At a follow-up examination 225 days post-operatively, recurrence of seizures was not observed, and the absence of tumor recurrence was confirmed by a repeat MRI examination. To the best of our knowledge, this is the first report in veterinary medicine describing a successful resection of a sphenoid-wing meningioma using a 3D-PSP. 3D-PSP-assisted craniectomy may be a surgical option for some canine skull-based tumors, such as sphenoid wing meningiomas.

Wide Dissection Trans-Sulcal Approach for Resection of Deep Intra-Axial Lesions in Eloquent Brain Areas

Introduction: Resection of intra-axial tumors (IaT) in eloquent brain regions risks major postoperative neurological deficits. Awake craniotomy is often used to navigate these areas; however, some patients are ineligible for awake procedures. The trans-sulcal approach (TScal) was introduced to reduce parenchymal trauma during tumor resection. We report our experiences utilizing TScal for resection of deep IaT located in eloquent areas. Materials and Methods: This is a single-center retrospective analysis of patients who underwent IaT resection in eloquent areas via TScal from January 2013 to April 2021. Seventeen cases were reviewed, and relevant data was collected. Fluorescence-guided surgery with 5-aminolevulinic acid (ALA) and intraoperative ultrasound was performed in some cases. Results: Seventeen patients (10 males, 7 females) averaging 61.2 years-old (range, 21-76) were included in this study. Average length of stay was 4.8 days, and only 2 patients (11.8%) required hospital readmission within 30 days. Gross total resection (GTR) was achieved in 15 patients (88.2%), while subtotal resection occurred in 2 patients (11.8%). Eleven patients (64.7%) reported full resolution of symptoms, 4 patients (23.5%) reported deficit improvement, and 2 patients (11.8%) experienced no change from their preoperative deficits. No patient developed new permanent deficits postoperatively. Discussion: GTR, preoperative deficit reduction, and complications were comparable to awake craniotomy and other TScal studies. Ancillary intraoperative techniques, such as brain mapping, 5-ALA and intraoperative ultrasound, are afforded by TScal to improve resection rates and overall outcomes. Conclusions: TScal can be an option for patients with deep lesions in eloquent areas who are not candidates for awake surgeries.

Morphological Analysis of the Sylvian Fissure Stem to Guide a Safe Trans-sylvian Fissure Approach

The sylvian fissure stem and its deep cisternal part (SDCP) consist mainly of the orbital gyrus (OG) and anterior medial portion of the temporal lobe. SDCP's adhesion has been found to make a trans-sylvian approach difficult due to the various patterns of adhesion. Thus, in this study, we aim to clarify the morphological features of the SDCP, and to guide a safe trans-sylvian approach. We retrospectively classified the morphology of the SDCP in 81 patients into 3 types (tight, moderate, loose type) according to the degree of adhesion of the arachnoid membrane and analyzed the morphological features of the OG and the temporal lobe using intraoperative video images. In addition, we have retrospectively measured each width of the SDCP's subarachnoid space at the three points (Point A, lateral superior portion; Point B, downward portion; Point C, medial inferior portion of SDCP) and analyzed their relationship to the degree of adhesion using the preoperative coronal three-dimensional computed tomography angiography (3D-CTA) images of 44 patients. As per the results, SDCP's adhesions were determined to be significantly tighter in cases with large OG and young cases. The temporal lobe had four surfaces (posterior, middle, anterior, and medial) that adhered to the OG in various patterns. The tighter the adhesion between the OG and each of the three distal surfaces of the temporal lobe, the narrower the width of the subarachnoid space at each point (A, B, C). Understanding of the morphological features of the SDCP, and estimating its adhesion preoperatively are useful in developing a surgical strategy and obtaining correct intraoperative orientation in the trans-sylvian approach.

Multiple Meningioma Resection by Bilateral Extended Rostrotentorial Craniotomy with a 3D-Print Guide in a Cat

Simple Summary

Meningioma is the most common intracranial neoplasia in cats. Treatments for meningiomas—including complete surgical resection, debulking, irradiation, or palliative therapy—have been reported in veterinary medicine. However, multiple meningiomas (two or more meningiomas in the same patient, separated by anatomical location) have been reported to affect the complication rate and prognosis. Moreover, the characteristics of neurosurgery—such as accurate localization and awareness of the anatomical structures of the lesions—make the surgery especially difficult for inexperienced surgeons. Surgical navigation systems have been developed, but recently, patient-specific three-dimensional(3D)-printed models and guides have also been used in orthopedics and neurosurgeries for treating many disorders with good results. A 13-year-old castrated male domestic shorthair cat was referred with multiple meningiomas located within the right frontal and occipital lobes. The cat suffered from generalized tonic–clonic seizures and mild proprioceptive ataxia. After removing both of the tumors, the cat showed a favorable clinical outcome and no neurological abnormalities throughout long-term follow-up. With a patient-specific 3D guide technology, a craniotomy for multiple meningiomas can be performed safely and accurately.

Abstract

A 13-year-old castrated male domestic shorthair cat was referred for the surgical removal of multiple meningiomas. The cat experienced generalized tonic–clonic seizures, altered mentation, mild proprioceptive ataxia, and circling. Magnetic resonance imaging (MRI) revealed two round, solitary, well-delineated, space-occupying lesions suggestive of multiple meningiomas in the right frontal and occipital lobes. Before surgery, patient-specific three-dimensional (3D) printed models and guides were produced using a 3D program based on MRI and computed tomography (CT), and a rehearsal surgery was performed. With a 3D guide to find the location of the craniotomy lines, bilateral extended rostrotentorial craniotomy allowed en bloc resection of multiple meningiomas. The bone fragment was replaced and secured to the skull with a craniofacial plate and screws with an artificial dura. All of the surgical steps were performed without complications. The preoperative presenting signs were resolved by the time of follow-up examinations 2 weeks after surgery. Twelve months after the removal of the multiple meningiomas, the cat survived without further neurological progression. For the resection of multiple meningiomas, surgery can result in large bone defects and risk of massive hemorrhage. For this challenging surgery, patient-specific 3D models and guides can be effective for accurate and safe craniotomies.

Brain retraction injury after elective aneurysm clipping: a retrospective single-center cohort study

Background

BRI is estimated to occur in 10% of skull-base surgery and 5% of aneurysm surgery. These estimates are based on a few studies with unclear methodology. The purpose of this study is to assess the rate of BRI occurrence, its risk factors, and the association between BRI and postoperative focal neurological deficit in patients that underwent elective aneurysm surgery in a single institution.

Methods

All patients that underwent elective aneurysm surgery in a single tertiary center in the Netherlands were included. BRI was defined as cortical hypodensities in the surgical trajectory not matching areas of large arterial infarction. Risk ratios were calculated between BRI and (a) the use of temporary parent artery occlusion during clipping, (b) anterior communicating artery (ACom), and (c) middle cerebral artery (MCA) location of the aneurysm, (d) presence of mentioned CVA risk factors, (e) the clipping of > 1 aneurysm during the same procedure, and (f) new focal neurological deficit. Statistical analysis further included t-tests and binary logistical regression analysis on the correlation between age and BRI.

Results

BRI was identified postoperatively in 42 of the 94 patients included in this study. A new focal neurological deficit was found in 7 patients in the BRI group. A total of 5 patients had persisting symptoms at 3-month follow-up, of which 2 were caused by BRI. Increasing age is a risk factor for developing BRI.

Conclusions

The high rate of BRI and significant risk of new postoperative focal neurological deficit in our patients should be considered when counseling patients for elective aneurysm surgery.

Soft Robotic Deployable Origami Actuators for Neurosurgical Brain Retraction

Metallic tools such as graspers, forceps, spatulas, and clamps have been used in proximity to delicate neurological tissue and the risk of damage to this tissue is a primary concern for neurosurgeons. Novel soft robotic technologies have the opportunity to shift the design paradigm for these tools towards safer and more compliant, minimally invasive methods. Here, we present a pneumatically actuated, origami-inspired deployable brain retractor aimed at atraumatic surgical workspace generation inside the cranial cavity. We discuss clinical requirements, design, fabrication, analytical modeling, experimental characterization, and in-vitro validation of the proposed device on a brain model.

Surgical advances in the management of brain metastases

As the epidemiological and clinical burden of brain metastases continues to grow, advances in neurosurgical care are imperative. From standard magnetic resonance imaging (MRI) sequences to functional neuroimaging, preoperative workups for metastatic disease allow high-resolution detection of lesions and at-risk structures, facilitating safe and effective surgical planning. Minimally invasive neurosurgical approaches, including keyhole craniotomies and tubular retractors, optimize the preservation of normal parenchyma without compromising extent of resection. Supramarginal surgery has pushed the boundaries of achieving complete removal of metastases without recurrence, especially in eloquent regions when paired with intraoperative neuromonitoring. Brachytherapy has highlighted the potential of locally delivering therapeutic agents to the resection cavity with high rates of local control. Neuronavigation has become a cornerstone of operative workflow, while intraoperative ultrasound (iUS) and intraoperative brain mapping generate real-time renderings of the brain unaffected by brain shift. Endoscopes, exoscopes, and fluorescent-guided surgery enable increasingly high-definition visualizations of metastatic lesions that were previously difficult to achieve. Pushed forward by these multidisciplinary innovations, neurosurgery has never been a safer, more effective treatment for patients with brain metastases.

Dissection of the Sylvian Fissure in the Trans-sylvian Approach Based on the Morphological Classification of the Superficial Middle Cerebral Vein

The superficial middle cerebral vein (SMCV) is one of the main factors that can impede a wide opening of the sylvian fissure. To reveal the most efficient SMCV dissection for a wide operative field while preserving the veins in the trans-sylvian approach, we retrospectively investigated the SMCVs through intraoperative video images. We characterized the SMCV as composed of the frontosylvian trunk (FST; receiving frontosylvian veins [FSVs] or parietosylvian veins [PSVs]), the temporosylvian trunk (TST; receiving temporosylvian veins [TSVs]), and the superficial middle cerebral common trunk (SMCCT; receiving both FSV/PSV and TSV), and classified the SMCVs of the 116 patients into 5 types based on the morphological classification of the SMCV. Type A SMCV (60.4%) with the SMCCT anastomosed to the frontal side had few bridging veins (BVs) between the SMCCT and the temporal side during dissection. Type B (7.8%) had the SMCCT with no anastomoses to the frontal side. In Type C (17.2%) consisting of the FST and TST and Type D (12.9%) with a merging of the vein of Trolard and Labbé posteriorly and the SMCVs dividing into the FST and the TST again proximally, there were few BVs between the FST and the TST during dissection. Finally, in Type E (1.7%) showing an undeveloped SMCV, there were no BVs between the frontal and the temporal lobes. Postoperative venous infarction occurred in 2.6%. Morphological classification of the SMCV can inform appropriate dissection line to create a wide operative field while preserving the veins in the trans-sylvian approach.

Clinical applications of the endoscopic transorbital approach for various lesions

BACKGROUND

The endoscopic transorbital approach (ETOA) was recently added to the neurosurgical armamentarium. Although this approach could result in less injury to normal brain tissue, shorter operation times, and smaller scars, its clinical applications have not been fully investigated. We, therefore, sought to share our unique experiences of exploring the application of this approach in various diseases.

METHODS

From June 2017 to March 2019, we conducted ETOAs via the superior eyelid crease in 22 patients for the treatment of lesions confined to the middle fossa with and without slight extension to the posterior fossa. These lesions included 5 gliomas, 11 meningiomas, 3 schwannomas, 1 lymphoma, 1 cavernous hemangioma in the orbital wall, and 1 hemangiopericytoma mimicking schwannoma. Perioperative radiologic findings and clinical outcomes were recorded.

RESULTS

Gross total resection was accomplished in three (60%) patients with gliomas, nine (81.8%) with meningiomas, two (66.7%) with schwannomas, and one (33.3%) with another lesion. The mean bleeding count was 1051.4 ± 961.1 cc, and major complications were observed in only two (9.1%) cases (one major cerebral artery infarction and one reoperation due to a large amount of bleeding). A cerebrospinal fluid leak was reported in two (9.1%) patients, and transient eye movement palsy was noted in four (18.2%) patients without permanent disability.

CONCLUSIONS

The endoscopic transorbital approach could be considered to be feasible for various lesions with different characteristics. After carefully considering the lesion anatomy, consistency, and vascular relationships, using this approach, we could achieve a satisfactory extent of resection without severe complications.

Brain Invasion in Meningioma-A Prognostic Potential Worth Exploring

Most meningiomas are slow growing tumors arising from the arachnoid cap cells and can be cured by surgical resection or radiation therapy in selected cases. However, recurrent and aggressive cases are also quite common and challenging to treat due to no established treatment alternatives. Assessment of the risk of recurrence is therefore of utmost importance and several prognostic clinical and molecular markers have been established. Additionally, the identification of invasive growth of meningioma cells into CNS tissue was demonstrated to lead to a higher risk of recurrence and was therefore integrated into the WHO classification of CNS tumors. However, the evidence for its prognostic impact has been questioned in subsequent studies and its exclusion from the next WHO classification proposed. We were recently able to show the prognostic impact of CNS invasion in a large comprehensive retrospective meningioma cohort including other established prognostic factors. In this review we discuss the growing experiences that have been gained on this matter, with a focus on the currently nonuniform histopathological assessment, imaging characteristics and intraoperative sampling as well as the overall outlook on the future role of this potential prognostic factor.

Impact of the weekend effect on outcome after microsurgical clipping of ruptured intracranial aneurysms

BACKGROUND

The "weekend effect" describes the assumption that weekend and/or on-call duty admission of emergency patients is associated with increased morbidity and mortality rates. For aneurysmal subarachnoid hemorrhage, we investigated, whether presentation out of regular working hours and microsurgical clipping at nighttime correlates with worse patient outcome.

METHODS

This is a retrospective review of consecutive patients that underwent microsurgical clipping of an acutely ruptured aneurysm at our institution between 2010 and 2019. Patients admitted during (1) regular working hours (Monday-Friday, 08:00-17:59) and (2) on-call duty and microsurgical clipping performed during (a) daytime (Monday-Sunday, 08:00-17:59) and (b) nighttime were compared regarding the following outcome parameters: operation time, treatment-related complications, vasospasm, functional outcome, and angiographic results.

RESULTS

Among 157 enrolled patients, 104 patients (66.2%) were admitted during on-call duty and 48 operations (30.6%) were performed at nighttime. Admission out of regular hours did not affect cerebral infarction (p = 0.545), mortality (p = 0.343), functional outcome (p = 0.178), and aneurysm occlusion (p = 0.689). Microsurgical clipping at nighttime carried higher odds of unfavorable outcome at discharge (OR: 2.3, 95%CI: 1.0-5.1, p = 0.039); however, there were no significant differences regarding the remaining outcome parameters. After multivariable adjustment, clipping at nighttime did not remain as independent prognosticator of short-term outcome (OR: 2.1, 95%CI: 0.7-6.2, p = 0.169).

CONCLUSIONS

Admission out of regular working hours and clipping at nighttime were not independently associated with poor outcome. The adherence to standardized treatment protocols might mitigate the "weekend effect."

Outcomes after mini-craniotomy middle fossa approach combined with mastoidectomy for lateral skull base defects

PURPOSE

Controversy exists regarding the ideal approach for repair of lateral skull base defects. Our goal is to report the outcomes following middle cranial fossa (MCF) mini-craniotomy combined with mastoidectomy for patients with superior semicircular canal dehiscence (SSCD), spontaneous cerebrospinal fluid (CSF) leak, and cholesteatoma.

MATERIALS AND METHODS

A retrospective database from chart review was formed consisting of 97 patients who met surgical criteria: SSCD, spontaneous CSF leak, and cholesteatoma. Mini-craniotomy MCF approach (<4 × 2 cm in size) combined with mastoidectomy was performed. All patients were admitted directly to the ICU postoperatively. Multiple factors were assessed, including need for revision surgery, duration of surgery, length of post-operative stay, and hospital readmission.

RESULTS

Average surgery time was 110 min with no intraoperative complications. The average length of hospitalization was 2 days with an average ICU stay of 1 day. There were no neurologic complications; however, there were 3 inpatient complications (3%) which included 1 patient (1%) that had wound breakdown and 2 patients (2%) that had severe post-operative vertigo. A total of 8 patients (8%) required revision surgery and these were primarily for SSCD. The 30-day readmission rate was 3%.

CONCLUSION

In the current series, all patients that underwent mini-craniotomy MCF surgery combined with mastoidectomy had minimal complications, short surgical time, limited hospital stay, low revision surgery rate and few hospital readmissions. This combined approach offers superior visualization of lateral skull base defects without the morbidity and risk typically associated with traditional, extensive MCF surgery.

Real-Time Intraoperative Pressure Monitoring to Avoid Surgically Induced Localized Brain Injury Using a Miniaturized Piezoresistive Pressure Sensor

Neurosurgical procedures often cause damage to the brain tissue at the periphery from surgical manipulations. Especially during retraction, a large amount of pressure could be applied on the brain surface, which can damage it, leading to brain herniation, which can be fatal for patients. To resolve this issue, we have developed a pressure sensor that can be used to monitor the applied pressure during surgery for intraoperative care. This device was tested on a rodent model to create a superficial surgically induced damage profile for three different applied pressures (30, 50, and 70 mmHg) and compared to a standard intracranial pressure monitoring system. Magnetic resonance imaging has been performed after surgical procedures to detect the herniation caused by applied pressure. To evaluate the damage to brain cells and tissue rupture, histological analysis was performed using hematoxylin and eosin staining. A scoring system was developed to understand the severity of the surgically induced brain injury, which will help neurosurgeons to limit the pressure to an optimum point without causing damage.

Minimally invasive resection of intracranial lesions using tubular retractors: a large, multi-surgeon, multi-institutional series

PURPOSE

Lesions located in subcortical areas are difficult to safely access. Tubular retractors have been increasingly used successfully with low complication profile to access lesions by minimizing brain retraction trauma and distributing pressure radially. Both binocular operative microscope and monocular exoscope are utilized for lesion visualization through tubular retractors. We present the largest multi-surgeon, multi-institutional series to determine the efficacy and safety profile of a transcortical-transtubular approach for intracranial lesion resections with both microscopic and exoscopic visualization.

METHODS

We reviewed a multi-surgeon, multi-institutional case series including transcortical-transtubular resection of intracranial lesions using either BrainPath (NICO, Indianapolis, Indiana) or ViewSite Brain Access System (VBAS, Vycor Medical, Boca Raton, Florida) tubular retractors (n = 113).

RESULTS

One hundred thirteen transtubular resections for intracranial lesions were performed. Patients presented with a diverse number of pathologies including 25 cavernous hemangiomas (21.2%), 15 colloid cysts (13.3%), 26 GBM (23.0%), two meningiomas (1.8%), 27 metastases (23.9%), 9 gliomas (7.9%) and 9 other lesions (7.9%). Mean lesion depth below the cortical surface was 4.4 cm, and mean lesion size was 2.7 cm. A gross total resection was achieved in 81 (71.7%) cases. Permanent complication rate was 4.4%. One patient (0.8%) experienced one early postoperative seizure (< 1 week postop). No patients experienced late seizures (> 1 week follow-up). Mean post-operative hospitalization length was 4.1 days.

CONCLUSION

Tubular retractors provide a minimally invasive operative corridor for resection of intracranial lesions. They provide an effective tool in the neurosurgical armamentarium to resect subcortical lesions with a low complication profile.

Tumor retractor: a simple and novel instrument for brain tumor surgery

Background

It is important to secure a surgical space during brain tumor surgery. One of the commonly used methods is to retract the brain. We hypothesized that the tumor can be retracted and that the normal brain tissue retraction can be minimized during surgery, and thus, the degree of collateral damage caused by brain retraction would be reduced.

Methods

The tumor retractor had a 90°, hard, and sharp tip for fixation of the tumor. The distal part of the retractor has a malleable and thin blade structure. By adjusting the angle of the distal malleable part of the tumor retractor, the operator can make the retracting angle additionally. Retractors with thin blade can be used in a conventional self-retraction system. To pull and hold the tumor constantly, the tumor retractor is held by a self-retraction system. The surgical technique using a tumor retractor is as follows: The first step is to fix the retractor to the tumor. The second step is to pull the retractor in the operator’s desired direction by applying force. After the tumor is pulled by adjusting the degree of force and angle, the surgical arm should be held in place to maintain the tumor retracted state.

Results

The tumor retractor was used to minimize the brain retraction, pulling the tumor in the opposite direction from the surrounding brain tissue. In clinical cases, we can apply the tumor retractor with good surgical outcomes.

Conclusions

A tumor retractor can be used to pull a tumor and minimize the brain retraction.

Comparison between retrosigmoid and translabyrinthine approaches for large vestibular schwannoma: focus on cerebellar injury and morbidities

This study aimed to compare the surgical outcomes and morbidities of retrosigmoid and translabyrinthine approaches for large vestibular schwannoma (VS), with a focus on cerebellar injury and morbidities. Eighty-six consecutive patients with large VS, with a maximal extrameatal diameter > 3.0 cm, were reviewed between August 2010 and September 2018. The surgical outcomes, operating time, volume change of perioperative cerebellar edema, and inpatient rehabilitation related to cerebellar morbidities were compared between the two approaches. In total, 53 and 33 patients underwent the retrosigmoid and translabyrinthine approaches, respectively. The median follow-up time was 34.5 months. Surgical outcomes, including the extent of resection, tumor recurrence, and facial nerve preservation, showed no significant differences between the two groups. Patients who underwent the retrosigmoid approach showed a marginal trend for postoperative lower cranial nerve (LCN) dysfunction (P = 0.068). Although the approaching procedure time was longer in the translabyrinthine group, the tumor resection time was significantly longer in the retrosigmoid group (P = 0.001). The median change in the volume of the perioperative cerebellar edema was significantly larger in the retrosigmoid group (P < 0.001) and significantly related to the retrosigmoid approach, solid VS, and tumor resection time. Most cerebellar and LCN deficits were transient; however, the patients in the retrosigmoid group underwent inpatient rehabilitation more than those in the translabyrinthine group (P = 0.018). Both surgical approaches show equivalent surgical outcomes. Notably, the translabyrinthine approach for large VS has advantages in that it reduces cerebellar injury and related morbidities.

Combination of the tubular retractor and brain spatulas provides an adequate operative field in surgery for deep-seated lesions: Case series and technical note

Background:

Surgeries for deep-seated lesions are challenging because making a corridor and observing the interface between lesions and normal brain tissue are difficult. The ViewSite Brain Access System, which is a clear plastic tubular retractor system, is used for resection of deep-seated lesions. However, the tapered shape of this system may result in limitation of the surgical field and cause brain injury to observe the interface between lesions and normal tissue. In this study, we evaluated the usefulness of the combination of ViewSite and brain spatulas.

Methods:

Nine patients were retrospectively identified who underwent resection of deep-seated lesions with the combination of Viewsite and brain spatulas. We assessed the extent of resection, prognosis, and quantitative brain injury from postoperative diffusion-weighed imaging (DWI).

Results:

There were four total radiographically confirmed resections. Subtotal resection in four patients and partial resection in one with central neurocytoma were achieved because these tumors were strongly adherent to the choroid plexus and ependymal veins. Only one case of metastatic tumor relapsed 6 months after surgery. The mean postoperative high signal on DWI was 3.68 ± 0.80 cm³.

Conclusions:

The combination of ViewSite and brain spatulas provides wide and adequate operative fields to observe the interface between lesions and normal tissue, and to prevent brain injury from excessive retraction pressure on the brain derived from repositioning of the ViewSite. Postoperative 3D volumetric analysis shows minimal damage to normal brain tissue. This report may provide new insight into the use of the ViewSite tubular retractor.

Retractorless surgery for third ventricle tumor resection through the transcallosal approach

OBJECTIVE

Resection of tumors of the third ventricle through the transcallosal-interforniceal approach presents a surgical challenge with potential serious postoperative neurological deficits and complications. Retraction injury of the deep brain tissue and veins is a possible reason. Here, we aimed to investigate the feasibility and value of retractorless surgery in third ventricle tumor resection.

PATIENTS AND METHODS

Since 2014, a total of 31 patients with third ventricle tumors were operated in our institution. All patients were operated using the transcallosal-interforniceal approach with a straight incision. The use of self-retaining retractor or constant retraction was not allowed. At the end of surgery, the opening of corpus callosum was sealed with fibrin glues. The degrees of tumor resection and postoperative neurological function deficits as well as complications were analyzed. The effect of retractorless surgery was evaluated according to the brain edema around the surgical approach on T2 imaging.

RESULTS

Thirty-one tumors were located in the anterior, middle, and posterior of the third ventricle. Total or gross total resection was achieved in 25 patients (80.6%). Postoperative neurological function deficits occurred in 4 patients (12.9%), and patients with mutism had a good recovery 3 weeks post-surgery. Retraction injuries around the surgical pathway were not obvious on T2 imaging. In addition, no subdural hygroma and subcutaneous fluid accumulation occurred.

CONCLUSIONS

The application of retractorless surgery in third ventricle tumors is feasible with enough exposure of tumors. This application could decrease the occurrence of postoperative neurological deficits and complications by avoiding the retraction injury on the deep brain structures.

A multiport MR-compatible neuroendoscope: spanning the gap between rigid and flexible scopes

OBJECTIVE Rigid endoscopes enable minimally invasive access to the ventricular system; however, the operative field is limited to the instrument tip, necessitating rotation of the entire instrument and causing consequent tissue compression while reaching around corners. Although flexible endoscopes offer tip steerability to address this limitation, they are more difficult to control and provide fewer and smaller working channels. A middle ground between these instruments-a rigid endoscope that possesses multiple instrument ports (for example, one at the tip and one on the side)-is proposed in this article, and a prototype device is evaluated in the context of a third ventricular colloid cyst resection combined with septostomy. METHODS A prototype neuroendoscope was designed and fabricated to include 2 optical ports, one located at the instrument tip and one located laterally. Each optical port includes its own complementary metal-oxide semiconductor (CMOS) chip camera, light-emitting diode (LED) illumination, and working channels. The tip port incorporates a clear silicone optical window that provides 2 additional features. First, for enhanced safety during tool insertion, instruments can be initially seen inside the window before they extend from the scope tip. Second, the compliant tip can be pressed against tissue to enable visualization even in a blood-filled field. These capabilities were tested in fresh porcine brains. The image quality of the multiport endoscope was evaluated using test targets positioned at clinically relevant distances from each imaging port, comparing it with those of clinical rigid and flexible neuroendoscopes. Human cadaver testing was used to demonstrate third ventricular colloid cyst phantom resection through the tip port and a septostomy performed through the lateral port. To extend its utility in the treatment of periventricular tumors using MR-guided laser therapy, the device was designed to be MR compatible. Its functionality and compatibility inside a 3-T clinical scanner were also tested in a brain from a freshly euthanized female pig. RESULTS Testing in porcine brains confirmed the multiport endoscope's ability to visualize tissue in a blood-filled field and to operate inside a 3-T MRI scanner. Cadaver testing confirmed the device's utility in operating through both of its ports and performing combined third ventricular colloid cyst resection and septostomy with an endoscope rotation of less than 5°. CONCLUSIONS The proposed design provides freedom in selecting both the number and orientation of imaging and instrument ports, which can be customized for each ventricular pathological entity. The lightweight, easily manipulated device can provide added steerability while reducing the potential for the serious brain distortion that happens with rigid endoscope navigation. This capability would be particularly valuable in treating hydrocephalus, both primary and secondary (due to tumors, cysts, and so forth). Magnetic resonance compatibility can aid in endoscope-assisted ventricular aqueductal plasty and stenting, the management of multiloculated complex hydrocephalus, and postinflammatory hydrocephalus in which scarring obscures the ventricular anatomy.

The transsylvian approach for resection of insular gliomas: technical nuances of splitting the Sylvian fissure

Insular gliomas represent a unique surgical challenge due to the complex anatomy and nearby vascular elements associated within the Sylvian fissure. For certain tumors, the transsylvian approach provides an effective technique for achieving maximal safe resection. The goal of this manuscript and video are to present and discuss the surgical nuances and appropriate application of splitting the Sylvian fissure. Our hope is that this video highlights the safety and efficacy of the transsylvian approach for appropriately selected insular gliomas.

Exposing the Fundus of the Internal Acoustic Meatus without Entering the Labyrinth Using a Retrosigmoid Approach: Is It Possible?

OBJECTIVES

To evaluate the feasibility of performing a labyrinth-sparing neuronavigation-assisted retrosigmoid approach to the fundus of the internal acoustic meatus (IAM) and to describe the anatomy of the structures embedded in the posterior meatal wall.

METHODS

Ten surgical dissections were performed bilaterally on 5 fresh cadavers. Cadavers were subjected to preoperative computed tomography scans and spatial coordinates of inner ear structures were recorded. A retrosigmoid craniectomy was performed. The IAM was drilled towards the fundus until no more than 1 mm of bone covered the labyrinthine structures. Specimens underwent a new computed tomography scan to verify the length of opened IAM and the status of the labyrinth. We then opened the labyrinthine structures and recorded their coordinates using navigation. These were compared with the radiologic coordinates to verify the neuronavigation accuracy.

RESULTS

In 9 sides, the IAM was opened to the fundus without injuring the labyrinth; in 1 side, the vestibule was opened. The mean residual bone on the fundus was 0.97 mm. The average length of the accessible IAM was 88.95%. The best accuracy of the navigation was for the identification of the common crus, with a mean value of 0.73 mm.

CONCLUSIONS

This surgical technique could facilitate the opening of the IAM with preservation of inner ear structures. We opened a mean of 88.95% of the IAM without entering the labyrinthine structures in 90% of cases. These results confirm the feasibility of the retrosigmoid approach for the exposure of the IAM fundus with preservation of labyrinthine structures.

Clip-retraction of the superficial Sylvian vein to enhance visualization in "retractorless" aneurysm surgery

BACKGROUND

According to microsurgical principles, the access to deep-seated cerebral lesions should be as atraumatic as possible. Temporary brain retraction is acceptable in certain situations and may be indispensable when the view of the lesion is obstructed.

METHOD

The utility of this method is illustrated in a case of a ruptured middle cerebral artery (MCA) aneurysm. Two temporary aneurysm clips were connected by a braided suture, thus forming a band with two points of attachment. The Sylvian fissure was opened in a standard fashion. Using one clip, the adventitia and arachnoid over the superficial Sylvian vein were grasped firmly enough to mobilize the superficial Sylvian vein. The distal clip was then attached to surrounding drapes, thus granting a direct view of the aneurysm in the depth of the fissure. Retraction with spatula was not necessary. Patency of the superficial Sylvian vein was demonstrated using idocyanine green angiography.

RESULTS

We present a simple method for minimally traumatic brain retraction using aneurysm clips attached to the adventitia of Sylvian veins and held back by sutures.

CONCLUSION

The use of clips attached to the adventitia of the superficial Sylvian may be of help in retracting the Sylvian fissure. By virtue of enlarging the field of view into the deep Sylvian fissure, it may be of help in performing retractorless aneurysm surgery.

Anatomy and physiology of cisternostomy

Cisternostomy is defined as opening the basal cisterns to atmospheric pressure. This technique helps to reduce the intracranial pressure in severe head trauma as well as other conditions when the so-called sudden "brain swelling" troubles the surgeon. We elaborated the surgical anatomy of this procedure as well as the proposed physiology of how cisternostomy works. This novel technique may change the current trends in neurosurgery.

Retractorless Surgery for Anterior Circulation Aneurysms via a Pterional Keyhole Approach

Brain retraction is required during many intracranial procedures to provide more working space. However, it is difficult to avoid brain retraction injury. Here, we report on retractorless surgery for anterior circulation aneurysms via a pterional keyhole approach. All patients undergoing a minimally invasive pterional keyhole approach within 3 days after hemorrhage by the same surgeon were included in the study. Patients were randomly assigned into group I (with the retractorless technique) and group II (with fixed retractors). Data on adequate clipping level, intraoperative ischemia induced by retraction, operation time, brain retraction injury, intraoperative blood loss, intraoperative aneurysm rupture, and modified Rankin Scale were collected for the 2 groups. A consecutive series of 47 patients (21 patients in group I, 26 patients in group II) successfully underwent a minimally invasive pterional keyhole approach. Statistical analysis revealed no significant between-group differences with regard to sex, age, Hunt-Hess grade, adequate clipping level, operation time, intraoperative blood loss, and aneurysm rupture (P > 0.05). However, no intraoperative ischemia was detected in group I, whereas 23.1% (6 of 26) of patients in group II had reversible ischemia. Furthermore, the proportion of brain retraction injuries in group I (5.3%) was lower than that in group II (34.6%). In addition, a better prognosis was obtained in patients who underwent retractorless surgery. With the careful and accurate use of a handheld suction device and operating instruments, the retractorless technique can replace fixed retraction, reduce brain retraction injury, and is applicable to surgeries on anterior circulation aneurysms via pterional keyhole approaches.

Minimizing Collateral Brain Injury Using a Protective Layer of Fibrin Glue: Technical Note

BACKGROUND

Neurosurgical procedures expose the brain surface to a constant risk of collateral injury. We describe a technique where the brain surface is covered with a protective layer of fibrin glue and discuss its advantages.

METHODS

A thin layer of fibrin glue was applied on the brain surface after its exposure in 34 patients who underwent different craniotomies for tumoral and vascular lesions. Data of 35 more patients who underwent standard microsurgical technique were collected as a control group. Cortical and pial injuries were evaluated using an intraoperative visual scale. Eventual abnormal signals at the early postoperative T2-weighted fluid-attenuated inversion recovery (T2FLAIR) magnetic resonance imaging (MRI) sequences were evaluated in oncological patients.

RESULTS

Total pial injury was noted in 63% of cases where fibrin glue was not used. In cases where fibrin glue was applied, a significantly lower percentage of 26% (P < 0.01) had pial injuries. Only 9% had injuries in areas covered with fibrin glue (P < 0.0001). Early postoperative T2FLAIR MRI confirmed the differences of altered signal around the surgical field in the two populations.

CONCLUSION

We propose beside an appropriate and careful microsurgical technique the possible use of fibrin glue as alternative, safe, and helpful protection during complex microsurgical dissections. Its intrinsic features allow the neurosurgeon to minimize the cortical manipulation preventing minor collateral brain injury.

A modified anterior temporal approach for low-position aneurysms of the upper basilar complex

Background:

Although surgery for aneurysms of the upper basilar complex is generally accomplished by a pterional or subtemporal approach, both techniques have disadvantages. Therefore, attempts have been made to combine both the approaches, such as an anterior temporal approach, which exposes the anterior aspect of the temporal lobe during standard fronto-temporal craniotomy. However, in all these techniques, the temporal vein is sacrificed to allow posterior retraction of the temporal lobe, which may cause venous infarction in the temporal lobe.

Methods:

Our institutional review board approved this prospective study. We modified the anterior temporal approach for low-position aneurysms of the upper basilar complex by performing posterior clinoidectomy as necessary, thereby preventing the sacrifice of all vessels.

Results:

From 2007 to 2014, seven patients were operated on using this modified approach, and four patients underwent additional posterior clinoidectomy. Complete clip ligation was performed for all aneurysms without sacrificing any vessels, and there were no permanent complications attributable to manipulation for clipping or posterior clinoidectomy.

Conclusions:

The modified anterior temporal approach allows a wider operating field within the retro-carotid space, without sacrificing any vessels, and permits safer posterior clinoidectomy and aneurysm clipping in patients with low-position aneurysms of the basilar complex.

Re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms

BACKGROUND

Unplanned re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms (UIAs) is sometimes required, but the underlying causes and rates of these procedures are seldom reported. This study retrospectively analyzed the causes of such re-explorations to identify methods for decreasing their necessity.

METHOD

From January 2000 to December 2011, 1,720 patients with a total of 1,938 UIAs underwent surgical treatment at our institution. From this cohort, 26 patients (1.5 %) with 38 UIAs required re-exploration. Clinical data, aneurysm characteristics, treatment methods, and the incidence and causes of re-exploration of the craniotomy were analyzed for these 26 patients.

RESULTS

Several causes of re-exploration were identified: compromised distal blood flow (eight patients, 0.47 %), hemorrhagic venous infarction (four patients, 0.23 %), brain retraction injury (three patients, 0.17 %), newly identified aneurysms (three patients, 0.17 %), bleeding from an incompletely clipped aneurysm (two patients, 0.12 %), epidural hematoma (two patients, 0.12 %), failed aneurysm clipping (two patients, 0.12 %) and other causes (two patients, 0.12 %). Annual re-exploration incidence rates ranged from 0 to 3.1 %. Annual incidence rates gradually decreased following the introduction of several intraoperative monitoring systems.

CONCLUSIONS

Precise surgical planning and careful operative techniques can reduce the incidence of unplanned re-exploration of the craniotomy. The introduction of various intraoperative monitoring systems can also contribute to a reduction in this incidence.

Current and future practices in surgical retraction

Retraction of tissues and anatomical structures is an essential component of all forms of surgery. The means by which operative access is gained through retraction are many and diverse. In this article, the various forms of retraction methods currently available are reviewed, with special reference to hand held, self-retaining and compliant techniques. The special challenges posed by laparoscopic surgery are considered and future developments in new retraction techniques are anticipated.

Brain retraction injury

This paper reviews the literature of the brain retraction injury during the last century. The review focused on the instrument characteristic as well as the physiopathological and histopathological damage of the brain induced by brain retraction. It was found that lesions were induced by cerebral ischemia. We conclude that a better monitoring system needs to be developed to avoid brain injury.

Integrating Retraction Modeling Into an Atlas-Based Framework for Brain Shift Prediction

In recent work, an atlas-based statistical model for brain shift prediction, which accounts for uncertainty in the intraoperative environment, has been proposed. Previous work reported in the literature using this technique did not account for local deformation caused by surgical retraction. It is challenging to precisely localize the retractor location prior to surgery and the retractor is often moved in the course of the procedure. This paper proposes a technique that involves computing the retractor-induced brain deformation in the operating room through an active model solve and linearly superposing the solution with the precomputed deformation atlas. As a result, the new method takes advantage of the atlas-based framework's accounting for uncertainties while also incorporating the effects of retraction with minimal intraoperative computing. This new approach was tested using simulation and phantom experiments. The results showed an improvement in average shift correction from 50% (ranging from 14 to 81%) for gravity atlas alone to 80% using the active solve retraction component (ranging from 73 to 85%). This paper presents a novel yet simple way to integrate retraction into the atlas-based brain shift computation framework.

The safety of the intraoperative sacrifice of the deep cerebral veins

BACKGROUND

The effect of surgically ligating the deep cerebral veins is often thought to be of significant risk. That concern and the paucity of information on surgery of the deep venous system confound surgical decision making when operations involve manipulation of the deep cerebral veins.

DISCUSSION

The authors review the human and animal literature on the selective sacrifice of the deep cerebral veins. Robust experimental studies and limited clinical experience indicate that occlusion of one or several deep cerebral veins is generally safe.

Anatomical restrictions in the transsphenoidal, transclival approach to the upper clival region: a cadaveric, anatomic study

OBJECTIVE

Tumours in the clival region are difficult to remove surgically. Before the 1970s, clival tumours had very high mortality and morbidity rates.

METHODS

An anatomic dissection was performed on 24 spheno-occipital bone blocks obtained from 28 adult cadavers. The internal carotid artery, paraclival carotid tubercle, sixth cranial nerve and dorsum sellae in the upper clival region were analyzed qualitatively and quantitatively. For the histological evaluation, 4 samples were decalcified and sagittal sections were cut. From the eight blocks obtained, 32 incisions were made in the axial plane, and the tissue was analyzed.

RESULTS

Using microscopy, a clival recess was clearly identified in 15 of the 24 (62.5%) samples. Paraclival carotid tubercles were observed in 19 (79.16%) of the samples. In the upper clival and petroclival region, the sixth cranial nerve had directional changes at the dural porus, the petrous apex and the lateral wall of the cavernous segment of the internal carotid artery. At the dorsum sellae level, the distance between the medial surfaces of both internal carotid arteries was a mean of 15.33 ± 2.12 mm. This distance at the pharyngeal tubercle was a mean of 38.95 ± 4.67 mm. On all the histological sections, the distance of the sixth cranial nerve from the dural porus to the cavernous sinus was within the basilar plexus, along with the subarachnoid membranes around it. On the petrous apex level, the sixth cranial nerve was fixed to the petrous apex and the internal carotid artery with connective tissue formed by dense collagen fibres. The sixth cranial nerve and the internal carotid artery are tightly surrounded by dense collagen connective tissue, and the relative proximity between the carotids on the dorsum sellae level can be easily damaged during the transsphenoidal-transclival approach. Similarly, due to the ligamentous fixation on the dural porus and the petrous apex surfaces, there is a high risk of injury to the carotid artery and sixth cranial nerve.

CONCLUSION

This study determines the relationship between the sixth cranial nerve and the internal carotid artery at the upper clivus and to provide morphologic details that is essential for the risks of transclival surgery.

Anatomic relationship between the anterior sylvian point and the pars triangularis

The aim of this study was to show morphological sulcal variations of the pars triangularis of the inferior frontal gyrus and to provide a clearer description of the anterior sylvian point. Thirty-six hemispheres of 18 adult cadavers were studied. The hemispheres were harvested by the classical autopsy method and fixed in 10% formalin solution for three weeks. In six hemispheres, the arteries and veins were filled with colored silicone. The proximal and distal segments of the sylvian fissure, the perpendicular distance of both the anterior sylvian point and inferior rolandic point to the insular cortex and the distances between the anterior ascending ramus and the precentral, central, and postcentral sulcus were measured. The anterior horizontal and ascending rami were exposed. The sulcus located on the pars triangularis was appraised. The relationship between the anterior sylvian point and the vascular structure around the sylvian fissure was examined. The rising of the anterior horizontal and ascending ramus from the sylvian fissure defines the shape of the pars triangularis. The pars triangularis has three shapes: V, U, and Y. In V- and Y-shaped pars triangularis both rami merge but in U-shaped pars triangularis the rami do not merge. The pars triangularis was Y-shaped in 30.76% (4/13) of the right hemispheres and in 50% (7/14) of the left hemispheres; U-shaped in 20.3% (3/13) of the right hemispheres and in 35.71% (5/14) of the left hemispheres; V-shaped in 40.61% (6/13) of the right hemispheres and in 14.29% (2/14) of the left hemispheres. Minimally invasive procedures use basic anatomic landmarks intracranially to reach the targeted area; therefore, exact and detailed knowledge of the anatomy of the sylvian fissure and pars triangularis is of great importance.

The endoscopic approach to vestibular schwannomas and posterolateral skull base pathology

This article provides an overview of the technical considerations of endoscopy of the posterolateral skull base and cerebellopontine angle (CPA). Specific areas of focus are on the instrumentation requirements for neuroendoscopy of the CPA; the learning curve associated with this technique; and a complete description of the surgical techniques necessary to perform the procedure, along with outcomes and results. The article provides a general overview of the endoscopic approach to the CPA. For a variety of pathologies, the emphasis is on performing this technique for acoustic tumors and hearing preservation. Insights as to how the author's practice evolved in its use of neuroendoscopic procedures are provided.

Microsurgical resection of deep-seated lesions using transparent tubular retractor: pediatric case series

BACKGROUND

To facilitate effective resection of deep-seated brain lesions without causing significant trauma to the overlying cortex, the authors used a transparent plastic tubular retractor to approach these lesions.

METHODS

Between July 2009 and January 2011, we used an 11-mm diameter transparent plastic tubular retractor in combination with a frameless stereotactic navigation system to remove 18 deep lesions.

RESULTS

Gross total resection of the lesions was achieved in 14 of 18 patients, and subtotal removal occurred in four patients. Effective resection of lesions was achieved in all patients through small size craniotomy window and small cortical incision. The histopathologic diagnosis was established in all 18 patients: 3 hematomas, 3 cavernous angioma, 7 low-grade glioma, 2 dysembryoplastic neuroepithelial tumor, 1 choroid plexus papilloma, 1 abscess, and 1 meningioma.

CONCLUSION

Microsurgery using a transparent tubular retractor guided by a neuronavigation system facilitated accurate and effective removal of these deep-seated brain lesions.

Infratentorial approach to internal acoustic meatus

Surgical exposure of internal acoustic meatus via typical suboccipital retrosigmoid craniotomy is limited by inner ear structures that should remain intact if hearing preservation is attempted. Feasibility of supracerebellar-infratentorial approach to the meatus with more medial angle of exposure and with preservation of inner ear structures was studied on fresh cadavers and on computed tomography pictures of temporal bones. Anatomical relationships of internal acoustic meatus and adjacent structures show marked individual variability. When typical retrosigmoid craniotomy is used to expose meatal fundus, significant medial retraction of cerebellar hemisphere is required in 47% of the patients to avoid opening endolymphatic spaces. Internal acoustic foramen and meatus can be exposed via craniotomy situated under transverse sinus, with 10-15 mm downward retraction of cerebellum. Medial extent of craniotomy can be planned on preoperative imaging studies. Infratentorial supracerebellar exposure of internal acoustic meatus allows for more medial angle of surgical approach than standard retrosigmold craniotomy. It can be used when preoperative imaging studies show that anatomical relationships between internal acoustic meatus and inner ear structures would require excessive cerebellar retraction to visualize a whole tumor inside meatus.

Reoperation as a result of raised intracranial pressure associated with cyst formation in tumor cavity after intracranial tumor resection: a report of two cases

Reoperation as a result of increased intracranial pressure (ICP) associated with cyst formation in an intracranial tumor resection cavity is a rare clinical condition. We report two cases of reoperation as a result of raised ICP associated with cyst formation in the tumor resection cavity, one arising after glioma resection and the other after meningioma resection. In both cases, a "valve"-like structure was noted intraoperatively in the roof region of the tumor resection cavity. Surgical resection of the "valve"-like structure led to slow regression over several months after the reoperation rather than to immediate disappearance of the cyst. Both cases illustrate that the "valve"-like structure formed in the roof region of the tumor resection cavity may be responsible for cyst formation. Surgical resection of it provides good long-term outcomes in such patients though short-term outcomes are unsatisfactory; we speculate that if the resection of the cortical tissue around the "valve"-like structure is enough wide, its return may be avoided.

Stitch retractor--simple and easy technique to retract brain

BACKGROUND

Self-retaining brain retractors are commonly used during intracranial surgery, and they are indispensable during microneurosurgery. There is a common severe complication due to the use of self-held retractors, that is, formation of a hemorrhagic infarct area in the brain region exposed to traction. All the more, present retractor systems are fixed and rigid and obstruct surgeons during surgery. Sometimes these retractors create glare in the microscope that distracts the surgeon. We hereby propose a simple and easy method of retraction of brain especially the temporal lobe using the transsylvian approach and vermis using the transvermian approach.

METHODS

This is retrospective analysis of 47 patients in 4 years in which we have used our stitch retractor. We have analyzed their outcome, postoperative scan, and ease of performing surgery.

RESULTS

In 47 patients, there was only 1 postoperative contusion, and the longest period it was kept for is 6 hours. The other advantage was that it does not obstruct in any way while doing dissections and surgery. There was no glare while operating under a microscope.

CONCLUSION

We hereby propose a simple and easy method of retraction of brain especially the temporal lobe using the transsylvian approach and vermis using the transvermian approach. It is minimally traumatic, reducing insult to the brain. It allows the surgeon to dissect without any obstruction and glare in the way. The biggest advantage of the present stitch retractor is that it is very cheap and simple to use.

IHAST II and the response of neuroanaesthetists

Deliberate mild hypothermia was first used in 1955 as an intraoperative technique to ameliorate new neurological deficits following cerebral aneursym clipping, and subsequently was also used following neonatal asphyxia, head trauma and cardiac arrest. The Intraoperative Hypothermia for Aneurysm Surgery Trial (IHAST II) randomized control trial was designed to determine the effectiveness of mild hypothermia to decrease neurological deficits following aneurysm surgery. No overall benefit was demonstrated in the hypothermic group versus normothermic group (67% versus 63% good outcome; p=0.32), with a higher rate of bacteraemia in the hypothermic group (5% versus 3%; p=0.05). We undertook a survey of Australasian and Asian neuroanaesthetists to determine whether their thermal management of patients undergoing cerebral aneursym clipping had changed in response to the IHAST II trial results.

Endovascular embolization vs surgical clipping in treatment of cerebral aneurysms: morbidity and mortality with short-term outcome

BACKGROUND

Endovascular embolization of cerebral aneurysms has evolved rapidly worldwide within the last years, and has gained more popularity at the expense of surgical clipping; however, both regimens have inherent risks. This study was undertaken to asses the cerebral complications associated with both modalities of cerebral aneurysm treatment.

METHODS

We retrospectively reviewed the charts, operative and embolization reports, and imaging of patients who underwent surgical clipping or embolization for cerebral aneurysms at our institution between October 2001 and October 2004. Patients were divided into 2 groups: group A, patients who had confirmed subarachnoid hemorrhage; group B, patients with unruptured cerebral aneurysms. Patients belonging to group A were evaluated according to the Hunt and Hess scale with their computed tomography scan evaluated according to Fisher scale. Short-term outcome was measured with Glasgow Outcome Scale for both groups.

RESULTS

One hundred thirty-three patients with 168 aneurysms were treated; 95 (71.4%) were women and 38 (28.6%) men; mean age was 60.28 years. Hypertension (29.6%) was the most commonly encountered risk factor; average size of aneurysms treated was 7.21 mm; 53 patients belonged to group A. Seven patients were Hunt and Hess grade I, 23 grade II, 11 grade III, 7 grade IV, and 5 grade V. Eighty patients belonged to group B; for both groups, the periprocedural technical complication rate associated with coiling was 8.4% vs 19.35% with clipping. Follow-up angiographic results were better with clipping, as total aneurysm occlusion was 81.4% vs 57.5% with coiling. In group A, the incidence of angiographic vasospasm was 17.4% vs 45.4% with coiling vs clipping, whereas the incidence of shunt-dependant hydrocephalus was comparable with embolization and clipping. In group A, excellent outcome was achieved in 62% vs 44% (endovascular vs surgical) of subgroups, whereas in group B, it was 93% vs 81%, respectively.

CONCLUSION

With rapidly evolving technology of endovascular embolization, accumulated experience, and good selection of patients with optimum angioanatomical criteria and endovascular accessibility, our results of morbidity and mortality associated with both modalities of cerebral aneurysm treatment with short-term outcome show that endovascular embolization of cerebral aneurysms is a safe alternative to surgical clipping in the treatment of both ruptured and unruptured cerebral aneurysms; however, long-term outcome needs to be evaluated.

Cerebral microdialysis and positron emission tomography after surgery for aneurysmal subarachnoid hemorrhage in grade I patients

BACKGROUND

Using cerebral microdialysis, baseline values for energy-related chemical markers have been reported in awake patients. Radionuclide studies have demonstrated a locally decreased metabolism, thought to be the result of brain retraction. These baseline values, however, may not be applicable to patients after surgical aneurysm repair following a subarachnoid hemorrhage (SAH). We assessed metabolic chemical marker levels in World Federation of Neurological Surgeons Committee (WFNS) grade I SAH patients after aneurysm surgery and compared them with previously reported baseline values.

METHODS

In 5 WFNS grade I SAH patients, energy-related chemical marker levels were obtained using microdialysis in the area of brain retraction after aneurysm surgery. In addition, an [(18)F]2-deoxy-d-glucose positron emission tomography (FDG-PET) was performed.

RESULTS

The FDG-PET showed a decrease of glucose metabolism in the frontotemporal area. Comparing the mean values for chemical markers of this study with reported baseline values, the most striking difference was a mild decrease of pyruvate and an increase of the lactate/pyruvate ratio. In individual patients, some markers indicated possible ischemia. A consistent pattern or ischemic profile for all markers, however, was not found.

CONCLUSION

FDG-PET scanning confirmed postoperative metabolic changes found in previous studies. Mean interstitial chemical marker levels ranged from normal to mildly deviant compared with reference chemical marker levels for awake patients and are likely to be applicable in SAH patients after aneurysm repair.

Prise en charge du patient neurochirurgical avec tumeur intracrânienne

1. Neurological state of patient.

PROCEDURES

(low risk of ICP problems or ischemia, little need for brain relaxation). - Volatile-based technique; "high-risk" procedures (anticipated ICP problems, significant risk of intraoperative cerebral ischemia, need for excellent brain relaxation): use total intravenous anaesthesia. EXTRACRANIAL MONITORING: For example, cardiovascular or renal, venous air embolism. Intracranial monitoring. - General environment vs. specific functions-metabolic (jugular venous bulb), neurophysiological (EEG/EP), functional (transcranial Doppler). 4. Induction of anaesthesia.

GOALS

Ventilatory control (early mild hyperventilation; avoid hypercapnia, hypoxemia); blood pressure control (avoid CNS arousal: adequate antinociception, anaesthesia); optimal position on ICP-volume curve. PATIENT POSITIONING: Pin holder application --> maximal nociceptive stimulus, block by deeper anaesthesia or analgesia and local anesthetic pin site infiltration. Alternative: antihypertensives. 5. Maintenance of anaesthesia.

GOALS

Controlling brain tension via control of CMR and CBF: preventing CNS arousal (depth of anaesthesia, antinociception); treating consequences of CNS arousal (sympatholysis, antihypertensives); the "chemical brain retractor concept". NEUROPROTECTION: Maintenance of an optimal intracranial environment (matching cerebral substrate demand and supply). 6. Emergence from anaesthesia.

GOALS

Maintain intra/extracranial homeostasis. Avoid factors --> intracranial bleeding and/or increasing CBF/ICP. The patient should be calm, co-operative and responsive to verbal commands soon after emergence. EARLY VS. LATE EMERGENCE: Ideal: rapid emergence to permit early assessment of surgical results and postoperative neurological follow-up, but there are still some categories of patients where early emergence is not appropriate.

Modelling of interaction between a spatula and a human brain

This paper describes a method for surgery simulation, or more specifically a learning system of how to use a brain spatula. Improper use of brain spatulas can lead to brain tissue lesions such as tearing of brain tissue and ischemia. The idea is to provide surgeons with a tool which can teach them the correlation between deformation and applied force. The system includes a Finite Element based model of the brain in a Virtual Reality setup with haptic feedback. The physical model links the shape of the deformable model with the associated force. The interaction between the spatula and the brain model is handled by a collision response method which aims at smoothing the discrete haptic feedback. The experimental results are promising even though the used force feedback device is somewhat constraining the realism.

Arousal in Drosophila

Arousal can be described as an endogenously generated or exogenously induced change in behavioral responsiveness. Changes in levels of arousal, such as occur during sleep or attention, most likely accomplish adaptive functions common to most animals. Recent evidence demonstrating changing arousal states in Drosophila melanogaster complements other behavioral research in this model organism. Herein we review the methodology related to the study of circadian rhythms, sleep and anesthesia where arousal, or lack of it, plays an essential role. We end this review by discussing a new method that allows for the first time to correlate changes in brain electrophysiology to changes in behavioral arousal in the fruit fly.