Modern Brain Retractors and Surgical Brain Injury: A Review

Intrasylvian Retraction Technique to Facilitate the Sylvian Fissure Dissection: A Clinical Study of 125 Cases

Although many authors have recommended the retractorless technique to avoid retractor-induced brain injury, others usually use brain retractors with a meticulous technique to facilitate the surgery, especially for sylvian fissure dissection. The intrasylvian retraction technique was described for sylvian fissure opening, but no clinical evidence was found. We evaluate the efficacy and safety of this technique for the distal transsylvian approach. We reviewed the video records of clinical cases where the distal transsylvian approach was performed using the intrasylvian retraction technique for aneurysm treatment and middle cerebral artery (MCA) bypass between September 2018 and August 2022. Operative techniques are described. The efficacy and safety of the technique were assessed by full exposure of the sylvian fissure and new postoperative perisylvian hematoma, respectively. One hundred twenty-five cases were included and had an average age of 53.5 (range 16-85) years. Women comprised 73.6%. Aneurysm surgery, pure MCA revascularization, and aneurysm surgery with MCA revascularization were 106 (84.8%), 12 (9.6%), and 7 cases (5.6%), respectively. The most common aneurysm location was the internal carotid artery-posterior communicating artery junction in 37 cases (34.9%), followed by the anterior communicating artery in 27 (25.5%). Full exposure of the Sylvian fissure was achieved in all cases. No perisylvian hematoma was detected by immediate postoperative computed tomography in any patient. Using an appropriate technique for brain retractor application, sylvian fissure dissection was safely performed. The intrasylvian retraction technique effectively facilitated sylvian fissure dissection and provided wide exposure for the distal transsylvian approach.

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.

A Novel Foley Catheter-Based Brain Retraction Method for the Interhemispheric Approach: Technical Considerations and an Illustrative Video

BACKGROUND

Management of interhemispheric pathologies requires surgical intervention through a restricted anatomical corridor ensconced within critical cerebral structures. The use of retractors to facilitate operative access may cause damage to cerebral tissue. The development of an innovative retraction technique designed to alleviate cerebral damage in such cases is imperative. In this study, we present a novel and gentle retraction method to facilitate the interhemisferic approach.

METHODS

We retrospectively examined data of 9 right-handed patients who underwent surgical resection of interhemispheric lesions between 2021 and 2022. All patients underwent surgery for the first time because of this pathology. All operative specimens were histologically confirmed. Clinical characteristics, operative details, and follow-up data were retrospectively analyzed.

RESULTS

The new retraction technique was successfully applied to 8 tumor patients and 1 patient with an aneurysm. Eight patients had an anterior interhemispheric approach, and 1 patient had a posterior interhemispheric approach. Complete surgical excision was achieved in all patients with no postoperative complications. Postoperative Gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) showed no signs of ischemia or contusion. All patients exhibited significant improvements in their symptoms. An illustrative video that elucidates the removal of an interhemispheric epidermoid tumor, employing the anterior ipsilateral interhemispheric approach, featuring the novel retraction method.

CONCLUSIONS

The ideal retraction technique during the interhemispheric approach is still a challenge. Our novel retraction technique may help minimize brain parenchymal damage during surgical resection of interhemispheric lesions.

Neutrophil Extracellular Traps Regulate Surgical Brain Injury by Activating the cGAS-STING Pathway

Surgical brain injury (SBI), induced by neurosurgical procedures or instruments, has not attracted adequate attention. The pathophysiological process of SBI remains sparse compared to that of other central nervous system diseases thus far. Therefore, novel and effective therapies for SBI are urgently needed. In this study, we found that neutrophil extracellular traps (NETs) were present in the circulation and brain tissues of rats after SBI, which promoted neuroinflammation, cerebral edema, neuronal cell death, and aggravated neurological dysfunction. Inhibition of NETs formation by peptidylarginine deiminase (PAD) inhibitor or disruption of NETs with deoxyribonuclease I (DNase I) attenuated SBI-induced damages and improved the recovery of neurological function. We show that SBI triggered the activation of cyclic guanosine monophosphate-adenosine monophosphate synthase stimulator of interferon genes (cGAS-STING), and that inhibition of the cGAS-STING pathway could be beneficial. It is worth noting that DNase I markedly suppressed the activation of cGAS-STING, which was reversed by the cGAS product cyclic guanosine monophosphate-adenosine monophosphate (cGMP-AMP, cGAMP). Furthermore, the neuroprotective effect of DNase I in SBI was also abolished by cGAMP. NETs may participate in the pathophysiological regulation of SBI by acting through the cGAS-STING pathway. We also found that high-dose vitamin C administration could effectively inhibit the formation of NETs post-SBI. Thus, targeting NETs may provide a novel therapeutic strategy for SBI treatment, and high-dose vitamin C intervention may be a promising translational therapy with an excellent safety profile and low cost.

Endoscopic Cylinder Surgery for Ventricular Lesions

Cylinder retractors have been developed to reduce the risk of brain retraction injury during surgery by dispersing retraction pressure on the brain. In recent years, various types of cylinder retractors have been developed and widely used in neurosurgery. The ventricles, being deep structures within the brain, present an effective area for cylinder retractor utilization. Endoscopy provides a bright, wide field of view in the deep surgical field, even through narrow corridors.This chapter introduces surgical techniques using an endoscope through a cylinder. Given the deep and complex shapes of the ventricles, preoperative planning is paramount. Two main surgical techniques are employed in endoscopic cylinder surgery. The wet-field technique involves the continuous irrigation of artificial cerebrospinal fluid (CSF) during the procedure, maintaining ventricle shape with natural water pressure, facilitating tumor border identification, and achieving spontaneous hemostasis. Conversely, the dry-field technique involves CSF drainage, providing a clear visual field even during hemorrhage encounters. In intraventricular surgery, both techniques are used and switched as needed.Specific approaches for lateral, third, and fourth ventricular tumors are discussed, considering their locations and surrounding anatomical structures. Detailed intraoperative findings and strategies for tumor removal and hemostasis are presented.Endoscopic cylinder surgery offers a versatile and minimally invasive option for intraventricular tumors, leading to improved surgical outcomes. Overall, this technique enhances surgical precision and patient outcomes in intraventricular tumor cases.

Impact of Preoperative Mapping and Intraoperative Neuromonitoring in Minimally Invasive Parafascicular Surgery for Deep-Seated Lesions

BACKGROUND

Transsulcal tubular retractor-assisted minimally invasive parafascicular surgery changes the surgical strategy for deep-seated lesions by promoting a deficit-sparing approach. When integrated with preoperative brain mapping and intraoperative neuromonitoring (IONM), this approach may potentially improve patient outcomes. In this study, we assessed the impact of preoperative brain mapping and IONM in tubular retractor-assisted neuro-oncological surgery.

METHODS

This retrospective single-center cohort study included patients who underwent transsulcal tubular retractor-assisted minimally invasive parafascicular surgery for resection of deep-seated brain tumors from 2016 to 2022. The cohort was divided into 3 groups: group 1, no preoperative mapping or IONM (17 patients); group 2, IONM only (25 patients); group 3, both preoperative mapping and IONM (38 patients).

RESULTS

We analyzed 80 patients (33 males and 47 females) with a median age of 46.5 years (range: 1-81 years). There was no significant difference in mean tumor volume (26.2 cm3 [range 1.07-97.4 cm3]; P = 0.740) and mean preoperative depth of the tumor (31 mm [range 3-65 mm], P = 0.449) between the groups. A higher proportion of high-grade gliomas and metastases was present within group 3 (P = 0.003). IONM was related to fewer motor (P = 0.041) and language (P = 0.032) deficits at hospital discharge. Preoperative mapping and IONM were also related to shorter length of stay (P = 0.008).

CONCLUSIONS

Preoperative and intraoperative brain mapping and monitoring enhance transsulcal tubular retractor-assisted minimally invasive parafascicular surgery in neuro-oncology. Patients had a reduced length of stay and prolonged overall survival. IONM alone reduces postoperative neurological deficit.

Neuroendoscopy: The State of the Art

Over the past century, neuroendoscopy developed into a mainstay of neurosurgical practice, allowing for minimally invasive approaches to the ventricles, skull base, and spine. Its development, however, is far from over. Current challenges are inherent in the very feature that renders neuroendoscopy appealing-the small channels of the modern endoscope allow surgery to be performed with minimal tissue retraction, but they also make hemostasis and resection of large masses difficult. New optics allow for significantly improved image quality; yet open craniotomy often allows for 3-dimensional visualization and bimanual dissection and is part of everyday neurosurgical training. Finally, the utilization of neuroendoscopy remains limited, presenting ongoing challenges for neurosurgical teaching and achievement of technical mastery.

Cerebral corridor creator for resection of trigone ventricular tumors: Two case reports

BACKGROUND

Resection of deep intracranial tumors requires significant brain retraction, which frequently causes brain damage. In particular, tumor in the trigone of the lateral ventricular presents a surgical challenge due to its inaccessible location and intricate adjacent relationships with essential structures such as the optic radiation (OR) fibers. New brain retraction systems have been developed to minimize retraction-associated injury. To date, there is little evidence supporting the superiority of any retraction system in preserving the white matter tract integrity. This report illustrates the initial surgical excision in two patients using a new retraction system termed the cerebral corridor creator (CCC) and demonstrates its advantage in protecting OR fibers.

CASE SUMMARY

We report two patients with nonspecific symptoms, who had trigone ventricular lesions that involved the neighboring OR identified on preoperative diffusion tensor imaging (DTI). Both patients underwent successful surgical excision using the CCC. Total tumor removal was achieved without additional neurological deficit. DTI showed that the OR fibers were preserved along the surgical field. Preoperative symptoms were alleviated immediately after surgery. Clinical outcomes were improved according to the Glasgow-Outcome-Scale and Activity-of-Daily-Living Scale assessments.

CONCLUSION

In the two cases, the CCC was a safe and useful tool for creating access to the deep trigonal area while preserving the white matter tract integrity. The CCC is thus a promising alternative brain retractor.

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.

Targeting integrated stress response regulates microglial M1/M2 polarization and attenuates neuroinflammation following surgical brain injury in rat

Integrated stress response (ISR) contributes to various neuropathological processes and acting as a therapy target in CNS injuries. However, the fundamental role of ISR in regulating microglial polarization remains largely unknown. Currently no proper pharmacological approaches to reverse microglia-driven neuroinflammation in surgical brain injury (SBI) have been reported. Here we found that inhibition of the crucial ISR effector, activating transcription factor 4 (ATF4), using the RNA interference suppressed the lipopolysaccharide (LPS)-stimulated microglial M1 polarization in vitro. Interestingly, counteracting ISR with a small-molecule ISR inhibitor (ISRIB) resulted in a significant microglial M1 towards M2 phenotype switching after LPS treatment. The potential underlying mechanisms may related to downregulate the intracellular NADPH oxidase 4 (NOX4) expression under the neuroinflammatory microenvironment. Notably, ISRIB ameliorated the infiltration of microglia and improved the neurobehavioral outcomes in the SBI rat model. Overall, our findings suggest that targeting ISR exerts a novel anti-inflammatory effect on microglia via regulating M1/M2 phenotype and may represent a potential therapeutic target to overcome neuroinflammation following SBI.