The "subdural" space: a new look at an outdated concept

Biomimetic and Nonbiomimetic Approaches in Dura Substitutes: The Influence of Mechanical Properties

The dura mater, the furthest and strongest layer of the meninges, is crucial for protecting the brain and spinal cord. Its biomechanical behavior is vital, as any alterations can compromise biological functions. In recent decades, interest in the dura mater has increased due to the need for hermetic closure of dural defects prompting the development of several substitutes. Collagen-based dural substitutes are common commercial options, but they lack the complex biological and structural elements of the native dura mater, impacting regeneration and potentially causing complications like wound/postoperative infection and cerebrospinal fluid (CSF) leakage. To face this issue, recent tissue engineering approaches focus on creating biomimetic dura mater substitutes. The objective of this review is to discuss whether mimicking the mechanical properties of native tissue or ensuring high biocompatibility and bioactivity is more critical in developing effective dural substitutes, or if both aspects should be systematically linked. After a brief description of the properties and architecture of the native cranial dura, we describe the advantages and limitations of biomimetic dura mater substitutes to better understand their relevance. In particular, we consider biomechanical properties' impact on dura repair's effectiveness. Finally, the obstacles and perspectives for developing the ideal dural substitute are explored.

Contemporary Management of Subdural Hematoma

This review provides a comprehensive overview of the contemporary management strategies for acute and chronic subdural hematomas, delineating their distinct clinical characteristics, risk factors, etiologies, and treatment paradigms. Through a synthesis of current evidence and emerging trends, this review explores established therapeutic strategies alongside innovative modalities under active investigation. This article equips clinicians with a nuanced understanding of optimal care pathways for both acute and chronic subdural hematomas, thus facilitating improved patient outcomes.

Role of Sulcal Hyperintensity and Web/Net Appearance on MRI in Patients With Chronic Subdural Hematoma Presenting With Transient Neurological Deficits

BACKGROUND AND OBJECTIVES

Transient neurological deficits (TNDs) in patients with chronic subdural hematoma (CSDH), such as fluctuating aphasia, hemiparesis, or sensory disturbances, present diagnostic and treatment challenges as their pathophysiology remains unclear. The aim of this study was to investigate the association between specific MRI findings and TNDs in patients with CSDH and explored their relationship through intraoperative observation.

METHODS

We retrospectively evaluated 72 patients with CSDH who underwent preoperative MRI among 251 CSDH patients treated from January 2020 to December 2023. Sulcal hyperintensity (SHI) on fluid-attenuated inversion recovery images and web/net appearance (W/N) on T2*-weighted images were assessed and their association with TNDs was analyzed. Flexible neuroendoscopic surgery (FNS) was performed on 8 patients with TNDs exhibiting these MRI findings, allowing intraoperative observation of intrahematoma conditions. Histopathological examination was performed on hematoma samples.

RESULTS

Thirteen patients (5.2%) presented with preoperative TNDs. Diffuse SHI and W/N were strongly associated with preoperative TNDs (odds ratio = 150.0, P < .001). FNS revealed organized hematomas with inflammatory changes corresponding to the SHI and W/N seen on MRI. Patients who underwent FNS experienced complete resolution of TNDs postprocedure, with diffuse SHI disappearing by one month. No recurrence was observed at a mean follow-up of 5.9 months.

CONCLUSION

This study provided the first evidence that the combination of diffuse SHI and W/N on MRI strongly correlates with TNDs in patients with CSDH, serving as valuable diagnostic indicators. These findings will aid in guiding surgical approach selection and facilitate more personalized treatment strategies for patients with CSDH presenting with TNDs.

Diffusion-weighted imaging findings predictive of postoperative recurrence of chronic subdural hematoma

OBJECTIVES

To identify the brain magnetic resonance imaging (MRI) findings associated with the postoperative recurrence of chronic subdural hematoma (CSDH).

METHODS

We examined 1099 consecutive patients admitted to our hospital with CSDH between 2005 and 2014. Of those, 1021 who underwent surgery for CSDH and were followed-up for >3 months after surgery were included. Preoperative brain MRI findings were classified as homogeneous, laminar, separate, or trabecular, according to the nature of the hematoma. Postoperative recurrence was defined in patients who required reoperation for ipsilateral hematoma growth within three months of surgery. The clinical and radiological factors associated with postoperative recurrence were evaluated using univariate and multivariate analyses.

RESULTS

Of the 1021 CSDH patients with CSDH who underwent surgery, 91 (8.9%) experienced postoperative recurrence. Postoperative recurrence was significantly associated with male sex (p = 0.0004) and hematoma volume (p < 0.0001). Additionally, isotype or separate types of hematoma on computed tomography (CT) (p < 0.0001) and laminar/separate types of hematoma types on MRI (p = 0.0008) were significant. Multivariate analysis revealed odds ratios of 2.50 (95% CI, 1.45-4.61; p = 0.0007) for male sex and 3.05 (95% CI, 1.95-4.87; p < 0.0001) for iso/separate hematoma types in CT. Conversely, among the patients who underwent MRI, multivariate analysis revealed odds ratios of 4.33 (95% CI, 1.20-27.92; p = 0.001) for male sex and 4.88 (95% CI, 1.90-14.18; p = 0.023) for laminar/separate hematoma types.

CONCLUSION

While distinguishing the nature of hematomas is challenging with brain CT examination, detailed laminar/trabecular differentiation using MRI images may predict postoperative recurrence.

Middle meningeal artery embolization for chronic subdural hematoma refractory to Burr hole surgery: A case report

Middle meningeal artery embolization is a valuable alternative for chronic subdural hematoma refractory to Burr hole surgery. In a 61-year-old patient, this endovascular intervention effectively resolved the hematoma alleviating associated symptoms.

Post-traumatic hematoma of the "transdural" virtual space. A possible cause of incorrect surgical treatment of epidural hematomas

The space existing between the external and internal dural layer has been anatomically described as a virtual space; no clear clinical significance has been given to it to date. We hereby describe a case of a child with what was expected to be a purely epidural hematoma, at surgery, was found to be composed of two equally coexistent components, one in the epidural space and the second one between the two dural layers. The recognition of a possible involvement of the transdural space in the case of post-traumatic epidural hematomas is relevant for a correct conclusion of the surgical treatment of epidural hematomas, extensively considered basic practice among neurosurgical procedures.

Molecular anatomy of adult mouse leptomeninges

Leptomeninges, consisting of the pia mater and arachnoid, form a connective tissue investment and barrier enclosure of the brain. The exact nature of leptomeningeal cells has long been debated. In this study, we identify five molecularly distinct fibroblast-like transcriptomes in cerebral leptomeninges; link them to anatomically distinct cell types of the pia, inner arachnoid, outer arachnoid barrier, and dural border layer; and contrast them to a sixth fibroblast-like transcriptome present in the choroid plexus and median eminence. Newly identified transcriptional markers enabled molecular characterization of cell types responsible for adherence of arachnoid layers to one another and for the arachnoid barrier. These markers also proved useful in identifying the molecular features of leptomeningeal development, injury, and repair that were preserved or changed after traumatic brain injury. Together, the findings highlight the value of identifying fibroblast transcriptional subsets and their cellular locations toward advancing the understanding of leptomeningeal physiology and pathology.

Rehabilitation of Traumatic Acute Subdural Hematoma and Subarachnoid Hemorrhage: A Case Report

A head injury or cerebrovascular illness may be the cause of acute intracranial hemorrhage. Making a precise diagnosis is challenging since diagnostic imaging might be challenging in both situations. In this case report, an aneurysmal rupture related head injury resulted in an acute subdural hematoma (SHD) after the patient lost consciousness. A 54-year-old male was found in a state of unconsciousness on the ground and was brought to the nearest hospital. Computed tomography (CT) scan showed an oblique fracture involving the bilateral frontal and right parietal bones along with underlying SDH, subarachnoid hemorrhage (SAH), and hemorrhagic contusion along with midline shift. The case report highlights the rehabilitation journey of a patient with acute SDH and SAH. The patient can now sit independently and stand with minimal assistance. Vasospasm detection, prevention, and treatment need to be the norm at that time. This case demonstrates the effectiveness of a comprehensive rehabilitation approach in promoting mobility and independence for patients with traumatic brain injuries.

Widespread distribution of lymphatic vessels in human dura mater remote from sinus veins

Background and purpose: Previous experimental studies have shown that meningeal lymphatic vessels are located primarily along the walls of the dural sinus veins. Whether they are more widespread throughout human dura mater has presently not been characterized. The present study explored in humans whether meningeal lymphatic vessels may be identified remote from the sinus veins and whether they differ in the various location of dura mater. Methods: We included 15 patients who underwent neurosurgery, in whom dura mater was removed as part of the planned procedure. Tissue was prepared for immunohistochemistry using the lymphatic endothelial cell markers lymphatic vessel endothelial hyaluronan receptor 1 protein (LYVE-1), podoplanin and vascular endothelial growth factor receptor 3 (VEGFR3). Results: Lymphatic endothelial cell positive cells were found in dura mater at the posterior fossa (n = 8), temporal skull base (n = 5), frontal convexity (n = 1), and cranio-cervical junction (n = 1). They were most commonly seen remote from blood vessels, but also occurred along blood vessels, and seemed to be most abundant at the skull base. Conclusion: The present observations show that human lymphatic vessels are widespread in dura mater, not solely lining the dural sinuses.

The interdural hematoma: A subtype of convexity subdural/dural hematoma with specific radioanatomical characteristics

Background

Rare cases of biconvex hematomas splitting the convexity dura mater were reported and denominated interdural hematoma (IDH). Due to their rarity, little is known about their radiological characteristics, and in most cases, their invasive management with craniotomy and dural membrane excision is unnecessary.

Case Description

We report here a case of single burr-hole endoscopic evacuation of an IDH and its complete resolution after the 6-month follow-up imaging. The literature review reveals 11 reported cases of IDH. Most of them are male and the mean age is 65 years (range 51-90). Most of the reported IDHs were misdiagnosed as epidural hematoma or meningioma, and therefore, they have been managed invasively through craniotomy with dural excision. Diagnosis of the interdural nature was confirmed macroscopically during surgery in all cases and histology was reported for 6 cases. Image analysis found a double dural beak sign and biconvex shape on coronal planes, subarachnoid space enlargement at the collection extremities, and irregular thick inner wall as common radiological aspects of the IDH.

Conclusion

IDH is a rarely reported and often misdiagnosed dural hematoma subtype. Its invasive treatment through craniotomy is likely related to its unknown radiological characteristics. We review and raise awareness about potentially unique radiological anatomy that could avoid unnecessary invasive treatment. Moreover, we report the first case of endoscopically evacuated IDH with long-term follow-up imaging showing complete resolution.

Utility of balanced steady-state field precession sequence in the evaluation of retinal and subdural hemorrhages in patients with abusive head trauma

Abusive head trauma is the leading cause of physical child abuse deaths in children under 5 years of age in the United States. To evaluate suspected child abuse, radiologic studies are typically the first to identify hallmark findings of abusive head trauma including intracranial hemorrhage, cerebral edema, and ischemic injury. Prompt evaluation and diagnosis are necessary as findings may change rapidly. Current imaging recommendations include brain magnetic resonance imaging with the addition of a susceptibility weighted imaging (SWI) sequence which can detect additional findings that suggest abusive head trauma including cortical venous injury and retinal hemorrhages. However, SWI is limited due to blooming artifacts and artifacts from the adjacent skull vault or retroorbital fat, which can affect the evaluation of retinal, subdural, and subarachnoid hemorrhages. This work explores the utility of the high-resolution, heavily T2 weighted balanced steady-state field precession (bSSFP) sequence to identify and characterize retinal hemorrhage and cerebral cortical venous injury in children with abusive head trauma. The bSSFP sequence provides distinct anatomical images to improve the identification of retinal hemorrhage and cortical venous injury.

Photosealing of dural defects using a biocompatible patch

PURPOSE

Photosealing of many biological tissues can be achieved using a biocompatible material in combination with a dye that is activated by visible light to chemically bond over the tissue defect via protein cross-linking reactions. The aim of this study was to test the efficacy of photosealing using a commercially available biomembrane (AmnioExcel Plus) to securely close dural defects in comparison to another sutureless method (fibrin glue) in terms of repair strength.

METHODS

Two-millimeter diameter holes were created in dura harvested from New Zealand white rabbits and repaired ex vivo using one of two methods: (1) in n = 10 samples, photosealing was used to bond a 6-mm-diameter AmnioExcel Plus patch over the dural defect, and (2) in n = 10 samples, fibrin glue was used to attach the same patch over the dural defect. Repaired dura samples were then subjected to burst pressure testing. Histological analysis was also performed of photosealed dura.

RESULTS

The mean burst pressures of rabbit dura repaired with photosealing and fibrin glue were 302 ± 149 mmHg and 26 ± 24 mmHg, respectively. The increased repair strength using photosealing was statistically significant and considerably higher than the normal intracranial pressure of ~ 20 mmHg. Histology demonstrated a tight union at the interface between the dura surface and patch with no disruption of the dura structure.

CONCLUSION

The results of this study suggest that photosealing performs better than fibrin glue for the fixation of a patch for ex vivo repair of small dural defects. Photosealing is worthy of testing in pre-clinical models for the repair of dural defects.

Factors that Influence Subdural Hemorrhage Secondary to Intracranial Arachnoid Cysts in Children

OBJECTIVE

This study aimed to investigate factors that influence subdural haemorrhage (SDH) secondary to intracranial arachnoid cysts (IACs) in children.

METHODS

Data of children with unruptured IACs (IAC group) and those with SDH secondary to IACs (IAC-SDH group) were analyzed. Nine factors, sex, age, birth type (vaginal or caesarean), symptoms, side (left, right, or midline), location (temporal or nontemporal), image type (I, II, or III), volume, and maximal diameter, were selected. IACs were classified as types I, II, and III according to their morphological changes observed on computed tomography images.

RESULTS

There were 117 boys (74.5%) and 40 girls (25.5%); 144 (91.7%) patients comprised the IAC group and 13 (8.3%) comprised the IAC-SDH group. There were 85 (53.8%) IACs on the left side, 53 (33.5%) on the right side, 20 (12.7%) in the midline region, and 91 (58.0%) in the temporal region. The univariate analysis showed significant differences in age, birth type, symptoms, cyst location, cyst volume, and cyst maximal diameter (P < 0.05) between the 2 groups. Logistic regression using the synthetic minority oversampling technique model showed that image type III and birth type were independent factors that influenced SDH secondary to IACs (β0 = 4.143; β for image type = -3.979; β for birth type = -2.542) and that the representative area under the receiver-operating characteristic curve value was 0.948 (95% confidence interval, 0.898-0.997).

CONCLUSIONS

IACs are more common in boys than in girls. They can be divided into 3 groups according to their morphological changes on computed tomography images. Image type III and caesarean delivery were independent factors that influenced SDH secondary to IACs.

Surgical techniques for evacuation of chronic subdural hematoma: a mini-review

Chronic subdural hematoma is one of the most common neurosurgical pathologies with over 160,000 cases in the United States and Europe each year. The current standard of care involves surgically evacuating the hematoma through a cranial opening, however, varied patient risk profiles, a significant recurrence rate, and increasing financial burden have sparked innovation in the field. This mini-review provides a brief overview of currently used evacuation techniques, including emerging adjuncts such as endoscopic assistance and middle meningeal artery embolization. This review synthesizes the body of available evidence on efficacy and risk profiles for each critical aspect of surgical technique in cSDH evacuation and provides insight into trends in the field and promising new technologies.

Imaging of Abusive Head Trauma in Children

In this article, we describe relevant anatomy, mechanisms of injury, and imaging findings of abusive head trauma (AHT). We also briefly address certain mimics of AHT, controversies, pearls, and pitfalls. Concepts of injury, its evolution, and complex nature of certain cases are highlighted with the help of case vignettes.

Efficacy analysis of neuroendoscopy-assisted burr-hole evacuation for chronic subdural hematoma: a systematic review and meta-analysis

The purpose of this study was to compare neuroendoscopy-assisted burr-hole evacuation with conventional burr-hole evacuation in the treatment of chronic subdural hematoma (CSDH), and to evaluate the curative effect of neuroendoscopy. This study follows PRISMA guidelines and uses the keywords "chronic subdural hematoma," "neuroendoscopies," "neuroendoscopy," "endoscopy," "endoscopic neurosurgery," and "neuroendoscopic surgery" to conduct an electronic search of online databases, including PubMed, Embase, Web of Science, and Cochrane Library. There were no restrictions on language or publication year. This meta-analysis involved 948 patients in six studies. The results showed that the recurrence rate in the neuroendoscopy group was significantly lower than that in the conventional burr-hole group (3.1% vs. 13.8%, P<0.001). Compared with the control group, the neuroendoscopy group had a longer operation time (P<0.001) and a shorter postoperative drainage time (P<0.001). In addition, there was no significant difference in hospital stay (P=0.14), mortality (P=0.39), postoperative morbidity (P=0.12), or 6-month neurological outcomes (P=0.32) between the two groups. It should be noted that the comparison of neurological outcomes was based on 269 patients (6/106 vs. 14/163). Compared with conventional burr-hole evacuation, neuroendoscopy-assisted burr-hole evacuation reduces the recurrence rate of CSDH and shortens the postoperative drainage time. However, the neuroendoscopy group did not have lower mortality or morbidity or better functional outcomes. In the future, randomized controlled trials are needed to further evaluate the efficacy and safety of neuroendoscopic surgery.

Immunohistochemical visualization of lymphatic vessels in human dura mater: methodological perspectives

BACKGROUND

Despite greatly renewed interest concerning meningeal lymphatic function over recent years, the lymphatic structures of human dura mater have been less characterized. The available information derives exclusively from autopsy specimens. This study addressed methodological aspects of immunohistochemistry for visualization and characterization of lymphatic vessels in the dura of patients.

METHODS

Dura biopsies were obtained from the right frontal region of the patients with idiopathic normal pressure hydrocephalus (iNPH) who underwent shunt surgery as part of treatment. The dura specimens were prepared using three different methods: Paraformaldehyde (PFA) 4% (Method #1), paraformaldehyde (PFA) 0.5% (Method #2), and freeze-fixation (Method #3). They were further examined with immunohistochemistry using the lymphatic cell marker lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), and as validation marker we used podoplanin (PDPN).

RESULTS

The study included 30 iNPH patients who underwent shunt surgery. The dura specimens were obtained average 16.1 ± 4.5 mm lateral to the superior sagittal sinus in the right frontal region (about 12 cm posterior to glabella). While lymphatic structures were seen in 0/7 patients using Method #1, it was found in 4/6 subjects (67%) with Method #2, while in 16/17 subjects (94%) using Method #3. To this end, we characterized three types of meningeal lymphatic vessels: (1) Lymphatic vessels in intimate contact with blood vessels. (2) Lymphatic vessels without nearby blood vessels. (3) Clusters of LYVE-1-expressing cells interspersed with blood vessels. In general, highest density of lymphatic vessels were observed towards the arachnoid membrane rather than towards the skull.

CONCLUSIONS

The visualization of meningeal lymphatic vessels in humans seems to be highly sensitive to the tissue processing method. Our observations disclosed most abundant lymphatic vessels towards the arachnoid membrane, and were seen either in close association with blood vessels or remote from blood vessels.

Cortical atrophy in chronic subdural hematoma from ultra-structures to physical properties

Several theories have tried to elucidate the mechanisms behind the pathophysiology of chronic subdural hematoma (CSDH). However, this process is complex and remains mostly unknown. In this study we performed a retrospective randomised analysis comparing the cortical atrophy of 190 patients with unilateral CSDH, with 190 healthy controls. To evaluate the extent of cortical atrophy, CT scan images were utilised to develop an index that is the ratio of the maximum diameter sum of 3 cisterns divided by the maximum diameter of the skull at the temporal lobe level. Also, we reported, for the first time, the ultrastructural analyses of the CSDH using a combination of immunohistochemistry methods and transmission electron microscopy techniques. Internal validation was performed to confirm the assessment of the different degrees of cortical atrophy. Relative Cortical Atrophy Index (RCA index) refers to the sum of the maximum diameter of three cisterns (insular cistern, longitudinal cerebral fissure and cerebral sulci greatest) with the temporal bones' greatest internal distance. This index, strongly related to age in healthy controls, is positively correlated to the preoperative and post-operative maximum diameter of hematoma and the midline shift in CSDH patients. On the contrary, it negatively correlates to the Karnofsky Performance Status (KPS). The Area Under the Receiver Operating Characteristics (AUROC) showed that RCA index effectively differentiated cases from controls. Immunohistochemistry analysis showed that the newly formed CD-31 positive microvessels are higher in number than the CD34-positive microvessels in the CSDH inner membrane than in the outer membrane. Ultrastructural observations highlight the presence of a chronic inflammatory state mainly in the CSDH inner membrane. Integrating these results, we have obtained an etiopathogenetic model of CSDH. Cortical atrophy appears to be the triggering factor activating the cascade of transendothelial cellular filtration, inflammation, membrane formation and neovascularisation leading to the CSDH formation.

Factors Associated With Subdural Hygroma Following Mild Traumatic Brain Injury

Objective

Subdural hygroma (SDG) is a complication of traumatic brain injury (TBI). In particular, the outcome and outpatient treatment period may vary depending on the occurrence of SDG. However, the pathogenesis of SDG has not been fully elucidated. Therefore, this study aimed to identify the risk factors associated with the occurrence of SDG after mild TBI.

Methods

We retrospectively analyzed 250 patients with mild TBI admitted to a single institution between January 2021 and December 2021. The SDG occurrence and control groups were analyzed according to the risk factors of SDG, such as age, history, initial computed tomography (CT) findings, and initial laboratory findings.

Results

The overall occurrence rate of SDG was 31.6% (n=79). A statistically significant association was found between preoperative diagnoses and the occurrence of SDG, such as subarachnoid hemorrhage (odds ratio [OR], 2.36; 95% confidence interval [CI], 1.26–4.39) and basal skull fracture (OR, 0.32; 95% CI, 0.12–0.83). Additionally, age ≥70 years (OR, 3.20; 95% CI, 1.74–5.87) and the use of tranexamic acid (OR, 2.12; 95% CI, 1.05–4.54) were statistically significant factors. The prognostic evaluation of patients using the Glasgow Outcome Scale (GOS) did not show any statistical differences between patients with and without SDG.

Conclusion

SDG was not associated with the prognosis of patients assessed using the GOS. However, depending on the occurrence of SDG, differences in patient symptoms may occur after mild TBI. Therefore, the early evaluation of patients with mild TBI and determination of the probability of developing SDG are important.

Nomogram for predicting traumatic subdural effusion after mild traumatic brain injury

Objective

Traumatic subdural effusion (TSE) is a common complication of traumatic brain injury (TBI). This study aimed to determine the risk factors associated with subdural effusion and to propose a nomogram to predict the risk of TSE in patients with mild TBI.

Methods

We retrospectively analyzed 120 patients with mild TBI between January 2015 and December 2020 at the Third People's Hospital of Hefei. The risk factors of TSE were selected using univariate and multivariable logistic regression analysis. A nomogram was developed to predict the incidence of TSE. Receiver operating characteristics and calibration plots were used to evaluate the discrimination and fitting performance.

Results

Of the 120 patients, 32 developed subdural effusion after mild TBI. Univariate analysis showed that gender, age, history of hypertension, traumatic subarachnoid hemorrhage, subdural hematoma, basilar skull fracture, and cerebral contusion were varied significantly between groups (p &lt; 0.05). Logistic multivariate regression analysis showed that the gender, age, history of hypertension, and basilar skull fracture were independent risk factors for TSE. Based on these results, a nomogram model was developed. The C-index of the nomogram was 0.78 (95% CI: 0.70–0.87). The nomogram had an area under the receiver operating characteristic curve of 0.78 (95% CI: 0.70–0.87). The calibration plot demonstrated the goodness of fit between the nomogram predictions and actual observations.

Conclusion

Gender, age, history of hypertension, and basilar skull fracture can be used in a nomogram to predict subdural effusion after mild TBI.

Streptococcus pneumoniae Rapidly Translocate from the Nasopharynx through the Cribriform Plate to Invade the Outer Meninges

The entry routes and translocation mechanisms of microorganisms or particulate materials into the central nervous system remain obscure We report here that Streptococcus pneumoniae (pneumococcus), or polystyrene microspheres of similar size, appear in the meninges of the dorsal cortex of mice within minutes of inhaled delivery. Recovery of viable bacteria from dissected tissue and fluorescence microscopy show that up to at least 72 h, pneumococci and microspheres were predominantly found in the outer of the two meninges: the pachymeninx. No pneumococci were found in blood or cerebrospinal fluid. Intravital imaging through the skull, aligned with flow cytometry showed recruitment and activation of LysM+ cells in the dorsal pachymeninx at 5 and 10 hours following intranasal infection. Imaging of the cribriform plate suggested that both pneumococci and microspheres entered through the foramina via an inward flow of fluid connecting the nose to the pachymeninx. Our findings bring new insight into the varied mechanisms of pneumococcal invasion of the central nervous system, but they are also pertinent to the delivery of drugs to the brain and the entry of airborne particulate matter into the cranium. IMPORTANCE Using two-photon imaging, we show that pneumococci translocate from the nasopharynx to the dorsal meninges of a mouse in the absence of any bacteria found in blood or cerebrospinal fluid. Strikingly, this takes place within minutes of inhaled delivery of pneumococci, suggesting the existence of an inward flow of fluid connecting the nasopharynx to the meninges, rather than a receptor-mediated mechanism. We also show that this process is size dependent, as microspheres of the same size as pneumococci can translocate along the same pathway, while larger size microspheres cannot. Furthermore, we describe the host response to invasion of the outer meninges. Our study provides a completely new insight into the key initial events that occur during the translocation of pneumococci directly from the nasal cavity to the meninges, with relevance to the development of intranasal drug delivery systems and the investigations of brain damage caused by inhaled air pollutants.

H-ABC tubulinopathy revealed by label-free second harmonic generation microscopy

Hypomyelination with atrophy of the basal ganglia and cerebellum is a recently described tubulinopathy caused by a mutation in the tubulin beta 4a isoform, expressed in oligodendrocytes. The taiep rat is the only spontaneous tubulin beta 4a mutant available for the study of this pathology. We aimed to identify the effects of the tubulin mutation on freshly collected, unstained samples of the central white matter of taiep rats using second harmonic generation microscopy. Cytoskeletal differences between the central white matter of taiep rats and control animals were found. Nonlinear emissions from the processes and somata of oligodendrocytes in tubulin beta 4a mutant rats were consistently detected, in the shape of elongated structures and cell-like bodies, which were never detected in the controls. This signal represents the second harmonic trademark of the disease. The tissue was also fluorescently labeled and analyzed to corroborate the origin of the nonlinear signal. Besides enabling the description of structural and molecular aspects of H-ABC, our data open the door to the diagnostic use of nonlinear optics in the study of neurodegenerative diseases, with the additional advantage of a label-free approach that preserves tissue morphology and vitality.

Embolization of the Middle Meningeal Artery for the Treatment of Chronic Subdural Hematoma: A Path Less Travelled So Far

Introduction  Chronic subdural hematoma (CSDH) is relatively common and usually encountered in elderly population. With steady increase in life expectancy, incidence of CSDH also is bound to increase proportionately. Though surgery is the treatment of choice and relatively a simpler procedure, recurrence is a cause of concern. Embolization of the middle meningeal artery (MMA) is a newly evolving treatment modality in CSDH and offers hope in some of the recently published case series. Materials and Methods  Five cases of CSDH were subjected to embolization of MMA over a period from October 2019 to July 2020. Among them, it was employed for treatment in four cases after at least two recurrences following surgery, and in one case, it was done as the patient was not fit for surgery. All procedures were done under general anesthesia and polyvinyl alcohol (PVA) particles were used for embolization. Follow-up of the patients were done with computed tomography brain at 4 weeks and after 6 months of the procedure. Results  There was no incidence of recurrence in our series. Furthermore, embolization per se did not cause any complication or side effect which could be directly attributable to the procedure itself. Conclusion  In carefully selected patients based on clinical profile and angiographic findings, MMA embolization can be an effective modality for the treatment in CSDH.

Reducing meningo-cerebral adhesions by implanting an interpositional subdural polyesterurethane graft after high-grade glioma resection

BACKGROUND

Meningo-cerebral adhesions are frequently encountered during recurrent high-grade glioma resections. Adhesiolysis not only lengthens operation times, but can also induce focal cortical tissue injury that could affect overall survival.

METHODS

Immediately after the primary resection of a high-grade glioma, a polyesterurethane interpositional graft was implanted in the subdural space covering the entire exposed cortex as well as beneath the dural suture line. No postoperative complications were documented. All patients received adjuvant radiotherapy. Upon repeat resection for focal tumor recurrence, the graft was shown to effectively reduce meningo-cerebral adhesion development.

CONCLUSION

The implantation of a synthetic subdural graft is a safe and effective method for preventing meningo-cerebral adhesions.

Meningeal and visual pathway MRI analysis after single and repetitive Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA)-induced disruption in male and female mice

The consequences of forceful rotational acceleration on the central nervous system are not fully understood. While traumatic brain injury (TBI) research primarily has focused on effects related to the brain parenchyma, reports of traumatic meningeal enhancement in TBI patients may possess clinical significance. The objective of this study was to evaluate the meninges and brain for changes in dynamic contrast enhancement (DCE) magnetic resonance imaging (MRI) following closed-head impact model of engineered rotational acceleration (CHIMERA)–induced cerebral insult. Adult male and female mice received one (1 × ; n = 19 CHIMERA, n = 19 Sham) or four (4 × one/day; n = 18 CHIMERA, n = 12 Sham) injuries. Each animal underwent three MRI scans: 1 week before injury, immediately after the final injury, and 1 week post-injury. Compared with baseline readings and measures in sham animals, meningeal DCE in males was increased after single impact and repetitive injury. In female mice, DCE was elevated relative to their baseline level after a single impact. One week after CHIMERA, the meningeal enhancement returned to below baseline for single injured male mice, but compared with uninjured mice remained elevated in both sexes in the multiple impact groups. Pre-DCE meningeal T2-weighted relaxation time was increased only after 1 × CHIMERA in injured mice. Since vision is impaired after CHIMERA, visual pathway regions were analyzed through imaging and glial fibrillary acidic protein (GFAP) histology. Initial DCE in the lateral geniculate nucleus (LGN) and superior colliculus (SC) and T2 increases in the optic tract (OPT) and LGN were observed after injury with decreases in DCE and T2 1 week later. Astrogliosis was apparent in the OPT and SC with increased GFAP staining 7 days post-injury. To our knowledge, this is the first study to examine meningeal integrity after CHIMERA in both male and female rodents. DCE-MRI may serve as a useful approach for pre-clinical models of meningeal injury that will enable further evaluation of the underlying mechanisms.

Emerging roles for CNS fibroblasts in health, injury and disease

Recent transcriptomic, histological and functional studies have begun to shine light on the fibroblasts present in the meninges, choroid plexus and perivascular spaces of the brain and spinal cord. Although the origins and functions of CNS fibroblasts are still being described, it is clear that they represent a distinct cell population, or populations, that have likely been confused with other cell types on the basis of the expression of overlapping cellular markers. Recent work has revealed that fibroblasts play crucial roles in fibrotic scar formation in the CNS after injury and inflammation, which have also been attributed to other perivascular cell types such as pericytes and vascular smooth muscle cells. In this Review, we describe the current knowledge of the location and identity of CNS perivascular cell types, with a particular focus on CNS fibroblasts, including their origin, subtypes, roles in health and disease, and future areas for study.

Outpatient management of chronic expanding subdural hematomas with endovascular embolization to minimize inpatient admissions during the COVID-19 viral pandemic

Chronic subdural hematomas are complex collections that usually form after a trauma, particularly in elderly patients. This vulnerable population is at increased risk given the current viral pandemic. We share our experience in managing minimally symptomatic, enlarging subdural collections via middle meningeal embolization through the outpatient setting. This approach minimizes inpatient hospitalizations in hopes or reducing nosocomial spread (e.g., of COVID-19).

CGRP outflow into jugular blood and cerebrospinal fluid and permeance for CGRP of rat dura mater

Background

Calcitonin gene-related peptide (CGRP) is released from activated meningeal afferent fibres in the cranial dura mater, which likely accompanies severe headache attacks. Increased CGRP levels have been observed in different extracellular fluid compartments during primary headaches such as migraine but it is not entirely clear how CGRP is drained from the meninges.

Methods

We have used an in vivo preparation of the rat to examine after which time and at which concentration CGRP applied onto the exposed parietal dura mater appears in the jugular venous blood and the cerebrospinal fluid (CSF) collected from the cisterna magna. Recordings of meningeal (dural) and cortical (pial) blood flow were used to monitor the vasodilatory effect of CGRP. In a new ex vivo preparation we examined how much of a defined CGRP concentration applied to the arachnoidal side penetrates the dura. CGRP concentrations were determined with an approved enzyme immunoassay.

Results

CGRP levels in the jugular plasma in vivo were slightly elevated compared to baseline values 5-20 min after dural application of CGRP (10 μM), in the CSF a significant three-fold increase was seen after 35 min. Meningeal but not cortical blood flow showed significant increases. The spontaneous CGRP release from the dura mater ex vivo was above the applied low concentration of 1 pM. CGRP at 1 nM did only partly penetrate the dura.

Conclusions

We conclude that only a small fraction of CGRP applied onto the dura mater reaches the jugular blood and, in a delayed manner, also the CSF. The dura mater may constitute a barrier for CGRP and limits diffusion into the CSF of the subarachnoidal space, where the CGRP concentration is too low to cause vasodilatation.

Preserved arachnoid membrane acts as a predictor of postoperative visual improvement in clinoidal meningioma

OBJECTIVES

Improvement of patient visual outcome is very important in the treatment of clinoidal meningioma (CLM). The purpose of this study is to determine the association between arachnoid preservation and visual outcome.

PATIENTS

Fifteen patients with CLMs that caused visual impairment underwent surgery in our hospital. The patients included 4 men and 11 women, and the mean age was 53.3 years.

METHODS

The clinical findings of these patients were retrospectively reviewed. We divided the patients into two groups based on the presence or absence of the arachnoid membrane. Group 1 comprised cases in which arachnoid preservation was intraoperatively confirmed. Group 2 comprised cases in which the arachnoid membrane was not preserved. The Landolt C chart was used to evaluate visual acuity, and dynamic visual field tests using Goldmann perimetry were used to evaluate the visual field. Results were compared before and after surgery.

RESULTS

The visual acuity of the ipsilateral eye was significantly improved in Group 1 (p = 0.038). There were no other significant differences between the two groups in terms of tumor volume, patient age, and symptom duration.

CONCLUSIONS

Patients in which arachnoid preservation could be intraoperatively confirmed had good improvement in visual acuity. Further research with an increased number of cases is needed to confirm these findings.

A novel rat model of chronic subdural hematoma: Induction of inflammation and angiogenesis in the subdural space mimicking human-like features of progressively expanding hematoma

Pathophysiological mechanisms of chronic subdural hematoma (CSDH) involve localized inflammation, angiogenesis, and dysregulated coagulation and fibrinolysis. The scarcity of reproducible and clinically relevant animal models of CSDH hinders further understanding the underlying pathophysiology and improving new treatment strategies. Here, we developed a novel rat model of CSDH using extracellular matrices (Matrigel) and brain microvascular endothelial cell line (bEnd.3 cells). One hundred-microliter of Matrigel-bEnd.3 cell (10⁶ cells per milliliter) mixtures were injected into the virtual subdural space of elderly male Sprague-Dawley rats. This approach for the first time led to a spontaneous and expanding subdural hematoma, encapsulated by internal and external neomembranes, formed as early as 3 d, reached its peak at 7 d, and lasted for more than 14 d, mimicking the progressive hemorrhage observed in patients with CSDH. The external neomembrane and hematoma fluid involved numerous inflammatory cells, fibroblasts, and highly fragile neovessels. Furthermore, a localized pathophysiological process was validated as evidenced by the increased expressions of inflammatory and angiogenic mediators in external neomembrane and hematoma fluid rather than in peripheral blood. Notably, the specific expression profiles of these mediators were closely associated with the dynamic changes in hematoma volume and neurological outcome. In summary, the CSDH model described here replicated the characteristics of human CSDH, and might serve as an ideal translational platform for preclinical studies. Meanwhile, the crucial roles of angiogenesis and inflammation in CSDH formation were reaffirmed.

Aging-associated inflammation and fibrosis in arachnoid membrane

Background

The physiological and pathological significance of the arachnoid membrane (AM) is still unknown. In this study, we investigated various characteristics of the AM, focusing on the influence of inflammation and fibrosis.

Methods

Small pieces of AM sample were obtained during neurosurgical procedures from 74 cases. The clinical and pathological characteristics of the hyperplastic AM group (≥ 50 μm) and the non-hyperplastic AM group (< 50 μm) were compared. Then, potential correlations between AM thickness and clinical characteristics were analyzed. Moreover, VEGFα, TGFβ, and TGFα levels were quantitated by real time PCR. Then, the potential correlations between AM thickness and these inflammatory or anti-inflammatory markers, and the influence of the original disease were calculated.

Results

The median age of the patients in hyperplastic AM group was significantly older than that of the non-hyperplastic AM group. Moreover, the number of fibroblasts, CD68⁺ cells, CD86⁺ cells, and CD206⁺ cells in the hyperplastic AM group was significantly higher than that in the non-hyperplastic AM group. The AM thickness was significantly correlated to age and number of fibroblasts, CD68⁺ cells, CD86⁺ cells, and CD206⁺ cells. The thickness of the AM was significantly correlated to the messenger RNA expression levels of VEGFα (ρ = 0.337), and the VEGFα expression levels were significantly correlated with TGFβ and TNFα.

Conclusions

The AM hyperplasia was influenced by aging and could be a result of inflammation and fibrosis through cytokine secretion from the inflammatory cells and fibroblasts in the AM.

Predictors of Brain Natriuretic Peptide Serum Level Elevation in Patients with Symptomatic Chronic Subdural Hematoma: A Prospective Study

Background: Brain natriuretic peptide serum levels (BNP) on admission are frequently elevated in patients with symptomatic chronic subdural hematoma (cSDH) and predict unfavorable long-term functional outcomes. However, the reasons for these elevated levels remain unclear. Therefore, we aimed to identify the predictors of BNP elevation. Methods: Patients with unilateral symptomatic cSDH who were surgically treated in our department between November 2016 and May 2020 were enrolled. Patients’ symptoms and neurological deficits were prospectively assessed using a study questionnaire. On initial computer tomography, hematoma volumes and midline shift (MLS) values were measured to analyze the degree of brain compression. Results: In total, 100 patients were analyzed. Linear regression analysis showed that higher BNP levels were significantly associated with smaller hematoma volumes (p = 0.003) and littler MLS values (p = 0.022). Multivariate analysis revealed that presence of a neurological deficit (p = 0.041), a hematoma volume < 140 mL (p = 0.047), advanced age (p = 0.023), and head trauma within 24 h of admission (p = 0.001) were independent predictors of BNP elevation. Conclusion: In symptomatic cSDH, BNP elevation is related, among others, to the presence of neurological deficits and smaller hematoma volumes. Whether BNP elevation may coincide with the early stage of hematoma growth, i.e., immaturity of cSDH neomembrane, requires further investigations.

Arachnoid and dural reflections

The dura mater is the major gateway for accessing most extra-axial lesions and all intra-axial lesions of the central nervous system. It provides a protective barrier against external trauma, infections, and the spread of malignant cells. Knowledge of the anatomical details of dural reflections around various corners of the skull bases provides the neurosurgeon with confidence during transdural approaches. Such knowledge is indispensable for protection of neurovascular structures in the vicinity of these dural reflections. The same concept is applicable to arachnoid folds and reflections during intradural excursions to expose intra- and extra-axial lesions of the brain. Without a detailed understanding of arachnoid membranes and cisterns, the neurosurgeon cannot confidently navigate the deep corridors of the skull base while safely protecting neurovascular structures. This chapter covers the surgical anatomy of dural and arachnoid reflections applicable to microneurosurgical approaches to various regions of the skull base.

Dural venous system: angiographic technique and correlation with ex vivo investigations

BACKGROUND

The dural vasculature plays a key role in several important conditions, including dural fistulas and subdural collections. While in vivo investigations of intrinsic dural arterial angioarchitecture are rare, no angiographic studies of dural venous drainage exist to our knowledge.

OBJECTIVE

To describe methods by which dural venous drainage might be visualized with current angiographic equipment and technique, and to correlate our results with existing ex vivo literature.

METHODS

Digital subtraction angiography and 3D angiography (rotational and Dyna CT) of dural neurovasculature were acquired in the context of subdural hematoma embolization and normal dura. Protocols for visualization of dural venous drainage were established, and findings correlated with ex vivo studies.

RESULTS

Meningeal arteries supply both the skull and dura. Normal dural enhancement is accentuated by the presence of hypervascular membranes. Intrinsic meningeal veins/sinuses parallel outer layer arteries with well-known tram-tracking appearance. Dura adjacent to main arterial trunks drains via skull base foramina into the pterygopalatine venous plexus, or via emissary veins into the temporalis venous plexus. Dura near the sinuses drains into venous pouches adjacent to the sinus, before emptying into the sinus proper-possibly the same pouches implicated in the angioarchitecture of dural fistulas. Finally, posterior temporoparietal convexity dura, situated in a watershed-like region between middle and posterior meningeal territories, frequently empties into diploic and emissary veins of the skull. Wide variation in balance is expected between these three routes. Drainage patterns appear to correlate with venous embryologic investigations of Padget and ex vivo studies in adults.

CONCLUSIONS

Continued attention to dural venous drainage may prove useful in the diagnosis and management of dural-based vascular diseases.

Spinal subdural hematoma after interlaminar full-endoscopic decompression of lumbar spinal stenosis: a case report and literature review

The use of full-endoscopic decompression for lumbar spinal stenosis has been increasing recently. It is a minimally invasive surgical procedure that has few complications. Spinal subdural hematoma (SSH) following endoscopic surgery has never been reported. Previously described SSHs have occurred spontaneously or due to surgery-related iatrogenic injury. We describe the first case of SSH after endoscopic decompression. A 68-year-old woman presented with bilateral radiating pain and neurological claudication due to lumbar spinal stenosis at the L4-5 level. Full-endoscopic interlaminar decompression was performed without intraoperative complications. Preoperative leg pain improved after endoscopic decompression. However, two days after the index surgery, the patient complained of severe radiating pain in her right leg with urinary retention. The radiologic evaluation showed compressive subdural fluid collection at the index level. Open microscopic decompression was performed. No dural injury was observed. After durotomy, xanthochromic fluid gushed out at a high pressure. We found that the arachnoid was also intact. The patient recovered completely after surgical hematoma evacuation. Although SSH after endoscopic decompression is a very rare event, it is a reminder that suspicion and urgent imaging and intervention are necessary during the postoperative period upon development of unexpected, progressive neurological deterioration regardless of intraoperative problems. Additionally, early surgical decompression is necessary for optimal neurological recovery.

Neuroanatomy of cranial dural vessels: implications for subdural hematoma embolization

Adoption of middle meningeal artery embolization in the management of chronic subdural hematomas has led to a renewed interest in dural vascular anatomy. The readily identifiable major dural arteries and potential hazards associated with their embolization are well described. Less emphasized are several levels of intrinsic dural angioarchitecture, despite their more direct relationship to dural based diseases, such as subdural hematoma and dural fistula. Fortunately, microvascular aspects of dural anatomy, previously limited to ex vivo investigations, are becoming increasingly accessible to in vivo visualization, setting the stage for synthesis of the old and the new, and providing a rationale for the endovascular approach to subdural collections in particular. In contrast with traditional anatomical didactics, where descriptions advance from larger trunks to smaller pedicles, we present a strategic approach that proceeds from a fundamental understanding of the dural microvasculature and its relationship to larger vessels.

A venous mechanism of ventriculomegaly shared between traumatic brain injury and normal ageing

Recently, age-related timing dissociation between the superficial and deep venous systems has been observed; this was particularly pronounced in patients with normal pressure hydrocephalus, suggesting a common mechanism of ventriculomegaly. Establishing the relationship between venous drainage and ventricular enlargement would be clinically relevant and could provide insight into the mechanisms underlying brain ageing. To investigate a possible link between venous drainage and ventriculomegaly in both normal ageing and pathological conditions, we compared 225 healthy subjects (137 males and 88 females) and 71 traumatic brain injury patients of varying ages (53 males and 18 females) using MRI-based volumetry and a novel perfusion-timing analysis. Volumetry, focusing on the CSF space, revealed that the sulcal space and ventricular size presented different lifespan profiles with age; the latter presented a quadratic, rather than linear, pattern of increase. The venous timing shift slightly preceded this change, supporting a role for venous drainage in ventriculomegaly. In traumatic brain injury, a small but significant disease effect, similar to idiopathic normal pressure hydrocephalus, was found in venous timing, but it tended to decrease with age at injury, suggesting an overlapping mechanism with normal ageing. Structural bias due to, or a direct causative role of ventriculomegaly was unlikely to play a dominant role, because of the low correlation between venous timing and ventricular size after adjustment for age in both patients and controls. Since post-traumatic hydrocephalus can be asymptomatic and occasionally overlooked, the observation suggested a link between venous drainage and CSF accumulation. Thus, hydrocephalus, involving venous insufficiency, may be a part of normal ageing, can be detected non-invasively, and is potentially treatable. Further investigation into the clinical application of this new marker of venous function is therefore warranted.

Endovascular embolisation of the middle meningeal artery to treat chronic subdural haematomas: effectiveness, safety, and the current controversy. A systematic review

INTRODUCTION

Chronic subdural haematoma (CSDH) represents a clinical challenge due to its high recurrence rate. Endovascular middle meningeal artery embolisation (eMMAE) has emerged as an alternative for those patients presenting health problems or multiple recurrences of CSDH. Despite several encouraging reports, the safety profile, indications, and limitations of the technique are not clearly established.

DEVELOPMENT

This study aimed to evaluate the current evidence on eMMAE in patients with CSDH. We performed a systematic review of the literature, following the PRISMA guidelines. Our search yielded a total of 6 studies, in which a total of 164 patients with CSDH underwent eMMAE. The recurrence rate across all studies was 6.7%, and complications occurred in up to 6% of patients.

CONCLUSIONS

eMMAE is a feasible technique for treating CSDH, with a relatively low recurrence rate and an acceptable rate of complications. Further prospective and randomised studies are needed to formally establish a clear profile of the safety and effectiveness of the technique.

Effectiveness and Safety of Pressure Dressings on Reducing Subdural Effusion After Decompressive Craniectomy

OBJECTIVE

Decompressive craniectomy as a treatment is often used in the rescue treatment of critically ill patients in neurosurgery; however, there are many complications after this operation. Subdural effusion is a common complication after decompressive craniectomy. Once it occurs, it can cause further problems for the patient. Therefore, the purpose of this study was to explore the safety and effectiveness of pressure dressings for subdural effusion after decompressive craniectomy.

METHODS

Patients who underwent decompressive craniectomy in our hospital from January 2016 to January 2021 were included in this study, and all patients were followed up for 6 months or more. After the operation, the patients were divided into two groups according to whether they received a pressure dressing or a traditional dressing. Subdural effusion, cerebrospinal fluid leakage, hydrocephalus and other complications were compared between the two groups, and the differences in hospital duration, cost and prognosis between the two groups were analyzed.

RESULTS

A total of 123 patients were included in this study. Among them, 62 patients chose pressure dressings, and 61 patients chose traditional dressings. The incidence of subdural effusion in the pressure dressing group was significantly lower than that in the traditional dressing group (P<0.05). There was no difference between the two groups in cerebrospinal fluid leakage and hydrocephalus (P > 0.05). In addition, the length of hospital stay and the total cost in the pressure dressing group were significantly lower (P<0.05).

CONCLUSION

Pressure dressing can effectively reduce the occurrence of subdural effusion after decompressive craniectomy, and it does not increase the occurrence of other cerebrospinal fluid-related complications.

Meningiomas from a developmental perspective: exploring the crossroads between meningeal embryology and tumorigenesis

Meningiomas are tumors arising from the meninges and represent the most frequent central nervous system tumors in adults. Recent large-scale genetic studies and preclinical meningioma mouse modelling led to a better comprehension of meningioma development and suggested evidences of close relationships between meningeal embryology and tumorigenesis. In this non-systematic review, we summarize the current knowledge on meningeal embryology and developmental biology, and illustrate how meningioma tumorigenesis is deeply related to meningeal embryology, concerning the potential cell of origin, the role of reactivation of embryonic stem cells, the influence of the embryonic tissue of origin, and the parallelism between topography-dependant molecular pathways involved in normal meninges and in meningioma development. Our study emphasizes why future studies on meningeal embryology are mandatory to affine our comprehension of mechanisms underlying meningioma initiation and development.

Quiescent and Activated Fibroblasts in Lateral Ventricular Meningioma With a Dura-like Membrane

BACKGROUND

Lateral ventricular meningioma (LVM) is a rare entity, accounting for 0.5%-5% of all intracranial meningiomas. This type of meningioma arises from meningothelial inclusion bodies in the tela choroidea and/or mesenchymal stroma of the choroid plexus. Although not yet fully characterized, a membranous structure is frequently observed around LVMs. This study analyzed quiescent and activated fibroblast phenotypes in LVMs with focus on the relationship between tumor growth and development of the membranous structure.

METHODS

This retrospective study analyzed 9 LVM cases for which gross total removal was achieved. Expression of the ependymal cell marker (Forkhead Box J1 [FoxJ1]) was histopathologically evaluated. The distribution of quiescent and activated fibroblasts was also analyzed using anti-fibroblast-specific protein-1 (FSP1)/S100A4 antibody and anti-α-smooth muscle actin (αSMA) antibody, respectively. The control group was 5 cases with primary convexity meningioma for which Simpson grade I removal was achieved.

RESULTS

Small LVMs (≤30 mm) were covered by a FoxJ1-positive(+) ependymal cell monolayer; no αSMA(+) cells were detected in the tumor; and a thick membrane capsule was not observed. None of the convexity meningiomas showed FoxJ1(+) cells. Large LVMs (>30 mm) had thick membrane capsules without an ependymal cell monolayer, which resembled dura mater. The FSP1/S100A4(+) and αSM(+) cells were clearly concentrated in the peripheral area just below the thick dura mater-like membrane capsules.

CONCLUSIONS

This study found an association between activated fibroblasts and dura mater-like membrane capsules in LVMs. The characteristics of membranous structure in LVMs may differ depending on tumor size.

A computational investigation of strain concentration in the brain in response to a rapid temperature rise

Following the mysterious health attacks on U.S. diplomats in Cuba in 2016, the cause of concussion-like symptoms concurrent with strange noises heard by the diplomats remains undetermined. A wide range of possible causes of the sensations have been proposed: pulsed microwave exposure, infrasound acoustic devices, pesticides/neurotoxins, and even mass hysteria (psychogenic illness). Here, we numerically examine the pulsed microwave exposure hypothesis and the simulated mechanical response of brain tissue. A computational model is used to examine the influence of various spatially varying temperature gradients and pulse durations on the mechanical response of brain tissue. We show that a stress-focusing effect due to a rapid temperature increase may result in brain tissue strains larger than the initially applied thermal strains.

Hyper-viscoelastic mechanical behavior of cranial pia mater in tension

BACKGROUND

Cranial pia mater, the innermost layer of the meninges, protects the central nervous system by tightly wrapping the brain and damping the external impact force to the brain. Accurate experimental data of the mechanical property of the cranial pia mater can enhance the theoretical prediction of traumatic brain injury or the scientific surgery design for brain disease. The aim of this study is to characterize the mechanical behavior of the cranial pia mater.

METHODS

In vitro tensile and stress-relaxation experiments of ovine cranial pia mater specimens were conducted at eight strain rates to characterize the rate-dependent viscoelastic property. The tensile and stress-relaxation experimental data were fitted by an Ogden hyper-viscoelastic model with a strain rate function to describe the mechanical behavior of the cranial pia mater.

FINDINGS

The elastic modulus and the ultimate stress are significantly increased from 5.545 MPa and 0.535 MPa at 0.00167 s^-1 to 18.345 MPa and 2.547 MPa at 0.83 s^-1 (p < .0001), respectively. The initial stress and the long-term stress (300 s) are also increased significantly with the increasing strain rates (p < .0001). A good fit of the experimental data with the Ogden hyper-viscoelastic model incorporated with a strain rate function was achieved (R² > 0.93).

INTERPRETATION

The cranial pia mater exhibits as a rate-dependent hyper-viscoelastic material in the tensile and stress-relaxation experiments. Compared with the brain, the stiffer nature of the cranial pia mater indicates its essential role in brain protection. The rate-dependent constitutive model provides a proper description of the hyper-viscoelastic characteristics of the cranial pia mater in tension and may provide a basic constitutive relationship for numerical simulations of traumatic brain injury.