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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.

Abstract Background Intracystic hematoma in arachnoid cyst are a very rare pathology that commonly occurs after head trauma, while spontaneous intracystic hematomas in arachnoid cyst associated with subdural hematoma is extremely rare. Currently there are 33 patients of spontaneous intracystic hematomas in arachnoid cyst reported in the literature. In this case report we present an adult patient with concomitant chronic subdural hematoma with intracystic hematoma in arachnoid cyst. Case presentation A 19-year-old Egyptian Arabian female patient presented to the outpatient clinic complaining of severe headache of 1-month duration that was progressive in nature. Provisionally, it was thought that it might be an arachnoid cyst with associated chronic subdural hematoma along with intracystic hematoma. Decision to proceed with craniotomy and cyst evacuation was made. Conclusion Concomitant intracystic hematoma in arachnoid cyst along with subdural hematoma is a serious condition that might be life-threatening if not well managed.

Meninges cover the surface of the brain and spinal cord and contribute to protection and immune surveillance of the central nervous system (CNS). How the meningeal layers establish CNS compartments with different accessibility to immune cells and immune mediators is, however, not well understood. Here, using 2-photon imaging in female transgenic reporter mice, we describe VE-cadherin at intercellular junctions of arachnoid and pia mater cells that form the leptomeninges and border the subarachnoid space (SAS) filled with cerebrospinal fluid (CSF). VE-cadherin expression also marked a layer of Prox1+ cells located within the arachnoid beneath and separate from E-cadherin+ arachnoid barrier cells. In vivo imaging of the spinal cord and brain in female VE-cadherin-GFP reporter mice allowed for direct observation of accessibility of CSF derived tracers and T cells into the SAS bordered by the arachnoid and pia mater during health and neuroinflammation, and detection of volume changes of the SAS during CNS pathology. Together, the findings identified VE-cadherin as an informative landmark for in vivo imaging of the leptomeninges that can be used to visualize the borders of the SAS and thus potential barrier properties of the leptomeninges in controlling access of immune mediators and immune cells into the CNS during health and neuroinflammation.

Cerebral venous thrombosis is the obstruction of cranial venous pathways, including thrombosis in the cortical, dural, and deep cerebral veins. It constitutes 0.5%-1% of all strokes and is usually seen in young people. It is slightly more common in young women due to pregnancy, puerperium, and oral contraceptive use. Patients usually present with headaches or focal neurological deficits. Intradural venous sinus cysts are congenital and very rare pathologies. They are usually asymptomatic and detected incidentally. However, large cysts may be symptomatic when they disrupt the venous flow. Common symptoms are headaches and syncope. In this case, we present our 41-year-old female patient with complaints of headache, syncope, dizziness, ringing in the ears, and sleep disturbances that have been going on for 1 month. The patient's complete blood count revealed a normal hematocrit, hemoglobin, and red blood cell count. After clinical and laboratory exclusion of other differential diagnoses in the case, a magnetic resonance imaging (MRI) venography examination was requested with the preliminary diagnosis of dural sinus vein thrombosis. In the magnetic resonance venography examination performed in our case, an unenhanced 7 mm-diameter area was observed in the contrast-enhanced series. The diagnosis was primarily considered as cerebral venous sinus thrombosis. Our patient's complaints of severe headache, dizziness, and syncope were also consistent with our initial diagnosis. However, our patient did not benefit from the anticoagulant treatment given. For this reason, we turned to alternative diagnoses and performed a contrast-enhanced MRI. Our diagnosis changed to intradural venous sinus cyst after constrast-enhanced MRI examination. [ABSTRACT FROM AUTHOR]

PurposeBrain herniation into arachnoid granulations (BHAG) of the dural venous sinuses is a recently described finding of uncertain etiology. The purpose of this study was to investigate the prevalence of BHAG in a cohort of patients with pulsatile tinnitus (PT) and to clarify the physiologic and clinical implications of these lesions.MethodsThe imaging and charts of consecutive PT patients were retrospectively reviewed. All patients were examined with MRI including pre- and post-contrast T1- and T2-weighted sequences. Images were reviewed separately by three blinded neuroradiologists to identify the presence of BHAG. Their location, signal intensity, size, presence of arachnoid granulation, and associated dural venous sinus stenosis were documented. Clinical records were further reviewed for idiopathic intracranial hypertension, history of prior lumbar puncture, and opening pressure.ResultsTwo hundred sixty-two consecutive PT patients over a 4-year period met inclusion criteria. PT patients with BHAG were significantly more likely to have idiopathic intracranial hypertension than PT patients without BHAG (OR 4.2, CI 1.5-12, p = 0.006). Sixteen out of 262 (6%) patients were found to have 18 BHAG. Eleven out of 16 (69%) patients had unilateral temporal or occipital lobe herniations located in the transverse sinus or the transverse-sigmoid junction. Three out of 16 (19%) patients had unilateral cerebellar herniations and 2/16 (13%) patients had bilateral BHAG.ConclusionIn patients with PT, BHAG is a prevalent MRI finding that is strongly associated with the clinical diagnosis of IIH. The pathogenesis of BHAG remains uncertain, but recognition should prompt comprehensive evaluation for IIH.

Introduction: The pia-arachnoid is a critical component of cerebrospinal fluid removal. It covers and invaginates into the brain parenchyma, and physiologic failure results in hydrocephalus and cerebral edema. The purpose of this study was to characterize the role of arachnoid within brain parenchyma and determine if water flux and solute transport are affected by these intra-parenchymal cells. Methods: An immortalized arachnoid rat cell line was used to seed 300-µm organotypic rat brain slices of 4-week-old rats. Fluid and tracer transport analyses were conducted following a 7-10 day intraparenchymal growth period. The development of an arachnoid brain slice model was characterized using diffusion chamber experiments to calculate permeability, diffusion coefficient, and flux. Results: Labeled rat arachnoid cells readily penetrated organotypic cultures for up to 10 days. A significant reduction of dye and water flux across arachnoid-impregnated brain slices was observed after 3 hours in the diffusion chamber. Permeability decreased in whole brain slices containing arachnoid cells compared to slices without arachnoid cells. In comparison, a significant reduction of dextran across all slices occurred when molecular weights increased from 40 to 70 kDa. Conclusion: Tracer and small molecule studies show that arachnoid cells' presence significantly impacts water's movement through brain parenchyma. Size differential experiments indicate that the permeability of solute changed substantially between 40 and 70 kDa, an essential marker of blood-CSF barrier definition. We have developed an arachnoid organotypic model that reveals their ability to alter permeability and transport. [ABSTRACT FROM AUTHOR]

Abstract Background Arachnoid cysts (ACs) account for about 1% of all intracranial mass lesions. The Sylvian fissure is the most common site of ACs which are usually asymptomatic. Traumatic rupture of arachnoid cysts complicated with subdural hygroma is a relatively rare entity in adults especially in females. There is no consensus on their management and each case could add to previous experiences leading to more uniform therapeutic measurements. This case encompasses a combination of watchful strategy, limited surgery and ultimately successful cyst fenestration which highlights a good outcome without complications by adopting a stepwise procedure. Case presentation Here, the case of a 51-year-old Persian woman being presented with a 2-month history of a localized headache which had begun 4 days after a minor head trauma. Early brain computed tomography (CT) obtained in another center at 4th day of post-injury which misinterpreted as an old infarct. Repeated CT in our center revealed a large AC of Sylvian fissure complicated with subdural hygroma. Initially a conservative management pursued but due to worsening of the symptoms, a burr-hole craniotomy performed for hygroma evacuation that subsequently followed by cyst fenestration about 1-month later. Conclusion Previous awareness about radiographic characteristics of ACs as well as employing appropriate imaging modality are necessary for correct and timely diagnosis of symptomatic patients after minor head trauma because incidentally found ACs might be the underpinning causes of symptoms. Also, following a multistage therapeutic process along with the involvement of patients in decision-making are of paramount importance.

Background: Arachnoid cysts (ACs) account for about 1% of all intracranial mass lesions. The Sylvian fissure is the most common site of ACs which are usually asymptomatic. Traumatic rupture of arachnoid cysts complicated with subdural hygroma is a relatively rare entity in adults especially in females. There is no consensus on their management and each case could add to previous experiences leading to more uniform therapeutic measurements. This case encompasses a combination of watchful strategy, limited surgery and ultimately successful cyst fenestration which highlights a good outcome without complications by adopting a stepwise procedure. Case presentation: Here, the case of a 51-year-old Persian woman being presented with a 2-month history of a localized headache which had begun 4 days after a minor head trauma. Early brain computed tomography (CT) obtained in another center at 4th day of post-injury which misinterpreted as an old infarct. Repeated CT in our center revealed a large AC of Sylvian fissure complicated with subdural hygroma. Initially a conservative management pursued but due to worsening of the symptoms, a burr-hole craniotomy performed for hygroma evacuation that subsequently followed by cyst fenestration about 1-month later. Conclusion: Previous awareness about radiographic characteristics of ACs as well as employing appropriate imaging modality are necessary for correct and timely diagnosis of symptomatic patients after minor head trauma because incidentally found ACs might be the underpinning causes of symptoms. Also, following a multistage therapeutic process along with the involvement of patients in decision-making are of paramount importance. [ABSTRACT FROM AUTHOR]

Spinal extradural arachnoid cysts are rare benign lesions occurring along the cerebrospinal axis. They may be associated with pain or varying degrees of neurological compressive symptoms. Brown-Sequard syndrome is a rare sequalae, where there is ipsilateral upper motor neuron paralysis with loss of proprioception as well as contralateral loss of pain and temperature sensation below the lesion. We present a 33-year-old female with a 6-month history of worsening right lower limb weakness and a 2-month history of right lower limb pain. Motor examination revealed right lower limb weakness as well as exaggerated knee and ankle jerk reflexes. A magnetic resonance imaging (MRI) was done, which showed an eccentrically located T4–7 cystic extradural mass causing severe cord compression. She had T4–7 laminectomies with total excision of the cyst and disconnection of the fistulous tract between the cyst and the subarachnoid space. She made full neurologic recovery with no complications. [ABSTRACT FROM AUTHOR]

Background: The meninges, formed by dura, arachnoid and pia mater, cover the central nervous system and provide important barrier functions. Located between arachnoid and pia mater, the cerebrospinal fluid (CSF)-filled subarachnoid space (SAS) features a variety of trabeculae, septae and pillars. Like the arachnoid and the pia mater, these structures are covered with leptomeningeal or meningothelial cells (MECs) that form a barrier between CSF and the parenchyma of the optic nerve (ON). MECs contribute to the CSF proteome through extensive protein secretion. In vitro, they were shown to phagocytose potentially toxic proteins, such as α-synuclein and amyloid beta, as well as apoptotic cell bodies. They therefore may contribute to CSF homeostasis in the SAS as a functional exchange surface. Determining the total area of the SAS covered by these cells that are in direct contact with CSF is thus important for estimating their potential contribution to CSF homeostasis. Methods: Using synchrotron radiation-based micro-computed tomography (SRµCT), two 0.75 mm-thick sections of a human optic nerve were acquired at a resolution of 0.325 µm/pixel, producing images of multiple terabytes capturing the geometrical details of the CSF space. Special-purpose supercomputing techniques were employed to obtain a pixel-accurate morphometric description of the trabeculae and estimate internal volume and surface area of the ON SAS. Results: In the bulbar segment, the ON SAS microstructure is shown to amplify the MECs surface area up to 4.85-fold compared to an "empty" ON SAS, while just occupying 35% of the volume. In the intraorbital segment, the microstructure occupies 35% of the volume and amplifies the ON SAS area 3.24-fold. Conclusions: We provided for the first time an estimation of the interface area between CSF and MECs. This area is of importance for estimating a potential contribution of MECs on CSF homeostasis. [ABSTRACT FROM AUTHOR]

Objective: Pituitary adenomas frequently extend into the suprasellar space. After a suprasellar tumor is removed, the superiorly extended arachnoid becomes redundant and sinks down into the intrasellar space which often hiders visualization and accessibility to the hidden space behind the evaginated arachnoid. We introduced arachnoid remodeling by clipping technique, and evaluated its usefulness and safety during TSS. Methods: Total 223 patients who underwent arachnoid remodeling with our new clipping technique were included. Redundant arachnoid was clipped along the dural edge with multiple 2.6-mm titanium clips until the redundant arachnoid membrane no longer blocked the surgical route. To check for possible deterioration of hormonal function by this technique, we assessed anterior pituitary function of 166 patients who underwent arachnoid remodeling by clipping and compared this with those of other 429 control patients. Results: Our technique greatly enhanced the accessibility and visualization of intrasellar and parasellar spaces, both of which are generally hindered by redundant arachnoid during transsphenoidal surgery (TSS). We found no difference in anterior pituitary function between a clip-assisted arachnoid remodeling group and the control group, implying that this technique does not result in hypopituitarism. Conclusion: During TSS for pituitary adenomas with suprasellar extension, arachnoid remodeling by clipping technique is very useful and convenient for the management of the redundant arachnoid membrane to enhance visualization and surgical accessibility. [ABSTRACT FROM AUTHOR]

Sphenoid wing meningiomas are slow-growing tumors that originate from outer arachnoid meningeal epithelial cells. They can present with progressive symptoms of an orbital or temporal fossa mass, including temporal fullness, proptosis, globe displacement, ptosis, and impaired ocular motility. The ophthalmic manifestations of sphenoid wing meningiomas vary depending on the location of the primary tumor. In this case report, we discuss a 52-year-old female with meningioma of unusual presentation which was reported to be removed completely, and recurrence was noticed after a lapse of 3 years with subsequent extension into the orbit resulting in the structural and functional destruction of the eye.

The presence of intact arachnoid membranes between skull base meningiomas and critical neurovascular structures is crucial for predicting surgical outcomes, understanding tumor development and growth, and planning the feasibility of tumor resection or the need for adjuvant treatments. While neurosurgeons often utilize the subarachnoid cisterns to enhance access to these tumors and facilitate their removal, a comprehensive review aimed at health professionals involved in the diagnosis and treatment of this complex pathology, including radiologists, neurologists, oncologists, ophthalmologists, and neurosurgeons is still lacking. This study aims to summarize the interaction between skull base meningiomas, subarachnoid cisterns, and arachnoid membranes, emphasizing their significance in both the diagnosis and treatment of this pathology. By conducting a thorough radiological assessment of skull base meningiomas, correlating these findings with intraoperative observations, and reviewing relevant literature, we summarize the critical relationship between skull base meningiomas and the surrounding subarachnoid spaces. We concisely describe how arachnoid structures influence tumor growth and interaction with neurovascular elements. We advocate for the inclusion of tumor-arachnoid relationships in the medical literature concerning the treatment of these tumors. A better understanding and description of the interaction between tumors and neurovascular structures will aid in planning and attempting safer treatments, minimizing surgical risks, predicting potential tumor progression, and the need for adjuvant treatments., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s).)

Objective: To explore the clinical efficacy and safety of microvascular decompression (MVD) combined with internal neurolysis (IN) in the treatment of recurrent trigeminal neuralgia (TN) after MVD. Methods: Sixty-four patients with recurrent TN admitted to the hospital from January 2014 to December 2017 were divided into two groups according to the surgical method. Twenty-nine patients, admitted from January 2014 to December 2015, were treated with MVD alone, whereas 35 admitted from January 2016 to December 2017 were treated with MVD+IN. The postoperative efficacy, complications, and pain recurrence rate of the two groups were analyzed. Results: The efficacy of the MVD+IN and MVD groups were 88.6% and 86.2%, and the cure rates were 77.1% and 65.5% respectively. There was no statistically significant difference between the two groups (p>0.05). The cure rate (83.3%) of patients in the MVD+IN group, who were only found thickened arachnoid adhesions during the operation that could not be fully released, was significantly higher than that of the MVD group (30.0%) (p<0.05), while the efficacy (91.7% vs. 70%) of the two groups was not statistically different (p>0.05). For patients whose arachnoid adhesions were completely released, there had no significant difference (p>0.05) in the efficacy (87% vs. 94.7%) and recurrence rate (5.0% vs. 11.1%). The incidence of postoperative facial numbness (88.6%) in the MVD+IN group was higher than that in the MVD group (10.3%) (p<0.01). The long-term incidence of facial numbness was not statistically significant (p>0.05). In the 18-36 months follow-up, the recurrence rate of patients in the MVD+IN group (9.7%) and in the MVD group (16%) were not statistically different (p>0.05). Conclusion: A retrospective comparison of patients with recurrent TN showed that both MVD and MVD combined with IN can effectively treat recurrent TN. Compared with MVD alone, MVD combined with IN can effectively improve the pain cure rate of patients with recurrent TN who have only severe arachnoid adhesions. The combination does not increase the incidence of longterm facial numbness and other complications. [ABSTRACT FROM AUTHOR]

The role of PDGF-B and its receptor in meningeal tumorigenesis is not clear. We investigated the role of PDGF-B in mouse meningioma development by generating autocrine stimulation of the arachnoid through the platelet-derived growth factor receptor (PDGFR) using the RCAStv-a system. To specifically target arachnoid cells, the cells of origin of meningioma, we generated the PGDStv-a mouse (Prostaglandin D synthase). Forced expression of PDGF-B in arachnoid cells in vivo induced the formation of Grade I meningiomas in 27% of mice by 8 months of age. In vitro, PDGF-B overexpression in PGDS-positive arachnoid cells lead to increased proliferation.We found a correlation of PDGFR-B expression and NF2 inactivation in a cohort of human meningiomas, and we showed that, in mice, Nf2 loss and PDGF over-expression in arachnoid cells induced meningioma malignant transformation, with 40% of Grade II meningiomas. In these mice, additional loss of Cdkn2ab resulted in a higher incidence of malignant meningiomas with 60% of Grade II and 30% of Grade III meningiomas. These data suggest that chronic autocrine PDGF signaling can promote proliferation of arachnoid cells and is potentially sufficient to induce meningiomagenesis. Loss of Nf2 and Cdkn2ab have synergistic effects with PDGF-B overexpression promoting meningioma malignant transformation.

Teaching point: The scalpel sign is pathognomonic for a dorsal arachnoid web, a rare clinical-radiologic entity that can cause myelopathy.

Glioblastoma multiforme (GBM) is the most frequent and most aggressive primary brain tumor in adults, mainly located in the cerebral hemispheres. In the literature, few cases of primary GBM have been reported to have radiographic and intraoperative features of extra-axial lesions, leading to a diagnostic dilemma. Despite the advances in imaging modalities, the diagnosis of GBM can be challenging, and it is mainly based on the histopathologic confirmation of the excised tumor. We describe the case of a 76-year-old previously healthy female patient who presented to our hospital due to speech disturbances and cognitive impairment. The diagnosis of the tumor type on magnetic resonance imaging (MRI) was difficult, as the findings were suggestive of a malignant meningioma due to the heterogeneous enhancement of a dural-based mass with a dural tail sign. Moreover, the intraoperative findings revealed an extra-axial mass attached to the dura. A histological examination confirmed the diagnosis of glioblastoma with arachnoid infiltration. The patient underwent adjuvant radiotherapy and concomitant temozolomide treatment, she had clinical improvement postoperatively, and was stable during the six months of follow-up. Glioblastoma should be considered in the differential diagnosis of primary extra-axial mass with atypical and malignant features, especially in elderly patients.

Background: Although leptomeningeal melanin pigmentation is well-known, it is not described in the neurosurgical literature. Dark pigmentation native to these transparent membranes might have microsurgical relevance in identifying a plane of dissection.Objective: To describe the prevalence of leptomeningeal pigmentation and determine whether its recognition helps during microsurgical excision of extra-axial brain tumors.Materials and Methods: : This was a prospective cross-sectional observational study in cadavers and neurosurgical patients. Eight adult cadaveric brains were examined for leptomeningeal pigmentation and biopsies taken for histological studies. A total of 126 patients undergoing surgery for cerebellopontine angle and suprasellar lesions were included in the clinical study. The surgeon determined whether the recognition of pigmentation was useful during microneurosurgical arachnoid dissection.Results: Seven of 8 cadavers (87.5%) had leptomeningeal pigmentation on the ventral pons, optic chiasm, lamina terminalis, olfactory tract, and gyrus rectus and infrequently on the cerebral convexities. The prevalence of pigmentation was 76.9% in the clinical study, was seen in all pediatric patients, and was significantly higher in males (P = 0.009), with no significant association with skin color. Immunochemistry identified the pigmentation as melanin. Recognition of this pigmentation was deemed to be useful during tumor excision in 78% of the cases.Conclusions: Leptomeningeal melanin pigmentation has a prevalence of 76% to 87% in the Indian population and is more often seen in younger males. It is most commonly identified overlying the ventral brain stem and optic chiasm. Recognition of its presence is helpful during arachnoid dissection during most cerebellopontine angle and suprasellar tumor resections. [ABSTRACT FROM AUTHOR]

SummarySpontaneous lateral sphenoid cephaloceles arise from bony defects in the lateral sphenoid, in the absence of predisposing factors such as trauma, surgery, mass, or congenital skull base malformation. We reviewed CT and MR imaging findings and clinical data of 26 patients with spontaneous lateral sphenoid cephaloceles to better understand anatomic contributions to pathogenesis, varying clinical and imaging manifestations, and descriptive terminology. Two types of spontaneous lateral sphenoid cephaloceles were identified. In 15 of 26 patients, a type 1 spontaneous lateral sphenoid cephalocele was noted, herniating into a pneumatized lateral recess of the sphenoid sinus, and typically presenting with CSF leak and/or headache. In 11 of 26 patients, a type 2 spontaneous lateral sphenoid cephalocele was noted, isolated to the greater sphenoid wing without extension into the sphenoid sinus, presenting with seizures, headaches, meningitis, cranial neuropathy, or detected incidentally. All patients had sphenoid arachnoid pits, and 61% of patients had an empty or partially empty sella, suggesting that altered CSF dynamics may play a role in their genesis.

Background: Clival cystic lesions are not frequently seen in neurosurgery. Cystic lesion in the clivus can be part of a neoplastic process such as chordoma, chondrosarcoma, plasmacytoma, or metastasis. Rare types of pure cystic clival lesions include simple bone cysts and arachnoid cysts, which are asymptomatic most of the time and do not cause symptoms until they reach a large size. Case Description: This is a case report of a healthy 53-year-old male patient with a clival cystic lesion. The patient underwent surgical drainage and wall resection of the clival lesion with no postoperative complications. Intraoperative finding raised the possibility of the diagnosis of an arachnoid cyst. However, the pathology findings indicated a simple bone cyst. Conclusion: Simple bone cyst and arachnoid cyst in the clivus are rare, they should be considered in the diagnosis of clival cystic lesions. [ABSTRACT FROM AUTHOR]

Objective: Recent studies have reported that arachnoid plasty (ARP) using gelatin sponges with fibrin glue reduced the occurrence of chronic subdural hematoma (CSDH) following clipping surgery for unruptured intracranial aneurysm (UIA). This metaanalysis was conducted to collate further evidence for the efficacy of ARP in preventing postoperative CSDH. Methods: Data of patients who underwent clipping surgery were extracted from PubMed, EMBASE, and Cochrane Central Register of Controlled Trials by two independent reviewers. A random effects model was used to investigate the efficacy of ARP by using odd ratios (ORs) and 95% confidence intervals (CIs). A meta-regression analysis for male sex was additionally preformed. Results: Data from six studies with 1715 patients were consecutively included. Meta-analysis revealed that ARP was significantly associated with lower rates of CSDH development after surgical clipping for UIA (ARP group vs. control group: 3.2% vs. 7.2%; OR, 0.40; 95% CI, 0.18-0.93; I2=44.3%; p=0.110). Meta-regression analysis did not highlight any modifying effect of the male sex on postoperative CSDH development (p=0.951). Conclusion: This meta-analysis indicated that ARP reduced the incidence rates of CSDH following clipping surgery for UIA. If feasible, ARP would be implemented as an additional surgical technique to prevent postoperative CSDH development during surgical clipping of UIA. [ABSTRACT FROM AUTHOR]

Introduction: Arachnoid cysts are benign extracerebral collections of cerebrospinal fluid; a very low incidence has been described as part of all intracranial lesions (about 1%). They appear in the different anatomical areas of the neuroaxis where arachnoids exist; the majority are supratentorial and in the middle fossa (50-60%). In general, less than 50% of cases present manifestations that merit surgical treatment. Case report: A 55-year-old female underwent surgery due to torpid evolution as a result of an arachnoid cyst in the posterior fossa. She started suffering from episodes of pulsatile headache 2 years ago without irradiation accompanied by occasional vertigo that was attenuated with conventional analgesia. In the past week, the pain was exacerbated, as was the vertigo, intolerance to the oral route, and generalized weakness. A scheduled surgical intervention was decided on, and a histopathological study reported characteristics compatible with an arachnoid cyst. Discussion: Arachnoid cysts are an uncommon pathology that sometimes requires surgical intervention. In the case presented, the incipient clinic manifestations showed that the patient had an abrupt progression in her intensity, perhaps due to an increase in size, conditioning the increasing headache, and added symptoms. This culminated in her assessment and surgical intervention due to the important compression of the brain stem. It was considered a successful procedure due to the disappearance of the symptoms and the return to her activities. Conclusions: Surgical intervention for posterior fossa arachnoid cyst is an excellent treatment when the symptoms do not improve after having maintained an expectant conduct through conservative management. [ABSTRACT FROM AUTHOR]

Background: Sellar arachnoid cysts (SACs) are rare lesions and incidentally found on brain imaging. The pathophysiology is poorly understood. Some authors suggested that SACs develop as a herniation of arachnoid membrane through the diaphragma sellae followed by cyst formation. Furthermore, Meyer et al. postulated that SACs are formed by splitting of the arachnoid layers. Symptomatic SACs present with headache, visual field deficit, or pituitary dysfunction. The data are limited on the indications and timing for intervention. We present a case of symptomatic SAC that was fenestrated using orbitofrontal approach. A 64-year-old female presented with chronic headaches and blurriness of vision. She was previously diagnosed with diabetes insipidus (DI) that was treated with desmopressin, magnetic resonance imaging (MRI) of her brain at that time was normal. Later on, she developed severe headaches that were managed medically. A year later, she had an episode of generalized seizure that led to the discovery of SAC on brain MRI. On examination, she had a left-sided monocular temporal hemianopia. The patient underwent an orbitofrontal craniotomy for fenestration of the SAC. At 6-month follow-up, her headaches had significantly improved with the resolution of the visual deficit. In addition, the DI had resolved, and the desmopressin was discontinued. Conclusion: SACs are rare with no consensus on the indications for surgery. Our experience suggests that fenestration of SAC through transcranial approach is a valid option for patients with visual deficit and/or pituitary dysfunction. [ABSTRACT FROM AUTHOR]

Background: CSF has long been accepted to circulate throughout the subarachnoid space, which lies between the arachnoid and pia maters of the meninges. How the CSF interacts with the cellular components of the developing postnatal meninges including the dura, arachnoid, and pia of both the meninges at the surface of the brain and the intracranial meninges, prior to its eventual efflux from the cranium and spine, is less understood. Here, we characterize small and large CSF solute distribution patterns along the intracranial and surface meninges in neonatal rodents and compare our findings to meningeal CSF solute distribution in a rodent model of intraventricular hemorrhage-posthemorrhagic hydrocephalus. We also examine CSF solute interactions with the tela choroidea and its pial invaginations into the choroid plexuses of the lateral, third, and fourth ventricles., Methods: 1.9-nm gold nanoparticles, 15-nm gold nanoparticles, or 3 kDa Red Dextran Tetramethylrhodamine constituted in aCSF were infused into the right lateral ventricle of P7 rats to track CSF circulation. 10 min post-1.9-nm gold nanoparticle and Red Dextran Tetramethylrhodamine injection and 4 h post-15-nm gold nanoparticle injection, animals were sacrificed and brains harvested for histologic analysis to identify CSF tracer localization in the cranial and spine meninges and choroid plexus. Spinal dura and leptomeninges (arachnoid and pia) wholemounts were also evaluated., Results: There was significantly less CSF tracer distribution in the dura compared to the arachnoid and pia maters in neonatal rodents. Both small and large CSF tracers were transported intracranially to the arachnoid and pia mater of the perimesencephalic cisterns and tela choroidea, but not the falx cerebri. CSF tracers followed a similar distribution pattern in the spinal meninges. In the choroid plexus, there was large CSF tracer distribution in the apical surface of epithelial cells, and small CSF tracer along the basolateral surface. There were no significant differences in tracer intensity in the intracranial meninges of control vs. intraventricular hemorrhage-posthemorrhagic hydrocephalus (PHH) rodents, indicating preserved meningeal transport in the setting of PHH., Conclusions: Differential CSF tracer handling by the meninges suggests that there are distinct roles for CSF handling between the arachnoid-pia and dura maters in the developing brain. Similarly, differences in apical vs. luminal choroid plexus CSF handling may provide insight into particle-size dependent CSF transport at the CSF-choroid plexus border., (© 2024. The Author(s).)

Hydrocephalus (HC) is an imbalance in cerebrospinal fluid (CSF) secretion/absorption resulting in fluid accumulation within the brain with consequential pathophysiology. Our research has identified a unique cerebral folate system in which depletion of CSF 10-formyl-tetrahydrofolate-dehydrogenase (FDH) is associated with cortical progenitor cell-cycle arrest in hydrocephalic Texas (H-Tx) rats. We used tissue culture, immunohistochemistry, in-situ PCR and RT-PCR and found that the in-vitro proliferation of arachnoid cells is highly folate-dependent with exacerbated proliferation occurring in hydrocephalic CSF that has low FDH but high folate-receptor-alpha (FRα) and folate. Adding FDH to this CSF prevented aberrant proliferation indicating a regulatory function of FDH on CSF folate concentration. Arachnoid cells have no detectable mRNA for FRα or FDH, but FDH mRNA is found in the choroid plexus (CP) and CSF microvesicles. Co-localization of FDH, FRα and folate suggests important functions of FDH in cerebral folate transport, buffering and function. In conclusion, abnormal CSF levels of FDH, FRα and folate inhibit cortical cell proliferation but allow uncontrolled arachnoid cell division that should increase fluid absorption by increasing the arachnoid although this fails in the hydrocephalic brain. FDH appears to buffer available folate to control arachnoid proliferation and function. [ABSTRACT FROM AUTHOR]

Background: Cerebellopontine angle (CPA) tumors are usually benign, and they are divided into extra-axial, intra-axial, extradural, and petrous axis tumors. CPA pathologies can be asymptomatic or it may present with vertigo, tinnitus, or unilateral hearing loss depending upon the site of tumor origin and displacement of the neurovascular structure. Aim and Objectives: To evaluate the role of magnetic resonance imaging (MRI) aided with contrast-enhanced MRI as an imaging modality for diagnosis of CPA lesions. Materials and Methods: Analysis of 36 patients of CPA lesions over a period of 2 years was done. MRI was performed on Siemens 1.5 Tesla MAGNETOM Avanto Machine. Conclusion: There are spectrums of pathologies, which can present with these symptoms, which includes tumors, vascular malformations, and vascular loop compressing vestibulocochlear nerve or mastoid pathology so it is important to investigate the patient by MRI. Contrast-enhanced MRI is the most sensitive investigation in the evaluation of the CPA lesions, its characteristic, and its extent.

The suprachoroidal region of the eye comprises vascular channels, melanocytes, and thin fibroblasts with elongated cytoplasm that are positioned directly adjacent to the densely collagenous sclera. Morphological similarities between these suprachoroidal fibroblasts and arachnoid cells and perineurial cells have been recognized, but whether these fibroblasts have a perineurial cell-like immunophenotype is not known. To further examine the relationship of these three cell types, we investigated the comparative expression of epithelial membrane antigen (EMA), the tight junction protein claudin-1, glucose transporter-1 (Glut-1), and CD34 in suprachoroidal fibroblasts, arachnoid of the optic nerve sheath, and perineurium of ciliary nerves in eight human eye specimens. Granular, diffuse, and cytoplasmic EMA expression was seen in suprachoroidal fibroblasts, but this was not contiguous with the similar pattern of EMA expression in adjacent perineurium and arachnoid. CD34 expression in suprachoroidal fibroblasts was also seen, similar to arachnoid and perineurium. Claudin-1 and Glut-1 were not consistently expressed in suprachoroidal fibroblasts, distinguishing them from perineurial cells in particular and suggesting that these fibroblasts do not arise directly from adjacent arachnoid or perineurium. Nonetheless, the overlapping morphology and protein expression suggest phenotypic similarities in these cells that protect and support adjacent retina, optic nerve, and peripheral nerve. [ABSTRACT FROM AUTHOR]

Giant arachnoid granulations (GAGs) are minimally investigated. Here, we systematically review the available data in published reports to better understand their etiologies, nomenclature, and clinical significance. In the literature, 195 GAGs have been documented in 169 persons of varied ages (range, 0.33 to 91 years; mean, 43 ± 20 years; 54% female). Prior reports depict intrasinus (i.e., dural venous sinus, DVS) (84%), extrasinus (i.e., diploic or calvarial) (15%), and mixed (1%) GAG types that exhibit pedunculated, sessile, or vermiform morphologies. GAG size ranged from 0.4 to 6 cm in maximum dimension (mean, 1.9 ± 1.1 cm) and encompassed symptomatic or non-symptomatic enlarged arachnoid granulations (≥1 cm) as well as symptomatic subcentimeter arachnoid granulations. A significant difference was identified in mean GAG size between sex (females, 1.78 cm; males, 3.39 cm; p < 0.05). The signs and symptoms associated with GAGs varied and include headache (19%), sensory change(s) (11%), and intracranial hypertension (2%), among diverse and potentially serious sequelae. Notably, brain herniation was present within 38 GAGs (22%). Among treated individuals, subsets were managed medically (19 persons, 11%), surgically (15 persons, 9%), and/or by endovascular DVS stenting (7 persons, 4%). Histologic workup of 53 (27%) GAG cases depicted internal inflammation (3%), cystic change consistent with fluid accumulation (2%), venous thrombosis (1%), hemorrhage (1%), meningothelial hyperplasia (1%), lymphatic vascular proliferation (1%), and lymphatic vessel obliteration (1%). This review emphasizes heterogeneity in GAG subtypes, morphology, composite, location, symptomatology, and imaging presentations. Additional systematic investigations are needed to better elucidate the pathobiology, clinical effects, and optimal diagnostic and management strategies for enlarged and symptomatic arachnoid granulation subtypes, as different strategies and size thresholds are likely applicable for medical, interventional, and/or surgical treatment of these structures in distinct brain locations.