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The arachnoid barrier delineates the border between the central nervous system and dura mater. Although the arachnoid barrier creates a partition, communication between the central nervous system and the dura mater is crucial for waste clearance and immune surveillance 1 , 2 . How the arachnoid barrier balances separation and communication is poorly understood. Here, using transcriptomic data, we developed transgenic mice to examine specific anatomical structures that function as routes across the arachnoid barrier. Bridging veins create discontinuities where they cross the arachnoid barrier, forming structures that we termed arachnoid cuff exit (ACE) points. The openings that ACE points create allow the exchange of fluids and molecules between the subarachnoid space and the dura, enabling the drainage of cerebrospinal fluid and limited entry of molecules from the dura to the subarachnoid space. In healthy human volunteers, magnetic resonance imaging tracers transit along bridging veins in a similar manner to access the subarachnoid space. Notably, in neuroinflammatory conditions such as experimental autoimmune encephalomyelitis, ACE points also enable cellular trafficking, representing a route for immune cells to directly enter the subarachnoid space from the dura mater. Collectively, our results indicate that ACE points are a critical part of the anatomy of neuroimmune communication in both mice and humans that link the central nervous system with the dura and its immunological diversity and waste clearance systems. Arachnoid cuff exit points create openings in the arachnoid barrier enabling the drainage of cerebrospinal fluid and exchange of molecules and cells between the dura and the subarachnoid space, therefore physically connecting the brain and the dura.

Background Spinal arachnoid cysts (SAC) and spinal arachnoid webs (SAW) are intradural pathologies, often presenting with pain and/or myelopathic symptoms. Reports on postoperative outcomes for SAC and SAW are scarce. This study aims to assess the surgical outcomes of SAC and SAW. Methods Patients who underwent surgical treatment for SAC or SAW at our institution between 2011 and 2023 were retrospectively reviewed. Demographic data, radiological findings, surgical management, and clinical outcomes were evaluated using the modified McCormick (mMC) scale. Outcomes were categorized as \"favorable\" (mMC I-II) or \"unfavorable\" (mMC III-V). Results A total of 35 patients (29 SAC, 6 SAW) were analyzed. Mean age was 50.9 (SD ± 9.8) years. Males comprised 70.3% of cases (SAC: 64.5%, SAW: 100%). Most common symptoms were local or radiating pain (SAC 77.4%; SAW 100%), gait-disturbance (SAC 45.2%; SAW 16.7%), sensory-deficits (SAC 32.3%; SAW 66.7%) and impaired motor function (SAC 20%; SAW 16.7%). Median preoperative mMC was 2 in both groups (SAC IQR: 1; SAW IQR: 1). Median postoperative mMC was 1 in both groups (SAC CI 1.07–1.34; SAW CI 0.74–1.60). Favorable outcome (postoperative mMC I-II) was achieved in 26 SAC patients (90%) and 5 SAW patients (83%) respectively. Surgical complications occurred in 14.7%, all in the SAC group, without lasting deficits. Conclusion Surgical treatment for SAC and SAW appears to have an overall favorable outcome, though larger cohort analyses are needed. Surgery should be considered in symptomatic patients.

A quadrigeminal cistern arachnoid cyst is an extremely rare cause of trigeminal neuralgia in adulthood. This report presents the fourth case in the literature of trigeminal neuralgia caused by a giant quadrigeminal cistern arachnoid cyst. A 52-year- old woman presented with a 3-month history of cerebellar ataxia and vertigo. She had a 2-year history of trigeminal neuralgia that was unresponsive to medical therapy. Neuroimaging studies revealed a cystic lesion in the quadrigeminal cistern associated with hydrocephalic enlargement. Using an infratentorial supracerebellar approach, neuroendoscope-assisted decompression and fenestration of the cyst were performed. Postoperatively, the patient was pain-free and able to walk unaided without symptoms of ataxia. Keywords: Arachnoid cyst; ataxia; hydrocephalus; quadrigeminal cistern; trigeminal neuralgia.

PurposeIntrasellar arachnoid cysts are extremely rare, and their differentiation from other cystic lesions can be challenging because of their similar imaging characteristics.MethodsThis study aimed to describe the imaging characteristics observed in five patients and correlate them with developmental and growth mechanisms.ResultsThese cysts are characterized by the lack of contrast enhancement in their walls and posterior displacement of the pituitary gland. As a result, no enhancing tissue is present at the anterior portion of the sella where it interfaces with the sphenoid sinus.ConclusionWe believe that this sign will lead to more accurate diagnosis and improve surgical planning.

Purpose Children diagnosed with suprasellar arachnoid cysts often concurrently have hydrocephalus. This study aims to classify the relationship between suprasellar arachnoid cysts and hydrocephalus, discussing surgical strategies—shunting or neuroendoscopic approaches—and their sequence, based on this classification. Methods A retrospective analysis was conducted on 14 patients diagnosed with suprasellar arachnoid cysts and hydrocephalus, treated surgically by the first author between January 2016 and December 2020. Clinical features, radiological findings, surgical strategies, and outcomes were reviewed. The classification of the relationship between the suprasellar arachnoid cysts and hydrocephalus was developed and illustrated with specific cases. Recommendations for future surgical management based on this classification are provided. Results We classified the relationship between suprasellar arachnoid cysts and hydrocephalus into three categories. SACH-R1, the direct type, represents cases where the cysts cause obstructive hydrocephalus. Here, neuroendoscopic ventriculocystocisternostomy (VCC) effectively treats both conditions. SACH-R2, the juxtaposed type, involves concurrent occurrences of cysts and hydrocephalus without a causative link. This is further subdivided into SACH-R2a, where acute progressive communicating hydrocephalus coexists with the cyst, initially managed with a ventriculoperitoneal shunt, followed by VCC upon stabilization of hydrocephalus; and SACH-R2b, where the cyst coexists with chronic stable communicating hydrocephalus, first addressed with VCC, followed by monitoring and potential secondary shunting if needed. Key factors differentiating SACH-R2a from SACH-R2b include the patient's age, imaging signs of fourth ventricle and cisterna magna enlargement, and the rapid progression or chronic stability and severity of hydrocephalus symptoms. SACH-R3, the reverse type, describes scenarios where shunting for hydrocephalus leads to the development or enlargement of the cyst, managed via neuroendoscopic VCC with precautions to prevent infections in existing shunt systems. Conclusion The simultaneous presence of suprasellar arachnoid cysts and hydrocephalus requires a nuanced understanding of their complex relationship for optimal surgical intervention. The analysis and classification of their relationship are crucial for determining appropriate surgical approaches, including the choice and sequence of shunting and neuroendoscopic techniques. Treatment should be tailored to the specific type identified, rather than blindly opting for neuroendoscopy. Particularly for SACH-R2a cases, we recommend initial ventriculoperitoneal shunting.

Background Arachnoid cysts are extra parenchymal, intra-arachnoid fluid collections of unknown origin, similar in content to cerebrospinal fluid. Suprasellar arachnoid cysts are a rarer localization resulting from abnormalities of the Liliequist membrane or cystic dilatation of the interpeduncular cisterna. We aimed to contribute to the literature by presenting a series of suprasellar arachnoid cyst cases with endoscopic intervention and long-term results. Methods This study analyzed radiographic data, clinical symptoms, surgical records, and videos of giant arachnoid cysts that underwent endoscopic surgery between 2013 and 2023. Cyst volumes and Evan’s indexes were calculated both preoperatively and postoperatively. Results The patient population consisted of 3 males (21.4%, 3/14 patients) and 11 females (78.5%, 11/14 patients). Their age at the time of surgery ranged from 1 year to 56 years (mean: 14.4 years). Of the total 14 patients, 4 (28.5%, 4/14 patients) were adults (age ≥ 18 years), and 10 (71.4%, 10/14 patients) were pediatric (age < 18 years). The most common presenting complaints were gait disturbance (21.4%, 3/14 patients), headache (21.4%, 3/14 patients), increased head circumference (14.2%, 2/14 patients), hormonal disorders (14.2%, 2/14 patients), seizures (14.2%, 2/14 patients), and forgetfulness (7.1%, 1/14 patients). Ventriculocystocisternostomy was performed in all patients. The most common perioperative complication was bleeding controlled by irrigation (28.5%, 4/14 patients). The mean follow-up period was 63.8 months (min:12 months-max:125 months). In the postoperative long-term follow-up, the preoperative neurologic examinations of the patients showed complete recovery, and hormonal problems returned to normal. Conclusions Endoscopic options for the surgery of rare giant suprasellar arachnoid cysts, especially ventriculocisternostomy, are safe, less invasive, and successful, with fewer recurrences and the need for a second operation in the long-term results of patients who underwent ventriculocisternostomy according to our experience.

ObjectiveThe best treatment strategies for cerebral arachnoid cysts (CAC) are still up for debate. In this study, we present CAC management, outcome data, and risk factors for recurrence after surgical treatment, focusing on microscopic/endoscopic approaches as compared to minimally invasive stereotactic procedures in children and adults.MethodsIn our single-institution retrospective database, we identified all patients treated surgically for newly diagnosed CAC between 2000 and 2022. Microscopic/endoscopic surgery (ME) aimed for safe cyst wall fenestration. Stereotactic implantation of an internal shunt catheter (STX) to drain CAC into the ventricles and/or cisterns was used as an alternative procedure in patients aged ≥ 3 years. Treatment decisions in favor of ME vs. STX were made by interdisciplinary consensus. The primary study endpoint was time to CAC recurrence (TTR). Secondary endpoints were outcome metrics including clinical symptoms and MR-morphological analyses. Data analysis included subdivision of the total cohort into three distinct age groups (AG1, < 6 years; AG2, 6–18 years; AG3, ≥ 18 years).ResultsSixty-two patients (median age 26.5 years, range 0–82 years) were analyzed. AG1 included 15, AG2 10, and AG3 37 patients, respectively. The main presenting symptoms were headache and vertigo. In AG1 hygromas, an increase in head circumference and thinning of cranial calvaria were most frequent. Thirty-five patients underwent ME and 27 STX, respectively; frequency did not differ between AGs. There were two (22.2%) periprocedural venous complications in infants (4- and 10-month-old) during an attempt at prepontine fenestration of a complex CAC, one with fatal outcome in a 10-month-old boy. Other complications included postoperative bleeding (2, 22.2%), CSF leaks (4, 44.4%), and meningitis (1, 11.1%). Overall, clinical improvement and significant volume reduction (p = 0.008) were seen in all other patients; this did not differ between AGs. Median follow-up for all patients was 25.4 months (range, 3.1–87.1 months). Recurrent cysts were seen in 16.1%, independent of surgical procedure used (p = 0.7). In cases of recurrence, TTR was 7.9 ± 12.7 months. Preoperative ventricular expansion (p = 0.03), paresis (p = 0.008), and age under 6 years (p = 0.03) were significant risk factors for CAC recurrence in multivariate analysis.ConclusionsIn patients suffering from CAC, both ME and STX can improve clinical symptoms at low procedural risk, with equal extent of CAC volume reduction. However, in infants and young children, CAC are more often associated with severe clinical symptoms, stereotactic procedures have limited use, and microsurgery in the posterior fossa may bear the risk of severe venous bleeding.

Brain tumors represent the second most frequent etiology in patients with focal seizure onset before 18 years of age and submitted to epilepsy surgery. Hence, this category of brain tumors, herein defined as low-grade, developmental, epilepsy-associated brain tumors (LEAT) is different from those frequently encountered in adults as (A): 77% of LEAT occur in the temporal lobe; (B): the vast majority of LEAT are of low malignancy and classified as WHO I°; (C): LEAT are often composed of mixed glial and neuronal cell components and present with variable growth patterns including small cysts or nodules; (D): LEAT do not share common gene driving mutations, such as IDH1 or 1p/19q co-deletions. Characteristic entities comprise the ganglioglioma (GG), the dysembryoplastic neuroepithelial tumor (DNT), the angiocentric glioma (AG), the isomorphic diffuse glioma (IDG) and the papillary glio-neuronal tumor (PGNT), representing 73.2% of 1680 tumors collected in a large German series of 6747 patients submitted to epilepsy surgery. In the realm of exciting discoveries of genetic drivers of brain tumors new genes have been also reported for LEAT. BRAF V600E mutations were linked to GG with CD34 expression, FGFR1 mutations to DNT, MYB alterations to AG and also IDG and PRKCA fusions to PGNT, suggesting the possibility to also develop a genetically driven tumor classification scheme for LEAT. Rare availability of LEAT in a single center is a challenging obstacle, however, to systematically unravel the neurobiological nature and clinical behavior of LEAT. Other challenges in need of clarification include malignant tumor progression of LEAT entities, seizure relapse in patients following bulk tumor resection and the controversial issue of associated focal cortical dysplasia as additional pathomechanism. In order to advance our understanding and promote reliable diagnostic work-up of LEAT, we recommend, therefore, international collaboration to achieve our goals.

ABSTRACT Background Spinal adhesive arachnoidopathy (SAA) is a chronic pathology associated with persistent inflammatory responses in the arachnoid. Adhesive arachnoiditis (AA) is one of the major forms of SAA, with accompanying secondary complications. Therefore, we aimed to systematically review both clinical and animal model studies related to SAA to gain a deeper understanding of this unique pathology. Methods A literature search was conducted in PubMed, EMBASE, and Cochrane Library databases to retrieve relevant publications up to October 2022. Clinical manifestations, etiologies, imaging modalities, treatments, and prognosis in patients with SAA were collected. Data from animal experiments related to SAA were also extracted. Results A total of 176 studies, including 147 clinical and 29 animal model studies, with a total of 510 patients were enrolled in this study. Pain (37.5%), abnormal nerve sensations (39.58%), and abnormal motor function (78.75%) were the top three common symptoms of SAA. Major etiologies included trauma (22.7%), infection (17.73%), surgery (15.37%), and hemorrhage (13.48%). MRI was widely used to confirm the diagnosis. AA could be involved in cervical (96/606, 15.84%), thoracic (297/606, 49.01%), lumbar (174/606, 28.71%), and sacrococcygeal (39/606, 6.44%) vertebral segments. Patients with AA in cervical segments had a higher post‐surgery recovery rate (p = 0.016) compared to that of other segments. The common pathological diagnoses of SAA were AA (80.82%), AA combined with arachnoid cyst (12.79%), arachnoid calcification/scars (3.43%), and arachnoid web/fibrosis (2.97%). Patients with AA were more likely to develop syringomyelia, compared with patients with other forms of SAA (p < 0.001). Animal studies mainly focused on new AA therapeutic agents (n = 14), the pathomechanism of AA (n = 14), and the development of new MRI sequences for improved diagnosis (n = 1). Conclusions The pathological consequences of SAA are more complex than AA and manifest in different forms, such as AA combined with arachnoid cyst, arachnoid calcification/scars, and arachnoid web/fibrosis. In many instances, AA was associated with secondary syringomyelia. Unspecific clinical manifestations of SAA may easily lead to misdiagnosis and missed diagnosis. Although SAA may result from multiple etiologies, including spinal trauma, meningitis, spinal surgery, and hemorrhage, the pathogenesis and treatment of SAA have still not been standardized.

This study examines the arachnoid fossae (AF) in crania from early modern Wrocław, Poland, and their connection to endocranial lesions, specifically abnormal blood vessel impressions (ABVI) and periosteal appositions of the dura mater (PADM). AF are fovea on the inner surface of the cranial bone, which arise as the result of arachnoid granulations’ (AG) protruding and causing the resorption of the bone. ABVI and PADM are non-specific pathological lesions caused by inflammation and hemorrhages in the meninges. The goal of the study is to determine if the size of AF is associated with the occurrence of endocranial lesions (ABVI and PADM), whether they can aid in diagnosing pathological conditions in historical populations, and to propose a measurement methodology. Using an endoscopic device, the study analyzed 80 adult crania from a collection in Wrocław, Poland. The size of AF was measured using scaled photographs, and the occurrence and severity of ABVI and PADM were also documented. The study then investigated the relationship between the size of AF and the presence of ABVI and PADM. It was determined that the individuals with ABVI had greater AF than those without the lesions. The results indicate that while the presence of AF can be considered a normal cranial variation, their size may be useful in diagnosing pathological conditions in the meninges, such as trauma, tumors, or infectious diseases.