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The glymphatic system theory postulates that brain waste is removed through the cerebrospinal fluid (CSF) flow. According to this theory, CSF in the subarachnoid space (SAS) moves to the perivascular space around the penetrating arteries, flows into parenchyma to mix with interstitial fluid and brain waste, and then moves to the perivenous space to be flushed out of the brain. Despite the controversies about the glymphatic theory, it is clear that SAS plays a key role in waste clearance. For instance, the SAS around the middle cerebral artery is known to be highly involved in glymphatic influx. While diffusion tensor imaging has been used for studying the glymphatic system, there has been limited exploration of age-related changes in diffusion anisotropy within SAS and their regional variations. Given the narrow and heterogeneous morphology of SAS, the fractional anisotropy (FA) in diverse brain regions may be more relevant to glymphatic transport than mean diffusivity (MD). The goal of this study was to investigate FA in SAS to observe age-related changes across different brain regions and to interpret the results based on the glymphatic transport. We segmented SAS in the whole brain of 83 young adults and divided SAS into four cortical lobes. We demonstrated regional variations in FA and MD within SAS and an age-related decline in FA among young adults, indicating that diffusion within SAS becomes more isotropic with aging. These findings raise new questions about the factors influencing diffusion anisotropy within SAS, which are relevant to glymphatic transport., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 International Brain Research Organization (IBRO). Published by Elsevier Inc. All rights reserved.)

Background and Purpose: The glymphatic (glia-lymphatic) system is a paravascular pathway for the clearance of waste metabolites including amyloid β from the brain. Serial T1 relaxation time measurements after the intrathecal injection of gadolinium-based contrast agents facilitate the analysis of the temporal dynamics that may be different in patients with spontaneous intracranial hypotension (SIH) and those without SIH., Materials and Methods: 3D T1-weighted magnetization-prepared 2 rapid gradient echo sequences were acquired in 4 patients with SIH with proved CSF leaks and 12 patients without SIH before, 2-4, 6-8, and 24-48 hours after intrathecal gadobutrol injection. MR scans were warped to the Montreal Neurological Institute space and serial scans were coregistered. T1 relaxation times were measured in predefined ROIs including the subarachnoid space, cortex, white matter, and cervical lymph nodes., Results: In the subarachnoid space and cortex, T1 relaxation times decreased after 2-4 and 6-8 hours before they increased again. In contrast, in the white matter of the temporal lobe T1 relaxation time still decreased after 24-48 hours. There was a striking difference in patients with SIH who did not show a clear contrast distribution within the brain parenchyma., Conclusions: T1 relaxation time curves are compatible with a convective flow driven by arterial pulsations via paravascular spaces surrounding penetrating arteries into the brain's interstitial fluid in the deep white matter. Different curves in patients with SIH and those without SIH indicate that the CSF pressure also impacts the temporal kinetics of the glymphatic system., (© 2024 by American Journal of Neuroradiology.)

Background: Subarachnoid hyperdensities after mechanical thrombectomy (MT) are a common finding. However, it is often regarded as clinically insignificant., Objective: With this single-center investigation, to identify the prevalence of subarachnoid hyperdensities following MT, associated predictors, and the impact on the clinical outcome of the patients., Methods: 383 patients from the stroke registry were analyzed for the presence of subarachnoid hyperdensities on flat detector CT (FDCT) directly after the completion of MT, and on follow-up dual-energy CT, then classified according to a visual grading scale. 178 patients were included with anterior circulation occlusions. Regression analysis was performed to identify significant predictors, and Kruskal-Wallis analysis and Χ 2 test were performed to test the variables among the different groups. The primary outcome was the modified Rankin Scale (mRS) score at 90 days and was analyzed with the Wilcoxon-Mann-Whitney rank-sum test., Results: The prevalence of subarachnoid hyperdensities on FDCT was (66/178, 37.1%) with patients experiencing a significant unfavorable outcome (P=0.035). Significantly fewer patients with subarachnoid hyperdensities achieved a mRS score of ≤3 at 90 days 25/66 (37.9%) vs 60/112 (53.6%), P=0.043). In addition, mortality was significantly higher in the subarachnoid hyperdensities group (34.8% vs 19.6%, P=0.024). Distal occlusions and a higher number of device passes were significantly associated with subarachnoid hyperdensities (P=0.026) and (P=0.001), respectively. Patients who received intravenous tissue plasminogen activator had significantly fewer subarachnoid hyperdensities (P=0.029)., Conclusions: Postinterventional subarachnoid hyperdensities are a frequent finding after MT and are associated with neurological decline and worse functional outcome. They are more common with distal occlusions and multiple device passes., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Histological studies have for decades documented that each of the classical meningeal membranes contains multiple fibroblast layers with distinct cellular morphology. Particularly, the sublayers of the arachnoid membranes have received attention due to their anatomical complexity. Early studies found that tracers injected into the cerebrospinal fluid (CSF) do not distribute freely but are restricted by the innermost sublayer of the arachnoid membrane. The existence of restrictions on CSF movement and the subdivision of the subarachnoid space into several distinct compartments have recently been confirmed by in vivo 2-photon studies of rodents, as well as macroscopic imaging of pigs and magnetic resonance imaging of human brain. Based on in vivo imaging and immunophenotyping characterization, we identified the structural basis for this compartmentalization of the subarachnoid space, which we term 'Subarachnoid lymphatic-like membrane', SLYM. The SLYM layer engages the subarachnoid vasculature as it approaches the brain parenchyma, demarcating a roof over pial perivascular spaces. Functionally, the separation of pial periarterial and perivenous spaces in the larger subarachnoid space is critical for the maintenance of unidirectional glymphatic clearance. In light of its close apposition to the pial surface and to the brain perivascular fluid exit points, the SLYM also provides a primary locus for immune surveillance of the brain. Yet, the introduction of SLYM, in terms of its anatomic distinction and hence functional specialization, has met resistance. Its critics assert that SLYM has been described in the literature by other terms, including the inner arachnoid membrane, the interlaminate membrane, the outer pial layer, the intermediate lamella, the pial membrane, the reticular layer of the arachnoid membrane or, more recently, BFB2-3. We argue that our conception of SLYM as an anatomically and functionally distinct construct is both necessary and warranted since its functional roles are wholly distinct from those of the overlying arachnoid barrier layer. Our terminology also lends clarity to a complex anatomy that has hitherto been ill-described. In that regard, we also note the lack of specificity of DPP4, which has recently been introduced as a 'selected defining marker' of the arachnoid barrier layer. We note that DPP4 labels fibroblasts in all meningeal membranes as well as in the trabecula arachnoides and the vascular adventitial layers, thus obviating its utility in meningeal characterization. Instead, we report a set of glymphatic-associated proteins that serve to accurately specify SLYM and distinguish it from its adjacent yet functionally distinct membranes., (© 2024. The Author(s).)

Objective: Determining the long-term success of endoscopic third ventriculostomy (ETV) remains challenging. This study aimed to investigate the impact of clinical and radiological factors on ETV success in pediatric patients with hydrocephalus., Methods: The study included patients < 18 years old with hydrocephalus who underwent ETV between March 2014 and May 2021. Data including patient age, gender, history of previous shunt surgery, previous external ventricular drain placement, intraventricular hemorrhage history, and postoperative meningitis were extracted from medical records. Imaging features such as aqueductal stenosis, third ventricle floor bowing, displaced lamina terminalis, pulsatility index (PI), and maximum diameter of the cortical subarachnoid space (CSAS) were recorded for each patient using preoperative CT scans. Two independent neurosurgeons measured the CSAS maximum diameter and the PI. CSAS measurements were obtained on axial slices of the preoperative CT scans, whereas the PI was based on intraoperative third ventricle pulsatility. Patients were followed up for 1 year after surgery, with failure defined as the need for ventriculoperitoneal shunt (VPS) placement or death attributable to hydrocephalus., Results: Ninety-eight children with a mean age of 16.39 ± 19.07 months underwent ETV for hydrocephalus. No deaths were recorded, but over 6 months and 1 year of follow-up, 12.2% and 22.4% of patients, respectively, experienced documented ETV failure requiring VPS placement. At the 6-month follow-up, a smaller maximum diameter of the CSAS was significantly associated with ETV failure; multivariate analysis revealed that CSAS maximum diameter was a predictor of 6-month ETV failure. At the 1-year follow-up, a lower PI was significantly associated with ETV failure, and multivariate analysis confirmed the PI as a significant predictor of ETV failure within 1 year after surgery. CSAS and PI measurements were repeated to assess interrater reliability: the intraclass correlation coefficients were 0.897 and 0.669 for CSAS and PI, respectively., Conclusions: This study found that the CSAS maximum diameter and the PI are predictors of ETV failure at 6 months and 1 year, respectively. These findings highlight the importance of considering specific factors such as the CSAS and PI when assessing the likelihood of ETV success in pediatric patients with hydrocephalus. Further research and consideration of these factors may help optimize patient selection and improve outcomes for those undergoing ETV as a treatment for hydrocephalus.

Purpose: Idiopathic Normal pressure hydrocephalus (iNPH) is an under-diagnosed in elderly patients but none of the diagnostic tests are currently sufficiently sensitive or specific. The objective of this study was to analyze the dynamics of neurofluids by PC-MRI in relation to clinical evolution as measured using the iNPH grading scale after tap-test., Method: We prospectively included patients with suspected iNPH. All these patients underwent PCMRI to assess craniospinal hemohydrodynamics with analysis of the stroke volume of the cephalospinal fluid (CSF) within the Sylvius' aqueduct, within the high cervical subarachnoid spaces and the arteriovenous stroke volume. By this means, we calculated a compliance index. Morphological analysis was carried out using the DESH score. The infusion test was measuring the resistance to CSF flow. We analysed all these parameters according to the clinical improvement of the patients., Results: 23 patients were included. Compliance index assessed by PC-MRI was significantly higher in the group of patients with improvement > 10% (p = 0.015)., Conclusions: Our study highlights the importance of investigating arteriovenous and CSF interactions in iNPH. This involves understanding the physiological and pathophysiological mechanisms related to the circulation of neurofluids. The analysis of the interactions of these neurofluids allows for a comprehensive understanding of the system., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background/objectives: We aimed to measure cerebrospinal fluid (CSF) flow rates in the subarachnoid space (SAS) of the optic nerve (ON) by applying non-invasive diffusion-weighted MRI in patients with normal tension glaucoma (NTG) compared to age-matched controls., Subjects/methods: In this prospective study, an analysis of diffusion-weighted images of 26 patients with NTG (49ONs) and age-matched volunteers (52ONs) was conducted. Subjects were classified into 4 groups: group I (50-59 y., n = 12 eyes), group II (60-69 y., n = 16 eyes), group III (70-79 y., n = 18 eyes) and group IV ( > 80 y., n = 6 eyes) for NTGs and healthy volunteers, respectively. The flow-range ratio (FRR) between the frontal lobe SAS and the SAS of the ON was calculated for each age category group and then compared between age-categories as well as between NTGs and controls., Results: The mean FRR for age groups were (I) 0.54 ± 0.06 and 0.62 ± 0.03 (p < 0.05), (II) 0.56 ± 0.08 and 0.63 ± 0.03 (p < 0.05), (III) 0.54 ± 0.06 and 0.62 ± 0.02 (p < 0.001) as well as (IV) 0.61 ± 0.03 and 0.61 ± 0.04, for NTGs and controls, respectively. Using pooled data, the difference between the FRR in NTGs and controls was statistically significant (p < 0.0001). There were no statistically significant differences within the age categories of the control group. When comparing the FRR of NTGs by age categories, no statistically significant difference was found between the subgroups., Conclusions: FRR was significantly reduced in NTGs compared to age-matched controls without any significant differences within the age groups themselves. Given the physiological importance of CSF for the integrity of neurons, axons and glial cells, reduced CSF flow dynamics might be part of the underlying neurodegenerative process of NTG., (© 2024. The Author(s).)

Purpose: The traditional imaging findings reported in Sturge-Weber syndrome (SWS) include endpoints of cortical injury-cortical atrophy and cortical calcifications-but also what has been termed a "leptomeningeal angiomatosis," the latter recognized and reported as a leptomeningeal enhancement on magnetic resonance imaging (MRI). The objective of this study is to demonstrate through neuropathological correlation that the "leptomeningeal angiomatosis" in patients with Sturge-Weber syndrome (SWS), represents a re-opened primitive venous network in the subarachnoid space that likely acts as an alternative venous drainage pathway, seen separately to abnormal pial enhancement., Materials and Methods: Retrospective review of MR imaging and surgical pathology of patients that underwent surgery for epilepsy at a tertiary, children's hospital. A pediatric radiologist with more than 20 years of experience reviewed the MR imaging. Surgically resected brain specimens that had been sectioned and fixed in 10% paraformaldehyde for histologic processing, following processing and paraffin embedding, were cut into 5-µm unstained slides which were subsequently stained with hematoxylin and eosin (H&E). Slides were re-examined by a board-certified pediatric neuropathologist, and histologic features specifically relating to cerebral surface and vascularity were documented for correlation with MR imaging of the resected region performed prior to resection., Results: Five patients were reviewed (3 boys and 2 girls; the median age at the onset of seizures was 12 months (IQR, 7 to 45 months); the median age at surgery was 33 months (IQR, 23.5 to 56.5 months)). Surgical procedures included the following: 4, hemispherotomy (right: 2, left: 2) and 1, hemispherectomy (right). A subarachnoid space varicose network was present on both MRI and histology in 4 patients. Calcifications were seen on both MRI and histology in 3 patients. Abnormal leptomeningeal enhancement was present in 5 patients and seen separately from the subarachnoid vascular network in 4 patients., Conclusion: Histopathology confirmed the MRI findings of a subarachnoid space varicose network seen separately from leptomeningeal enhancement and presumed to represent an alternative venous drainage pathway to compensate for maldevelopment of cortical veins, the primary abnormality in SWS. No pial-based angioma was identified., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Toward further cerebro-spinal flow quantification in clinical practice, this study aims at assessing the variations in the cerebro spinal fluid flow pattern associated with change in the morphology of the subarachnoid space of the cervical canal of healthy humans by developing a computational fluid dynamics model., Methods: 3D T2-space MRI sequence images of the cervical spine were used to segment 11 cervical subarachnoid space. Model validation (time-step, mesh size, size and number of boundary layers, influences of parted inflow and inflow continuous velocity) was performed a 40-year-old patient-specific model. Simulations were performed using computational fluid dynamics approach simulating transient flow (Sparlart-Almaras turbulence model) with a mesh size of 0.6, 6 boundary layers of 0.05 mm, a time step of 20 ms simulated on 15 cycles. Distributions of components velocity and WSS were respectively analyzed within the subarachnoid space (intervertebral et intravertebral levels) and on dura and pia maters., Results: Mean values cerebro spinal fluid velocity in specific local slices of the canal range between 0.07 and 0.17 m.s-1 and 0.1 and 0.3 m.s-1 for maximum values. Maximum wall shear stress values vary between 0.1 and 0.5 Pa with higher value at the middle of the cervical spine on pia mater and at the lower part of the cervical spine on dura mater. Intra and inter-individual variations of the wall shear stress were highlighted significant correlation gwith compression ratio (r = 0.76), occupation ratio and cross section area of the spinal cord., Conclusion: The inter-individual variability in term of subarachnoid canal morphology and spinal cord position influence the cerebro-spinal flow pattern, highlighting the significance of canal morphology investigation before surgery., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Leblond et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: The intracranial fluid spaces (IFS), also known as "the extra-axial spaces," consist of the superficial cerebral sulci, the Sylvian fissures, the basal cisterns, the third ventricle, the fourth ventricle, and the two lateral ventricles. In diseases such as schizophrenia, Alzheimer's, Parkinson's, and especially hydrocephalus, IFS' enlargements are observed., Objective: Our study aimed to determine the mean values of IFS measurements in patients with schizophrenia and compare them with healthy controls., Material and Methods: This work has been carried out on 188 cases, out of which 88 schizophrenia patients (56 men and 32 women) met the diagnostic criteria according to DSM-5 for schizophrenia and 100 healthy controls (50 men and 50 women). The 10 parameters have been used to evaluate IFS on magnetic resonance imaging (MRI) scans., Results: The parameters showing statistically significant differences were higher in favor of the individual with schizophrenia. Except for the bifrontal index and Evan's index, most parameters (the bicaudate index, the fourth ventricle width, the fourth ventricle index, the maximum width of the anterior interhemispheric fissure, the maximum width of the right frontal subarachnoid space, the maximum width of the left frontal subarachnoid space, the maximum width of the right Sylvian fissure, and the maximum width of the left Sylvian fissure) were obtained statistically highly significant differences between the examined and control groups., Conclusions: In schizophrenia, it is more practical to evaluate brain atrophy using some parameters, especially the width of the Sylvian fissure and the bicaudate index., (Copyright © 2024 Copyright: © 2024 Neurology India, Neurological Society of India.)

The perioptic space comprises the subarachnoid space [SAS] of the optic nerve communicating with the SAS of the central nervous system. Pressure variations in the SAS of the central nervous system can be transmitted to the optic papilla through the perioptic space. Variations in the diameter of the perioptic space serve as an important indicator for select intracranial pathologies in the pediatric population. Though the perioptic space can be evaluated using various imaging modalities, MRI is considered highly effective due to its superior soft tissue resolution. With advancement in MR imaging techniques, high-resolution images of the orbits can provide improved visualization of the perioptic space. It is imperative for the pediatric radiologist to routinely assess the perioptic space on brain and orbit MR imaging, as it can prompt exploration for additional features associated with select intracranial pathologies, thus improving diagnostic accuracy. This article reviews basic anatomy of the perioptic space, current understanding of the CSF dynamics between the perioptic space and central nervous system SAS, various imaging modalities utilized in the assessment of the perioptic space, MRI sequences and the optimal parameters of specific sequences, normal appearance of the perioptic space on MR imaging, and various common pediatric pathologies which cause alteration in the perioptic space., Competing Interests: Declaration of competing interest No funding was received to assist with the preparation of this manuscript. The authors have no relevant financial or non-financial interests to disclose., (Published by Elsevier Inc.)

Objective: Several radiological markers have been linked to clinical improvement after shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). However, iNPH has no pathognomonic feature, and patients are still diagnosed as probable, possible, or unlikely cases based on clinical symptoms, imaging findings, and invasive supplementary tests. The predictive value of the disproportionately enlarged subarachnoid space hydrocephalus (DESH) score is not yet conclusively determined, but it might offer a more accurate diagnostic method. The aim of the present retrospective cohort study was to validate the predictive power of the DESH score for clinical improvement after shunt surgery in iNPH patients., Methods: We retrospectively obtained presurgical MRI and/or CT scans from 71 patients with iNPH who underwent ventriculoperitoneal shunt surgery. Radiological images were evaluated for Evans index (EI), corpus callosal angle (CA), tight high convexity (THC), Sylvian fissure dilation, and focal sulci dilation. These markers were aggregated to determine the DESH score. Patient journal entries were used to subjectively determine the extent of improvement in gait function, urinary incontinence, and/or cognition as a measure of shunt surgery response., Results: Multiple logistic regression analysis, controlling for age and sex (α = 0.05), showed that DESH score was significantly correlated (OR 1.77) with subjective shunt-surgery response at a minimum of 1-month follow-up. Patients with higher DESH scores were more likely to have a favorable response to shunt surgery., Conclusion: Aggregating radiological markers into the DESH score is useful for predicting shunt responders among iNPH patients and can aid the selection of patients for surgery. These findings provide further support for the DESH score as a diagnostic tool for iNPH., Competing Interests: Declaration of Competing Interest We, the authors, declare no conflicts of interests., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Ultrasound (US) is often the first method used to look for brain or cerebrospinal fluid (CSF) space pathologies. Knowledge of normal CSF width values is essential. Most of the available US normative values were established over 20 years ago, were obtained with older equipment, and cover only part of the age spectrum that can be examined by cranial US. This prospective study aimed to determine the normative values of the widths of the subarachnoid and internal CSF spaces (craniocortical, minimal and maximal interhemispheric, interventricular, and frontal horn) for high-resolution linear US probes in neurologically healthy infants and children aged 0-19 months and assess whether subdural fluid collections can be delineated., Methods: Two radiologists measured the width of the CSF spaces with a conventional linear probe and an ultralight hockey-stick probe in neurologically healthy children not referred for cranial or spinal US., Results: This study included 359 neurologically healthy children (n boys  = 178, 49.6%; n girls  = 181, 50.4%) with a median age of 46.0 days and a range of 1-599 days. We constructed prediction plots, including the 5th, 50th, and 95th percentiles, and an interactive spreadsheet to calculate normative values for individual patients. The measurements of the two probes and the left and right sides did not differ, eliminating the need for separate normative values. No subdural fluid collection was detected., Conclusion: Normative values for the widths of the subarachnoid space and the internal CSF spaces are useful for evaluating intracranial pathology, especially when determining whether an increase in the subarachnoid space width is abnormal., (© 2024. The Author(s).)

Objective: This study compared the clinical therapeutic efficacy of syringo-subarachnoid shunt placement with direct tube and T-tube via the dorsal root entry zone (DREZ) approach for treatment of eccentric syringomyelia., Methods: A retrospective study was performed of 41 patients with idiopathic or secondary eccentric syringomyelia from November 2011 to December 2022. Syringo-subarachnoid shunt placement with direct tube or T-tube via the DREZ approach was performed. The modified Japanese Orthopaedic Association low back pain scale was used to investigate the severity of clinical symptoms. Magnetic resonance imaging was used to investigate therapeutic efficacy（reduction of the cavity volume by >10% was considered an improvement and 50% was considered a significant improvement)., Results: Incision length of the spinal cortex in the direct tube group was shorter than in the T-tube group (3.10 ± 0.28 cm vs. 5.03 ± 0.19 cm), with a significant difference between the 2 groups (t = -52.56, P < 0.001). Modified Japanese Orthopaedic Association score 3 months postoperatively was significantly better than the preoperative score in both the direct tube group（t = 40.954, P < 0.001） and the T-tube group（t = 24.769, P < 0.001）. Statistical comparison revealed there was no difference in imaging improvement between the direct tube group and T-tube group 3 months (χ 2  = 0.20, P = 0.655) and 12 months (χ 2  = 0.21, P = 0.647) postoperatively., Conclusions: Syringo-subarachnoid shunt placement with direct tube via the DREZ approach for treatment of eccentric syringomyelia is safer than with T-tube via the DREZ approach due to smaller incision length and less of a space-occupying effect with same therapeutic efficacy., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The human subarachnoid space harbors the cerebrospinal fluid, which flows within a landscape of blood vessels and trabeculae. Functional implications of subarachnoid space anatomy remain far less understood. This study of 75 patients utilizes a cerebrospinal fluid tracer (gadobutrol) and consecutive magnetic resonance imaging to investigate features of early (i.e. within 2-3 h after injection) tracer propagation within the subarachnoid space. There is a time-dependent perivascular pattern of enrichment antegrade along the major cerebral artery trunks; the anterior-, middle-, and posterior cerebral arteries. The correlation between time of first enrichment around arteries and early enrichment in nearby cerebral cortex is significant. These observations suggest the existence of a compartmentalized subarachnoid space, where perivascular ensheathment of arteries facilitates antegrade tracer passage towards brain tissue. Periarterial transport is impaired in subjects with reduced intracranial pressure-volume reserve capacity and in idiopathic normal pressure hydrocephalus patients who also show increased perivascular space size., (© 2024. The Author(s).)

The fluid-attenuated inversion recovery (FLAIR) sequence forms part of the vast majority of current diagnostic protocols for brain MRI. This sequence enables the suppression of the signal from cerebrospinal fluid, facilitating the detection of disease involving the subarachnoid space. The causes of hyperintensity in the arachnoid space in this sequence can be divided into two main categories: hyperintensity due to disease and hyperintensity due to artifacts. Hyperintensity due to tumors, inflammation, vascular disease, or hypercellularity of the cerebrospinal fluid or hematic contents is well known. However, numerous other non-pathological conditions, mainly due to artifacts, that are also associated with this finding are a potential source of diagnostic errors., (Copyright © 2022 SERAM. Published by Elsevier España, S.L.U. All rights reserved.)

Background: Idiopatic normal pressure hydrocephalus (iNPH) is a progressive neurologic syndrome featured by the triad of gait disturbance, mental deterioration and urinary incontinence, associated with ventriculomegaly and normal cerebrospinal fluid (CSF) pressure. The clinical presentation may be atypical or incomplete, or mimicked by other diseases, so conventional neuroradiologic imaging plays an important role in defining this pathology. iNPH pathophysiologic mechanisms have not yet been fully elucidated, although several studies have demonstrated the involvement of the glymphatic system, a highly organized fluid transport system, the malfunction of which is involved in the pathogenesis of several disorders including normotensive hydrocephalus., Methods: Recent studies have shown how crucial in the diagnosis of this pathology is the definition of morphologic biomarkers, such as ventricular enlargement disproportionate to cerebral atrophy and associated ballooning of frontal horns; periventricular hyperintensities; and corpus callosum thinning and elevation, with callosal angle <90 degrees., Results: Another interesting feature that is becoming a well-recognized factor to look for and useful for the diagnosis of iNPH is disproportionately enlarged subarachnoid space hydrocephalus, which includes enlarged ventricles, tight high-convexity and medial surface subarachnoid spaces, and expanded Sylvian fissures. A correct choice of MRI sequences is important for a proper characterization identification of others diseases that may underlie this pathology. Magnetic resonance imaging allows us to evaluate CSF flow, enabling us to define qualitative and quantitative parameters necessary for the purpose of accurate iNPH diagnosis., Conclusions: iNPH can represent a real diagnostic challenge; a proper correlation among clinical features, traditional MRI, and CSF dynamics analysis can lead to a correct diagnosis., (Copyright © 2023. Published by Elsevier Inc.)

BACKGROUNDIntrathecal injection is an attractive route through which drugs can be administered and directed to the spinal cord, restricted by the blood-spinal cord barrier. However, in vivo data on the distribution of cerebrospinal fluid (CSF) substances in the human spinal cord are lacking. We conducted this study to assess the enrichment of a CSF tracer in the upper cervical spinal cord and the brain stem.METHODSAfter lumbar intrathecal injection of a magnetic resonance imaging (MRI) contrast agent, gadobutrol, repeated blood samples and MRI of the upper cervical spinal cord, brain stem, and adjacent subarachnoid spaces (SAS) were obtained through 48 hours. The MRI scans were then analyzed for tracer distribution in the different regions and correlated to age, disease, and amounts of tracer in the blood to determine CSF-to-blood clearance.RESULTSThe study included 26 reference individuals and 35 patients with the dementia subtype idiopathic normal pressure hydrocephalus (iNPH). The tracer enriched all analyzed regions. Moreover, tracer enrichment in parenchyma was associated with tracer enrichment in the adjacent SAS and with CSF-to-blood clearance. Clearance from the CSF was delayed in patients with iNPH compared with younger reference patients.CONCLUSIONA CSF tracer substance administered to the lumbar thecal sac can access the parenchyma of the upper cervical spinal cord and brain stem. Since CSF-to-blood clearance is highly individual and is associated with tracer level in CSF, clearance assessment may be used to tailor intrathecal treatment regimes.FUNDINGSouth-Eastern Norway Regional Health and Østfold Hospital Trust supported the research and publication of this work.

Purpose: To quantify the T 1 and T 2 values of CSF in the subarachnoid space (SAS) at 3 T and interpret them in the context of water exchange between CSF and brain tissues., Methods: CSF T 1 was measured using inversion recovery, and CSF T 2 was assessed using T 2 -preparation. T 1 and T 2 values in the SAS were compared with those in the frontal horns of lateral ventricles, which have less brain-CSF exchange. Phantom experiments were performed to examine whether there were spatial variations in T 1 and T 2 that were unrelated to brain-CSF exchange. Simulations were conducted to investigate the relationship between the brain-CSF exchange rate and the apparent T 1 and T 2 values of SAS CSF., Results: The CSF T 1 and T 2 values were 4308.7 ± 146.9 ms and 1885.5 ± 67.9 ms, respectively, in the SAS and were 4454.0 ± 187.9 ms and 2372.9 ± 72.0 ms in the frontal horns. The SAS CSF had shorter T 1 (p = 0.006) and T 2 (p < 0.0001) than CSF in the frontal horns. Phantom experiments showed negligible (< 6 ms for T 1 ; < 1 ms for T 2 ) spatial variations in T 1 and T 2 , suggesting that the T 1 and T 2 differences between SAS and frontal horns were largely attributed to physiological reasons. Simulations revealed that faster brain-CSF exchange rates lead to shorter apparent T 1 and T 2 of SAS CSF. However, the experimentally observed T 2 difference between SAS and frontal horns was greater than that attributable to typical exchange effect, suggesting that the T 2 shortening in SAS may reflect a combined effect of exchange and deoxyhemoglobin susceptibility., Conclusion: Quantification of SAS CSF relaxation times may be useful to assess the brain-CSF exchange., (© 2023 International Society for Magnetic Resonance in Medicine.)

Purpose: The purpose of this study was to examine the differences of optic nerve subarachnoid space (ONSAS) volume in patients with normal tension glaucoma (NTG) and healthy controls in different body positions., Methods: Eight patients with NTG and seven healthy controls underwent magnetic resonance imaging (MRI) examinations in head up tilt (HUT) +11 degrees and head down tilt (HDT) -5 degrees positions according to a randomized protocol determining the starting position. The ONSAS volume in both body positions was measured and compared between the two groups. The results were analyzed using a generalized linear model., Results: Between HDT and HUT, the postural ONSAS volume change was dependent on starting position (P < 0.001) and group (P = 0.003, NTG versus healthy). A subgroup analysis of those that were randomized to HUT examination first, coming directly from an upright position, showed that the patients with NTG had significantly larger positional ONSAS volume changes compared to the healthy controls; 121 ± 22 µL vs. 65 ± 37 µL (P = 0.049). Analysis of the ONSAS volume distribution showed different profiles for patients with NTG and healthy controls., Conclusions: There was a significant difference in ONSAS volume change between patients with NTG and healthy subjects when subjected to posture changes, specifically when going from upright to head-down posture. This indicates that patients with NTG had been exposed to a lower ONSAS pressure when they came from the upright posture, which suggests an increased translaminar pressure difference in upright position. This may support the theory that NTG has a dysfunction in an occlusion mechanism of the optic nerve sheath that could cause abnormally negative ONSAS pressures in upright posture.

Introduction: The subarachnoid space (SAS) is a potential space surrounding the brain where the cerebrospinal fluid (CSF) flows. Previous work demonstrated how the SAS width changes during pregnancy and measured the normal values per gestational week., Objectives: Studying the ratio between the fetal brain volume (STV) and the SAS width (SS ratio), as measured via fetal magnetic resonance imaging (MRI) in different fetal pathologies - macrocephaly and microcephaly, and studying the correlation between this ratio and the gestational week., Methods: A retrospective study was conducted on 77 fetuses that underwent fetal MRI scans during gestational weeks 29-37, in three groups: 23 normocephaly, 27 macrocephaly, and 27 microcephaly. SAS width was measured in 10 points via fetal MRI scans, and a ratio was calculated between the width and STV., Results: The SS ratio is largest in microcephaly group and smallest in normocephaly group, with the macrocephaly group between them. All comparisons were statistically significant except between the macrocephaly and normocephaly groups. There was a strong positive correlation between SS ratio and week of gestation., Conclusions: The SS ratio is statistically different between normocephalic fetuses and fetuses with macrocephaly or microcephaly. From week 29 this ratio enlarges with gestational age., Discussion: The SAS affects the fetal head circumference, an important parameter of fetal growth, thus we decided to study the SS ratio in pathologies of the head circumference. Previous work demonstrated how the STV and the SAS width expand starting at a specific gestational age, thus the gestational week also affects the SS ratio. Summary: The SS ratio is affected by pathologies of the fetal head circumference and by gestational age.

Schimmelpenning-Feuerstein-Mims syndrome is a rare disorder generally characterised by a craniofacial nevus with multisystemic presentations. Our patient, an infant, was brought to the emergency department in a postictal state following a first seizure episode. A physical examination showed a solitary dark brown, well-demarcated verrucous plaque extending from the patient's left temporal region to the left mandible without crossing the midline. Epibulbar choristomas were present on the ipsilateral side of the craniofacial lesion. Neuroimaging showed benign enlargement of the subarachnoid space. Due to the known risk of seizures associated with this condition, the patient was started on levetiracetam and showed adequate compliance. We present this as the first reported case of Schimmelpenning-Feuerstein-Mims syndrome with benign enlargement of the subarachnoid space in an infant presenting with seizures to emphasise the value of collaboration among multidisciplinary professionals to improve the quality of care for such patients., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: We investigated the impact of pregestational and gestational diabetes mellitus (PGDM and GDM) on the development of fetal intracranial structures and spaces., Methods: This prospective cross-sectional study involved singleton pregnancies between 20 and 32 weeks of gestation. The study comprised a control group (n = 65) of healthy pregnant women without diabetes mellitus (DM); a PGDM group (n = 43) of pregnant women having type 2 DM in a controlled diabetic state; and a GDM group (n = 26) of pregnant women with GDM diagnosed with 2-h 75-g oral glucose tolerance test and received intervention to reduce the diabetic impact on fetus. During neurosonographic evaluation, the simultaneous measurements of corpus callosum (CC) width and depth in the midsagittal image; and lateral craniocortical and posterior craniocortical widths of the subarachnoid space and insular and parieto-occipital fissure depths in the axial image were performed. Before statistical analysis, these values were carefully adjusted for the occipitofrontal diameter., Results: The DM groups displayed substantially higher frequencies of family history of DM and obstetric history of GDM compared to the control group (p < 0.05). Regarding the neurosonographic parameters, the CC length and insular and parieto-occipital fissure depths were significantly increased in the GDM group but not in the PGDM group (p < 0.05). No significant difference was found among the study groups regarding other neurosonographic parameters (p > 0.05)., Conclusion: The results of neurosonographical evaluation of fetal brain structures and spaces reveal that diabetic impact may not be seen in the presence of PGDM, especially in pregnant women receiving prenatal interventions to reduce or avoid diabetic adverse effects on fetal brain development. The effect of GDM on neurosonographically assessed fetal brain development should be evaluated in further studies with subjects matched for gestational weeks and antenatal care conditions., (© 2023 Wiley Periodicals LLC.)

The pathophysiology of idiopathic intracranial hypertension (IIH) and idiopathic normal-pressure hydrocephalus (iNPH) differs in terms of cerebrospinal fluid (CSF) pressure and imaging-related characteristics. A 51-year-old man presented with optic nerve papillary edema, visual disturbance, bilateral abducens nerve palsy, and a wide-based gait. Imaging showed characteristic findings of IIH and disproportionately enlarged subarachnoid space hydrocephalus (DESH) - characteristic of iNPH. A CSF examination revealed marked CSF hypertension. IIH with iNPH-like imaging features (DESH) was diagnosed, and ventriculoperitoneal shunt surgery was performed. Postoperatively, the visual acuity and visual field improved. This report also describes the distinct and overlapping pathophysiological mechanisms of IIH and iNPH.

Background: Surgical treatment of syringomyelia is directed at the reconstruction of the subarachnoid space and restoration normal cerebrospinal fluid flow. Direct intervention on the syrinx is a rescue procedure and should be offered to patients with refractory syringomyelia., Methods: We provide an overview on indications and technique of syringopleural shunt (SPS). The procedure involves the connection of syrinx with the pleural space using a lumboperitoneal shunt. The occurrence of a negative pressure inside the pleural compartment offers an appropriate gradient for drainage from the syrinx., Conclusions: The SPS allows for a safe and effective treatment of persistent syringomyelia when management of the underlying cause does not yield substantial improvement., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background: The etiology of enlarged subarachnoid spaces of infancy is unknown; however, there is radiologic similarity with normal pressure hydrocephalus. Adults with normal pressure hydrocephalus have been shown to have altered cerebrospinal (CSF) flow through the cerebral aqueduct., Objective: To explore potential similarity between enlarged subarachnoid spaces of infancy and normal pressure hydrocephalus, we compared MRI-measured CSF flow through the cerebral aqueduct in infants with enlarged subarachnoid spaces of infancy to infants with normal brain MRIs., Materials and Methods: This was an IRB approved retrospective study. Clinical brain MRI examinations including axial T2 imaging and phase contrast through the aqueduct were reviewed for infants with enlarged subarachnoid spaces of infancy and for infants with a qualitatively normal brain MRI. The brain and CSF volumes were segmented using a semi-automatic technique (Analyze 12.0) and CSF flow parameters were measured (cvi42, 5.14). All data was assessed for significant differences while controlling for age and sex using analysis of covariance (ANCOVA)., Results: Twenty-two patients with enlarged subarachnoid spaces (mean age 9.0 months, 19 males) and 15 patients with normal brain MRI (mean age 18.9 months, 8 females) were included. Volumes of the subarachnoid space (P < 0.001), lateral (P < 0.001), and third ventricles (P < 0.001) were significantly larger in infants with enlarged subarachnoid spaces of infancy. Aqueductal stroke volume significantly increased with age (P = 0.005), regardless of group., Conclusion: CSF volumes were significantly larger in infants with enlarged subarachnoid spaces of infancy versus infants with a normal MRI; however, there was no significant difference in CSF flow parameters between the two groups., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

We report the case of 74-year-old patient suspected of post-traumatic external hydrocephalus (EH) following a mild traumatic brain injury with a progressive neurological decline and a concomitant enlargement of subarachnoid spaces without ventriculomegaly on CT scan. A lumbar puncture revealed raised ICP and a careful CSF withdrawal was performed, resulting in an immediate neurological improvement, confirming the diagnosis of EH. During the 20-month follow-up, the patient presented progressive signs of normal pressure hydrocephalus (NPH): gait and cognitive decline, ventriculomegaly and the lumbar infusion study confirmed disturbed CSF dynamics. The patient underwent a ventriculoperitoneal shunt surgery, resulting in a long-lasting improvement.

Objective: The presence of tightened sulci in the high-convexities (THC) is a key morphological feature for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH), but the exact localization of THC has yet to be defined. The purpose of this study was to define THC and compare its volume, percentage, and index between iNPH patients and healthy controls., Methods: According to the THC definition, the high-convexity part of the subarachnoid space was segmented and measured the volume and percentage from the 3D T1-weighted and T2-weighted magnetic resonance images in 43 patients with iNPH and 138 healthy controls., Results: THC was defined as a decrease in the high-convexity part of the subarachnoid space located above the body of the lateral ventricles, with anterior end on the coronal plane perpendicular to the anterior commissure-posterior commissure (AC-PC) line passing through the front edge of the genu of corpus callosum, the posterior end in the bilateral posterior parts of the callosomarginal sulci, and the lateral end at 3 cm from the midline on the coronal plane perpendicular to the AC-PC line passing through the midpoint between AC and PC. Compared to the volume and volume percentage, the high-convexity part of the subarachnoid space volume per ventricular volume ratio < 0.6 was the most detectable index of THC on both 3D T1-weighted and T2-weighted magnetic resonance images., Conclusions: To improve the diagnostic accuracy of iNPH, the definition of THC was clarified, and high-convexity part of the subarachnoid space volume per ventricular volume ratio <0.6 proposed as the best index for THC detection in this study., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The cisterna magna has been defined as the space between the inferior margin of the cerebellar vermis to the level of the foramen magnum, while an enlarged dorsal subarachnoid space at the occipito-cervical junction extending from the foramen magnum to the upper border of the axis (C2) is still ignored. Recently, the myodural bridge complex is proved to drive the cerebral spinal fluid flowing via this region, we therefore introduce the "occipito-atlantal cistern (OAC)" to better describe the subarachnoid space and provide a detailed rationale. The present study utilized several methods, including MRI, gross anatomical dissection, P45 sheet plastination, and three-dimensional visualization. OAC was observed to be an enlarge subarachnoid space, extending from the foramen magnum to the level of the C2. In the median sagittal plane, OAC was a funnel shape and its anteroposterior dimensions were 15.92 ± 4.20 mm at the level of the C0, 4.49 ± 1.25 mm at the level of the posterior arch of the C1, and 2.88 ± 0.77 mm at the level of the arch of the C2, respectively. In the median sagittal plane, the spino-dural angle of the OAC was calculated to be 35.10 ± 6.91°, and the area of OAC was calculated to be 232.28 ± 71.02 mm 2 . The present study provides OAC is a subarachnoid space independent from the cisterna magna. Because of its distinctive anatomy, as well as theoretical and clinical significance, OAC deserves its own name., (© 2023. The Author(s).)

Background Subarachnoid block is one of the commonly used techniques of regional anesthesia and accurate placement of spinal needle is crucial. A conventional spinal needle may be too long for a lean patient or too short in obese patients leading to multiple attempts, inadvertent nerve injuries and patient discomfort. So a pre-procedural estimation of the skin to subarachnoid space depth may be beneficial. Objective To estimate the skin to subarachnoid space depth using ultrasound and correlate it with the length of spinal needle to be inserted during subarachnoid block. Method This was a prospective, observational study conducted at Bir Hospital, Kathmandu in patients undergoing elective surgeries under subarachnoid block. A pre-procedural ultrasound of lumbo-sacral spine using 2-5 Hz curvilinear probe was done to measure skin to subarachnoid space depth (SSD) at the level of L3-L4 interspace. Then under all aseptic precautions, subarachnoid block was performed and the length of spinal needle outside the skin was measured and that length was subtracted from the standard length of needle to get the inserted length of spinal needle. These two measurements were compared. Result In the fifty patients included in the study, ultrasound estimated skin to subarachnoid space depth was found to be 4.24 ± 0.48 cm and the inserted length of spinal needle was 4.24 ± 0.46 cm. A significant correlation r=0.96 (p < 0.05) was found between the two measurements in the study population. Conclusion Ultrasound estimated skin to subarachnoid depth in the study population was found to be 4.24 ± 0.48 cm which correlated with the inserted length of spinal needle. So, use of ultrasound can be very helpful in performing subarachnoid block.

Virchow Robin spaces are normally found pial-lined perivascular spaces traversing from subarachnoid space to the brain parenchyma. Giant dilated Virchow robin spaces (dVRS) are rare. They do not require any surgical intervention unless they are causing symptoms. Here we report a young boy with an incidentally detected giant dVRS in brainstem which was referred for surgery with an initial impression of glioma. Knowledge about such an entity is important to prevent mismanagement.

Background and Purpose: The fetal subarachnoid space size serves as an indicator of normal brain development. The subarachnoid space is commonly measured by an ultrasound examination. Introduction of MR imaging for fetal brain evaluation enables standardization of MR imaging-driven subarachnoid space parameters for a more accurate evaluation. This study aimed to determine the normal range of MR imaging-derived subarachnoid space size in fetuses according to gestational age., Materials and Methods: A cross-sectional study based on a retrospective assessment of randomly selected brain MR images of apparently healthy fetuses performed between 2012 and 2020 at a large tertiary medical center was performed. Demographic data were collected from the mothers' medical records. Subarachnoid space size was measured at 10 reference points using the axial and coronal planes. Only MR imaging scans obtained between weeks 28 and 37 of pregnancy were included. Scans with low-quality images, multiple pregnancy, and cases with intracranial pathologic findings were excluded., Results: Overall, 214 apparently healthy fetuses were included (mean maternal age, 31.2 [SD, 5.4] years). Good interobserver and intraobserver agreement was observed (intraclass correlation coefficient > 0.75 for all except 1 parameter). For each gestational week, the 3rd, 15th, 50th, 85th, and 97th percentiles of each subarachnoid space measurement were described., Conclusions: MR imaging-derived subarachnoid space values at a specific gestational age provide reproducible measurements, probably due to the high resolution of MR imaging and adherence to the true radiologic planes. Normal values for brain MR imaging could provide valuable reference information for assessing brain development, thus being an important tool in the decision-making process of both clinicians and parents., (© 2023 by American Journal of Neuroradiology.)

In infants without a history of trauma, subdural haemorrhages should raise the concern for an abusive head injury, particularly when they are associated with bridging vein clotting/rupture or with septations. However, non-haemorrhagic, fluid-appearing subdural collections (also called hygromas) may also be the result of abuse. Subdural collections have also been uncommonly observed in patients with benign enlargement of the subarachnoid spaces (BESS) and a few large-scale studies accurately investigate the incidence and the significance. Currently, there is a wide variation of practices in children with BESS and subdural collections. Due to the social risks associated with abuse evaluation and the perceived risk of radiation exposure, there might be a reluctance to fully evaluate these children in some centres. The diagnosis of physical abuse cannot be substantiated nor safely excluded in infants with BESS and subdural collection(s), without investigation for concomitant traumatic findings. The exact prevalence of occult injuries and abuse in these infants is unknown. In macrocephalic infants with subdural collections and imaging features of BESS, thorough investigations for abuse are warranted and paediatricians should consider performing full skeletal surveys even when fundoscopy, social work consult, and detailed clinical evaluation are unremarkable., (© 2023. The Author(s).)

Anatomic MRI, MRI flow studies, and intraoperative ultrasonography demonstrate that the Chiari I malformation obstructs CSF pathways at the foramen magnum and prevents normal CSF movement through the foramen magnum. Impaired CSF displacement across the foramen magnum during the cardiac cycle increases pulsatile hindbrain motion, pressure transmission to the spinal subarachnoid space, and the amplitude of CSF subarachnoid pressure waves driving CSF into the spinal cord. Central canal septations in adults prevent syrinx formation by CSF directly transmitting its pressure wave from the fourth ventricle to the central canal., Competing Interests: Disclosure The author has nothing to disclose., (Published by Elsevier Inc.)

Background: The hyperintense acute reperfusion marker (HARM) describes a phenomenon with a hyperintense signal in the subarachnoid space in Fluid-Attenuated Inversion Recovery (FLAIR) magnetic resonance imaging (MRI) sequences, presumably based on blood-brain barrier breakdown in acute stroke with reperfusion. However, this imaging phenomenon was described in other medical conditions., Aim: Determination of the prevalence and associated clinical findings of this phenomenon in a large sample of patients with different neurological conditions., Methods: This is retrospective, single-center, observational study of 23,948 cerebral MRIs acquired in a Neurological University Clinic over 5 years. The prevalence of HARM, the underlying diagnosis, and damage pattern were examined by chart analysis; MRI was analyzed regarding the type of acute lesions, extent of microangiopathic lesions, and whether gadolinium-based contrast agent (GBCA) was given., Results: Among the MRI data, 84 images (0.35%) from 61 patients were HARM-positive without a subarachnoid signal abnormality in any other sequence. Etiologies were heterogeneous; 35 patients had a cerebrovascular disease (CVD; 19 patients received recanalization therapy), 12 patients had an inflammatory central nervous system (CNS) disease and 14 patients had epilepsy. GBCA was applied to 64% of the patients., Conclusion: HARM was a rare radiological finding in a range of different neurological pathologies, not limited to stroke, or to previous reperfusion therapy and was not dependent on previous GBCA administration. Our data suggest that the term is too narrow in terms of the concepts of the underlying pathology. We propose to use the term FLA IR S ubarachnoid H yperintensity ("FLASH") phenomenon which might better reflect the observation that the radiological sign can be associated with a variety of central neurological conditions without a straightforward association with therapy.

Traumatic subarachnoid-pleural fistula is an uncommon occurrence. We present a case of a patient sustaining a subarachnoid-pleural fistula after a gunshot wound to the neck, which ultimately resulted in substantial pneumocephalus. The patient underwent successful operative repair of the fistula with notable improvement and resolution of pneumocephalus., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Impaired cerebrospinal fluid (CSF) dynamics may contribute to the pathophysiology of neurodegenerative diseases, and play a crucial role in brain health in older people; nonetheless, such age-related changes have not been well elucidated. Disproportionately enlarged subarachnoid-space hydrocephalus (DESH) is a neuroimaging phenotype of idiopathic normal-pressure hydrocephalus, originating from impaired CSF dynamics, and closely associated with aging. This study aimed to investigate the pathophysiology of DESH and determine age-related changes in CSF dynamics., Methods: Using magnetic resonance imaging, we investigated the pathophysiology of DESH by quantitatively evaluating the volumes of DESH-related regions (ventricles [VS], Sylvian fissure [SF], and subarachnoid spaces at high convexity and midline [SHM]) and brain parenchyma in community-dwelling individuals aged  ≥ 65 years. DESH-related regions were assessed using a visual rating scale, and volumes measured using voxel-based morphometry. Brain parenchyma volumes were measured using FreeSurfer software., Results: Data from 1,356 individuals were analyzed, and 25 (1.8%) individuals had DESH. Regarding the relationships between the volume of each CSF space and age, VS and SF volumes increased with age, whereas SHM volume did not increase. VS and SF volumes increased as the whole brain volume decreased, whereas SHM volume did not increase even if the whole brain volume decreased; that is, SHM did not expand even if brain atrophy progressed. Moreover, lower Mini-Mental State Examination scores were significantly associated with lower SHM volume and higher VS volume. These associations remained significant even when individuals with DESH were excluded., Conclusions: This study showed that the volume of high-convexity and medial subarachnoid spaces did not expand and tended to decrease with age; the human brain continuously progresses toward a "DESH-like" morphology with aging in community-dwelling older persons (i.e., DESH might be an "accelerated aging stage" rather than an "age-related disorder"). Our results indicated that brain atrophy may be associated with the development of "DESH-like" morphology. In addition, this morphological change, as well as brain atrophy, is an important condition associated with cognitive decline in older adults. Our findings highlight the importance of investigating the aging process of CSF dynamics in the human brain to preserve brain health in older people., (© 2022. The Author(s).)

Objective: The aims of the study were to measure the cerebrospinal fluid (CSF) volumes in the lateral ventricle, high-convexity subarachnoid space, and Sylvian fissure region in patients with idiopathic normal-pressure hydrocephalus (INPH) and Alzheimer's disease (AD), and to evaluate differences in these volumes between INPH and AD groups and healthy controls., Methods: Forty-nine INPH patients, 59 AD patients, and 26 healthy controls were imaged with automated three-dimensional volumetric MRI., Results: INPH patients had larger lateral ventricles and CSF spaces of the Sylvian fissure region and smaller high-convexity subarachnoid spaces than other groups, and AD patients had larger lateral ventricles and CSF spaces of the Sylvian fissure region than the control group. The INPH group showed a negative correlation between lateral ventricle and high-convexity subarachnoid space volumes, while the AD group showed a positive correlation between lateral ventricle volume and volume for CSF spaces of the Sylvian fissure region. The ratio of lateral ventricle to high-convexity subarachnoid space volumes yielded an area under the curve of 0.990, differentiating INPH from AD., Conclusions: Associations between CSF volumes suggest that there might be different mechanisms between INPH and AD to explain their respective lateral ventricular dilations. The ratio of lateral ventricle to high-convexity subarachnoid space volumes distinguishes INPH from AD with good diagnostic sensitivity and specificity. We propose to refer to this ratio as the VOSS (ventricle over subarachnoid space) index., (© 2022. The Author(s).)

Background and Purpose: Forced respirations reportedly have an effect on CSF movement in the spinal canal. We studied respiratory-related CSF motion during normal respiration., Materials and Methods: Six healthy subjects breathed at their normal rate with a visual guide to ensure an unchanging rhythm. Respiratory-gated phase-contrast MR flow images were acquired at 5 selected axial planes along the spine. At each spinal level, we computed the flow rate voxelwise in the spinal canal, together with the associated stroke volume. From these data, we computed the periodic volume changes of spinal segments. A phantom was used to quantify the effect of respiration-related magnetic susceptibility changes on the velocity data measured., Results: At each level, CSF moved cephalad during inhalation and caudad during expiration. While the general pattern of fluid movement was the same in the 6 subjects, the flow rates, stroke volumes, and spine segment volume changes varied among subjects. Peak flow rates ranged from 0.60 to 1.59 mL/s in the cervical region, 0.46 to 3.17 mL/s in the thoracic region, and 0.75 to 3.64 mL/s in the lumbar region. The differences in flow rates along the canal yielded cyclic volume variations of spine segments that were largest in the lumbar spine, ranging from 0.76 to 3.07 mL among subjects. In the phantom study, flow velocities oscillated periodically during the respiratory cycle by up to 0.02 cm/s or 0.5%., Conclusions: Respiratory-gated measurements of the CSF motion in the spinal canal showed cyclic oscillatory movements of spinal fluid correlated to the breathing pattern., (© 2022 by American Journal of Neuroradiology.)

Objective: Benign Enlargement of the Subarachnoid Spaces in Infancy (BESSI) is a common finding during workup for progressive macrocephaly. BESSI has been associated with slightly higher prevalence of subdural (SD) spaces and a risk for developing subdural hematoma. This study utilizes fast brain magnetic resonance imaging (MRI) to investigate the prevalence of visible SD spaces in BESSI., Methods: A retrospective review was performed for all pediatric patients who underwent brain MRI for macrocephaly. Patients with a diagnosis of BESSI were included in the study. A total of 109 patients met the inclusion criteria. Patient demographics were collected, and images were reviewed for size of subarachnoid, visible SD spaces, and ventricle size. Descriptive and inferential statistics were performed., Results: The average age was 8 ± 4.6 months, 64 (59%) were male, and 55 patients had no previous medical history (50%). Sixty-seven percent of all patients were identified to have visible SD spaces. Eleven patients had confirmed SD hematomas; 1 patient was deemed to have abusive head trauma. Visible SD spaces were associated with younger age (6.9 months). Thirty-one patients with visible SD spaces had follow-up MRI, with complete resolution by 33 months., Conclusions: BESSI is a self-limiting pathology that has been associated with visible SD spaces and potential risk for SD hemorrhages. We report a high prevalence of visible SD spaces within BESSI through utilization of fast brain MRI. These spaces may contribute to the higher rate of incidental subdural hematoma in this population., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides a detailed look at the anatomy of the intracranial portions of these structures with a particular focus on neuroimaging methods., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Massive migration of fat droplets in the ventricles and the subarachnoid space is a very rare sequel of spinal trauma. Owing to its rarity, knowledge about treatment and outcome remains limited. We report on the uncommon occurrence of massive subarachnoid and intraventricular fat dissemination in a 41-year-old man who suffered a complex sacropelvic fracture with spondylopelvic dissociation but who had no head injury. We show that early placement of an external ventricular drain with prolonged drainage for washout of the fat depots can prevent chronic hydrocephalus and subsequent shunt dependency., Competing Interests: Prof. Krauss is a consultant to Boston Scientific and Medtronic, outside the submitted work., (Thieme. All rights reserved.)

Purpose: The optic nerve (ON) is an extension of the central nervous system via the optic canal to the orbital cavity. It is accompanied by meninges whose arachnoid layer is in continuity with that of the chiasmatic cistern. This arachnoid layer is extended along the ON, delimiting a subarachnoid space (SAS) around the ON. Not all forms of chronic intracranial hypertension (ICH) present papilledema. The latter is sometimes asymmetric, unilateral, or absent. The radiological signs of optic nerve sheath (ONS) dilation, in magnetic resonance imaging, are inconsistent or difficult to interpret. The objective of this study was to analyze the anatomy, the constitution, and the variability of the SAS around the ON in its intraorbital segment to improve the understanding of the pathophysiologic mechanism of asymmetric or unilateral or absent papilledema in certain ICH., Methods: The study was carried out on nine cadaveric specimens. In four embalmed specimens, macroscopic analysis of the SAS of the ONS were performed, with description about density of the arachnoid trabecular meshwork in three distinct areas (bulbar segment, mid-orbital segment and the precanal segment). In three other embalmed specimens, after staining of SAS by methylene blue (MB), we performed macroscopic analysis of MB progression in the SAS of the ONS. Then, in two non-embalmed specimens, light and electron microscopy (EM) analysis were also done., Results: On the macroscopic level, after staining of SAS, we found in all cases that MB progressed on 16 mm average throughout the SAS of the ONS without reaching the papilla. In four embalmed specimens, in the SAS of the ONS, the density of the arachnoid trabecular meshwork showed inter-individual variability (100%) and intra-individual variability with bilateral variability (50%) and/or variability within the same ONS (88%). On the microscopic level, the arachnoid trabeculae of the ONS are composed of dense connective tissue. The EM perfectly depicted its composition which is mainly of collagen fibers of parallel orientation., Conclusion: The variability of the SAS around the ONS probably impacts the symmetrical or asymmetrical nature of papilledema in ICH., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background: The micro-architectonics of the subarachnoid space (SAS) remain partially understood and largely ignored, likely the result of the inability to image these structures in vivo. We explored transvascular imaging with high-frequency optical coherence tomography (HF-OCT) to interrogate the SAS., Methods: In vivo HF-OCT was performed in 10 dogs in both the posterior and anterior cerebral circulations. The conduit vessels used were the basilar, anterior spinal, and middle and anterior cerebral arteries through which the perivascular SAS was imaged. The HF-OCT imaging probe was introduced via a microcatheter and images were acquired using a contrast injection (3.5 mL/s) for blood clearance. Segmentation and three-dimensional rendering of HF-OCT images were performed to study the different configurations and porosity of the subarachnoid trabeculae (SAT) as a function of location., Results: Of 13 acquisitions, three were excluded due to suboptimal image quality. Analysis of 15 locations from seven animals was performed showing six distinct configurations of arachnoid structures in the posterior circulation and middle cerebral artery, ranging from minimal presence of SAT to dense networks and membranes. Different locations showed predilection for specific arachnoid morphologies. At the basilar bifurcation, a thick, fenestrated membrane had a unique morphology. SAT average thickness was 100 µm and did not vary significantly based on location. Similarly, the porosity of the SAT averaged 91% and showed low variability., Conclusion: We have demonstrated the feasibility to image the structures of the SAS with transvascular HF-OCT. Future studies are planned to further map the SAT to increase our understanding of their function and possible impact on neurovascular pathologies., Competing Interests: Competing interests: VA, ME, RMK, and AV declare no competing interest. GJU is an employee of Gentuity LLC. ASP: consultant for Medtronic Neurovascular and Stryker Neurovascular; research grants from Medtronic Neurovascular and Stryker Neurovascular. MJG has been a consultant on a fee-per-hour basis for Alembic LLC, Astrocyte Pharmaceuticals, BendIt Technologies, Cerenovus, Imperative Care, Jacob's Institute, Medtronic Neurovascular, Mivi Neurosciences, phenox GMbH, Q’Apel, Route 92 Medical, Stryker Neurovascular, Wallaby Medical; holds stock in Imperative Care, InNeuroCo, Galaxy Therapeutics and Neurogami; and has received research support from the Research support from the National Institutes of Health (NIH), the United States – Israel Binational Science Foundation, Anaconda, ApicBio, Arsenal Medical, Axovant, Balt, Cerenovus, Ceretrieve, CereVasc LLC, Cook Medical, Galaxy Therapeutics, Gentuity, Gilbert Foundation, Imperative Care, InNeuroCo, Insera, Jacob’s Institute, Magneto, Microvention, Medtronic Neurovascular, MIVI Neurosciences, Naglreiter MDDO, Neurogami, Philips Healthcare, Progressive Medical, Pulse Medical, Rapid Medical, Route 92 Medical, Stryker Neurovascular, Syntheon, ThrombX Medical, Wallaby Medical, the Wyss Institute and Xtract Medical. MJG is Associate Editor of Basic Science on the JNIS Editorial Board., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: Benign expansion of the subarachnoid spaces (BESS) is a condition seen in macrocephalic infants. BESS is associated with mild developmental delays which tend to resolve within a few years. It is accepted that patients with BESS are at increased risk of spontaneous subdural hematomas (SDHs), although the exact pathophysiology is not well understood. The prevalence of spontaneous SDH in BESS patients is poorly defined, with only a few large single-center series published. In this study the authors aimed to better define BESS prevalence and developmental outcomes through the longitudinal review of a large cohort of BESS patients., Methods: A large retrospective review was performed at a single institution from 1995 to 2020 for patients 2 years of age or younger with a diagnosis of BESS by neurology or neurosurgery and head circumference > 85th percentile. Demographic data, head circumference, presence of developmental delay, occurrence of SDH, and need for surgery were extracted from patient charts. The subarachnoid space (SAS) size was measured from the available MR images, and the sizes of those who did and did not develop SDH were compared., Results: Free text search revealed BESS mentioned within the medical records of 1410 of 2.6 million patients. After exclusion criteria, 480 patients remained eligible for the study. Thirty-two percent (n = 154) of patients were diagnosed with developmental delay, most commonly gross motor delay (53%). Gross motor delay resolved in 86% of patients at a mean age of 22.2 months. The prevalence of spontaneous SDH in this BESS population over a period of 25 years was 8.1%. There was no significant association between SAS size and SDH formation., Conclusions: This study represents results for one of the largest cohorts of patients with BESS at a single institution. Gross motor delay was the most common developmental delay diagnosed, and a majority of patients had resolution of their delay. These data support that children with BESS have a higher prevalence of SDH than the general pediatric population, although SAS size was not significantly associated with SDH development.

The anatomical routes for the clearance of cerebrospinal fluid (CSF) remain incompletely understood. However, recent evidence has given strong support for routes leading to lymphatic vessels. A current debate centers upon the routes through which CSF can access lymphatics, with evidence emerging for either direct routes to meningeal lymphatics or along cranial nerves to reach lymphatics outside the skull. Here, a method was established to infuse contrast agent into the ventricles using indwelling cannulae during imaging of mice at 2 and 12 months of age by magnetic resonance imaging. As expected, a substantial decline in overall CSF turnover was found with aging. Quantifications demonstrated that the bulk of the contrast agent flowed from the ventricles to the subarachnoid space in the basal cisterns. Comparatively little contrast agent signal was found at the dorsal aspect of the skull. The imaging dynamics from the 2 cohorts revealed that the contrast agent was cleared from the cranium through the cribriform plate to the nasopharyngeal lymphatics. On decalcified sections, we confirmed that fluorescently labeled ovalbumin drained through the cribriform plate and could be found within lymphatics surrounding the nasopharynx. In conclusion, routes leading to nasopharyngeal lymphatics appear to be a major efflux pathway for cranial CSF.

The arachnoid membranes are projections of connective tissue in the subarachnoid space that connect the arachnoid mater to the pia mater. These are underappreciated and largely unrecognized by most neuroradiologists despite being found to be increasingly important in the pathogenesis, imaging, and treatment of communicating hydrocephalus. This review aims to provide neuroradiologists with an overview of the history, embryology, histology, anatomy, and normal imaging appearance of these membranes, as well as some examples of their clinical importance., (© 2022 by American Journal of Neuroradiology.)