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Arachnoid villi

Roberto De Simone, Angelo Ranieri, Vincenzo Bonavita
Two critical functions for the control of intracranial fluids dynamics are carried on the venous side of the perfusion circuit: the first is the avoidance of cortical veins collapse during the physiological increases of cerebrospinal fluid (CSF) pressure in which they are immersed. The second, is the generation of an abrupt venous pressure drop at the confluence of the cortical veins with the dural sinuses that is required to allow a CSF outflow rate balanced with its production. There is evidence that both of these effects are ensured by a Starling resistor mechanism (a fluid dynamic construct that governs the flow in collapsible tubes exposed to variable external pressure) acting at the confluence of cortical veins in the dural sinus...
September 6, 2016: Panminerva Medica
Masaki Ueno, Yoichi Chiba, Ryuta Murakami, Koichi Matsumoto, Machi Kawauchi, Ryuji Fujihara
Blood-borne substances can invade into the extracellular spaces of the brain via endothelial cells in sites without the blood-brain barrier (BBB), and can travel through the interstitial fluid (ISF) of the brain parenchyma adjacent to non-BBB sites. It has been shown that cerebrospinal fluid (CSF) drains directly into the blood via the arachnoid villi and also into lymph nodes via the subarachnoid spaces of the brain, while ISF drains into the cervical lymph nodes through perivascular drainage pathways. In addition, the glymphatic pathway of fluids, characterized by para-arterial pathways, aquaporin4-dependent passage through astroglial cytoplasm, interstitial spaces, and paravenous routes, has been established...
April 2016: Brain Tumor Pathology
Amir R Honarmand, Michael C Hurley, Sameer A Ansari, Tord D Alden, Ryan Kuhn, Ali Shaibani
Regardless of the underlying pathology, elevated intracranial pressure is the endpoint of any impairment in either cerebrospinal fluid (CSF) absorption (including arachnoid villi) or intracranial venous drainage. In all age groups, the predominant final common pathway for CSF drainage is the dural venous sinus system. Intracranial venous hypertension (ICVH) is an important vascular cause of intracranial hypertension (and its subsequent sequelae), which has often been ignored due to excessive attention to the arterial system and, specifically, arteriovenous shunts...
April 2016: Interventional Neuroradiology
Charles Raybaud
PURPOSE: This study was conducted to design a rational approach to the MR diagnosis of hydrocephalus based on a pathophysiologic reevaluation of its possible mechanisms and to apply it to the different etiological contexts. METHOD: A review of the literature reports describing new physiologic models of production and absorption and of the hydrodynamics of the CSF was made. RESULTS: Besides the secretion of CSF by the choroid plexuses, and its passive, pressure-dependent transdural absorption (arachnoid villi, dural clefts, cranial, and spinal nerve sheaths), water transporters, aquaporins, allow water (if not ions and organic molecules) to exchange freely between the brain parenchyma and the CSF spaces across the ependymal and the pial interfaces (including the Virchow-Robin spaces)...
January 2016: Child's Nervous System: ChNS: Official Journal of the International Society for Pediatric Neurosurgery
Reynold Spector, S Robert Snodgrass, Conrad E Johanson
In this review, a companion piece to our recent examination of choroid plexus (CP), the organ that secretes the cerebrospinal fluid (CSF), we focus on recent information in the context of reliable older data concerning the composition and functions of adult human CSF. To accomplish this, we define CSF, examine the methodology employed in studying the CSF focusing on ideal or near ideal experiments and discuss the pros and cons of several widely used analogical descriptions of the CSF including: the CSF as the "third circulation," the CSF as a "nourishing liquor," the similarities of the CSF/choroid plexus to the glomerular filtrate/kidney and finally the CSF circulation as part of the "glymphatic system...
November 2015: Experimental Neurology
Takahiko Tokuda, Shinya Kida
It has been recently pointed out that there are fallacies in the bulk flow theory, a dogmatic idea of cerebrospinal fluid (CSF) physiology, which assumes that CSF is produced by the choroid plexus and circulates unidirectionally from the ventricles to the subarachnoid space to be absorbed by the arachnoid villi in the parietal region. Therefore, CSF physiology now needs to be reconsidered. Since there is free exchange of water between the CSF and the brain interstitial fluid (ISF), when considering the dynamics of water in the brain, we should regard these two fluid compartments collectively as brain extracellular fluid...
May 2015: Brain and Nerve, Shinkei Kenkyū No Shinpo
Stephen B Hladky, Margery A Barrand
Interstitial fluid (ISF) surrounds the parenchymal cells of the brain and spinal cord while cerebrospinal fluid (CSF) fills the larger spaces within and around the CNS. Regulation of the composition and volume of these fluids is important for effective functioning of brain cells and is achieved by barriers that prevent free exchange between CNS and blood and by mechanisms that secrete fluid of controlled composition into the brain and distribute and reabsorb it. Structures associated with this regular fluid turnover include the choroid plexuses, brain capillaries comprising the blood-brain barrier, arachnoid villi and perineural spaces penetrating the cribriform plate...
2014: Fluids and Barriers of the CNS
Etsuro Mori, Shinya Yamada
The morphological features of disproportionately enlarged subarachnoid-space hydrocephalus (DESH), the core type of idiopathic normal pressure hydrocephalus, can not be explained by the classical theory of CSF absorption at the arachnoid villi and the hypothesis of CSF flow blocking at the convexity subarachnoid spaces. By using MRI Time-SLIP CSF flow imaging, we demonstrated that CSF freely move in the subarachnoid spaces below and in the Sylvian fissures. CSF does not move in the convexity subarachnoid spaces in healthy individuals and patients with DESH, indicating the presence of flow obstacles in the convexity subarachnoid spaces by nature...
2014: Rinshō Shinkeigaku, Clinical Neurology
Masatsune Ishikawa
It has long been considered that cerebrospinal fluid (CSF) flows from choroid plexus through the aqueduct, and finally is absorbed from the arachnoid villi near the superior sagittal to mix the venous blood. Recently, this CSF bulk flow theory is challenged by new ideas, one of which claims that brain capillaries are a major site for production and absorption of CSF. This new idea gives revision of previous understandings of CSF production, absorption and dynamics. However, revision of previous works may provide a great progress in CSF research...
2014: Rinshō Shinkeigaku, Clinical Neurology
Takahiko Tokuda
Recently, there has been emerging a new attractive hypothesis that cerebrospinal fluid (CSF) is not circulating or absorbed from arachnoid villi, but absorbed from capillaries of the brain surface to vasculature or excreting through arterial walls and cribriform plate to cervical lymph nodes. About 90% of patients with iNPH (idiopathic normal pressure hydrocephalus) show DESH (Disproportionately Enlarged Subarachnoid-space Hydrocephalus) sign on brain CT/MRI. Identification of the DESH sign is important for the diagnosis of iNPH, and it is helpful for the judgement whether DESH sign is positive or not to detect apparent hyperperfusion in the high-convexity of the brain in iNPH patients with N-isopropyl-p-[(123)I] iodoamphetamine (IMP) single photon emission computed tomography (SPECT)...
2014: Rinshō Shinkeigaku, Clinical Neurology
Pravin Salunke, Ravi Garg, Ankur Kapoor, Rajesh Chhabra, Kanchan K Mukherjee
OBJECT: Contralateral subdural hygromas are occasionally observed after decompressive craniectomies (DCs). Some of these hygromas are symptomatic, and the etiology and management of these symptomatic contralateral subdural collections (CLDCs) present surgical challenges. The authors share their experience with managing symptomatic CLSDCs after a DC. METHODS: During a 10-month period, 306 patients underwent a DC. Of these patients, 266 had a head injury, 25 a middle cerebral artery infarction (that is, a thrombotic stroke), and 15 an infarction due to a vasospasm (resulting from an aneurysmal subarachnoid hemorrhage [SAH])...
March 2015: Journal of Neurosurgery
Masaki Ueno, Yoichi Chiba, Koichi Matsumoto, Toshitaka Nakagawa, Hiroshi Miyanaka
Intravascular substances invade extracellular spaces in the brain via endothelial cells in the sites without bloodbrain barrier (BBB) and move not only in the cerebrospinal fluid (CSF) but also in the interstitial fluid (ISF) of brain parenchyma adjacent to non-BBB sites. It is likely that CSF drains directly into the blood via arachnoid villi and granulations and also to lymph nodes via subarachnoid spaces in the brain and nasal lymphatics, whereas ISF drains to cervical lymph nodes through pathways along vascular wall of capillaries and arteries...
2014: Current Medicinal Chemistry
Taha M Mehemed, Yasutaka Fushimi, Tomohisa Okada, Akira Yamamoto, Mitsunori Kanagaki, Aki Kido, Koji Fujimoto, Naotaka Sakashita, Kaori Togashi
Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF...
2014: PloS One
S Tsutsumi, I Ogino, M Miyajima, M Nakamura, Y Yasumoto, H Arai, M Ito
BACKGROUND AND PURPOSE: Studies have suggested that arachnoid villi or granulations found in the walls of the cranial dural sinuses, olfactory mucosa, and cranial nerve sheaths function as outlets for intracranial CSF. However, their role as CSF outlets has not yet been verified. Here we show that arachnoid protrusions and contiguous diploic veins provide an alternative drainage route for intracranial CSF. MATERIALS AND METHODS: Four hundred patients with intact skull, dura mater, and dural sinuses underwent MR imaging to explore arachnoids protruding into the skull and diploic veins...
September 2014: AJNR. American Journal of Neuroradiology
D G Gomez, J E Ehrmann, D Gordon Potts, A M Pavese, A Gilanian
Portions of the superior sagittal sinus and lacunae laterales containing arachnoid villi and granulations from 8 full-term newborn babies were studied by transmission electron microscopy. Arachnoid proliferations from 3 subjects were distended and fixed in vitro by applying a differential pressure of 8 cm H2O to the subarachnoid aspect of the tissues. The remaining cases were fixed in a collapsed state. Distended arachnoid proliferations showed morphologic characteristics associated with similar functional structures in experimental animals: shortened and enlarged interendothelial spaces; micropinocytotic activity and a system of endothelial-lined tubules...
1983: International Journal of Developmental Neuroscience
Thomas Brinker, Edward Stopa, John Morrison, Petra Klinge
According to the traditional understanding of cerebrospinal fluid (CSF) physiology, the majority of CSF is produced by the choroid plexus, circulates through the ventricles, the cisterns, and the subarachnoid space to be absorbed into the blood by the arachnoid villi. This review surveys key developments leading to the traditional concept. Challenging this concept are novel insights utilizing molecular and cellular biology as well as neuroimaging, which indicate that CSF physiology may be much more complex than previously believed...
2014: Fluids and Barriers of the CNS
Maria Adele Marino, Rosa Morabito, Sergio Vinci, Antonino Germanò, Marilena Briguglio, Concetta Alafaci, Enricomaria Mormina, Marcello Longo, Francesca Granata
External hydrocephalus (EH) is a benign clinical entity in which macrocephaly is associated with an increase in volume of the subarachnoid space, especially overlying both frontal lobes, and a normal or only slight increase in volume of the lateral ventricles. Several pathogenic hypotheses have been proposed but the most accredited theory seems to be delayed maturation of the arachnoid villi. There is a consensus that this is a benign entity, correlated to a familial predisposition and, in some cases, inheritance...
April 2014: Neuroradiology Journal
T Taoka, Y Ida, H Nakagawa, S Iwasaki, M Sakamoto, A Fukusumi, K Takayama, T Wada, K Myochin, C Wuttikul, K Kichikawa
The purpose of the study was to evaluate the number and size of arachnoid markings on the inner plate of the skull on 3D-CT. The subjects included 16 hydrocephalus and 26 non-hydrocephalus cases. We evaluated the correlation between age and both the number and sizes of the arachnoid markings, and compared them between hydrocephalus and non-hydrocephalus cases. We also evaluated cases exhibiting a "smooth cranium" that had no arachnoid markings at all on the inner plate. There was a positive correlation between age and the number of the arachnoid markings...
June 30, 2007: Neuroradiology Journal
Hironaka Igarashi, Mika Tsujita, Ingrid L Kwee, Tsutomu Nakada
Recent studies on cerebrospinal fluid (CSF) homeostasis emphasize the importance of water flux through the pericapillary (Virchow-Robin) space for both CSF production and reabsorption (Oreskovic and Klarica hypothesis), and challenge the classic CSF circulation theory, which proposes that CSF is primarily produced by the choroid plexus and reabsorbed by the arachnoid villi. Active suppression of aquaporin-1 (AQP-1) expression within brain capillaries and preservation of AQP-1 within the choroid plexus together with pericapillary water regulation by AQP-4 provide a unique opportunity for testing this recent hypothesis...
January 8, 2014: Neuroreport
R O Carare, C A Hawkes, R O Weller
Immunological privilege appears to be a product of unique lymphatic drainage systems for the brain and receptor-mediated entry of inflammatory cells through the blood-brain barrier. Most organs of the body have well-defined lymphatic vessels that carry extracellular fluid, antigen presenting cells, lymphocytes, neoplastic cells and even bacteria to regional lymph nodes. The brain has no such conventional lymphatics, but has perivascular pathways that drain interstitial fluid (ISF) from brain parenchyma and cerebrospinal fluid (CSF) from the subarachnoid space to cervical lymph nodes...
February 2014: Brain, Behavior, and Immunity
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