Definition and classification of hydrocephalus

The formation of cerebrospinal fluid: Nearly a hundred years of interpretations and misinterpretations

Blood-cerebrospinal fluid barrier alteration following intraventricularly administered cholera toxin

Cerebrospinal fluid formation and absorption and transport of iodide and sulfate from the spinal subarachnoid space.

A significant steady state or d.c. potential difference exists between the cerebrospinal and extracellular fluids of the anesthetized dogfish. Since the cerebrospinal fluid is negative with respect to the extracellular fluid and the chloride concentration is greater in cerebrospinal fluid, the formation of cerebrospinal fluid must involve at least one process: active transport of Cl–. While acetazolamide abolishes the gradient of chloride between dogfish cerebrospinal fluid and plasma, its administration did not demonstrably change the potential difference. Though the active transport of Cl– is clearly part of the process of cerebrospinal fluid formation, it is probably only part of the process. No potential difference was observed between dogfish aqueous humor and extracellular fluid.

Rates of Formation and Absorption of Cerebrospinal Fluid in Mild Chronic Bovine Hypervitaminosis A

T HIS paper presents an experimental test of the assumption that the force of formation of cerebrospinal fluid causes the eerebrospinal fluid to circulate and the ventricles to enlarge when its pathways are blocked. These experiments show that this assmnption is wrong and a new description of the circulation of the cerebrospinal fluid is given. I t has always been assumed that the cerebral ventricular enlargement of hydroeephalus was caused by the back pressure of blocked circulation of the cerebrospinal fluid, but this has never been put to experimental test. The clinical facts of hydroeephalus leave no doubt that if some cerebrospinal fluid escapes from the cerebral ventricles internal hydrocephalus will be prevented or cured, if established, and experimental work has generally confirmed these facts. TM Dandy, 4 in his experiments on hydrocephalus and formation of cerebrospinal fluid in dogs, removed the choroid plexus from one lateral cerebral ventricle, plugged the foramen of Monro on the same side, and then occluded the aqueduct of Sylvius. In this animal there was an enlargement of the ventricle with the choroid plexus present and the foramen of Monro open, while the other lateral ventricle remained unchanged. This was interpreted as demonstrating that the choroid plexus produced the cerebrospinal fuid, and this has remained as the basic experimental work showing that the choroid plexuses were the major source of

Intracranial pressure (ICP), cerebral blood flow (CBF), and the cerebrospinal fluid (CSF) formation rate were examined in anesthetized cats during ammonia intoxication. Hyperammonemia, evoked by intravenous infusion of ammonium acetate, caused a significant increase in ICP when the arterial blood ammonia level exceeded 400 mumol X liter-1. A progressive elevation of blood ammonia concentration was followed by a gradual rise in CBF, measured by the xenon-133 clearance technique. At an arterial blood ammonia level exceeding 500 mumol X liter-1, the CBF reached a plateau at 30% above the mean control value. Increase in ICP correlated weakly, but significantly, with the increase in CBF (R = 0.489, p less than 0.005). Elevation of the arterial blood ammonia level to 780.4 +/- 25.5 mumol X liter-1 for 2 hours elicited a significant gradual increase in CSF formation rate, measured by the ventriculocisternal perfusion method with iodine-125-albumin as an indicator substance. A maximum increase in CSF flow of 81% was noted at the end of the ammonium acetate infusion. It is suggested that hyperammonemia increases ICP both by cerebral vasodilatation and by enhancement of the CSF formation rate.

Summary1. Water and electrolytes enter the cerebrospinal fluid rapidly both in the ventricles and throughout the subarachnoid space. The formation of the fluid is thus not an exclusive prerogative of the choroid plexus. 2. Water and electrolytes leave directly into the blood from both the ventricles and the subarachnoid space, doing so at roughly similar rates. 3. CSF does not suddenly come into being fully formed at any point with all its constituents in their proper ratios, but each constituent is exchanging with blood at its own characteristic rate. 4. In contrast to water and electrolytes, protein is absorbed largely from the subarachnoid space, presumably from the arachnoidal villi. By virtue of this specific role played by the arachnoid villi, they serve a function in the CSF system analogous to the lymphatics of‘the general circulation. 5. The site and rate of protein reabsorption is an important determinant of the direction and rate of CSF flow. 6. The net amount of CSF elaborated per day in the v...

Comparison of radio-iodinated serum albumin and blue dextran as indicators to measure rate of formation of cerebrospinal fluid

Alterations by antidepressants of cerebrospinal fluid formation and calcium distribution dynamics in the intact rat brain

BackgroundBetween 2009 and 2011 an attempt has been made to develop a consensus on the classification of hydrocephalus. Clinicians and basic scientists who are recognized internationally for their work in hydrocephalus attended working meetings in which the concepts of classification of hydrocephalus were discussed at length.PurposeThis review attempts to explain the relevance of a classification scheme based on the point of obstruction to the flow of cerebrospinal fluid to basic science research into the pathophysiology and effects of hydrocephalus. The review is designed to give examples of the value of this classification in analyzing research utilizing animal models. The development of hydrocephalus in the absence of a point of obstruction (true communicating hydrocephalus) is analyzed.ConclusionContemporary neuroimaging techniques are now available that can identify the actual point of obstruction to the flow of CSF, if any, which results in the development of hydrocephalus. Such identification may lead to improved ability to analyze animal models used in hydrocephalus research as well as deciding among various treatment options.

Intracranial pressure (ICP) research has significant importance in clinic. There are many internal or external factors which cause the vibration of ICP, including heart beat, breath, neural regulation, and so on. A lumped parameter mathematical model of ICP dynamics is established based on animal (dogs) experiments, which includes cerebrovascular bed, cerebrospinal fluid (CSF) formation and absorption, brain compliance, lumbar cerebrospinal fluid, and interactions between these factors. An exponential volume-pressure relationship is employed in this simulation to describe cerebrovascular compliance. The model well simulates intracranial pressure dynamics and the vibration of ICP when compared to animal experiments; the changes of parameters in simulation are consistent with animal experiments. It offers certain values for clinical ICP ward and diagnosis.

Hyperbaric Oxygen Therapy Associated with Ventricular–Subcutaneous Shunt Promotes Neuroprotection in Young Hydrocephalic Rats

Intracranial pressure (ICP) has been shown to increase dramatically during desflurane anesthesia, possibly as a result in part of an increase in the rate of cerebrospinal fluid (CSF) formation (Vf) or a decrease in the rate of CSF reabsorption. To examine this phenomenon, I designed a study to measure Vf, resistance to reabsorption of CSF (Ra), brain tissue water content, and the electroencephalographic activity (EEG) during desflurane anesthesia in dogs. Vf and Ra were determined using ventriculocisternal perfusion of mock CSF labeled with blue dextran. EEG activity was determined using aperiodic analysis. At the end of the study, brain tissue water contents of gray and white matter were determined by dry/wet weight ratios. Eighteen dogs were allocated into three groups. Group 1 (n = 6) was examined at five experimental conditions during normocapnia; group 2 (n = 6) was examined at five experimental conditions during hypocapnia. The experimental conditions for groups 1 and 2 were (a) baseline (halothane 0.5-1.0% inspired plus thiopental 12 mg.kg-1 i.v. given over 15 min followed by i.v. infusion at 12 mg.kg-1 x h-1), (b) 0.5 MAC (3.5 +/- 0.1% expired) and (c) 1.0 MAC (7.0 +/- 0.1% expired) desflurane at normal CSF pressure, and (d) and (e) 0.5 and 1.0 MAC desflurane at increased CSF pressure (> 30 cm H2O). Group 3 (n = 6), the control group, was examined over the same time period as groups 1 and 2. In the control group, desflurane was not administered; instead, the baseline condition (i.e., halothane plus thiopental) was maintained throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)

The formation of cerebrospinal fluid in two amphibians, Rana catesbeiana and Rana pipiens