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Journal ArticleDOI

Compartmental analysis of compliance and outflow resistance of the cerebrospinal fluid system

01 Nov 1975-Journal of Neurosurgery (Journal of Neurosurgery Publishing Group)-Vol. 43, Iss: 5, pp 523-534
TL;DR: The distribution of compliance and outflow resistance between cerebral and spinal compartments was measured in anesthetized, ventilated cats by analysis of the cerebrospinal fluid (CSF) pressure response to changes in CSF volume.
Abstract: ✓ The distribution of compliance and outflow resistance between cerebral and spinal compartments was measured in anesthetized, ventilated cats by analysis of the cerebrospinal fluid (CSF) pressure response to changes in CSF volume. Cerebral and spinal compartments were isolated by inflating a balloon positioned epidurally at the level of C-6. The change of CSF volume per unit change in pressure (compliance) and change of CSF volume per unit of time (absorption) were evaluated by inserting pressure data from the experimental responses into a series of equations developed from a mathematical model. It was found that 68% of total compliance is contributed by the cerebral compartment while the remaining 32% is contained within the spinal axis. The cerebral compartment accounted for 84% of total CSF absorption. The mechanism for spinal absorption appears to be similar in that no differences were obvious on the basis of pressure dynamics.
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Journal ArticleDOI
TL;DR: This review integrates eight aspects of cerebrospinal fluid (CSF) circulatory dynamics: formation rate, pressure, flow, volume, turnover rate, composition, recycling and reabsorption.
Abstract: This review integrates eight aspects of cerebrospinal fluid (CSF) circulatory dynamics: formation rate, pressure, flow, volume, turnover rate, composition, recycling and reabsorption. Novel ways to modulate CSF formation emanate from recent analyses of choroid plexus transcription factors (E2F5), ion transporters (NaHCO3 cotransport), transport enzymes (isoforms of carbonic anhydrase), aquaporin 1 regulation, and plasticity of receptors for fluid-regulating neuropeptides. A greater appreciation of CSF pressure (CSFP) is being generated by fresh insights on peptidergic regulatory servomechanisms, the role of dysfunctional ependyma and circumventricular organs in causing congenital hydrocephalus, and the clinical use of algorithms to delineate CSFP waveforms for diagnostic and prognostic utility. Increasing attention focuses on CSF flow: how it impacts cerebral metabolism and hemodynamics, neural stem cell progression in the subventricular zone, and catabolite/peptide clearance from the CNS. The pathophysiological significance of changes in CSF volume is assessed from the respective viewpoints of hemodynamics (choroid plexus blood flow and pulsatility), hydrodynamics (choroidal hypo- and hypersecretion) and neuroendocrine factors (i.e., coordinated regulation by atrial natriuretic peptide, arginine vasopressin and basic fibroblast growth factor). In aging, normal pressure hydrocephalus and Alzheimer's disease, the expanding CSF space reduces the CSF turnover rate, thus compromising the CSF sink action to clear harmful metabolites (e.g., amyloid) from the CNS. Dwindling CSF dynamics greatly harms the interstitial environment of neurons. Accordingly the altered CSF composition in neurodegenerative diseases and senescence, because of adverse effects on neural processes and cognition, needs more effective clinical management. CSF recycling between subarachnoid space, brain and ventricles promotes interstitial fluid (ISF) convection with both trophic and excretory benefits. Finally, CSF reabsorption via multiple pathways (olfactory and spinal arachnoidal bulk flow) is likely complemented by fluid clearance across capillary walls (aquaporin 4) and arachnoid villi when CSFP and fluid retention are markedly elevated. A model is presented that links CSF and ISF homeostasis to coordinated fluxes of water and solutes at both the blood-CSF and blood-brain transport interfaces.

751 citations


Cites result from "Compartmental analysis of complianc..."

  • ...This more-or-less reciprocal relationship between CBV and CSF volume reflects the fact that, according to the Munro-Kelly doctrine [191], the combined volume of blood, CSF and brain remains relatively constant in the intracranial space bounded by the rigid skull....

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Journal ArticleDOI
TL;DR: Of the 48 patients who died, severe intracranial hypertension was the primary cause of death in nearly half and even moderately increased ICP (greater than 20 mm Hg) was associated with higher morbidity in patients with mass lesions and those with diffuse brain injury.
Abstract: ✓ Measurements of intracranial pressure (ICP) were begun within hours of injury in 160 patients with severe brain trauma, and continued in the intensive care unit. Some degree of increased ICP (> 10 mm Hg) was present on admission in most cases (82%), and in all but two of the 62 patients with intracranial mass lesions requiring surgical decompression; ICP was over 20 mm Hg on admission in 44% of cases, and over 40 mm Hg in 10%. In patients with mass lesions only very high ICP (> 40 mm Hg) on admission was significantly associated with a poor neurological picture and outcome from injury, while in patients with diffuse brain injury any increase in ICP above 10 mm Hg was associated with a poorer neurological status and a worse outcome. Despite intensive measures aimed at prevention of intracranial hypertension, ICP rose over 20 mm Hg during the monitoring period in 64 of the 160 patients (40%). Postoperative increases in ICP over 20 mm Hg (mean) were seen in 52% of the patients who had had intracranial mass...

727 citations

Journal ArticleDOI
TL;DR: Dynamic tests were developed for rapid measurement of CSF formation, absorption resistance, and the bulk intracranial compliance, applicable to clinical settings, providing data that are useful in characterizing the physiological mechanisms responsible for raised ICP and assessing changes induced by therapy.
Abstract: A mathematical model of the cerebrospinal fluid (CSF) system was developed to help clarify the kinetics of the intracranial pressure (ICP). A general equation predicting the time course of pressure was derived in terms of four parameters: the intracranial compliance, dural sinus pressure, resistance to absorption, and CSF formation. These parameters were measured in the adult cat, and the equation was tested by comparing experimental and calculated values of the time course of pressure in response to volume changes. The theoretical and experimental results were in close agreement, and the role of each parameter in governing the dynamic equilibrium of the ICP was determined. From this analysis, dynamic tests were developed for rapid measurement of CSF formation, absorption resistance, and the bulk intracranial compliance. These techniques are applicable to clinical settings, providing data that are useful in characterizing the physiological mechanisms responsible for raised ICP and assessing changes induced by therapy.

563 citations

Journal ArticleDOI
01 Aug 1998
TL;DR: More research on reproducibility and inter-method comparisons is urgently needed, particularly involving the assessment of pressure autoregulation in individuals rather than patient groups, and it is not clear whether the two approaches are interchangeable.
Abstract: Assessment of cerebral autoregulation is an important adjunct to measurement of cerebral blood flow for diagnosis, monitoring or prognosis of cerebrovascular disease. The most common approach tests the effects of changes in mean arterial blood pressure on cerebral blood flow, known as pressure autoregulation. A 'gold standard' for this purpose is not available and the literature shows considerable disparity of methods and criteria. This is understandable because cerebral autoregulation is more a concept rather than a physically measurable entity. Static methods utilize steady-state values to test for changes in cerebral blood flow (or velocity) when mean arterial pressure is changed significantly. This is usually achieved with the use of drugs, shifts in blood volume or by observing spontaneous changes. The long time interval between measurements is a particular concern in many of the studies reviewed. Parallel changes in other critical variables, such as pCO2, haematocrit, brain activation and sympathetic tone, are rarely controlled for. Proposed indices of static autoregulation are based on changes in cerebrovascular resistance, on parameters of the linear regression of flow/velocity versus pressure changes, or only on the absolute changes in flow. The limitations of studies which assess patient groups rather than individual cases are highlighted. Newer methods of dynamic assessment are based on transient changes in cerebral blood flow (or velocity) induced by the deflation of thigh cuffs, Valsalva manoeuvres, tilting and induced or spontaneous oscillations in mean arterial blood pressure. Dynamic testing overcomes several limitations of static methods but it is not clear whether the two approaches are interchangeable. Classification of autoregulation performance using dynamic methods has been based on mathematical modelling, coherent averaging, transfer function analysis, crosscorrelation function or impulse response analysis. More research on reproducibility and inter-method comparisons is urgently needed, particularly involving the assessment of pressure autoregulation in individuals rather than patient groups.

506 citations

References
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Journal ArticleDOI
TL;DR: The cerebrospinal fluid pressure‐volume curve was determined by measuring the pressure response to rapid injection of fluid into the cisterna magna of dogs, by means of a constant flow infusion pump.
Abstract: The cerebrospinal fluid pressure-volume curve was determined by measuring the pressure response to rapid injection of fluid into the cisterna magna of dogs, by means of a constant flow infusion pump. The shape of the curve is complex, with two plateaus at the levels of the venous and arterial pressures, respectively. The slope dP/dV is referred to as the elastance of the system (mmHg/ml). The elastance has a low value in the normal pressure range and shifts at a fluid pressure of about 15 mmHg to a value approximately 20 times higher, with a relatively minute change in the volume of the system.

229 citations

Journal ArticleDOI
TL;DR: A quantitative analysis of the contributions of the cranial and spinal compartments to the cerebrospinal fluid pressure‐volume curve was made using dogs using dogs to represent the effects on the fluid pressure of forced alterations in the volume of the intracranial vascular bed.
Abstract: A quantitative analysis of the contributions of the cranial and spinal compartments to the cerebrospinal fluid pressure-volume curve was made using dogs. The curve was determined by rapid continuous injection of fluid into the cisterna magna with simultaneous measurement of the pressure. Spinal block at the C 1 level was produced by inflation of an epidural rubber balloon allowing the recording of the pressure-volume curve for the isolated cranial system. By subtraction of the two curves obtained, the spinal pressure-volume curve could be calculated. 70 % of the variation in volume within the system was related to the spinal section and 30 % to the cranial section. The intracranial curve represents the effects on the fluid pressure of forced alterations in the volume of the intracranial vascular bed. The spinal compartment has a quantitatively defined and probably mechanically important function as an expansion vessel for the intracranial system.

107 citations

Journal ArticleDOI
TL;DR: Evidence of normal ventricular pressure does not exclude the possibility of progressive hydrocephalus, and increased pressure is likely to occur for quite long periods while the hydrocephalic infant is engaged in normal infantile activities.
Abstract: SUMMARY Intraventricular pressure in infants with progressive hydrocephalus was found to be within the normal range while the infants were resting, but wide fluctuations in pressure occurred during periods of activity such as sucking, crying or straining. Thus, evidence of normal ventricular pressure does not exclude the possibility of progressive hydrocephalus, and increased pressure is likely to occur for quite long periods while the hydrocephalic infant is engaged in normal infantile activities. A pressure-volume index is discussed, by which it is hoped to quantify rates of CSF formation and absorption in a less complex manner than is possible by the perfusion technique. RESUME Considerations sur le rapport pression-volume dans l'hydrocephalic infantile La pression intraventriculaire chez le nourrisson avec hydrocephalic progressive a ete trouvee dans les limites du normal lorsque les nourrissons etaient au repos, mais de larges fluctuations de pression ont ete relevees durant les periodes d'activite comme la succion, les pleurs ou les efforts. Ainsi, l'existence d'une pression ventriculaire normale ne doit pas faire exclure la possibilite d'une hydrocephalic progressive et une pression augmentee doit etre considered comme probable durant de longues periodes, lorsque l'enfant hydrocephale est au cours d'activites infantiles normales. Un index pression-volume est discute, par lequel les auteurs esperent quantifier les taux de formation et d'absorption du LCR d'une maniere plus simple qu'il n'est possible avec les techniques de perfusion. ZUSAMMENFASSUNG Druck-Volumen-Betrachtungen beim kindlichen Hydrocephalus Bei Kindern mit progressivem Hydrocephalus fanden sich in Ruhe intraventrikulare Druckverhaltnisse im Normbereich, wahrend in Zeiten der Aktivitat, wie Trinken, Schreien oder Strampeln, grose Druckschwankungen auftraten. Somit schliest ein normaler Ventrikeldruck die Moglichkeit eines progressiven Hydrocephalus nicht aus und ein erhohter Druck ist fur recht lange Perioden zu erwarten, wenn das Kind mit Hydrocephalus die normale Aktivitat des Sauglings entfaltet. Es wird ein Druck-Volumen-Index diskutiert, mit dessen Hilfe man hoffentlich die CSF Bildung und -Absorption in einer weniger umfassenden Weise als mit der Perfusionstechnik quantitativ erfassen kann.

69 citations