Ventricular Cerebrospinal Fluid Pressure Research Articles

New experimental model of acute aqueductal blockage in cats: Effects on cerebrospinal fluid pressure and the size of brain ventricles

It is generally assumed that cerebrospinal fluid (CSF) is secreted in the brain ventricles, and so after an acute blockage of the aqueduct of Sylvius an increase in the ventricular CSF pressure and dilation of isolated ventricles may be expected. We have tested this hypothesis in cats. After blocking the aqueduct, we measured the CSF pressure in both isolated ventricles and the cisterna magna, and performed radiographic monitoring of the cross-sectional area of the lateral ventricle. The complete aqueductal blockage was achieved by implanting a plastic cannula into the aqueduct of Sylvius through a small tunnel in the vermis of the cerebellum in the chloralose-anesthetized cats. After the reconstitution of the occipital bone, the CSF pressure was measured in the isolated ventricles via a plastic cannula implanted in the aqueduct of Sylvius and in the cisterna magna via a stainless steel cannula. During the following 2 h, the CSF pressures in the isolated ventricles and cisterna magna were identical to those in control conditions. We also monitored the ventricular cross-sectional area by means of radiography for 2 h after the aqueductal blockage and failed to observe any significant changes. When mock CSF was infused into isolated ventricles to imitate the CSF secretion, the gradient of pressure between the ventricle and cisterna magna developed, and disappeared as soon as the infusion was terminated. However, when mock CSF was infused into the cisterna magna at various rates, the resulting increased subarachnoid CSF pressure was accurately transmitted across the brain parenchyma into the CSF of isolated ventricles. The lack of the increase in the CSF pressure and ventricular dilation during 2 h of aqueductal blockage suggests that aqueductal obstruction by itself does not lead to development of hypertensive acute hydrocephalus in cats.

The Pathogenesis of Normal Pressure Hydrocephalus: A Theoretical Analysis

Hydrocephalus is an abnormal accumulation of cerebrospinal fluid (CSF) in the cerebral ventricles, usually caused by impaired absorption of the fluid into the bloodstream. Despite obstructed absorption and continued secretion of CSF into the ventricles at a near normal rate, the ventricular CSF pressure (VCSFP) is often normal. We attempt to understand how hydrocephalus can exist with normal VCSFP by exploring the role of the brain parenchyma in absorbing CSF in hydrocephalus. We test three theories: (1) the ventricular wall is impermeable to CSF; (2) ventricular CSF seeps into the parenchyma, from which it is efficiently absorbed; and (3) ventricular CSF seeps into the parenchyma but is absorbed inefficiently. We model the brain as a thick spherical shell consisting of a porous, elastic, solid matrix, containing interstitial fluid and blood. We modify the equations of poroelasticity, which describe flow of fluid through porous solids, to allow for parenchymal absorption. For each of the three theories we calculate the steady state changes in VCSFP and in parenchymal fluid pressure caused by an incremental defect in CSF absorption. We also calculate the steady state changes in fluid content, tissue volume, tissue displacement, and stresses caused by a small increment of VCSFP. We conclude that only the second theory—seepage of CSF with efficient parenchymal absorption—accounts for the clinical features of normal pressure hydrocephalus. These features include sustained ventricular dilatation despite normal VCSFP, increased periventricular fluid content, and localized periventricular white matter damage.

Simultaneous lumbar and intraventricular manometry to evaluate the role and safety of lumbar puncture in raised intracranial pressure following subarachnoid haemorrhage.

We report a prospective investigation of a bedside test to evaluate the role and safety of lumbar puncture in raised intracranial pressure in patients with subarachnoid haemorrhage. Fourteen patients who underwent aneurysm clipping following subarachnoid haemorrhage were studied. All patients had intraventricular drains and needed high volume cerebrospinal fluid (CSF) drainage to maintain the normal intracranial pressure. A lumbar puncture was performed in these patients and the simultaneous opening lumbar and ventricular pressures noted, CSF was then drained via the lumbar puncture, and the simultaneous closing lumbar and ventricular pressures noted. In all patients, the opening lumbar pressure was close to the ventricular pressure. In 13 of 14 patients, CSF drainage resulted in an equivalent and simultaneous fall of ventricular pressure. We concluded that simultaneous measurement of lumbar and ventricular CSF pressure before and after lumbar CSF drainage allows identification of candidates with differential cranial and lumbar pressures and therefore indicates safety or risk of lumbar CSF drainage.

Cerebral energy metabolism in experimental canine hydrocephalus

Cerebral energy metabolism, its relationship to the stage and extent of hydrocephalus, and the effect of cerebrospinal fluid (CSF) removal on it were studied in experimental canine hydrocephalus produced by intracisternal injection of kaolin by using phosphorus-31 (P-31) magnetic resonance (MR) spectroscopy and MR imaging. P-31 MR spectra were serially obtained before and after CSF removal, maximally on eight occasions over a period of nearly 5 h. There was a decrease in the ratio of creatine phosphate to inorganic phosphate, used as an indicator of the bioenergetic state, in acute and subacute stages of hydrocephalus as compared with the control. An animal in the subacute stage, when periventricular edema was most prominent, exhibited the most predominent decrease in this ratio at 14 days after hydrocephalic insult. The recovery of the ratio toward the control level was seen in the chronically hydrocephalic animal. There was no change in adenosine triphosphate (ATP) levels in any stage of hydrocephalus. Serial spectra obtained after the withdrawal of ventricular CSF showed no change in the bioenergetic state of the brain in any stage of hydrocephalus. There was no relationship between either the extent of hydrocephalus or the ventricular CSF pressure and the change in the bioenergetic state or the levels of any of the phosphorus compounds. These findings may indicate the alteration of the mitochondrial energy metabolism in hydrocephalus, which may explain the mechanism of hydrocephalic syndrome.

Isoflurane and cerebrospinal fluid pressure—a study in neurosurgical patients undergoing intracranial shunt procedures

The effect of isoflurane 1.0% and 1.5% with nitrous oxide on ventricular cerebrospinal fluid pressure was studied in 17 patients who underwent intracranial shunt procedures. Isoflurane at both concentrations caused significant increases in cerebrospinal fluid pressure during normocapnic ventilation, but these could be prevented by simultaneous hyperventilation or by the prior induction of hypocapnia. Decreases in mean arterial pressure occurred also, and resulted in a significant reduction in cerebral perfusion pressure in normocapnic patients.

The relationship between intracranial pressure, disturbances of brain function and prognosis

Long term measurements of the ventricular CSF pressure were made in 236 patients, before and after brain operations or trauma. Neither a definite rise in daily average pressure, nor the daily maximum values proved of any value in determining the prognosis when considered on their own. However, an analysis of the V F P over the course of several days, in relation to the simultaneous disturbances of neurological function, and particularly level of consciousness and brain metabolism (as shown by the CSF lactate levels), gives a much clearer indication as regards the prognosis. Thus, no patient survived when, after the fourth post-operative/post-traumatic day, there still persisted an average daily rise of V F P over 20 mm Hg which was associated with coma and a CSF lactate level of over 2.0 mmol/l.

Fatty acid in cerebrospinal fluid of congenital hydrocephalus.

In this presentation the analysis of fatty acid composition in cerebrospinal fluid (CSF), by gas-chromatography, in 40 cases of congenital hydrocephalus before and after shunting operation is discussed. Each fatty acid content was determined by the method which uses arachidic acid as an indicator. The total fatty acid value was found to be significantly higher than normal in the preoperative period in hydrocephalus. The concentration of the total and of the short chain fatty acids (less than C16) in the CSF was higher in the high ventricular CSF pressure group of hydrocephalic patients (above 150 mm H2O) than in the low pressure group. The concentration level of all these fatty acids in the CSF was higher in the cases showing poor prognosis than in those with good prognosis 3 weeks after operation.