Three-dimensional cerebrospinal fluid flow within the human ventricular system

Cerebrospinal fluid (CSF) is a Newtonian fluid and can, therefore, be modelled using computational fluid dynamics (CFD). Previous modelling of the CSF has been limited to simplified geometric models. This work describes a geometrically accurate three dimensional (3D) computational model of the human ventricular system (HVS) constructed from magnetic resonance images (MRI) of the human brain. It is an accurate and full representation of the HVS and includes appropriately positioned CSF production and drainage locations. It was used to investigate the pulsatile motion of CSF within the human brain. During this investigation CSF flow rate was set at a constant 500 ml/day, to mimic real life secretion of CSF into the system, and a pulsing velocity profile was added to the inlets to incorporate the effect of cardiac pulsations on the choroid plexus and their subsequent influence on CSF motion in the HVS. Boundary conditions for the CSF exits from the ventricles (foramina of Magendie and Lushka) were found using a "nesting" approach, in which a simplified model of the entire central nervous system (CNS) was used to examine the effects of the CSF surrounding the ventricular system (VS). This model provided time varying pressure data for the exits from the VS nested within it. The fastest flow was found in the cerebral aqueduct, where a maximum velocity of 11.38 mm/s was observed over five cycles. The maximum Reynolds number recorded during the simulation was 15 with an average Reynolds number of the order of 0.39, indicating that CSF motion is creeping flow in most of the computational domain and consequently will follow the geometry of the model. CSF pressure also varies with geometry with a maximum pressure drop of 1.14 Pa occurring through the cerebral aqueduct. CSF flow velocity is substantially slower in the areas that are furthest away from the inlets; in some areas flow is nearly stagnant.     

Three-dimensional cerebrospinal fluid flow within the human ventricular system

Cerebrospinal fluid (CSF) is a Newtonian fluid and can, therefore, be modelled using computational fluid dynamics (CFD). Previous modelling of the CSF has been limited to simplified geometric models. This work describes a geometrically accurate three dimensional (3D) computational model of the human ventricular system (HVS) constructed from magnetic resonance images (MRI) of the human brain. It is an accurate and full representation of the HVS and includes appropriately positioned CSF production and drainage locations. It was used to investigate the pulsatile motion of CSF within the human brain. During this investigation CSF flow rate was set at a constant 500 ml/day, to mimic real life secretion of CSF into the system, and a pulsing velocity profile was added to the inlets to incorporate the effect of cardiac pulsations on the choroid plexus and their subsequent influence on CSF motion in the HVS. Boundary conditions for the CSF exits from the ventricles (foramina of Magendie and Lushka) were found using a “nesting” approach, in which a simplified model of the entire central nervous system (CNS) was used to examine the effects of the CSF surrounding the ventricular system (VS). This model provided time varying pressure data for the exits from the VS nested within it. The fastest flow was found in the cerebral aqueduct, where a maximum velocity of 11.38 mm/s was observed over five cycles. The maximum Reynolds number recorded during the simulation was 15 with an average Reynolds number of the order of 0.39, indicating that CSF motion is creeping flow in most of the computational domain and consequently will follow the geometry of the model. CSF pressure also varies with geometry with a maximum pressure drop of 1.14 Pa occurring through the cerebral aqueduct. CSF flow velocity is substantially slower in the areas that are furthest away from the inlets; in some areas flow is nearly stagnant.     

Method of intracranial pressure monitoring and cerebrospinal fluid sampling in swine

Cerebral oedema and encephalopathy have been noted to occur frequently in patients severely ill or dying after trauma, ischaemia, infections or even metabolic disorders. The objective of the present study was to establish continuous monitoring of the intracranial pressure (ICP) and sampling of cerebrospinal fluid (CSF) for further investigations in swine. ICP monitoring was established in eight pigs by using a ventricular drainage system, implemented after paramedian trepanation of the os frontale. CSF and serum samples were taken for measurement of the levels of glucose and protein. Operating time was 21+/-8 min for the trepanation until ICP monitoring was performed. No complications occurred during surgery. Continuous monitoring of ICP and CSF sampling was easy to perform, and without any side-effects in any animal. At autopsy, no iatrogenic lesions were found and monitoring catheters were still in place. For several types of research requiring ICP monitoring and sampling of CSF, this method can be used successfully.     

Immunoreactive LHRH in cerebrospinal fluid: the clinical significance in intracranial diseases

Cerebrospinal fluid (CSF) and plasma levels of luteinizing hormone-releasing hormone (LHRH) were measured by RIA in 46 patients with acute intracranial diseases, ie, cerebral bleeding (group A), cerebral thrombosis (B), head injury (C) and meningitis (D), and the results were compared to those obtained in 21 patients with non-intracranial diseases (group E; control). Immunoreactive LHRH concentrations in CSF (CSF IR-LHRH) of 8 postmenopausal women in group E ranged 1.3 to 6.1 (mean +/- SE: 3.1 +/- 0.6) pg/ml, and those of 5 other women and 8 men with group E ranged 1.0 to 5.6 (3.6 +/- 0.4)pg/ml. In 7 out of 15 patients in group A(7/15), CSF IR-LHRH were above the levels seen in group E. In group B, C and D, CSF IR-LHRH were above the control levels in 9/15, 1/9, 3/7, respectively. The changes in plasma LHRH were not clear in postmenopausal patients in groups A and B. Plasma IR-LHRH in other women and men in group A were above the control levels in 2 out of 9 patients (2/9). Those in groups B, C and D were above the control levels in 3/8, 1/9, 2/7, respectively. Moreover, both plasma and CSF IR-LHRH of 13 patients in group A or B in chronic stage were within the control ranges. In cases observed following the time course, the occasionally increased IR-LHRH in plasma and CSF tended to decrease following the abatement of the diseases.(ABSTRACT TRUNCATED AT 250 WORDS)     

An immunocytochemical study of normal and abnormal human cerebrospinal fluid with monoclonal antibodies to glial fibrillary acidic protein

The presence of astrocytes in the cerebrospinal fluid (CSF) of patients may be of diagnostic importance. However, the frequency with which astrocytes are shed into normal and abnormal human CSF is unknown. This issue was studied using monoclonal antibodies to an astrocyte-specific antigen, glial fibrillary acidic protein (GFAP), and immunoperoxidase cytochemistry. The study was prospectively conducted on 108 CSF preparations diagnosed as normal, reactive, metastatic malignancy or suspicious for metastatic malignancy. To validate these methods, cells from a clonal human glioma cell line, which contains astrocytes rich in GFAP, were processed in a manner identical to that used for the CSFs obtained from patients. Studies of the human glioma cell line demonstrated intense GFAP immunoreactivity in the majority of the malignant astrocytes. In contrast, none of the CSFs contained GFAP-positive cells. We conclude that immunocytochemical methods can detect GFAP in neoplastic human astrocytes but that nonneoplastic GFAP-positive cells are uncommon in human CSF; such cells were not seen in our large series of normal and abnormal human CSFs. The immunocytochemical detection of GFAP may be a useful criterion for distinguishing malignant astrocytes from other types of malignant cells in human CSF.     

The effect of craniotomy on the intracranial hemodynamics and cerebrospinal fluid dynamics in humans

The goal of the research was to study the effect of the trephination of the human cranial cavity on the intracranial hemodynamics and cerebrospinal fluid (CSF) dynamics. The sample comprised 15 patients of a neurosurgical clinic in whom a trephine opening in the cranial bones was made for medical indications. In these patients, at rest and during an appropriate functional load, we recorded pulse changes in blood circulation (by transcranial Doppler sonography) and in the ratio between the pulse fluctuations in the blood and CSF volumes (by rheoencephalography) before and after surgery. Simultaneous recording of these parameters followed by computer pattern and phase analyses allowed evaluation of the complex biomedical compliance of the cranium during successive phases of the cardiac rhythm: the inflow of arterial blood, the redistribution of blood/CSF volumes, and the outflow of venous blood. Analysis of the results showed a beneficial influence of craniotomy on the intracranial hemodynamics and CSF dynamics. This was reflected in an increase in the cranial compliance, which increased the pulse increment in the volume of the arterial blood in the skull almost twofold. After craniotomy, the cross-flow of CSF between the cranial and spinal cavities decreased significantly, giving way to volumetric compensatory translocations of blood and CSF within the cranial cavity per se during the cardiac cycle, which increased the intracranial utilization of the energy of the cardiac output and contributed to the outflow of venous blood from the cranium. The results suggest a beneficial effect of craniotomy on the physiological mechanisms of the circulatory and metabolic maintenance of the brain activity.     

Two-dimensional electrophoresis of cerebrospinal fluid proteins in normal and pathological conditions

The two-dimensional polyacrylamide gel electrophoresis technique has been adapted for the analysis of human cerebrospinal fluid proteins. Proteins were detected by Coomassie brilliant blue stain and/or by silver stain. Highly reproducible protein patterns were obtained. We analyzed ten normal CSF specimens, thirty pathological CSF specimens and the corresponding sera. We mapped the protein patterns observed by examination of serum/CSF differences and by immunofixation. Preliminary observations on the changes in protein patterns in CSF specimens from patients with neurological disorders are reported.     

Demonstration of prolactin flow into the cerebrospinal fluid of the alert rat in a pulsatile circhoral manner by push-pull cannulation of the 3d ventricle

In 8 male unanesthetized rats, sequential sampling of cerebrospinal fluid (CSF) from a push-pull cannula implanted into the 3rd ventricle revealed that prolactin was present in this fluid, where it displayed circhoral pulsatility resembling the temporal variations in plasma prolactin observed in the same animals. Although basal prolactin levels were lower in the CSF than in the plasma, the amplitude of the circhoral prolactin pulses was twice as great in the CSF as in the plasma compartment. The possible origin and role of CSF prolactin are discussed.     

Relation between resorption resistance of cerebrospinal fluid and the degree of intracranial pressure]

Changes in the CSF resorption resistance in relation to the value of the intracranial pressure have been assessed in 44 cats. Changes in the intracranial pressure have been produced with fluid infusions. Between 1 to 5 infusion tests with the rate 0.012-1.8 ml/min have been performed in each animal. A relationship between CSF resorption resistance and intracranial pressure has been found. With an increase in the intracranial pressure CSF resorption resistance increased to maximum value of 34 kPa/ml per minute (255.6 mm Hg/ml per minute) at pressure 2.96 +/- 0.69 kPa (22.2 +/- 5.2 mm Hg). At the intracranial pressure about 6.7 kPa (50 mm Hg) CSF resorption resistance rapidly decreased to the value of 13.9 kPa/ml per minute (104 mm Hg/ml per minute). Later, changes have been rather slight. It is possible, that the breaking point at 6.7 kPa corresponds to the mobilisation of all ways of CSF evacuation.     

Blocking cerebrospinal fluid absorption through the cribriform plate increases resting intracranial pressure

Cerebrospinal fluid (CSF) drains through the cribriform plate (CP) in association with the olfactory nerves. From this location, CSF is absorbed into nasal mucosal lymphatics. Recent data suggest that this pathway plays an important role in global CSF transport in sheep. In this report, we tested the hypothesis that blocking CSF transport through this pathway would elevate resting intracranial pressure (ICP). ICP was measured continuously from the cisterna magna of sheep before and after CP obstruction in the same animal. To block CSF transport through the CP, an external ethmoidectomy was performed. The olfactory and adjacent mucosa were removed, and the bone surface was sealed with tissue glue. To restrict our analysis to the cranial CSF system, CSF transport into the spinal subarachnoid compartment was prevented with a ligature tightened around the thecal sac between C1 and C2. Sham surgical procedures had no significant effects, but in the experimental group CP obstruction elevated ICP significantly. Mean postobstruction steady-state pressures (18.0 +/- 3.8 cmH(2)O) were approximately double the preobstruction values (9.2 +/- 0.9 cmH(2)O). These data support the concept that the olfactory pathway represents a major site for CSF drainage.     

Physical characteristics in the new model of the cerebrospinal fluid system

It is unknown which factors determine the changes in cerebrospinal fluid (CSF) pressure inside the craniospinal system during the changes of the body position. To test this, we have developed a new model of the CSF system, which by its biophysical characteristics and dimensions imitates the CSF system in cats. The results obtained on a model were compared to those in animals observed during changes of body position. A new model was constructed from two parts with different physical characteristics. The "cranial" part is developed from a plastic tube with unchangeable volume, while the "spinal" part is made of a rubber baloon, with modulus of elasticity similar to that of animal spinal dura. In upright position, in the "cranial" part of the model the negative pressure appears without any measurable changes in the fluid volume, while in "spinal" part the fluid pressure is positive. All of the observed changes are in accordance to the law of the fluid mechanics. Alterations of the CSF pressure in cats during the changes of the body position are not significantly different compared to those observed on our new model. This suggests that the CSF pressure changes are related to the fluid mechanics, and do not depend on CSF secretion and circulation. It seems that in all body positions the cranial volume of blood and CSF remains constant, which enables a good blood brain perfusion.