Cerebrospinal Fluid Movement Research Articles

Errors in velocity measurement by the Pitot principle in fluids with slowly propagated pressure waves

An attempt has been made to develop a velocity probe using the Pitot principle for the measurement of fluid velocities in cerebrospinal fluid. Pressures were measured using conventional transducers and amplifiers and the pressure difference signal has the predicted relationship to the square of fluid velocity in the steady state. However, in the clinical situation where slowly propagated pressure waves accompany cerebrospinal fluid movement the pressure difference incorporates an indeterminate term unrelated to velocity, and this imposes severe limitations on the technique. Measurements and discussion are presented.

Evaluation of the central canal of the spinal cord in experimentally induced hydrocephalus.

The central canal of the spinal cord has been proposed as a significant compensatory alternative pathway of cerebrospinal fluid (CSF) flow in hydrocephalus. Ten dogs were made hydrocephalic by a relatively atraumatic experimental model that simulates the human circumstance of chronic communicating hydrocephalus. The central canal was studied by histopathology and compared with 10 normal control dogs. In both groups the central canal of the spinal cord was normal in size, configuration, and histological appearance. In this experimental model dilatation of the canal and increased movement of CSF does not appear to be a compensatory alternative pathway.

The Central Canal of the Spinal Cord in Experimental Hydrocephalus: Preliminary Results

The central canal of the spinal cord in certain animal species has been shown to be an alternative pathway of cerebrospinal fluid flow in experimentally induced hydrocephalus. Enlargement and increased movement of cerebrospinal fluid in the central canal has been proposed as a compensatory mechanism in hydrocephalus in humans. The central canal of the spinal cord was normal in 5 dogs and 2 primates made hydrocephalic by a relatively atraumatic experimental model which simulates the human disorder to chronic communicating hydrocephalus. Dilatation of the central canal is apparently not an important compensatory alternative pathway.

THE PATHOLOGY OF EXPERIMENTAL OBSTRUCTIVE HYDROCEPHALUS

Acute hydrocephalus was produced in newborn rabbits by the injection of kaolin into the cisterna magna. The light microscopic changes which occurred in the ependyma and periventricular brain tissue were studied. Some animals also received intraventricular injection of Evans blue albumin (EBA) at various times after the kaolin injection to study the permeability of the ependymal lining. There was a progressive dilatation of the lateral ventricles from the second day after the kaolin injection. Marked hydrocephalus was seen after 2 weeks. The white matter of the cerebral hemispheres showed increasing reduction in volume with the degree of hydrocephalus. No destruction of brain tissue, macrophage response, or inflammation were seen. The ependyma adapted remarkably well to the increased intraventricular pressure by extensive flattening and stretching. Apart from occasional and inconstant ruptures at the sites of the ventricular coarctations, no convincing breaks or defects of the ependymal lining were seen. There was a patchy spongy zone beneath the ependyma, possibly indicating oedema of the periventricular white matter due to transventricular movement of cerebrospinal fluid (CSF). Denudation of the ependymal lining is not necessary for the concept of transventricular flow of CSF. No difference was seen in the penetration of EBA into the periventricular tissue between hydrocephalic and control animals. The reduction of the cerebral mantle thickness was probably caused by simple pressure atrophy. This indicates that the changes may to a large extent be reversible if the hydrocephalus is treated within reasonable time.

Autoradiographic observations in experimental communicating hydrocephalus.

To study alternative pathways of cerebrospinal fluid movement and absorption in chronic communicating hydrocephalus, autoradiographs were performed on animals in which cisternograms had confirmed that chronic communicating hydrocephalus had been produced The autoradiographs showed transependymal migration of labeled albumin in the animals to such an extent as to suggest bulk flow. Radioactivity concentrated around the cerebral capillaries in the periventricular region. These findings correlated with the histologic changes of flattening and denudation of the ventricular ependyma and enlargement of the periventricular extracellular space. Transependymal absorption may explain the cisternographic patterns, periventricular edema, and some of the neurologic manifestations associated with chronic communicating hydrocephalus.

The evaluation of cerebrospinal fluid flow and absorption: clinical and experimental studies.

There is a basic alteration in cerebrospinal fluid (CSF) movement and absorption with the development of chronic communicating hydrocephalus. The transfer of radioactive albumin from the CSF space into the blood is delayed. — Ventricular entry associated with persistence (“stasis”) of the radiopharmaceutical corresponds with the syndrome of normal pressure hydrocephalus (NPH) and in clinical improvement with CSF diversionary shunts. As demonstrated by autoradiographic investigations the concentration gradient of radioactivity from the ependymal surface to depth in the periventricular area supports the concept that transependymal migration is an important mechanism of egress of CSF from the CSF space in communicating hydrocephalus.

Scanning electron microscopy of the third ventricle of sheep.

Scanning electron microscopy of the third ventricle of sheep demonstrates areas of ciliated ependymal cells at the dorsal and middle third. The cilia of the dorsal portion of the ventricle have biconcave discs that are attached to each cilium by a slender stalk. The lower third and floor of the ventricular wall, as well as the pineal recess, are largely covered by ependymal cells that possess numerous microvilli with only a few isolated cilia scattered along cell surfaces. The infundibular recess is papillated with apical blebs of the ependymal cells that project into the lumen of the recess. Measurements of these surface elements indicate an average diameter of 0.28 μ for cilia, 0.10 μ for microvilli and 0.50 μ for the apical blebs of the infundibular recess. The functional significance of the regional differences in surface structures is discussed in relation to cerebrospinal fluid movement, ependymoabsorption and ependymosecretion.

Distribution of intraventricular horseradish peroxidase in normal and hydrocephalic cat brains.

The distribution of intraventricularly injected horseradish peroxidase (HRP) was examined in the ependymal and subependymal tissue of both normal and experimental hydrocephalic cats by light and electron microscopy. At different time intervals after the intracisternal injection of kaolin, the hydrocephalic ventricles were perfused at various intraventricular pressures with mock cerebrospinal fluid (CSF) containing HRP. The uptake and localization of HRP by periventricular brain tissue was studied with respect to transventricular absorption of cerebrospinal fluid. The results of both light and electron microscopic studies have shown that in normal, acute or chronic hydrocephalic cats perfused at either high or low pressure the distribution of HRP is similar. The enzyme was localized mainly to the intercellular spaces, between ependymal cells, glial cells, and in perivascular spaces (in and across the basement membrane of subependymal blood vessels). HRP did not penetrate endothelial tight junctions even in chronic hydrocephalic cats undergoing significant rates of transventricular absorption of CSF. It is concluded that since the distribution of HRP in brain is determined by diffusion, its use as a tracer for the bulk movement of CSF through nervous tissue is limited. It is, however, an excellent extracellular space marker in electron microscopy.

Angiography and Cisternography in Acute Meningitis due toHemophilus influenzae

Two cases of Hemophilus injluenzae meningitis in infants are presented. In both cases, narrowing of vessels at the base of the brain and mUltiple small vessel occlusions of the middle and callosal systems were demonstrated at angiography, and acute communicating hydrocephalus was demonstrated by cisternography. Cisternography is a safe diagnostic technique that will demonstrate bulk movement of cerebrospinal fluid and changes associated with acute meningitis, thereby aiding in the selection of patients who may benefit from diversionary shunts.

Studies in the Movement of Isotopes RI131SA and Na24from Ventricular CSF Fluid

SUMMARYThe author discusses several experiments in tracing the bulk movement of cerebrospinal fluid in animals and in human subjects by the injection of radio‐active isotopes.

Transport of water and electrolytes between brain and ventricular fluid in the rabbit

Bidirectional sodium fluxes and net transfer of potassium, chloride, and water across the ventricular ependyma were studied in anesthetized rabbits by closed perfusion of the cerebral aqueduct and anterior fourth ventricle with solutions containing trace amounts of inulin- 3H and 22Na. Inulin dilution and clearance from the perfusate indicated a bulk fluid accretion of 0.37 μl min −1 cm −2 of ependymal surface. The concurrent net sodium movement into ventricular fluid occurred at a rate of .0645 ± .0060 μEq min −1 cm −2 against typical ventriculo-vascular potential gradients of 5–10 mv. Potassium entered the perfusate at concentrations approximating that of normal cerebrospinal fluid (CSF). Chloride accumulated in the ventricular system at a rate of .0356 ± .0057 μEq min −1 cm −2 and its distribution between blood and ventricular fluids approached an electrochemical equilibrium. Water was transported at reduced rates into hypotonic perfusates without associated changes in sodium influx, whereas, both water and sodium movements were inhibited by acetazolamide or cardiac glycosides. These studies imply that movement of CSF across the blood-brain-CSF barrier is an isotonic flow coupled to sodium transport and represents one-third of the total intraventricular formation of CSF.

Anatomy of the Anterior Choroidal Artery in the Dog

THE PRECISE role of the choroid plexus in the production and mass movement of cerebrospinal fluid (CSF) remains unsettled, and even the long-accepted interpretation of experiments conducted by Dandy in 1919 has been challenged. 1 Whatever role may be assigned to the choroid plexus, the blood supply of this vascular structure is critical. The detailed anatomy of the anterior choroidal artery, the major afferent vessel of the choroid plexus, has been described in man, but similar studies have not been reported in the dog, 2 the animal most commonly employed for the study of CSF circulation. The present study was undertaken to provide a description of the course and distribution of the anterior choroidal artery in the dog. Materials and Methods Normal brains from 50 adult mongrel dogs were examined. Both internal carotid arteries and the basilar artery were cannulated immediately after removal of the brain. A colored

Ependymal cilia: distribution and activity in the adult human brain.

Examination of 150 to 200 samples of the ependymal lining of the ventricles of nine adult human brains obtained 2(1/2) to 6 hours post-mortem revealed cilia in at least 20 separate sites in the four ventricular cavities. In seven of the brains ciliary motion was evident, and in two of these it was wide-spread and rapid. It seems likely that the adult human ventricular ependyma is ciliated throughout. Currents having distinct patterns are induced in the ventricles of animal brains by ciliary motion, and such currents probably exist in man. A local mechanism for the rapid movement of cerebrospinal fluid is therefore present.

Cervical spondylosis and compression of the spinal cord.

• Indentation of the cervical part of the spinal cord by protrusion of intervertebral disks and by osteophytic lipping produces varied neurological symptoms directly by mechanical injury and indirectly by effects on the movement of blood and cerebrospinal fluid. Diagnosis depends on cerebrospinal fluid manometry and myelography, for the symptoms may have more than one cause. In one case, the extensive paralyses in the patient were found to result from amyotrophic lateral sclerosis in addition to osteophytes that had caused marked narrowing of the disk space at the fourth and fifth cervical levels. In a second case, gross spondylotic changes in the cervical region coexisted with a sarcoma that was blocking the canal completely in the thoracic region. Laminectomy, with section of the dentate ligament, was done in six cases of chronic cord compression by cervical spondylosis. No improvement resulted in one case, and in two the results were hard to assess. But in three there was partial success, and two of these patients were relieved of symptoms and enabled to return to their occupations. This experience indicated that surgical treatment should be reserved for the patient in whom the symptoms are recent and rapidly progressing.