Vishnu Deonarine

DIRECT IN VIVO OBSERVATION OF TRANSVENTRICULAR ABSORPTION IN THE HYDROCEPHALIC DOG USING MAGNETIC RESONANCE IMAGING

RATIONALE AND OBJECTIVES.A model of chronic noncommunicating hydrocephalus in canines was developed, and gadolinium- DTPA (Gd-DTPA)-enhanccd magnetic resonance imaging, physiologic and morphologic studies were performed to investigate transventricular absorption of cerebrospinal fluid. METHODS.Chronic hydrocephalus was induced in 12 mongrel dogs by injection of a silastic mixture into the prepontine cisterns. Ventricular pressure was measured during the development of hydrocephalus, and lateral ventriculo-ventricular perfusions with Gd-DTPA were performed under controlled conditions during serial magnetic resonance imaging studies. RESULTS.Hydrocephalus developed over an average of 129 ± 24 days after induction, and the intraventricular pressure increased from an initial level of 14 ± 4 cm H2O to a stabilized plateau of 25 ± 5 cm H2O. Increased signal intensity in the brain matter, as seen on magnetic resonance images of chronic hydrocephalic dogs perfused with Gd-DTPA in the lateral ventricles, was consistent with the presence of the contrast agent in the periventricular extracellular space. This increased signal intensity was not observed in control animals. CONCLUSIONS.These results provide direct evidence of transventricular absorption in chronic hydrocephalus.

Perfusion studies of the cerebrospinal fluid absorptive pathways in the dog.

Abstract Perfusion studies with Hypaque 75%, barium gelatin, and barium sulfate demonstrated the absorptive and filtrative functions of the arachnoid villi in dogs during life and immediately after death. Perfusion with artificial cerebrospinal fluid in sacrificed dogs at approximately the rate of CSF formation during life showed a pressure gradient between the cisterna magna and sagittal sinus of 6.8 cm water as compared to 5.8 cm in live dogs. These findings suggest that absorptive pathways function relatively normally for 1 to 2 hr. after death and that the absorptive pathways function as a passive filtration system.

The Rate of Cerebrospinal Fluid Formation Proximal and Distal to Aqueductal Obstruction in the Dog

The authors describe a stereotactic technique for producing aqueductal obstruction in dogs. Cerebrospinal fluid was collected proximal and distal to the occluded aqueduct for three hours. The choroid plexuses from all four ventricles were weighed. Each lateral ventricle plexus comprised approximately 18% of the total; the plexus of the third ventricle was 25.3%, and that of the fourth ventricle was 38.2%. The rate of fluid formation was not related to the weight of the choroid plexus, suggesting either (a) significant extrachoroidal sources of cerebrospinal fluid or (b) a functional difference between the choroid plexus of the fourth ventricle and those proximal to the aqueduct.

Measurement of the Rate of Cerebrospinal Fluid Formation in the Lateral Ventricles of the Dog

Abstract The lateral ventricles of 30 dogs were punctured at least 10 mm behind the foramen of Monro, and three different techniques were then used to isolate the fluid produced elsewhere in the ventricular system. The fluid formed in the lateral ventricles was aspirated and measured directly. The results showed formation at the rates of 0.0052 ml/min.; 0.0055 ml/min.; and 0.0051 ml/min., respectively.

Preparation of plastic mounted brain specimens

SummaryA technique is described for producing plastic embedded brain slices. These specimens are valuable teaching aids which may be viewed by reflected or transmitted light, with or without magnification. Vessels which contain clotted blood are clearly seen in these specimens.RésuméLes auteurs décrivent une technique pour réaliser des tranches de cerveau fixées sur matière plastique. Ces pièces sont une aide précieuse pour l’enseignement et peuvent être examinées par lumière réfléchie ou transmise, avec ou sans agrandissement. Les vaisseaux contenant des caillots sanguins sont clairement visibles sur ces pièces.ZusammenfassungEs wird eine Technik beschrieben, um Hirnschnitte plastisch einzubetten. Diese Schnitte sind von besonderem. Wert für die Lehre, sie können bei reflektiertem oder durchscheinendem. Licht betrachetet werden. Die Gefäße sind in den Schnitten sicher erkennbar.

Measurement of Total Cerebrospinal Fluid Formation Proximal to an Acute Cisternal Block

Abstract The posterior fossa and adjacent supratentorial subarachnoid cisterns of dogs were obstructed with Lipiodol Ascendant. This oily radiopaque material was introduced through a needle in the cisterna magna. The cerebrospinal fluid formed proximal to the cisternal block was collected by draining it from the cisterna magna at the original cisternal pressure and at zero pressure. The rates of formation of cerebrospinal fluid recorded at both pressure levels (0.053 ml/min. at initial pressure; 0.049 ml/min. at zero pressure) correspond well with cerebrospinal fluid measurements made by other methods.