Anthony Marmarou

Pressure-Volume Considerations in Infantile Hydrocephalus

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.

The Time Course of Brain Tissue Pressure and Local CBF in Vasogenic Edema

Our results for tissue pressure show: 1. Resting brain tissue pressure is above atmospheric pressure and equal to cerebrospinal fluid pressure. 2. The ventricular fluid pressure provides a reasonable estimate (± 10 mm Hg) of the maximum brain tissue pressure. 3. Excluding impaction, the maximum brain tissue pressure gradients developed are transient, less than 10 mm Hg, and dissipate within 2 h. 4. With impaction, the brain tissue pressure tends to equilibrate with the compartmental CSF pressure.

Gradients of Brain Interstitial Fluid Pressure in Experimental Brain Infusion and Compression

Brain interstitial fluid pressure (BIFP) measured with a cotton wick catheter is different from and usually below cisterna magna pressure (CMP). BIFP gradients in the region of cold induced edema and emboli have been shown. The purpose of the present investigation was to study the biomechanics of local tissue pressure in response to modifying influences: the direct infusion of mock CSF into the cat’s deep white matter and the change of BIFP induced by balloon compression.

The Time Course and Distribution of Water in the Resolution Phase of Infusion Edema

Relatively little is known of the clearance mechanisms in the vasogenic form of brain edema. According to Klatzo7 the ingestion of the exudate by astrocytes and its digestion are the primary mechanisms involved in clearing the issue of edema fluid. Reulen et al14 postulated that the edema fluid follows a downhill pressure gradient by bulk flow and enters the ventricle where it is cleared by the CSF. The effectiveness of the clearance mechanism in acute and chronic stages of brain edema has not been resolved. Moreover, it has been suggested by Cserr5 and Bradbury2, that edema fluid that flows into the CSF from the brain interstitium may be cleared by a lympathic pathway. The importance of this route in clearance of edema is unclear.

Abnormal Brain Biomechanics in the Hydrocephalic Child

: Sixteen children with active hydrocephalus were studied using the Pressure Volume Index (PVI) technique to characterize neural axis compliance and the resistance to CSF absorption (Ro). Intracranial pressure for the series was 16.2 +/- 6.2/13.3 +/- 6.1 mm Hg. Measured PVI was twice that predicted for each child, indicating abnormally compliant systems. Ro was 7.8 +/- 1.7 mm Hg/ml/min, a three-fold increase above normal. There was no correlation between PVI and ventricular size. These studies indicate that the biomechanical properties of the brain and its coverings are altered by the hydrocephalic process in a way that encourages further accumulation of volume.

Behavioral reactions of newborns to speech-like sounds and their implications for developmental studies

Newborns exposed to a randomized sound battery containing speech-like sounds demonstrated a variety of behavioral reactions reflecting individual differences in personality and organization. Subjects who actively searched the environment for stimuli and showed prolonged vigilance episodes scored in the 90th percentile on the Denver Developmental Test when evaluated at later ages. Subjects who were remarked as inhibiting crying during their exposure to the experimental schedule later were described by their parents as “good” babies, while subjects who vocalized their displeasure during exposure were described far less favorably. These findings may have implications for developmental studies of mother-infant interactions.

An Evaluation of Static and Dynamic Properties of Tissue Pressure Catheters

The recent introduction of tissue pressure measurement using cotton wick devices has raised several questions in our laboratory regarding possible artifacts associated with cotton wick strain gauge systems. An analysis of the pressure sensing technique was initiated to resolve some of the problems associated with the manufacture and testing of cotton wick devices to insure uniform measurement characteristics.

A Compartmental Analysis of Compliance and Outflow Resistance and the Effects of Elevated Blood Pressure

Our studies of intracranial pressure dynamics have shown that the volume extensibility, or compliance, in combination with the resistance to drainage of CSF are major parameters which affect the rate of change and resting level of the ICP. The objective of this investigation was to examine how these parameters were distributed between cranial and spinal compartments. We hypothesized that in the cranial compartment, a shift of cerebral blood volume offers the only means of rapid compensation to sudden changes in CSF volume. A second objective, then, was to examine to what extent the compliance which would be affected by the degree of this vascular compensation, is influenced by changes in mean systemic blood pressure.