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In 39 patients with intracranial lesions the resorption resistance was measured using an own computerized infusion test. A high usefulness of this test was demonstrated in the diagnosis of hydrocephalus and for establishing indications to ventriculocardiac valve implantation. In patients after craniocerebral injuries a rise was observed of the resorption resistance immediately after trauma in cases with subarachnoid haemorrhage. Later on, this resistance decreased gradually reaching a stable value after 1-2 years. Data obtained in the infusion test make possible establishing of optimal intracranial pressure and choice of an appropriate valve. The determination can be performed intraoperatively.

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Biophysical aspects and the method of the Computerized Infusion Test (CIT) developed in the Neurosurgical Clinic of the Medical Research Center, Polish Academy of Sciences, are presented. The CIT is a development of classical methods of estimating the cerebrospinal fluid outflow resistance. It is based on a clinically tested mathematical model of the intracranial pressure-volume compensating mechanisms. The CIT enables the etrapolation of the infusion curve in cases when it is impossible to reach the upper steady during the constant infusion test because of the ICP exceeding values estimated as being critical.

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We studied the effects of two commonly employed antiedema agents, mannitol and furosemide, on CT brain density in eight patients with primary and metastatic brain tumors. Noncontrast CTs were performed before and after IV furosemide or IV mannitol, and serial blood samples were analyzed for osmolality. Computer-generated frequency histograms of CT numbers from "before-and-after" brain slices were using quantile-quantile (QQ) plots and the Kruskal-Wallis statistic. After IV mannitol, there was a progressive increase in CT brain density, which corresponded to an upward shift in the QQ plot over the range 0 to 70 Hounsfield units. The differences between baseline and posttreatment histograms for mannitol patients were significantly different from controls, and maximum differences coincided with peak serum osmolality. No statistically significant effects were observed in the furosemide group despite maximal diuresis. The relative magnitude of the quantitative changes observed after mannitol and furosemide administration are consistent with anticipated changes in brain water content.

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The role of changes in CSF inflow in patients without intracranial pathology has been studied. The CSF outflow resistance has been calculated, by dividing the CSF pressure rise by the speed of intrathecal saline infusion. The average CSF pressure rise produced during infusion test (infusion 2 ml/min) amounted to 11.15 mmHg. The calculated CSF outflow resistance equaled to 5.58 +/- 1.1 mm Hg/ml/min. On-line computer assisted analysis during infusion test helps to shorten the procedure and makes it more precise.

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An index of intracranial pressure instability is calculated as a new way to evaluate the capacity of intracranial voluminal compensation in patients suffering from cranio-cerebral trauma. The value of the index is determined by mutual relations of intracranial pressure standard deviations measured during 3-minute periods before and after intracranial administration of 2 ml of 0.9% NaCl. Normal physiological range of the index was evaluated in controls without intracranial pathology.

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The authors describe a fast method for estimating the elastance of the intracranial system in man. The method consists in constructing the so-called amplitude-pressure (Amp-P) curve which describes the relationship between the amplitude of pulse-related oscillations in cerebrospinal fluid pressure and the basic level of intracranial pressure. The Amp-P curve consists of two straight lines, and the point of intersection of these lines is thought to indicate the intracranial pressure level at which there occurs a qualitative change in the functioning of compensatory mechanisms of the intracranial system. The authors applied the method to examine the Amp-P curves of 10 patients without intracranial pathology and found that they provide a good description of the state and dynamics of the intracranial system. Preliminary data obtained in patients with intracranial pathology indicate that the method is a valuable tool in the diagnosis and treatment of neurosurgical patients.

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Extracranial hypertension was produced in cats by means of epidural compression with a baloon. After 2 hours of compression sudden decompression was performed and tissue pressure was compared at symmetrical sites of cerebral hemispheres with cerebrospinal fluid pressure measured in the cisterna magna. It was found that symmetrical tissue pystem, which was due probably to early oedema developing in the compressed area.

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A new method of estimating intracranial decompensation in man is described. An on-line computer system is connected to an intracranial pressure (ICP) monitoring system to compute regression plots of mean ICP vs standard deviation; standard deviation is used as a measure of ICP instability. Two zones with distinctly different slopes are a characteristic feature of these plots. It is thought that the changes of slope signify intracranial decompensation.

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A specialized neurosurgical data acquisition and processing system was developed and applied in practice to monitor some 60 patients after head injury or neurosurgical operations. At first the system allowed off-line operation, and the experiences thus gained made it possible to implement the system in its present form for real-time on-line patient monitoring. The algorithms prepared in our laboratory allow rapid and concise presentation of results and have proved their usefulness in clinical practice. The main parameters of interest in neurosurgery are intracranial pressure (ICP) and the volume of cerebrospinal fluid (CSF) drained from one of the lateral ventricles. Examples of statistical analysis of both these variables, and their presentation in the form of tables, diagrams and histograms are given.

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The authors describe a system for rapid digital automatic recording of cerebrospinal fluid pressure. The results are recorded in numerical form by a recorder. Owing to this quantitative expression of results the subjective evaluation of analog curves is avoided. The system may be used also to measure other slowly changing physiological processes.

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The effect of prolonged mannitol infusion upon intraventricular pressure was investigated with the aid of a specially-designed automatic digital recording system; the data recorded were processed off-line by a minicomputer. The character of the pressure curves is thought to result from interaction between the mannitol effect and the observed system's shifting equilibrium position, which is caused by other factors. The character of the pressure curves prior to mannitol infusion must be taken into consideration in estimating the actual effect of the drug; the authors suggest that in certain cases it might be possible to decrease further the rate of mannitol administration. The advantages of statistical approach to the evaluation of intracranial pressure variations are discussed.

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