Changes in Ventricular Size During and After Pneumoencephaloqraphy

Abstract

In the developmental phase of pneumoencephalography, an increase in the size of the lateral ventricles on twenty-fourhour films has been reported by several authors (1, 6, 7, 10). Others including Dyke and Davidoff (4), however, found no dilatation on late films. Dyke and Davidoff used helium for their examinations. Schatzki and his co-workers (13), employing air for encephalography, found the ventricles enlarged on the twenty-four-hour films in 23 out of 60 cases. They gave reasons why the ventricular measurement on the day of pneumoencephalography could represent the normal size, but arguments were more convincing that the larger twenty-fourhour measurement was the true size. Bronisch (1), on the contrary, believed that the larger late-film measurement did not reflect the usual ventricular size. Most of the patients in Schatzki's study had head injuries, and other authors (9, 11) also found twenty-four-hour ventricular dilatation in post-traumatic cases. These controversial reports raised at least two questions. Do ventricles change size during pneumoencephalography? If so, is it because of abnormal dilatation following the procedure or because of brain swelling during the examination? To resolve these questions, we began obtaining films at twenty-four hours and frequently at three, forty-eight, and seventy-two hours, first on a series of cases where air was used as the contrast medium and then in a consecutive series with oxygen the type of gas employed. We wished to see if the contrast agent influenced the ventricular measurements and we also hoped to find if changes in ventricular size occurred more often in patients who had distinct clinical disease. Method of Measurement In many of the pneumoencephalographic examinations in our series only a small amount of gas was used, and, since it had decreased considerably in amount by twenty-four hours, it was necessary to make the comparative measurements on the frontal horns with the head in the brow-up position. A single bifrontal measurement was recorded rather than measuring the ventricles separately, as frequently the septum pellicidum curves on late films if the gas is unequally distributed in the lateral ventricles. The study was carried out in several institutions, and to minimize any vagaries in target-film distance used by different technicians an index was made of the bifrontal horn measurement to that of the greatest external diameter of the skull (FH/xD). This is a modification of Evans' index which uses the greatest internal diameter of the skull. The latter is occasionally difficult to determine in adults. Because our index was used only to compare measurements on the same skull for immediate and twenty-four-hour films, variations due to the overall dimensions of the skull, whether mezo-, dolicho-, or brachycephalic, were minimized. Variations in position of the skull were not great and had little effect on the index.