Roentgenographic Examination of the Base of the Cranium in the Presence of Basal Tumors

Roentgenographic examination of the base of the cranium in the presence of a basal tumor more frequently yields practical results than would be anticipated if a judgment were to be based on the small number of articles on the subject appearing in the literature. Recognition of the changes that take place in such cases requires, to be sure, a thorough study and a comprehensive knowledge, particularly of the numerous variations that appear at the base of the cranium, which might easily give rise to false conclusions. The fact that a large number of skeletal parts of complicated structure lie one above the other on the plate, and, furthermore, are exceedingly variable in form, as is the case at the base of the skull, makes it of course much more difficult to get one's bearings. But the recognition of the various details of the roentgenogram and the interpretation of the whole will be possible if one forms the habit of working with a skull in hand, comparing constantly the roentgenogram and the skull, and learns to figure out on the skull the exact angle from which the roentgenogram was taken. Correct and appropriate technic in the taking of roentgenograms is a precondition of success and makes it possible to limit the roentgenograms to the actual number required, which is desirable not only for economic reasons but also in the interest of the patient, since every superfluous roentgenogram constitutes just so much needless annoyance. We must, therefore, have a clear idea from the start where we should look for changes, that is to say, where we most frequently find them, and how we can best demonstrate them. Such considerations will determine in each case the course of the examination. It has been our experience that, in the presence of basal tumors, our pathologic observations are made most frequently in the sella turcica, and secondarily in the pyramids. The third most frequent place of involvement is in the small wings of the sphenoidal bone, together with the optic canal, and fourthly, the great wings of the sphenoidal bone, together with the foramen spinosum, the foramen ovale, and the foramen rotundum. The Technic of the Examination In all cases in which the presence of a basal tumor is suspected, we must prepare, above all, two roentgenograms for the purpose of orientation, one in a frontal and one in a sagittal direction. While this statement may seem superfluous, experience has shown that it is necessary to emphasize this point. There are, to be sure, cases in which roentgenograms of a special part lead to an unequivocal result. However, one often finds in such special roentgenograms changes that he should not attempt to interpret other than in the light of observations made on the cranium as a whole, for the reason that such changes may constitute a local erosion as well as a variation.