The Study of the Base of the Skull

Abstract

THE study of the base of the skull is certainly one of the most important elements in the investigation of intracranial disease and disease of the nasal accessory sinuses. I will make no attempt to review the enormous amount of literature bearing upon the roentgenographic studies of the skull and cranial cavity; and I will only refer to some of the more recent developments in technic, not even including the excellent work with lipiodol, but will confine myself especially to the general technic and the special information obtained from a study of the base of the skull. We must all realize that the recent work has been made possible only by the brilliant work of the authors who have preceded. My interest in the study of the accessory sinuses has extended over a period of twenty-five years, but Coakley and Caldwell were probably the first in this country to investigate the subject systematically, and Caldwell was the first to describe his technic, at the Annual Meeting of the American Roentgen Ray Society, at Niagara Falls, 1906. In discussing Dr. Caldwell's paper, I called attention to the importance of studying the accessory sinuses at various angles. Most roentgenologists who have taken special interest in the study of the nasal accessory sinuses must have recognized the changes which occur in the surrounding bony walls, but the importance of these pathological changes has been especially emphasized in the writings of Van Zwaluwenburg, Law, and Granger, as well as myself. Many of us think these changes are of more importance than the involvement of the mucous membrane. The early works in roentgen diagnosis of accessory sinus disease referred especially to the opacities in the cavities caused by exudate. In this respect we supplement and confirm the findings of the clinicians by their means of transillumination, but the roentgenologist who recognizes only the opacities misses much valuable evidence. Van Zwaluwenburg said: “We depend for our interpretation on the changes in the bony structures more than on the hazy opacities that are caused by the exudates and the soft tissue changes in the diseased pneumatic cells.” Granger called attention especially to the changes in the bones forming the roof of the sphenoid sinuses, and Law emphasized the importance of the changes in the walls of the ethmoid cells. Technic for Examination of Accessory Sinuses For the study of any of these changes in the bony structure of the walls, it is absolutely essential to have perfect roentgenograms, which show the finest detail. A fine focus tube, the smallest possible diaphragm that will include the sinuses and no more; absolute stillness of the patient and the tube will be important factors. A localizer such as I show in Figures 1 and 2 will assist in absolute direction of the central ray in relation to the accessory sinuses, and will permit the use of the smallest diaphragm.