Radiography of Normal Larynx

Abstract

RADIOGRAPHY of the larynx has been studied mostly by Continental workers. The “Atlas,” of Thost, probably represents the most important contribution so far presented. We would mention also Iglauer and Lange in this country. The present study was undertaken as a contribution to a subject somewhat neglected. The refinements of modern technic, permitting of a rapid exposure, have simplified the subject in a very decided manner. The larynx is capable of four types of movement: first, movements from the action of the muscles of the neck producing displacement of all the structures of the neck; second, displacement by the intrinsic and extrinsic muscles of the larynx; third, movements incident to respiration, and fourth, blurring due to the cardiac impacts transmitted by the carotids. For the successful elimination of these various types of movement, it is not sufficient to ask the patient to suspend respiration and keep as still as possible. It is necessary to employ flash exposures. Most of the studies which the writer has made have been accomplished with an exposure of a twentieth of a second, the exposure being made with the help of a relay circuit breaker actuated by an overload of the primary. The time of these exposures was verified by means of the timing top. Naturally, the maximum amount of information is gathered from a lateral exposure, the antero-posterior being of little value on account of the overlying shadows in the cervical vertebræ The lateral exposure may be made on a 5 × 7 film in a cassette with a narrow edge. A cassette of larger size with a wide edge is inconvenient and the wide edge will often cut off part of the tissues under examination. With a small 5 × 7 cassette the film can be accurately placed so as to show the shadows of the laryngopharynx, the larynx, the trachea for some two or three inches, the upper portion of the esophagus, and the cervical vertebræ. Usually, the amount of the trachea which can be shown will depend upon the body habitus, more difficulty being experienced with patients with a short neck. The skin target distance should be at least 30 inches, preferably 36 inches. In patients with a short neck and in cases where one desires to include as much of the trachea as possible, the larger cassette, an 8 × 10 or a 10 × 12, may be supported beyond the shoulder and the tube removed to a distance sufficient to minimize the enlargement. Incidentally this technic, introduced by Caldwell many years ago, is very successful in the demonstration of the cervical vertebræ. This second procedure is better carried out with the patient sitting up and grasping the seat of the chair so as to pull the shoulders down on each side as far as possible. The head should be supported in an erect position by a non-radiopaque pillow. It will be necessary to increase the length of the exposure to compensate for the greater distance.