Imaging of the larynx: current concepts

Abstract

Not every laryngeal abnormality requires imaging. If a lesion is small and there is no evidence of deep extension, the clinician can derive all visual examination. Similarly, when a lesion is large and obviously involves both true and false cords (transglottic), the clinician already knows that a total laryngectomy is necessary and imaging is of little value unless there is a question about nodal involvement. The real value of imaging is in the questionable cases in which a decision must be made about the feasibility of speech conservation therapy. The radiologist must understand the various conservation techniques and the key information needed to determine the feasibility of each. In cases in which patients are able to cooperate with the examination, MR with multiplanar imaging capabilities and increased tissue differentiation has, in my view, an edge over CT. However, many patients cannot cooperate, and in these cases CT provides a more consistently good examination. Some centers rely totally on CT and some rely completely on MR imaging units with low or middle field strength. Either can give excellent laryngeal imaging. At my institution, with a high-field-strength unit, MR imaging is the first choice if the patient is fairly cooperative and is thought able to undergo the examination. Even if the patient cannot tolerate the entire protocol, the examination usually provides enough necessary information. If the patient has major problems with secretions or has difficulty cooperating, we do not try MR imaging but use CT; the examination is almost always adequate even though restricted to one plane. The imaging modality used is less important than the radiologist's knowledge of the key anatomic landmarks. The most important landmarks, from a surgeon's perspective, are the ventricle, anterior commissure, and the cricoid cartilage. The structures most helpful in identifying the position of the ventricle are the paraglottic fat, the thyroarytenoid muscle, and the arytenoid cartilage. The clinician remains responsible for evaluating the mucosal surface. The goal of the radiologic examination is to find deep tumoral extension that the clinician cannot see.