CYSTIC MASSES IN THE FLOOR OF THE MOUTH - VALUE OF MR-IMAGING IN PLANNING SURGERY

OBJECTIVE. The purpose of this study was to determine the value of pre operative MR imaging for planning the best surgical approach for excis ing cystic masses in the floor of the mouth. In addition, different se quences and slice orientations were compared in order to develop a sta ndard MR examination technique for this purpose. SUBJECTS AND METHODS. Eleven patients with cystic masses in the floor of the mouth were pro spectively examined with MR imaging after palpation and sonography. Th e imaging protocol included T1- and T2-weighted spin-echo sequences, b oth unenhanced and contrast enhanced. The exact topographic relationsh ip of these cysts to the surrounding muscles and the value of differen t MR techniques were analyzed. RESULTS. The mylohyoid muscle, which se rves as a key structure in determining the exact position of a cystic mass, was visualized in all cases. T2-weighted images facilitated the primary diagnosis of cystic lesions, whereas T1-weighted images allowe d the best visualization of anatomic details. Use of gadopentetate dim eglumine did not provide significant diagnostic information. Coronal a nd axial slices provided the best visualization of the topographic rel ationship of cyst and muscles. Sagittal slices were helpful only for m idline lesions. In two cases, the choice between the intraoral and the cervical surgical approach was altered by MR imaging findings. CONCLU SION. MR imaging facilitates exact visualization of the location and e xtent of cystic lesions in the floor of the mouth and is useful for de termining their relationship to the surrounding muscles. We conclude t hat MR imaging is an important adjunct to palpation and sonography in planning the best surgical approach.