Cystic masses in the floor of the mouth: value of MR imaging in planning surgery.

Abstract

The purpose of this study was to determine the value of preoperative MR imaging for planning the best surgical approach for excising cystic masses in the floor of the mouth. In addition, different sequences and slice orientations were compared in order to develop a standard MR examination technique for this purpose. Eleven patients with cystic masses in the floor of the mouth were prospectively examined with MR imaging after palpation and sonography. The imaging protocol included T1- and T2-weighted spin-echo sequences, both unenhanced and contrast enhanced. The exact topographic relationship of these cysts to the surrounding muscles and the value of different MR techniques were analyzed. The mylohyoid muscle, which serves 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 allowed the best visualization of anatomic details. Use of gadopentetate dimeglumine did not provide significant diagnostic information. Coronal and axial slices provided the best visualization of the topographic relationship of cyst and muscles. Sagittal slices were helpful only for midline lesions. In two cases, the choice between the intraoral and the cervical surgical approach was altered by MR imaging findings. MR imaging facilitates exact visualization of the location and extent of cystic lesions in the floor of the mouth and is useful for determining their relationship to the surrounding muscles. We conclude that MR imaging is an important adjunct to palpation and sonography in planning the best surgical approach.