[Diagnostic value of magnetic resonance imaging in postoperative maxillary cyst].

Magnetic resonance imaging (MRI) is superior to conventional X-ray tomography and CT scanning in detecting postoperative maxillary cysts (POMCs). We analyzed the MRI features of 51 cases (72 sides) and compared them with the operative findings of 42 cases (52 sides) of POMC. The total number of cysts diagnosed was 121. Multiple cysts were found in 37 sides (51%) and bilateral cysts were found in 21 cases (45%). According to classification of POMC based on location in the maxilla the central cysts were found in only 38% of all cysts (peripheral ones in 62%). In the 42 patients operated on, 69 of 83 cysts which had been detected by MRI were confirmed, whereas there were two additional cysts which could not be diagnosed preoperatively. Sixty four of 71 cysts were opened to the nasal cavity under endonasal endoscopic control. The other seven cysts (five sides) were operated on via a buccogingival incision. Detailed and accurate diagnosis by MRI and development of endoscopic instruments enabled endonasal surgery in most (91%) sides of the POMC. In five cysts of the superior type which are small isolated and distant from the lateral wall of the nasal cavity, endoscopic endonasal surgery was not indicated. In conclusion, MRI for POMC was extremely helpful in selecting a surgical approach.