Radiological and functional evaluation
MR examinations were performed using a 3.0T MRI scanner (Discovery 750W; GE Healthcare, Milwaukee, WI) equipped with a quadrature head coil. The MR sialographic visualization of salivary ducts was performed on each parotid gland before and after stimulation with a sialagogue. The MR sialography findings including duct visualization, sialectasis, main duct stenosis, and gland volume were reviewed using defined criteria. The largest diameter of the megaduct portion was measured on pre- and postoperative MR images, and the pre- and postoperative values were compared. Pre- and postoperative salivary excretory flow was compared between the two groups. The postoperative visualization of the distal duct beyond the stenotic portion was considered as improved excretory flow through the site of stricture. However, if the distal duct was not visualized with a sialagogue after surgery, it was considered as no improvement in saliva excretion.