OBJECTIVETo investigate the incidence, MRI characteristics and invasion route of nasopharyngeal carcinoma (NPC) infiltrating the cavernous sinus.

METHODSThe data of 141 patients with histologically proven NPC collected from May 2003 to June 2004 were reviewed. All patients were examined by 1.5-tesla superconducting MR unit to evaluate the tumor extent. MR FSE technique was used for T1 WI and T2WI images in the axial plane, followed by FSPGR fat-suppressed gadolinium-enhancement for T1WI images in the axial and coronal sections. All MR images were interpreted and evaluated by two diagnostic radiologists, paying particular attention to the nasopharynx and cavernous sinus infiltration.

RESULTSMR imaging showed infiltration of 49 cavernous sinuses in 39 patients (27.7%). The most common MRI features were enlargement of cavernous sinus with unconventional enhancement (22/49, 44.9%), even with formation of mass inside the sinus (9/49, 18.4%). The other MRI image features were local or diffuse dura mater thickening of cavernous sinus and presence of obscure structure as intra-sinus blurs and hazies inside. The most common infiltration route is through the foramen ovale (18/49, 36.7%), or through both the foramen ovale and foramen lacerum (6/49, 12.2%).

CONCLUSIONIn NPC patients, MRI invasion is characteristically and clearly shown as changes in the cavernous sinus. Possession of this information is crucial for giving correct treatment. The main infiltrtion route is through foramen ovale.