Orbital invasion in nasopharyngeal carcinoma: evaluation with computed tomography and magnetic resonance imaging

Ocular symptoms and tumor cranial nerve involvement are commonly observed in patients with nasopharyngeal carcinoma (NPC). These are primarily due to tumor invasion of the cavernous sinus and/or skull base, as direct tumor invasion of the orbit is very rare. This study was designed to assess computed tomography (CT) and magnetic resonance imaging (MRI) in documenting orbital invasion caused by NPC, with a special emphasis on the route of orbital extension.

A total of 562 patients with histopathologically prove NPC were examined using CT and/or MRI for tumor staging or post-treatment follow-up. We retrospectively reviewed CT and MRI findings to identify tumor invasion to orbital cavities and to evaluate the pathway of tumor spread.

Eighteen patients had tumor extension into the orbital cavities. Seventeen patients had ocular complaints. Fourteen of 18 showed unilateral orbital involvement and four patients showed bilateral orbital involvement. The route from the pterygopalatine fossa and inferior orbital fissure into the orbital cavities was the most common pathway of NPC invasion (n = 13), followed by ethmoid sinus and/or sphenoid sinus into the orbits (n = 4). In one patient, the route of orbital invasion was difficult to determine due to massive tumor extension.

Direct orbital invasion is rare in NPC. The pterygopalatine fossa and inferior orbital fissure are the most common routes of invasion, followed by invasion via the ethmoid and/or sphenoid sinuses. Coronal sections best show these findings on CT or MRI. Our study also shows that either CT or MRI provide essential information in documenting orbital invasion and determining the pathway of tumor spread.