2017 Volume 60 Issue 6 Pages 315-318
A 45-year-old female with severe Graves orbitopathy was treated with Orbital decompression. Half a year after the operation, she developed left Maxillary sinusitis. Medication lead to improvement, but we decided to perform endonasal endoscopic sinus surgery. It is because the ostium of the maxillary sinus is closed and there was a possibility of recurrence. Orbital decompression exposed the lamina papyracea and orbital floor, so the risk of injury to the orbit was very high. She was treated with endonasal endoscopic sinus surgery supported by Navigation system. Navigation system was very useful to prevent complications.