A 53-year-old man presented with a 1-week history of headache and double vision. On examination, he was found to have right cranial nerve III palsy. Computed tomography and magnetic resonance imaging of the brain showed a sellar mass with right cavernous sinus invasion. There was no evidence of anterior visual pathway compression on formal neuro-ophthalmologic examination. An elective endoscopic transsphenoidal adenectomy was performed. On access to the sphenoid sinus, he was noted to have a completely dehiscent posterior bony wall of sphenoid sinus with only a thin mucous membrane covering the sella, optic nerves, carotid arteries, and clivus (Figure 1). A focal area of mucosa was subsequently stripped from the posterior sphenoid sinus wall, and a micro-Doppler was used to localize the carotid arteries before sharp dural opening. The tumor was subsequently resected without complication. Failure to appreciate this uncommon anatomic variant (Figures 2 and 3) could result in disastrous irreversible carotid artery or optic nerve injury.