Two patients with thyroid eye disease underwent inferomedial orbital decompression complicated by a cerebrospinal fluid (CSF) leak. One of the cases developed a postoperative pneumocephalus resolved with conservative measures. In the second case, the CSF leak was managed intraoperatively. In both patients, a computed tomography (CT) scan revealed a pronounced slope of the lateral lamella of the cribriform plate, forming an obtuse angle with its lateral bony extension. When this anatomical disposition of the olfactory fossa (OF) is present, the course of the anterior ethmoidal artery (AEA) is usually embedded in the skull base, and its foramen should not be taken as the upper limit of the transconjunctival ethmoidectomy. The shape and relative height of the olfactory fossa and fovea ethmoidalis, and the course of the AEA should always be assessed before transconjunctival medial decompressions.
Keywords: Fovea ethmoidalis; olfactory fossa; orbital decompression; thyroid eye disease.