The article describes two cases of expansion of the posterior ethmoid cells deeply into the sphenoid body in combination with hypoplasia/aplasia of sphenoid sinus. In the first presented case, the sphenoethmoidal cell was in contact with the superior and posterior walls of the hypoplastic sinus. In the second case, the posterior ethmoidal cell was positioned next to the sinus, creating the illusion of its second half.
Large sphenoethmoidal cells can be easily confused with the sphenoid sinus. The presence of such anatomical variation of the ethmoidal labyrinth poses a significant risk of surgical complications including damage to neurovascular structures during transsphenoidal surgical approach to the structures of the skull base.
