We describe a case of transsphenoidal deflation of a detachable balloon after embolization of a carotid-cavernous fistula (CCF). The patient developed complete third and sixth nerve palsies immediately after detachable balloon embolization of the CCF, which was considered to be caused by cavernous sinus (CS) compression by the over-inflated balloon. We performed direct puncture of the balloon via the transsphenoidal route using a frameless neuronavigation system. Navigation-assisted transsphenoidal approach (TSA) is technically feasible for balloon deflation in cases of severe cranial nerve palsies due to an over-inflated balloon.