Pursuing an alternative access route for transvenous embolization of cavernous sinus dural arteriovenous fistulas can be challenging in patients with an occluded inferior petrosal sinus. We found that cannulation of even a completely occluded inferior petrosal sinus is feasible, especially when using a standard hydrophilic-polymer-jacketed 0.035-inch guidewire as a frontier-wire for probing. From 2002 to 2017, the frontier-wire technique was tried in 52 patients with occluded inferior petrosal sinuses for transvenous embolization of cavernous sinus dural arteriovenous fistulas at our center. Technical success was defined as access into the affected cavernous sinus compartment with a microcatheter through the occluded inferior petrosal sinus and deployment of at least 1 coil. The complications and treatment outcomes were analyzed. The frontier-wire technique was applied in 52 patients with 57 occluded inferior petrosal sinuses (52 ipsilateral and 5 contralateral inferior petrosal sinuses). Technical success rates were 80.8% (42/52) of patients and 73.7% (42/57) of inferior petrosal sinuses. Alternative transvenous routes were used in 3 patients, and transarterial access was used in 7 patients. Complete embolization of fistulas was achieved in 82.2% (37/45) of patients in the transvenous embolization group and in 14.3% (1/7) of patients in the transarterial group. No procedure-related morbidity or mortality was observed. Transvenous embolization of cavernous sinus dural arteriovenous fistulas, even through a completely occluded inferior petrosal sinus, is feasible. The difficulty of passing the microcatheter can be minimized by prior probing of the occluded inferior petrosal sinus using a standard 0.035-inch guidewire; the trace of the guidewire on the roadmap image serves as a guide for microcatheter navigation through the inferior petrosal sinus on fluoroscopy.