Unexpected coil mass migration during transvenous embolization of a dural arteriovenous fistula resolved with guidewire-assisted snaring technique.

Endovascular embolization is a standard treatment for dural arteriovenous fistulas (dAVFs). Although it is considered relatively safe, intraoperative and postoperative complications can occur. Herein, a rare case of unexpected coil mass migration requiring a retrieval procedure during sinus occlusion for a transverse-sigmoid sinus dAVF (TSdAVF) is described. An 83-year-old man presented with worsening decline in cognitive function. Magnetic resonance angiography showed a TSdAVF. Since his symptoms seemed to be a result of the TSdAVF, transvenous embolization preserving the normal cranial venous circulation was planned. During sinus occlusion, including embolization of the shunted pouch of the TSdAVF, unexpected migration of the coil mass to the confluence of the superior sagittal sinus and the transverse sinus occurred. The migrated coil mass impeded venous circulation in the superior sagittal sinus. Since the presence of the coil mass at the confluence could have had catastrophic sequelae, the coil mass was retrieved using a guidewire-assisted snaring technique. Sinus occlusion was subsequently completed with repositioning of the coil mass at the target site. The TSdAVF resolved, with no recurrence confirmed for 1 year. Clinicians should be aware that coil mass migration can unexpectedly occur during sinus occlusion performed for treatment of a TSdAVF. The guidewire-assisted snaring technique might be effective in resolving this intraoperative complication.