Background Percutaneous microballoon compression (PMC) for trigeminal neuralgia (TN) is a well-established technique. However, complications from cannulating the foramen ovale (FO) have been reported because direct puncture of the FO is sometimes difficult. Here we report our experience with Dyna-CT-assisted PMC for TN in cannulating the FO and determining the position and volume of the balloon. Methods Dyna-CT-assisted PMC was performed for image reconstruction in 16 cases. The optimal working projection was generated and further fluoroscopic data were used to determine the relationship of the needle with the FO during puncture. The balloon position and three-dimensional shape were verified with Dyna-CT during balloon compression and the balloon volume and puncture angle were also calculated. Patients' prognosis is discussed. Results Dyna-CT allows quick, safe and easy cannulation of the FO. It provided three-dimensional images which were more elaborate than the classic 'pear shape' images for determining correct positioning in 16 cases. The volume of the inflated balloon ranged from 568.2 mm(3) to 891.4 mm(3) (average 769.5 mm(3)). The angle of introducing the cannula ranged from 15.32 degrees to 35.48 degrees rotation to the midline (average 25.18 degrees) and 38.47 degrees-51.89 degrees angulation to the Reid line (average 46.17 degrees). All the patients were pain-free after PMC. Four patients had resolvable masseter weakness and fine touch loss. No recurrence of TN was reported on follow-up. Conclusions Dyna-CT performed by digital subtraction angiography assists PMC in three ways: (1) the FO can be better visualized independent of the patient's position; (2) needle correction or insertion can be performed much more easily because of the direct fluoroscopic control; and (3) the needle position, balloon position, balloon configuration and the volume of the inflated balloon is more reliably determined. The use of Dyna-CT-assisted PMC has a low incidence of complications and a good prognosis.