An alternative projection for fluoroscopic-guided needle insertion in the foramen ovale: technical note

Abstract

Puncture of the ganglion Gasseri through the foramen ovale and subsequent thermocoagulation, balloon compression, or glycerin injection is a well-established technique to treat trigeminal neuralgia. However, direct puncture of the foramen is sometimes difficult. Here, the authors present a simple technique of improved biplane fluoroscopic control for insertion of the needle into the foramen ovale. The authors evaluated an alternative oblique X-ray trajectory for the correct placement of a needle into the foramen ovale on cadaveric skull models. After determination of the ideal X-ray trajectory, 13 subsequent patients suffering from trigeminal neuralgia were subjected to intraforaminal needle placement with application of the alternative X-ray trajectory. An oblique projection with the X-ray tube (mean rotation 20.9° and angulations 28°) aligned coaxially to the inserted needle is proposed. On cadaver skull models, this oblique trajectory appeared to be ideal for visualization of the correct needle position. In the 13 patients, an immediate needle insertion into the foramen ovale was achieved under this direct oblique fluoroscopic control. No complications were observed. Experimentally and clinically, the new projection demonstrated three distinct advantages over the standard submental projection: Firstly, the foramen ovale can be better visualized independent of the patient's position. Secondly, needle correction or insertion can be performed much easier because of the direct fluoroscopic control. Thirdly, the correct needle position in the foramen ovale is more reliably determined than with the submental projection due to projection geometry. Further studies are needed to give evidence that the needle insertion into the foramen ovale is easier achieved with the coaxial projection than with the standard technique.