MR-guided perineural injections of the ganglion impar

Perineural ganglion impar injections are used in the management of pelvic pain syndromes due to various malignant and benign pathologies. There is no consensus regarding the optimal image guidance for this procedure. Magnetic resonance (MR) imaging provides excellent soft tissue contrast and the potential to directly visualize and target the ganglion impar with the added benefit of no ionizing radiation. However, there are no scientific studies which have assessed this technique. The purpose of this study was to assess the feasibility of MR-guided percutaneous perineural ganglion impar injections using image overlay navigation. The data for 6 MR-guided ganglion impar injections performed in 6 nonembalmed, full torso human cadavers was reviewed. The procedures were performed with a clinical 1.5-Tesla MRI system and image overlay navigation. MR-compatible 20-gauge needles of different length were used based on the cadaver size. After location of the needle tip position was assessed, 3 cc of Gadolinium-DTPA-enhanced saline were injected under real-time MR imaging monitoring. The location of the injectant was assessed on T1-weighted, fat suppressed turbo spin echo images. Procedure time, number of intermittent MR imaging control steps required to place the needle, target error between the intended and final needle tip location, and inadvertent punctures of non-targeted vulnerable structures were determined. The gangion impar was visualized and accurate needle placement were technically feasible in all (6/6, 100%) cadavers. An average of 3 MR imaging control steps (range, 2-6) were required to complete the injections. The average target error was 2.2 ± 2.1 mm (range, 0.1-4.5 mm) [coefficient of variance: 9.3 ± 5.1%; range, 0.8-15.1%]. No punctures of non-targeted vulnerable structures occurred. The median procedure time was 20 minutes (range, 12-29). MR guidance can visualize and directly target the ganglion impar for accurate needle placement and successful periganglionic injection with the additional benefit of no ionizing radiation exposure to patient and staff. Our results support further evaluation with clinical trials.