High-resolution magnetic resonance-guided posterior femoral cutaneous nerve blocks.

OBJECTIVE: To assess the feasibility, technical success, and effectiveness of high-resolution magnetic resonance (MR)-guided posterior femoral cutaneous nerve (PFCN) blocks.

MATERIALS AND METHODS: A retrospective analysis of 12 posterior femoral cutaneous nerve blocks in 8 patients [6 (75%) female, 2 (25%) male; mean age, 47 years; range, 42-84 years] with chronic perineal pain suggesting PFCN neuropathy was performed. Procedures were performed with a clinical wide-bore 1.5-T MR imaging system. High-resolution MR imaging was utilized for visualization and targeting of the PFCN. Commercially available, MR-compatible 20-G needles were used for drug delivery. Variables assessed were technical success (defined as injectant surrounding the targeted PFCN on post-intervention MR images) effectiveness, (defined as post-interventional regional anesthesia of the target area innervation downstream from the posterior femoral cutaneous nerve block), rate of complications, and length of procedure time.

RESULTS: MR-guided PFCN injections were technically successful in 12/12 cases (100%) with uniform perineural distribution of the injectant. All blocks were effective and resulted in post-interventional regional anesthesia of the expected areas (12/12, 100%). No complications occurred during the procedure or during follow-up. The average total procedure time was 45 min (30-70) min.

CONCLUSIONS: Our initial results demonstrate that this technique of selective MR-guided PFCN blocks is feasible and suggest high technical success and effectiveness. Larger studies are needed to confirm our initial results.