High-Resolution ultrasound of the pudendal nerve: normal anatomy.

INTRODUCTION In this study we aimed to determine whether high-resolution ultrasound (US) can identify the pudendal nerve and its terminal branches. We also attempted to identify the best approach for visualizing these structures. METHODS Normal anatomy of the pudendal nerve was evaluated in 3 cadavers and 20 healthy volunteers proximally at the level of the ischial spine and distally with low-frequency (2-5-MHZ) and high-frequency (12-7-MHZ and 17-5-MHZ) transducers. Two musculoskeletal radiologists performed the examinations and evaluations. Volunteers were placed in 3 different positions, which allowed different approaches (posterior, medial, and anterior transperineal). A 0-3 scale was used to assess nerve visibility. RESULTS Visualization of the pudendal nerve at the ischial spine was best when using a medial approach (P < 0.004); the terminal branches were seen best with the anterior approach (P < 0.002). CONCLUSION High-resolution ultrasound (US) can identify the pudendal nerve and its terminal branches.