Feasibility of Real-Time Ultrasound for Pudendal Nerve Block in Patients with Chronic Perineal Pain

BACKGROUND AND OBJECTIVES: Compared with conventional fluoroscopic-guided pudendal nerve block, ultrasonography has potential advantages for visualizing anatomical landmarks such as the internal pudendal artery and nerve, the sacrospinous and sacrotuberous ligaments, and local anesthetic spread. We examined the clinical utility of performing pudendal nerve block under real-time ultrasound guidance. METHODS: Seventeen patients were studied. With the patient lying prone, a 2 to 5 MHz curved array ultrasound probe was placed at the level of the ischial spine to capture the transverse view of the ischial spine, the sacrospinous and sacrotuberous ligaments (SSL and STL), the internal pudendal artery (confirmed with color Doppler), and the pudendal nerve. A 22-gauge needle was advanced under real-time ultrasound guidance to reach the pudendal nerve in the plane between the STL and SSL. Following confirmation of spread of dextrose 5% solution in the interligamentous plane, a mixture of 5 mL 0.25% bupivacaine with 1:200,000 epinephrine and 40 mg Depo-Medrol (Pharmacia & Upjohn, Kalamazoo, MI) was injected. Assessment included the ease of identification of anatomical structures and local anesthetic spread with ultrasound, and the degree of sensory block in the perineum. RESULTS: The ischial spine, SSL, STL, internal pudendal artery, and pudendal nerve were easily identifiable with ultrasound in the majority of patients. Local anesthetic spread was seen as a hypoechoic collection around the nerve and expanding between the STL and SSL. All patients developed perineal sensory block following the procedure. CONCLUSIONS: Pudendal nerve block at the ischial spine level can be reliably performed under real-time ultrasound guidance.