Study of Pudendal Nerve Location with Ultrasound

High resolution ultrasonography allows for depiction of all major nerves in the body. At the extremities and the neck linear array transducers with frequencies between 7 and 18 MHz are used to examine the superficial lying motor and sensory nerves. Within the nerve sheath axons are packed together in fascicles, which are wrapped into connective tissue and form parallel structures, which can reflect the ultrasound waves and, therefore, become visible. As all parallel structures according to the angle of impact of the sound waves nerves can be either bright (hyper-echoic) or dark (hypo-echoic). In contrary to the major nerves of the extremities the pudendal nerve is a rather thin nerve (0.6 to 6.8 mm), which may consist of separated trunks (2 trunks in 34.5 percent, 3 trunks in 6 percent) and is lying in deep topographical regions embedded in fatty tissue. So the nerve is not approachable with high frequency transducers on the one hand. On the other hand curved array transducers working on 2 to 5 MHz used for abdominal ultrasound can be used for depicting the most important site for pudendal nerve block, which is the course around the sacrospinous ligament an