Sliding the transducer up and down the forearm helps verify that the structure is the ulnar nerve by following the course of the ulnar artery and looking for the nerve on its ulnar side.įrom the Compendium of Regional Anesthesia: Cognitive priming for a radial nerve block at the level of the wrist.Ī wrist nerve block results in anesthesia of the entire hand, except the territory of the deep branch of the radial nerve. Scanning proximally, these two structures can be easily differentiated.
At this location, the tendon of the flexor carpis ulnaris muscle can be seen superficial to the ulnar nerve. A linear transducer placed at the level of the wrist crease will show the hyperechoic anterior surface of the ulna with shadowing behind just lateral to the bone and very superficial will be the triangular or oval hyperechoic ulnar nerve, with the pulsating ulnar artery immediately next to it ( Figures 4 and 5). The ulnar nerve is located medially (ulnar side) to the ulnar artery from the level of the mid-forearm to the wrist this provides a useful landmark. Tilting the transducer slightly will make the nerve appear alternately brighter (more contrast) or darker (less contrast) with respect to the background.
In many instances, however, it is much simpler to perform a median nerve block at the midforearm, where the nerve is easier to recognize. The tendons will have disappeared on the image, leaving just muscle and the solitary median nerve ( Figures 2 and 3), which then can be carefully traced back to the wrist, if desired. At this location, it is easy to confuse the tendons for the nerve and vice versa for this reason, it is recommended to slide the transducer 5–10 cm proximally the volar side of the forearm, to confirm the location of the nerve. A linear transducer placed transversely at the level of the wrist crease will reveal a cluster of oval hyperechoic structures, one of which is the median nerve. As the muscles taper toward tendons near the wrist, the nerve assumes an increasingly superficial position until it is located beneath the flexor retinaculum in the carpal tunnel with the tendons of the flexor digitorum profundus, flexor digitorum superficialis, and flexor pollicis longus. The median nerve crosses the elbow medial to the brachial artery and courses toward the wrist deep to the flexor digitorum superficialis in the center of the forearm. Three individual nerves are involved in a wrist nerve block: the median, ulnar, and radial nerves. In addition to providing anesthesia and analgesia, wrist nerve blocks using botulinum toxin to treat hyperhidrosis have been described. Since the nerves are located relatively close to the surface, this is a technically easy nerve block to perform, but knowledge of the anatomy of the soft tissues of the wrist is essential for successful block with minimum patient discomfort. Traditional wrist nerve block technique involves advancing needles using surface landmarks toward the three nerves that supply the hand: the median, ulnar, and radial nerves. The wrist nerve block is an effective method to provide anesthesia of the hand and fingers without the arm immobility that occurs with more proximal brachial plexus nerve blocks. Transducer and needle positions for (A) median nerve block (B) ulnar nerve block (C) radial nerve block.