33 Intercostal Block
Placement
Anatomy
Examination of an individual intercostal nerve shows that there are five principal branches (Fig. 33-1). The intercostal nerve contributes preganglionic sympathetic fibers to the sympathetic chain through the white rami communicantes (branch 1) and receives postganglionic neurons from the sympathetic chain ganglion through the gray rami communicantes (branch 2). These rami are joined to the spinal nerves near their exit from the intervertebral foramina. Also, shortly after exiting from the intervertebral foramina, the dorsal rami carrying posterior cutaneous and motor fibers (branch 3) supply skin and muscles in the paravertebral region. The lateral cutaneous branch of the intercostal nerve arises just anterior to the mid-axillary line before sending subcutaneous fibers posteriorly and anteriorly (branch 4). The termination of the intercostal nerve is known as the anterior cutaneous branch (branch 5)