2 – Transversus abdominis plane block

All thoracolumbar nerves that innervate the anterior abdominal wall travel as multiple mixed segmental nerves, which branch and communicate widely within the transversus abdominis plane (TAP) (1) anterolaterally (intercostal TAP plexus = Th6-Th9) (2) in plexuses that run with the deep circumflex iliac artery (DCIA) (classical TAP plexus = Th10-Th12) and (3) the deep inferior epigastric artery (DIEA) (rectus sheath plexus)

Segmental nerves Th6 to Th9 emerge from the costal margin to enter the TAP between the midline and the anterior axillary line

Th6 enters the TAP just lateral to the linea alba

Th7-Th9 emerge from the costal margin at increasingly lateral positions

Branches of Th9 emerge from the costal margin either medial or lateral to the anterior axillary line