subkostalnerve

The subcostal nerve, also known as the subcostal nerve or T12 nerve, is the last anterior rami of the thoracic spinal nerves. It originates from the ventral ramus of the twelfth thoracic vertebra. Unlike the other intercostal nerves, the subcostal nerve is not truly an intercostal nerve because it does not run between the ribs. Instead, it courses inferolaterally, passing posterior to the lateral arcuate ligament of the diaphragm and then anterior to the quadratus lumborum muscle. It then runs anteriorly and laterally, passing deep to the transversus abdominis muscle.

The subcostal nerve innervates the skin of the abdominal wall below the umbilicus, specifically the hypogastric region. It also provides motor innervation to some of the abdominal muscles, including the transversus abdominis and internal oblique muscles. Additionally, it may contribute sensory innervation to the peritoneum in the upper part of the inguinal canal. Due to its anatomical course, the subcostal nerve can be susceptible to injury during abdominal surgery, particularly procedures involving the lower abdomen or flank. Symptoms of subcostal nerve injury can include localized pain, altered sensation, and weakness in the abdominal muscles.