Subcostal Nerve (T12)

The lumbar plexus is formed from the anterior primary rami of T12, L1, L2, L3, and half of L4. The lumbar plexus distributes to the inguinal area, anterior abdominal wall, subinguinal area, anterolateral and medial thigh. The Subcostal nerve innervates the pyramidalis muscle, provides general sensation to the suprapubic area, and occassionally contributes to the lumbar plexus. Its large lateral cutaneous branch does not divide into anterior and posterior branches but passes downward over the crest of the ilium several centimeters behind the anterior superior spine of the ilium. This nerve distributes to the skin of the side of the hip.