Hello everyone! This is Nicole from Kenhub, and in this tutorial, we're going to be looking at the iliohypogastric nerve. So the iliohypogastric nerve which we can see here in green arises from the ventral or anterior ramus of the first lumbar nerve root, L1, of the lumbar plexus. And just to remind you, the lumbar plexus is this collection of nerves just here. And the iliohypogastric nerve arises initially with the ilioinguinal nerve as a single nerve root and this short common trunk soon divides into the iliohypogastric nerve and the ilioinguinal nerve at the lateral edge of the psoas major muscle. So, we can't see the psoas major muscle here but if we can imagine the edge here where the arrow is pointing then we have the ilioinguinal nerve in yellow and the iliohypogastric nerve in green.
The lumbar plexus is formed by the spinal nerves L1 to L4 and here we can see each of these roots L1, L2, L3 and L4 and lies posterior to the psoas major muscle as we can see in this image. So after branches from the common trunk, the iliohypogastric nerve emerges from the upper lateral border of the psoas major which is highlighted in very bright green here and courses obliquely in front of the quadratus lumborum muscle posterior to the kidneys, and it will be traveling in this direction as I'm pointing out here. So after that point, it then pierces the transversus abdominis muscle posteriorly just above the iliac crest and continues anteriorly between the transversus abdominis and the internal oblique muscles and on this image we can see the transversus abdominis muscle just here and the iliohypogastric nerve making its way just across it. And just to remind you, the transversus abdominis muscle is the deepest layer of our abdominal muscles so the internal oblique muscle will be traveling on top of that.
And so it's here that the iliohypogastric nerve divides into an anterior cutaneous branch and a lateral cutaneous branch. So the anterior cutaneous branch of the iliohypogastric nerve runs between the internal oblique muscle which we can see here in green and the transversus abdominis muscle which we can see here in green. And the anterior cutaneous branch of the iliohypogastric nerve innervates both of these muscles – so we can see that here in this image – as well as our superficial inguinal ring. It then continues through the internal oblique muscle 2 centimeters medial to the anterior superior iliac spine and passes through the external oblique muscle's aponeurosis about 3 centimeters superior to the superficial inguinal ring where it terminates by supplying the skin of the suprapubic region.
The lateral cutaneous branch of the iliohypogastric nerve arises above the iliac crest and it runs through the internal oblique muscle and the external oblique muscle posterior to the iliac branch of the twelfth thoracic spinal nerve T12. Now, this branch of the iliohypogastric nerve innervates posterolateral gluteal skin deep to the subcostal nerve.
So now we're going to talk about the iliohypogastric nerve's function. The iliohypogastric nerve provides sensory innervation and motor innervation. Let's review the structures it supplies. Sensory nerve fibers from the iliohypogastric nerve and its branches supply the internal oblique muscle, the external oblique muscle and the transversus abdominis muscle along with the suprapubic skin and the posterolateral gluteal skin. Motor nerve fibers of the iliohypogastric nerve and its branches supply the transversus abdominis muscle and the internal oblique muscle as well as the tendon formed from their common aponeurosis, the conjoint tendon.
And of course let's have a chat about the clinical significance of the iliohypogastric nerve. So injury or trauma to the iliohypogastric nerve may result in a burning pain in the suprapubic region and the inguinal region. These injuries can be treated through the injection of a local anesthetic and analgesic or with physical therapy. And so when would we be most likely to have an iliohypogastric nerve injury? Well, an iliohypogastric nerve injury may arise from a pelvic injury or during a surgical procedure, a sports injury and sometimes but very rarely in pregnancy. It's also important to note that injury to the iliohypogastric nerve is rarely isolated and therefore it can affect other nerves. The division of the iliohypogastric nerve above the level of the anterior superior iliac spine can result in the weakening of the posterior wall of the inguinal canal and that can lead to a predisposition to direct hernia formation.
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