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Ilioinguinal nerve: want to learn more about it?

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Ilioinguinal nerve

The ilioinguinal nerve is one of the final branches of the lumbar plexus. The lumbar plexus lies within the posterior aspect of the psoas major muscle and is formed by the first four lumbar ventral rami or the anterior divisions of spinal nerves L1-4. There also may be a contribution from the ventral ramus of the 12th thoracic spinal nerve (T12).

The lumbar plexus divides off to give 8 branches in total. The ventral ramus of L1 receives contributions from the ventral ramus of T12 before bifurcating. The upper and larger bifurcation then divides again to form two nerves.

This article will describe the anatomical course and function of the ilioinguinal nerve, followed by any clinical pathology.

Key facts about the ilioinguinal nerve
Origin Anterior divisions of L1-L4 spinal nerves
Course Upper lateral border of psoas major -> crosses quadratus lumborum and iliacus muscles -> enters transversus abdominis and internal oblique muscles -> spermatic cord
Functions

Sensory: Sensation to transversus abdominis and internal oblique muscles, anteromedial aspect of the thigh, skin over parts of the external genitalia

Motor: Actions of the transversus abdominis and internal oblique muscles

Clinical points Ilioinguinal nerve injury, entrapment and blocks

Anatomical course

The ilioinguinal nerve exits the psoas major at its upper lateral border inferior to the iliohypogastric nerve, the other nerve that originates from the first lumbar ventral ramus. It crosses the quadratus lumborum and iliacus muscles in an oblique direction before entering the transversus abdominus muscle near to the anterior aspect of the iliac crest.

It then enters the internal oblique muscle before crossing the inguinal canal posterior to the spermatic cord. The ilioinguinal nerve then emerges with the spermatic cord from the superficial inguinal ring to supply skin in the groin region.

Ilioinguinal nerve and posterior abdominal wall in a cadaver: The course of the ilioinguinal nerve can help you during dissections. If you follow it laterally, you will reach the plane of dissection between the internal oblique and transversus abdominis muscles.

Anatomical variation

The ilioinguinal nerve is smaller than the iliohypogastric nerve and is sometimes so small that it joins with the iliohypogastric nerve where it enters the quadratus lumborum. In this instance, a branch of the iliohypogastric nerve will then take its place. The ilioinguinal nerve can sometimes be absent and in this case, the iliohypogastric nerve will then supply its territory.

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Function

Sensory function

The nerve supplies sensory fibers to the transversus abdominus and internal oblique muscles. It also supplies the anteromedial aspect of the skin of the thigh, the skin covering the upper scrotum and the skin over the root of the penis in males or the skin over the mons pubis and labium majus in females.

Motor function

The ilioinguinal nerve also has motor fibres that innervate the transversus abdominus and internal oblique muscles.

More details about the ilioinguinal nerve are provided below:

Ilioinguinal nerve: Injury, entrapment and nerve block

The ilioinguinal nerve is susceptible to damage during abdominal surgery or from trauma to the abdominal wall. Injury to the ilioinguinal nerve can lead to a weakening of the transversus abdominus and internal oblique muscles, which can lead to the development of an inguinal hernia. Moreover, inguinal incisions carried out to repair inguinal hernias are a high-risk incision and may injure the ilioinguinal nerve. The nerve may also be damaged if it is included in the suture during incision closure causing nerve entrapment. Injury to the nerve can result in pain in the sensory distribution described above.

Both ilioinguinal nerve damage and entrapment during an inguinal hernia repair can lead to Post-Herniorraphy Pain Syndrome or inguinodynia, which is a chronic pain in the groin region lasting for greater than 3 months following inguinal hernia repair surgery, otherwise known as a herniorrhaphy. This can be treated with analgesia or physical therapy but these have been shown to have little effect. Ilioinguinal nerve block has been shown to be effective in reducing groin pain following herniorrhaphy. Nerve blocks can temporarily and reversibly block nerve transmission, leading to pain relief.

Local anesthesia administration between the layers of the transversus abdominus and internal oblique muscles, as well as between the internal oblique and external oblique muscles, can lead to temporary analgesia. The injection is placed 2cm medial and 2cm superior to the anterior superior iliac spine and can involve various chemical agents such as anesthetics, steroid, glycerol or alcohol.

Ilioinguinal nerve: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,235,643 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • A. Hakeem, V. Shanmugam: Current trends in the diagnosis and management of post-herniorraphy chronic groin pain. World J Gastrointest Surg. (2011), volume 3, issue 6, p. 73-81.
  • K.L. Moore, A.F. Dalley, A.M.R. Agur: Clinically Oriented Anatomy, 5th Edition, Lippincott Williams & Wilkins (2006), p. 207-10.
  • S. Standring: Gray’s Anatomy The Anatomical Basis Of Clinical Practice, 40th Edition, Elsevier Health Sciences UK (2008), p. 1967-9.

Author, review and layout:

  • Charlotte O'Leary
  • Shahab Shahid
  • Catarina Chaves

Illustrators:

  • Ilioinguinal nerve and posterior abdominal wall in a cadaver - Prof. Carlos Suárez-Quian
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