Emergence and distribution of the ilioinguinal nerve in the inguinal region: applications to the ilioinguinal anaesthetic block (about 100 dissections)

Abstract

The variations in the emergence and distribution of the ilioinguinal nerve are the cause of the failures of the ilioinguinal block and the difficulties at interpreting the ilioinguinal nerve syndrome. In order to identify its variations and set reliable anatomical landmarks for performing the ilioinguinal block, we dissected 100 inguinal regions of 51 adult corpses. The nerve was absent in seven cases and double in one case. The ilioinguinal nerve emerged from the internal oblique muscle, passing at 1 +/- 0.8 cm of the inguinal ligament and 3.33 +/- 2 cm of the ventral cranial iliac spine. It appeared behind the inguinal ligament and/or the ventral cranial iliac spine in 19 cases and presented a common trunk with the iliohypogastric nerve in 13 cases. In 47 cases, the nerve appeared in the form of a single trunk. Sixteen modes of division and eight types of predominantly anterior scrotal topographic distribution could be noted. These results show the high variability of the emergence and the sensory distribution of the ilioinguinal nerve. They enable us to propose techniques for ilioinguinal block performance using more accurate anatomical landmarks formed by the inguinal ligament and the ventral cranial iliac spine and a better diagnostic approach of ilioinguinal neuropathies.

Essentials of Our Current Understanding

“…Although this is true in the majority of individuals, there is significant variability, with up to 20% having origins from the L2 and L3 nerve roots. [14][15][16] Both nerves emerge at the lateral border of psoas major and run inferolaterally on the ventral surface of QLM and TAM, just superior and parallel to the iliac crest (Fig. 2).…”

“…The exact location at which the nerves pierce TAM and enter the TAP is variable, but this is usually in the region of the anterior third of the iliac crest rather than more posteriorly. 14,17,18 The iliohypogastric nerve enters the TAP earlier in its course than the ilioinguinal nerve, and in a significant number of individuals, the ilioinguinal nerve only enters the TAP very close to the ASIS (medial to the anterior axillary line). 9 Both nerves continue to ascend through the IOM and EOM to supply the abdominal wall in the inguinal and pubic regions.…”

“…They pierce the IOM at a variable distance medial to the ASIS (approximately 3 ± 2 cm medial to ASIS and 1 cm superior to inguinal ligament in adults. 14 The anatomic variability in their course contributes to the high failure rates for blockade of these nerves with the TAP block 19,20 and the landmark-guided techniques of II-IH block. 21,22 …”

Case study: Managing a case of ankylosing spondylitis for inguinal hernia repair

“…10 Ndiaye, Diop, Ndoye and Ndiyae have reported a high variation in the emergence and sensory distribution of the ilioinguinal nerve as a cause of the failure of an ilioinguinal nerve block. 13 In our case, as the placement of an LMA™ was unsuccessful, we decided to go ahead with the nasopharyngeal airway. We found the nasopharyngeal airway device (the endotracheal tube) easy to pass and that it required a lighter anaesthetic plane.…”

Pneumoperitoneum Does Not Influence Spread of Local Anesthetics in Midaxillary Approach Transversus Abdominis Plane Block

“…The variation in spinal contribution, emergence, and distribution of the ilioinguinal and iliohypogastric nerves has been well studied. 19,20 These studies also pointed to the frequent variability of the course of these nerves, which interconnect intensively and form plexuses in their intermuscular and intramuscular extensions and in the (sub)cutaneous region. This emphasizes the necessity of a profound anatomical knowledge to improve block success rate.…”