Anatomical study of the iliohypogastric, ilioinguinal, and genitofemoral nerves using high-resolution ultrasound

Anatomical Variations of the Iliohypogastric Nerve: A Systematic Review of the Literature

Several anatomical variations of the iliohypogastric nerve branches have been observed in earlier studies. Knowledge of these variations is useful for the improvement of peripheral nerve blocks and avoidance of iatrogenic nerve injuries during surgeries. The purpose of this study was to perform a systematic review of the literature about the anatomical topography and variations of the iliohypogastric nerve. An extensive search on PubMed, Scopus, and Web of Science electronic databases was conducted by the first author in November 2021, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Anatomical or cadaveric studies about the origin, the course, and the distribution of the iliohypogastric nerve were included in this review. Thirty cadaveric studies were included for qualitative analysis. Several anatomical variations of the iliohypogastric nerve were depicted including its general properties, its origin, its branching patterns, its course, its relation to anatomical landmarks, and its termination. Among them, the absence of the iliohypogastric nerve ranged from 0 to 34%, its origin from L1 ranged from 62.5 to 96.5%, and its isolated emergence from psoas major ranged from 47 to 94.5%. Numerous anatomical variations of the iliohypogastric nerve exist but are not commonly cited in classic anatomical textbooks. The branches of the iliohypogastric nerve may be damaged during spinal anesthesia and surgical procedures in the lower abdominal region. Therefore, a better understanding of the regional anatomy and its variations is of vital importance for the prevention of iliohypogastric nerve injuries.

Sonoanatomy of the ilioinguinal, iliohypogastric, genitofemoral, obturator, and pudendal nerves: a practical guide for US-guided injections

The ilioinguinal, iliohypogastric, genitofemoral, obturator, and pudendal nerves are the major sensory nerves that may be involved in chronic groin and genital pain with a significant impact on the quality of life of patients. The diagnosis remains clinical, and US-guided diagnostic injections using an anesthetic may aid in confirming the clinical suspicion. The anatomy of the peripheral nerves can be successfully studied using imaging. High-resolution ultrasound is increasingly used in the clinical setting for visualizing small peripheral nerves, and magnetic resonance imaging provides an anatomical overview of the relationship between small nerves and surrounding structures. In this pictorial assay, we review the anatomy and clinical relevance of the ilioinguinal, iliohypogastric, genitofemoral, obturator, and pudendal nerves. We summarize the various techniques for ultrasound identification, and present the ultrasound-guided infiltration techniques for injecting the ilioinguinal, iliohypogastric, genitofemoral, obturator, and pudendal nerves. Corresponding magnetic resonance images and clinical photos of the probe placement technique are provided for anatomical correlation. This paper is aimed to serve as a practical technical guide for physicians to familiarize themselves with the ultrasound anatomy of the major inguinal sensory nerves and to enable successful ultrasound identification and ultrasound-guided diagnostic or therapeutic infiltrations for pain management of the ilioinguinal, iliohypogastric, genitofemoral, obturator, and pudendal nerves.

Ultrasound of Small Nerves

Nerve ultrasound has become an integral part of the diagnostic workup of peripheral neuropathies. Especially in the examination of small nerves, ultrasound provides superior image quality by using high frequency transducers. For a selection of small nerves, this article summarizes the local anatomy and common pathologies and offers simple instructions for determining their location with ultrasound including some cases with pathologies. This selection of nerves comprises the great auricular nerve, the supraclavicular nerves, the suprascapular nerve, the medial antebrachial cutaneous nerve, the lateral antebrachial cutaneous nerve, the palmar cutaneous branch of the median nerve, the long thoracic nerve, the intercostobrachial nerve, the posterior cutaneous nerve, the infrapatellar branch of the saphenous nerve, the medial calcaneal nerve, and the deep peroneal nerve at the ankle. Following our recommendations, these nerves can be swiftly located and tracked along their course to the site of the pathology.

Cutaneous nerve fields of the anteromedial lower limb-Determination with selective ultrasound-guided nerve blockade

BACKGROUND

This study aimed to determine the peripheral cutaneous nerve fields (CNF), their variability, and potential overlap by selectively blocking the intermediate (IFCN) and medial (MFCN) femoral cutaneous nerves and the infrapatellar branch of the saphenous nerve (IPBSN) in healthy volunteers.

METHODS

In this prospective study, ultrasound-guided nerve blockades of the IFCN, MFCN, and IPBSN in 14 healthy volunteers were administered. High-frequency probes (15-22 MHz) and 1 ml of 1% lidocaine per nerve were used. The area of sensory loss was determined using a pinprick, and all fields were drawn on volunteers' skin. A three-dimensional (3D) scan of all lower limbs was obtained and the three CNF and their potential overlap were measured.

RESULTS

The mean size of innervation areas showed a high variability of peripheral CNF, with 258.58 ± 148.26 mm² (95% CI, 169-348.18 mm² ) for the IFCN, 193.26 ± 72.08 mm² (95% CI, 124.45-262.08 mm² ) for the MFCN, and 166.78 ± 121.30 mm² (95% CI, 94.1-239.46 mm² ) for the IPBSN. In 11 volunteers, we could evaluate an overlap between the IFCN and MFCN (range, 4.11-139.68 ± 42.70 mm² ), and, in 10 volunteers, between the MFCN and IPBSN (range, 11.12-224.95 ± 79.61 mm² ). In only three volunteers was an overlap area found between the IFCN and IPBSN (range, 7.46-224.95 ± 88.88 mm² ). The 3D-scans confirmed the high variability of the peripheral CNF.

CONCLUSIONS

Our study successfully determined CNF, their variability, and the overlap of the MFCN, IFCN, and IPBSN in healthy volunteers. Therefore, we encourage physicians to use selective nerve blockades to correctly determine peripheral CNF at the anteromedial lower limb.

The inguinal region revisited: the surgical point of view : An anatomical-surgical mapping and sonographic approach regarding postoperative chronic groin pain following open hernia repair

PURPOSE

Inguinodynia or chronic post-herniorrhaphy pain, defined as pain lasting longer than 3 months after open inguinal hernia repair, has become the most important complication after inguinal surgery and therefore compromises the patient´s quality of life. A major reason for inguinodynia might be the lack of neuroanatomical knowledge and suboptimal "management" of the nerves during surgery.

METHODS

We present a detailed neuroanatomic mapping of the inguinal region by dissection including the most important surgical landmarks with all nerves confirmed by immunohistochemistry, ultrasound guided visualization of the iliohypogastric, ilio-inguinal, and genital branch of the genitofemoral nerve, and a practical (preoperative) algorithm for clinical management.

RESULTS

Surgically and ultrasonographically relevant structures ("landmarks") in open hernia repair are the anterior-superior iliac spine, pubic tubercle, Camper´s fascia (superficial layer of the superficial abdominal fascia), External oblique aponeurosis, Internal oblique muscle, Transversus abdominis muscle, superficial inguinal ring, external spermatic fascia, cremasteric fascia with cremaster muscle fibers, internal spermatic fascia, cremasteric vein (=external spermatic vein = "blue line"), ductus deferens, pampiniform plexus, inguinal ligament and the inferior epigastric vessels.

CONCLUSION

A detailed understanding of inguinal anatomy is an indispensable basic requirement for all surgeons to perform inguinal ultrasonography as well as open inguinal hernia repair, avoiding complications, especially postoperative inguinodynia.

Use of free sensate SCIA flap for reconstruction of distal limb defects of moderate size

Recent attempts have been made to direct the sensory neurotisation of free superficial circumflex iliac artery (SCIA) flaps. However, donor nerves enabling sensory recovery are limited. We report our findings in fifteen patients who underwent distal limb defect reconstruction using a sensate SCIA flap, including the lateral cutaneous branch of the subcostal nerve (LCSN), between August 2017 and September 2018. The distance from the anterosuperior iliac spine to the point where the LCSN crossed the iliac crest ranged between 6.5 and 10 cm. The diameter ranged between 1.5 and 4.0 mm. The flap size ranged between 8 × 4 and 13 × 10 cm². All of the flaps survived uneventfully. Tests of sensory modalities, including the Semmes-Weinstein (SW) touch, vibration, pinprick, temperature and static two-point discrimination (s2PD) tests were applied in nine regions of each flap post-operatively. One or more modalities were present in at least one region at 6 months post-operatively, and the recovery of vibration perception was more consistent than that of SW touch and pinprick perception. The recovery of s2PD was noted in 4 cases over a follow-up period of more than 12 months. A reliable sensate flap with the LCSN can be considered as an attractive option for the sensory reconstruction of distal limb defects of moderate size.

Ultrasound-Guided Microwave Ablation for the Management of Inguinal Neuralgia: A Preliminary Study with 1-Year Follow-up

PURPOSE

To evaluate the feasibility and efficacy of ultrasound-guided microwave ablation for the treatment of inguinal neuralgia.

MATERIALS AND METHODS

A retrospective review of 12 consecutive ultrasound-guided microwave ablation procedures was performed of 10 consecutive patients (8 men, 2 women; mean age, 41 years [range, 15-64 years]), between August 2012 and August 2016. Inclusion criteria for inguinal neuralgia included clinical diagnosis of chronic inguinal pain (average, 17.3 months [range, 6-46 months]) refractory to conservative treatment and a positive nerve block. Pain response-reduction of pain level and duration and percent pain reduction using a 10-point visual analog scale (VAS) at baseline and up to 12 months after the procedure-was measured. Nine patients had pain after the inguinal hernia repair, and 1 patient had pain from the femoral artery bypass procedure. The microwave ablation procedure targeted the ilioinguinal nerve in 7 cases, the genitofemoral nerve in 4 cases, and the iliohypogastric nerve in 1 case.

RESULTS

Average baseline VAS pain score was 6.1 (standard deviation, 2.5). Improved pain levels immediately after the procedure and at 1, 6, and 12 months were statistically significant (P = .0037, .0037, .0038, .0058, respectively). Also, 91.7% (11/12) of the procedures resulted in immediate pain relief and at 1 month and 6 months. At 12 months, 83.3% (10/12) of patients had an average of 69% ± 31% pain reduction. Percent maximal pain reduction was 93% ± 14% (60%-100%), and the average duration of clinically significant pain reduction was 10.5 months (range, 0-12 months.). No complications or adverse outcomes occurred.

CONCLUSIONS

Ultrasound-guided microwave ablation is an effective technique for the treatment of inguinal neuralgia after herniorrhaphy.

Predictive value of a diagnostic block in focal nerve injury with neuropathic pain when surgery is considered

OBJECT

In patients with focal nerve injury and neuropathic pain cutting the nerve to obtain permanent pain reduction can be considered. Surgery is indicated only if a diagnostic nerve block provides temporary pain relief. We evaluated the predictive value of a block on the outcome of surgery.

METHODS

In total, three blocks were performed at two week intervals. Patients were blinded to injections containing lidocaine 1% and a placebo was included. Surgery was offered regardless of the effect of the blocks. Twenty-four patients received 72 blocks. Sixteen patients opted for surgery, 5 patients refrained from surgery, and in 3 the blocks provided permanent pain relief. The predictive ability of the block on the outcome of surgery was assessed by calculating the area under a Receiver Operating Characteristic curve (AUC).

RESULTS

The AUC of the first lidocaine block was 0.35 with a 95% confidence interval from 0.077 to 0.62. At 95% confidence (two-sided), the AUC is less than 0.62, and hence the predictive ability of the block was poor. The outcome of the second lidocaine block and saline block did not change the conclusion of the first block.

CONCLUSIONS

We conclude that the use of blocks to select patients for surgery should be critically appraised.

PERSPECTIVE

A pain relieving response to one open block is currently considered mandatory before patients with focal nerve injury and neuropathic pain are offered surgery. Blinded blocks including a placebo show that responses for selection should be carefully interpreted because they may not be as predictive as generally presumed.

Imaging of inguinal-related groin pain in athletes

Inguinal canal-related groin pain is common in athletes and may involve numerous structures such as the conjoint tendon and the transversalis fascia. Ultrasound is the only dynamic tool that shows the passage of preperitoneal fat at the level of the Hesselbach triangle and allows excluding true inguinal hernias. Fascia transversalis bulging and inguinal ring dilatation may also be described. MRI assesses injuries of rectus abdominis and adductor longus enthesis and osteitis symphysis but its accuracy for the diagnosis of inguinal-related groin pain remains debated.

Diagnosis of Ilioinguinal Nerve Injury Based on Electromyography and Ultrasonography: A Case Report

Being located in the hypogastric area, the ilioinguinal nerve, together with iliohypogastric nerve, can be damaged during lower abdominal surgeries. Conventionally, the diagnosis of ilioinguinal neuropathy relies on clinical assessments, and standardized diagnostic methods have not been established as of yet. We hereby report the case of young man who presented ilioinguinal neuralgia with symptoms of burning pain in the right groin and scrotum shortly after receiving inguinal herniorrhaphy. To raise the diagnostic certainty, we used a real-time ultrasonography (US) to guide a monopolar electromyography needle to the ilioinguinal nerve, and then performed a motor conduction study. A subsequent US-guided ilioinguinal nerve block resulted in complete resolution of the patient's neuralgic symptoms.

Sonographic tracking of trunk nerves: essential for ultrasound-guided pain management and research

Delineation of architecture of peripheral nerves can be successfully achieved by high-resolution ultrasound (US), which is essential for US-guided pain management. There are numerous musculoskeletal pain syndromes involving the trunk nerves necessitating US for evaluation and guided interventions. The most common peripheral nerve disorders at the trunk region include thoracic outlet syndrome (brachial plexus), scapular winging (long thoracic nerve), interscapular pain (dorsal scapular nerve), and lumbar facet joint syndrome (medial branches of spinal nerves). Until now, there is no single article systematically summarizing the anatomy, sonographic pictures, and video demonstration of scanning techniques regarding trunk nerves. In this review, the authors have incorporated serial figures of transducer placement, US images, and videos for scanning the nerves in the trunk region and hope this paper helps physicians familiarize themselves with nerve sonoanatomy and further apply this technique for US-guided pain medicine and research.

Peripheral nerve imaging: Not only cross-sectional area

Peripheral nerve imaging is recognized as a complement to clinical and neurophysiological assessment in the evaluation of peripheral nerves with the ability to impact patient management, even for small and difficult nerves. The European Society of Musculoskeletal Radiology, suggest to use ultrasound (US) for nerve evaluation due to the fact that, in sever anatomical area, magnetic resonance imaging is not able to give additional informations. US could be considered the first-choice approach for the assessment of peripheral nerves. The relative drawback of peripheral nerve US is the long learning curve and the deep anatomic competence to evaluate even small nerves. In the recent years, the role of US in peripheral nerve evaluation has been widened. In the past, nerve US was mainly used to assess nerve-cross sectional area, but now more advanced measurements and considerations are desirable and can boost the role of peripheral nerve US. Nerve echotexture evaluation was defined in 2010: The ratio between the hypoechoic and hyperechoic areas of peripheral nerves on US was called “nerve density”. For evaluation of patients who have peripheral neuropathies, the role of peripheral nerve is US wider than simple cross-sectional area evaluation. Quantitative measurements describing the internal fascicular echotexture of peripheral nerves introduce the concept of considering US as a possible quantitative imaging biomarker technique. The potential of nerve US has started to be uncovered. It seems clear that only cross-sectional area measurement is no more sufficient for a comprehensive US evaluation of peripheral nerves.