Surgical anatomy of the lateral femoral cutaneous nerve for meralgia paraesthetica: A simple technical guide for surgeons and trainees alike

Meralgia paraesthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve, usually due to compression at the inguinal ligament as the nerve passes from the pelvis into the thigh. Surgical decompression of the lateral femoral cutaneous nerve is a simple and effective treatment option, but the surgical anatomy of the area is not always familiar to neurosurgeons and neurosurgical trainees alike. This paper is a simple review of the relevant surgical anatomy and the surgical steps of lateral femoral cutaneous nerve decompression, with the aim of providing the busy surgeon and trainee a quick and easy reference guide to the procedure.

[Decompression of the lateral femoral cutaneous nerve of the thigh : Treatment of meralgia paresthetica]

OBJECTIVE

Treatment of non-responding pain to conservative treatment located at the anterolateral thigh with surgical decompression of the lateral femoral cutaneous nerve of the thigh (LFCN).

INDICATIONS

Compression syndrome of the LFCN; patients suffering from the following symptoms: pain (dysesthesia), numbness (paresthesia), hypersensibility to temperature (or temperature changes) along the course of the LFCN located at the anterolateral thigh.

CONTRAINDICATIONS

A new or recrudescent hernia with additional pain or recent laparoscopic hernia repair as a supposed iatrogenically induced compression of the LFCN.

SURGICAL TECHNIQUE

Dissection and release of the LFCN of connective tissue, scar tissue, bone rims, and retraction located along the passage underneath the inguinal ligament and distally.

POSTOPERATIVE MANAGEMENT

Suture removal after 10-14 days, no sports for 2 weeks. Physiotherapy if necessary. Neurography 4 months after surgery (obligatory if symptoms are persistent). The patient should be followed up for about 24 months.

RESULTS

Of the patients, 69% had a history of trauma or surgery, which were designated as the onset of pain. Of these patients, 78% had hip prostheses and 22% had previous falls. Postoperatively, a significant reduction of pain of 6.6 points on the numeric rating scale was observed. All other evaluated parameters also improved postoperatively. Patient satisfaction was high, with 86% reporting complete satisfaction, and 14% reporting partial satisfaction.

Meralgia Paraesthetica after Prone Position Ventilation in a Patient with COVID-19

Background and objectives

One of the most feared complications of COVID-19 is respiratory failure caused by acute respiratory distress syndrome. In order to improve oxygenation and survival, patients admitted to intensive care units and intubated may undergo prone position mechanical ventilation. Prolonged prone positioning may cause meralgia paraesthetica due to lateral femoral cutaneous nerve entrapment between the inguinal ligament and the anterior superior iliac spine. Reports of the first two cases have been recently published.

Case presentation

We describe the case of a 52-year-old man with respiratory failure during COVID-19 infection, who underwent prone position ventilation for 16 hours a day over 19 days and developed persistent burning pain and dysaesthesia on the lateral surface of the thigh bilaterally, diagnosed as meralgia paraesthetica.

Conclusion

This is the second report describing meralgia paraesthetica following prone position ventilation in COVID-19. Given the ongoing pandemic and the inevitability of more patients with severe respiratory distress requiring prone position ventilation, this disabling entrapment condition should be considered and possibly prevented.

LEARNING POINTS

[Subcutaneous botulinum toxin in the treatment of peripheral neuropathic pain]

Neuropathic pain impairs quality of life in affected individuals and poses a challenge to clinicians due to the complexity of its treatment and frequent therapeutic failures. We present 4clinical cases of chronic neuropathic pain (LANSS ≥ 19), refractory to conservative treatment (meralgia paraesthetica, post-surgical pain and 2surgical scars). Subcutaneous botulinum toxin type A was infiltrated periodically over the painful area. All patients experienced subjective improvement in pain and improvement measured by the visual analogic scale. Pain relief started at 5-21 days and continued up to 1.5-3 months, and up to 9 months in one patient. Pain that reappeared was of lower intensity in 3patients and was reduced in area in 2patients.

A rare presentation of meralgia paraesthetica in limb girdle muscular dystrophy

A 44-year-old female with paraesthesia and pain on the left anterolateral thigh who had been diagnosed with limb-girdle muscular dystrophy by electromyography and muscle biopsy is presented. Neurological examination revealed atrophy of the proximal muscles of both shoulders, plus pseudo hypertrophy of both calves. Electromyography exhibited a myopathic pattern. Musculoskeletal ultrasound imaging demonstrated a fusiform nerve swelling below the inguinal ligament suggesting lateral femoral cutaneous nerve compression, consistent with meralgia paraesthetica. Treatment with a perineural injection of betamethasone dipropionate and betamethasone sodium phosphate combination, and prilocaine-HCl, under ultrasound guidance, was performed. Symptoms resolved within 6 h. At 3-week follow-up, the patient was asymptomatic, and there was no paraesthesia or pain on examination. In this case, ultrasound-guided perineural injection of the lateral femoral cutaneous nerve with local anaesthetics and steroid served both diagnostic and therapeutic functions.

Meralgia paraesthetica: Ultrasound-guided injection at multiple levels with 12-month follow-up

OBJECTIVES

To evaluate the efficacy of ultrasound (US)-guided injections around the lateral femoral cutaneous nerve (LFCN) at different levels in meralgia paraesthetica (MP) patients.

METHODS

The study was approved by the university ethics committee and informed oral and written consent were obtained from all patients. Between June 2008 and August 2013, 20 patients with symptoms of MP, including nine men (mean age, 61.33 years) and 11 women (mean age 61.18 years), were treated with US-guided injection of steroids along the LFCN at three different levels in a mean of 2.25 sessions. A visual analogue scale (VAS) was used to measure symptoms before, immediately after and 12 months after treatment.

RESULTS

Complete resolution of symptoms was documented in 15/20 patients (mean VAS decreased from 82 to 0), and partial resolution in the remaining five (mean VAS decreased from 92 to 42), which was confirmed at 12-month follow-up. By using the different levels of injection approach overall significantly better symptom relief was obtained (p < 0.05).

CONCLUSION

The outcome of US-guided injection along the LFCN can be further improved by injections at different levels (p < 0.05), which was confirmed at 12-month long-term follow-up.

KEY POINTS

Meralgia paraesthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve. Ultrasound proved effective in diagnosis and in guiding injection therapy. Injection at the anterior superior iliac spine has been used previously. Multiple injections along the nerve course were used in this study. Long-term follow-up (12 months) confirmed the results.