Ultrasound-Guided Injection in Meralgia Paresthetica: A Case Series and Technical Report

Abstract

This case series describes high-resolution ultrasound-based diagnosis of meralgia paresthetica and the technical details of ultrasound-guided perineural therapeutic steroid injections. Twelve patients with clinically suspected meralgia paresthetica were prospectively assessed. The cross-sectional area of the lateral femoral cutaneous nerve was measured proximal and distal to the inguinal ligament using an 18-MHz transducer. Of the 12 patients, 10 demonstrated sonographic abnormalities, with a cross-sectional area difference greater than 2 mm² serving as a diagnostic criterion. Eight patients with confirmed diagnosis and nonsurgical causes of entrapment underwent ultrasound-guided perineural triamcinolone acetate injections, resulting in complete symptom relief in 87% of cases at 6 weeks. Literature review findings showed comparable success rates of 80 to 85% for ultrasound-guided injections and 80% for surgical decompression. No significant complications were encountered, highlighting the safety and efficacy of this minimally invasive approach. High-resolution ultrasound thus serves as a valuable tool for both diagnosis and guided treatment of meralgia paresthetica, offering cost-effective and patient-friendly management with outcomes comparable to surgery.

Keywords

meralgia paresthetica - lateral femoral cutaneous nerve - ultrasound-guided injections - steroid injections - minimally invasive alternatives

Introduction

Meralgia paresthetica (MP) is a neuropathy of the lateral femoral cutaneous nerve (LFCN) characterized by pain, paresthesia, numbness, and altered sensation over the anterolateral thigh.[1] [2] The condition results from entrapment or compression of the LFCN as it passes beneath the inguinal ligament near the anterior superior iliac spine (ASIS).[1] MP, also known as Bernhardt–Roth syndrome, was initially described in the mid-1880s.[3] The prevalence is approximately 4.3 patients per 100,000 individuals, with a higher incidence among males, diabetics, obese patients, and during pregnancy, with a peak in the fifth decade.[1] [2] [4] The diagnosis is based on clinical symptoms, with MP remaining a diagnosis of exclusion. Nerve conduction studies and imaging aid in diagnosis.[5]

The LFCN is a pure sensory nerve and arises from the posterior divisions of the anterior rami of L2 and L3 nerve roots, follows the lateral border of the psoas muscle, and courses through the pelvis toward the inguinal ligament.[1] [2] [6] At the ASIS level, the nerve passes beneath the inguinal ligament, remains medial to the ASIS, and traverses between the sartorius and tensor fascia lata muscles before bifurcating into anterior and posterior branches.[1] This anatomical pathway, combined with considerable anatomic variability, creates multiple potential sites for nerve entrapment and contributes to diagnostic challenges.[1] [7]

Traditional diagnostic approaches often rely on clinical evaluation supported by neurophysiological studies, but lack of standardized criteria and unfamiliarity with the condition contribute to diagnostic delays.[8] Treatment options include conservative management, ultrasound-guided injections, and surgical interventions.[1] [2] [6] [9] Conservative management remains the mainstay of management with assurance, avoidance of external compression, and rehabilitation.[6] While surgery provides direct anatomical correction, ultrasound-guided injections offer minimally invasive alternatives with real-time visualization capabilities and comparable therapeutic outcomes in addition to providing diagnostic confirmation.[8] The European Society of Musculoskeletal Radiology recommends ultrasound utilization for diagnosis and treatment of peripheral nerve pathologies, including compressive neuropathies.[8] Ultrasound provides advantages including low cost, high soft-tissue resolution, real-time evaluation, and ability to compare with the contralateral side.[1] [5] [6] [8] This study aims to evaluate the diagnostic accuracy of ultrasound in MP and assess therapeutic efficacy of ultrasound-guided perineural steroid injections.

Case Series

Twelve patients with clinically suspected MP presenting with burning, tingling, and pain in the anterolateral thigh were evaluated [Table 1].

Ultrasound Technique and Diagnostic Criteria

High-resolution ultrasound examination was performed using an 18 MHz linear probe. Patients were positioned supine. Sonographic identification of the nerve is possible at a relatively constant landmark between the tensor fascia lata and sartorius muscle bellies distal to the ASIS ([Fig. 1]). The nerve is in a superficial location at this site, and can be traced proximally up to the ASIS, where it dives deep into the pelvis under the inguinal ligament. This is a common site of entrapment and focal enlargement of the nerve. Anatomical variations in the LFCN include the accessory nerve arising from the femoral nerve at the level of inguinal canal, intramuscular course of the LFCN in the proximal thigh, and early branching of the nerve. For appropriate diagnosis and identification of such variations, the LFCN branches can be identified in the subcutaneous plane in the mid-thigh and followed proximally as they join the main LFCN.

Fig. 1 Diagrammatic representation of the course of the LFCN with probe position. Image on the right demonstrates the corresponding ultrasound picture with the nerve (encircled) superficial to the muscular fascia. LFCN, lateral femoral cutaneous nerve.

The cross-sectional area of the LFCN was measured at standardized locations proximal and distal to the inguinal ligament. Diagnostic criteria included cross-sectional area difference >2 mm² between affected and normal sides, hypoechogenicity of nerve fascicles, or presence of neuroma formation ([Fig. 2]). Both symptomatic and asymptomatic contralateral nerves were assessed for comparison. Patients included in this case series had unilateral symptoms, allowing for the contralateral side to be used as a control.

Fig. 2 Transverse gray-scale ultrasound image demonstrating >2 mm² difference in cross-sectional area of the LFCN of the normal and affected sides. LFCN, lateral femoral cutaneous nerve.

Ultrasound-Guided Injection Procedure

For patients with a confirmed ultrasound diagnosis, ultrasound-guided perineural injection was performed with sterile preparation using 2% chlorhexidine in 70% alcohol solution following local anesthesia administration. Under real-time visualization, a 23-gauge needle was advanced into the perineural space of the affected LFCN just before it pierces the fascia lata, distal to the ASIS. The deeper and superficial aspects of the nerve sheath were targeted and complete neural encasement with the solution was achieved ([Fig. 3]). A therapeutic solution consisting of corticosteroid (triamcinolone acetate) combined with local anesthetic (2% lidocaine) amounting to a total of 5 to 6 cc was delivered around the affected nerve under continuous ultrasound guidance to ensure optimal perineural distribution. Complete hydro-dissection was achieved by ensuring circumferential encasement of the nerve with fluid.

Fig. 3 Ultrasound-guided perineural LFCN hydrodissection. A lateral to medial approach was used and the nerve sheath was targeted—first the deeper aspect (A) and then the superficial aspect. Complete encasement of the nerve by the injectate was ensured (B). Yellow arrow marks the LFCN. LFCN, lateral femoral cutaneous nerve.

Outcome Assessment

Visual Analog Scale scores were recorded before the procedure, immediately post-procedure, and at 6-week follow-up. Treatment success was defined as complete symptom relief or >50% reduction in Visual Analog Scale score. Since MP results in burning and tingling, without any motor deficit, the functionality of the patients was not markedly affected. Complications and adverse events were documented throughout the study period.

Among 12 patients assessed (24 nerves, including contralateral controls), 10 patients demonstrated LFCN abnormalities on ultrasound examination. Diagnostic findings included cross-sectional area difference >2 mm² (n = 10), hypoechogenicity of nerve fascicles (n = 7), neuroma formation (n = 2), and external compression (n = 2; [Figs. 4] and [5]).

Fig. 4 Neuroma in continuity in the LFCN distal to the inguinal ligament. LFCN, lateral femoral cutaneous nerve.

Fig. 5 A case of meralgia paresthetica due to compression on the nerve by fibrofatty tissue.

The mean cross-sectional area of affected nerves was 4.8 ± 1.2 mm² compared with 2.1 ± 0.4 mm² for normal contralateral nerves (p < 0.001). Two patients showed normal ultrasound findings despite clinical suspicion and were excluded from therapeutic intervention ([Table 2]).

Table 1 Patient demographics and clinical characteristics

Parameter	Value
Total patients	12
Mean age (years)	51.4 ± 12.3
Gender (M:F)	5:7
Mean symptom duration (months)	8.2 ± 6.1
Associated obesity	4 (40%)
Associated diabetes	2 (20%)
Pregnancy-related	1 (10%)

Table 2 Ultrasound findings and treatment outcomes

Finding	Number of patients	Percentage
Cross-sectional area difference >2 mm2	10	84%
Nerve hypoechogenicity	7	70%
Neuroma formation	2	20%
Compressive lesion	2	20%
Normal ultrasound	2	20%
Received injection	8	80%
Complete symptom relief	7	87%
Treatment failure	1	13%

Note: Percentages for findings are based on the total of 10 patients with ultrasound abnormalities. Percentage for treatment outcomes is based on the 8 patients who received an injection.

Therapeutic Outcomes

Eight patients with confirmed ultrasound diagnosis received ultrasound-guided perineural steroid injections. Pre-procedure Visual Analog Scale scores ranged from 5 to 9 (mean 7.0 ± 1.6). Immediate post-procedure scores decreased to 1 to 4 (mean 2.2 ± 1.3), representing significant improvement (p < 0.01).

At 6-week follow-up, seven patients (87%) achieved complete symptom relief with Visual Analog Scale scores of 0 to 2. One patient (13%) experienced symptom recurrence with the Visual Analog Scale score returning to 8, representing treatment failure. No major complications occurred, with only transient numbness from local anesthetic reported in all patients, resolving within 12 to 24 hours.

Potential minor complications from the procedure include post-procedural pain and strain of the sartorius/tensor fascia lata. No major complications are expected from this procedure if performed safely under ultrasound guidance.

Discussion

Our case series demonstrates that high-resolution ultrasound effectively diagnoses MP with clear morphological criteria and provides successful therapeutic intervention through guided steroid injection. The 87% success rate in our prospective series aligns with the current available literature, confirming the efficacy of ultrasound-guided treatment.[1]

Ultrasound diagnosis relies on quantitative measurements of nerve cross-sectional area and qualitative assessment of nerve echogenicity.[7] [8] The >2 mm² cross-sectional area difference threshold proved reliable for distinguishing pathological from normal nerves, consistent with established diagnostic criteria for peripheral nerve entrapment syndromes.[8] [10] Real-time visualization during injection ensures accurate needle placement and optimal therapeutic agent distribution around the affected nerve, positioning this technique as an optimal first-line treatment approach. Furthermore, other ultrasound-guided techniques, such as hydro-dissection, have been explored to release the nerve from surrounding tissues, further expanding the minimally invasive options.[1] [11]

Surgical approaches require general anesthesia, operative expertise, and carry inherent risks of wound complications, infection, and nerve injury.[6] Surgical techniques include neurectomy, neurolysis, decompression, and nerve transposition.[1] [6] [9] A 2021 meta-analysis by Tagliafico et al in the European Journal of Radiology demonstrated an effectiveness of 80% for surgery in treating MP. This conclusion was based on an analysis of 92 patients who underwent surgical procedures. The study further highlighted that this success rate was not statistically different from the 85% effectiveness found for minimally invasive ultrasound-guided injections.[1] The ability to perform ultrasound-guided injections in office settings with immediate return to normal activities represents a substantial clinical advantage.

The European Society of Musculoskeletal Radiology endorsement of ultrasound for peripheral nerve pathology diagnosis and treatment supports the growing role of interventional radiology in MP management.[8] The technique's safety profile, demonstrated by absence of major complications in our series and published literature, further supports its use as first-line therapy.[6] [11]

The 13% failure rate in our series, with one patient experiencing complete symptom recurrence, highlights the need for longer follow-up and investigation of factors predicting treatment success.

Future research should focus on randomized controlled trials directly comparing ultrasound-guided injection with surgical intervention, standardized outcome measures, and extended follow-up periods to assess treatment durability. Investigation of optimal injection techniques, steroid preparations, and patient selection criteria would further enhance treatment outcomes.

Conclusion

High-resolution ultrasound represents an effective diagnostic modality for MP, enabling accurate identification of LFCN pathology through established morphological criteria. Ultrasound-guided perineural steroid injection achieves therapeutic success rates comparable to surgical intervention while offering significant advantages in terms of invasiveness, cost-effectiveness, and patient safety. These findings support ultrasound-guided injection as the preferred first-line treatment for MP, with surgery reserved for refractory cases requiring definitive anatomical correction. Larger randomized controlled trials with extended follow-up are warranted to provide definitive comparative effectiveness data and optimize patient selection criteria.

Conflict of Interest

None declared.

Acknowledgments

The authors acknowledge the patients who participated in this study and the technical staff who provided assistance with ultrasound examinations and intervention procedures.

Data Availability Statement

Data supporting the conclusions are available from the corresponding author upon reasonable request.

Ethical Approval

This study was approved by the institutional ethics committee.

• References

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Publication History

Article published online:
05 February 2026