Sonographic evaluation of the lateral femoral cutaneous nerve in meralgia paresthetica

Diagnostic criteria utilized for selection of patients for meralgia paresthetica surgery: a systemic review

Meralgia paresthetica (MP) lacks consensus on diagnostic criteria for surgical candidates. This study reviews the literature to identify the most common criteria for determining MP surgical candidates and their impact on surgical outcomes. A literature search using PubMed, MEDLINE, and Google Scholar was conducted for MP surgical outcome studies. Studies were evaluated using methodical index for non-randomized studies (MINORS) criteria, and diagnostic criteria were compared. Twenty-one studies were identified with inclusion of 616 surgical results involving decompression or neurectomy of the lateral femoral cutaneous nerve (LFCN). The most used diagnostic criteria were patient history (100%), response to LFCN injection (90%), and spinal imaging (57%). Positive outcomes were noted in 84.7% of cases. History and LFCN injection were effective for diagnosing MP, while EMG was useful to rule out other pathologies. The combination of appropriate patient history and positive response to LFCN injection is a common and sufficient diagnostic method to effectively identify MP patients who are likely to benefit from surgical decompression or neurectomy. Additionally, EMG may be useful as a supplemental test to rule out non-MP diagnoses. Level III systematic review.

The Diagnosis and Management of Meralgia Paresthetica: A Narrative Review

Meralgia paresthetica (MP) is a sensory mononeuropathy affecting the lateral femoral cutaneous nerve. Diagnosis is typically made clinically, often utilising multiple diagnostic aids such as imaging and electrophysiology. Upon diagnosis, the management of MP follows the standard ladder, with conservative management first line, followed by steroid injection and finally surgery. Surgery may be neurolysis or neurectomy. A literature review of the PubMed database was performed identifying 594 papers regarding MP or the lateral femoral cutaneous nerve. Following a two-stage screening process and reference searching, 34 articles were included in this review, 11 discussing diagnosis and 23 discussing management. Despite the longstanding knowledge of MP, there remains limited comprehensive research discussing its diagnosis and management. Diagnosis of MP is based on clinical examination, imaging and electrophysiology. There is no obviously superior diagnostic strategy for MP. Once that diagnosis is made, the management strategy is typical of any condition, wherein a patient will move up the intervention ladder. It is apparent that conservative management and steroid injection are both adequate in most patients. Where these strategies fail, surgical options such as decompression, radiofrequency ablation or neurectomy are suitable for the majority of remaining patients. While both neurolysis and neurectomy are described as appropriate strategies, there is a scope for discussion regarding whether one is superior. Other management strategies such as botox, acupuncture and kinesio taping may have some value, but limited research exists on these strategies and further research into these is required.

Less Common Mononeuropathies

Uncommon mononeuropathies are challenging to diagnose as they can mimic joint pathology, radiculopathies, or plexopathies. They are less easily diagnosed due to unfamiliarity with their clinical presentation, knowledge of anatomy, and less commonly used diagnostic studies. A careful history, physical examination, and electrodiagnostic evaluation can help identify these neuropathies in a timely manner to administer the best treatment for resolution of symptoms. Recent advances in ultrasound and magnetic resonance techniques are used to confirm clinical suspicion of peripheral neuropathy by clearly depicting the anatomy and pathology as well as describing findings that mimic mononeuropathy. It is important for neurology, orthopedic, rheumatology, emergency, and primary care physicians to be familiar with less common mononeuropathies.

Sonographic Evaluation of the Lateral Femoral Cutaneous Nerve: Single-Institution Experience and Pictorial Review

ABSTRACT

The location of the lateral femoral cutaneous nerve (LFCN) makes it susceptible to injury with trauma, external compression, and iatrogenic injury. The objectives of this study were to report the single-institution efficacy of LFCN visualization on ultrasound (US), define the clinical characteristics of patients with LFCN palsy, and describe sonographic appearances of LFCN abnormalities by pictorial review. A retrospective chart review of LFCN cases evaluated using US at a single institution was performed, documenting rate of visibility on US, mode of nerve injury, and US imaging findings. Nerve visibility rates on US were correlated with magnetic resonance imaging (MRI) when both modalities were used. Imaging findings were confirmed with clinical/surgical history and follow-up. Retrospective review found that 170 patients underwent US for LFCN evaluation in the last 10 years. Injury was associated with surgical intervention in 56% of cases, and perineural scarring was the most common pathology described using US. Lateral femoral cutaneous nerve was visible on US in 97% of cases; MRI visualized LFCN in 60%. Chart review showed US as an effective tool in evaluating LFCN pathology, with a higher visualization rate than MRI. Through pictorial review, the array of LFCN pathology sonographically detectable is demonstrated.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Meralgia Paresthetica: Relevance, Diagnosis, and Treatment

BACKGROUND

Pain and sensory disturbance in the distribution of the lateral femoral cutaneous nerve in the ventrolateral portion of the thigh is called meralgia paresthetica (MP). The incidence of MP has risen along with the increasing prevalence of obesity and diabetes mellitus and was recently estimated at 32 new cases per 100 000 persons per year. In this review, we provide an overview of current standards and developments in the diagnosis and treatment of MP.

METHODS

This review is based on publications retrieved by a selective literature search, with special attention to meta-analyses, systematic reviews, randomized and controlled trials (RCTs), and prospective observational studies.

RESULTS

The diagnosis is mainly based on typical symptoms combined with a positive response to an infiltration procedure. In atypical cases, electrophysiological testing, neurosonography, and magnetic resonance imaging can be helpful in establishing the diagnosis. The literature search did not reveal any studies of high quality. Four prospective observational studies with small case numbers and partly inconsistent results are available. In a meta-analysis of 149 cases, pain relief was described after infiltration in 85% of cases and after surgery in 80%, with 1-38 months of follow-up. In another meta-analysis of 670 cases, there was pain relief after infiltration in 22% of cases, after surgical decompression in 63%, and after neurectomy in 85%. Hardly any data are available on more recent treatment options, such as radiofrequency therapy, spinal cord stimulation, or peripheral nerve stimulation.

CONCLUSION

The state of the evidence is limited in both quantity and quality, corresponding to evidence level 2a for surgical and non-surgical methods. Advances in imaging and neurophysiological testing have made the diagnosis easier to establish. When intervention is needed, good success rates have been achieved with surgery (decompression, neurectomy), and variable success rates with infiltration.

Nerve entrapment syndromes: detection by ultrasound

Nerve entrapment syndromes are commonly encountered in clinical practice. Accurate diagnosis and management require a knowledge of peripheral neuroanatomy and the recognition of key clinical symptoms and findings. Nerve entrapment syndromes are frequently associated with structural abnormalities of the affected nerve. Therefore, imaging allows the evaluation of the cause, severity, and etiology of the entrapment. High-resolution ultrasonography can depict early and chronic morphological changes within the entire nerve course and is therefore an ideal modality for diagnosing various nerve entrapment syndromes in different regions. This review article presents some of the most common types of nerve entrapment, with special focus on ultrasound imaging and key findings.

Meralgia Paresthetica Review: Update on Presentation, Pathophysiology, and Treatment

Purpose of Review

Meralgia paresthetica (MP) is a condition characterized by paresthesias, neuropathic pain, and alterations in sensorium of the anterolateral thigh secondary to impingement of the lateral femoral cutaneous nerve (LFCN). MP is generally diagnosed by clinical history and is often a diagnosis of exclusion. When diagnosis remains a challenge, diagnostic modalities such as ultrasound, MRI, electromyography, and nerve conduction studies have been utilized as an adjunct. This review summarizes the most recent medical literature regarding MP, its pathophysiology, presentation, and current treatment options.

Recent Findings

Treatment options for patients with MP range from lifestyle modifications and conservative management to surgical procedures. Initial management is often conservative with symptoms managed with medications. When conservative management fails, the next step is regional blocks followed by surgical management. The conflicting data for treatment options for MP highlight how the evidence available does not point to a single approach that's universally effective for treating all patients with MP.

Summary

Despite the apparent success at treating MP with regional blocks and surgical interventions, much remains to be known about the dosing, frequency, and optimal interventions due to the inconclusive results of current studies. Further research including randomized controlled trials are needed to better understand the most optimal treatment options for MP including studies with a larger number of participants.

Imaging of the Peripheral Nerves of the Lower Extremity

Continued advancements in magnetic resonance (MR) neurography and ultrasound have made both indispensable tools for the workup of peripheral neuropathy. Ultrasound provides high spatial resolution of superficial nerves, and techniques such as "sonopalpation" and dynamic maneuvers can improve accuracy. Superior soft tissue contrast, ability to evaluate both superficial and deep nerves with similar high resolution, and reliable characterization of denervation are strengths of MR neurography. Nevertheless, familiarity with normal anatomy, anatomic variants, and common sites of nerve entrapment is essential for radiologists to use both MR neurography and ultrasound effectively.

US for Traumatic Nerve Injury, Entrapment Neuropathy, and Imaging-guided Perineural Injection

US is commonly performed to help diagnose traumatic peripheral nerve injury and entrapment neuropathy, particularly with superficial nerves, where higher spatial resolution provides an advantage over MRI. Other advantages of US include dynamic evaluation, easy contralateral comparison, fewer implant contraindications, less artifact from ferromagnetic debris, and facile needle guidance for perineural injections. The authors review peripheral nerve US for traumatic peripheral nerve injury with an emphasis on injury grading and entrapment neuropathy and describe best-practice techniques for US-guided perineural injections while highlighting specific techniques and indications. Online supplemental material is available for this article. ^©RSNA, 2022.

Ultrasound of the Lateral Femoral Cutaneous Nerve: A Review of the Literature and Pictorial Essay

We review the ultrasound (US) findings in patients who present with meralgia paresthetica (MP). The anatomy of the lateral femoral cutaneous nerve at the level where the nerve exits the pelvis and potential entrapment sites that can lead to MP are discussed. A wide range of pathological cases are presented to help in recognizing the US patterns of MP. Finally, our experience with US-guided treatment is discussed.

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound - Part I: Extraarticular Pathologies

The first part of the guidelines and recommendations for musculoskeletal ultrasound, produced under the auspices of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), provides information about the use of musculoskeletal ultrasound for assessing extraarticular structures (muscles, tendons, entheses, ligaments, bones, bursae, fasciae, nerves, skin, subcutaneous tissues, and nails) and their pathologies. Clinical applications, practical points, limitations, and artifacts are described and discussed for every structure. After an extensive literature review, the recommendations have been developed according to the Oxford Centre for Evidence-based Medicine and GRADE criteria and the consensus level was established through a Delphi process. The document is intended to guide clinical users in their daily practice.

Sonographic features of the lateral femoral cutaneous nerve in meralgia paresthetica

BACKGROUND

The diagnosis of meralgia paresthetica (MP) is usually based on clinical symptoms and physical examination. Therefore, the present study aimed to investigate the lateral femoral cutaneous nerve (LFCN) sonographic features in MP patients.

METHODS

A total of 86 clinically suspected MP patients and 40 asymptomatic volunteers were prospectively recruited in the study. The sonographic features of the LFCN were observed by 18 MHz high-frequency ultrasound. At the level of the anterior superior iliac spine, the cross-sectional area of the LFCN was measured.

RESULTS

Of the 86 clinically suspected MP patients, 82 (95.3%) had sonographic findings positive for MP. There were 54, 63, and 44 cases of abrupt caliber change, indistinct perineurium, and abnormal intraneural vascularity. The average value of the cross-sectional area of the LFCN at the level of the anterior superior iliac spine was 4.47±2.64 mm2, and the cut-off value was 2.65 mm2.

CONCLUSIONS

The sonographic diagnosis of MP may be achieved based on the following signs: nerve abrupt caliber change, indistinct perineurium of the nerve, intraneural vascularity, or increased cross-sectional area.

Preoperative Ultrasound in Patients with Meralgia Paresthetica to Detect Anatomical Variations in the Course of the Lateral Femoral Cutaneous Nerve

OBJECTIVE

Sometimes during surgery for meralgia paresthetica, it can be difficult to find the lateral femoral cutaneous nerve (LFCN). The aims of this study were to study the prevalence of different anatomical variations in patients, compare preoperative ultrasound (US) data with intraoperative findings, and investigate the effect of type of anatomical variation on duration of surgery and success rate of localizing the LFCN.

METHODS

Fifty-four consecutive patients with idiopathic meralgia paresthetica who underwent either a neurolysis or neurectomy procedure were included. All patients preoperatively underwent US of the LFCN. Anatomical variations were categorized into type A, B, C, D, and E using the classification of Aszmann and Dellon. The cross-sectional area of the LFCN at the inguinal ligament and the distance of the LFCN to the anterior superior iliac spine were noted. Correlations with intraoperative findings were investigated, as well as the effect on duration of surgery and success rate of finding the LFCN. Clinical outcome was assessed using the Likert scale.

RESULTS

The most frequent anatomical variant was type B (79%), followed by type C (9%), D (5%), and E (7%). No type A was encountered. Correlation between preoperative US and intraoperative findings was 100%. During surgery, the LFCN could be identified in all cases. Duration of surgery did not significantly vary for the different anatomical variants.

CONCLUSIONS

Preoperative US is reliable in detecting anatomical variations of LFCN. This information can be very helpful in identifying the LFCN more frequently and easily during surgery, especially in more medial variants.