Meralgia paresthetica in differential diagnosis of low-back pain

Nerve entrapment syndromes of the lower limb: a pictorial review

Peripheral nerves of the lower limb may become entrapped at various points during their anatomical course. While clinical assessment and nerve conduction studies are the mainstay of diagnosis, there are multiple imaging options, specifically ultrasound and magnetic resonance imaging (MRI), which offer important information about the potential cause and location of nerve entrapment that can help guide management. This article overviews the anatomical course of various lower limb nerves, including the sciatic nerve, tibial nerve, medial plantar nerve, lateral plantar nerve, digital nerves, common peroneal nerve, deep peroneal nerve, superficial peroneal nerve, sural nerve, obturator nerve, lateral femoral cutaneous nerve and femoral nerve. The common locations and causes of entrapments for each of the nerves are explained. Common ultrasound and MRI findings of nerve entrapments, direct and indirect, are described, and various examples of the more commonly observed cases of lower limb nerve entrapments are provided.Critical relevance statement This article describes the common sites of lower limb nerve entrapments and their imaging features. It equips radiologists with the knowledge needed to approach the assessment of entrapment neuropathies, which are a critically important cause of pain and functional impairment.Key points• Ultrasound and MRI are commonly used to investigate nerve entrapment syndromes.• Ultrasound findings include nerve hypo-echogenicity, calibre changes and the sonographic Tinel's sign.• MRI findings include increased nerve T2 signal, muscle atrophy and denervation oedema.• Imaging can reveal causative lesions, including scarring, masses and anatomical variants.

Lateral Femoral Cutaneous Nerve Radiofrequency Ablation for Long-term Control of Refractory Meralgia Paresthetica

BACKGROUND

Meralgia paresthetica is a term used to describe a clinical pain syndrome related to the compression or irritation of the lateral femoral cutaneous nerve (LFCN). The LFCN is a pure sensory nerve that is susceptible to compression injury. The most common compression locations are: as it courses from the lumbosacral plexus, through the abdominal cavity, under the inguinal ligament, and into the subcutaneous tissue of the thigh.

METHODS

This case series is a retrospective single-center review of six patients with medically intractable meralgia paresthetica who were treated with radiofrequency ablation. To be considered for radiofrequency ablation, the patient must have been unsuccessful with medical management alone for more than two months and have a clinical diagnosis of meralgia paresthetica. Temporary relief of pain of 50% or greater was considered a positive result. Average pain scores were measured pre- and postprocedure, along with one-, two-, three-, and six-month intervals postoperation.

RESULTS

All patients demonstrated immediate relief in self-reported pain scores, averaging a 75.5% reduction in pain. At the one-, two-, three-, and six-month follow-ups, patients averaged a reduction of 60.0%, 58.0%, 51.4%, and 40.5%, respectively. Both the postop and one-month follow-up pain scores were lower, statistically significantly so (P < 0.05), whereas the two-, three-, and six-month follow-ups were not statistically different from pretreatment scores.

CONCLUSIONS

Although our study was small, radiofrequency ablation showed a clear reduction in average pain scores in a subset of patients who had failed standard medical therapy with a reduction in pain at one-month follow-up with relief of symptoms sometimes lasting longer than 12 months.

Meralgia paresthetica: 3-Tesla magnetic resonance neurography

OBJECTIVE

To assess the diagnostic accuracy and observer performance of 3-Tesla magnetic resonance neurography (MRN) in the evaluation of meralgia paresthetica (MP).

MATERIALS AND METHODS

Two independent readers were blinded to the clinical diagnosis and evaluated the MRN studies of the pelvis of 11 patients with MP and 28 control participants. In each study, the lateral femoral cutaneous nerves were assessed for signal alteration and/or neuroma formation, indicating lateral femoral cutaneous neuropathy, at various levels along their course. Intra- and inter-observer reliability was evaluated.

RESULTS

Both readers exhibited substantial intraobserver agreement in detecting signal alterations and neuroma formation of the lateral femoral cutaneous nerve (LFCN). The readers demonstrated moderate interobserver agreement in detecting signal alteration of the LFCN and poor interobserver agreement in diagnosing neuroma formation. Sensitivity, specificity, positive predictive value, and negative predictive value of LFCN neuropathy diagnosis were ≥ 71 % and ≥ 94 % for both readers respectively. The diagnostic test accuracy was ≥ 90 % for both readers.

CONCLUSION

3-Tesla MRN provides reliable and accurate diagnostic evaluation of meralgia paresthetica.

Imaging of neuropathies about the hip

Neuropathies about the hip may be cause of chronic pain and disability. In most cases, these conditions derive from mechanical or dynamic compression of a segment of a nerve within a narrow osteofibrous tunnel, an opening in a fibrous structure, or a passageway close to a ligament or a muscle. Although the evaluation of nerve disorders primarily relies on neurological examination and electrophysiology, diagnostic imaging is currently used as a complement to help define the site and aetiology of nerve compression and exclude other disease possibly underlying the patient' symptoms. Diagnosis of entrapment neuropathies about the hip with US and MR imaging requires an in-depth knowledge of the normal imaging anatomy and awareness of the anatomic and pathologic factors that may predispose or cause a nerve injury. Accordingly, the aim of this article is to provide a comprehensive review of hip neuropathies with an emphasis on the relevant anatomy, aetiology, clinical presentation, and their imaging appearance. The lateral femoral cutaneous neuropathy (meiralgia paresthetica), femoral neuropathy, sciatic neuropathy, obturator neuropathy, superior and inferior gluteal neuropathies and pudendal neuropathy will be discussed.

A novel approach to the diagnosis and management of meralgia paresthetica

OBJECTIVE

To review the results of conservative and surgical treatment of meralgia paresthetica (MP), with particular reference to the use of a simple clinical test for diagnosing this condition and the outcome of primary nerve decompression surgery.

METHODS

Records of all patients with a diagnosis of MP were reviewed. Information was obtained about clinical presentation and risk factors, diagnostic evaluation, management, and outcome. Actuarial analysis was used to determine the intervention-free interval after surgical decompression.

RESULTS

Between 2000 and 2005, MP was diagnosed in 45 patients. There were 27 men and 18 women, and the average age at presentation and duration of symptoms were 47 and 1.9 years, respectively. The pelvic compression test had a sensitivity of 95% and a specificity of 93.3% for this condition. Twenty-five patients were managed conservatively and 20 required operative intervention, which was bilateral in two patients. The average follow-up period was 25 months, and the actuarial 2- and 5-year intervention-free rates were 91 and 78%, respectively, with no specific risk factors for revision surgery.

CONCLUSION

The pelvic compression test is a sensitive and specific test for MP, helping to distinguish it from lumbosacral radicular pain. Most patients with this condition can be managed successfully with conservative measures, and those requiring surgery can be treated effectively with nerve decompression.