Unusual causes for meralgia paresthetica: systematic review of the literature and single center experience.

Meralgia paresthetica is often idiopathic, but sometimes symptoms may be caused by traumatic injury to the lateral femoral cutaneous nerve (LFCN) or compression of this nerve by a mass lesion. In this article the literature is reviewed on unusual causes for meralgia paresthetica, including different types of traumatic injury and compression of the LFCN by mass lesions. In addition, the experience from our center with the surgical treatment of unusual causes of meralgia paresthetica is presented. A PubMed search was performed on unusual causes for meralgia paresthetica. Specific attention was paid to factors that may have predisposed to LFCN injury and clues that may have pointed at a mass lesion. Moreover, our own database on all surgically treated cases of meralgia paresthetica between April 2014 and September 2022 was reviewed to identify unusual causes for meralgia paresthetica. A total of 66 articles was identified that reported results on unusual causes for meralgia paresthetica: 37 on traumatic injuries of the LFCN and 29 on compression of the LFCN by mass lesions. Most frequent cause of traumatic injury in the literature was iatrogenic, including different procedures around the anterior superior iliac spine, intra-abdominal procedures and positioning for surgery. In our own surgical database of 187 cases, there were 14 cases of traumatic LFCN injury and 4 cases in which symptoms were related to a mass lesion. It is important to consider traumatic causes or compression by a mass lesion in patients that present with meralgia paresthetica.

Variations of the obturator nerve and implications in obturator nerve entrapment treatment: an anatomical study.

INTRODUCTION: Obturator nerve entrapment or idiopathic obturator neuralgia is an unfamiliar pathology for many physicians which can lead to diagnostic errancy. This study aims to identify the potential compression areas of the obturator nerve to improve therapeutic management. MATERIAL AND METHODS: 18 anatomical dissections of lower limbs from 9 anatomical cadavers were performed. Endopelvic and exopelvic surgical approaches were utilized to study the anatomical variations of the nerve and to identify areas of entrapment. RESULTS: On 7 limbs, the posterior branch of the obturator nerve passed through the external obturator muscle. A fascia between the adductor brevis and longus muscles was present in 9 of the 18 limbs. The anterior branch of the obturator nerve was highly adherent to the fascia in 6 cases. In 3 limbs, the medial femoral circumflex artery was in close connection with the posterior branch of the nerve. CONCLUSION: Idiopathic obturator neuropathy remains a difficult diagnosis. Our cadaveric study did not allow us to formally identify one or more potential anatomical entrapment zones. However, it allowed the identification of zones at risk. A clinical study with staged analgesic blocks would be necessary to identify an anatomical area of compression and would allow targeted surgical neurolysis.

Meralgia Paresthetica.

PURPOSE OF REVIEW: This review article summaries the epidemiology, etiology, clinical presentations, and latest treatment modalities of meralgia paresthetica, including the latest data about peripheral and spinal cord stimulation therapy. Meralgia paresthetica (MP) causes burning, stinging, or numbness in the anterolateral part of the thigh, usually due to compression of the lateral femoral cutaneous nerve (LFCN). RECENT FINDINGS: There are emerging data regarding the benefit of interventional pain procedures, including steroid injection and radiofrequency ablation, and other interventions including spinal cord and peripheral nerve stimulation reserved for refractory cases. The strength of evidence for treatment choices in meralgia paraesthetica is weak. Some observational studies are comparing local injection of corticosteroid versus surgical interventions. However, more extensive studies are needed regarding the long-term benefit of peripheral and spinal cord stimulation therapy.

Saphenous nerve schwannoma as a cause of vascular claudication - case report and review of the literature.

Schwannomas are peripheral nerve tumours that are uncommon. They typical present with a palpable mass, pain or neurological changes. We describe a saphenous nerve schwannoma compressing the superficial femoral artery and causing vascular claudication. We also review the literature.

Anatomical locations of the motor endplates of sartorius muscle for botulinum toxin injections in treatment of muscle spasticity.

PURPOSE: This study aimed to detect the idyllic locations for botulinum neurotoxin injection by analyzing the intramuscular neural distributions of the sartorius muscles. METHODS: An altered Sihler's staining was conducted on sartorius muscles (15 specimens). The nerve entry points and intramuscular arborization areas were measured as a percentage of the total distance from the most prominent point of the anterior superior iliac spine (0%) to the medial femoral epicondyle (100%). RESULTS: Intramuscular neural distribution were densely detected at 20-40% and 60-80% for the sartorius muscles. The result suggests that the treatment of sartorius muscle spasticity requires botulinum neurotoxin injections in particular locations. CONCLUSIONS: These locations, corresponding to the locations of maximum arborization, are suggested as the most suggestive points for botulinum neurotoxin injection.

The posterior femoral cutaneous nerve contributes significantly to sensory innervation of the lower leg: an anatomical investigation.

BACKGROUND: Incomplete peripheral nerve blocks distal to the popliteal region are commonly considered a sciatic and femoral/saphenous nerve block failure. The existence of a much more distal innervation area of the posterior femoral cutaneous nerve (PFCN) as described has not been assumed yet. We therefore investigated the distal termination of the PFCN in the lower leg. METHODS: In 83 human lower extremities embalmed with Theil's method, the course of the PFCN was investigated from the sub-gluteal fold to the most distal macroscopically dissectible branch. The topographic connection to other landmarks, such as the small saphenous vein or small arteries, was investigated. RESULTS: Popliteal ending of the PFCN was found in 9.7% of cases. The PFCN terminated at the proximal or distal lower leg in 45.7% and 44.6% of cases, respectively. The PFCN had a close connection to the Achilles tendon in 13.2% of cases and was found distally to the medial malleolus in one case. The small saphenous vein was close to the PFCN in 90.3% of cases and can therefore be used as a landmark to identify the nerve. In 40.9% of cases, the PFCN was accompanied by a small descending branch of the inferior gluteal artery. In two cases, an innervation of the fibula or calcaneus periosteum was found. CONCLUSIONS: The PFCN has a much more distal termination in the lower leg than previously demonstrated. To ensure complete anaesthesia of the lower leg and foot, the PFCN must be included in combined peripheral nerve block procedures.

Surgical options for meralgia paresthetica: long-term outcomes in 13 cases.

BACKGROUND: Meralgia paresthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve that may cause paresthesias, pain, and sensory loss of the anterior and lateral thigh. Treatment is primarily medical. Surgery is an option for patients who do not respond to medical treatments. METHODS: Patients whose symptoms did not improve after medical and conservative treatment for at least 3 months were included in this study. These patients underwent neurolysis and decompression surgery and had a mean postoperative follow-up of 38 months. Their pain levels were assessed by the VAS scoring system. RESULTS: In 8 (61.5%) patients, the symptoms completely resolved within the first 3 months. In 5 (38.5%) patients, the complaints persisted partially and the recovery was observed after 12 months. In patients having a metabolic etiology, the duration of recovery was up to 12 months. CONCLUSION: The long term results of surgery are good though only partial improvemnts in reported pain were seen in the early postoperative period, especially in patients with a metabolic etiology.

What Is the Risk Posed to the Lateral Femoral Cutaneous Nerve During the Use of the Anterior Portal of Supine Hip Arthroscopy and the Minimally Invasive Anterior Approach for Total Hip Arthroplasty?

PURPOSE: To determine: (1) What is the proximity of the lateral femoral cutaneous nerve (LFCN) to the anterior portal (AP) used in supine hip arthroscopy? (2) What is the proximity of the LCFN to the incision in the minimally invasive anterior approach (MIAA) for total hip arthroplasty? (3) What effect does lateralizing the AP have on the likelihood of nerve injury? (4) What branching patterns are observable in the LFCN? METHODS: Forty-five hemipelves were dissected. The LFCN was identified and its path dissected. The positions of the nerve in relation to the AP and the MIAA incision were measured. RESULTS: The AP intersected with 38% of nerves. In the remainder, the LFCN was located 5.7 ± 4.5 mm from the portal's edge. In addition, 44% of nerves crossed the incision of the MIAA. Of those that did not, the average minimum distance from the incision was 14.4 ± 7.0 mm. We found a significant reduction in risk if the AP is moved medially by 5 mm or laterally by 15 mm (P = .0054 and P = .0002). The LFCN showed considerable variation with 4 branching variants. CONCLUSIONS: These results show that the LFCN is at high risk during supine hip arthroscopy and the MIAA, emphasizing the need for meticulous dissection. We suggest that relocation of the AP 5 mm medially or 15 mm laterally will reduce the risk to the LFCN. CLINICAL RELEVANCE: These findings should aid surgeons in minimizing the risk to the LCFN during hip arthroscopy and the minimally invasive anterior approach to the hip.

Anatomy of the Pudendal Nerve and Other Neural Structures Around the Proximal Hamstring Origin in Males.

PURPOSE: To define the anatomy of the pudendal nerve in relationship to the proximal hamstring and other nearby neurological structures during proximal hamstring repair. METHODS: Six fresh-frozen human cadaveric hemi-pelvises from male patients ages 64.0 ± 4.1 years were dissected in prone position with hips in 10° flexion to identify the relationship of proximal hamstring origin to surrounding neurologic structures including the pudendal nerve, sciatic nerve, and posterior femoral cutaneous nerve. Two independent observers used digital calipers to measure distances. RESULTS: The pudendal nerve emerged at the inferior border of the piriformis muscle 6.3 ± 1.4 cm from the superior aspect of the proximal hamstring origin. It passed the superior border of the sacrotuberous ligament 3.0 ± 0.6 cm from the superior aspect and 3.9 ± 0.7 cm from the medial aspect of the hamstring origin. It crossed the inferior border of the sacrotuberous ligament 3.0 ± 0.4 cm from the superior aspect and 2.7 ± 0.7 cm from the medial aspect of the proximal hamstring origin. The shortest distance from the hamstring origin to the pudendal nerve was 2.6 ± 0.5 cm from the superior aspect and 2.3 ± 0.8 cm from the medial aspect. The shortest distance from the hamstring origin to the pudendal nerve was located deep to the sacrotuberous ligament in all cadavers. The sciatic nerve was an average of 1.1 ± 0.1 cm lateral to the lateral aspect of the proximal hamstring origin. The posterior femoral cutaneous nerve was located between the hamstring origin and the sciatic nerve, 0.7 ± 0.2 cm lateral to the lateral aspect of the proximal hamstring origin. CONCLUSIONS: The proximal hamstring origin lies in close proximity to surrounding nerves, including the pudendal, sciatic, and posterior femoral cutaneous nerves. CLINICAL RELEVANCE: Knowledge that the pudendal nerve lies 2 to 3 cm superior and medial to the proximal hamstring origin may help to prevent iatrogenic damage during surgical dissection and retraction when performing proximal hamstring repair or deep gluteal space endoscopy.

The anatomy of the perineal branch of the sciatic nerve.

A "perineal" branch of the sciatic nerve has been visualized during surgery, but there is currently no description of this nerve branch in the literature. Our study investigates the presence and frequency of occurrence of perineal innervation by the sciatic nerve and characterizes its anatomy in the posterior thigh. Fifteen cadavers were obtained for dissection. Descriptive results were recorded and analyzed statistically. Twenty-one sciatic nerves were adequately anatomically preserved. Six sciatic nerves contained a perineal branch. Five sciatic nerves had a branch contributing to the perineal branch of the posterior femoral cutaneous (PFC) nerve. In specimens with adequate anatomical preservation, the perineal branch of the sciatic nerve passed posterior to the ischial tuberosity in three specimens and posterior to the conjoint tendon of the long head of biceps femoris and semitendinosus muscles (conjoint tendon) in one. In specimens in which the perineal branch of the PFC nerve received a contribution from the sciatic nerve, the branch passed posterior to the sacrotuberous ligament in one case and posterior to the conjoint tendon in three. Unilateral nerve anatomy was found to be a poor predictor of contralateral anatomy (Cohen's kappa = 0.06). Our study demonstrates for the first time the presence and frequency of occurrence of the perineal branch of the sciatic nerve and a sciatic contribution to the perineal branch of the PFC nerve. Clinicians should be cognizant of this nerve and its varying anatomy so their practice is better informed. Clin. Anat. 31:357-363, 2018. © 2018 Wiley Periodicals, Inc.

Re-defining the anatomical structures for blocking the nerves in adductor canal and sciatic nerve through the same injection site: an anatomical study.

PURPOSE: The aim of this study is to re-define the anatomical structures which are important for blocking the sciatic nerve and the nerves within the adductor canal which innervate the knee joint through the same injection site. We also aimed to investigate the spread of the anesthetic toward the areas in which the mentioned nerves lie on cadavers. METHODS: This study was performed on 16 lower extremities of formaldehyde-embalmed eight adult cadavers. The anatomy of adductor canal, courses of the nerves within the canal and the relationships of the saphenous, medial femoral cutaneous, medial retinacular, posterior branch of the obturator and sciatic nerves with each other and with the fascial compartments were investigated. Transverse sections that crossed the superior border of vastoadductor membrane were taken to reach the sciatic nerve in the shortest way. Colored latex was injected to demonstrate the anesthetic blockage of the targeted nerves. The structures along the needle's way were investigated. RESULTS: The saphenous, medial femoral cutaneous and at its distal part posterior branch of the obturator nerve were colored with latex within the adductor canal. The nerve to vastus medialis (in other words, the medial retinacular nerve) lay beneath the fascia of vastus medialis and did not enter the adductor canal. There was a fascial plane which did not allow the passage of colored latex toward the sciatic nerve. To traverse this fascial structure, it was found out to be necessary to insert the needle perpendicular to both the vertical and transverse axes of the thigh and then advance it along 2/3 of diameter of the thigh. Thus, the colored latex was observed to fill the compartment where the sciatic nerve lay within. CONCLUSIONS: Blocking the sciatic nerve and the nerves within the adductor canal which innervate the knee joint through the same injection site seems anatomically possible without injuring any neurovascular structures.

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.

Anatomy of the lateral femoral cutaneous nerve relevant to clinical findings in meralgia paresthetica.

INTRODUCTION: Compression of the lateral femoral cutaneous nerve (LFCN), known as meralgia paresthetica (MP), is common. We investigated the topographic anatomy of the LFCN focusing on the inguinal ligament and adjacent structures. METHODS: Distances from various bony and soft-tissue landmarks to the LFCN were investigated in 33 formalin-embalmed cadavers. RESULTS: The mean distance from the anterior superior iliac spine (ASIS) to the LFCN was 8.8 mm. In approximately 90% of cases, the LFCN lay <2 cm from the medial tip of the ASIS, whereas, in 76% of cases, it was <1 cm away. The mean angle between the inguinal ligament and LFCN was 83.3°. CONCLUSIONS: We determined the variability of the location of the LFCN at the boundary between the pelvic and femoral portions. The reported results will be helpful for diagnosis and treatment of MP. Muscle Nerve 55: 646-650, 2017.

Prevalence and Risk Factors for Lateral Femoral Cutaneous Nerve Palsy in the Beach Chair Position.

PURPOSE: To report on the prevalence of lateral femoral cutaneous nerve (LFCN) palsy in patients who had undergone shoulder surgery in the beach chair position and to identify patient and surgical risk factors for its development. METHODS: We retrospectively reviewed the medical records of 397 consecutive patients who underwent either open or arthroscopic shoulder surgery in the beach chair position by a single surgeon. Patient demographic and surgical data including age, gender, weight, body mass index (BMI), diabetes, procedure duration, and anesthesia type (general, regional, regional/general) were recorded. LFCN palsy symptoms were recorded prospectively at the initial postoperative visit and identified clinically by focal pain, numbness, and/or tingling over the anterolateral thigh. RESULTS: The median patient age was 59.0 years and consisted of 158 males (40%) and 239 (60%) females. Five cases of LFCN palsy were identified for a prevalence of 1.3%. These patients had a higher median weight (108.9 kg vs 80.7 kg, P = .005) and BMI (39.6 vs 29.4, P = .005) than the patients who did not develop LFCN palsy. Median age, gender, diabetes, and surgical time were not significantly different between the groups. All cases resolved completely within 6 months. CONCLUSIONS: LFCN palsy after shoulder surgery in the beach chair position in our study has a prevalence of 1.3%, making it an uncommon complication. Patients with elevated BMI should be counseled about its possible occurrence after shoulder surgery in the beach chair position. LEVEL OF EVIDENCE: Level IV, prognostic.

Anatomic variability of the lateral femoral cutaneous nerve: Value of 3T MRI in identifying anomaly for surgical intervention.

The anatomic variability of the lateral femoral cutaneous nerve (LFC) creates diagnostic as well as therapeutic problems. A case is reported in which a woman with complaints of pain in the anterior and lateral thigh was referred for evaluation. Symptoms arose after an abdominal hysterectomy. Her symptoms were the territory of the LFC and not of the L2/L3 dermatome. She had a Tinel sign that was positive for the LFC skin territory, but this was located over the anterior superior iliac spine (ASIS), instead of medial to it. For this reason, a 3-Tesla MR neurography imaging was obtained. This showed the LFC as crossing over the ASIS, instead of being located either within or beneath the inguinal ligament. MRI imaging facilitated successful surgical treatment. This is the first report of the MR neurography and intraoperative appearance of this least common anatomic course for the LFC.

Lateral femoral cutaneous nerve transposition: Renaissance of an old concept in the light of new anatomy.

Meralgia paresthetica causes pain in the anterolateral thigh. Most surgical procedures involve nerve transection or decompression. We conducted a cadaveric study to determine the feasibility of lateral femoral cutaneous nerve (LFCN) transposition. In three cadavers, the LFCN was exposed in the thigh and retroperitoneum. The two layers of the LFCN canal superficial and deep to the nerve were opened. The nerve was then mobilized medially away from the ASIS, by cutting the septum medial to sartorius. It was possible to mobilize the nerve for 2 cm medial to the ASIS. The nerve acquired a much straighter course with less tension. A new technique of LFCN transposition is presented here as an anatomical feasibility study. The surgical technique is based on the new understanding of the LFCN canal. Clin. Anat. 30:409-412, 2017. © 2017 Wiley Periodicals, Inc.

Motor Neuron Pools of Synergistic Thigh Muscles Share Most of Their Synaptic Input.

Neural control of synergist muscles is not well understood. Presumably, each muscle in a synergistic group receives some unique neural drive and some drive that is also shared in common with other muscles in the group. In this investigation, we sought to characterize the strength, frequency spectrum, and force dependence of the neural drive to the human vastus lateralis and vastus medialis muscles during the production of isometric knee extension forces at 10 and 30% of maximum voluntary effort. High-density surface electromyography recordings were decomposed into motor unit action potentials to examine the neural drive to each muscle. Motor unit coherence analysis was used to characterize the total neural drive to each muscle and the drive shared between muscles. Using a novel approach based on partial coherence analysis, we were also able to study specifically the neural drive unique to each muscle (not shared). The results showed that the majority of neural drive to the vasti muscles was a cross-muscle drive characterized by a force-dependent strength and bandwidth. Muscle-specific neural drive was at low frequencies (<5 Hz) and relatively weak. Frequencies of neural drive associated with afferent feedback (6-12 Hz) and with descending cortical input (∼20 Hz) were almost entirely shared by the two muscles, whereas low-frequency (<5 Hz) drive comprised shared (primary) and muscle-specific (secondary) components. This study is the first to directly investigate the extent of shared versus independent control of synergist muscles at the motor neuron level. SIGNIFICANCE STATEMENT: Precisely how the nervous system coordinates the activity of synergist muscles is not well understood. One possibility is that muscles of a synergy share a common neural drive. In this study, we directly compared the relative strength of shared versus independent neural drive to synergistically activated thigh muscles in humans. The results of this analysis support the notion that synergistically activated muscles share most of their neural drive. Scientifically, this study addressed an important gap in our current understanding of how neural drive is delivered to synergist muscles. We have also demonstrated the feasibility of a novel approach to the study of muscle synergies based on partial coherence analysis of motor unit activity.

Giant Schwannoma of the Saphenous Nerve in The Distal Thigh: A Case Report.

CASE: Schwannomas are benign nerve myelin sheath tumors that can occur anywhere in the peripheral nervous system. It is very rare for Schwannomas to become malignant, but surgery is still the principal treatment to eliminate symptoms and to correctly diagnosis the tumor. We report an interesting case of a schwannoma of the saphenous nerve at the distal third of the posteromedial thigh: the patient complained of muscle weakness at left lower limb and vague anteromedial knee pain, mimicking a meniscal tear. Magnetic resonance images of the thigh showed a well-defined and oval mass lesion measuring 8.5 cm x 4.5 cm. Before investigating for a possible meniscal tear, we decided to remove the mass from the thigh, because we felt that it could itself be the cause of the mild pain complained about by the patient. Post-surgery, histological analysis conducted confirmed that this was a benign schwannoma. DISCUSSION: Schwannomas generally can be asymptomatic or present as a mass. The clinical presentation of this rare tumor makes the diagnosis difficult. CONCLUSION: This reported case is particularly interesting because of the rarity of the lesion localization along the course of the saphenous nerve. The combination of the location, and especially the large size of the tumor, led us to believe that there is a correlation with the particular clinical presentation.

Topographical relationships of intramuscular nerves and vessels of the motor endplates in the thigh and gluteal regions of human fetuses: an immunohistochemical study.

PURPOSE: The aim of this study was to describe topography of vessels and nerves in striated muscles to understand individual muscle function. MATERIALS AND METHODS: Immunohistochemistry for nerve and artery was used to examine the thigh and gluteal muscles of six human midterm fetuses. RESULTS: The supplying nerves often accompanied arteries along epimysium bundling muscle fibers as well as in the covering fascia surrounding the entire muscle mass. However, courses of nerve twigs were usually independent of those of vessels in muscle bundles. Notably, irrespective of whether or not the vascular bundle accompanied the nerves at the muscle surface or hilus, most of the motor endplate bands did not accompany the vessels. CONCLUSION: Since the motor endplates were low vascularised, a chemical induction of vessels for nerve terminal development (or the reversed induction) seemed unlikely in striated muscles. In contrast to proprioceptive neuromuscular facilitation, manual stimulation of the endplate bands may stimulate muscle activity without sympathetic reflexes through vessel-accompanying nerves.