Bilateral Persistent Sciatic Artery - An Infrequent Occurrence: A Case Report with Review of Literature.

A persistent sciatic artery (PSA) is a rare congenital vascular anomaly with an extremely low incidence of about 0.04%-0.06%. It is due to the persistence of the embryological axial limb artery, representing a continuation of the internal iliac artery into the thigh through the greater sciatic foramen below the piriformis muscle and down the thigh alongside the sciatic nerve. In normal embryologic development of the lower limb, the axial artery normally regresses after week 12. Persistent sciatic artery is often asymptomatic until a complication develops, it can be classified into two types, complete and incomplete. PSA can cause serious lower limb complications such as acute or critical limb ischemia.

RésuméUne artère sciatique persistante (APS) est une anomalie vasculaire congénitale rare avec une incidence extrêmement faible d'environ 0,04 % à 0,06 %. Cela est dû à la persistance de l'artère axiale embryologique des membres, représentant une continuation de l'artère iliaque interne dans la cuisse à travers la grande foramen sciatique sous le muscle piriforme et le long de la cuisse le long du nerf sciatique. Dans le développement embryologique normal de la partie inférieure membre, l'artère axiale régresse normalement après la semaine 12. L'artère sciatique persistante est souvent asymptomatique jusqu'à ce qu'une complication se développe, elle peut être classés en deux types, complets et incomplets. Le PSA peut entraîner des complications graves des membres inférieurs telles qu'une ischémie aiguë ou critique des membres.

Sciatic nerve fascicle differentiation on high-resolution ultrasound with histological verification: An ex vivo study.

INTRODUCTION/AIMS: The development of high-resolution ultrasound (HRUS) has enabled the depiction of peripheral nerve microanatomy in vivo. This study compared HRUS fascicle differentiation to the structural depiction in histological cross-sections (HCS). METHODS: A human cadaveric sciatic nerve was marked with 10 surgical sutures, and HRUS image acquisition was performed with a 22-MHz probe. The nerve was excised and cut into five segments for HCS preparation. Selected HCS were cross-referenced to HRUS, with sutures to improve orientation. Sciatic nerve and fascicle contouring were performed to assess nerve and fascicular cross-sectional area (CSA), fascicle count, and interfascicular distances. Three groups were defined based on HRUS fascicle differentiation in comparison to HCS, namely single fascicle (SF), fascicular cluster (FC), and no depiction (ND) group. RESULTS: On cross-referenced HRUS to HCS images, 58% of fascicles were differentiated. On HRUS, significantly larger fascicle CSA and smaller fascicle count were observed compared with HCS. Group analysis showed that 41% of fascicles were defined as SF, 47% as FC, and 12% as ND. The mean fascicle CSA in the ND group was 0.05 mm2. Compared with the SF, the FC had significantly larger fascicle CSA (1.2 ± 0.7 vs. 0.6 ± 0.4 mm2; p < .001) and shorter interfascicular distances (0.1 ± 0.04 vs. 0.5 ± 0.3 µm; p < .001). DISCUSSION: While HRUS can depict fascicular anatomy, only half of the fascicles visualized on HRUS directly correspond to single fascicles observed on HCS. The amount of interfascicular epineurium appears to influence the ability of HRUS to differentiate individual fascicles.

Anatomical Proximity Between Sciatic Nerve and Ischial Spine and its Relationship to the Development of Deep Gluteal Pain Syndrome.

OBJECTIVE: Deep gluteal syndrome (DGS) is a medical diagnosis in which the pathoanatomy of the subgluteal space contributes to pain. The growing recognition that gluteal neuropathies can be associated with the presence of a bone-neural conflict with irritation or compression may allow us to shed some light on this pathology. This study aims to determine whether the location of the sciatic nerve (SN) in relation to the ischial spine (IS) contributes to the development of DGS. METHODS: The SN - IS relationship was analyzed based on magnetic resonance imaging (MRI) in 15 surgical patients (SPs), who underwent piriformis release, and in 30 control patients who underwent MRI of the pelvis for reasons unrelated to sciatica. The SN exit from the greater sciatic foramen was classified as either zone A (medial to the IS); zone B (on the IS); or zone C (lateral to the IS). RESULTS: The SN was significantly closer to the IS in SPs than in MRI controls (P = 0.014). When analyzing patients of similar age, SNs in SPs were significantly closer (P = 0.0061) to the IS, and located in zone B significantly more (P = 0.0216) as compared to MRI controls. Patients who underwent surgery for piriformis release showed a significant decrease in pain postoperatively (P < 0.0001). CONCLUSIONS: The results from this study suggest that the relationship between the IS and SN may play a role in the development of DGS. This may also help establish which patients would benefit more from surgical intervention.

Ultrasonographic Contrast and Therapeutic Effects of Hydrogen Peroxide-Responsive Nanoparticles in a Rat Model with Sciatic Neuritis.

Purpose: Peripheral nerve damage lacks an appropriate diagnosis consistent with the patient's symptoms, despite expensive magnetic resonance imaging or electrodiagnostic assessments, which cause discomfort. Ultrasonography is valuable for diagnosing and treating nerve lesions; however, it is unsuitable for detecting small lesions. Poly(vanillin-oxalate) (PVO) nanoparticles are prepared from vanillin, a phytochemical with antioxidant and anti-inflammatory properties. Previously, PVO nanoparticles were cleaved by H2O2 to release vanillin, exert therapeutic efficacy, and generate CO2 to increase ultrasound contrast. However, the role of PVO nanoparticles in peripheral nerve lesion models is still unknown. Herein, we aimed to determine whether PVO nanoparticles can function as contrast and therapeutic agents for nerve lesions. Methods: To induce sciatic neuritis, rats were administered a perineural injection of carrageenan using a nerve stimulator under ultrasonographic guidance, and PVO nanoparticles were injected perineurally to evaluate ultrasonographic contrast and therapeutic effects. Reverse transcription-quantitative PCR was performed to detect mRNA levels of pro-inflammatory cytokines, ie, tumor necrosis factor-α, interleukin-6, and cyclooxygenase-2. Results: In the rat model of sciatic neuritis, PVO nanoparticles generated CO2 bubbles to increase ultrasonographic contrast, and a single perineural injection of PVO nanoparticles suppressed the expression of tumor necrosis factor-α, interleukin-6, and cyclooxygenase-2, reduced the expression of F4/80, and increased the expression of GAP43. Conclusion: The results of the current study suggest that PVO nanoparticles could be developed as ultrasonographic contrast agents and therapeutic agents for nerve lesions.

Evaluation of peripheral nerve injury according to the severity of damage using 18F-FDG PET/MRI in a rat Model of sciatic nerve injury.

OBJECTIVES: We ascertained that the PET scan may be a valuable imaging modality for the noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury through the previous study. This study aimed to assess peripheral nerve damage according to severity using18F-FDG PET/MRI of the rat sciatic nerve. METHODS: Eighteen rats were divided into three groups: 30-second (G1), 2-minute (G2), and 5-minute (G3) crushing injuries. The severity of nerve damage was measured in the third week after the crushing injury using three methods: the paw withdrawal threshold test (RevWT), standardized uptake values on PET (SUVR), and intensity analysis on immunohistochemistry (IntR). RESULTS: There were significant differences between G1 and G3 in both SUVR and IntR (p = 0.012 and 0.029, respectively), and no significant differences in RevWT among the three groups (p = 0.438). There was a significant difference in SUVR (p = 0.012), but no significant difference in IntR between G1 and G2 (p = 0.202). There was no significant difference between G2 and G3 in SUVR and IntR (p = 0.810 and 0.544, respectively). DISCUSSION: Although PET did not show results consistent with those of immunohistochemistry in all respects, this study demonstrated that PET uptake tended to increase with severe nerve damage. If this research is supplemented by further experiments, PET/MRI can be used as an effective diagnostic modality.

Nerve block, nerve damage, and fluid injection pressure: overturning the myth.

Histological and micro-ultrasound evidence rebuffs deep-rooted views on the nature of nerve block, nerve damage, and injection pressure monitoring. We propose that the ideal position of the needle tip for nerve block is between the innermost circumneural fascial layer and outer epineurium, with local anaesthetic passing circumferentially through adipose tissue. Thin, circumferential, subepineural expansion that is invisible to the naked eye was identified using micro-ultrasound, and could account for variability of outcomes in clinical practice. Pressure monitoring cannot differentiate between intrafascicular and extrafascicular injection. High injection pressure only indicates intraneural extrafascicular spread, not intrafascicular spread, because it is not possible to inject into the stiff endoneurium in most human nerves.

Magnetization transfer ratio of the sciatic nerve differs between patients in type 1 and type 2 diabetes.

BACKGROUND: Previous studies on magnetic resonance neurography (MRN) found different patterns of structural nerve damage in type 1 diabetes (T1D) and type 2 diabetes (T2D). Magnetization transfer ratio (MTR) is a quantitative technique to analyze the macromolecular tissue composition. We compared MTR values of the sciatic nerve in patients with T1D, T2D, and healthy controls (HC). METHODS: 3-T MRN of the right sciatic nerve at thigh level was performed in 14 HC, 10 patients with T1D (3 with diabetic neuropathy), and 28 patients with T2D (10 with diabetic neuropathy). Results were subsequently correlated with clinical and electrophysiological data. RESULTS: The sciatic nerve's MTR was lower in patients with T2D (0.211 ± 0.07, mean ± standard deviation) compared to patients with T1D (T1D 0.285 ± 0.03; p = 0.015) and HC (0.269 ± 0.05; p = 0.039). In patients with T1D, sciatic MTR correlated positively with tibial nerve conduction velocity (NCV; r = 0.71; p = 0.021) and negatively with hemoglobin A1c (r = - 0.63; p < 0.050). In patients with T2D, we found negative correlations of sciatic nerve's MTR peroneal NCV (r = - 0.44; p = 0.031) which remained significant after partial correlation analysis controlled for age and body mass index (r = 0.51; p = 0.016). CONCLUSIONS: Lower MTR values of the sciatic nerve in T2D compared to T1D and HC and diametrical correlations of MTR values with NCV in T1D and T2D indicate that there are different macromolecular changes and pathophysiological pathways underlying the development of neuropathic nerve damage in T1D and T2D. TRIAL REGISTRATION: https://classic. CLINICALTRIALS: gov/ct2/show/NCT03022721 . 16 January 2017. RELEVANCE STATEMENT: Magnetization transfer ratio imaging may serve as a non-invasive imaging method to monitor the diseases progress and to encode the pathophysiology of nerve damage in patients with type 1 and type 2 diabetes. KEY POINTS: • Magnetization transfer imaging detects distinct macromolecular nerve lesion patterns in diabetes patients. • Magnetization transfer ratio was lower in type 2 diabetes compared to type 1 diabetes. • Different pathophysiological mechanisms drive nerve damage in type 1 and 2 diabetes.

Design and implementation of a training programme on ultrasound-guided lower limb peripheral nerve blockade: An Advanced Clinical Practitioner's personal journey.

Increased demand in services, workforce pressures and continued financial constraints has resulted in a significant expansion in advanced clinical practice roles in the United Kingdom. This article will describe the personal experience of a perioperative Advanced Clinical Practitioner in the design and implementation of a training programme to achieve competence in ultrasound-guided lower limb peripheral nerve blockade. Three specific lower limb peripheral nerve blockade were included in the training programme, namely sciatic nerve block at the popliteal fossa, saphenous nerve block, and femoral nerve block. Key service drivers underpinning development, rationale for Advanced Clinical Practitioner involvement in lower limb peripheral nerve blockade and governance will also be discussed.

Neuromuscular choristoma and circumferential nerve territory desmoid-type fibromatosis: imaging findings supporting a nerve-driven mechanism.

OBJECTIVE: Neuromuscular choristoma (NMC) is a rare developmental malformation of peripheral nerve that is frequently associated with the development of a desmoid-type fibromatosis (DTF). Both NMC and NMC-DTF typically contain pathogenic CTNNB1 mutations and NMC-DTF develop only within the NMC-affected nerve territory. The authors aimed to determine if there is a nerve-driven mechanism involved in the formation of NMC-DTF from the underlying NMC-affected nerve. METHODS: Retrospective review was performed for patients evaluated in the authors' institution with a diagnosis of NMC-DTF in the sciatic nerve (or lumbosacral plexus). MRI and FDG PET/CT studies were reviewed to determine the specific relationship and configuration of NMC and DTF lesions along the sciatic nerve. RESULTS: Ten patients were identified with sciatic nerve NMC and NMC-DTF involving the lumbosacral plexus, sciatic nerve, or sciatic nerve branches. All primary NMC-DTF lesions were located in the sciatic nerve territory. Eight cases of NMC-DTF demonstrated circumferential encasement of the sciatic nerve, and one abutted the sciatic nerve. One patient had a primary DTF remote from the sciatic nerve, but subsequently developed multifocal DTF within the NMC nerve territory, including 2 satellite DTFs that circumferentially encased the parent nerve. Five patients had a total of 8 satellite DTFs, 4 of which abutted the parent nerve and 3 that circumferentially involved the parent nerve. CONCLUSIONS: Based on clinical and radiological data, a novel mechanism of NMC-DTF development from soft tissues innervated by NMC-affected nerve segments is proposed, reflecting their shared molecular genetic alteration. The authors believe the DTF develops outward from the NMC in a radial fashion or it arises in the NMC and wraps around it as it grows. In either scenario, NMC-DTF develops directly from the nerve, likely arising from (myo)fibroblasts within the stromal microenvironment of the NMC and grows outward into the surrounding soft tissues. Clinical implications for patient diagnosis and treatment are presented based on the proposed pathogenetic mechanism.

Endovascular revascularization of critical limb ischemia: the role of ultrasound-guided popliteal sciatic nerve block for the procedural pain management.

OBJECTIVES: To evaluate the impact of the ultrasound-guided popliteal sciatic nerve block (PSNB) for pain management during endovascular treatment of chronic limb-threatening ischemia (CLTI). MATERIAL AND METHODS: From November 2020 to January 2022, 111 CLTI patients that underwent endovascular procedures were prospectively enrolled in this prospective single-arm interventional study. Ultrasound-guided PSNB was used for procedural pain control. Pain intensity was evaluated throughout the procedure (baseline, 10 min after the block, pain peak, and at the end of the procedure) with the visual analog scale (VAS). RESULTS: Forty-six patients underwent above-the-knee revascularization (ATK), 20/111 below-the-knee (BTK) revascularization, 20/111 to both ATK and BTK revascularization. In 25 cases, no endovascular option was feasible at diagnostic angiography. The PSNB was effective in 96% of patients, with no need for further pain management with a statistically significant reduction (p < 0.0001) in the mean value of the VAS from 7.86 ± 1.81 (pre-procedural) to 2.04 ± 2.20 after 10 min from the block and up to 0.74 ± 1.43 at the end of the procedure (mean time 43 min). Only 1 complication related to the popliteal sciatic nerve block was registered (a temporary foot drop, completely resolved within 48 h). The time necessary to perform the block ranged between 4 and 10 min. CONCLUSION: Ultrasound-guided PSNB is a feasible and effective method to manage patients with rest pain and increase comfort and compliance during endovascular procedures. CLINICAL RELEVANCE STATEMENT: An ultrasound-guided popliteal sciatic nerve block is a safe, feasible, and effective technique to manage pain during endovascular treatment of chronic limb-threatening ischemia, especially in frail patients with multiple comorbidities who are poor candidates for deep sedoanalgesia or general anesthesia. KEY POINTS: Endovascular treatment of CTLI may require long revascularization sessions in patients with high levels of pain at rest, which could be exacerbated during the revascularization procedure. The PSNB is routinely used for anesthesia and analgesia during foot and ankle surgery, but the experience with lower limb revascularization procedures is very limited and not included in any international guideline. Ultrasound-guided PSNB is a feasible and effective regional anesthesia technique to relieve procedural and resting pain. Because of its safety and availability, every interventional radiologist should know how to perform this type of loco-regional anesthesia.

Adductor canal block techniques do not lead to involvement of sciatic nerve branches: a radiological cadaveric study.

INTRODUCTION: Low and high volume mid-thigh (ie, distal femoral triangle) and distal adductor canal block approaches are frequently applied for knee surgical procedures. Although these techniques aim to contain the injectate within the adductor canal, spillage into the popliteal fossa has been reported. While in theory this could improve analgesia, it might also result in motor blockade due to coverage of motor branches of the sciatic nerve. This radiological cadaveric study, therefore, investigated the incidence of coverage of sciatic nerve divisions after various adductor canal block techniques. METHODS: Eighteen fresh, unfrozen and unembalmed human cadavers were randomized to receive ultrasound-guided distal femoral triangle or distal adductor canal injections, with 2 mL or 30 mL injectate volume, on both sides (36 blocks in total). The injectate was a 1:10 dilution of contrast medium in local anesthetic. Injectate spread was assessed using whole-body CT with reconstructions in axial, sagittal and coronal planes. RESULTS: No coverage of the sciatic nerve or its main divisions was found. The contrast mixture spread to the popliteal fossa in three of 36 nerve blocks. Contrast reached the saphenous nerve after all injections, whereas the femoral nerve was always spared. CONCLUSIONS: Adductor canal block techniques are unlikely, even when using larger volumes, to block the sciatic nerve, or its main branches. Furthermore, injectate reached the popliteal fossa in a small minority of cases, yet if a clinical analgesic effect is achieved by this mechanism is still unknown.

Femoral vs sciatic nerve block to provide analgesia after medial open wedge high tibial osteotomy in the setting of multimodal analgesia: A randomized, controlled, single-blinded trial.

STUDY OBJECTIVE: Medial open wedge high tibial osteotomy (MOW HTO) is associated with moderate to severe postoperative pain. The proximal part of the tibia is innervated by branches from the femoral nerve anteriorly and the sciatic nerve posteriorly. There is a paucity of information regarding the optimal peripheral nerve block for postoperative analgesia with minimal impact on motor function. This study tested the hypothesis that a femoral nerve block provides superior analgesia to a sciatic nerve block after MOW HTO in the setting of multimodal analgesia. DESIGN: Randomized controlled single-blind trial. SETTING: Operating room, postoperative recovery area and ward, up to 6 postoperative months. PATIENTS: Fifty patients undergoing MOW HTO. INTERVENTIONS: Interventions were femoral or sciatic nerve block under ultrasound guidance. For each intervention, a total of 100 mg of ropivacaine was injected. Postoperative pain treatment followed a pre-defined protocol with intravenous patient-controlled analgesia of morphine, paracetamol, and ibuprofen. MEASUREMENTS: The primary outcome was intravenous morphine consumption at 24 h postoperatively. Secondary outcomes included rest and dynamic pain scores (on a numeric rating scale out of 10) at 2, 24 and 48 h postoperatively. Functional outcomes included the Short Form-12, Knee injury and Osteoarthritis Outcome Score, and International Knee Documentation Committee (IKDC) scores measured at 6 months postoperatively. MAIN RESULTS: Mean [95% confidence interval] i.v. morphine consumption at 24 postoperative hours were 24 mg [15 mg,33 mg] in the femoral nerve block group and 24 mg [16 mg,32 mg] in the sciatic nerve block group (p = 0.98). There were no significant differences in the secondary outcomes between groups. CONCLUSIONS: This trial failed to demonstrate that a femoral nerve block provides superior analgesia to a sciatic nerve block after MOW HTO under general anesthesia in the setting of multimodal analgesia. There was no significant difference in quality of life and functional outcomes at 6 months postoperatively between groups. Trial registry number:Clinicaltrials.com - NCT05728294; Kofam.ch - SNCTP000003048 | BASEC2018-01774.

The Anatomic Position of the Sciatic Nerve During Percutaneous Retrograde Posterior Column Fixation Is Determined by Hip Position.

OBJECTIVES: There are multiple established patient positions for placement of a percutaneous retrograde posterior column screw for fixation of acetabulum fractures. The sciatic nerve is at risk of injury during this procedure because it lies adjacent to the start point at the ischial tuberosity. The purpose of this study was to define how the position of the sciatic nerve, relative to the ischial tuberosity, changes regarding the patient's hip position. METHODS: In a cohort of 11 healthy volunteers, ultrasound was used to measure the absolute distance between the ischial tuberosity and the sciatic nerve. Measurements were made with the hip and knee flexed to 90 degrees to simulate supine and lateral positioning and with the hip extended to simulate prone positioning. In both positions, the hip was kept in neutral abduction and neutral rotation. RESULTS: The distance from the lateral border of the ischial tuberosity to the medial border of the sciatic nerve was greater in all subjects in the hip-flexed position versus the extended position. The mean distance was 17 mm (range, 14-27 mm) in the hip-extended position and 39 mm (range, 26-56 mm) in the hip-flexed position ( P < 0.001). CONCLUSIONS: The sciatic nerve demonstrates marked excursion away from the ischial tuberosity when the hip is flexed compared with when it is extended. The safest patient position for percutaneous placement of a retrograde posterior column screw is lateral or supine with the hip flexed to 90 degrees.

The effect of warming ropivacaine on ultrasound-guided subgluteal sciatic nerve block: a randomized controlled trial.

BACKGROUND: There is a long latent period for the sciatic nerve block before a satisfactory block is attained. Changes in the temperature of local anesthetics may influence the characters of the peripheral nerve block. This study was designed to evaluate the effect of warming ropivacaine on the ultrasound-guided subgluteal sciatic nerve block. METHODS: Fifty-four patients for distal lower limbs surgery were randomly allocated into warming group (group W, n = 27) or room tempeture group (group R, n = 27) with the ultrasound-guided subgluteal sciatic nerve block. The group W received 30 ml of ropivacaine 0.5% at 30℃ and the group R received 30 ml of ropivacaine 0.5% at 23℃. The sensory and motor blockade were assessed every 2 min for 30 min after injection. The primary outcome was the onset time of limb sensory blockade. RESULTS: The onset time of sensory blockade was shorter in group W than in group R (16 (16,18) min vs 22 (20,23) min, p < 0.001), and the onset time of motor blockade was also shorter in group W than in group R (22 (20,24) min vs 26 (24,28) min, p < 0.001). The onset time of sensory blockade for each nerve was shorter in group W than in group R (p < 0.001). No obvious differences for the duration of sensory and motor blockade and the patient satisfaction were discovered between both groups. No complications associated with nerve block were observed 2 days after surgery. CONCLUSIONS: Warming ropivacaine 0.5% to 30℃ accelerates the onset time of sensory and motor blockade in the ultrasound-guided subgluteal sciatic nerve block and it has no influence on the duration of sensory and motor blockade. TRIAL REGISTRATION: The trial was registered on October 3, 2022 in the Chinese Clinical Trial Registry ( https://www.chictr.org.cn/bin/project/edit?pid=181104 ), registration number ChiCTR2200064350 (03/10/2022).