A proof-of-concept study of ultrasound-guided continuous parasacral ischial plane block for postoperative pain control in patients undergoing total knee arthroplasty.

BACKGROUND: Continuous peripheral nerve blocks are widely used for anesthesia and postoperative analgesia in lower limb surgeries. The authors aimed to develop a novel continuous sacral plexus block procedure for analgesia during total knee arthroplasty. METHODS: The study comprised two stages. In Stage I, the authors built upon previous theories and technological innovations to develop a novel continuous sacral plexus block method, ultrasound-guided continuous parasacral ischial plane block (UGCPIPB) and subsequently conducted a proof-of-concept study to assess its effectiveness and feasibility. Stage II involved a historical control study to compare clinical outcomes between patients undergoing this new procedure and those receiving the conventional procedure. RESULTS: The study observed a 90% success rate in catheter placement. On postoperative day (POD) 1, POD2, and POD3, the median visual analog scale (VAS) scores were 3 (range, 1.5-3.5), 2.5 (1.6-3.2), and 2.7 (1.3-3.4), respectively. Furthermore, 96.3% of the catheters remained in place until POD3, as confirmed by ultrasound. The study revealed a significant increase in skin temperature and peak systolic velocity of the anterior tibial artery on the blocked side compared with those on the non-blocked side. Complications included catheter clogging in one patient and leakage at the insertion site in two patients. In Stage II, the novel technique was found to be more successful than conventional techniques, with a lower catheter displacement rate than the conventional procedure for continuous sciatic nerve block. CONCLUSION: UGCPIPB proved to be an effective procedure and safe for analgesia in total knee arthroplasty. CHINESE CLINICAL TRIAL REGISTRY NUMBER: ChiCTR2300068902.

Lumbosacral plexus and pudendal nerve magnetic resonance tractography: A systematic review of the clinical applications for pudendal neuralgia.

Diffusion tensor imaging (DTI) is commonly used to establish three-dimensional mapping of white-matter bundles in the supraspinal central nervous system. DTI has also been the subject of many studies on cranial and peripheral nerves. This non-invasive imaging technique enables virtual dissection of nerves in vivo and provides specific measurements of microstructural integrity. Adverse effects on the lumbosacral plexus may be traumatic, compressive, tumoral, or malformative and thus require dedicated treatment. DTI could lead to new perspectives in pudendal neuralgia diagnosis and management. We performed a systematic review of all articles or posters reporting results and protocols for lumbosacral plexus mapping using the DTI technique between January 2011 and December 2023. Twenty-nine articles published were included. Ten studies with a total of 351 participants were able to track the lumbosacral plexus in a physiological context and 19 studies with a total of 402 subjects tracked lumbosacral plexus in a pathological context. Tractography was performed on a 1.5T or 3T MRI system. DTI applied to the lumbosacral plexus and pudendal nerve is feasible but no microstructural normative value has been proposed for the pudendal nerve. The most frequently tracking parameters used in our review are: 3T MRI, b-value of 800 s/mm2, 33 directions, 3 × 3 × 3 mm3, AF threshold of 0.1, minimum fiber length of 10 mm, bending angle of 30°, and 3DT2 TSE anatomical resolution. Increased use of DTI could lead to new perspectives in the management of pudendal neuralgia due to entrapment syndrome, whether at the diagnostic, prognostic, or preoperative planning level. Prospective studies of healthy subjects and patients with the optimal acquisition parameters described above are needed to establish the accuracy of MR tractography for diagnosing pudendal neuralgia and other intrapelvic nerve entrapments.

[Advancements in Magnetic Resonance Neurography: Techniques, Sequences, and Standardization].

Magnetic resonance neurography requires varying imaging techniques based on the site of imaging and anticipated disease. In assessing the brachial and lumbosacral plexus, a three-dimensional (3D) spin echo method, such as 3D-short tau inversion recovery imaging, is frequently employed. It's beneficial to familiarize oneself with the imaging sequence and understand the appearance of normal images in advance. The imaging parameters used in our institute are provided below as a reference. When interpreting the images, pay close attention to nerve thickening, signal intensity changes, asymmetry between the left and right sides, and irregularities in nerve caliber. Efforts are underway to standardize qualitative assessments and quantify signals through technological advancements.

Real-time ultrasound-guided sacral plexus block combined with mild sedation for hemorrhoidectomy and hemorrhoidal artery ligation in a patient with amyotrophic lateral sclerosis: a case report.

BACKGROUND: Patients with amyotrophic lateral sclerosis present perioperative challenges for clinical anesthesiologists for anesthesia-associated complications. CASE PRESENTATION: A 54-year-old Han woman with a 2-year history of amyotrophic lateral sclerosis was scheduled for hemorrhoidectomy and hemorrhoidal artery ligation. We performed real-time ultrasound-guided sacral plexus block with dexmedetomidine under standard monitoring. The anesthesia method met the surgical demands and avoided respiratory complications during the procedures. There was no neurological deterioration after the surgery and 3 months after, the patient was discharged. CONCLUSIONS: Real-time ultrasound-guided sacral plexus block combined with mild sedation may be an effective and safe technique in patients with amyotrophic lateral sclerosis undergoing hemorrhoidectomy and hemorrhoidal artery ligation.

Clinical and ultrasound characteristics of deep endometriosis affecting sacral plexus.

OBJECTIVE: To describe the sonomorphological changes and appearance of deep endometriosis (DE) affecting the nervous tissue of the sacral plexus (SP). METHODS: This was a retrospective study of symptomatic patients who underwent radical resection of histologically confirmed DE affecting the SP and who had undergone preoperative transvaginal sonography (TVS) between 2019 and 2023. Lesions were described based on the terms and definitions of the International Deep Endometriosis Analysis (IDEA), International Ovarian Tumor Analysis (IOTA) and Morphological Uterus Sonographic Assessment (MUSA) groups. A diagnosis of DE affecting the SP on TVS was made when the sonographic criteria of DE were visualized in conjunction with fibers of the SP and the presence of related symptoms corresponding to sacral radiculopathy. Clinical symptoms, ultrasound features and histological confirmation were analyzed for each patient included. RESULTS: Twenty-seven patients with DE infiltrating the SP were identified in two contributing tertiary referral centers. Median age was 37 (range, 29-45) years and all patients were symptomatic and presented one or more of the following neurological symptoms: dysesthesia in the ipsilateral lower extremity (n = 17); paresthesia in the ipsilateral lower extremity (n = 10); chronic pelvic pain radiating in the ipsilateral lower extremity (n = 9); chronic pain radiating in the pudendal region (n = 8); and motor weakness in the ipsilateral lower extremities (n = 3). All DE lesions affecting the SP were purely solid tumors in the posterior parametrium in direct contact with, or infiltrating, the S1, S2, S3 and/or S4 roots of the SP. The median of the largest diameter recorded for each of the DE nodules was 35 (range, 18-50) mm. Echogenicity was non-uniform in 23 (85%) of the DE nodules, with all but one of these nodules containing hyperechogenic areas. The shape of the lesions was irregular in 24 (89%) cases. Only one lesion exhibited a lobulated form, with all other irregular lesions showing a spiculated appearance. An acoustic shadow was produced in 20 (74%) of the nodules, all of which were internal. On color or power Doppler examination, 21 (78%) of the nodules showed no signal (color score of 1). The remaining six (22%) lesions showed a minimal color content (color score of 2). According to pattern recognition, most DE nodules were purely solid, non-uniform, hypoechogenic nodules containing hyperechogenic areas, with internal shadows and irregular spiculated contours, and were poorly vascularized on color/power Doppler examination. CONCLUSION: The ultrasound finding of a parametrial, unilateral, solid, non-uniform, hypoechogenic nodule with hyperechogenic areas and possible internal shadowing, as well as irregular spiculated contours, demonstrating poor vascularization on Doppler examination in proximity to or involving the structures of the SP, indicates DE affecting the SP. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Improved 3D DESS MR neurography of the lumbosacral plexus with deep learning and geometric image combination reconstruction.

OBJECTIVE: To evaluate the impact of deep learning (DL) reconstruction in enhancing image quality and nerve conspicuity in LSP MRN using DESS sequences. Additionally, a geometric image combination (GIC) method to improve DESS signals' combination was proposed. MATERIALS AND METHODS: Adult patients undergoing 3.0 Tesla LSP MRN with DESS were prospectively enrolled. The 3D DESS echoes were separately reconstructed with and without DL and DL-GIC combined reconstructions. In a subset of patients, 3D T2-weighted short tau inversion recovery (STIR-T2w) sequences were also acquired. Three radiologists rated 4 image stacks ('DESS S2', 'DESS S2 DL', 'DESS GIC DL' and 'STIR-T2w DL') for bulk motion, vascular suppression, nerve fascicular architecture, and overall nerve conspicuity. Relative SNR, nerve-to-muscle, -fat, and -vessel contrast ratios were measured. Statistical analysis included ANOVA and Wilcoxon signed-rank tests. p < 0.05 was considered statistically significant. RESULTS: Forty patients (22 females; mean age = 48.6 ± 18.5 years) were enrolled. Quantitatively, 'DESS GIC DL' demonstrated superior relative SNR (p < 0.001), while 'DESS S2 DL' exhibited superior nerve-to-background contrast ratio (p value range: 0.002 to < 0.001). Qualitatively, DESS provided superior vascular suppression and depiction of sciatic nerve fascicular architecture but more bulk motion as compared to 'STIR-T2w DL'. 'DESS GIC DL' demonstrated better nerve visualization for several smaller, distal nerve segments than 'DESS S2 DL' and 'STIR-T2w DL'. CONCLUSION: Application of a DL reconstruction with geometric image combination in DESS MRN improves nerve conspicuity of the LSP, especially for its smaller branch nerves.

MSEF-Net: Multi-scale edge fusion network for lumbosacral plexus segmentation with MR image.

Nerve damage of spine areas is a common cause of disability and paralysis. The lumbosacral plexus segmentation from magnetic resonance imaging (MRI) scans plays an important role in many computer-aided diagnoses and surgery of spinal nerve lesions. Due to the complex structure and low contrast of the lumbosacral plexus, it is difficult to delineate the regions of edges accurately. To address this issue, we propose a Multi-Scale Edge Fusion Network (MSEF-Net) to fully enhance the edge feature in the encoder and adaptively fuse multi-scale features in the decoder. Specifically, to highlight the edge structure feature, we propose an edge feature fusion module (EFFM) by combining the Sobel operator edge detection and the edge-guided attention module (EAM), respectively. To adaptively fuse the multi-scale feature map in the decoder, we introduce an adaptive multi-scale fusion module (AMSF). Our proposed MSEF-Net method was evaluated on the collected spinal MRI dataset with 89 patients (a total of 2848 MR images). Experimental results demonstrate that our MSEF-Net is effective for lumbosacral plexus segmentation with MR images, when compared with several state-of-the-art segmentation methods.

Comparison Between a Modified Fast 3-Dimensional Turbo Spin-Echo and Diffusion-Weighted Imaging With Background Suppression in Evaluation of Lumbosacral Plexus and Its Branches.

OBJECTIVES: To compare the fast 3-dimensional NerveVIEW (3D NerveVIEW) with diffusion-weighted imaging with background suppression (DWIBS) in imaging of lumbosacral plexus and its branches. METHODS: A prospective study was performed on 30 healthy volunteers and patients who had undergone compressed sensing 3D NerveVIEW and DWIBS scans. There were 11 healthy subjects, 15 patients with lumbar disc herniation, and 4 patients with chronic inflammatory demyelinating polyradiculoneuropathy. Image quality was rated using a 4-point subjective scale. Quantitative evaluation of the nerves was done by measuring signal-to-noise ratio, contrast-to-noise ratio, and signal-to-background ratio, and the consistency in the measurements of nerve root cross-sectional areas was also assessed. The differences of signal-to-noise ratio, contrast-to-noise ratio, signal-to-background ratio, and the scores of image quality between 2 sequences were compared. RESULTS: The overall average image quality score of 3D NerveVIEW was significantly higher than that of DWIBS (2.72 ± 0.45 and 2.45 ± 0.81, respectively; P < 0.01). In terms of individual nerves, there was no significant difference between the 2 sequences in the display of the nerves from L2 to S1; however, 3D NerveVIEW was significantly better than DWIBS in demonstration of the S2-S3 nerves, as well as the nerve details. Regarding quantitative measurements, these sequences achieved comparable results with excellent interobserver agreements. CONCLUSION: Fast 3D NerveVIEW was superior to DWIBS with improved conspicuity of small distal nerves of S2-S3 and nerve details.

An Updated Review of Magnetic Resonance Neurography for Plexus Imaging.

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

Selective MR neurography-guided lumbosacral plexus perineural injections: techniques, targets, and territories.

The T12 to S4 spinal nerves form the lumbosacral plexus in the retroperitoneum, providing sensory and motor innervation to the pelvis and lower extremities. The lumbosacral plexus has a wide range of anatomic variations and interchange of fibers between nerve anastomoses. Neuropathies of the lumbosacral plexus cause a broad spectrum of complex pelvic and lower extremity pain syndromes, which can be challenging to diagnose and treat successfully. In their workup, selective nerve blocks are employed to test the hypothesis that a lumbosacral plexus nerve contributes to a suspected pelvic and extremity pain syndrome, whereas therapeutic perineural injections aim to alleviate pain and paresthesia symptoms. While the sciatic and femoral nerves are large in caliber, the iliohypogastric and ilioinguinal, genitofemoral, lateral femoral cutaneous, anterior femoral cutaneous, posterior femoral cutaneous, obturator, and pudendal nerves are small, measuring a few millimeters in diameter and have a wide range of anatomic variants. Due to their minuteness, direct visualization of the smaller lumbosacral plexus branches can be difficult during selective nerve blocks, particularly in deeper pelvic locations or larger patients. In this setting, the high spatial and contrast resolution of interventional MR neurography guidance benefits nerve visualization and targeting, needle placement, and visualization of perineural injectant distribution, providing a highly accurate alternative to more commonly used ultrasonography, fluoroscopy, and computed tomography guidance for perineural injections. This article offers a practical guide for MR neurography-guided lumbosacral plexus perineural injections, including interventional setup, pulse sequence protocols, lumbosacral plexus MR neurography anatomy, anatomic variations, and injection targets.

Prominent caudal shift of the lumbar plexus roots in spines with 18 thoracolumbar vertebrae.

PURPOSE: It remains unclear whether concomitant changes in the thoracolumbar (TL) vertebrae and lumbar plexus roots seen in experimental embryology are present in humans with different vertebral formulas, particularly in humans with 18 TL vertebrae. We thus investigated the human lumbar plexus root changes occurring in spines with an additional TL vertebra (18TL). METHODS: The lumbosacral plexus was macroscopically dissected in TL anomaly cases found in 161 computed tomography examinations. TL anomalies were distinguished as simple abnormalities in total TL count and abnormal TL trade-offs, i.e., exchanges between the last thoracic and first lumbar vertebrae, and were analyzed separately. RESULTS: One additional TL vertebra (7C_18TL_5S) was observed in 4/159 cases (2.5%), excluding cases with cervical and sacral abnormalities. Different from the unclear shifts of nerve roots in cases with 16TL and 17TL trade-offs, the 18TL trade-off tended to involve a caudal shift at the cranial limit, without event change at the caudal limit. In addition, only one nerve segment shift was reconfirmed with a change in two vertebral segments from 16 to 18 TL vertebrae. CONCLUSIONS: We revealed that concomitant changes in the lumbar plexus roots and vertebrae in humans with 18TL vertebrae may become more pronounced than those in humans with 16 or 17TL vertebrae, by approaching the typical mammalian TL formula (19TL). This study showed that the TL formula can be used to estimate changes in the lumbar plexus roots, which may assist in the planning of nerve-sparing spinal and pelvic surgery.

A non-inferiority study comparing the ultrasound-guided parasacral with a novel greater ischiatic notch plane approach in canine cadavers.

OBJECTIVE: To describe the gross and ultrasound anatomy of the parasacral region and an ultrasound-guided greater ischiatic notch (GIN) plane approach aimed at staining the lumbosacral trunk (LST) in canine cadavers. To evaluate if the ultrasound-guided GIN plane approach is non-inferior to the previously described ultrasound-guided parasacral approach at staining the LST. STUDY DESIGN: Prospective, randomized, non-inferiority experimental anatomic study. ANIMALS: A total of 17 (23.9 ± 5.2 kg) mesocephalic canine cadavers. METHODS: Anatomic and echographic landmarks, and the feasibility of performing a GIN plane technique were evaluated using two canine cadavers. The remaining 15 cadavers had each hemipelvis randomly assigned to be administered either parasacral or GIN plane injection of 0.15 mL kg-1 dye solution. The parasacral region was dissected after injections to assess the staining of LST, cranial gluteal nerve, pararectal fossa and pelvic cavity. The stained LST were removed and processed for histological evaluation of intraneural injections. A one-sided z-test for non-inferiority (non-inferiority margin -14%) was used to statistically evaluate the success of the GIN plane versus the parasacral approach. Data were considered statistically significant when p < 0.05. RESULTS: The GIN plane and parasacral approach stained the LST in 100% and 93.3% of the injections, respectively. The success rate difference between treatments was 6.7% [95% confidence interval, -0.6 to 19.0%; p < 0.001 for non-inferiority]. The GIN plane and parasacral injections stained the LST for 32.7 ± 16.8 mm and 43.1 ± 24.3 mm, respectively (p = 0.18). No evidence of intraneural injection was found. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided GIN plane technique resulted in nerve staining that was non-inferior to the parasacral technique and may be considered an alternative to the parasacral approach to block the LST in dogs.

Surgical Management of Lumbosacral Plexus Tumors.

BACKGROUND: Lumbosacral plexus tumors are uncommon, and because of their deep location and proximity to critical nerves subserving lower extremity function, understanding surgical approaches and short-term outcomes is important. METHODS: In a retrospective case series of lumbosacral plexus tumor surgeries performed from May 2000 to July 2021 by a single neurosurgeon, demographic information, clinical presentation, imaging studies, and operative outcomes were analyzed. RESULTS: A total of 42 patients with mean age of 48.3 years (range, 16-84 years) underwent surgery for a lumbosacral plexus tumor. Patients presented with leg pain (n = 25; 59.5%), followed by back/flank pain (n = 5; 11.9%), abdominal/pelvic pain (n = 5; 11.9%), leg weakness (n = 5; 11.9%), and leg numbness (n = 3; 7.1%). The most common tumor pathology was schwannoma (n = 20; 50.0%) followed by neurofibroma (n = 9; 22.5%). A retroperitoneal approach was used in all cases. Gross total resection was achieved in 23 (54.8%) patients, and only 1 (2.4%) patient exhibited symptomatic tumor recurrence after subtotal resection of a malignant tumor. Mean follow-up was 33.1 months (range, 1-96 months). Postoperatively, patient neurological status remained unchanged or improved (n = 37; 88.1%). Complications were infrequent, with 4 (9.5%) patients experiencing new sensory symptoms and 1 patient (2.4%) experiencing new anticipated motor weakness after en bloc resection of a malignant tumor. CONCLUSIONS: Indications for surgery include pain and/or neurological symptoms attributable to the lesion or large size if asymptomatic. Careful study of preoperative imaging is necessary to determine the best approach. Intraoperative nerve stimulation is essential to preserve function and guide extent of resection in benign tumors.

Exposure of the Lumbosacral Plexus by Using the Pararectus Approach: A Technical Note.

BACKGROUND: Surgical exploration of the lumbosacral plexus is challenging. Previously described approaches reach from invasive open techniques with osteotomy of the ilium to laparoscopic techniques. OBJECTIVE: To describe a novel surgical technique to explore lumbosacral plexopathies such as benign nerve tumors or iatrogenic lesions of the lumbosacral plexus in 4 case examples. METHODS: We retrospectively evaluated 4 patients suffering from pathologies or injuries of the lumbosacral plexus between 2017 and 2019. The mean follow-up period after surgery was 23.5 (range 11-52) months. All patients underwent neurolysis of the lumbosacral plexus using the single incision, intrapelvic, extraperitoneal pararectus approach. RESULTS: In all patients, the pathology of the lumbosacral plexus was successfully visualized, proving feasibility of the extraperitoneal pararectus approach for this indication. There were no major complications, and all patients recovered well. CONCLUSION: The pararectus approach allows excellent visualization of the lumbar plexus and intrapelvic lesions of the femoral and sciatic nerves.

A Lumbar Paravertebral Space Ultrasound Lumbar Plexus Block Technique for Hip Fracture Surgery in the Elderly.

Ultrasound imaging of peripheral nerves is challenging in elderly population. In cases involving the lumbar plexus (LP), we have employed ultrasound imaging and neurostimulation guidance for successful localization and block of the LP. The postero-medial segment of the psoas muscle (PSM), superior to the vertebral body and anterior to the transverse process ("corner pocket") was used as an imaging landmark for the implementation of the LP block. By advancing the needle through the lateral abdominal wall into the "corner pocket" we were afforded a seamless advancement of the needle into the postero-medial segment of the PSM, which is the standard anatomic position of LP in the PSM. Forty-eight patients in whom ultrasound imaging of the LP was not feasible, but the "corner pocket" was clearly depicted were included in the study. LP block characteristics and adverse events were recorded. The LP was localized in 43/48 patients. The average imaging, needling, and performance times to complete the block were 51 sec (range, 6-180 sec), 81 sec (range, 16-236 sec), and 132 sec (range, 24-270 sec), respectively. The median number of needle redirections per patient was 5.5 (range, 1-13). The local anesthetic spread was visualized in the postero-medial segment of the PSM in 39/43 patients. No complications were recorded. The imaging, needling, and performance times, as well as the number of needle passes did not significantly differ between obese and non-obese patients. In conclusion, in cases with challenging ultrasound imaging of the LP, ultrasound-assisted LP block can be accomplished through the lateral abdominal wall by using as an imaging landmark the "corner pocket" at the postero-medial quadrant of the PSM.

Residual-atrous attention network for lumbosacral plexus segmentation with MR image.

Accurate segmentation of the lumbosacral plexus is a crucial step for diagnosis and analysis of nerve damage in clinical. Due to the extremely low contrast and complicated structure around the lumbosacral plexus, it has been remaining a challenging task to effectively segment the lumbosacral plexus from spinal MR images. Even though several deep learning methods for spine segmentation have been developed, most of them only pay attention to the segmentation of vertebral bodies and intervertebral discs rather than nerves. To solve these problems, in this paper, we propose a residual-atrous attention network (RA2-Net) for lumbosacral plexus segmentation with MR images. Specifically, the RA2-Net consists of three main parts, (1) the atrous encoder module is employed to learn multi-scale contextual features from MR images in the encoder, (2) the residual skip connection operation is used to integrate the features with high-resolution spatial details in the encoder and the high-level contextual features in the decoder, and (3) the scale attention block is proposed for fusing the multi-scale high-level features in the decoder. We perform our proposed RA2-Net for the lumbosacral plexus segmentation on the collected spinal MRI dataset with 10 patients (a total of 236 MRI scans). Extensive experiments demonstrate that our RA2-Net achieves better performance in lumbosacral plexus segmentation with MR images when compared with several state-of-the-art methods.