Ultrasonography in Pain Medicine: A Critical Review

Sensors and Devices Guided by Artificial Intelligence for Personalized Pain Medicine

Personalized pain medicine aims to tailor pain treatment strategies for the specific needs and characteristics of an individual patient, holding the potential for improving treatment outcomes, reducing side effects, and enhancing patient satisfaction. Despite existing pain markers and treatments, challenges remain in understanding, detecting, and treating complex pain conditions. Here, we review recent engineering efforts in developing various sensors and devices for addressing challenges in the personalized treatment of pain. We summarize the basics of pain pathology and introduce various sensors and devices for pain monitoring, assessment, and relief. We also discuss advancements taking advantage of rapidly developing medical artificial intelligence (AI), such as AI-based analgesia devices, wearable sensors, and healthcare systems. We believe that these innovative technologies may lead to more precise and responsive personalized medicine, greatly improved patient quality of life, increased efficiency of medical systems, and reducing the incidence of addiction and substance use disorders.

Evaluating the Extent of Ultrasound-Guided Cervical Selective Nerve Root Block in the Lower Cervical Spine: Evidence Based on Computed Tomography Images

Objective

To verify the injectate dispersal patterns (IDP) and therapeutic outcome of ultrasound-guided cervical selective nerve root block (UG-SCNRB) in treating cervical radiculopathy (CR).

Methods

Overall, 18 CR patients were recruited to undergo UG-SCNRB in the CT room. Following placement of the puncture needle tip between the target nerve root and posterior tubercle, 3 mL of the drug was administered per root (0.33% lidocaine 0.5 mL + Compound betamethasone injection 0.5mL + methylcobalamin injection 1mL + iohexol 1mL). Subsequently, the IDP was assessed on postintervention CT scan images.

Results

In all, 18 participants were analyzed. We injected 21 target cervical nerve roots, namely, 1 C4 nerve, 9 C5 nerves, and 11 C6 nerves. Among the IDPs on postintervention CT scan images, two IDPs were most prevalent, namely, the contrast spread into the extraforaminal spaces (Zone I, the interscalene) in 100% (21/21) of cases, and the foraminal space spread (Zone II) in 61.90% (13/21) of cases. The injectate spread into the epidural spaces (Zone III) in only 2 out of 21 cases (9.52%). The pain relief was significantly improved two hours after surgery, compared to the preoperative VAS pain scores (2 hours, 1.39±0.50 vs VAS at baseline, P<0.01). The VAS pain scores during follow-up were significantly lower than preoperation (1 weeks, 1.94±0.54 vs VAS at baseline; 2 weeks, 2.61±0.70, P<0.01 vs VAS at baseline; 4 weeks, 2.67±0.59, P<0.01 vs VAS at baseline).

Conclusion

We verified, via CT imaging, that the UG-SCNRB drug diffusion was within safe range (the injectate mainly spread to the extraforaminal spaces), and without any serious complications, such as, intravascular drug injection, extensive diffusion of the epidural space, and general spinal anesthesia.

Ultrasound-guided monopolar versus bipolar radiofrequency ablation for genicular nerves in chronic knee osteoarthritis pain: A randomized controlled study

Background

This study compared between monopolar and bipolar radiofrequency (RF) ablation of the genicular nerves using ultrasound guidance (USG) in chronic knee osteoarthritis pain.

Material and methods

This was a prospective, randomized, double-blind study. Fifty patients with knee osteoarthritis pain were equally randomized to either monopolar or bipolar groups. The primary outcome was visual analogue score (VAS). The secondary outcomes were the proportion of successful responders with a reduction of 50% of VAS score at 12 and 24 weeks, the procedure time and pain and oxford knee score (OKS).VAS and OKS were recorded at 1, 4, 12, 24 weeks after intervention. Any complications were reported.

Results

Mean VAS score in bipolar group was (p < 0.05) lower than monopolar group at 12 weeks [4.84 ± 0.62 Vs. 3.56 ± 0.71] and 24 weeks [5.44 ± 0.82 Vs. 3.96 ± 0.79]. The Proportion of successful responders with a reduction of at least 50% of VAS score were more in bipolar group than monopolar group at 12 weeks (80% Vs. 12%) and 24 weeks (44% Vs. 4%). Mean OKS score in bipolar group was (p < 0.05) lower than monopolar group at 12 weeks [26 ± 3 Vs. 34 ± 3] and 24 weeks [27 ± 3 Vs. 35 ± 3].The procedure time and pain were (p < 0.05) lower in monopolar than bipolar group. The complications were similar in both groups.

Conclusion

USG bipolar RF ablation is more effective than monopolar RF ablation in controlling knee osteoarthritis pain as for the duration and severity of pain without fluoroscopic confirmation.

•

A study on 50 patient undergoing USG RFA of genicular nerves of 2 groups; Monopolar or bipolar RFA.

•

Bipolar RFA is more effective than Monopolar RFA.

•

USG radiofrequency ablation is alternative to fluoroscopic RFA.

•

No significant difference between the two groups according to complications.

Ultrasound-guided cervical selective nerve root injections: a narrative review of literature

BACKGROUND/IMPORTANCE

Ultrasound (US)-guided cervical selective nerve root injections (CSNRI) have been proposed as an alternative to fluoroscopic (FL) -guided injections. When choosing US guidance, the proceduralist should be aware of potential issues confirming vertebral level, be clear regarding terminology, and up to date regarding the advantages and disadvantages of US-guided CSNRI.

OBJECTIVE

Review the accuracy and effectiveness of US guidance in avoiding vascular puncture (VP) and/or intravascular injection (IVI) during CSNRI.

EVIDENCE REVIEW

Queries included PubMed, CINAHL and Embase databases from 2005 to 2019. Three authors reviewed references for eligibility, abstracted data, and appraised quality.

FINDINGS

The literature demonstrates distinct safety considerations and limited evidence of the effectiveness of US guidance in detecting VP and/or IVI. As vascular flow and desired injectate spread cannot be visualized with US, the use of real-time fluoroscopy, and if needed digitial subraction imaging, is indicated in cervical transforaminal epidural injections (CTFEIs). Given the risk of VP and/or IVI, the ability to perform and to retain FL images to document that the procedure was safely conducted is valuable in CTFEIs.

CONCLUSION

US guidance remains to be proven as a non-inferior alternative to FL guidance or other imaging modalities in the prevention of VP and/or IVI with CTFEIs or cervical selective nerve root blocks. There is a paucity of adequately powered clinical studies evaluating the accuracy and effectiveness of US guidance in avoiding VP and/or IVI. US-guided procedures to treat cervical radicular pain has limitations in visualization of anatomy, and currently with the evidence available is best used in a combined approach with FL guidance.

<p>Blood Flow Index and Skin Temperature Measured by Laser Speckle Contrast Imaging and Infrared Thermography After Specific Ultrasound-Guided Blocking of the C6, C7 Nerve Root: A Case Report</p>

Ultrasound-guided cervical nerve root block is the technique of injecting local anesthetic or steroid into the intertubercular groove outside of the cervical foramen under real-time ultrasound guidance. It has established diagnostic and therapeutic employment for patients suffering symptoms caused by cervical disc disorders and foraminal stenosis. Measures of selective nerve root blockade would have vital clinical utility, especially in multilevel disease or combined with atypical symptoms, where subjective assessment is difficult. This case reported a 47-year-old male patient who suffered from severe radicular pain confined to the index and middle fingers, with weakness of the right upper extremity. He was successfully treated with selective C6, C7 nerve root under ultrasound guidance. For confirmation of the proper analgesia range, laser speckle contrast imaging (LSCI) and infrared thermography (IT) were both constructed over the dorsum of the hands and forearms during the procedure. The results of the off-line analysis suggested LSCI and IT might be considered as alternative measurements for the selective cervical nerve root.

Efficacy and Safety of Ultrasound-Guided Radiofrequency Treatment for Chronic Pain in Patients with Knee Osteoarthritis: A Systematic Review and Meta-Analysis

Background

Knee osteoarthritis (KOA) is a common degenerative disease associated with joint dysfunction and pain. Ultrasound-guided radiofrequency (RF) may be a promising therapy in the treatment of chronic pain for KOA patients.

Objective

To evaluate the efficacy and safety of ultrasound-guided RF treatment for chronic pain in patients with KOA.

Design

A systematic review was conducted, and a meta-analysis was carried out when possible. Setting. We examined the studies evaluating the clinical efficiency of ultrasound-guided RF on chronic pain in KOA population.

Method

A systematic review for the efficacy and safety of ultrasound-guided RF treatment for pain management of KOA patients was carried out in PubMed, EMBASE, Cochrane Library, Web of Science, Wanfang Data, and China National Knowledge Infrastructure (CNKI) from the date of inception to February 2020, and a meta-analysis was conducted. The primary outcomes of pain intensity (visual analogue scale or numerical rating scale) and knee function [the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)] were evaluated from baseline to various follow-up times by random-effects model. Heterogeneity was assessed by I ² statistic and the potential sources of heterogeneity by subgroup and metaregression analyses, respectively.

Results

Eight publications with 256 patients were included in the meta-analysis. RF could relieve pain with -4.196 of pooled mean difference and improve knee function by decreasing 23.155 points in WOMAC. Three patients had ecchymosis, two with hypoesthesia and one with numbness after the procedure, and improved within 6 months. Furthermore, study design and treatment target were the sources of heterogeneity by subgroup and metaregression analyses, accounting for 37% and 74% of variances, respectively. Target of genicular nerve achieved better pain relief than intra-articular or sciatic nerve. Sensitivity analysis showed that removal of any single study was unlikely to overturn the findings. Limitations. There were some limitations in the study. Firstly, the small number of relevant studies limited the confidence level of the meta-analysis. Also, the significant heterogeneity may not be explained due to the limited data. Secondly, the direct comparison of two different guidance methods (ultrasound vs. fluoroscopy) for RF therapy is lacking. In addition, the outcomes were blindly assessed in the meta-analysis from all studies according to evaluation of bias, which could affect the reality of the data. Finally, most of the studies only provided short follow-up times, so we could not analyze the long-term effectiveness of ultrasound-guided RF in the treatment of patients with KOA.

Conclusions

Ultrasonography is an effective, safe, nonradiative, and easily applicable guidance method for RF in pain relief and functional improvement in KOA patients.

Ultrasound-Assisted Lumbar Interlaminar Epidural Dye Injection and Evaluation of Its Distribution by Anatomical Dissection

Background: Epidural steroid injections are frequently used to treat lumbar radicular pain. However, the spread of a solute in the epidural space needs further elucidation. We aimed at assessing the distribution of green dye in the epidural space after lumbar epidural injection on cadavers.

Methods: We performed ultrasound-guided injections of green dye between lumbar vertebrae 4 and 5 in 24 cadavers. The cadavers were randomly divided into group A and B according to the volume of injected dye; 3 ml in group A (n = 13) and 6 ml in group B (n = 11). Accuracy of the needle insertion and patterns and distributions of the spread were compared between the groups. After local dissection, we examined the spread of dye in dorsal and ventral epidural spaces and presented the distribution as whole numbers and quartiles of intervertebral segments. Mann-Whitney U Test was used to compare distribution of dye spread between groups A and B. Wilcoxon Signed-Rank Test was used to compare the spread of dye in cranial and caudal direction within the group. We considered P < 0.05 as significant.

Results: Data were obtained from all 24 cadavers. Median levels of dorsal cranial dye distribution in groups A and B were 2 and 4 (P = 0.02), respectively. In the dorsal caudal−2 and 2, respectively (P = 0.04). In the ventral epidural space cranial dye spread medians were−0 and 2 in groups, respectively (P = 0.04). Ventral caudal spread was 0 and 1, respectively (P = 0.03). We found a significant difference between cranial and caudal dye distribution in group B (P < 0.05). In group A the dye spread was bilateral. In group B cranial and caudal dye spread was observed.

Conclusions: Ventral dye flow was observed in 50% of injections. Bilateral spread of dye occurred in 63%, and more often in group A. Cranial spread was slightly higher than caudal spread in group A despite a smaller injected volume, and significantly higher in group B following a larger volume.

Clinical evaluation of the shape of the suprascapular notch--an ultrasonographic and computed tomography comparative study: Application to shoulder pain syndromes

The most common site of suprascapular nerve compression and injury is the suprascapular notch. The aim of this study was to assess the sensitivity and specificity of sonography in determining the type of suprascapular notch (SSN). Thirty randomized patients (60 upper extremities) underwent USG examination of the shoulder area. The results were further compared with three-dimensional reconstructions of the scapulae obtained through CT examination to place the SSNs within a fivefold classification. For identification of type I, the sensitivity was 73.3% and the specificity 97.8%. For identification of type III, the values was 96.9% and 85.7%, respectively. Type II was not found in USG examination. Discrimination between type IV and V was not possible. The mean distance between the line connecting the edges of the SSN and the skin was 38 mm in right-handed patients and 34 mm in ambidextrous subjects. Ultrasonographic examination of the SSN is characterized by high specificity for type I, and high sensitivity for type III SSN. Discrimination between type IV and V of the SSN is not recommended based on sonographic evaluation.

Ultrasonography of the cervical spine: an in vitro anatomical validation model

BACKGROUND

Anatomical validation studies of cervical ultrasound images are sparse. Validation is crucial to ensure accurate interpretation of cervical ultrasound images and to develop standardized reliable ultrasound procedures to identify cervical anatomical structures. The aim of this study was to acquire validated ultrasound images of cervical bony structures and to develop a reliable method to detect and count the cervical segmental levels.

METHODS

An anatomical model of a cervical spine, embedded in gelatin, was inserted in a specially developed measurement device. This provided ultrasound images of cervical bony structures. Anatomical validation was achieved by laser light beams projecting the center of the ultrasound image on the cervical bony structures through a transparent gelatin.

RESULTS

Anatomically validated ultrasound images of different cervical bony structures were taken from dorsal, ventral, and lateral perspectives. Potentially relevant anatomical landmarks were defined and validated. Test/retest analysis for positioning showed a reproducibility with an intraclass correlation coefficient for single measures of 0.99. Besides providing validated ultrasound images of bony structures, this model helped to develop a method to detect and count the cervical segmental levels in vivo at long-axis position, in a dorsolateral (paramedian) view at the level of the laminae, starting from the base of the skull and sliding the ultrasound probe caudally.

CONCLUSIONS

Ultrasound bony images of the cervical vertebrae were validated with an in vitro model. Anatomical bony landmarks are the mastoid process, the transverse process of C1, the tubercles of C6 and C7, and the cervical laminae. Especially, the cervical dorsal laminae serve best as anatomical bony landmarks to reliably detect the cervical segmental levels in vivo.

Ultrasound-guided versus computed tomography-controlled periradicular injections in the middle and lower cervical spine: a prospective randomized clinical trial

PURPOSE

We conducted this study to evaluate accuracy, time saving, radiation doses, safety, and pain relief of ultrasound (US)-guided periradicular injections versus computed tomography (CT)-controlled interventions in the cervical spine in a prospective randomized clinical trial.

METHODS

Forty adult patients were consecutively enrolled and randomly assigned to either a US or a CT group. US-guided periradicular injections were performed on a standard ultrasound device using a broadband linear array transducer. By basically following the osseous landmarks for level definition in "in-plane techniques", a spinal needle was advanced as near as possible to the intended, US-depicted nerve root. The respective needle tip positioning was then verified by CT. The control group underwent CT-guided injections, which were performed under standardized procedures using the CT-positioning laser function.

RESULTS

The accuracy of US-guided interventions was 100%. The mean time to final needle placement in the US group was 02:21 ± 01:43 min:s versus 10:33 ± 02:30 min:s in the CT group. The mean dose-length product radiation dose, including CT confirmation for study purposes only, was 25.1 ± 16.8 mGy cm for the US group and 132.5 ± 78.4 mGy cm for the CT group. Both groups showed the same significant visual analog scale decay (p < 0.05) without "inter-methodic" differences of pain relief (p > 0.05).

CONCLUSIONS

US-guided periradicular injections are accurate, result in a significant reduction of procedure expenditure under the avoidance of radiation and show the same therapeutic effect as CT-guided periradicular injections.

The American Society of Regional Anesthesia and Pain Medicine, the European Society of Regional Anaesthesia and Pain Therapy, and the Asian Australasian Federation of Pain Societies Joint Committee recommendations for education and training in ultrasound-guided interventional pain procedures

The use of ultrasound in pain medicine for interventional axial, nonaxial, and musculoskeletal pain procedures is rapidly evolving and growing. Because of the lack of specialty-specific guidelines for ultrasonography in pain medicine, an international collaborative effort consisting of members of the Special Interest Group on Ultrasonography in Pain Medicine from the American Society of Regional Anesthesia and Pain Medicine, the European Society of Regional Anaesthesia and Pain Therapy, and the Asian Australasian Federation of Pain Societies developed the following recommendations for education and training in ultrasound-guided interventional pain procedures. The purpose of these recommendations is to define the required skills for performing ultrasound-guided pain procedures, the processes for appropriate education, and training and quality improvement. Training algorithms are outlined for practice- and fellowship-based pathways. The previously published American Society of Regional Anesthesia and Pain Medicine and European Society of Regional Anaesthesia and Pain Therapy education and teaching recommendations for ultrasound-guided regional anesthesia served as a foundation for the pain medicine recommendations. Although the decision to grant ultrasound privileges occurs at the institutional level, the committee recommends that the training guidelines outlined in this document serve as the foundation for educational training and the advancement of the practice of ultrasonography in pain medicine.

Ultrasound-guided pain interventions - a review of techniques for peripheral nerves

Ultrasound has emerged to become a commonly used modality in the performance of chronic pain interventions. It allows direct visualization of tissue structure while allowing real time guidance of needle placement and medication administration. Ultrasound is a relatively affordable imaging tool and does not subject the practitioner or patient to radiation exposure. This review focuses on the anatomy and sonoanatomy of peripheral non-axial structures commonly involved in chronic pain conditions including the stellate ganglion, suprascapular, ilioinguinal, iliohypogastric, genitofemoral and lateral femoral cutaneous nerves. Additionally, the review discusses ultrasound guided intervention techniques applicable to these structures.

Suprascapular nerve block: a narrative review

Suprascapular nerve blockade (SSNB) is a simple and safe technique for providing relief from various types of shoulder pain, including rheumatologic disorders, cancer, and trauma pain, and postoperative pain due to shoulder arthroscopy. Posterior, superior, and anterior approaches may be used, the most common being the posterior. Recently, an ultrasound-guided approach has been described. In this review, the basic anatomy of the suprascapular nerve will be described. The different techniques of SSNB and indications for SSNB will be discussed. The complications of SSNB and outcomes of SSNB on the management of acute and chronic shoulder pain will be reviewed.

Spine ultrasonography: interventions and diagnostics

SUMMARY Ultrasound-guided procedures are well established and utilized in the regional anesthesia and radiology practice. Conversely, there have been considerable difficulties in implementation of ultrasound in pain medicine. Ultrasonography has to compete with the more established modalities such as fluoroscopy and computed tomography; however, ultrasound has the advantage of radiation safety and point-of care imaging. It also allows direct visualization of tissue planes, blood vessels and nerves. Ultrasound-guided spine interventions are technically feasible and reasonably accurate when validated with conventional radiological modalities. Epidural, zygapophysial joint and caudal injection techniques have been published. The main pitfall of the ultrasound-guided spinal procedures lies in the inability to diagnose intravascular injections. Future technological improvements will help to solve this problem. Diagnostic spinal sonography may also contribute to the practice of medicine helping in the clinical workup of scoliosis and paraspinal pathology.

Ultrasound-guided lumbar transforaminal injections: feasibility and validation study

STUDY DESIGN

Preclinical feasibility study.

OBJECTIVE

Evaluation and validation of ultrasound-guided lumbar transforaminal injections.

SUMMARY OF BACKGROUND DATA

Lumbar transforaminal injections are routinely implemented in the interventional management of spinal radicular pain. Typically, these injections are administered under fluoroscopy or computed tomography. Although radiological guidance provides anatomical precision and accuracy, it is associated with radiation exposure and cannot be performed during outpatient visits or at bedside. Ultrasound-guided techniques have been previously described; however, the methodological generalizability remained unknown and validation against routine fluoroscopy has never been conducted on multiple spinal levels.

METHODS

We addressed the procedural accuracy of ultrasound-guided lumbar transforaminal injections and proposed anatomically sound approach. Fluoroscopic validation was performed.

RESULTS

Of the 50 planned injections, 46 procedures were performed. L5/S1 foraminal access was impossible in 4 cases (8%). Fluoroscopy confirmed the correct foraminal placement in all 46 injections (100%). The contrast-spread pattern was intraforaminal in 42 cases (91.3%) and extraforaminal (nerve root) in 4 cases (8.7%). When intraforaminal pattern was detected on anteroposterior image, lateral fluoroscopy demonstrated ventral epidural flow in all occasions. In 3 cases, intravascular injection was detected (6.5%).

CONCLUSION

Ultrasound-guided lumbar transforaminal injections are accurate and feasible in the preclinical setting.

Can parturients identify the midline during neuraxial block placement?

STUDY OBJECTIVE

To determine whether parturients can reliably identify their midline during epidural or spinal needle insertion, and to determine whether parturient feedback helps the anesthesiologist successfully identify the midline.

DESIGN

Survey instrument completed by anesthesiologists.

SETTING

Labor and delivery unit of a university-based, tertiary-care hospital.

MEASUREMENTS

Completed questionnaires were obtained for 554 of 904 (61.3%) neuraxial blocks. Data were collected on the type of neuraxial block, number of needle redirections required to identify the midline, the patient's height and weight, the patient's position during block placement, whether the patient was questioned for assistance identifying the midline, and if so, how helpful the patient was in redirecting the needle to locate the epidural or subarachnoid space.

MAIN RESULTS

The anesthesiologist requested the assistance of 194 patients (35.0%) for needle location. Of those questioned, the anesthesiologist reported 128 instances (66.0%) when the patient's response was helpful in identification of the midline. Morbidly obese parturients (BMI > 35 kg/m²) were questioned more often than their non-morbidly obese counterparts (48.9% vs. 30.5%; P < 0.0005). Of those morbidly obese parturients who were questioned (n = 64), 76.6% were reported by the anesthesiologist to be helpful.

CONCLUSIONS

Most patients, including morbidly obese patients, are helpful in identifying the midline during neuraxial anesthesia.

Ultrasound-guided, percutaneous peripheral nerve stimulation: technical note

BACKGROUND

Peripheral nerve stimulation is a form of neuromodulation that applies electric current to peripheral nerves to induce stimulation paresthesias within the painful areas.

OBJECTIVE

To report a method of ultrasound-guided, percutaneous peripheral nerve stimulation. This technique utilizes real-time imaging to avoid injury to adjacent vascular structures during minimally invasive placement of peripheral nerve stimulator electrodes.

MATERIAL AND METHODS

We describe a patient that presented with chronic, bilateral foot pain following multiple foot surgeries, for whom a comprehensive, pain management treatment strategy had failed. We utilized ultrasound-guided, percutaneous tibial nerve stimulation at a thigh level to provide durable pain relief on the right side, and open peripheral nerve stimulation on the left.

RESULTS

The patient experienced appropriate stimulation paresthesias and excellent pain relief on the plantar aspect of the right foot with the percutaneous electrode. On the left side, we were unable to direct the stimulation paresthesias to the sole of the foot, despite multiple electrode repositionings. A subsequent, open placement of a left tibial nerve stimulator was performed. This revealed that the correct electrode position against the tibial nerve was immediately adjacent to the popliteal artery, and was thus not appropriate for percutaneous placement.

CONCLUSION

We describe a method of ultrasound-guided peripheral nerve stimulation that avoids the invasiveness of electrode placement via an open procedure while providing excellent pain relief. We further describe limitations of the percutaneous approach when navigating close to large blood vessels, a situation more appropriately managed with open peripheral nerve stimulator placement. Ultrasound-guided placement may be considered for patients receiving peripheral nerve stimulators placed within the deep tissues, and not easily placed in a blind fashion.

Ultrasound-guided interventional procedures in pain medicine: a review of anatomy, sonoanatomy, and procedures. Part II: axial structures

There is a growing trend in using ultrasonography in pain medicine as evident by the plethora of published reports. Ultrasound(US) provides direct visualization of various soft tissues and real-time needle advancement and avoids exposing both the health care provider and the patient to the risks of radiation. The US machine is more affordable and transferrable than fluoroscopy, computed tomography scan,or magnetic resonance imaging machine. In a previous review, we discussed the challenges and limitations of US, anatomy, sonoanatomy, and techniques of interventional procedures of peripheral structures. In the present review, we discuss the anatomy, sonoanatomy, and US-guided techniques of interventional pain procedures for axial structures and review the pertinent literature.

Medical imaging in the diagnosis and management of cancer pain

Within the past few decades medical imaging has evolved very rapidly, now becoming an indispensable tool for the diagnosis, treatment, and follow-up of patients with cancer-related pain. Multiple imaging modalities are available for the assessment of cancer patients, each one with different advantages and limitations that are important to consider at the time we order a diagnostic study or plan an image-guided procedure. This article reviews the role that various imaging modalities play in the management of cancer pain and provides an overview of the latest technological advances.

Development and validation of a new technique for ultrasound-guided stellate ganglion block

BACKGROUND AND OBJECTIVES

Although the stellate ganglion is located anteriorly to the first rib, anesthetic block is routinely performed at the C6 level. Ultrasonography allegedly improves accuracy of needle placement and spread of injectate. The technique is relatively new, and the optimal approach has not been determined. Moreover, the location of the cervical sympathetic trunk relative to the prevertebral fascia is debatable.

METHODS

Three-dimensional sonography was performed on 10 healthy volunteers, and image reconstruction was completed. On the basis of analysis of pertinent anatomy, a lateral trajectory for needle placement was simulated. Accuracy was tested by injection of methylene blue in cadavers. A clinical validation study was then conducted. A block needle was inserted according to the predetermined lateral path, and 5 mL of a mixture of bupivacaine and iohexol was injected. Spread of the contrast agent was verified fluoroscopically.

RESULTS

Image reconstruction revealed that the cervical sympathetic trunk is located posterolaterally to the prevertebral fascia on the surface of the longus colli muscle. The mean anteroposterior width of the muscle at the C6 level was 11 mm. The lateral approach does not interfere with any visceral or nerve structures. Anatomic dissection in cadavers confirmed entirely subfascial spread of the dye and staining of the sympathetic trunk. The contrast agent spread was seen in all patients between the C4 and T1 levels in a typical prevertebral pattern.

CONCLUSIONS

This study revealed that, at the C6 level, the cervical sympathetic trunk lies entirely subfascially. Subfascial injection via the lateral approach ensures reliable spread of a solution to the stellate ganglion.