A simple sonographic approach to thoracic transforaminal epidural injections for zoster-associated pain involving multiple nerves: an exploratory prospective cohort study
Article information
Abstract
Background
A simple superoposterior approach to thoracic transforaminal epidural injections (TFEIs) under ultrasonographic guidance was proposed to reduce zoster-associated pain (ZAP) involving multiple thoracic nerves and the likelihood of transitioning to postherpetic neuralgia (PHN).
Methods
Patients were prospectively enrolled. Primary endpoints were the burden of illness (BOI) scores and epidural contrast spread. Secondary endpoints included number of needle insertion attempts, sensory blockade, hemodynamic changes, procedure time, radiation dose, adverse events, rescue analgesics, PHN incidence and EuroQoL 5-Dimension scores.
Results
Thirty-five injections were performed in 27 patients. Median levels of cephalad-caudad epidural contrast spread were 3, 4, and 5 ml following injections of 2, 3, and 4 ml. Dorsal epidural spread was observed at levels 3, 4, and 5, whereas concurrent ventral spread was observed at levels 2, 3, and 4. BOI scores at 30–180 days significantly decreased (mean difference: −25.3, 95% CI [−57.4 to 6.6], P = 0.005), accounting for reduced rescue analgesic requirements and PHN occurrence and improved EuroQoL 5-Dimension scores. Median sensory blockade at 5 min post-procedure was at level 2, 3, and 4 after 2, 3, and 4 ml of therapeutic injectate. No significant hemodynamic changes were noted at 15 min post-injection. No serious adverse events were observed.
Conclusions
Spread of thoracic epidural contrast to all involved nerves was confirmed using this novel technique. Simplified needle placement reduced the technical difficulty and risk of complications. It might be a promising alternative approach for ZAP.
Introduction
Thoracic herpes zoster (HZ) originates from the reactivation of latent varicella zoster viruses in the dorsal root ganglion and spreads along the thoracic spinal nerves to their innervated dermatomes [1]. Zoster-associated pain (ZAP) and its catastrophic complication of postherpetic neuralgia (PHN) can severely debilitate physical function, psychological status, and quality of life, resulting in a heavy disease burden with increased hospitalization expenses according to real-world studies conducted on the Chinese population in Beijing [2,3]. The Neuropathic Pain Special Interest Group suggests reserving epidural blockades for patients in whom oral antivirals and analgesics fail [4]. Recently, a target-specific transforaminal (TF) approach that allows for delivery of drugs directly into the involved spinal nerve roots important for ZAP relief within 12 weeks of HZ onset has been advocated [5].
American Society of Interventional Pain Physicians (ASIPP) Comprehensive Evidence-Based Guidelines have recommended applying thoracic epidural injections using the TF approach (TFEIs) under fluoroscopy (FL) with real-time contrast injection. However, the prolonged procedure time and high radiation exposure associated with this approach discourages its use [6]. Ultrasonography (US) has the advantages of portability, real-time needle tracking, radiation-free visualization of the underlying pleura, and cost-effectiveness without hospitalization [7]. Although the scope for visualizing neuraxial structures in the thoracic spine is limited, a transverse US can provide a reliable acoustic window of the dorsal surface of the thoracic vertebrae [8].
Therefore, we describe a simple US-assisted method to identify the bony framework of the “armpit” of the thoracic lamina, which is used as a conduit into the foramen to guide needle placement in the key ultrasonographic view. We hypothesized that the proposed method would facilitate thoracic TFEI performance and reduce the risk of complications. Presuming that this would be associated with the spread of contrast to all involved nerve roots in the epidural space (ES) with a single injection, we subsequently estimated the pain relief effect and its potential as a prophylactic for PHN.
Materials and Methods
Ethical approval was granted by the Institutional Ethics Examination Committee of Human Research at the Women’s Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital (approval number: 2024KY-010) and was carried out in accordance with the 2024 revision of Declaration of Helsinki and the Strengthening the Reporting of Observational Studies in Epidemiology standardized reporting guidelines [9]. This study was prospectively registered on February 2, 2024, in the Chinese Registry of Clinical Trials (registration number: ChiCTR2400080761). All the participants provided written informed consent.
Study design
This prospective cohort study introduces a simple superoposterior approach for thoracic TFEIs under US guidance. Enrollment occurred between February 12 and March 31, 2024 (Fig. 1). The primary endpoints were the HZ-related burden of illness (HZ-BOI) over 30 days and the different patterns of epidural contrast flow determined by the final position of the needle tip and the volume of the injectates. The secondary endpoints included the number of needle insertion attempts into the foramen, radiation dose, procedure time, sensory blockade, mean arterial pressure, heart rate, adverse events such as inadvertent neuraxial injury, hematoma or blood flow disruption caused by mechanical trauma or embolic events, and intravascular injection, HZ-BOI from day 90 to 180, PHN incidence, health-related quality of life (HR-QoL) scores, and rescue analgesic requirement over time. Baseline status was determined on the day of enrollment and follow-ups were performed on days 7 (D7), 14 (D14), 21 (D21), and 30 (D30) after enrollment at our pain clinic and on days 90 (D90) and 180 (D180) via telephone interviews by two specially trained nurses.
CONSORT flow diagram of the study. HZ: herpes zoster, US: ultrasound, TFEI: transforaminal epidural injection, CT: computerized tomography, D: day, MI: multiple imputation.
Patients
Consecutive patients who visited our pain clinic for the treatment of herpetic eruptions were identified (Fig. 1). The inclusion criteria were as follows: (1) clinically diagnosed thoracic HZ within 30 days of rash onset, (2) involvement of ≥ 2 dermatomes, (3) ZAP with a ‘worst pain’ score ≥ 4 on the Zoster Brief Pain Inventory (ZBPI) scale [10], (4) failed standard antivirals and analgesics, (5) aged ≥ 50 years, and (6) willingness to comply with the study protocol. We excluded patients who met any of the following criteria: immune dysfunction or need for immunosuppressive treatment, hepatic or renal dysfunction, coagulation disorders, allergy to contrast medium, systemic use of analgesics, and pregnant or lactating women.
Description of intervention
The patients received a single thoracic epidural injection using the novel TF approach with US assistance. Based on consensus from previous studies, the need for an additional injection was determined after a minimum 2-week interval if patients reported < 50% relief in worst pain scores on the ZBPI [11,12]. Nonsteroidal anti-inflammatory drugs (NSAIDs) (celecoxib [200 mg], starting at 200 mg per day and up to a maximum of 200 mg twice a day as needed for pain relief) and weak opioids (tramadol hydrochloride [100 mg], starting at 50–100 mg and increasing up to 200 mg twice per day on demand for rescue analgesia) were prescribed if patients reported mild and moderate pain, respectively, following the recommendations of the World Health Organization analgesic ladder [13].
Procedures
All procedures were performed by three of the four authors who had expertise in the area of minimally invasive interventions for neuropathic pain under US guidance.
Patients were placed in the prone position on a computerized tomography (CT) table with a monitor for blood pressure, electrocardiography, and pulse oximetry. A curvilinear low-frequency US transducer (2–5 MHz) was positioned 2–3 cm lateral to the midline at the level of the pathology. Transverse processes (TPs) were observed as hyperechoic and rounded bony structures on this sagittal scan, and the hyperechoic structure of the parietal pleura (PP) that moves with respiration was also observed between the two contiguous TPs (Fig. 2A). The transducer was transmitted along a short axis over the TP at the primary target level, which was defined as the segment with the most severe manifestation of skin lesions when multiple levels were involved. The clearly delineated TP casted a dark acoustic shadow that completely obscured the visibility of the thoracic paravertebral region on US and was lateral to the hyperechoic pleura that exhibited a typical “lung sliding sign” (Fig. 2B). The transducer was then glided slightly caudally until the US beam was not impeded by the TP, thoracic spinous process (SP), or lamina and the PP or rib appeared in the image with characteristic hyperechoic signals.
Steps of the novel approach for US-assisted thoracic TFEIs at the sixth thoracic level. (A) a curvilinear probe is placed to view TPs using a longitudinal scan, (B) the probe is turned 90° and placed over the TP at the targeted thoracic vertebrae for the transverse view, (C) the probe is advanced slightly in the caudal direction to visualize the “armpit” of the lamina, which is identified as a hyperechoic landmark, (D) the probe is titled at an approximately 10–15° angle to the transverse plane to match the path of the intercostal space without any bony barrier, and the safety line, composed of a clear hyperechoic curve of pleura or rib in the modified transverse scan, (E) the needle (white arrow tip) is inserted in plane to reach the outer edge of the lamina using real-time US guidance, and (F) the needle is partially withdrawn and re-advanced at a steeper trajectory angle until the tip (yellow arrow tip) is placed next to the “armpit” and advanced slightly at a fixed pre-determined distance of 2–3 mm. “A–D” represents sequential changes in the probe position during the procedure: A (initial position), B (first adjustment), C (second adjustment), and D (finial position). US: ultrasound, TFEI: transforaminal epidural injection, TP: transverse process, SP: spinous process, “T” marker: orientation marker of transducer.
The “armpit” of the lamina, which represents the junction of the lamina and TP, is faintly visualized as a clear hyperechoic line. In the authors’ experience, the contours of the articular processes together with the necks of ribs (NRs) would appear, if the transducer is moved too far in the caudal direction; this anatomical detail is one reason for block failure. Therefore, understanding the “armpit” of the lamina as a vital landmark to find the foramen is crucial (Fig. 2C). Generally, the adjacent ribs create an additional barrier, making US application challenging and often impossible. To optimize the acoustic orientation, the transducer was rotated upward at the upper-thoracic level (T1–T4) by an angle of approximately 10–15° to the transverse screen and downward at the mid- and lower-thoracic levels (T5–T9 and T10–T12, respectively). Consequently, it was easier to advance the needle into the foramen, as this slanted direction matched the path of the intercostal space and no bony obstruction was present. To ensure needle placement was safe and atraumatic, we used a hyperechoic curve on the parietal pleura at the T1–T4 and T10–T12 levels or the neck of the next rib from T5–T9 as a reference and avoided exceeding this line (Fig. 2D).
After evaluating the vulnerable blood vessels around the pathway using color Doppler, a 22-gauge needle was inserted in the plane of the US beam and advanced using real-time tracking. The needle was advanced in the direction of the foramen until the tip made contact with the lamina (Fig. 2E). Once located, the needle tip was withdrawn slightly, and re-advanced at a more acute angle to slip into the “armpit” of the superoposterior quadrant of the foramen by a pre-determined distance of 2–3 mm (Fig. 2F). Precise visualization of the needle tip, which was not allowed to exceed the 6 o’clock position of the thoracic vertebral pedicle, was verified using axial CT imaging. After negative aspiration, dilute contrast medium was injected at increments of 1 ml for every additional nerve involved, after which a CT scan of the thoracic spine was performed again to observe dispersion. Subsequently, drugs were mixed with normal saline to create a total volume of injectate according to the following formula: (lidocaine [2 mg/ml] + dexamethasone [1.5 mg/ml]) × 1 ml per level and administered at a speed of 0.1 ml/s using real-time US. Dermatomal blockade was assessed in the presence of hypoesthesia by applying an alcohol soaked cotton ball 5 min after injection.
Outcome variables
The contrast dispersion into the ES was analyzed by two radiologists using sagittal reconstruction CT images according to the following criteria (Fig. 3): (1) dorsal spread defined as contrast reaching the ligamentum flavum; (2) ventral spread defined as contrast reaching the posterior aspect of the longitudinal ligament or vertebral body (if 1/3 of the ventral ES was not filled, it was considered dorsal spread); and (3) contralateral spread defined as contrast exceeding the SP on the contralateral side. The extent of contrast spread from the needle tip in the cephalic-to-caudal direction was also recorded [14]. Sensory blockade of dermatomes was defined as the loss of cold-warm discrimination, tested using a cooled alcohol-based cotton ball. The procedure duration was defined from the time landmarks were established with the US transducer to the completion of the injection. The radiation dose was collected from the report generated by the CT unit over the entire procedure in the form of a dose-area-product.
CT-confirmed contrast spread into the thoracic ES. (A) The precise placement of the needle tip is verified via axial CT, (B) contrast is shown filling the ventral ES exceeding the inner margin of the corresponding pedicle, (C) contrast is shown filling the dorsal ES in the cephalic-to-caudal direction along the ligamentum flavum, (D) contrast is shown filling the contralateral side exceeding the spinal process. The white arrow shows the needle insertion point. CT: computerized tomography, ES: epidural space, A: anterior.
ZAP was rated on a 11-point Likert scale ranging from 0 (no pain) to 10 (worst imaginable pain), and the “worst pain scores in the last 24 h” item of the ZBPI [10]. The total BOI imposed by HZ was assessed by quantifying the severity of HZ-specific pain over time using the area under the curve (AUC). The curve was created by connecting a series of XY points, taking the worst pain on the ZBPI as the Y-axis and the number of days with ZAP as the X-axis. Simply drawing a straight line between every set of adjacent points resulted in a trapezoid shape, the area of which was converted into the area of a rectangle using the formula of ΔX × (Y1 + Y2)/2. The trapezoidal rule was repeated for each adjacent pair of points to estimate the total AUC [15]. PHN was defined as a ‘worst pain’ score ≥ 3 on the ZBPI that persisted for at least 90 days after onset of HZ rash [16]. The HR-QoL was assessed using the 5L version of the EuroQoL 5-Dimensional questionnaire (EQ-5D-5L). This questionnaire evaluates the following five dimensions of health: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, each on a 5-level scale of difficulty as follows: none, slight, some, severe, and extreme [17]. Safety was evaluated according to the incidence of adverse events.
Sample size calculation
The PASS software version 16 (NCDS, LLC) was used to calculate the sample size. We aimed to test whether the mean response level (HZ-BOI-30AUC) to TFEIs using the novel approach was significantly different from that of conventional thoracic paravertebral blocks. We hypothesized the mean at 90 based on previous studies reporting a mean BOI-30AUC of 90 after repeated US-guided paravertebral injections, and the true mean BOI-30AUC was 75 with a standard deviation (SD) ranging from 10 to 20 by 1 if patients completed the TFEIs [18,19]. Considering a power of 90% with a 2-tailed α of 5% at various sample sizes from 5 to 40, and allowing for a 20% loss to follow-up, the sample size calculation was 27 cases.
Statistical analysis
SPSS software (version 22.0; SPSS Inc.) was used for the statistical analyses. Statistical significance was set at a significance level of 5%. The Kolmogorov-Smirnov Z test was used for normality testing. Normal or skewed quantitative data are described as the mean ± SD or median (Q1, Q3). Categorical data are reported as frequencies and percentages. Repeated-measures analysis was employed for changes in quantitative data over time, with the baseline values used as covariates. Post-hoc comparisons were performed using Bonferroni Correction. The Fisher’s exact test was used to analyze categorical variables. Missing values lost to follow-up were assumed to be missing at random for any reason and processed by means of a multiple imputation method using chained equations. Sensitivity analyses were performed to test robustness.
Results
The Consolidated Standards of Reporting Trails (CONSORT) flowchart of this study is shown in Fig. 1. The patient demographic details and clinical characteristics are shown in Table 1.
Demographic and Clinical Characteristics of Study Patients at Baseline
A total of 35 TFEIs were performed in 27 patients. The ZBPI scores decreased significantly at all time intervals from D7 (2 [0, 4] [range: 0–6]) to D180 (0 [0, 0] [range: 0–5]). As a result, the mean HZ-BOI-30AUC, BOI-30–90AUC, and BOI-90–180AUC showed a significant decline in the BOI associated with ZAP over time after adjusting for the baseline scores as covariates (Table 2). Sensitivity analysis, which was performed to account for the missing outcomes shown in Fig. 1, yielded results consistent with the primary findings (mean HZ-BOI score: 43.6 ± 39.1 and 36.5 ± 25.2 at the 90- and 180-day assessment). The prevalence of PHN decreased across all time points during the follow-up.
HZ-related BOI using AUC and PHN Occurrence on Days 0–30, 30–90, and 90–180
The median number of needle insertion attempts and mean procedure time and radiation dose are shown in Table 3. The median levels of cephalad-caudad epidural contrast spread were 3, 4, and 5 ml following injections of 2, 3, and 4 ml, respectively. Dorsal epidural spread was observed at levels 3, 4, and 5, whereas concurrent ventral spread was observed at levels 2, 3, and 4. However, separate spread of the epidural contrast agent was not observed. The width of bilateral epidural contrast spread increased with the incremental increases in injected volume. Median sensory blockade at 5 min post-procedure was at level 2, 3, and 4 after 2, 3, and 4 ml of therapeutic injectate. Therefore, the total level of spread in the cephalad-caudal direction was wider than that in the postprocedural anesthetized dermatomes (Fig. 4). No significant hemodynamic changes were noted 15 min after injection.
Outcomes of Thoracic TFEIs using Novel Approach and Patterns of Contrast Spread into ES
Sensory blockades after TFEIs. (A) The frequency of each thoracic dermatome involved at baseline and the frequency of the sensory blockade at each thoracic dermatome observed 5 min post-procedure in patients receiving US-assisted thoracic TFEIs using the novel approach. (B) The number of anesthetized dermatomes receiving different volumes of therapeutic injectate at 5 min post-procedure. TFEI: transforaminal epidural injection, US: ultrasound, T: thoracic spine level.
The proportion of patients requiring rescue analgesics decreased, though to variable degrees, during the follow-up period and was significantly lower than at baseline. A similar trend was also observed for the rescue medication dosages (Fig. 5).
Rescue analgesic requirement, including celecoxib and tramadol hydrochloride in patients with inadequate pain relief during the follow-up period. The bar graph represents the percentage of patients using rescue analgesia, and the line graph indicates the mean analgesic dosage. *Given that receiving two rescue analgesics could influence the results, a significant difference using Bonferroni correction with an adjusted alpha value of 0.05 / 6 = 0.0083 was made to account for the comparison across 2 drugs × 3 time points. D: days.
Fig. 6 shows a significant improvement in the proportion of patients reporting difficulty with mobility, self-care, usual activities, pain/discomfort, and symptoms of anxiety/depression according to the EQ-5D-5L scores (all P < 0.001).
The proportion of patients reporting difficulties in the five domains of the EQ-5D-5L at baseline and across all time points during follow-up period. *A significant difference compared to baseline using Bonferroni correction with an adjusted alpha value of 0.05 / 3 = 0.0167. EQ-5D-5L: 5L version of the Euro-QoL 5-Dimensional questionnaire, D: days.
No serious adverse events occurred following any of the 35 injections. Dizziness was observed within 10 min of injection in four (11.4%) cases, and pain at the entry point was reported in five (14.3%) cases. None of the patients withdrew from the study due to adverse events.
Discussion
The two main findings of this study were as follows: our novel approach facilitated needle placement during TF-entry procedures and the risk of complications was reduced by targeting the superoposterior quadrant of the foramen with a safety hyperechoic-curved-line.
The thoracic intervertebral foramen is unique due to its complex boundaries. The TPs are articulated with the tubercles of their respective ribs to form costotransverse articulations, and the NRs lie anterior to the TPs, both of which cause narrowing of the acoustic windows. Additionally, the zygapophysial joints, together with the progressively projected NR of the next rib, impede access to most joint entrances [20]. Owing to these limitations, US of the thoracic foramen can only be reliability visualized if “acoustic windows” are created and used properly. Based on our clinical experience, this novel approach was technically simple when the needle was inserted targeting the “armpit” of the lamina and the US visibility of the puncture-path was refined to overcome the bony obstructions limiting needle probing.
Although a few reports of nerve blocks with the same purpose and method as ours are available, previous studies have reported a considerable number of required needle punctures (7.2 to 14.4 times) when introducing the needle to the foramen via the TF approach with the assistance of FL, as well as longer needling or procedure times (518 ± 103 s with US guidance vs. 929 ± 228 s with FL guidance; P < 0.05) [21,22]. Our data showed a reduced median number of needle redirection attempts 2 (1, 3) and a reduction in the time required to perform the procedure using US guidance (14.96 ± 1.99 min), indicating that this novel technique enables clinicians to locate the corresponding foramen with ease. Significantly higher radiation exposure has been reported in the literature, at 8807.75 ± 1039.10 to 8992 ± 2132 µGy·m2 with FL-guided injection, while our findings showed a dose of 2047.20 ± 469.53 µGy·m2, presumably because CT screening was used for verification rather than guidance [22,23].
CT not only enabled confirmation of the precise position of the needle tip inside the foramen but also verification of the blockade levels with the assistance of contrast agents. In our study, the ranges of contrast spread, using the pedicle as a representative point, extended in either a cephalad-to-caudal or ventral-to-dorsal direction after a single injection, covering all involved levels. Hong et al. [24] reported similar findings in their study showing cephalad spread of contrast with lateral imaging using FL at a median of 2 levels (1, 2) for caess receiving 1 ml of contrast, 2.5 (2, 3) for 2 ml, and 3 (2, 4) for 3 ml, while the caudal spread level was 1 (1, 2), 2 (2, 3), and 2 (2, 3) for the 1-, 2- and 3-ml injections, respectively. Both ventral and dorsal spread were observed in 88% of patients after a 3-ml contrast injection, whereas bilateral epidural spread on anteroposterior images was reported in 85% of cases. A review of the literature showed that the extent of sensory blockade is usually less extensive than the spread of contrast medium by an average of one dermatome [25]. Accordingly, the levels of sensory blockade at 5 min post-injection were slightly wider than those of the involved thoracic dermatomes in all cases of different injection volumes in our study. However, this difference was not statistically significant. An appropriate range of neuraxial blockade within the thoracic area would block the desired area while avoiding the side effects of hypotension [26]. Thus, we did not observe any statistically significant change, such as a drop of more than 30% from baseline in the blood pressure or heart rate 5 min after injection.
A recent meta-analysis of randomized controlled trials (RCTs) found that the risk of inadvertent intravascular puncture during TFEIs is lower with US guidance compared to CT- or FL-guidance, with an incidence ranging from 1.8% to 8.6% (odds ratio: 0.21, 95% CI [0.07–0.64]) [27]. Additionally, dural puncture has been previously reported in 1.3% of 10 000 fluoroscopically directed thoracic epidural injections [28]. However, our results showed no severe adverse events, such as inadvertent neuraxial injury, intravascular injection, or pneumothorax, during or after the procedure. The proposed method, based on the ease of direct needle placement into the posterolateral aspect of the foramen rather than the anterosuperior quadrant of the thoracic foramen where radicular branches providing an anterior radiculomedullary artery are most likely encountered, could reduce the risk of inadvertent injection or injury during TFEIs [29]. Our findings might also be favorable due to the obtuse angle used for needle insertion above a hyperechoic safety curve instead of advancing the needle anteriorly with a steeper obliquity using the vertebral pedicle as a fluoroscopic landmark to the entrance of the foramen, resulting in fewer complications [30]. Therefore, this novel approach conferred by real-time US minimizes the relative disadvantages of conventional FL techniques and presents a possible strategy to prevent iatrogenic complications.
However, tracking the needle tip in the foramen using this approach was challenging as deeper foraminal structures were poorly visualized. Our experience is consistent with the technique described by Emami et al. [31], who placed the needle tip on the lateral edge of the lamina instead of advancing it directly into the foraminal area. In addition, we believe that the use of a reliable validation method, either FL or CT, should be emphasized to determine the accuracy of needle tip placement.
A TF approach allows for improved access to the sensory ganglion, which contains various receptor channels for pain signaling in HZ [32]. Previous findings have reported that administering epidural injections in the early phase of HZ significantly reduces visual analog scale pain scores at 1 week (39 mm [21, 60] vs. 49 mm [30, 66], P = 0.001) and 1 month (2 mm [0, 23] vs. 6 mm [0, 32], P = 0.02) after injection compared to standard treatment [11]. Consistent with this, our results showed a significant decrease in ZBPI scores over time and a reduction in the rescue analgesic requirement. Our HZ-BOI score over 30 days (62.54 ± 43.24) was lower than that for existing options of thoracic paravertebral blocks, which range from 82.7 (95% CI [75.4–90.1]) to 111.9 (95% CI [97.4–126.4]) [18,19]. Therefore, a significant improvement was observed in quality of life with respect to EQ-5D-5L scores. Although the available evidence on PHN incidence is inconsistent, our data was comparable, with an incidence of 6.3% and 2.1% at three and six months after FL-guided thoracic TFEIs, respectively [33].
This study has several limitations. First, it was often challenging to visualize the entire needle under the US beam, even when using the novel approach, which might be because the beam was insonated with a slight oblique tilt for optimal visibility and highly dependent on the provider’s experience. Second, although vessels could be seen with US-assistance, periforaminal arteries were extremely small, with a mean diameter of 1.25 ± 0.45 mm [34]. Third, considering the small number of trials, the evidence is limited in terms of PHN occurrence. Fourth, the outcomes from the initial and repeated injections were combined owing to the small sample size, which might have introduced confounding factors in the analysis, as patients who require additional injections might have more refractory pain or different underlying pathologies. Fifth, as the block needle was advanced in the direction of the foramen, a well-designed RCT is needed to determine the incidence of complications given that central neuraxial adverse events are common with a medially directed needle.
In conclusion, utilizing this novel approach to perform thoracic TFEIs with US assistance and CT validation resulted in contrast dispersion into the desired ES covering all involved nerves with a single injection. Simplified needle placement decreased technical difficulty and helped reduce the risk of complications. With the advantages associated with US-assistance, managing ZAP and preventing PHN may be promising with this approach.
Notes
Funding
The study was funded by the academic project from Capital Medical University affiliated Beijing Shijitan Hosptial (2022-q17).
Conflicts of Interest
No potential conflict of interest relevant to this author was reported.
Data Availability
The data and materials are available from the corresponding author upon reasonable request.
Author Contributions
Shuyue Zheng (Conceptualization; Formal analysis; Investigation; Methodology; Project administration; Visualization; Writing – original draft)
Dan Wang (Data curation; Formal analysis; Investigation; Software; Validation; Visualization)
Li Yue (Formal analysis; Investigation; Methodology; Software)
Liangliang He (Conceptualization; Data curation; Investigation; Project administration; Supervision; Writing – review & editing)