The High-Frequency Ultrasound Detection of Rat Sciatic Nerve in a Crushed Injury Model

Ultrasound-guided and 'blind' sciatic nerve injection techniques: Comparison in rat cadavers

OBJECTIVE

To compare the success rate and extent of sciatic nerve staining with a bupivacaine-dye solution using two injection techniques: 'blind' or ultrasound-guided approach.

STUDY DESIGN

Prospective, experimental, randomized, cadaveric study.

ANIMALS

Adult female Wistar rat cadavers [n = 24, mass 352 g (323-374)].

METHODS

Each sciatic nerve was randomly allocated to one of two groups: 'blind' (group B) or ultrasound-guided approach (group US) to injection. Following injection of bupivacaine-dye solution (0.1 mL), gross anatomical dissection was performed to visualize nerve staining, categorizing it as either positive or negative. The length of nerve staining was then measured and visual inspection conducted to identify potential nerve damage. Fisher's exact test was used to compare positive or negative nerve staining, and the Wilcoxon signed rank test used to compare the length of nerve staining between groups.

RESULTS

In group B, the bupivacaine-dye solution stained 16/24 sciatic nerves (67% success). In group US, staining was successfully observed in all 24 nerves (100% success, p < 0.004). The length of nerve staining [median (interquartile range)] was 2 (2-3) mm in group B and 5 (4-6) mm in group US (p < 0.001). One sciatic nerve in group B had injectate distributed over 16 mm, suggestive of an intraneural injection. No signs of laceration or nerve damage were visible under 6× magnification in either group.

CONCLUSIONS AND CLINICAL RELEVANCE

The ultrasound-guided approach for sciatic nerve injection demonstrated a higher success rate with superior injectate distribution when compared with the 'blind' approach. Ultrasound guidance is recommended over a 'blind' approach for sciatic nerve block in rats when possible.

Quantitative evaluation of rat sciatic nerve degeneration using high-frequency ultrasound

In this study, we evaluated the utility of using high-frequency ultrasound to non-invasively track the degenerative process in a rat model of peripheral nerve injury. Primary analyses explored spatial and temporal changes in quantitative backscatter coefficient (BSC) spectrum-based outcomes and B-mode textural outcomes, using gray level co-occurrence matrices (GLCMs), during the progressive transition from acute to chronic injury. As secondary analyses, correlations among GLCM and BSC spectrum-based parameters were evaluated, and immunohistochemistry were used to suggest a structural basis for ultrasound outcomes. Both mean BSC spectrum-based and mean GLCM-based measures exhibited significant spatial differences across presurgical and 1-month/2-month time points, distal stumps enclosed proximity to the injury site being particularly affected. The two sets of parameters sensitively detected peripheral nerve degeneration at 1-month and 2-month post-injury, with area under the receiver operating charactersitic curve > 0.8 for most parameters. The results also indicated that the many BSC spectrum-based and GLCM-based parameters significantly correlate with each other, and suggested a common structural basis for a diverse set of quantitative ultrasound parameters. The findings of this study suggest that BSC spectrum-based and GLCM-based analysis are promising non-invasive techniques for diagnosing peripheral nerve degeneration.

Ultrasonic visualization technique for anatomical and functional analyses of the sciatic nerve in rats

Background and objective

Ultrasound has been widely used in the diagnosis and minimally invasive treatment of peripheral nerve diseases in the clinic, but there is still a lack of feasibility analysis in rodent models of neurological disease. The purpose of this study was to investigate the changes in the cross-sectional area of the sciatic nerve of different genders and body weights and to explore the effectiveness and reliability of an ultrasound-guided block around the sciatic nerve in living rats.

Methods

Using ultrasound imaging anatomy of the sciatic nerve of rats, the cross-sectional area of the sciatic nerve in rats of different genders from 6 to 10 weeks old was calculated, and then analyzed its correlation with body weight. Further analyses were conducted through behavioral and cadaveric studies to evaluate the feasibility of ultrasound-guided perineural injection of the sciatic nerve in rats.

Results

We first reported that the sciatic nerve cross-sectional area of rats was increased with age (F = 89.169, P < 0.001), males had a higher sciatic nerve cross-sectional area than females (F = 60.770, P < 0.001), and there was a positive correlation with body weight (r_Male = 0.8976, P < 0.001; r_Female = 0.7733, P < 0.001). Behavioral observation of rats showed that the lower extremity complete block rate was 80% following the administration of drugs around the sciatic nerve under ultrasound guidance and staining with methylene blue occurred in all sciatic nerves and surrounding muscles and fascia using 20 ultrasound-guided injections.

Conclusions

Ultrasound visualization technology can be used as a new auxiliary evaluation and intervention therapy for animal models of peripheral nerve injury, and will provide overwhelming new references for the basic research of neurological diseases.

In Vivo Whole-Nerve Electrophysiology Setup, Action Potential Recording, and Data Analyses in a Rodent Model

In vivo rodent, whole peripheral nerve models are useful for studying the electrical conduction of sensory and motor fibers under normal physiological conditions as well as for assessing neurological outcomes after the application of physical alterations or pharmacological agents to the nervous system. Significant literature has focused on single-neuron and central nervous system electrophysiology protocol development. However, creation and development of in vivo whole-nerve electrophysiological recording protocols are sparse in the scientific literature. Here, detailed protocols for designing and building an in vivo whole-nerve electrophysiology system are described, including straightforward techniques to create working stimulation and recording electrodes that may be adapted to numerous study designs. Further, we include details for rodent anesthesia, surgical dissection (for the sciatic nerve), compound action potential signal optimization, data acquisition, data analyses, and troubleshooting tips. © 2021 Wiley Periodicals LLC. Basic Protocol 1: In vivo electrophysiology system wiring, hardware, and software setups Support Protocol 1: Design and 3D printing of electrophysiology base electrodes Support Protocol 2: Building needle electrodes Basic Protocol 2: Rodent anesthesia and surgery for nerve exposure Basic Protocol 3: Compound action potential recording and troubleshooting using WinWCP Basic Protocol 4: Compound action potential data analysis using WinWCP.

Refining the rat sciatic nerve block: a novel ultrasound-guided technique

Murine translational models are an important tool to understand pain pathophysiology. One procedure used frequently in murine research is the sciatic nerve block. This study sought to demonstrate the use of ultrasound-guided sciatic nerve block in a cadaveric murine model. A total of 40 injections were performed in 20 Sprague-Dawley male 18-month-old rat cadavers. Necropsy was performed to identify staining of the sciatic nerve. Staining with methylene blue occurred in 40 of 40 ultrasound-guided injections. The extremely accurate nature of this block under ultrasound guidance is favorable for future translational studies in rats undergoing sciatic nerve blocks. This method may represent a significant improvement in current methods.