Objective: The incidence of chronic neuropathic pain following neck dissections is approximately 40%. Standard drug therapy in these patients include pharmacologic treatments due to the neuropathic pain (gabapentinoids, tricyclic antidepressants…). In this case, standard options were limited. The addition of ultrasound guidance to invasive pain management techniques has enabled us to successfully treat pathologies in which previous treatments options had been limited. Pulsed radiofrequency (PRF) ablation permits treatment over nerve structures that, due to either their morphological or functional characteristics, could not be approached using the conventional variant. Case report: A 45-year-old man with severe postoperative pain after undergoing partial glossectomy and functional neck dissection for squamous cell carcinoma of the tongue. The patient had been treated pharmacologically for several years with minimal results, baseline VAS of 90. After a successful superficial cervical plexus block under ultrasound guidance, he underwent PRF for a possible long-lasting effect. VAS post PRF improved in subsequent visits: VAS at 1 month was 0; at 3 months was 10 and at 6 months was 60. Conclusion: Postoperative changes to include alterations in nerve structures are a frequent source of chronic pain. The incidence of this type of pain in the cervical region is quite variable. Noninvasive treatment options are limited and oftentimes ineffective. Due to its location, superficial cervical plexus is an anatomical site with the potential risk of undergoing structural alterations (fibrosis, radiotherapy-associated retraction phenomena or neuroma formation). Interventional treatments performed under ultrasound guidance allow the dynamic application of therapies such as radiofrequency ablation. PRF could potentially cause an additive effect between neuromodulation and the hydrodissection caused by the infiltration of substances within a fibrotic area.

Background: Epidural steroid injection (ESI) is a common practice for pain treatment since 1953. In 2014, the FDA issued a warning about ESI. Studies have focused on the effect of the particle size and their ability to generate harmful aggregates. Although steroid aggregates provide longer times for reabsorption, therefore a longer anti-inflammatory effect, they are potentially harmful to the central nervous system via embolic mechanisms. Previous studies have established that steroidal aggregates with asizes over 100 μm are potentially able to occlude blood vessels. Studies by Tiso et al and Benzon et al addressed the role of steroids on CNS adverse events, with similar outcomes. The main difference was on the role of aggregates with a size over 100 μm, which Benzon et al. attributed to the ability of certain steroid preparations to rapidly precipitate and form large aggregates. Objectives: Studying the effect of the time elapsed between mixing the steroid preparation and injection on the number and size of aggregates with sizes above 100 μm. Study Design: Original study in basic science. Setting: Basic science Methods: Steroids evaluated are commonly used in Spain for ESI: betamethasone, triamcinolone, and dexamethasone. The size and number of the aggregates was determined for undiluted commercial steroid preparations in the usual amount for a single and double dosage used for ESI. Samples were examined with a Leica TCS-SP2 microscope at the first, the fifth and the 30th minute after shaking the preparations. Aggregates observed in the different preparations were manually counted and grouped in the following size range: 0-20, 20-50, 50-100, 100-300, 300-500 and > 500 μm. Statistical analysis was carried out using the R software. Nonparametric techniques were used in the comparison of aggregate size. Global comparison of the groups using the Kruskal-Wallis test and post-hoc comparisons using the Wilcoxon test, adjusting P-values by the Holm method for multiple comparisons Results: Aggregates present in triamcinolone and betamethasone samples were statistically larger than in dexamethasone samples. Triamcinolone suspensions produced significantly larger aggregates than betamethasone five minutes after mixing. Triamcinolone preparations produced greater particle aggregates (> 500 μm), which were not present in dexamethasone and betamethasone preparations. Limitations: Study how the human internal factors like blood elements and spinal fluid could interact with steroids and influence the size of the aggregates formed. Conclusions: This study demonstrates that the size of the particles injected depends on the type of steroid and the time allowed between mixing and injecting. The results demonstrate that waiting longer than 5 minutes between mixing and injecting can predispose the formation of potentially harmful aggregates in triamcinolone and betamethasone samples. The presence of greater particle aggregates (> 500 μm) may occlude some important vessels and arteries with serious adverse results. Vigorous shaking of the injectable could prevent such events. Key words. Epidural steroid injection. Triamcinolone. Betamethasone. Dexamethasone. Steroid aggregates.