Ultrasonography-Guided Radiofrequency Ablation for Painful Stump Neuromas to Relieve Postamputation Pain: A Pilot Study

Sciatic-nerve radiofrequency ablation for phantom limb pain: A case report

Phantom and residual limb pain are commonly experienced by the majority of amputees, and are often difficult to treat not adequately relieved with medical treatment alone. While extensively studied, the pathophysiology of refractory pain is still unclear, with many proposed mechanisms under investigation (Wilkes et al., 2008). Limited existing literature suggests percutaneous interventions including radiofrequency ablation (RFA) may be promising treatment modalities for patients who have pain refractory to oral agents (Sperry et al., 2023). We present a patient with persistent phantom limb and cancer-associated acetabular pain following hip disarticulation who underwent sciatic-notch RFA for pain management.

In vitro culture of muscle cells derived from myofascial trigger points

OBJECTIVE

To examine for the in vitro existence of contractile nodules on the taut band of muscle fibers where myofascial trigger points (MTrPs) are located (using cell culture).

METHODS

Sixteen male Sprague-Dawley rats (7 weeks old) were randomly divided into experimental and control groups. A blunt striking injury and eccentric exercise were applied to the gastrocnemius muscle of rats in the experimental group once a week for 8 weeks to establish an MTrP model. Subsequently, the rats were reared normally and rested for 4 weeks. After modeling, the skeletal muscles at the MTrPs (and non-MTrPs at the same anatomical position) were extracted from the two groups of rats for in vitro cell culture experiments of single muscle fibers. Potential contractile nodules in the MTrP group were exposed to different concentrations of acetylcholinesterase, whereas non-MTrP cells were exposed to acetylcholine. The morphological changes of muscle cells in each group were observed.

RESULTS

By culturing MTrP cells in vitro, large contractile nodules remained in single MTrP muscle fibers, whereas some contractile nodules were twisted and deformed. After the addition of different acetylcholinesterase concentrations, no obvious morphological changes were observed in the contractile nodules in the MTrP group. After the non-MTrP cells were exposed to different acetylcholine concentrations, no significant morphological changes were observed in the single muscle fibers.

CONCLUSION

MTrP cells can continue to maintain contractile morphology in vitro, but whether the recovery of such contractile nodules is related to acetylcholine remains uncertain.

Feasibility of Magnetic Resonance-Guided High-Intensity-Focused Ultrasound (MRgHIFU) Ablation of Stump Neuromas for the Relief of Chronic Postamputation Neuropathic Pain

Up to 70% of limb amputees develop chronic postamputation neuropathic pain (CPANP) which includes phantom pain and residual limb neuropathic pain due to neuroma formation. CPANP often requires invasive procedures aimed at neuroma ablation. Five amputees received 6 noninvasive magnetic resonance-guided high-intensity-focused ultrasound MRgHIFU treatments ExAblate®, Insightec, Tirat-Carmel, Israel). Although ablative temperature (>65°C) at the neuroma was reached in only 1 patient, pain intensity dropped from 5.7 at baseline to 4.3 and back to 5.6 at 3 and 6 month follow-up. Post-treatment bone necrosis was demonstrated in 1 patient. Although no firm conclusion about the effectiveness of MRgHIFU for CPANP could be drawn, further studies are warranted.

Mechanosensitive Ion Channel TMEM63A Gangs Up with Local Macrophages to Modulate Chronic Post-amputation Pain

Post-amputation pain causes great suffering to amputees, but still no effective drugs are available due to its elusive mechanisms. Our previous clinical studies found that surgical removal or radiofrequency treatment of the neuroma at the axotomized nerve stump effectively relieves the phantom pain afflicting patients after amputation. This indicated an essential role of the residual nerve stump in the formation of chronic post-amputation pain (CPAP). However, the molecular mechanism by which the residual nerve stump or neuroma is involved and regulates CPAP is still a mystery. In this study, we found that nociceptors expressed the mechanosensitive ion channel TMEM63A and macrophages infiltrated into the dorsal root ganglion (DRG) neurons worked synergistically to promote CPAP. Histology and qRT-PCR showed that TMEM63A was mainly expressed in mechanical pain-producing non-peptidergic nociceptors in the DRG, and the expression of TMEM63A increased significantly both in the neuroma from amputated patients and the DRG in a mouse model of tibial nerve transfer (TNT). Behavioral tests showed that the mechanical, heat, and cold sensitivity were not affected in the Tmem63a^-/- mice in the naïve state, suggesting the basal pain was not affected. In the inflammatory and post-amputation state, the mechanical allodynia but not the heat hyperalgesia or cold allodynia was significantly decreased in Tmem63a^-/- mice. Further study showed that there was severe neuronal injury and macrophage infiltration in the DRG, tibial nerve, residual stump, and the neuroma-like structure of the TNT mouse model, Consistent with this, expression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β all increased dramatically in the DRG. Interestingly, the deletion of Tmem63a significantly reduced the macrophage infiltration in the DRG but not in the tibial nerve stump. Furthermore, the ablation of macrophages significantly reduced both the expression of Tmem63a and the mechanical allodynia in the TNT mouse model, indicating an interaction between nociceptors and macrophages, and that these two factors gang up together to regulate the formation of CPAP. This provides a new insight into the mechanisms underlying CPAP and potential drug targets its treatment.

Real-time ultrasound-guided stellate ganglion block for migraine: an observational study

Objective

To observe whether ultrasound-guided stellate ganglion block (SGB) can effectively relieve migraine pain and improve the quality of migraine patients’ life.

Methods

81 patients with migraines were enrolled in this study. The patients received SGB with 6 ml of 0.15% ropivacaine once every week for four times. Migraine was assessed with the Migraine Disability Assessment Scale (MIDAS) at baseline and three-months follow-up (Tm). The numerical rating scale (NRS) score at baseline, one day after treatment (Td) and Tm, the frequency of analgesic use in 3 months and the side effects were also recorded at the same time.

Results

The NRS score of migraine subjects decreased significantly from 7.0 (2.0) to 3.0 (1.0) at Td and 2.0 (2.0) at Tm (vs baseline, P < 0.01). The MIDAS total scores were 14.0 (10.5) at baseline and 7.0 (4.5) at Tm (P < 0.001). During the three months, the frequency of analgesic consumption was decreased from 6.2 ± 2.8 to 1.9 ± 1.8. There were no serious side effects.

Conclusions

This study confirmed that ultrasound-guided SGB is an effective method to treat migraines. This technique can reduce pain and disability and then improve the quality of life of patients with migraines.

Peripheral Nerve Focused Ultrasound Lesioning-Visualization and Assessment Using Diffusion Weighted Imaging

Objectives: Magnetic resonance-guided focused ultrasound (MRgFUS) is a non-invasive targeted tissue ablation technique that can be applied to the nervous system. Diffusion weighted imaging (DWI) can visualize and evaluate nervous system microstructure. Tractography algorithms can reconstruct fiber bundles which can be used for treatment navigation and diffusion tensor imaging (DTI) metrics permit the quantitative assessment of nerve microstructure in vivo. There is a need for imaging tools to aid in the visualization and quantitative assessment of treatment-related nerve changes in MRgFUS. We present a method of peripheral nerve tract reconstruction and use DTI metrics to evaluate the MRgFUS treatment effect. Materials and Methods: MRgFUS was applied bilaterally to the sciatic nerves in 6 piglets (12 nerves total). T1-weighted and diffusion images were acquired before and after treatment. Tensor-based and constrained spherical deconvolution (CSD) tractography algorithms were used to reconstruct the nerves. DTI metrics of fractional anisotropy (FA), and mean (MD), axial (AD), and radial diffusivities (RD) were measured to assess acute (<1-2 h) treatment effects. Temperature was measured in vivo via MR thermometry. Histological data was collected for lesion assessment. Results: The sciatic nerves were successfully reconstructed in all subjects. Tract disruption was observed after treatment using both CSD and tensor models. DTI metrics in the targeted nerve segments showed significantly decreased FA and increased MD, AD, and RD. Transducer output power was positively correlated with lesion volume and temperature and negatively correlated with MD, AD, and RD. No correlations were observed between FA and other measured parameters. Conclusions: DWI and tractography are effective tools for visualizing peripheral nerve segments for targeting in non-invasive surgical methods and for assessing the microstructural changes that occur following MRgFUS treatment.