Can neural blocks prevent phantom limb pain?

Thalamus: The 'promoter' of endogenous modulation of pain and potential therapeutic target in pathological pain

More recently, the thalamic mediodorsal (MD) and ventromedial (VM) nuclei have been revealed to be functioned as 'nociceptive discriminator' in discriminating noxious and innocuous peripheral afferents, and exhibits distinct different descending controls of nociception. Of particularly importance, the function of thalamic nuclei in engaging descending modulation of nociception is 'silent' or inactive during the physiological state as well as in condition exposed to insufficient noxious stimulation. Once initiation by sufficient noxious or innocuous C-afferents associated with temporal and spatial summation, the thalamic MD and VM nuclei exhibit salient, different effects: facilitation and inhibition, on noxious mechanically and heat evoked nociception, respectively. Based on series of experimental evidence, we here summarize a novel hypothesis involving thalamic MD and VM nuclei functioned as 'promoter' in initiating descending facilitation and inhibition of pain with specific spatiotemporal characteristics. We further hypothesize that clinical remedy in targeting thalamic VM nucleus by enhancing its activities in recruiting inhibition alone or decreasing thalamic MD nucleus induced facilitation may provide promising way in effectively control of pathological pain.

OUP accepted manuscript

Among the work-related injuries, meat grinder injuries are not uncommon. One of the major challenges in the trauma resuscitation room is the appropriate choice of anesthesia/analgesia when the patient is still conscious and the second challenge is to find the best way to early extract the patient’s limb out of the machine without adding more suffering. Herein, we presented a 23-year-old male patient who was brought fully conscious in a kneeling position with the right forearm entrapped in a big meat grinder machine with part of the crushed fingers being extruded out of the machine. The patient was in severe pain; however, his vital signs were stable. Analgo-sedation with Midazolam/Ketamine followed by ultrasound guided upper limb regional anesthesia was used and showed to be a fast and safe alternative in a conscious, not fasting patient when the extremity is still entrapped in a meat grinder machine.

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

Objective

Postamputation pain (PAP) is a serious problem, and thus far, there is no perfect treatment strategy. Clinically, minimally invasive treatments for peripheral neuromas are simple and feasible. This study aimed to investigate the immediate and long-term effects of ultrasonography-guided radiofrequency ablation (RFA) on PAP.

Methods

Eighteen PAP subjects with painful peripheral neuromas were treated with ultrasonography-guided RFA.

Results

A total of 18 PAP subjects were included in the final analyses. Fourteen of the 17 subjects with residual limb pain (RLP) (82.4%) had successful outcomes. A successful outcome was noted in 9 of the 13 subjects with phantom limb pain (PLP) (69.2%). There were no significant associations between symptom relief and sex, age, or the duration of symptoms. There were no severe complications.

Conclusions

Ultrasonography-guided RFA for painful stump neuromas can effectively relieve stump pain and PLP in amputees with PAP (follow-up time was 12 months). Ultrasonography-guided RFA is easy and safe and does not involve radiation exposure, making it very suitable for clinical applications.

[Perioperative measures for prevention of phantom pain: an evidence-based approach to risk reduction]

Prevention of phantom limb pain is one of the biggest and still largely unsolved challenges in perioperative medicine. Despite many study efforts and optimization of postoperative pain treatment over the last 30 years, a significant reduction in the incidence of phantom limb pain has not been achieved. Current studies have also shown that at least 50% of patients develop phantom pain after 6 months. A possible approach could be to combine multiple synergistic interventions and implement them as a perioperative phantom pain management strategy bundle. In addition to regional anesthesia, NMDA antagonists, gabapentinoids, antidepressants and systemic lidocaine could play a relevant role. The aim of this pharmacological intervention was the modification of the pathophysiological changes in peripheral nerves and in the central nervous system after amputation.

Peripheral input and phantom limb pain: A somatosensory event-related potential study

BACKGROUND

Following amputation, nearly all amputees report nonpainful phantom phenomena and many of them suffer from chronic phantom limb pain (PLP) and residual limb pain (RLP). The aetiology of PLP remains elusive and there is an ongoing debate on the role of peripheral and central mechanisms. Few studies have examined the entire somatosensory pathway from the truncated nerves to the cortex in amputees with PLP compared to those without PLP. The relationship among afferent input, somatosensory responses and the change in PLP remains unclear.

METHODS

Transcutaneous electrical nerve stimulation was applied on the truncated median nerve, the skin of the residual limb and the contralateral homologous nerve in 22 traumatic upper-limb amputees (12 with and 10 without PLP). Using somatosensory event-related potentials, the ascending volley was monitored from the brachial plexus, the spinal cord, the brainstem and the thalamus to the primary somatosensory cortex.

RESULTS

Peripheral input could evoke PLP in amputees with chronic PLP (7/12), but not in amputees without a history of PLP (0/10). The amplitudes of the somatosensory components were comparable between amputees with and without PLP. In addition, evoked potentials from the periphery through the spinal, subcortical and cortical segments were not significantly associated with PLP.

CONCLUSIONS

Peripheral input can modulate PLP but seems insufficient to cause PLP. These findings suggest the multifactorial complexity of PLP and different mechanisms for PLP and RLP.

SIGNIFICANCE

Peripheral afferent input plays a role in PLP and has been assumed to be sufficient to generate PLP. In this study we found no significant differences in the electrical potentials generated by peripheral stimulation from the truncated nerve and the skin of the residual limb in amputees with and without PLP. Peripheral input could enhance existing PLP but could not cause it. These findings indicate the multifactorial complexity of PLP and an important role of central processes in PLP.

Regional anesthesia for vascular surgery: does the anesthetic choice influence outcome?

PURPOSE OF REVIEW

Outcomes following surgery are of major importance to clinicians, institutions and most importantly patients. This review examines whether regional anesthesia and analgesia influence outcome after vascular surgery.

RECENT FINDINGS

Large database analyses of contemporary practice suggest that utilizing regional anesthesia for both open and endovascular aortic aneurysm repair, lower limb revascularization and carotid endarterectomy reduces morbidity, length of stay and possibly even mortality. Results from such analyses are limited by an inherent risk of bias but are nevertheless important given the number of patients required in randomized trials to detect differences in rare outcomes. There is minimal evidence that regional anesthesia influences longer term outcomes except for arteriovenous fistula surgery where brachial plexus blocks appear to improve 3-month fistula patency.

SUMMARY

Patients undergoing vascular surgery often have multiple comorbidities and it is important to be able to outline both benefits and risks of regional anesthesia techniques. Regional anesthesia in vascular surgery allows avoidance of general anesthesia and does provide short-term benefits beyond superior analgesia. Evidence of long-term benefits is lacking in most procedures. Further work is required on newer patient centered outcomes.

Coping with Phantom Limb Pain

Phantom limb pain is a chronic neuropathic pain that develops in 45-85% of patients who undergo major amputations of the upper and lower extremities and appears predominantly during two time frames following an amputation: the first month and later about 1 year. Although in most patients the frequency and intensity of pain diminish over time, severe pain persists in about 5-10%. It has been proposed that factors in both the peripheral and central nervous systems play major roles in triggering the development and maintenance of pain associated with extremity amputations. Chronic pain is physically and mentally debilitating, affecting an individual's capacity for self-care, but also diminishing an individual's daily capacity for personal and economic independence. In addition, the pain may lead to depression and feelings of hopelessness. A National Center for Biotechnology Information study found that in the USA alone, the annual cost of dealing with neuropathic pain is more than $600 billion, with an estimated 20 million people in the USA suffering from this condition. Although the pain can be reduced by antiepileptic drugs and analgesics, they are frequently ineffective or their side effects preclude their use. The optimal approach for eliminating neuropathic pain and improving individuals' quality of life is the development of novel techniques that permanently prevent the development and maintenance of neuropathic pain, or that eliminate the pain once it has developed. What is still required is understanding when and where an effective novel technique must be applied, such as onto the nerve stump of the transected peripheral axons, dorsal root ganglion neurons, spinal cord, or cortex to induce the desired influences. This review, the second of two in this journal volume, examines the techniques that may be capable of reducing or eliminating chronic neuropathic pain once it has developed. Such an understanding will improve amputees' quality of life by blocking the mechanisms that trigger and/or maintain PLP and chronic neuropathic pain.

Perioperative Pain Management Strategies for Amputation: A Topical Review

Objective

To review acute pain management strategies in patients undergoing amputation with consideration of preoperative patient factors, pharmacologic/interventional modalities, and multidisciplinary care models to alleviate suffering in the immediate post-amputation setting.

Background

Regardless of surgical indication, patients undergoing amputation suffer from significant residual limb pain and phantom limb pain in the acute postoperative phase. Most studies have primarily focused on strategies to prevent persistent pain with inclusion of immediate postoperative outcomes as secondary measures. Pharmacologic agents, including gabapentin, ketamine, and calcitonin, and interventional modalities such as neuraxial and perineural catheters, have been examined in the perioperative period.

Design

Focused Literature Review.

Results

Pharmacologic agents (gabapentin, ketamine, calcitonin) have not shown consistent efficacy. Neuraxial analgesia has demonstrated both an opioid sparing and analgesic benefit while results have been mixed regarding perineural catheters in the immediate post-amputation setting. However, several early studies of perineural catheters employed sub-optimal techniques (distal surgical placement), and prolonged use of perineural catheters may provide a sustained benefit. Regardless of analgesic technique, a multidisciplinary approach is necessary for optimal care.

Conclusion

Patient-tailored analgesic regimens utilizing catheter-based techniques are essential in the acute post-amputation phase and should be implemented in all patients undergoing amputation. Future research should focus on improved measurement of acute pain and comparisons of effective analgesic regimens instead of single techniques.

The AIP Model of EMDR Therapy and Pathogenic Memories

Eye Movement Desensitization and Reprocessing (EMDR) therapy has been widely recognized as an efficacious treatment for post-traumatic stress disorder (PTSD). In the last years more insight has been gained regarding the efficacy of EMDR therapy in a broad field of mental disorders beyond PTSD. The cornerstone of EMDR therapy is its unique model of pathogenesis and change: the adaptive information processing (AIP) model. The AIP model developed by F. Shapiro has found support and differentiation in recent studies on the importance of memories in the pathogenesis of a range of mental disorders beside PTSD. However, theoretical publications or research on the application of the AIP model are still rare. The increasing acceptance of ideas that relate the origin of many mental disorders to the formation and consolidation of implicit dysfunctional memory lead to formation of the theory of pathogenic memories. Within the theory of pathogenic memories these implicit dysfunctional memories are considered to form basis of a variety of mental disorders. The theory of pathogenic memories seems compatible to the AIP model of EMDR therapy, which offers strategies to effectively access and transmute these memories leading to amelioration or resolution of symptoms. Merging the AIP model with the theory of pathogenic memories may initiate research. In consequence, patients suffering from such memory-based disorders may be earlier diagnosed and treated more effectively.

Ultrasound-guided alcohol neurolysis and radiofrequency ablation of painful stump neuroma: effective treatments for post-amputation pain

BACKGROUND

Post-amputation pain (PAP) is highly prevalent after limb amputation, and stump neuromas play a key role in the generation of the pain. Presently, PAP refractory to medical management is frequently treated with minimally invasive procedures guided by ultrasound, such as alcohol neurolysis and radiofrequency ablation (RFA).

OBJECTIVE

To record the immediate and long-term efficacy of alcohol neurolysis and RFA. We first used alcohol neurolysis and then, when necessary, we performed RFA on PAP patients.

STUDY DESIGN

Prospective case series.

SETTING

Pain management center.

METHODS

Thirteen subjects were treated with ultrasound-guided procedures.

RESULTS

All patients were treated with neurolysis using alcohol solutions guided by ultrasound. Seven (54%) of 13 subjects achieved pain relief after 1-3 alcohol injection treatments. The remaining 6 subjects obtained pain relief after receiving 2 administrations of ultrasound-guided RFA. After a 6-month follow-up evaluation period, pain quantities were also assessed. Both stump pain (including intermittent sharp pain and continuous burning pain) and phantom pain were relieved. The frequency of intermittent sharp pain was decreased, and no complications were noted during the observation.

CONCLUSION

The use of ultrasound guidance for alcohol injection and RFA of painful stump neuromas is a simple, radiation-free, safe, and effective procedure that provides sustained pain relief in PAP patients. In this case series, RFA was found to be an effective alternative to alcohol injection.

Percutaneous Image-Guided Cryoablation for the Treatment of Phantom Limb Pain in Amputees: A Pilot Study

PURPOSE

To prospectively evaluate percutaneous image-guided nerve cryoablation for treatment of refractory phantom limb pain (PLP) in a pilot cohort for purposes of deriving parameters to design a larger, randomized, parallel-armed, controlled trial.

MATERIALS AND METHODS

From January 2015 to January 2016, 21 patients with refractory PLP underwent image-guided percutaneous cryoneurolysis procedures. Visual analog scale scores were documented at baseline and 7, 45, and 180 days after the procedure. Responses to a modified Roland Morris Disability Questionnaire were documented at baseline and 7 and 45 days after the procedure.

RESULTS

Technical success rate of the procedures was 100%. There were 6 (29%) minor procedure-related complications. Disability scores decreased from a baseline mean of 11.3 to 3.3 at 45-day follow-up (95% confidence interval 5.8, 10.3; P < .0001). Pain intensity scores decreased from a baseline mean of 6.2 to 2.0 at long-term follow-up (95% confidence interval 2.8, 5.6; P < .0001).

CONCLUSIONS

Image-guided percutaneous nerve cryoablation is feasible and safe and may represent a new efficacious therapeutic option for patients with phantom pains related to limb loss.