Neuromas and postamputation pain

Neuroma Analysis in Humans: Standardizing Sample Collection and Documentation

INTRODUCTION

The biology of symptomatic neuromas is poorly understood, particularly the factors causing pain in human neuromas. Pain presence varies among and within individuals, with some having painful and nonpainful neuromas. To bridge these knowledge gaps, our group developed a protocol for assessing neuroma pain and collecting tissue for molecular analysis. This manuscript outlines our workflow and challenges and aims to inspire other centers to share their experiences with these tissues.

METHODS

For every included patient and collected nerve or bone tissue specimens, we perform a detailed chart review and a multifaceted analysis of pain and pain perception immediately before surgery. We collect patient-reported outcome measures (PROMs) on pain, function, and mental well-being outcomes at preoperative assessment and at the 6-month follow-up postoperatively. Before surgery, the patient is assessed once again to obtain an immediate preoperative pain status and identify potential differences in pain intensity of different neuromas. Intraoperatively, specimens are obtained and their gross anatomical features are recorded, after which they are stored in paraformaldehyde or frozen for later sample analyses. Postoperatively, patients are contacted to obtain additional postoperative PROMs.

RESULTS

A total of 220 specimens of nerve tissue have been successfully obtained from 83 limbs, comprising 95 specimens of neuromas and 125 specimens of nerves located proximal to the neuromas or from controls.

CONCLUSIONS

Our approach outlines the methods combining specimen collection and examination, including both macroscopic and molecular biological features, with PROMs, encompassing physical and psychological aspects, along with clinical metadata obtained through clinical teams and chart review.

Nociceptor spontaneous activity is responsible for fragmenting non-rapid eye movement sleep in mouse models of neuropathic pain

Spontaneous pain, a major complaint of patients with neuropathic pain, has eluded study because there is no reliable marker in either preclinical models or clinical studies. Here, we performed a comprehensive electroencephalogram/electromyogram analysis of sleep in several mouse models of chronic pain: neuropathic (spared nerve injury and chronic constriction injury), inflammatory (Freund's complete adjuvant and carrageenan, plantar incision) and chemical pain (capsaicin). We find that peripheral axonal injury drives fragmentation of sleep by increasing brief arousals from non-rapid eye movement sleep (NREMS) without changing total sleep amount. In contrast to neuropathic pain, inflammatory or chemical pain did not increase brief arousals. NREMS fragmentation was reduced by the analgesics gabapentin and carbamazepine, and it resolved when pain sensitivity returned to normal in a transient neuropathic pain model (sciatic nerve crush). Genetic silencing of peripheral sensory neurons or ablation of CGRP+ neurons in the parabrachial nucleus prevented sleep fragmentation, whereas pharmacological blockade of skin sensory fibers was ineffective, indicating that the neural activity driving the arousals originates ectopically in primary nociceptor neurons and is relayed through the lateral parabrachial nucleus. These findings identify NREMS fragmentation by brief arousals as an effective proxy to measure spontaneous neuropathic pain in mice.

Pain in the Context of Sensory Deafferentation

Pain that accompanies deafferentation is one of the most mysterious and misunderstood medical conditions. Prevalence rates for the assorted conditions vary considerably but the most reliable estimates are greater than 50% for strokes involving the somatosensory system, brachial plexus avulsions, spinal cord injury, and limb amputation, with controversy surrounding the mechanistic contributions of deafferentation to ensuing neuropathic pain syndromes. Deafferentation pain has also been described for loss of other body parts (e.g., eyes and breasts) and may contribute to between 10% and upwards of 30% of neuropathic symptoms in peripheral neuropathies. There is no pathognomonic test or sign to identify deafferentation pain, and part of the controversy surrounding it stems from the prodigious challenges in differentiating cause and effect. For example, it is unknown whether cortical reorganization causes pain or is a byproduct of pathoanatomical changes accompanying injury, including pain. Similarly, ascertaining whether deafferentation contributes to neuropathic pain, or whether concomitant injury to nerve fibers transmitting pain and touch sensation leads to a deafferentation-like phenotype can be clinically difficult, although a detailed neurologic examination, functional imaging, and psychophysical tests may provide clues. Due in part to the concurrent morbidities, the physical, psychologic, and by extension socioeconomic costs of disorders associated with deafferentation are higher than for other chronic pain conditions. Treatment is symptom-based, with evidence supporting first-line antineuropathic medications such as gabapentinoids and antidepressants. Studies examining noninvasive neuromodulation and virtual reality have yielded mixed results.

Effect of pain on activity and participation in individuals with unilateral lower-extremity amputation based on the International Classification of Functioning, Disability, and Health

BACKGROUND

Amputation is a major life-changing event and is regarded as one of the loading causes of permanent disability. However, amputation often causes changes in painful and nonpainful sensory experiences. Pain after amputation has been shown to increase functional limitations caused by limb loss and lower quality of life.

OBJECTIVE

This study aimed to examine the effect of pain on activity and participation in individuals with unilateral below-knee amputations according to the International Classification of Functioning, Disability, and Health.

STUDY DESIGN

Cross-sectional study.

METHODS

In the study, 64 individuals were divided into 2 groups: those who experienced pain and those who did not. Group 1 included 33 below-knee amputees who experienced pain (27 males, mean age 43.9 ± 12.6 years) and Group 2 included 31 below-knee amputees who did not experience pain (25 males, mean age 47.4 ± 12.1 years). The McGill Pain Questionnaire and visual analog scale were used to assess pain, the Prosthetic Limb Users Survey of Mobility was used to assess activity, and the Reintegration to Normal Living Index was used to assess participation.

RESULTS

Demographic characteristics of the 2 groups were statistically insignificant (P > 0.05). The nonpainful group had significantly higher activity and participation scores than the painful group (P < 0.001).

CONCLUSIONS

It was found that phantom pain and stump pain in below-knee amputees limited activity and participation. It was also shown that phantom pain has a more negative effect on the activity level of individuals than stump pain.

Introduction to Limb Deficiency for the Pediatrician

Owing to the lack of trained professionals in amputee care, the pediatrician is often required to assist in the care of children with limb deficiencies. An overview of the causes and epidemiology of limb deficiency is provided, as well as an evaluation and diagnostic workup. Important considerations for surgical interventions are discussed and an introduction to prosthetic prescribing and care of the amputee is described. Common overuse syndromes and mental health issues are also reviewed. Finally, resources for funding of prosthetic devices, as well as support and education for clinicians and families are provided.

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.

Factors Related to Neuropathic Pain following Lower Extremity Amputation

BACKGROUND

Lower extremity amputations are common, and postoperative neuropathic pain (phantom limb pain or symptomatic neuroma) is frequently reported. The use of active treatment of the nerve end has been shown to reduce pain but requires additional resources and should therefore be performed primarily in high-risk patients. The aim of this study was to identify the factors associated with the development of neuropathic pain following above-the-knee amputation, knee disarticulation, or below-the-knee amputation.

METHODS

Retrospectively, 1565 patients with an average follow-up of 4.3 years who underwent a primary above-the-knee amputation, knee disarticulation, or below-the-knee amputation were identified. Amputation levels for above-the-knee amputations and knee disarticulations were combined as proximal amputation level, with below-the-knee amputations being performed in 61 percent of patients. The primary outcome was neuropathic pain (i.e., phantom limb pain or symptomatic neuroma) based on medical chart review. Multivariable logistic regression was performed to identify independent factors associated with neuropathic pain.

RESULTS

Postoperative neuropathic pain was present in 584 patients (37 percent), with phantom limb pain occurring in 34 percent of patients and symptomatic neuromas occurring in 3.8 percent of patients. Proximal amputation level, normal creatinine levels, and a history of psychiatric disease were associated with neuropathic pain. Diabetes, hypothyroidism, and older age were associated with lower odds of developing neuropathic pain.

CONCLUSIONS

Neuropathic pain following lower extremity amputation is common. Factors influencing nerve regeneration, either increasing (proximal amputations and younger age) or decreasing (diabetes, hypothyroidism, and chronic kidney disease) it, play a role in the development of postamputation neuropathic pain.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Prophylactic Regenerative Peripheral Nerve Interfaces in Elective Lower Limb Amputations

Regenerative peripheral nerve interface (RPNI) is a relatively new surgical technique to manage neuromas and phantom pain after limb amputation. This study evaluates prophylactic RPNI efficacy in managing post-amputation pain and neuroma formation in amputees compared with patients in which lower limb amputation was performed without this procedure. We included 28 patients who underwent above the knee amputation (AKA) or below the knee amputation (BKA) for severe soft tissue infection from July 2019 till December 2020. All patients had insulin-dependent diabetes. The patients were divided into two groups, 14 patients with primary RPNI and 14 patients without. We analyzed the demographic data, level of amputation, number of RPNIs, operative time, postoperative complications and functional outcome on the defined follow up period. The mean patient age was 68.6 years (range 49-85), 19 (67.9 %) male and 9 (32.1 %) female patients. In this study 11 (39.3 %) AKA and 17 (60.7 %) BKA were performed. Overall, 37 RPNIs were made. The mean follow-up period was 49 weeks. PROMIS T-score decreased by 15.9 points in favor for the patients with RPNI. The VAS score showed that, in the RPNI group, all 14 patients were without pain compared to the group of patients without RPNI, where the 11 (78.6 %) patients described their pain as severe. Patients with RPNI used prosthesis significantly more (p < 0.005). Data showed significant reduction in pain and high patient satisfaction after amputation with RPNIs. This technique is oriented as to prevent neuroma formation with RPNI surgery, performed at the time of amputation. RPNI surgery did not provoke complications or significant lengthening of operative time and it should be furthermore exploited as a surgical technique.

The structure of sensory afferent compartments in health and disease

Primary sensory neurons are a heterogeneous population of cells able to respond to both innocuous and noxious stimuli. Like most neurons they are highly compartmentalised, allowing them to detect, convey and transfer sensory information. These compartments include specialised sensory endings in the skin, the nodes of Ranvier in myelinated axons, the cell soma and their central terminals in the spinal cord. In this review, we will highlight the importance of these compartments to primary afferent function, describe how these structures are compromised following nerve damage and how this relates to neuropathic pain.

MRI features of symptomatic amputation neuromas

OBJECTIVES

To demonstrate the magnetic resonance imaging (MRI) features of amputation neuromas in lower extremity amputees and investigate independent predictive MRI features for symptomatic neuromas.

METHODS

This retrospective study included 45 amputation neuromas in 44 lower extremity amputees. Two radiologists assessed the imaging features, including shape, size, type (end-bulb or spindle), signal intensity (SI), heterogeneity, margins, enlarged fascicles, dark outer rim, tail sign, target sign, enhancement, perilesional fibrosis, and muscle denervation. The neuromas were categorized into symptomatic (n = 24) or asymptomatic (n = 21). Symptomatic neuromas were determined based on neuropathic pain characteristics, the presence of Tinel's sign or tenderness, and response to local anesthetic injection. Univariate and multivariate analyses were performed to identify independent predictive MRI features.

RESULTS

Of 45 neuromas, 80% (36/45) were end-bulb neuromas and 20% (9/45) were spindle-type neuromas. Eighty percent of the neuromas (36/45) were heterogeneous on T2-weighted images (WIs). Enlarged fascicles were present in 42% (19/45) and dark outer rims in 27% (12/45) of the neuromas. Among the 23 neuromas with enhanced images, 78% (18/23) showed enhancement. Heterogeneity on T2-WIs and enhancement ratios were significantly different between the asymptomatic and symptomatic neuroma groups (p < 0.05). The multivariate analyses indicated that heterogeneity on T2-WIs was an independent factor associated with symptomatic neuromas (p < 0.001).

CONCLUSIONS

Heterogeneity on T2-WIs could be a predictive indicator for symptomatic neuromas in lower extremity amputees.

KEY POINTS

• Amputation neuromas are classified as either end-bulb or spindle-type. They can show enlarged fascicles, dark outer rims, and enhancement. • Heterogeneity on T2-weighted images could be a predictive indicator for symptomatic neuromas. • Predicting the symptomatic neuroma on MRI would help in effective management of stump pain.

The Phantom Satiation Hypothesis of Bariatric Surgery

The excitation of vagal mechanoreceptors located in the stomach wall directly contributes to satiation. Thus, a loss of gastric innervation would normally be expected to result in abrogated satiation, hyperphagia, and unwanted weight gain. While Roux-en-Y-gastric bypass (RYGB) inevitably results in gastric denervation, paradoxically, bypassed subjects continue to experience satiation. Inspired by the literature in neurology on phantom limbs, I propose a new hypothesis in which damage to the stomach innervation during RYGB, including its vagal supply, leads to large-scale maladaptive changes in viscerosensory nerves and connected brain circuits. As a result, satiation may continue to arise, sometimes at exaggerated levels, even in subjects with a denervated or truncated stomach. The same maladaptive changes may also contribute to dysautonomia, unexplained pain, and new emotional responses to eating. I further revisit the metabolic benefits of bariatric surgery, with an emphasis on RYGB, in the light of this phantom satiation hypothesis.

Managing Neuroma and Phantom Limb Pain in Ontario: The Status of Targeted Muscle Reinnervation

Supplemental Digital Content is available in the text.

Background:

Painful neuromas (PN) and phantom limb pain (PLP) are common following amputation and are unreliably treated, which impacts quality of life. Targeted muscle reinnervation (TMR) is a microsurgical technique that repairs the severed proximal nerve end to a redundant motor nerve in the amputated stump. Evidence supports TMR as effective in treating PN and PLP; however, its adoption has been slow. This study aimed to characterize: (1) the populations experiencing post-amputation PN/PLP; (2) current trends in managing PN/PLP; and (3) attitudes toward routine use of TMR to manage PN/PLP.

Methods:

A cross-sectional survey was distributed to all orthopedic surgeons, plastic surgeons, and physiatrists practicing in Ontario, via publicly available emails and specialty associations. Data were collected on demographics, experience with amputation, managing post-amputation pain, and attitudes toward routine use of TMR.

Results:

Sixty-six of 698 eligible participants submitted complete surveys (9.5% response rate). Respondents had a greater experience with surgical management of PN (71% PN versus 10% PLP). However, surgery was considered a 3rd-line option for PN and not an option for PLP in 57% and 59% of respondents, respectively. Thirty participants (45%) were unaware of TMR as an option, and only 8 respondents have currently incorporated TMR into their practice. Many (76%) would be willing to incorporate TMR into their practice as either an immediate or delayed surgical technique.

Conclusions:

Despite its promise in managing post-amputation pain, awareness of TMR as a surgical option is generally poor. Several barriers to the widespread adoption of this technique are defined.

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.

Covering the proximal nerve stump with chondroitin sulfate proteoglycans prevents traumatic painful neuroma formation by blocking axon regeneration after neurotomy in Sprague Dawley rats

OBJECTIVE

Neuropathic pain caused by traumatic neuromas is an extremely intractable clinical problem. Disorderly scar tissue accumulation and irregular and immature axon regeneration around the injury site mainly contribute to traumatic painful neuroma formation. Therefore, successfully preventing traumatic painful neuroma formation requires the effective inhibition of irregular axon regeneration and disorderly accumulation of scar tissue. Considering that chondroitin sulfate proteoglycans (CSPGs) can act on the growth cone and effectively inhibit axon regeneration, the authors designed and manufactured a CSPG-gelatin blocker to regulate the CSPGs' spatial distribution artificially and applied it in a rat model after sciatic nerve neurectomy to evaluate its effects in preventing traumatic painful neuroma formation.

METHODS

Sixty female Sprague Dawley rats were randomly divided into three groups (positive group: no covering; blank group: covering with gelatin blocker; and CSPG group: covering with the CSPG-gelatin blocker). Pain-related factors were evaluated 2 and 8 weeks postoperatively (n = 30). Neuroma growth, autotomy behavior, and histological features of the neuromas were assessed 8 weeks postoperatively (n = 30).

RESULTS

Eight weeks postoperatively, typical bulb-shaped neuromas did not form in the CSPG group, and autotomy behavior was obviously better in the CSPG group (p < 0.01) than in the other two groups. Also, in the CSPG group the regenerated axons showed a lower density and more regular and improved myelination (p < 0.01). Additionally, the distribution and density of collagenous fibers and the expression of α-smooth muscle actin were significantly lower in the CSPG group than in the positive group (p < 0.01). Regarding pain-related factors, c-fos, substance P, interleukin (IL)-17, and IL-1β levels were significantly lower in the CSPG group than those in the positive and blank groups 2 weeks postoperatively (p < 0.05), while substance P and IL-17 remained lower in the CSPG group 8 weeks postoperatively (p < 0.05).

CONCLUSIONS

The authors found that CSPGs loaded in a gelatin blocker can prevent traumatic neuroma formation and effectively relieve pain symptoms after sciatic nerve neurotomy by blocking irregular axon regeneration and disorderly collagenous fiber accumulation in the proximal nerve stump. These results indicate that covering the proximal nerve stump with CSPGs may be a new and promising strategy to prevent traumatic painful neuroma formation in the clinical setting.