Temporal Summation Predicts De Novo Contralateral Pain After Cordotomy in Patients With Refractory Cancer Pain

BACKGROUND

Percutaneous cervical cordotomy (PCC), which selectively interrupts ascending nociceptive pathways in the spinal cord, can mitigate severe refractory cancer pain. It has an impressive success rate, with most patients emerging pain-free. Aside from the usual complications of neurosurgical procedures, the risks of PCC include development of contralateral pain, which is less understood.

OBJECTIVE

To evaluate whether sensory and pain sensitivity, as measured by quantitative sensory testing (QST), are associated with PCC clinical outcomes.

METHODS

Fourteen palliative care cancer patients with severe chronic refractory pain limited mainly to one side of the body underwent comprehensive quantitative sensory testing assessment pre-PPC and post-PCC. They were also queried about maximal pain during the 24 h precordotomy (0-10 numerical pain scale).

RESULTS

All 14 patients reported reduced pain postcordotomy, with 7 reporting complete resolution. Four patients reported de novo contralateral pain. Reduced sensitivity in sensory and pain thresholds to heat and mechanical stimuli was recorded on the operated side (P = .028). Sensitivity to mechanical pressure increased on the unaffected side (P = .023), whereas other sensory thresholds were unchanged. The presurgical temporal summation values predicted postoperative contralateral pain (r = 0.582, P = .037).

CONCLUSION

The development of contralateral pain in patients postcordotomy for cancer pain might be due to central sensitization. Temporal summation could serve as a potential screening tool to identify those who are most likely at risk to develop contralateral pain. Analysis of PCC affords a unique opportunity to investigate how a specific lesion to the nociceptive system affects pain processes.

Productivity versus drought adaptation in olive leaves: Comparison of water relations in a modern versus a traditional cultivar

The physiological traits that set the tradeoff between productivity and drought adaptation in plants are still under debate. To reveal these traits, we compared the water relations of two olive (Olea europaea) cultivars: "Barnea"-a highly productive modern cultivar; and "Souri"-a drought-adapted traditional cultivar. We hypothesized that Souri has lower hydraulic conductivity and lower hydraulic vulnerability. The hypothesis was tested at the leaf level. The soil volumetric water content (θ), stem water potential (Ψ_S ), and gas exchange were measured in both cultivars while they dried until a significant reduction in their maximal photochemical potential (F_v /F_m  < 0.6) was obtained. Additionally, pressure-volume relations, leaf hydraulic vulnerability, and the petiole xylem architecture were evaluated. To our surprise, Souri's leaf hydraulic conductivity was more vulnerable to low Ψ_S , approaching zero at -8 MPa compared with <-10 MPa in "Barnea." At the same time, Souri's higher osmotic content and cell rigidity enabled it to sustain 1.4 MPa lower Ψ_S , while maintaining near optimal (F_v /F_m ). However, both cultivars significantly reduced their F_v /F_m (<0.6) at the same θ, suggesting that the capability to sustain a low θ is not the issue. Instead, Souri's lower transpiration enabled it to withstand a longer drought while avoiding low θ. Barnea's larger xylem vessels and hydraulic conductivity supported higher stomatal conductance (g_s ) and assimilation rate, which nurtured its higher productivity but resulted in quick depletion of θ. These results suggest that hydraulic resistance or the ability to sustain low θ do not set the tradeoff between productivity and drought adaptation in olive leaves.

A New Solution to an Old Problem: Ultrasound-guided Cervical Retrolaminar Injection for Acute Cervical Radicular Pain: Prospective Clinical Pilot Study and Cadaveric Study

STUDY DESIGN

Prospective clinical pilot study and cadaveric study.

OBJECTIVE

The aim of this study was to evaluate the spread of an ultrasound-guided interfascial plane blocks (UGIPBs) and its potential efficacy for cervical radiculopathy.

SUMMARY OF BACKGROUND DATA

Cervical radiculopathy is a common disorder, potentially leading to severe pain and disability. Conservative treatment with cervical epidural steroid injections (ESI) is limited by concerns regarding their safety. UGIPBs are used in cervical surgical procedures as part of the multimodal postoperative analgesia regimen however, were not described for cervical radiculopathy.

METHODS

Twelve patients with acute cervical radicular pain who failed conservative treatment and were candidates for surgery were offered a cervical retrolaminar injection. A solution of 4 mL lidocaine 0.5% and 10 mg dexamethasone was injected, assisted by ultrasound guidance, at the posterior aspect of the cervical lamina corresponding to the compressed nerve root level. Additionally, a cadaver study was carried to evaluate the contrast spread and infiltration into near structures, both anatomically and radiographically.

RESULTS

Twelve patients underwent the procedure, with a mean follow-up time of 14.5 weeks. Average numerical rating scale improved from 7.25 at baseline to 2.83 following the injection (P < 0.001). Three patients received 2 to 3 injections without significant improvement and were eventually operated. No adverse events were reported.In the cadaver study, fluoroscopy demonstrated contrast spread between T1 and T3 caudally, C2 to C5 cranially and facet joints laterally. Anatomically, the dye spread was demonstrated up to C2 cranially, T1 caudally, the articular pillars of C4 to C7, and the neural foramen of C6 laterally.

CONCLUSION

A solution injected into the cervical retrolaminar plane can diffuse in the cranial-caudal axis to C2-T3 and laterally to the facet joints and the cervical neural foramen. Our pilot study confirmed the feasibility of our study protocol. Future studies are needed to support our early results.Level of Evidence: 4.

Pain Management - A Decade's Perspective of a New Subspecialty

Objective

Pain management is increasingly recognized as a formal medical subspecialty worldwide. Israel was among the first to offer a board-certified subspecialty, formalized by the Israeli Medical Association in 2010 which is open to all clinicians with a state-recognized specialization. This paper aims at evaluating the current program across several quality control measures.

Design

A survey among pain medicine specialists who graduated from the Israeli Pain Management subspecialty.

Methods

All 43 graduates of the program were sent a web-based questionnaire, each related to a different time in the participants' residency period - prior to, during and after training.

Results

Forty-one physicians responded to the survey (95% response rate). The most common primary specialty was Anesthesiology (44%), followed by Family Medicine (22%). One-third of the respondents applied to the program over five years after completing their initial residency. Two-thirds reported that they acquired all or most of the professional tools required by a pain specialist. Insufficient training was mentioned regarding addiction management (71%), special population needs (54%) and interventional treatment (37%). A high proportion (82%) responded that the examination contributed to their training and almost all perceived their period of subspecialty as having a positive value in their personal development. Two-thirds of respondents had not yet actively engaged beyond the clinical aspect with other entities responsible for formulating guidelines and other strategic decision-making.

Conclusion

We hope the findings of this first-of-a-kind survey will encourage other medical authorities to construct formal training in pain medicine and enable this discipline to further evolve.

Cervical Cordotomy for Intractable Pain: Do Postoperative Imaging Features Correlate with Pain Outcomes and Mirror Pain?

BACKGROUND AND PURPOSE

Percutaneous cervical cordotomy offers relief of unilateral intractable oncologic pain. We aimed to find anatomic and postoperative imaging features that may correlate with clinical outcomes, including pain relief and postoperative contralateral pain.

MATERIALS AND METHODS

We prospectively followed 15 patients with cancer who underwent cervical cordotomy for intractable pain during 2018 and 2019 and underwent preoperative and up to 1-month postoperative cervical MR imaging. Lesion volume and diameter were measured on T2-weighted imaging and diffusion tensor imaging (DTI). Lesion mean diffusivity and fractional anisotropy values were extracted. Pain improvement up to 1 month after surgery was assessed by the Numeric Rating Scale and Brief Pain Inventory.

RESULTS

All patients reported pain relief from 8 (7-10) to 0 (0-4) immediately after surgery (P = .001), and 5 patients (33%) developed contralateral pain. The minimal percentages of the cord lesion volume required for pain relief were 10.0% on T2-weighted imaging and 6.2% on DTI. Smaller lesions on DWI correlated with pain improvement on the Brief Pain Inventory scale (r = 0.705, P = .023). Mean diffusivity and fractional anisotropy were significantly lower in the ablated tissue than contralateral nonlesioned tissue (P = .003 and P = .001, respectively), compatible with acute-phase tissue changes after injury. Minimal postoperative mean diffusivity values correlated with an improvement of Brief Pain Inventory severity scores (r = -0.821, P = .004). The average lesion mean diffusivity was lower among patients with postoperative contralateral pain (P = .037).

CONCLUSIONS

Although a minimal ablation size is required during cordotomy, larger lesions do not indicate better outcomes. DWI metrics changes represent tissue damage after ablation and may correlate with pain outcomes.

An increase in xylem embolism resistance of grapevine leaves during the growing season is coordinated with stomatal regulation, turgor loss point and intervessel pit membranes

Although xylem embolism resistance is traditionally considered as static, we hypothesized that in grapevine (Vitis vinifera) leaf xylem becomes more embolism-resistant over the growing season. We evaluated xylem architecture, turgor loss point (Ψ_TLP ) and water potentials leading to 25% of maximal stomatal conductance (g_s25 ) or 50% embolism in the leaf xylem (P₅₀ ) in three irrigation treatments and at three time points during the growing season, while separating the effects of leaf age and time of season. Hydraulic traits acclimated over the growing season in a coordinated manner. Without irrigation, Ψ_TLP , g_s25 , and P₅₀ decreased between late May and late August by 0.95, 0.77 and 0.71 MPa, respectively. A seasonal shift in P₅₀ occurred even in mature leaves, while irrigation had only a mild effect (< 0.2 MPa) on P₅₀ . Vessel size and pit membrane thickness were also seasonally dynamic, providing a plausible explanation for the shift in P₅₀ . Our findings provide clear evidence that grapevines can modify their hydraulic traits along a growing season to allow lower xylem water potential, without compromising gas exchange, leaf turgor or xylem integrity. Seasonal changes should be considered when modeling ecosystem vulnerability to drought or comparing datasets acquired at different phenological stages.

Interventional Pain Management for Cancer Pain: An Analysis of Outcomes and Predictors of Clinical Response

Background: Interventional procedures are offered routinely to patients seen in McGill University’s interdisciplinary cancer pain management program. However, publications on these procedures are scarce, making it difficult to predict which patients may benefit from them. Objectives: We hypothesized that interventional pain procedures offered to cancer patients could provide relief of pain as well as other symptoms. Furthermore, some variables may predict the efficacy of such procedures. Study Design: We conducted a retrospective chart review of interventional pain management procedures. Setting: The procedures reviewed were conducted at the Cancer Pain Program and performed at the interventional suites of the McGill University Health Centre. Methods: The retrospective chart review included interventional pain management procedures performed between June 2015 and March 2017. Demographic data, details about the underlying cancer and about the procedure and peripTrocedural patients’ reported outcomes were recorded for analysis. Results: Eighty-two of 126 procedures were included for analysis. Most patients presented with metastatic disease (75%). Eighty percent of the patients reported pain relief, with the average pain severity decreasing by more than 2 points on a 0-to-10 Numeric Rating Scale for pain (from 6.5 of 10 to 4.2 of 10). Forty-three percent of patients were considered responders (≥ 50% pain relief). Responders also reported a significant decrease in fatigue, depression, anxiety, drowsiness, and improved well-being. Among responders, average daily opioid use decreased significantly, by 60% on average. None of the analyzed variables correlated with the response; however, psychosocial variables like anxiety and depression showed a nonsignificant trend towards predicting procedure failure. Limitations: The core limitations of this study are its size and retrospective nature. Conclusions: In this cohort of cancer pain patients, interventional cancer pain procedures provided effective pain relief and other benefits, including pain relief, reduced burden of symptoms, and reduction of opioid intake, while demonstrating a favorable safety profile. Patients with poorer ratings of depression and fatigue derived less benefit from procedures, suggesting that offering such procedures as part of patients’ treatment plan would be sensible, rather than leaving interventions for later stages. Key words: Cancer pain, pain management, pain intractable, treatment outcomes, palliative care, advanced cancer, cancer, evidence-based madicine

Interventional Pain Management for Cancer Pain: An Analysis of Outcomes and Predictors of Clinical Response

BACKGROUND

Interventional procedures are offered routinely to patients seen in McGill University's interdisciplinary cancer pain management program. However, publications on these procedures are scarce, making it difficult to predict which patients may benefit from them.

OBJECTIVES

We hypothesized that interventional pain procedures offered to cancer patients could provide relief of pain as well as other symptoms. Furthermore, some variables may predict the efficacy of such procedures.

STUDY DESIGN

We conducted a retrospective chart review of interventional pain management procedures.

SETTING

The procedures reviewed were conducted at the Cancer Pain Program and performed at the interventional suites of the McGill University Health Centre.

METHODS

The retrospective chart review included interventional pain management procedures performed between June 2015 and March 2017. Demographic data, details about the underlying cancer and about the procedure and peripTrocedural patients' reported outcomes were recorded for analysis.

RESULTS

Eighty-two of 126 procedures were included for analysis. Most patients presented with metastatic disease (75%). Eighty percent of the patients reported pain relief, with the average pain severity decreasing by more than 2 points on a 0-to-10 Numeric Rating Scale for pain (from 6.5 of 10 to 4.2 of 10). Forty-three percent of patients were considered responders (>= 50% pain relief). Responders also reported a significant decrease in fatigue, depression, anxiety, drowsiness, and improved well-being. Among responders, average daily opioid use decreased significantly, by 60% on average. None of the analyzed variables correlated with the response; however, psychosocial variables like anxiety and depression showed a nonsignificant trend towards predicting procedure failure.

LIMITATIONS

The core limitations of this study are its size and retrospective nature.

CONCLUSIONS

In this cohort of cancer pain patients, interventional cancer pain procedures provided effective pain relief and other benefits, including pain relief, reduced burden of symptoms, and reduction of opioid intake, while demonstrating a favorable safety profile. Patients with poorer ratings of depression and fatigue derived less benefit from procedures, suggesting that offering such procedures as part of patients' treatment plan would be sensible, rather than leaving interventions for later stages.

The physiology of drought stress in grapevine: towards an integrative definition of drought tolerance

Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance?

Leaf Carbon Export and Nonstructural Carbohydrates in Relation to Diurnal Water Dynamics in Mature Oak Trees

Trees typically experience large diurnal depressions in water potential, which may impede carbon export from leaves during the day because the xylem is the source of water for the phloem. As water potential becomes more negative, higher phloem osmotic concentrations are needed to draw water in from the xylem. Generating this high concentration of sugar in the phloem is particularly an issue for the ∼50% of trees that exhibit passive loading. These ideas motivate the hypothesis that carbon export in woody plants occurs predominantly at night, with sugars that accumulate during the day assisting in mesophyll turgor maintenance or being converted to starch. To test this, diurnal and seasonal patterns of leaf nonstructural carbohydrates, photosynthesis, solute, and water potential were measured, and carbon export was estimated in leaves of five mature (>20 m tall) red oak (Quercus rubra) trees, a species characterized as a passive loader. Export occurred throughout the day at equal or higher rates than at night despite a decrease in water potential to -1.8 MPa at midday. Suc and starch accumulated over the course of the day, with Suc contributing ∼50% of the 0.4 MPa diurnal osmotic adjustment. As a result of this diurnal osmotic adjustment, estimates of midday turgor were always >0.7 MPa. These findings illustrate the robustness of phloem functioning despite diurnal fluctuations in leaf water potential and the role of nonstructural carbohydrates in leaf turgor maintenance.

Tailoring of neurosurgical ablative procedures in the management of refractory cancer pain

INTRODUCTION

Neurosurgical ablative procedures can offer immediate and effective pain relief for patients suffering from refractory cancer pain. However, choosing the appropriate procedure for each patient may not be straightforward and warrants an interdisciplinary approach. The purpose of the current study was to evaluate the outcome of patients with cancer who were carefully selected for neurosurgical intervention by a dedicated interdisciplinary team composed of a palliative physician and nurse practitioner, a pain specialist and a neurosurgeon.

METHODS

A retrospective review was carried out on all patients who underwent neurosurgical ablative procedures in our institute between March 2015 and September 2019. All patients had advanced metastatic cancer with unfavorable prognosis and suffered from intractable oncological pain. Each treatment plan was devised to address the patients' specific pain syndromes.

RESULTS

A total of 204 patients were examined by our service during the study period. Sixty-four patients with localized pain and nineteen patients with diffuse pain syndromes were selected for neurosurgical interventions, either targeted disconnection of the spinothalamic tract or stereotactic cingulotomy. Substantial pain relief was reported by both groups immediately (cordotomy: Numerical Rating Scale (NRS) 9 ≥1, p=0.001, cingulotomy: NRS 9 ≥2, p=0.001) and maintained along the next 3-month follow-up visits.

CONCLUSIONS

An interdisciplinary collaboration designated to provide neurosurgical ablative procedures among carefully selected patients could culminate in substantial relief of intractable cancer pain.

TRIAL REGISTRATION NUMBER

IR0354-17.

Visualizing Embolism Propagation in Gas-Injected Leaves

Because the xylem in leaves is thought to be at the greatest risk of cavitation, reliable and efficient methods to characterize leaf xylem vulnerability are of interest. We report a method to generate leaf xylem vulnerability curves (VCs) by gas injection. Using optical light transmission, we visualized embolism propagation in grapevine (Vitis vinifera) and red oak (Quercus rubra) leaves injected with positive gas pressure. This resulted in a rapid, stepwise reduction of transmitted light, identical to that observed during leaf dehydration, confirming that the optical method detects gas bubbles and provides insights into the air-seeding hypothesis. In red oak, xylem VCs generated using gas injection were similar to those generated using bench dehydration, but indicated 50% loss of conductivity at lower tension (∼0.4 MPa) in grapevine. In determining VC, this method eliminates the need to ascertain xylem tension, thus avoiding potential errors in water potential estimations. It is also much faster (1 h per VC). However, severing the petiole and applying high-pressure gas could affect air-seeding and the generated VC. We discuss potential artifacts arising from gas injection and recommend comparison of this method with a more standard procedure before it is assumed to be suitable for a given species.

Neurosurgical ablative procedures for intractable cancer pain

OBJECTIVE

Cancer patients suffering from severe refractory pain may benefit from targeted ablative neurosurgical procedures aimed to disconnect pain pathways in the spinal cord or the brain. These patients often present with a plethora of medical problems requiring careful consideration before surgical interventions. The authors present their experience at an interdisciplinary clinic aimed to facilitate appropriate patient selection for neurosurgical procedures, and the outcome of these interventions.

METHODS

This study was a retrospective review of all patients who underwent neurosurgical interventions for cancer pain in the authors' hospital between March 2015 and April 2018. All patients had advanced metastatic cancer with limited life expectancy and suffered from intractable oncological pain.

RESULTS

Sixty patients underwent surgery during the study period. Forty-three patients with localized pain underwent disconnection of the spinal pain pathways: 34 percutaneous-cervical and 5 open-thoracic cordotomies, 2 stereotactic mesencephalotomies, and 2 midline myelotomies. Thirty-nine of 42 patients (93%) who completed these procedures had excellent immediate postoperative pain relief. At 1 month the improvement was maintained in 30/36 patients (83%) available for follow-up. There was 1 case of hemiparesis.Twenty patients with diffuse pain underwent stereotactic cingulotomy. Nineteen of these patients reported substantial pain relief immediately after the operation. At 1 month good pain relief was maintained in 13/17 patients (76%) available for follow-up, and good pain relief was also found at 3 months in 7/11 patients (64%). There was no major morbidity or mortality.

CONCLUSIONS

With careful patient selection and tailoring of the appropriate procedure to the patient's pain syndrome, the authors' experience indicates that neurosurgical procedures are safe and effective in alleviating suffering in patients with intractable cancer pain.

Swift metabolite changes and leaf shedding are milestones in the acclimation process of grapevine under prolonged water stress

BACKGROUND

Grape leaves provide the biochemical substrates for berry development. Thus, understanding the regulation of grapevine leaf metabolism can aid in discerning processes fundamental to fruit development and berry quality. Here, the temporal alterations in leaf metabolism in Merlot grapevine grown under sufficient irrigation and water deficit were monitored from veraison until harvest.

RESULTS

The vines mediated water stress gradually and involving multiple strategies: osmotic adjustment, transcript-metabolite alteration and leaf shedding. Initially stomatal conductance and leaf water potential showed a steep decrease together with the induction of stress related metabolism, e.g. up-regulation of proline and GABA metabolism and stress related sugars, and the down-regulation of developmental processes. Later, progressive soil drying was associated with an incremental contribution of Ca²⁺ and sucrose to the osmotic adjustment concomitant with the initiation of leaf shedding. Last, towards harvest under progressive stress conditions following leaf shedding, incremental changes in leaf water potential were measured, while the magnitude of perturbation in leaf metabolism lessened.

CONCLUSIONS

The data present evidence that over time grapevine acclimation to water stress diversifies in temporal responses encompassing the alteration of central metabolism and gene expression, osmotic adjustments and reduction in leaf area. Together these processes mitigate leaf water stress and aid in maintaining the berry-ripening program.

New frontier: cancer pain management clinical fellowship

Cancer pain is a multi-dimensional experience, varies from person to person both physically and psycho-socially, and impacts all aspects of the patients' quality of life. Majority of patients with an advanced or metastatic cancer will experience pain. It is estimated that as many as half of cancer patients are under-treated and as many as 20% experience pain refractory to the conventional WHO ladder of pain management. The McGill University Health Centre (MUHC) Cancer Pain Clinic (CPC) was created to meet the needs of those patients with a diagnosis of cancer whose pain had become a main symptom and those who failed to respond to conventional treatment. The clinic offers a unique interdisciplinary approach with a core team that includes an anesthesiologist, a palliative care physician, a radiation oncologist, a nurse clinician specialist in oncology and palliative care, and, recently, also an interventional radiologist. A cancer pain clinical fellowship was offered for the first time in July 2016. It provides intense training in the classification, epidemiology, pathophysiology, and treatment of cancer pain. Through our education program, the fellow learns to appreciate, weigh, and respond to the full spectrum of factors influencing a specific patient's condition and to develop a tailor-made care plan. To our knowledge, it is the only fellowship program in existence that focuses exclusively on cancer pain. We see it as a beacon and hope that our graduate fellows become professional leaders with a quest not only to provide the best possible care but also to raise awareness of the humanitarian need to control cancer pain.

[NEUROSURGICAL INTERVENTIONS FOR INTRACTABLE ONCOLOGICAL PAIN]

Pain is one of the most common symptoms among cancer patients, and particularly in those who suffer from metastatic or terminal disease. There is great importance in delivering good pain management to these patients in order to alleviate their suffering, improve their functional status and their overall quality of life. In most cases, pain management is based on pharmacotherapy with opioids and other medications. However, there are selected patients for whom pharmacotherapy does not achieve acceptable pain relief or is associated with marked side effects. These patients, who suffer from refractory cancer pain, may benefit from neurosurgical procedures selectively intervening in different locations along the pain signaling pathways. This article summarizes several of these neurosurgical procedures: percutaneous cordotomy for unilateral pain, punctuate midline myelotomy for visceral pain and stereotactic cingulotomy for diffuse pain syndromes. This article demonstrates the use of careful patient selection by an interdisciplinary team which is critical for the success of these procedures. The team consists of palliative care specialists, pain specialists and a neurosurgeon. These neurosurgical interventions are presented through representative clinical cases, followed by a discussion of the clinical considerations that guided the choice of the therapeutic approach for each case.

Iso/Anisohydry: A Plant-Environment Interaction Rather Than a Simple Hydraulic Trait

Plants are frequently classified as isohydric or anisohydric in an attempt to portray their water relations strategy or ecological niche. However, despite the popularity of the iso/anisohydric classification, the underlying biology remains unclear. We use here a simple hydraulic model and the extensive literature on grapevine hydraulics to illustrate that the iso/anisohydric classification of a plant depends on the definition used and the environment in which it is grown, rather than describing an intrinsic property of the plant itself. We argue that abandoning the iso/anisohydric terminology and returning to a more fundamental hydraulic framework would provide a stronger foundation for species comparisons and ecological predictions.