The effect of fatty infiltration, revision surgery, and sex on lumbar multifidus passive mechanical properties.

Purpose: Previous research has demonstrated increased stiffness in the multifidus muscle compared to other paraspinal muscles at the fiber bundle level. We aimed to compare single fiber and fiber bundle passive mechanical properties of multifidus muscle: (1) in 40 patients undergoing primary versus revision surgery and (2) in muscle with mild versus severe fatty infiltration. Methods: The degree of muscle fatty infiltration was graded using the patients' spine magnetic resonance images. Average single fiber and fiber bundle passive mechanical properties across three tests were compared between primary (N = 30) and revision (N = 10) surgery status, between mild and severe fatty infiltration levels, between sexes, and with age from passive stress-strain tests of excised multifidus muscle intraoperative biopsies. Results: At the single fiber level, elastic modulus was unaffected by degree of fatty infiltration or surgery status. Female sex (p = 0.001) and younger age (p = 0.04) were associated with lower multifidus fiber elastic modulus. At the fiber bundle level, which includes connective tissue around fibers, severe fatty infiltration (p = 0.01) and younger age (p = 0.06) were associated with lower elastic modulus. Primary surgery also demonstrated a moderate, but non-significant effect for lower elastic modulus (p = 0.10). Conclusions: Our results demonstrate that female sex is the primary driver for reduced single fiber elastic modulus of the multifidus, while severity of fatty infiltration is the primary driver for reduced elastic modulus at the level of the fiber bundle in individuals with lumbar spine pathology.

PET/MR of pediatric bone tumors: what the radiologist needs to know.

Integrated 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) positron emission tomography (PET)/magnetic resonance (MR) imaging can provide "one stop" local tumor and whole-body staging in one session, thereby streamlining imaging evaluations and avoiding duplicate anesthesia in young children. 18F-FDG PET/MR scans have the benefit of lower radiation, superior soft tissue contrast, and increased patient convenience compared to 18F-FDG PET/computerized tomography scans. This article reviews the 18F-FDG PET/MR imaging technique, reporting requirements, and imaging characteristics of the most common pediatric bone tumors, including osteosarcoma, Ewing sarcoma, primary bone lymphoma, bone and bone marrow metastases, and Langerhans cell histiocytosis.

Factors impacting adherence to an exercise-based physical therapy program for individuals with low back pain.

BACKGROUND/OBJECTIVE: Exercise-based rehabilitation is a conservative management approach for individuals with low back pain. However, adherence rates for conservative management are often low and the reasons for this are not well described. The objective of this study was to evaluate predictors of adherence and patient-reported reasons for non-adherence after ceasing a supervised exercise-based rehabilitation program in individuals with low back pain. DESIGN: Retrospective observational study. METHODS: Data was retrospectively analyzed from 5 rehabilitation clinics utilizing a standardized exercise-based rehabilitation program. Baseline demographics, diagnosis and symptom specific features, visit number, and discontinuation profiles were quantified for 2,243 patients who underwent the program. RESULTS: Forty-three percent (43%) of participants were adherent to the program, with the majority (31.7%) discontinuing treatment prior to completion due to logistic and accessibility issues. Another 13.2% discontinued prior to the prescribed duration due to clinically significant improvements in pain and/or disability without formal discharge evaluation, whereas 8.3% did not continue due to lack of improvement. Finally, 6.0% were discharged for related and unrelated medical reasons including surgery. Individuals diagnosed with disc pathology were most likely to be adherent to the program. LIMITATIONS: This study was a retrospective chart review with missing data for some variables. Future studies with a prospective design would increase quality of evidence. CONCLUSIONS: The majority of individuals prescribed an in-clinic exercise-based rehabilitation program are non-adherent. Patient diagnosis was the most important predictor of adherence. For those who were not adherent, important barriers include personal issues, insufficient insurance authorization and lack of geographic accessibility.

Immediate Effects of a Continuous Peripheral Nerve Block on Postamputation Phantom and Residual Limb Pain: Secondary Outcomes From a Multicenter Randomized Controlled Clinical Trial.

BACKGROUND: We recently reported that a 6-day continuous peripheral nerve block reduced established postamputation phantom pain 3 weeks after treatment ended. However, the immediate effects of perineural infusion (secondary outcomes) have yet to be reported. METHODS: Participants from 5 enrolling academic centers with an upper or lower limb amputation and established phantom pain received a single-injection ropivacaine peripheral nerve block(s) and perineural catheter insertion(s). They were subsequently randomized to receive a 6-day ambulatory perineural infusion of either ropivacaine 0.5% or normal saline in a double-masked fashion. Participants were contacted by telephone 1, 7, 14, 21, and 28 days after the infusion started, with pain measured using the Numeric Rating Scale. Treatment effects were assessed using the Wilcoxon rank-sum test at each time point. Adjusting for 4 time points (days 1, 7, 14, and 21), P < .0125 was deemed statistically significant. Significance at 28 days was reported using methods from the original, previously published article. RESULTS: Pretreatment average phantom and residual pain scores were balanced between the groups. The day after infusion initiation (day 1), average phantom, and residual limb pain intensity was lower in patients receiving local anesthetic (n = 71) versus placebo (n = 73): median [quartiles] of 0 [0-2.5] vs 3.3 [0-5.0], median difference (98.75% confidence interval [CI]) of -1.0 (-3.0 to 0) for phantom pain (P = .001) and 0 [0-0] vs 0 [0-4.3], and median difference 0.0 (-2.0 to 0.0) for residual limb pain (P < .001). Pain's interference with physical and emotional functioning as measured with the interference domain of the Brief Pain Inventory improved during the infusion on day 1 for patients receiving local anesthetic versus placebo: 0 [0-10] vs 10 [0-40], median difference (98.75% CI) of 0.0 (-16.0 to 0.0), P = .002. Following infusion discontinuation (day 6), a few differences were found between the active and placebo treatment groups between days 7 and 21. In general, sample medians for average phantom and residual limb pain scores gradually increased after catheter removal for both treatments, but to a greater degree in the control group until day 28, at which time the differences between the groups returned to statistical significance. CONCLUSIONS: This secondary analysis suggests that a continuous peripheral nerve block decreases phantom and residual limb pain during the infusion, although few improvements were again detected until day 28, 3 weeks following catheter removal.

Ambulatory continuous peripheral nerve blocks to treat postamputation phantom limb pain: a multicenter, randomized, quadruple-masked, placebo-controlled clinical trial.

Phantom limb pain is thought to be sustained by reentrant neural pathways, which provoke dysfunctional reorganization in the somatosensory cortex. We hypothesized that disrupting reentrant pathways with a 6-day-long continuous peripheral nerve block reduces phantom pain 4 weeks after treatment. We enrolled patients who had an upper- or lower-limb amputation and established phantom pain. Each was randomized to receive a 6-day perineural infusion of either ropivacaine or normal saline. The primary outcome was the average phantom pain severity as measured with a Numeric Rating Scale (0-10) at 4 weeks, after which an optional crossover treatment was offered within the following 0 to 12 weeks. Pretreatment pain scores were similar in both groups, with a median (interquartile range) of 5.0 (4.0, 7.0) for each. After 4 weeks, average phantom limb pain intensity was a mean (SD) of 3.0 (2.9) in patients given local anesthetic vs 4.5 (2.6) in those given placebo (difference [95% confidence interval] 1.3 [0.4, 2.2], P = 0.003). Patients given local anesthetic had improved global impression of change and less pain-induced physical and emotional dysfunction, but did not differ on depression scores. For subjects who received only the first infusion (no self-selected crossover), the median decrease in phantom limb pain at 6 months for treated subjects was 3.0 (0, 5.0) vs 1.5 (0, 5.0) for the placebo group; there seemed to be little residual benefit at 12 months. We conclude that a 6-day continuous peripheral nerve block reduces phantom limb pain as well as physical and emotional dysfunction for at least 1 month.

Acquired Thoracic Fistulas.

Fistulas are abnormal connections between 2 epithelial-lined structures. Thoracic fistulas may result from nonanatomic communications between spaces within the thorax, such as the lung, tracheobronchial tree, pleural space, and mediastinal structures, or between thoracic spaces and extrathoracic structures, such as the gastrointestinal tract. Furthermore, thoracic fistulas may result in communication between thoracic spaces and the spine or vascular structures. Potential causes include trauma, infection, neoplasm, surgical intervention, or medical syndromes. In this article, we discuss various acquired thoracic fistulas and their potential causes, key multimodality imaging manifestations, and clinical significance.

Regional differences between superficial and deep lumbar multifidus in patients with chronic lumbar spine pathology.

BACKGROUND: Due to its unique arrangement, the deep and superficial fibers of the multifidus may have differential roles for maintaining spine stabilization and lumbar posture; the superficial multifidus is responsible for lumbar extension and the deep multifidus for intersegmental stability. In patients with chronic lumbar spine pathology, muscle activation patterns have been shown to be attenuated or delayed in the deep, but not superficial, multifidus. This has been interpreted as pain differentially influencing the deep region. However, it is unclear if degenerative changes affecting the composition and function of the multifidus differs between the superficial and deep regions, an alternative explanation for these electrophysiological changes. Therefore, the goal of this study was to investigate macrostructural and microstructural differences between the superficial and deep regions of the multifidus muscle in patients with lumbar spine pathology. METHODS: In 16 patients undergoing lumbar spinal surgery for degenerative conditions, multifidus biopsies were acquired at two distinct locations: 1) the most superficial portion of muscle adjacent to the spinous process and 2) approximately 1 cm lateral to the spinous process and deeper at the spinolaminar border of the affected vertebral level. Structural features related to muscle function were histologically compared between these superficial and deep regions, including tissue composition, fat fraction, fiber cross sectional area, fiber type, regeneration, degeneration, vascularity and inflammation. RESULTS: No significant differences in fat signal fraction, muscle area, fiber cross sectional area, muscle regeneration, muscle degeneration, or vascularization were found between the superficial and deep regions of the multifidus. Total collagen content between the two regions was the same. However, the superficial region of the multifidus was found to have less loose and more dense collagen than the deep region. CONCLUSIONS: The results of our study did not support that the deep region of the multifidus is more degenerated in patients with lumbar spine pathology, as gross degenerative changes in muscle microstructure and macrostructure were the same in the superficial and deep regions of the multifidus. In these patients, the multifidus is not protected in order to maintain mobility and structural stability of the spine.

The effect of high-intensity resistance exercise on lumbar musculature in patients with low back pain: a preliminary study.

BACKGROUND: Muscle atrophy and fatty infiltration of the lumbar extensors is associated with LBP. Exercise-based rehabilitation targets strengthening these muscles, but few studies show consistent changes in muscle quality with standard-of-care rehabilitation. The goal of this study was to assess the effect of high-intensity resistance exercise on lumbar extensor muscle size (cross sectional area) and quality (fat fraction) in individuals with low back pain (LBP). METHODS: Fourteen patients with LBP were recruited from a local rehabilitation clinic. Patients underwent MRI scanning before and after a standardized 10-week high-intensity machine-based, resistance exercise program. Patient pain, disability, anxiety/depression, satisfaction, strength, and range of motion was compared pre- and post-rehabilitation using analysis of covariance (covariates: age, gender). Exercise-induced changes in MRI, and patient functional outcome measures were correlated using Pearson's correlation test. RESULTS: No significant differences were found in muscle size or fatty infiltration of the lumbar extensors over the course of rehabilitation (p > 0.31). However, patients reported reduced pain (p = 0.002) and were stronger (p = 0.03) at the conclusion of the program. Improvements in muscle size and quality for both multifidus and erector spinae correlated with improvements in disability, anxiety/depression, and strength. CONCLUSION: While average muscle size and fatty infiltration levels did not change with high-intensity exercise, the results suggest that a subgroup of patients who demonstrate improvements in muscle health demonstrate the largest functional improvements. Future research is needed to identify which patients are most likely to respond to this type of treatment.

Continuous Popliteal-Sciatic Blocks for Postoperative Analgesia: Traditional Proximal Catheter Insertion Superficial to the Paraneural Sheath Versus a New Distal Insertion Site Deep to the Paraneural Sheath.

We tested the hypothesis that during a continuous popliteal-sciatic nerve block, postoperative analgesia is improved with the catheter insertion point "deep" to the paraneural sheath immediately distal to the bifurcation between the tibial and common peroneal branches, compared with the traditional approach "superficial" to the paraneural sheath proximal to the bifurcation. The needle tip location was determined to be accurately located with a fluid bolus visualized with ultrasound; however, catheters were subsequently inserted without a similar fluid injection and visualization protocol (visualized air injection was permitted and usually implemented, but not required per protocol). The average pain (0-10 scale) the morning after surgery for subjects with a catheter inserted at the proximal subparaneural location (n = 31) was a median (interquartile) of 1.5 (0.0-3.5) vs 1.5 (0.0-4.0) for subjects with a catheter inserted at the distal supraparaneural location (n = 32; P = .927). Secondary outcomes were similarly negative.

Cost-effectiveness of Intraoperative MRI for Treatment of High-Grade Gliomas.

Background Intraoperative MRI has been shown to improve gross-total resection of high-grade glioma. However, to the knowledge of the authors, the cost-effectiveness of intraoperative MRI has not been established. Purpose To construct a clinical decision analysis model for assessing intraoperative MRI in the treatment of high-grade glioma. Materials and Methods An integrated five-state microsimulation model was constructed to follow patients with high-grade glioma. One-hundred-thousand patients treated with intraoperative MRI were compared with 100 000 patients who were treated without intraoperative MRI from initial resection and debulking until death (median age at initial resection, 55 years). After the operation and treatment of complications, patients existed in one of three health states: progression-free survival (PFS), progressive disease, or dead. Patients with recurrence were offered up to two repeated resections. PFS, valuation of health states (utility values), probabilities, and costs were obtained from randomized controlled trials whenever possible. Otherwise, national databases, registries, and nonrandomized trials were used. Uncertainty in model inputs was assessed by using deterministic and probabilistic sensitivity analyses. A health care perspective was used for this analysis. A willingness-to-pay threshold of $100 000 per quality-adjusted life year (QALY) gained was used to determine cost efficacy. Results Intraoperative MRI yielded an incremental benefit of 0.18 QALYs (1.34 QALYs with intraoperative MRI vs 1.16 QALYs without) at an incremental cost of $13 447 ($176 460 with intraoperative MRI vs $163 013 without) in microsimulation modeling, resulting in an incremental cost-effectiveness ratio of $76 442 per QALY. Because of parameter distributions, probabilistic sensitivity analysis demonstrated that intraoperative MRI had a 99.5% chance of cost-effectiveness at a willingness-to-pay threshold of $100 000 per QALY. Conclusion Intraoperative MRI is likely to be a cost-effective modality in the treatment of high-grade glioma. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Bettmann in this issue.

The association of neuraxial versus general anesthesia with inpatient admission following arthroscopic knee surgery.

STUDY OBJECTIVE: Arthroscopic knee procedures are increasingly being performed in an outpatient setting. Appropriate intraoperative anesthesia is vital to prevent complications such as unanticipated hospital admission. We examined differences in complications between general (GA) vs neuraxial anesthesia (NA) as the primary anesthetic for patients undergoing arthroscopic knee procedures. DESIGN: This was a retrospective cohort study. We queried the National Surgical Quality Improvement Program for arthroscopic knee procedures performed between 2007 and 2016. We compared postoperative complication rates between propensity-matched cohorts (NA vs GA). The anesthesia groups were matched based on age, race, BMI, gender, diabetes, smoking history, COPD, CHF, functional status, HTN, ASA class, steroid use, bleeding disorder history, and readmission status. Univariable and multivariable logistic regression were used to compare factors associated with inpatient admission - defined as hospital length of stay >1 day. PATIENTS: A total of 57,494 patients were included - 55,257 GA and 2237 NA patients. MAIN RESULTS: Among the matched cohorts, NA patients were significantly more likely to be admitted to the hospital postoperatively (p < 0.001). Neuraxial anesthesia (OR 5.93, 95% CI 4.90-7.21) use was also significant in the final multivariable regression model for inpatient admission. Additional significant predictors for inpatient admission included history of bleeding disorder (OR 5.44, 95% CI 2.14-12.76), Asian race (OR 6.47, 95% CI 4.90-8.56), COPD (OR 3.10, 95% CI 1.94-4.82), diabetes (OR 1.90, 95% CI 1.43-2.49), and increased operation time (OR 3.01, 95% CI 2.69-3.37). CONCLUSIONS: NA was significantly associated with inpatient admission following knee arthroscopy. Further research should focus on examining the reason for this association and methods to reduce inpatient admission for patients undergoing arthroscopic knee procedures using neuraxial anesthesia.

Postoperative outcomes with neuraxial versus general anesthesia in bilateral total hip arthroplasty.

STUDY OBJECTIVE: Current evidence remains limited on the postoperative outcomes of neuraxial (NA) versus general anesthesia (GA) as primary anesthesia type in patients receiving simultaneous bilateral total hip arthroplasty (BTHA). We aimed to evaluate the rates of postoperative outcomes among patients receiving NA versus GA for BTHA. DESIGN: Retrospective cohort study. SETTING: Multi-institutional. PATIENTS: A total of 798 patients undergoing BTHA with 519 and 279 who received GA and NA, respectively. We used the American College of Surgeons - National Surgical Quality Improvement Program database for years 2007 to 2016. INTERVENTIONS: Patients undergoing BTHA. MEASUREMENTS: We propensity-score matched on demographic factors and comorbid conditions to compare rates of postoperative outcomes among cohorts (NA versus GA). We performed Pearson chi-square and Wilcoxon rank sum test to compare NA versus GA cohorts. MAIN RESULTS: The final analysis included 798 BTHA patients, of which 35% received NA as the primary anesthetic. The median age was 58 years old and 50.8% were female. The rate of perioperative transfusion in the NA and GA group were 20.1% and 29.0%, respectively (p = 0.02). There were no significant differences in the rate of postoperative outcomes between patients receiving NA versus GA as their primary anesthesia type (Bonferroni corrected p < 0.006 was considered statistically significant). CONCLUSION: Our study showed no significant differences in postoperative outcomes between NA versus GA following BTHA. Further studies are needed to investigate outcomes among this surgical population.

Methodological considerations in region of interest definitions for paraspinal muscles in axial MRIs of the lumbar spine.

BACKGROUND: Magnetic Resonance Imaging (MRI) is commonly used to assess the health of the lumbar spine and supporting structures. Studies have suggested that fatty infiltration of the posterior lumbar muscles is important in predicting responses to treatment for low back pain. However, methodological differences exist in defining the region of interest (ROI) of a muscle, which limits the ability to compare data between studies. The purpose of this study was to determine reliability and systematic differences within and between two commonly utilized methodologies for ROI definitions of lumbar paraspinal muscle. METHODS: T2-weighted MRIs of the mid-L4 vertebrae from 37 patients with low back pain who were scheduled for lumbar spine surgery were included from a hospital database. Fatty infiltration for these patients ranged from low to high, based on Kjaer criteria. Two methods were used to define ROI: 1) segmentation of the multifidus and erector spinae based on fascial planes including epimuscular fat, and 2) segmentation of the multifidus and erector spinae based on visible muscle boundaries, which did not include epimuscular fat. Total cross sectional area (tCSA), fat signal fraction (FSF), muscle cross sectional area, and fat cross sectional area were measured. Degree of agreement between raters for each parameter was assessed using intra-class correlation coefficients (ICC) and area fraction of overlapping voxels. RESULTS: Excellent inter-rater agreement (ICC > 0.75) was observed for all measures for both methods. There was no significant difference between area fraction overlap of ROIs between methods. Method 1 demonstrated a greater tCSA for both the erector spinae (14-15%, p < 0.001) and multifidus (4%, p < 0.016) but a greater FSF only for the erector spinae (11-13%, p < 0.001). CONCLUSION: The two methods of defining lumbar spine muscle ROIs demonstrated excellent inter-rater reliability, although significant differences exist as method 1 showed larger CSA and FSF values compared to method 2. The results of this study confirm the validity of using either method to measure lumbar paraspinal musculature, and that method should be selected based on the primary outcome variables of interest.

Proximal Versus Distal Continuous Adductor Canal Blocks: Does Varying Perineural Catheter Location Influence Analgesia? A Randomized, Subject-Masked, Controlled Clinical Trial.

BACKGROUND: A continuous adductor canal block provides analgesia after surgical procedures of the knee. Recent neuroanatomic descriptions of the thigh and knee led us to speculate that local anesthetic deposited in the distal thigh close to the adductor hiatus would provide superior analgesia compared to a more proximal catheter location. We therefore tested the hypothesis that during a continuous adductor canal nerve block, postoperative analgesia would be improved by placing the perineural catheter tip 2-3 cm cephalad to where the femoral artery descends posteriorly to the adductor hiatus (distal location) compared to a more proximal location at the midpoint between the anterior superior iliac spine and the superior border of the patella (proximal location). METHODS: Preoperatively, subjects undergoing total knee arthroplasty received an ultrasound-guided perineural catheter inserted either in the proximal or distal location within the adductor canal in a randomized, subject-masked fashion. Subjects received a single injection of lidocaine 2% via the catheter preoperatively, followed by an infusion of ropivacaine 0.2% (8 mL/h basal, 4 mL bolus, 30 minutes lockout) for the study duration. After joint closure, the surgeon infiltrated the entire joint using 30 mL of ropivacaine (0.5%), ketorolac (30 mg), epinephrine (5 µg/mL), and tranexamic acid (2 g). The primary end point was the median level of pain as measured on a numeric rating scale (NRS) during the time period of 8:00 AM to 12:00 PM the day after surgery. RESULTS: For the primary end point, the NRS of subjects with a catheter inserted at the proximal location (n = 24) was a median (10th, 25th-75th, 90th quartiles) of 0.5 (0.0, 0.0-3.2, 5.0) vs 3.0 (0.0, 2.0-5.4, 7.8) for subjects with a catheter inserted in the distal location (n = 26; P = .011). Median and maximum NRSs were lower in the proximal group at all other time points, but these differences did not reach statistical significance. There were no clinically relevant or statistically significant differences between the treatment groups for any other secondary end point, including opioid consumption and ambulation distance. CONCLUSIONS: For continuous adductor canal blocks accompanied by intraoperative periarticular local anesthetic infiltration, analgesia the day after knee arthroplasty is improved with a catheter inserted at the level of the midpoint between the anterior superior iliac spine and the superior border of the patella compared with a more distal insertion closer to the adductor hiatus.

Treatment of Post-Latissimus Dorsi Flap Breast Reconstruction Pain With Continuous Paravertebral Nerve Blocks: A Retrospective Review.

OBJECTIVES: The addition of a perioperative continuous paravertebral nerve block (cPVB) to a single-injection thoracic paravertebral nerve block (tPVB) has demonstrated improved analgesia in breast surgery. However, its use following isolated post-mastectomy reconstruction using a latissimus dorsi flap (LDF) has not previously been examined. METHODS: We performed a retrospective review of patients who underwent salvage breast reconstruction with a unilateral LDF by a single surgeon. Preoperatively, all patients received a single-injection tPVB with 0.5% ropivacaine. Additionally, patients had the option for catheter placement to receive a continuous 0.2% ropivacaine infusion with intermittent boluses. Infusions commenced in the recovery room and the catheters were removed on the morning of discharge. The primary endpoint was the mean pain numeric rating scale (NRS) scores for the 24-hour period beginning at 7:00 on post-operative day 1. RESULTS: A total of 22 patients were included in this study (11-cPVB and 11-tPVB). The mean NRS pain score of cPVB patients (3.5 (standard deviation (SD) 1.8) was lower than that of the single-injection tPVB patients (4.4 (SD 2.1), however this difference was not statistically significant (P = 0.31). The length of hospital stay and opioid use was not statistically different between groups. CONCLUSIONS: Patients receiving a cPVB in addition to tPVB after LDF reconstruction experienced similar pain to those receiving tPVB alone. A larger, randomized clinical trial is warranted to fully determine the benefits of using cPVB in addition to tPVB for this procedure.

Superior Efficacy of Gross Total Resection in Anaplastic Astrocytoma Patients Relative to Glioblastoma Patients.

INTRODUCTION: Because of their relative rarity, anaplastic astrocytomas (AAs) often are grouped with glioblastomas in clinical treatment paradigms. There are reasons, however, to expect that the therapeutic response of AAs may differ from those of glioblastoma. Here, we examined the clinical benefit of gross total resection (GTR) in AA relative to glioblastoma patients. METHODS: Using the Surveillance, Epidemiology and End Results database, we identified 2755 patients with AA and patients with 21,962 glioblastoma between 1999 and 2010. Surgical resection was defined as GTR, subtotal resection (STR), biopsy only, or no resection. Kaplan-Meier curves and multivariate Cox regression were used to assess the association between GTR and survival. RESULTS: The hazard of dying from the AA was reduced in GTR patients by 40% relative to STR patients. This reduction is 59% greater than that observed in glioblastoma where GTR was associated only with a 24% reduction relative to STR (P < 0.0001). The median survival for patients with AA who underwent GTR and subtotal resection were 64 and 24 months, respectively. For glioblastoma patients, the corresponding numbers for median survival were 13 and 9 months, respectively. The survival benefit of GTR in patients with AA was particularly notable in patient age < 50, where the median survival was not reached during the study period. CONCLUSIONS: The Surveillance, Epidemiology and End Results data suggest that survival benefit associated with GTR was greater for patients with AA relative to glioblastoma patients, particularly for patients < age 50.

Gamma band activity and the P3 reflect post-perceptual processes, not visual awareness.

A primary goal in cognitive neuroscience is to identify neural correlates of conscious perception (NCC). By contrasting conditions in which subjects are aware versus unaware of identical visual stimuli, a number of candidate NCCs have emerged; among them are induced gamma band activity in the EEG and the P3 event-related potential. In most previous studies, however, the critical stimuli were always directly relevant to the subjects' task, such that aware versus unaware contrasts may well have included differences in post-perceptual processing in addition to differences in conscious perception per se. Here, in a series of EEG experiments, visual awareness and task relevance were manipulated independently. Induced gamma activity and the P3 were absent for task-irrelevant stimuli regardless of whether subjects were aware of such stimuli. For task-relevant stimuli, gamma and the P3 were robust and dissociable, indicating that each reflects distinct post-perceptual processes necessary for carrying-out the task but not for consciously perceiving the stimuli. Overall, this pattern of results challenges a number of previous proposals linking gamma band activity and the P3 to conscious perception.

Spinal cord stimulators in an outpatient interventional neuroradiology practice.

PURPOSE: Spinal cord stimulation is a known modality for the treatment of chronic back and neck pain. Traditionally, spine surgeons and pain physicians perform the procedures. We report our experience in performing neuromodulation procedures in an outpatient interventional neuroradiology practice. METHODS: A retrospective analysis of medical records of all trial and permanent implantation patients over a period of 4 years was performed. 45 patients (32 men) of median age 47 years were included in the study. The primary diagnoses were 23 cases of failed back or neck surgery syndrome, 12 cases of spinal stenosis, 4 cases of axial pain, 3 cases with reflex sympathetic dystrophy, 1 case of peripheral vascular disease, 1 case of phantom limb and 1 case of post-concussion syndrome. RESULTS: Thirty-four trials were performed in an outpatient clinic while 11 trials were performed in hospital outpatient settings. Trial periods were 3-7 days. 27 patients (60%) who reported ≥50% pain relief underwent a permanent implantation. An interventional neuroradiologist performed 17 implantations, while spine surgeons performed 10 implantations. 23 implants were epidural (19 lumbar and 4 cervical) and four implants were subcutaneous. During the follow-up period, three patients had infections (13%) and required removal of the device and two cases (8%) reported lead migration. CONCLUSIONS: Neuromodulation procedures can be performed safely in an outpatient interventional radiology setting. Although the infection rate was relatively higher in this study population, the other complication rates and trial-to-implant ratio are similar to published data.