Search Results

You are looking at 1 - 10 of 20 items for

  • Author or Editor: Andrew I. Yang x
  • Refine by Access: all x
Clear All Modify Search
Restricted access

Multitarget deep brain stimulation for epilepsy

Andrew I. Yang, Faical Isbaine, Abdulrahman Alwaki, and Robert E. Gross

OBJECTIVE

Deep brain stimulation (DBS) is a rapidly growing surgical option for patients with drug-resistant epilepsy who are not candidates for resective/ablative surgery. Recent randomized controlled trials have demonstrated efficacy of DBS of the anterior nucleus of the thalamus (ANT), particularly in frontal or temporal epilepsy, whereas DBS of the centromedian (CM) nucleus appears to be most suitable in well-defined generalized epilepsy syndromes. At the authors’ institution, DBS candidates who did not fit the populations represented in these trials were managed with DBS of multiple distinct targets, which included ANT, CM, and less-studied nuclei—i.e., mediodorsal nucleus, pulvinar, and subthalamic nucleus. The goal of this study was to present the authors’ experience with these types of cases, and to motivate future investigations that can determine the long-term efficacy of multitarget DBS.

METHODS

This single-center retrospective study of adult patients with drug-resistant epilepsy who underwent multitarget DBS was performed to demonstrate the feasibility and safety of this approach, and to present seizure outcomes. Patients in this cohort had epilepsy with features that were difficult to treat with DBS of the ANT or CM nucleus alone, including multifocal/multilobar, diffuse-onset, and/or posterior-onset seizures; or both generalized and focal seizures.

RESULTS

Eight patients underwent DBS of 2–3 distinct thalamic/subthalamic nuclei. DBS was performed with 2 electrodes in each hemisphere. All leads in each patient were implanted with either frontal or parietal trajectories. There were no surgical complications. Among those with > 6 months of follow-up (n = 5; range 7–21 months), all patients were responders in terms of overall seizure frequency and/or convulsive seizure frequency (i.e., ≥ 50% reduction). Two patients had adverse stimulation effects, which resolved with further programming.

CONCLUSIONS

Multitarget DBS is a procedurally feasible and safe treatment strategy to maximize outcomes in patients with complex epilepsy. The authors highlight their approach to inform future studies that are sufficiently powered to assess its efficacy.

Restricted access

Pediatric spinal cord astrocytomas: a retrospective study of 348 patients from the SEER database

Andrew S. Luksik, Tomas Garzon-Muvdi, Wuyang Yang, Judy Huang, and George I. Jallo

OBJECTIVE

Intramedullary spinal cord tumors comprise 1%–10% of all childhood central nervous system neoplasms, with astrocytomas representing the most common subtype. Due to their rarity and poor prognosis, large population-based studies are needed to assess the epidemiology and survival risk factors associated with these tumors in the hope of improving outcome. The authors undertook this retrospective study to explore factors that may influence survival in pediatric patients with spinal cord astrocytomas.

METHODS

Utilizing the Surveillance, Epidemiology, and End Results (SEER) database, a prospective cancer registry, the authors retrospectively assessed survival in histologically confirmed, primary spinal cord astrocytomas in patients 21 years of age and younger. Survival was described with Kaplan-Meyer curves, and a multivariate regression analysis was used to assess the association of several variables with survival while controlling for confounding variables.

RESULTS

This analysis of 348 cases showed that age (hazard ratio [HR] 1.05, 95% CI 1.01–1.09, p = 0.017), nonwhite race (HR 1.74, 95% CI 1.11–2.74, p = 0.014), high-grade tumor status (HR 14.67, 95% CI 6.69–32.14, p < 0.001), distant or invasive extension of the tumor (HR 2.37, 95% CI 1.02–5.49, p = 0.046), and radiation therapy (HR 3.74, 95% CI 2.18–6.41, p < 0.001) were associated with decreased survival. Partial resection (HR 0.37, 95% CI 0.16–0.83, p = 0.017) and gross-total resection (HR 0.39, 95% CI 0.16–0.95, p = 0.039) were associated with improved survival.

CONCLUSIONS

Younger age appears to be protective, while high-grade tumors have a much worse prognosis. Early diagnosis and access to surgery appears necessary for improving outcomes, while radiation therapy has an unclear role. There is still much to learn about this disease in the hope of curing children with the misfortune of having one of these rare tumors.

Restricted access

Endoscopic versus microscopic microvascular decompression for trigeminal neuralgia: equivalent pain outcomes with possibly decreased postoperative headache after endoscopic surgery

John Y. K. Lee, John T. Pierce, Sukhmeet K. Sandhu, Dmitriy Petrov, and Andrew I. Yang

OBJECTIVE

Endoscopic surgery has revolutionized surgery of the ventral skull base but has not yet been widely adopted for use in the cerebellopontine angle. Given the relatively normal anatomy of the cerebellopontine angle in patients with trigeminal neuralgia (TN), the authors hypothesized that a fully endoscopic microvascular decompression (E-MVD) might provide pain outcomes equivalent to those of microscopic MVD (M-MVD) but with fewer complications.

METHODS

The authors conducted a single-institution, single-surgeon retrospective study with patients treated in the period of 2006–2013. Before surgery, all patients completed a questionnaire that included a validated multidimensional pain-outcome tool, the Penn Facial Pain Scale (PFPS, formerly known as Brief Pain Inventory–Facial), an 11-point scale that measures pain intensity, interference with general activities of daily living (ADLs), and facial-specific ADLs. Using a standardized script, independent research assistants conducted follow-up telephone interviews.

RESULTS

In total, 167 patients were available for follow-ups (66.5% female; 93 patients underwent M-MVD and 74 underwent E-MVD). Preoperative characteristics (i.e., TN classification, PFPS components, and medication use) were similar for the 2 surgical groups except for 2 variables. Patients in the M-MVD group had slightly higher incidence of V3 pain, and the 2 groups differed in the date of surgery and hence in the length of follow-up (2.4 years for the M-MVD group and 1.3 years for the E-MVD group, p < 0.05). There was a trend toward not finding neurovascular conflict at the time of surgery more frequently in the M-MVD than in the E-MVD group (11% vs 7%, p = 0.052). Internal neurolysis was more often performed in the E-MVD group (26% vs 7%, p = 0.001). The 2 groups did not significantly differ in the length of the MVD procedure (approximately 2 hours). Self-reported headaches at 1 month postoperatively were present in 21% of the patients in the M-MVD group versus 7% in the E-MVD group (p = 0.01). Pain outcomes at the most recent followup were equivalent, with patients reporting a 5- to 6-point (70%–80%) improvement in pain intensity, a 5-point (85%) improvement in pain interference with ADLs, and a 6-point (85%) improvement in interference with facial-specific ADLs. Actuarial freedom from pain recurrence was equivalent in the 2 groups, with 80% pain control at 3 years.

CONCLUSIONS

Both the fully endoscopic MVD and the conventional M-MVD appear to provide patients with equivalent pain outcomes. Complication rates were also similar between the groups, with the exception of the rate of headaches, which was significantly lower in the E-MVD group 1 month postoperatively.

Full access

Patterns of opioid use in patients with trigeminal neuralgia undergoing neurosurgery

Andrew I. Yang, Brendan J. McShane, Frederick L. Hitti, Sukhmeet K. Sandhu, H. Isaac Chen, and John Y. K. Lee

OBJECTIVE

First-line treatment for trigeminal neuralgia (TN) is pharmacological management using antiepileptic drugs (AEDs), e.g., carbamazepine (CBZ) and oxcarbazepine (OCBZ). Surgical intervention has been shown to be an effective and durable treatment for TN that is refractory to medical therapy. Despite the lack of evidence for efficacy in patients with TN, the authors hypothesized that patients with neuropathic facial pain are prescribed opioids at high rates, and that neurosurgical intervention may lead to a reduction in opioid use.

METHODS

This is a retrospective study of patients with facial pain seen by a single neurosurgeon. All patients completed a survey on pain medications, medical comorbidities, prior interventions for facial pain, and a validated pain outcome tool (the Penn Facial Pain Scale). Patients subsequently undergoing neurosurgical intervention completed a survey at the 1-month follow-up in the office, in addition to telephone interviews using a standardized script between 1 and 6 years after intervention. Univariate and multivariate logistic regression were used to predict opioid use.

RESULTS

The study cohort consisted of 309 patients (70% Burchiel type 1 TN [TN1], 18% Burchiel type 2 [TN2], 6% atypical facial pain [AFP], and 6% TN secondary to multiple sclerosis [TN-MS]). At initial presentation, 20% of patients were taking opioids. Of these patients, 55% were receiving concurrent opioid therapy with CBZ/OCBZ, and 84% were receiving concurrent therapy with at least one type of AED. Facial pain diagnosis (for diagnoses other than TN1, odds ratio [OR] 2.5, p = 0.01) and facial pain intensity at its worst (for each unit increase, OR 1.4, p = 0.005) were predictors of opioid use at baseline. Neurosurgical intervention led to a reduction in opioid use to 8% at long-term follow-up (p < 0.01, Fisher’s exact test; n = 154). Diagnosis (for diagnoses other than TN1, OR 4.7, p = 0.002) and postintervention reduction in pain at its worst (for each unit reduction, OR 0.8, p < 10−3) were predictors of opioid use at long-term follow-up. On subgroup analysis, patients with TN1 demonstrated a decrease in opioid use to 5% at long-term follow-up (p < 0.05, Fisher’s exact test), whereas patients with non-TN1 facial pain did not. In the nonsurgical group, there was no statistically significant decrease in opioid use at long-term follow-up (n = 81).

CONCLUSIONS

In spite of its high potential for abuse, opioid use, mostly as an adjunct to AEDs, is prevalent in patients with facial pain. Opportunities to curb opioid use in TN1 include earlier neurosurgical intervention.

Full access

Long-term outcomes following deep brain stimulation for Parkinson’s disease

Frederick L. Hitti, Ashwin G. Ramayya, Brendan J. McShane, Andrew I. Yang, Kerry A. Vaughan, and Gordon H. Baltuch

OBJECTIVE

Deep brain stimulation (DBS) is an effective treatment for several movement disorders, including Parkinson’s disease (PD). While this treatment has been available for decades, studies on long-term patient outcomes have been limited. Here, the authors examined survival and long-term outcomes of PD patients treated with DBS.

METHODS

The authors conducted a retrospective analysis using medical records of their patients to identify the first 400 consecutive patients who underwent DBS implantation at their institution from 1999 to 2007. The medical record was used to obtain baseline demographics and neurological status. The authors performed survival analyses using Kaplan-Meier estimation and multivariate regression using Cox proportional hazards modeling. Telephone surveys were used to determine long-term outcomes.

RESULTS

Demographics for the cohort of patients with PD (n = 320) were as follows: mean age of 61 years, 70% male, 27% of patients had at least 1 medical comorbidity (coronary artery disease, congestive heart failure, diabetes mellitus, atrial fibrillation, or deep vein thrombosis). Kaplan-Meier survival analysis on a subset of patients with at least 10 years of follow-up (n = 200) revealed a survival probability of 51% (mean age at death 73 years). Using multivariate regression, the authors found that age at implantation (HR 1.02, p = 0.01) and male sex (HR 1.42, p = 0.02) were predictive of reduced survival. Number of medical comorbidities was not significantly associated with survival (p > 0.5). Telephone surveys were completed by 40 surviving patients (mean age 55.1 ± 6.4 years, 72.5% male, 95% subthalamic nucleus DBS, mean follow-up 13.0 ± 1.7 years). Tremor responded best to DBS (72.5% of patients improved), while other motor symptoms remained stable. Ability to conduct activities of daily living (ADLs) remained stable (dressing, 78% of patients; running errands, 52.5% of patients) or worsened (preparing meals, 50% of patients). Patient satisfaction, however, remained high (92.5% happy with DBS, 95% would recommend DBS, and 75% felt it provided symptom control).

CONCLUSIONS

DBS for PD is associated with a 10-year survival rate of 51%. Survey data suggest that while DBS does not halt disease progression in PD, it provides durable symptomatic relief and allows many individuals to maintain ADLs over long-term follow-up greater than 10 years. Furthermore, patient satisfaction with DBS remains high at long-term follow-up.

Free access

Data-driven phenotyping of preoperative functional decline patterns in patients undergoing lumbar decompression and lumbar fusion using smartphone accelerometry

Hasan S. Ahmad, Shikha Singh, Kenneth Jiao, Gregory W. Basil, Andrew I. Yang, Michael Y. Wang, William C. Welch, and Jang W. Yoon

OBJECTIVE

Treatment of degenerative lumbar spine pathologies typically escalates to surgical intervention when symptoms begin to significantly impair patients’ functional status. Currently, surgeons rely on subjective patient assessments through patient-reported outcome measures to estimate the decline in patient wellness and quality of life. In this analysis, the authors sought to use smartphone-based accelerometry data to provide an objective, continuous measurement of physical activity that might aid in effective characterization of preoperative functional decline in different lumbar spine surgical indications.

METHODS

Up to 1 year of preoperative activity data (steps taken per day) from 14 patients who underwent lumbar decompression and 15 patients who underwent endoscopic lumbar fusion were retrospectively extracted from patient smartphones. A data-driven algorithm was constructed based on 10,585 unique activity data points to identify and characterize the functional decline of patients preceding surgical intervention. Algorithmic estimation of functional decline onset was compared with reported symptom onset in clinical documentation across patients who presented acutely (≤ 5 months of symptoms) or chronically (> 5 months of symptoms).

RESULTS

The newly created algorithm identified a statistically significant decrease in physical activity during measured periods of functional decline (p = 0.0020). To account for the distinct clinical presentation phenotypes of patients requiring lumbar decompression (71.4% acute and 28.6% chronic) and those requiring lumbar fusion (6.7% acute and 93.3% chronic), a variable threshold for detecting clinically significant reduced physical activity was implemented. The algorithm characterized functional decline (i.e., acute or chronic presentation) in patients who underwent lumbar decompression with 100% accuracy (sensitivity 100% and specificity 100%), while characterization of patients who underwent lumbar fusion was less effective (accuracy 26.7%, sensitivity 21.4%, and specificity 100%). Adopting a less-permissive detection threshold in patients who underwent lumbar fusion, which rendered the algorithm robust to minor fluctuations above or below the chronically decreased level of preoperative activity in most of those patients, increased functional decline classification accuracy of patients who underwent lumbar fusion to 66.7% (sensitivity 64.3% and specificity 100%).

CONCLUSIONS

In this study, the authors found that smartphone-based accelerometer data successfully characterized functional decline in patients with degenerative lumbar spine pathologies. The accuracy and sensitivity of functional decline detection were much lower when using non–surgery-specific detection thresholds, indicating the effectiveness of smartphone-based mobility analysis in characterizing the unique physical activity fingerprints of different lumbar surgical indications. The results of this study highlight the potential of using activity data to detect symptom onset and functional decline in patients, enabling earlier diagnosis and improved prognostication.

Restricted access

Defining the minimal clinically important difference in smartphone-based mobility after spine surgery: correlation of survey questionnaire to mobility data

Presented at the 2023 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Daksh Chauhan, Hasan S. Ahmad, Robert Subtirelu, Sai Mannam, Ryan Turlip, Kevin Bryan, Shreya Bathula, Yohannes Ghenbot, Andrew I. Yang, Michael Y. Wang, Gregory Basil, Zarina S. Ali, and Jang W. Yoon

OBJECTIVE

Patient-reported outcome measures (PROMs) are the gold standard for assessing postoperative outcomes in spine surgery. However, PROMs are also limited by the inherent subjectivity of self-reported qualitative data. Recent literature has highlighted the utility of patient mobility data streamed from smartphone accelerometers as an objective measure of functional outcomes and complement to traditional PROMs. Still, for activity-based data to supplement existing PROMs, they must be validated against current metrics. In this study, the authors assessed the relationships and concordance between longitudinal smartphone-based mobility data and PROMs.

METHODS

Patients receiving laminectomy (n = 21) or fusion (n = 10) between 2017 and 2022 were retrospectively included. Activity data (steps-per-day count) recorded in the Apple Health mobile application over a 2-year perioperative window were extracted and subsequently normalized to allow for intersubject comparison. PROMS, including the visual analog scale (VAS), Patient Reported Outcome Measurement Information System Pain Interference (PROMIS-PI), Oswestry Disability Index (ODI), and EQ-5D, collected at the preoperative and 6-week postoperative visits were retrospectively extracted from the electronic medical record. Correlations between PROMs and patient mobility were assessed and compared between patients who did and those who did not achieve the established minimal clinically important difference (MCID) for each measure.

RESULTS

A total of 31 patients receiving laminectomy (n = 21) or fusion (n = 10) were included. Change between preoperative and 6-week postoperative VAS and PROMIS-PI scores demonstrated moderate (r = −0.46) and strong (r = −0.74) inverse correlations, respectively, with changes in normalized steps-per-day count. In cohorts of patients who achieved PROMIS-PI MCID postoperatively, indicating subjective improvement in pain, there was a 0.784 standard deviation increase in normalized steps per day, representing a 56.5% improvement (p = 0.027). Patients who did achieve the MCID of improvement in either PROMIS-PI or VAS after surgery were more likely to experience an earlier sustained improvement in physical activity commensurate to or greater than their preoperative baseline (p = 2.98 × 10−18) than non-MCID patients.

CONCLUSIONS

This study demonstrates a strong correlation between changes in mobility data extracted from patient smartphones and changes in PROMs following spine surgery. Further elucidating this relationship will allow for more robust supplementation of existing spine outcome measure tools with analyzed objective activity data.

Restricted access

Cervical laminoplasty versus laminectomy and posterior cervical fusion for cervical myelopathy: propensity-matched analysis of 24-month outcomes from the Quality Outcomes Database

Presented at the 2023 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Eunice Yang, Praveen V. Mummaneni, Dean Chou, Mohamad Bydon, Erica F. Bisson, Christopher I. Shaffrey, Oren N. Gottfried, Anthony L. Asher, Domagoj Coric, Eric A. Potts, Kevin T. Foley, Michael Y. Wang, Kai-Ming Fu, Michael S. Virk, John J. Knightly, Scott Meyer, Paul Park, Cheerag D. Upadhyaya, Mark E. Shaffrey, Avery L. Buchholz, Luis M. Tumialán, Jay D. Turner, Giorgos D. Michalopoulos, Brandon A. Sherrod, Nitin Agarwal, Regis W. Haid Jr., and Andrew K. Chan

OBJECTIVE

Compared with laminectomy with posterior cervical fusion (PCF), cervical laminoplasty (CL) may result in different outcomes for those operated on for cervical spondylotic myelopathy (CSM). The aim of this study was to compare 24-month patient-reported outcomes (PROs) for laminoplasty versus PCF by using the Quality Outcomes Database (QOD) CSM data set.

METHODS

This was a retrospective study using an augmented data set from the prospectively collected QOD Registry Cervical Module. Patients undergoing laminoplasty or PCF for CSM were included. Using the nearest-neighbor method, the authors performed 1:1 propensity matching based on age, operated levels, and baseline modified Japanese Orthopaedic Association (mJOA) and visual analog scale (VAS) neck pain scores. The 24-month PROs, i.e., mJOA, Neck Disability Index (NDI), VAS neck pain, VAS arm pain, EQ-5D, EQ-VAS, and North American Spine Society (NASS) satisfaction scores, were compared. Only cases in the subaxial cervical region were included; those that crossed the cervicothoracic junction were excluded.

RESULTS

From the 1141 patients included in the QOD CSM data set who underwent anterior or posterior surgery for cervical myelopathy, 946 (82.9%) had 24 months of follow-up. Of these, 43 patients who underwent laminoplasty and 191 who underwent PCF met the inclusion criteria. After matching, the groups were similar for baseline characteristics, including operative levels (CL group: 4.0 ± 0.9 vs PCF group: 4.2 ± 1.1, p = 0.337) and baseline PROs (p > 0.05), except for a higher percentage involved in activities outside the home in the CL group (95.3% vs 81.4%, p = 0.044). The 24-month follow-up for the matched cohorts was similar (CL group: 88.4% vs PCF group: 83.7%, p = 0.534). Patients undergoing laminoplasty had significantly lower estimated blood loss (99.3 ± 91.7 mL vs 186.7 ± 142.7 mL, p = 0.003), decreased length of stay (3.0 ± 1.6 days vs 4.5 ± 3.3 days, p = 0.012), and a higher rate of routine discharge (88.4% vs 62.8%, p = 0.006). The CL cohort also demonstrated a higher rate of return to activities (47.2% vs 21.2%, p = 0.023) after 3 months. Laminoplasty was associated with a larger improvement in 24-month NDI score (−19.6 ± 18.9 vs −9.1 ± 21.9, p = 0.031). Otherwise, there were no 3- or 24-month differences in mJOA, mean NDI, VAS neck pain, VAS arm pain, EQ-5D, EQ-VAS, and distribution of NASS satisfaction scores (p > 0.05) between the cohorts.

CONCLUSIONS

Compared with PCF, laminoplasty was associated with decreased blood loss, decreased length of hospitalization, and higher rates of home discharge. At 3 months, laminoplasty was associated with a higher rate of return to baseline activities. At 24 months, laminoplasty was associated with greater improvements in neck disability. Otherwise, laminoplasty and PCF shared similar outcomes for functional status, pain, quality of life, and satisfaction. Laminoplasty and PCF achieved similar neck pain scores, suggesting that moderate preoperative neck pain may not necessarily be a contraindication for laminoplasty.

Open access

The relevance of biologically effective dose for pain relief and sensory dysfunction after Gamma Knife radiosurgery for trigeminal neuralgia: an 871-patient multicenter study

Ronald E. Warnick, Ian Paddick, David Mathieu, Elizabeth Adam, Christian Iorio-Morin, William Leduc, Andréanne Hamel, Sarah E. Johnson, Mohamad Bydon, Ajay Niranjan, L. Dade Lunsford, Zhishuo Wei, Kaitlin Waite, Shalini Jose, Selcuk Peker, Mustafa Yavuz Samanci, Ece Tek, Georgios Mantziaris, Stylianos Pikis, Jason P. Sheehan, Manjul Tripathi, Narendra Kumar, Juan Diego Alzate, Kenneth Bernstein, Peter Ahorukomeye, Varun R. Kshettry, Herwin Speckter, Wenceslao Hernandez, Dušan Urgošík, Roman Liščák, Andrew I. Yang, John Y. K. Lee, Samir Patel, Dorian M. Kusyk, Matthew J. Shepard, and Douglas Kondziolka

OBJECTIVE

Recent studies have suggested that biologically effective dose (BED) is an important correlate of pain relief and sensory dysfunction after Gamma Knife radiosurgery (GKRS) for trigeminal neuralgia (TN). The goal of this study was to determine if BED is superior to prescription dose in predicting outcomes in TN patients undergoing GKRS as a first procedure.

METHODS

This was a retrospective study of 871 patients with type 1 TN from 13 GKRS centers. Patient demographics, pain characteristics, treatment parameters, and outcomes were reviewed. BED was compared with prescription dose and other dosimetric factors for their predictive value.

RESULTS

The median age of the patients was 68 years, and 60% were female. Nearly 70% of patients experienced pain in the V2 and/or V3 dermatomes, predominantly on the right side (60%). Most patients had modified BNI Pain Intensity Scale grade IV or V pain (89.2%) and were taking 1 or 2 pain medications (74.1%). The median prescription dose was 80 Gy (range 62.5–95 Gy). The proximal trigeminal nerve was targeted in 77.9% of cases, and the median follow-up was 21 months (range 6–156 months). Initial pain relief (modified BNI Pain Intensity Scale grades I–IIIa) was noted in 81.8% of evaluable patients at a median of 30 days. Of 709 patients who achieved initial pain relief, 42.3% experienced at least one pain recurrence after GKRS at a median of 44 months, with 49.0% of these patients undergoing a second procedure. New-onset facial numbness occurred in 25.3% of patients after a median of 8 months. Age ≥ 63 years was associated with a higher probability of both initial pain relief and maintaining pain relief. A distal target location was associated with a higher probability of initial and long-term pain relief, but also a higher incidence of sensory dysfunction. BED ≥ 2100 Gy2.47 was predictive of pain relief at 30 days and 1 year for the distal target, whereas physical dose ≥ 85 Gy was significant for the proximal target, but the restricted range of BED values in this subgroup could be a confounding factor. A maximum brainstem point dose ≥ 29.5 Gy was associated with a higher probability of bothersome facial numbness.

CONCLUSIONS

BED and physical dose were both predictive of pain relief and could be used as treatment planning goals for distal and proximal targets, respectively, while considering maximum brainstem point dose < 29.5 Gy as a potential constraint for bothersome numbness.

Free access

Abstracts of the 2015 Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves Phoenix, Arizona • March 4–7, 2015