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Nishit Mummareddy, Michael C. Dewan, Michael R. Mercier, Robert P. Naftel, John C. Wellons III and Christopher M. Bonfield

OBJECTIVE

The authors aimed to provide an updated and consolidated report on the epidemiology, management, and functional outcome of cases of myelomeningocele (MMC) in patients with scoliosis.

METHODS

A comprehensive literature search was performed using MEDLINE, Embase, Google Scholar, and the Cochrane Database of Systematic Reviews on cases of MMC in patients with scoliosis between 1980 and 2016. The initial search yielded 670 reports. After removing duplicates and applying inclusion criteria, we included 32 full-text original articles in this study.

RESULTS

Pooled statistical analysis of the included articles revealed the prevalence of scoliosis in MMC patients to be 53% (95% CI 0.42–0.64). Slightly more females (56%) are affected with both MMC and scoliosis than males. Motor level appears to be a significant predictor of prevalence, but not severity, of scoliosis in MMC patients. Treatment options for these patients include tethered cord release (TCR) and fusion surgeries. Curvature improvement and stabilization after TCR may be limited to patients with milder (< 50°) curves. Meanwhile, more aggressive fusion procedures such as a combined anterior-posterior approach may result in more favorable long-term scoliosis correction, albeit with greater complication rates. Quality of life metrics including ambulatory status and sitting stability are influenced by motor level of the lesion as well as the degree of the scoliosis curvature.

CONCLUSIONS

Scoliosis is among the most common and challenging comorbidities from which patients with MMC suffer. Although important epidemiological and management trends are evident, larger, prospective studies are needed to discover ways to more accurately counsel and more optimally treat these patients.

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Michael D. Martin, Christopher M. Boxell and David G. Malone

Lumbar disc degeneration occurs because of a variety of factors and results in a multitude of conditions. Alterations in the vertebral endplate cause loss of disc nutrition and disc degeneration. Aging, apoptosis, abnormalities in collagen, vascular ingrowth, loads placed on the disc, and abnormal proteoglycan all contribute to disc degeneration. Some forms of disc degeneration lead to loss of height of the motion segment with concomitant changes in biomechanics of the segment. Disc herniation with radiculopathy and chronic discogenic pain are the result of this degenerative process.

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Alex J. Koefman, Melissa Licari, Michael Bynevelt and Christopher R. P. Lind

OBJECTIVE

An objective biomarker for pain is yet to be established. Functional MRI (fMRI) is a promising neuroimaging technique that may reveal an objective radiological biomarker. The purpose of this study was to evaluate fMRI technology in the setting of lumbosacral radiculopathy and discuss its application in revealing a biomarker for pain in the future.

METHODS

A prospective, within-participant control study was conducted. Twenty participants with painful lumbosacral radiculopathy from intervertebral disc pathology were recruited. Functional imaging of the brain was performed during a randomly generated series of nonprovocative and provocative straight leg raise maneuvers.

RESULTS

With a statistical threshold set at p < 0.000001, 3 areas showed significant blood oxygen level–dependent (BOLD) signal change: right superior frontal gyrus (x = 2, y = 13, z = 48, k = 29, Brodmann area 6 [BA6]), left supramarginal cortex (x = −37, y = −44, z = 33, k = 1084, BA40), and left parietal cortex (x = −19, y = −41, z = 63, k = 354, BA5). With a statistical threshold set at p < 0.0002, 2 structures showed significant BOLD signal change: right putamen (x = 29, y = −11, z = 6, k = 72) and bilateral thalami (right: x = 23, y = −11, z = 21, k = 29; x = 8, y = −11, z = 9, k = 274; and left: x = −28, y = −32, z = 6, k = 21).

CONCLUSIONS

The results in this study compare with those in previous studies and suggest that fMRI technology can provide an objective assessment of the pain experience.

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Christopher I. Shaffrey and Justin S. Smith

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Arjun S. Chandran, Michael Bynevelt and Christopher R. P. Lind

The subthalamic nucleus (STN) is one of the most important stereotactic targets in neurosurgery, and its accurate imaging is crucial. With improving MRI sequences there is impetus for direct targeting of the STN. High-quality, distortion-free images are paramount. Image reconstruction techniques appear to show the greatest promise in balancing the issue of geometrical distortion and STN edge detection. Existing spin echo- and susceptibility-based MRI sequences are compared with new image reconstruction methods. Quantitative susceptibility mapping is the most promising technique for stereotactic imaging of the STN.

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Christopher E. Mandigo, Prakash Sampath and Michael G. Kaiser

✓Posterior dynamic stabilization in the lumbar spine is performed in an attempt to reduce loading across the intervertebral disc for the purpose of relieving pain and limiting degeneration while preserving motion. The AccuFlex rod system (Globus Medical, Inc.), a first-generation device, achieves this by changing the properties of the rod within the Protex pedicle screw–based rigid rod system. Helical cuts that have been created in the standard 6.5-mm rod allow for a limited range of motion while providing a posterior tension band that relieves a significant amount of disc loading. The AccuFlex rod system has been approved by the Food and Drug Administration for single-level fusion when used in conjunction with an interbody graft. In a study involving 170 patients who underwent fusion surgery for back pain, the 54 who received the AccuFlex construct had statistically similar fusion rates and outcomes (as assessed by visual analog scale and Short Form-16 scores) when compared with 116 patients treated with rigid rod fixation after 1 year of follow up. Future clinical studies will examine and provide information regarding the impact of AccuFlex on the incidence of adjacent-level disease. Information gained through the clinical experience with AccuFlex will serve as a foundation for the development of a stand-alone dynamic construct.

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Michael J. Rauzzino, Christopher I. Shaffrey, James Wagner, Russ Nockels and Mark Abel

The indications for surgical intervention in patients with idiopathic scoliosis have been well defined. The goals of surgery are to achieve fusion and arrest progressive curvature while restoring normal coronal and sagittal balance. As first introduced by Harrington, posterior fusion, the gold standard of treatment, has a proven record of success. More recently, anterior techniques for performing fusion procedures via either a thoracotomy or a retroperitoneal approach have been popularized in attempts to achieve better correction of curvature, preserve motion segments, and avoid some of the complications of posterior fusion such as the development of the flat-back syndrome. Anterior instrumentation alone, although effective, can be kyphogenic and has been shown to be associated with complications such as pseudarthrosis and instrumentation failure. Performing a combined approach in patients with scoliosis and other deformities has become an increasingly popular procedure to achieve superior correction of deformity and to minimize later complications. Indications for a combined approach (usually consisting of anterior release, arthrodesis with or without use of instrumentation, and posterior segmental fusion) include: prevention of crankshaft phenomenon in juvenile or skeletally immature adolescents; correction of large curves (75°) or excessively rigid curves in skeletally mature or immature patients; correction of curves with large sagittal-plane deformities such as thoracic kyphosis (> 90°) or thoracic lordosis (> 20°); and correction of thoracolumbar curves that need to be fused to the sacrum. Surgery may be performed either in a staged proceedure or, more commonly, in a single sitting. The authors discuss techniques for combined surgery and complication avoidance.

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Michael J. Rauzzino, Christopher I. Shaffrey, Russ P. Nockels, Gregory C. Wiggins, Jack Rock and James Wagner

The authors report their experience with 42 patients in whom anterior lumbar fusion was performed using titanium cages as a versatile adjunct to treat a wide variety of spinal deformity and pathological conditions. These conditions included congenital, degenerative, iatrogenic, infectious, traumatic, and malignant disorders of the thoracolumbar spine. Fusion rates and complications are compared with data previously reported in the literature.

Between July 1996 and July 1999 the senior authors (C.I.S., R.P.N., and M.J.R.) treated 42 patients by means of a transabdominal extraperitoneal (13 cases) or an anterolateral extraperitoneal approach (29 cases), 51 vertebral levels were fused using titanium cages packed with autologous bone. All vertebrectomies (27 cases) were reconstructed using a Miami Moss titanium mesh cage and Kaneda instrumentation. Interbody fusion (15 cases) was performed with either the BAK titanium threaded interbody cage (in 13 patients) or a Miami Moss titanium mesh cage (in two patients). The average follow-up period was 14.3 months. Seventeen patients had sustained a thoracolumbar burst fracture, 12 patients presented with degenerative spinal disorders, six with metastatic tumor, four with spinal deformity (one congenital and three iatrogenic), and three patients presented with spinal infections. In five patients anterior lumbar interbody fusion (ALIF) was supplemented with posterior segmental fixation at the time of the initial procedure. Of the 51 vertebral levels treated, solid arthrodesis was achieved in 49, a 96% fusion rate. One case of pseudarthrosis occurred in the group treated with BAK cages; the diagnosis was made based on the patient's continued mechanical back pain after undergoing L4–5 ALIF. The patient was treated with supplemental posterior fixation, and successful fusion occurred uneventfully with resolution of her back pain. In the group in which vertebrectomy was performed there was one case of fusion failure in a patient with metastatic breast cancer who had undergone an L-3 corpectomy with placement of a mesh cage. Although her back pain was immediately resolved, she died of systemic disease 3 months after surgery and before fusion could occur.

Complications related to the anterior approach included two vascular injuries (two left common iliac vein lacerations); one injury to the sympathetic plexus; one case of superficial phlebitis; two cases of prolonged ileus (greater than 48 hours postoperatively); one anterior femoral cutaneous nerve palsy; and one superficial wound infection. No deaths were directly related to the surgical procedure. There were no cases of dural laceration and no nerve root injury. There were no cases of deep venous thrombosis, pulmonary embolus, retrograde ejaculation, abdominal hernia, bowel or ureteral injury, or deep wound infection. Fusion-related complications included an iliac crest hematoma and prolonged donor-site pain in one patient. There were no complications related to placement or migration of the cages, but there was one case of screw fracture of the Kaneda device that did not require revision.

The authors conclude that anterior lumbar fusion performed using titanium interbody or mesh cages, packed with autologous bone, is an effective, safe method to achieve fusion in a wide variety of pathological conditions of the thoracolumbar spine. The fusion rate of 96% compares favorably with results reported in the literature. The complication rate mirrors the low morbidity rate associated with the anterior approach. A detailed study of clinical outcomes is in progress. Patient selection and strategies for avoiding complication are discussed.

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Christopher S. Eddleman, Michael C. Hurley, Bernard R. Bendok and H. Hunt Batjer

Most cavernous carotid aneurysms (CCAs) are considered benign lesions, most often asymptomatic, and to have a natural history with a low risk of life-threatening complications. However, several conditions may exist in which treatment of these aneurysms should be considered. Several options are currently available regarding the management of CCAs with resultant good outcomes, namely expectant management, luminal preservation strategies with or without addressing the aneurysm directly, and Hunterian strategies with or without revascularization procedures. In this article, we discuss the sometimes difficult decision regarding whether to treat CCAs. We consider the natural history of several types of CCAs, the clinical presentation, the current modalities of CCA management and their outcomes to aid in the management of this heterogeneous group of cerebral aneurysms.

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Daniel J. Blizzard, Michael A. Gallizzi, Robert E. Isaacs and Christopher R. Brown

Lateral interbody fusion (LIF) via the retroperitoneal transpsoas approach is an increasingly popular, minimally invasive technique for interbody fusion in the thoracolumbar spine that avoids many of the complications of traditional anterior and transforaminal approaches. Renal vascular injury has been cited as a potential risk in LIF, but little has been documented in the literature regarding the etiology of this injury. The authors discuss a case of an intraoperative complication of renal artery injury during LIF. A 42-year-old woman underwent staged T12–L5 LIF in the left lateral decubitus position, and L5–S1 anterior lumbar interbody fusion, followed 3 days later by T12–S1 posterior instrumentation for idiopathic scoliosis with radiculopathy refractory to conservative management. After placement of the T12–L1 cage, the retractor was released and significant bleeding was encountered during its removal. Immediate consultation with the vascular team was obtained, and hemostasis was achieved with vascular clips. The patient was stabilized, and the remainder of the procedure was performed without complication. On postoperative CT imaging, the patient was found to have a supernumerary left renal artery with complete occlusion of the superior left renal artery, causing infarction of approximately 75% of the kidney. There was no increase in creatinine level immediately postoperatively or at the 3-month follow-up. Renal visceral and vascular injuries are known risks with LIF, with potentially devastating consequences. The retroperitoneal transpsoas approach for LIF in the superior lumbar spine requires a thorough knowledge of renal visceral and vascular anatomy. Supernumerary renal arteries occur in 25%–40% of the population and occur most frequently on the left and superior to the usual renal artery trunk. These arteries can vary in number, position, and course from the aorta and position relative to the usual renal artery trunk. Understanding of renal anatomy and the potential variability of the renal vasculature is essential to prevent iatrogenic injury.