Vivek A. Mehta

Factors associated with progression-free survival and long-term neurological outcome after resection of intramedullary spinal cord tumors: Analysis of 101 consecutive cases - Clinical article

OBJECT With the introduction of electrophysiological spinal cord monitoring, surgeons have been able to perform radical resection of intramedullary spinal cord tumors (IMSCTs). However, factors associated with tumor resectability, tumor recurrence, and long-term neurological outcome are poorly understood. METHODS The authors retrospectively reviewed 101 consecutive cases of IMSCT resection in adults and children at a single institution. Neurological function and MR images were evaluated preoperatively, at discharge, 1 month after surgery, and every 6 months thereafter. Factors associated with gross-total resection (GTR), progression-free survival (PFS), and long-term neurological improvement were assessed using multivariate regression analysis. RESULTS The mean age of the patients was 41 +/- 18 years and 17 (17%) of the patients were pediatric. Pathological type included ependymoma in 51 cases, hemangioblastoma in 15, pilocytic astrocytoma in 16, WHO Grade II astrocytoma in 10, and malignant astrocytoma in 9. A GTR was achieved in 60 cases (59%). Independent of histological tumor type, an intraoperatively identifiable tumor plane (OR 25.3, p < 0.0001) and decreasing tumor size (OR 1.2, p = 0.05) were associated with GTR. Thirty-four patients (34%) experienced acute neurological decline after surgery (associated with increasing age [OR 1.04, p = 0.02] and with intraoperative change in motor evoked potentials [OR 7.4, p = 0.003]); in 14 (41%) of these patients the change returned to preoperative baseline within 1 month. In 31 patients (31%) tumor progression developed by last follow-up (mean 19 months). Tumor histology (p < 0.0001) and the presence of an intraoperatively identified tumor plane (hazard ratio [HR] 0.44, p = 0.027) correlated with improved PFS. A GTR resulted in improved PFS for hemangioblastoma (HR 0.004, p = 0.04) and ependymoma (HR 0.2, p = 0.02), but not astrocytoma. Fifty-five patients (55%) maintained overall neurological improvement by last follow-up. The presence of an identifiable tumor plane (HR 3.1, p = 0.0004) and improvement in neurological symptoms before discharge (HR 2.3, p = 0.004) were associated with overall neurological improvement by last follow-up (mean 19 months). CONCLUSIONS Gross-total resection can be safely achieved in the vast majority of IMSCTs when an intraoperative plane is identified, independent of pathological type. The incidence of acute perioperative neurological decline increases with patient age but will improve to baseline in nearly half of patients within 1 month. Long-term improvement in motor, sensory, and bladder dysfunction may be achieved in a slight majority of patients and occurs more frequently in patients in whom a surgical plane can be identified. A GTR should be attempted for ependymoma and hemangioblastoma, but it may not affect PFS for astrocytoma. For all tumors, the intraoperative finding of a clear tumor plane of resection carries positive prognostic significance across all pathological types.

Implications of spinopelvic alignment for the spine surgeon.

The relation of the pelvis to the spine has previously been overlooked as a contributor to sagittal balance. However, it is now recognized that spinopelvic alignment is important to maintain an energy-efficient posture in normal and disease states. The pelvis is characterized by an important anatomic landmark, the pelvic incidence (PI). The PI does not change after adolescence, and it directly influences pelvic alignment, including the parameters of pelvic tilt (PT) and sacral slope (SS) (PI = PT 1 SS), overall sagittal spinal balance, and lumbar lordosis. In the setting of an elevated PI, the spineadapts with increased lumbar lordosis. To prevent or limit sagittal imbalance, the spine may also compensate with increased PT or pelvic retroversion to attempt to maintain anupright posture. Abnormal spinopelvic parameters contribute to multiple spinal conditions including isthmic spondylolysis, degenerative spondylolisthesis, deformity, and impact outcome after spinal fusion. Sagittal balance, pelvic incidence, and all spinopelvic parameters are easily and reliably measured on standing, full-spine (lateral) radiographs, and it is essential to accurately assess and measure these sagittal values to understand their potential role in the disease process, and to promote spinopelvic balance at surgery. In this article, we provide a comprehensive review of the literature regarding the implications of abnormal spinopelvic parameters and discuss surgical strategies for correction of sagittal balance. Additionally, the authors rate and critique the quality of the literature cited in a systematic review approach to give the reader an estimate of the veracity of the conclusions reached from these reports.

Translaminar versus pedicle screw fixation of C2: comparison of surgical morbidity and accuracy of 313 consecutive screws.

OBJECTIVE C2 translaminar (TL) screws rigidly capture the posterior elements of C2, avoid risk of vertebral artery injury, and are less technically demanding than C2 pedicle (PD) screws. However, a C2-TL screw breach places the spinal cord at risk, and the durability of C2-TL screws remains unknown. It is unclear if TL versus PD screw fixation of C2 is truly associated with less operative morbidity, greater accuracy of screw placement, or equivalent durability. METHODS We retrospectively reviewed the records of 167 consecutive patients undergoing posterior cervical fusion with either PD or TL screw fixation of C2. Perioperative morbidity, breach of the C2 lamina or pedicle on postoperative computed tomographic scans, and rates of operative revision were compared between PD and TL screw constructs in axial (C1–C2 or C1–C3) and subaxial (C2 and caudal) cervical fusions. RESULTS In total, 152 C2-TL screws and 161 C2-PD screws were placed in 167 patients. Thirty-one (19%) cases of axial cervical fusion (C1–C2 or C1–C3) were performed (mean age, 63.8 ± 20.6 years) with either C2-TL (16 [52%]) or C2-PD (15 [48%]) screw fixation. One hundred thirty-six (81%) cases of subaxial cervical fusion (C2-caudal) were performed (mean age, 57.9 ± 14.7 years) with either C2-TL (66 [49%]) or C2-PD (70 [51%]) screw fixation. For both axial and subaxial cervical fusions, baseline patient characteristics and all measures of perioperative morbidity were similar between C2-TL and C2-PD screw cohorts. In total, 11 (7%) PD screws breached the pedicle (0 requiring acute revision) versus only 2 (1.3%) TL screws that breached the C2 lamina (1 requiring acute revision) (P = 0.018). By 1 year postoperatively, pseudoarthrosis or screw pullout requiring reoperation was required in 4 (6.1%) patients with C2-TL screws versus 0 (0%) patients with PD screws (P < 0.05 for subaxial constructs). No cases of C2-TL or C2-PD axial fusion required reoperation or screw pullout or pseudoarthrosis. CONCLUSION In our experience, radiographic breach of C2 pedicle screws occurred more frequently than C2 laminar screw breach. However, this was not associated with an increase in morbidity. By 12 months postoperatively, C2-TL screws were associated with a greater incidence of operative revision when used in subaxial constructs but similarly effective for axial cervical constructs. The 1-year durability of C2-TL screws might be inferior to C2 pedicle screws for subaxial fusions, but equally effective for axial cervical fusions.

The evolution of surgical management for craniosynostosis.

Craniosynostosis, the premature closure of cranial sutures, has been known to exist for centuries, but modern surgical management has only emerged and evolved over the past 100 years. The success of surgery for this condition has been based on the recognition of scientific principles that dictate brain and cranial growth in early infancy and childhood. The evolution of strip craniectomies and suturectomies to extensive calvarial remodeling and endoscopic suturectomies has been driven by a growing understanding of how a prematurely fused cranial suture can affect the growth and shape of the entire skull. In this review, the authors discuss the early descriptions of craniosynostosis, describe the scientific principles upon which surgical intervention was based, and briefly summarize the eras of surgical management and their evolution to present day.

Trans-foraminal versus posterior lumbar interbody fusion: comparison of surgical morbidity

Abstract Background: Posterior lumbar interbody fusion (PLIF) and trans-foraminal lumbar interbody fusion (TLIF) are both accepted surgical approaches for spinal fusion in spondylolisthesis and degenerative disc disease. The unilateral approach of TLIF may minimize the risk of iatrogenic durotomy and nerve root injury; however, there is no definitive evidence to support either approach. We review our experience with TLIF versus PLIF to compare operative complications. Methods: We retrospectively reviewed 119 consecutive cases of PLIF or TLIF performed for degenerative disc disease or spondylolithesis at a single institution over 5 years and examined the incidences of operative complications and outcomes. Results: PLIF was performed in 76 (63%) patients and TLIF in 43 (37%). Patients were 48±13 years old and presented with mechanical back pain [109 (92%)], radicular pain [95 (80%)], and radicular motor weakness [10 (8%)]. Patients undergoing PLIF and TLIF had similar baseline demographic, clinical, and radiographic characteristics. PLIF was associated with a higher incidence of post-operative iatrogenic nerve root dysfunction [6 (7·8%) versus 1 (2%)] and durotomy [13 (17%) versus 4 (9%)]; however, these differences did not reach statistical significance. All cases of nerve root injury were transient and resolved by the third month post-operatively. Estimated operative blood loss, length of hospitalization, and other peri-operative indices were similar between cohorts. By 12 months, evidence of pseudoarthrosis was present in 2 (2·6%) and 2 (4·6%) patients with PLIF or TLIF, respectively. There was a similar incidence of improvement in radicular pain (88% versus 79%) and low back pain (74% versus 80%) between TLIF and PLIF. Conclusion: In our experience with surgical management of degenerative disc disease and spondylolesthesis, PLIF versus TLIF was associated with a trend toward a higher incidence of nerve root injury and durotomy. However, iatrogenic nerve root dysfunction was transient in all cases and 12-month pseudoarthrosis rates were similar between cohorts. Similar to previous clinical studies, the incidence of neurological complications and durotomy increases when an interbody fusion is performed through a posterior approach compared to non-interbody fusion techniques. However, the fusion rates with the interbody technique are also enhanced. TLIF and PLIF should only be considered when the goals of surgery cannot be addressed with decompression and traditional posterolateral fusion.

Advanced Imaging Modalities in the Detection of Cerebral Vasospasm

The pathophysiology of cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH) is complex and is not entirely understood. Mechanistic insights have been gained through advances in the capabilities of diagnostic imaging. Core techniques have focused on the assessment of vessel caliber, tissue metabolism, and/or regional perfusion parameters. Advances in imaging have provided clinicians with a multifaceted approach to assist in the detection of cerebral vasospasm and the diagnosis of delayed ischemic neurologic deficits (DIND). However, a single test or algorithm with broad efficacy remains elusive. This paper examines both anatomical and physiological imaging modalities applicable to post-SAH vasospasm and offers a historical background. We consider cerebral blood flow velocities measured by Transcranial Doppler Ultrasonography (TCD). Structural imaging techniques, including catheter-based Digital Subtraction Angiography (DSA), CT Angiography (CTA), and MR Angiography (MRA), are reviewed. We examine physiologic assessment by PET, HMPAO SPECT, 133Xe Clearance, Xenon-Enhanced CT (Xe/CT), Perfusion CT (PCT), and Diffusion-Weighted/MR Perfusion Imaging. Comparative advantages and limitations are discussed.

Pediatric tethered cord syndrome: response of scoliosis to untethering procedures. Clinical article.

OBJECT Tethered cord syndrome (TCS) is frequently associated with scoliosis in the pediatric population. Following spinal cord untethering, many patients continue to experience progression of spinal deformity. However, the incidence rate, time course, and risk factors for scoliosis progression following tethered cord release remain unclear. The aim of this study was to determine factors associated with scoliosis progression and whether tethered cord release alone would halt curve progression in pediatric TCS. METHODS The authors retrospectively reviewed 27 consecutive pediatric cases of spinal cord untethering associated with scoliosis. The incidence rate and factors associated with scoliosis progression (> 10 degrees increased Cobb angle) after untethering were evaluated using the Kaplan-Meier method. RESULTS The mean age of the patients was 8.9 years. All patients underwent cord untethering for lower-extremity weakness, back and leg pain, or bowel and bladder changes. Mean +/- SD of the Cobb angle at presentation was 41 +/- 16 degrees . The cause of the spinal cord tethering included previous myelomeningocele repair in 14 patients (52%), fatty filum in 5 (18.5%), lipomeningocele in 3 (11%), diastematomyelia in 2 (7.4%), arthrogryposis in 1 (3.7%), imperforate anus with an S-2 hemivertebra in 1 (3.7%), and lipomyelomeningocele with occult dysraphism in 1 (3.7%). Mean follow-up was 6 +/- 2 years. Twelve patients (44%) experienced scoliosis progression occurring a median of 2.4 years postoperatively and 8 (30%) required subsequent fusion for progression. At the time of untethering, scoliosis < 40 degrees was associated with a 32% incidence of progression, whereas scoliosis > 40 degrees was associated with a 75% incidence of progression (p < 0.01). Patients with Risser Grades 0-2 were also more likely to experience scoliosis progression compared with Risser Grades 3-5 (p < 0.05). Whereas nearly all patients with Risser Grades 0-2 with curves > 40 degrees showed scoliosis progression (83%), 54% of patients with Risser Grades 0-2 with curves < 40 degrees progressed, and no patients with Risser Grades 3-5 with curves < 40 degrees progressed following spinal cord untethering. CONCLUSIONS In this experience with pediatric TCS-associated scoliosis, patients with Risser Grades 3-5 and Cobb angles < 40 degrees did not experience curve progression after tethered cord release. Patients with Risser Grades 0-2 and Cobb angles > 40 degrees were at greatest risk of curve progression after cord untethering. Pediatric patients with TCS-associated scoliosis should be monitored closely for curve progression using standing radiographs after spinal cord untethering, particularly those with curves > 40 degrees or who have Risser Grades 0-2.

Safety and efficacy of concurrent pediatric spinal cord untethering and deformity correction

Study Design A retrospective clinical records analysis of concurrent pediatric spinal cord deformity correction and tethered cord release compared with a 2-staged approach. Objective To compare the safety and efficacy of a single-staged approach for pediatric spinal deformity correction and tethered cord release to a conventional 2-staged approach. Summary of Background Data Tethered cord syndrome (TCS) is frequently associated with scoliosis in the pediatric population. Conventional practice suggests waiting several months after untethering for scoliosis correction; however, some patients will experience progression of their spinal deformity. We report the efficacy and safety of concurrent tethered cord release and scoliosis and/or kyphosis deformity correction in a series of pediatric patients. Methods We retrospectively reviewed 15 consecutive pediatric cases of concurrent spinal cord untethering and deformity correction with fusion for scoliosis and/or kyphosis. The clinical and radiologic presentation, operative details, morbidity, and postoperative outcomes were evaluated. Outcomes of this cohort were then compared with 21 patients who underwent a 2-staged untethering surgery followed by scoliosis correction. We provide a review of the literature of the treatment of tethered cord associated with spine deformities. Results The mean age of patients undergoing concurrent untethering and curve correction was 9.6 years (5 male, 10 female). Tethered cord was because of myelomeningocele (5 patients), thickened filum terminale (5 patients), lipomyelomeningocele (4 patients), and retethering from an unknown primary TCS etiology (1 patient). The mean scoliosis Cobb angle (±SD) at presentation was 55.4±21.0 degrees (range, 32.3 degrees to 95.0 degrees) whereas average kyphosis was 112.7±43.6 degrees (range, 68.0 degrees to 155.0 degrees). Average postoperative scoliosis curve was 40.0 degrees, resulting in an average correction of 27%; kyphosis curve was 55.7 degrees resulting in an average correction of 50%. The average operation time was 8.6 hours (range, 3.9 to 13.7 h) and the average blood loss was 1266 mL (range, 400 to 5000 mL). Average length of hospitalization was 10.1 days (range, 4 to 34 d). New onset or worsening of neurologic deficits, bowel or bladder dysfunction, or TCS associated pain did not occur in any patients. At a mean follow-up of 5.7 years (range, 1.3 to 11.8 y), only 1 (7%) patient required subsequent surgery for pseudoarthrosis. The 2-staged cohort experienced a longer cumulative operative time (11.2 vs 8.6 h, P<0.05), more total blood loss (1534 vs 1266 mL, P<0.05), longer total days of hospitalization (14.8 vs 10.1 d, P<0.05), and a greater incidence of dural tear (9.5% vs 0%), wound infection (26% vs 0%), and retethering (9.5% vs 0%). Conclusion Concurrent tethered cord release and spinal fusion for correction of scoliosis and/or kyphosis may be a safe and effective approach in patients likely to experience deformity progression.

Local delivery of rapamycin: a toxicity and efficacy study in an experimental malignant glioma model in rats

Rapamycin, an anti-proliferative agent, is effective in the treatment of renal cell carcinoma and recurrent breast cancers. We proposed that this potent mammalian target of rapamycin inhibitor may be useful for the treatment of gliomas as well. We examined the cytotoxicity of rapamycin against a rodent glioma cell line, determined the toxicity of rapamycin when delivered intracranially, and investigated the efficacy of local delivery of rapamycin for the treatment of experimental malignant glioma in vivo. We also examined the dose-dependent efficacy of rapamycin and the effect when locally delivered rapamycin was combined with radiation therapy. Rapamycin was cytotoxic to 9L cells, causing 34% growth inhibition at a concentration of 0.01 µg/mL. No in vivo toxicity was observed when rapamycin was incorporated into biodegradable caprolactone-glycolide (35:65) polymer beads at 0.3%, 3%, and 30% loading doses and implanted intracranially. Three separate efficacy studies were performed to test the reproducibility of the effect of the rapamycin beads as well as the validity of this treatment approach. Animals treated with the highest dose of rapamycin beads tested (30%) consistently demonstrated significantly longer survival durations than the control and placebo groups. All dose-escalating rapamycin bead treatment groups (0.3%, 3% and 30%), treated both concurrently with tumor and in a delayed manner after tumor placement, experienced a significant increase in survival, compared with controls. Radiation therapy in addition to the simultaneous treatment with 30% rapamycin beads led to significantly longer survival duration than either therapy alone. These results suggest that the local delivery of rapamycin for the treatment of gliomas should be further investigated.

Sacral tumor resection and the impact on pelvic incidence

OBJECT pelvic incidence (PI) directly regulates lumbar lordosis and is a key determinant of sagittal spinal balance in normal and diseased states. Pelvic incidence is defined as the angle between the line perpendicular to the S-1 endplate at its midpoint and the line connecting this point to a line bisecting the center of the femoral heads. It reflects an anatomical value that increases with growth during childhood but remains constant in adulthood. It is not altered by changes in patient position or after traditional lumbosacral spinal surgery. There are only 2 reports of PI being altered in adults, both in cases of sacral fractures resulting in lumbopelvic dissociation and sacroiliac (SI) joint instability. En bloc sacral amputation and sacrectomy are surgical techniques used for resection of certain bony malignancies of the sacrum. High, mid, and low sacral amputations result in preservation of some or the entire SI joint. Total sacrectomy results in complete disruption of the SI joint. The purpose of this study was to determine if PI is altered as a result of total or subtotal sacral resection. METHODS the authors reviewed a series of 42 consecutive patients treated at The Johns Hopkins Hospital between 2004 and 2009 for sacral tumors with en bloc resection. The authors evaluated immediate pre- and postoperative images for modified pelvic incidence (mPI) using the L-5 inferior endplate, as the patients undergoing a total sacrectomy are missing the S-1 endplate postoperatively. The authors compared the results of total versus subtotal sacrectomies. RESULTS twenty-two patients had appropriate images to measure pre- and postoperative mPI; 17 patients had high, mid, or low sacral amputations with sparing of some or the entire SI joint, and 5 patients underwent a total sacrectomy, with complete SI disarticulation. The mean change in mPI was statistically different (p < 0.001) for patients undergoing subtotal versus those undergoing total sacrectomy (1.6° ± 0.9° vs 13.6° ± 4.9° [± SD]). There was no difference between patients who underwent a high sacral amputation (partial SI resection, mean 1.6°) and mid or low sacral amputation (SI completely intact, mean 1.6°). CONCLUSIONS the PI is altered during total sacrectomy due to complete disarticulation of the SI joint and discontinuity of the spine and pelvis, but it is not changed if any of the joint is preserved. Changes in PI influence spinopelvic balance and may have postoperative clinical importance. Thus, the authors encourage attention to spinopelvic alignment during lumbopelvic reconstruction and fixation after tumor resection. Long-term studies are needed to evaluate the impact of the change in PI on sagittal balance, pain, and ambulation after total sacrectomy.