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  • Author or Editor: Christopher Michael x
  • Journal of Neurosurgery: Spine x
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Michael P. Steinmetz, Christopher D. Kager and Edward C. Benzel

Object. Cervical kyphotic deformation may develop after surgery involving either the ventral or dorsal approach. Regardless of the cause, the development of a cervical kyphotic deformity should be avoided, if possible, and corrected if present, when appropriate. The authors describe their experience with a technique for the ventral correction of iatrogenic (postoperative) cervical kyphosis.

Methods. A retrospective review of cases involving correction of postoperative iatrogenic cervical kyphosis via an ventral approach was performed. The authors conducted an ventral approach to kyphosis correction. The procedure required specific head positioning (in extension), convergent distraction pins, and an ventrally placed implant (axially dynamic when appropriate) with multiple points of fixation including at least one point of intermediate fixation. The pre- and postoperative sagittal angle and clinical status were evaluated.

During a nearly 14-month period, 12 patients met the inclusion criteria. Ten patients underwent a minimum of 6 months of follow up. They comprised the study population. Most patients presented with mechanical neck pain as part of their symptom profile. The mean magnitude of deformity correction (pre- to postoperative) was 20° of lordosis. The mean postoperative sagittal angle was 6° of lordosis. The mean change in the sagittal angle during the follow-up period was 2.2° of lordosis.

Conclusions. The ventral approach to correction of cervical deformity led to the achievement of lordosis in all but one patient. This posture was effectively maintained during the follow-up period. All patients exhibited improvement postoperatively; three experienced complete resolution of their preoperative symptoms. When symptoms are related to postsurgical kyphosis, deformity correction should be considered. Such a procedure may be performed effectively via an ventral approach in most circumstances.

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Christopher I. Shaffrey and Justin S. Smith

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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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G. Edward Vates, Kevin C. Wang, David Bonovich, Christopher F. Dowd and Michael T. Lawton

✓ Bow hunter stroke, which is characterized by transient vertebrobasilar ischemia brought on by head turning, is an unusual condition usually caused by structural abnormalities at the craniocervical junction. The authors present a case in which compression of the left vertebral artery (VA) at the C4–5 level was caused by a laterally herniated intervertebral disc. A 56-year-old man presented with a 6-month history of dizziness and syncope when he turned his head 45° or more to the left. Transcranial Doppler (TCD) ultrasonography demonstrated decreased blood flow through the left VA, and angiography revealed an occlusion of the left VA at the C4–5 level, both when the patient turned his head to the left. Via an anterior cervical approach, the VA canal was unroofed through the transverse foramina to decompress the left VA at C4–5; intraoperatively, the left VA was found to be compressed by a laterally herniated cervical disc fragment. To the best of the authors' knowledge this is the first report of a laterally herniated cervical disc causing bow hunter stroke. The use of TCD may be of value in the diagnosis and management of the disorder, and herniated cervical disc must be included in the roster of potential causes for this rare disease.

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Devon Hoover, Aruna Ganju, Christopher I. Shaffrey, Henry Bartkowski and Michael J. Rauzzino

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William B. Feldman, Aaron J. Clark, Michael Safaee, Christopher P. Ames and Andrew T. Parsa

Object

Myxopapillary ependymomas (MPEs) are rare WHO Grade I tumors found in the conus medullaris, cauda equina, and filum terminale. Treatment generally consists of resection with or without adjuvant radiotherapy. Evidence-based guidelines for surgical management are lacking due to the rarity of this tumor.

Methods

An English-language PubMed search was performed using the key words “myxopapillary” and “ependymoma.” Reports describing fewer than 3 patients or those lacking data on the extent of resection or radiotherapy were excluded. A total of 28 articles describing 475 patients met the authors' inclusion criteria. Patients were grouped by extent of resection and whether or not they underwent adjuvant radiotherapy. Differences in recurrence rates were assessed by chi-square test.

Results

The overall recurrence rate was 15.5% in patients treated by gross-total resection (GTR) and 32.6% in patients treated by subtotal resection (STR), irrespective of whether they underwent adjuvant therapy (p < 0.001). Regardless of the extent of resection, adjuvant radiotherapy was not associated with a decrease in recurrence rates. The overall recurrence rate was 15.6% in patients who underwent GTR and radiotherapy compared with 15.9% in patients who underwent GTR alone (p = 0.58), and it was 29.3% in patients who underwent STR and radiotherapy compared with 35.1% in those who underwent STR alone (p = 0.53). The difference between recurrence rates for patients who underwent GTR alone versus STR and radiotherapy was statistically significant (p = 0.02). Subgroup analysis demonstrated significantly higher recurrence rates in pediatric patients compared with adults (40.5% vs 23.4%, respectively; p = 0.02). Even in the setting of GTR alone, recurrence rates were higher in pediatric patients (65% vs 7.6%; p < 0.001).

Conclusions

Gross-total resection alone is associated with decreased recurrence rates compared with STR with or without radiotherapy. The authors' results suggest that treatment goals should include attempted GTR whenever possible. The observation that children benefitted from radiation therapy to a greater extent than did adults suggests that biological differences between tumors in these patient populations warrants more rigorous scientific studies.

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Gregory C. Wiggins, Michael J. Rauzzino, Henry M. Bartkowski, Russ P. Nockels and Christopher I. Shaffrey

Object. The authors sought to analyze prospectively the outcome of surgery for complex spinal deformity in the pediatric and young adult populations.

Methods. The authors evaluate all pediatric and adolescent patients undergoing operative correction of complex spinal deformity from December 1997 through July 1999. No patient was lost to follow-up review (average 21.1 months). There were 27 consecutive pediatric and adolescent patients (3–20 years of age) who underwent 32 operations. Diagnoses included scoliosis (18 idiopathic, five nonidiopathic) and four severe kyphoscoliosis. Operative correction and arthrodesis were achieved via 21 posterior approaches (Cotrel-Dubousset-Horizon), seven anterior approaches (Isola or Kaneda Scoliosis System), and two combined approaches. Operative time averaged 358 minutes (range 115–620 minutes). Blood loss averaged 807 ml (range 100–2000 ml). Levels treated averaged 9.1 (range three–16 levels). There was a 54% average Cobb angle correction (range 6–82%). No case was complicated by the patient's neurological deterioration, loss of somatosensory evoked potential monitoring, cardiopulmonary disease, donor-site complication, or wound breakdown. There was one case of hook failure and one progression of deformity beyond the site of surgical instrumentation that required reoperation. There were 10 minor complications that did not significantly affect patient outcome. No patient received undirected banked blood products. There was a significant improvement in cosmesis, and no patient experienced continued pain postoperatively. All patients have been able to return to their preoperative activities.

Conclusions. Compared with other major neurosurgical operations, segmental instrumentation for pediatric and adolescent spinal deformity is a safe procedure with minimal morbidity and there is a low risk of needing to use allogeneic blood products.

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David E. Gwinn, Christopher A. Iannotti, Edward C. Benzel and Michael P. Steinmetz

Object

Analysis of cervical sagittal deformity in patients with cervical spondylotic myelopathy (CSM) requires a thorough clinical and radiographic evaluation to select the most appropriate surgical approach. Angular radiographic measurements, which are commonly used to define sagittal deformity, may not be the most appropriate to use for surgical planning. The authors present a simple straight-line method to measure effective spinal canal lordosis and analyze its reliability. Furthermore, comparisons of this measurement to traditional angular measurements of sagittal cervical alignment are made in regards to surgical planning in patients with CSM.

Methods

Twenty preoperative lateral cervical digital radiographs of patients with CSM were analyzed by 3 independent observers on 3 separate occasions using a software measurement program. Sagittal measurements included C2–7 angles utilizing the Cobb and posterior tangent methods, as well as a straight-line method to measure effective spinal canal lordosis from the dorsal-caudal aspect of the C2–7 vertebral bodies. Analysis of variance for repeated measures or Cohen 3-way (kappa) correlation coefficient analysis was performed as appropriate to calculate the intra- and interobserver reliability for each parameter. Discrepancies in angular and effective lordosis measurements were analyzed.

Results

Intra- and interobserver reliability was excellent (intraclass coefficient > 0.75, kappa > 0.90) utilizing all 3 techniques. Four discrepancies between angular and effective lordotic measurements occurred in which images with a lordotic angular measurement did not have lordosis within the ventral spinal canal. These discrepancies were caused by either spondylolisthesis or dorsally projecting osteophytes in all cases.

Conclusions

Although they are reliable, traditional methods used to make angular measurements of sagittal cervical spine alignment do not take into account ventral obstructions to the spinal cord. The effective lordosis measurement method provides a simple and reliable means of determining clinically significant lordosis because it accounts for both overall alignment of the cervical spine as well as impinging structures ventral to the spinal cord. This method should be considered for use in the treatment of patients with CSM.

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Thomas J. Buell, Davis G. Taylor, Ching-Jen Chen, Christopher I. Shaffrey, Justin S. Smith and Shay Bess

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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.