Idiopathic ventral spinal cord herniation is a rare condition that has been increasingly reported in the last decade. The natural history and optimal management have yet to be defined. Therefore, debate exists regarding the pathogenesis and surgical management of this condition. The purpose of this review article is to further educate neurosurgeons about the surgical techniques and outcomes associated with treating this rare and often misdiagnosed condition.
John H. Shin and Ajit A. Krishnaney
Benjamin J. Shin, Innocent U. Njoku, A. John Tsiouris and Roger Härtl
Three-dimensional spinal navigation increases screw accuracy, but its implementation in clinical practice has been difficult, mainly because of surgeons' concerns about increased operative times, disturbance of workflow, and safety. The authors present a custom-designed navigated guide that addresses some of these concerns by allowing for drilling, tapping, and placing the final screw via a minimally invasive approach without the need for K-wires. In this paper, the authors' goal was to describe the technical aspects of the navigated guide tube as well as pedicle screw accuracy.
The authors present the technical details of a navigated guide that allows drilling, tapping, and the placement of the final screw without the need for K-wires. The first 10 patients who received minimally invasive mini-open spinal pedicle screws are presented. The case series focuses on the immediate postoperative outcomes, pedicle screw accuracy, and pedicle screw–related complications. An independent board-certified neuroradiologist determined pedicle screw accuracy according to a 4-tiered grading system.
The navigated guide allowed successful placement of mini-open pedicle screws as part of posterior fixation from L-1 to S-1 without the use of K-wires. Only 7-mm-diameter screws were placed, and 72% of screws were completely contained within the pedicle. Breaches less than 2 mm were seen in 23% of cases, and these were all lateral except for one screw. Breaches were related to the lateral to medial trajectory chosen to avoid the superior facet joint. There were no complications related to pedicle screw insertion.
A novel customized navigated guide tube is presented that facilitates the workflow and allows accurate placement of mini-open pedicle screws without the need for K-wires.
John H. Shin, Michael P. Steinmetz, Edward C. Benzel and Ajit A. Krishnaney
Ossification of the posterior longitudinal ligament is a common cause of radiculopathy and myelopathy that often requires surgery to achieve decompression of the neural elements. With the evolution of surgical technique and a greater understanding of the biomechanics of cervical deformity, the criteria for selecting one approach over the other has been the subject of increased study and remains controversial. Ventral approaches typically consist of variations of the cervical corpectomy, whereas dorsal approaches include a wide range of techniques including laminoplasty, laminectomy, and laminectomy with instrumented fusion. Herein, the features and limitations of these approaches are reviewed with an emphasis on complications and outcomes.
Sepideh Amin-Hanjani, John H. Shin, Meide Zhao, Xinjian Du and Fady T. Charbel
To date, angiography has been the primary modality for assessing graft patency following extracranial–intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography.
One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery).
There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean ± standard error of the mean, 37 ± 13 ml/minute compared with 105 ± 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02).
Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.
William W. Ashley Jr., Sepideh Amin-Hanjani, Ali Alaraj, John H. Shin and Fady T. Charbel
✓Extracranial–intracranial bypass surgery has advanced from a mere technical feat to a procedure requiring careful patient selection and a justifiable decision-making paradigm. Currently available technologies for flow measurement in the perioperative and intraoperative setting allow a more structured and analytical approach to decision making. The purpose of this report is to review the use of flow measurement in cerebral revascularization, presenting algorithms for flow-assisted surgical planning, technique, and surveillance.
Christoph P. Hofstetter, Benjamin Shin, Apostolos John Tsiouris, Eric Elowitz and Roger Härtl
The paracoccygeal approach allows for instrumentation of L5/S1 and L4/5 by using a transsacral rod (AxiaLIF; TransS1, Inc.). The authors analyzed clinical and radiographic outcomes of 1- or 2-level AxiaLIF procedures with focus on durability of the construct.
This was a retrospective study of 38 consecutive patients who underwent either 1-level (32 patients) or 2-level (6 patients) AxiaLIF procedures at the authors' institution. The Oswestry Disability Index (minimum clinically important difference [MCID] ≥ 12) and visual analog scale ([VAS]; MCID ≥ 3) scores were collected. Disc height and Cobb angles were measured on pre- and postoperative radiographs. Bony fusion was determined on CT scans or flexion/extension radiographs.
Implantation of a transsacral rod allowed for intraoperative distraction of the L5/S1 intervertebral space and resulted in increased segmental lordosis postoperatively. At a mean follow-up time of 26.2 ± 2.4 months, however, graft subsidence (1.9 mm) abolished partial correction of segmental lordosis. Moreover, subsidence of the construct reduced L5/S1 lordosis in patients with 1-level AxiaLIF by 3.2° and L4–S1 lordosis in patients with 2-level procedures by 10.1° compared with preoperative values (p < 0.01). Loss of segmental lordosis predicted failure to improve VAS scores for back pain in the patient cohort (p < 0.05). Overall, surgical intervention led to modest symptomatic improvement; only 26.3% of patients achieved an MCID of the Oswestry Disability Index and 50% of patients an MCID of the VAS score for back pain. At last follow-up, 71.9% of L5/S1 levels demonstrated bony fusion (1-level AxiaLIF 80.8%, 2-level AxiaLIF 33.3%; p < 0.05), whereas none of the L4/5 levels in 2-level AxiaLIF fused. Five constructs developed pseudarthrosis and required surgical revision.
The AxiaLIF procedure constitutes a minimally invasive technique for L5/S1 instrumentation, with low perioperative morbidity. However, the axial rod provides inadequate long-term anterior column support, which leads to subsidence and loss of segmental lordosis. Modification of the transsacral technique to allow for placement of a solid interposition graft may counteract subsidence of the construct.
John H. Shin, Sebastian R. Herrera, Paula Eboli, Sabri Aydin, Emad H. Eskandar and Konstantin V. Slavin
Eagle syndrome is characterized by unilateral pain in the oropharynx, face, and earlobe, and is caused by an elongated styloid process or ossification of the stylohyoid ligament with associated compression of the glossopharyngeal nerve. The pain syndrome may be successfully treated with surgical intervention that involves resection of the styloid process. Although nerve decompression is routinely considered a neurosurgical intervention, Eagle syndrome and its treatment are not sufficiently examined in the neurosurgical literature.
A review was performed of cases of Eagle syndrome treated in the Department of Neurosurgery at the University of Illinois at Chicago Medical Center over the last 7 years. The clinical characteristics, radiographic imaging, operative indications, procedural details, surgical morbidity, and clinical outcomes were collected and analyzed.
Of the many patients with facial pain treated between 2001 and 2007, 7 were diagnosed with Eagle syndrome, and 5 of these patients underwent resection of the elongated styloid process. There were 4 women and 1 man, ranging in age from 20 to 68 years (mean 43 years). The average duration of disease was 11 years. In all patients, a preoperative workup revealed unilateral or bilateral elongation of the styloid process. All patients underwent resection of the styloid process on the symptomatic side using a lateral transcutaneous approach. There were no surgical complications. All patients experienced pain relief immediately after the operation. At the latest follow-up (average 46 months, range 7 months to 7.5 years) all but 1 patient maintained complete pain relief. In 1 patient, the pain recurred 12 months postoperatively and additional interventions were required.
Eagle syndrome may be considered an entrapment syndrome of the glossopharyngeal nerve. It is a distinct clinical entity that should be considered when evaluating patients referred for glossopharyngeal neuralgia. The authors' experience indicates that patients with Eagle syndrome may be successfully treated using open resection of the elongated styloid process, which appears to be both safe and effective in terms of long-lasting pain relief.
Jordan S. Terner, Roberto Travieso, Su-shin Lee, Antonio J. Forte, Anup Patel and John A. Persing
Combined metopic and sagittal craniosynostosis is a common variant of the nonsyndromic, multiplesuture synostoses. It is unknown whether this combined form causes reduced intracranial volume (ICV) and potentially more brain dysfunction than sagittal synostosis alone. This study is a volumetric comparison of these 2 forms of craniosynostosis.
The authors conducted a retrospective chart and CT review of 36 cases of isolated sagittal synostosis or combined metopic and sagittal synostosis, involving patients seen between 1998 and 2006. Values were obtained for the intracranial compartment, brain tissue, CSF space, and ventricular volumes. Patients with craniosynostosis were then compared on these measures to 39 age- and sex-matched controls.
In patients with isolated sagittal synostosis and in those with combined metopic and sagittal synostosis, there was a trend toward smaller ICV than in controls (p < 0.1). In female patients older than 4.5 months of age, there was also a trend toward smaller ICV in patients with the combined form than in those with sagittal synostosis alone (p < 0.1), and the ICV of patients with the combined form was significantly smaller than the volume in controls in the same age group (p < 0.05). Brain tissue volume was significantly smaller in both patient groups than in controls (p < 0.05). Ventricular volume was significantly increased (compared with controls) only in the patients with isolated sagittal synostosis who were younger than 4.5 months of age (p < 0.05). Overall CSF space, however, was significantly larger in both patient groups in patients younger than 4.5 months of age (p < 0.05).
These findings raise concerns about intracranial and brain volume reduction in patients with sagittal and combined metopic and sagittal synostoses and the possibility that this volume reduction may be associated with brain dysfunction. Because the ICV reduction is greater in combined metopic and sagittal synostosis in patients older than 4.5 months of age than in sagittal synostosis in this age group, the potential for brain dysfunction may be particularly true for these younger infants.
Maha Saada Jawad, Daniel K. Fahim, Peter C. Gerszten, John C. Flickinger, Arjun Sahgal, Inga S. Grills, Jason Sheehan, Ronald Kersh, John Shin, Kevin Oh, Frederick Mantel and Matthias Guckenberger
The purpose of this study was to identify factors contributing to an increased risk for vertebral compression fracture (VCF) following stereotactic body radiation therapy (SBRT) for spinal tumors.
A total of 594 tumors were treated with spinal SBRT as primary treatment or re-irradiation at 8 different institutions as part of a multi-institutional research consortium. Patients underwent LINAC-based, image-guided SBRT to a median dose of 20 Gy (range 8–40 Gy) in a median of 1 fraction (range 1–5 fractions). Median patient age was 62 years. Seventy-one percent of tumors were osteolytic, and a preexisting vertebral compression fracture (VCF) was present in 24% of cases. Toxicity was assessed following treatment. Univariate and multivariate analyses were performed using a logistic regression method to determine parameters predictive for post-SBRT VCF.
At a median follow-up of 10.1 months (range 0.03–57 months), 80% of patients had local tumor control. At the time of last imaging follow-up, at a median of 8.8 months after SBRT, 3% had a new VCF, and 2.7% had a progressive VCF. For development of any (new or progressive) VCF following SBRT, the following factors were predictive for VCF on univariate analysis: short interval from primary diagnosis to SBRT (less than 36.8 days), solitary metastasis, no additional bone metastases, no prior chemotherapy, preexisting VCF, no MRI used for target delineation, tumor volume of 37.3 cm3 or larger, equivalent 2-Gy-dose (EQD2) tumor of 41.8 Gy or more, and EQD2 spinal cord Dmax of 46.1 Gy or more. Preexisting VCF, solitary metastasis, and prescription dose of 38.4 Gy or more were predictive on multivariate analysis. The following factors were predictive of a new VCF on univariate analysis: solitary metastasis, no additional bone metastases, and no MRI used for target delineation. Presence of a solitary metastasis and lack of MRI for target delineation remained significant on multivariate analysis.
A VCF following SBRT is more likely to occur following treatment for a solitary spinal metastasis, reflecting a more aggressive treatment approach in patients with adequately controlled systemic disease. Higher prescription dose and a preexisting VCF also put patients at increased risk for post-SBRT VCF. In these patients, pre-SBRT cement augmentation could be considered to decrease the risk of subsequent VCF.
Ahmed Hashmi, Matthias Guckenberger, Ron Kersh, Peter C. Gerszten, Frederick Mantel, Inga S. Grills, John C. Flickinger, John H. Shin, Daniel K. Fahim, Brian Winey, Kevin Oh, B. C. John Cho, Daniel Létourneau, Jason Sheehan and Arjun Sahgal
This study is a multi-institutional pooled analysis specific to imaging-based local control of spinal metastases in patients previously treated with conventional external beam radiation therapy (cEBRT) and then treated with re-irradiation stereotactic body radiotherapy (SBRT) to the spine as salvage therapy, the largest such study to date.
The authors reviewed cases involving 215 patients with 247 spinal target volumes treated at 7 institutions. Overall survival was calculated on a patient basis, while local control was calculated based on the spinal target volume treated, both using the Kaplan-Meier method. Local control was defined as imaging-based progression within the SBRT target volume. Equivalent dose in 2-Gy fractions (EQD2) was calculated for the cEBRT and SBRT course using an α/β of 10 for tumor and 2 for both spinal cord and cauda equina.
The median total dose/number of fractions of the initial cEBRT was 30 Gy/10. The median SBRT total dose and number of fractions were 18 Gy and 1, respectively. Sixty percent of spinal target volumes were treated with single-fraction SBRT (median, 16.6 Gy and EQD2/10 = 36.8 Gy), and 40% with multiple-fraction SBRT (median 24 Gy in 3 fractions, EQD2/10 = 36 Gy). The median time interval from cEBRT to re-irradiation SBRT was 13.5 months, and the median duration of patient follow-up was 8.1 months. Kaplan-Meier estimates of 6- and 12-month overall survival rates were 64% and 48%, respectively; 13% of patients suffered a local failure, and the 6- and 12-month local control rates were 93% and 83%, respectively. Multivariate analysis identified Karnofsky Performance Status (KPS) < 70 as a significant prognostic factor for worse overall survival, and single-fraction SBRT as a significant predictive factor for better local control. There were no cases of radiation myelopathy, and the vertebral compression fracture rate was 4.5%.
Re-irradiation spine SBRT is effective in yielding imaging-based local control with a clinically acceptable safety profile. A randomized trial would be required to determine the optimal fractionation.