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John H. Shin and Ajit A. Krishnaney

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.

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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.

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Sepideh Amin-Hanjani, John H. Shin, Meide Zhao, Xinjian Du and Fady T. Charbel

Object

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.

Methods

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).

Conclusions

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.

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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.

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John H. Shin, Sebastian R. Herrera, Paula Eboli, Sabri Aydin, Emad H. Eskandar and Konstantin V. Slavin

Object

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.

Methods

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.

Results

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.

Conclusions

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.

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Graeme F. Woodworth, Kunal S. Patel, Benjamin Shin, Jan-Karl Burkhardt, Apostolos John Tsiouris, Edward D. McCoul, Vijay K. Anand and Theodore H. Schwartz

Object

This study details the extent of resection and complications associated with endonasal endoscopic surgery for pituitary tumors invading the cavernous sinus (CS) using a moderately aggressive approach to maximize extent of resection through the medial CS wall while minimizing the risk of cranial neuropathy and blood loss. Tumor in the medial CS was aggressively pursued while tumor in the lateral CS was debulked in preparation for radiosurgery.

Methods

A prospective surgical database of consecutive endonasal pituitary surgeries with verified CS invasion on intraoperative visual inspection was reviewed. The extent of resection as a whole and within the CS was assessed by an independent neuroradiologist using pre- and postoperative Knosp-Steiner (KS) categorization and volumetrics of the respective MR images. The extent of resection and clinical outcomes were compared for medial (KS 1–2) and lateral (KS 3–4) lesions.

Results

Thirty-six consecutive patients with pituitary adenomas involving the CS who had surgery via an endonasal endoscopic approach were identified. The extent of resection was 84.6% for KS 1–2 and 66.6% for KS 3–4 (p = 0.04). The rate of gross-total resection was 53.8% for KS 1–2 and 8.7% for KS 3–4 (p = 0.0006). Six patients (16.7%) had preoperative cranial neuropathies, and all 6 had subjective improvement after surgery. Surgical complications included 2 transient postoperative cranial neuropathies (5.6%), 1 postoperative CSF leak (2.8%), 1 reoperation for mucocele (2.8%), and 1 infection (2.8%).

Conclusions

The endoscopic endonasal “medial-to-lateral” approach permits safe debulking of tumors in the medial and lateral CS. Although rates of gross-total resection are moderate, particularly in the lateral CS, the risk of permanent cranial neuropathy is extremely low and there is a high chance of improvement of preexisting deficits. This approach can also facilitate targeting for postoperative radiosurgery.

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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

OBJECTIVE

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.

METHODS

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.

RESULTS

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%.

CONCLUSIONS

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.

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Matthew J. Koch, Christopher J. Stapleton, Pankaj K. Agarwalla, Collin Torok, John H. Shin, Jean-Valery Coumans, Lawrence F. Borges, Christopher S. Ogilvy, James D. Rabinov and Aman B. Patel

OBJECTIVE

Vascular malformations of the spine represent rare clinical entities with profound neurological implications. Previously reported studies on management strategies for spinal dural arteriovenous fistulas (sDAVFs) appeared before the advent of modern liquid embolic agents. Authors of the present study review their institutional experience with endovascularly and surgically treated sDAVFs.

METHODS

The authors performed a retrospective, observational, single-center case series on sDAVFs treated with endovascular embolization, microsurgical occlusion, or both between 2004 and 2013. The mode, efficacy, and clinical effect of treatment were evaluated.

RESULTS

Forty-seven patients with spinal arteriovenous malformations were evaluated using spinal angiography, which demonstrated 34 Type I sDAVFs (thoracic 20, lumbar 12, and cervical 2). Twenty-nine of the patients (85%) were male, and the median patient age was 63.3 years. Twenty patients underwent primary endovascular embolization (16 Onyx, 4 N-butyl cyanoacrylate [NBCA]), and 14 underwent primary surgical clipping. At a mean follow-up of 36 weeks, according to angiography or MR angiography, 5 patients treated with endovascular embolization demonstrated persistent arteriovenous shunting, whereas none of the surgically treated patients showed lesion persistence (p = 0.0237). Thirty patients (88%) experienced some resolution of their presenting symptoms (embolization 17 [85%], surgery 13 [93%], p = 1.00).

CONCLUSIONS

Microsurgical occlusion remains the most definitive treatment modality for sDAVFs, though modern endovascular techniques remain a viable option for the initial treatment of anatomically amenable lesions. Treatment of these lesions usually results in some clinical improvement.

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Christoph P. Hofstetter, Benjamin J. Shin, Lynn Mubita, Clark Huang, Vijay K. Anand, John A. Boockvar and Theodore H. Schwartz

Object

The purpose of this study was to analyze preoperative predictors of endocrinological remission following endonasal endoscopic resection of therapy-resistant prolactin-, growth hormone (GH)–, and adrenocorticotropic hormone (ACTH)–secreting pituitary adenomas and to establish benchmarks for cure by using the most recent consensus criteria.

Methods

The authors reviewed a prospective database of 86 consecutive functional pituitary adenomas that were resected by a purely endoscopic endonasal transsphenoidal technique. Extent of resection was evaluated on postoperative contrast-enhanced MR imaging. Endocrinological remission was defined according to the most recent consensus criteria.

Results

The majority of functional adenomas (62.8%) were classified as macroadenomas (> 1 cm in maximum diameter), and 20.9% of lesions had invaded the cavernous sinus (CS) at the time of surgery. A gross-total resection was achieved in 75.6% of all patients. The rate of endocrinological remission differed between various types of functional adenomas. Cure rates were 92.3% (microadenomas) and 57.1% (macroadenomas) for prolactinomas, 75% (microadenomas) and 40% (macroadenomas) for GH-secreting tumors, and 54.5% (microadenomas) and 71.4% (macroadenomas) for ACTH-secreting tumors. Lower rates of cure occurred in GH-secreting macroadenomas due to a high rate of CS invasion, and in ACTH-secreting adenomas due to a high rate of lesions that were not visible on preoperative MR imaging. Whereas univariate analysis showed that macroadenoma, suprasellar, cavernous extension, or extent of resection correlated with cure, on multivariate analysis, only extent of resection and suprasellar extension predicted cure. One patient developed postoperative meningitis that was complicated by hydrocephalus requiring a ventriculoperitoneal shunt. Two patients developed postoperative panhypopituitarism, and 2 patients suffered from CSF leaks, which were treated with lumbar CSF diversion.

Conclusions

This paper reports benchmarks for endocrinological cure as well as complications in a large series of purely endoscopic pituitary surgeries by using the most recent consensus criteria. The advantages of extended endonasal approaches are most profound in tumors with suprasellar extension and CS invasion.

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Ganesh M. Shankar, Michelle J. Clarke, Tamir Ailon, Laurence D. Rhines, Shreyaskumar R. Patel, Arjun Sahgal, Ilya Laufer, Dean Chou, Mark H. Bilsky, Daniel M. Sciubba, Michael G. Fehlings, Charles G. Fisher, Ziya L. Gokaslan and John H. Shin

OBJECTIVE

Primary osteosarcoma of the spine is a rare osseous neoplasm. While previously reported retrospective studies have demonstrated that overall patient survival is impacted mostly by en bloc resection and chemotherapy, the continued management of residual disease remains to be elucidated. This systematic review was designed to address the role of revision surgery and multimodal adjuvant therapy in cases in which en bloc excision is not initially achieved.

METHODS

A systematic literature search spanning the years 1966 to 2015 was performed on PubMed, Medline, EMBASE, and Web of Science to identify reports describing outcomes of patients who underwent biopsy alone, neurological decompression, or intralesional resection for osteosarcoma of the spine. Studies were reviewed qualitatively, and the clinical course of individual patients was aggregated for quantitative meta-analysis.

RESULTS

A total of 16 studies were identified for inclusion in the systematic review, of which 8 case reports were summarized qualitatively. These studies strongly support the role of chemotherapy for overall survival and moderately support adjuvant radiation therapy for local control. The meta-analysis revealed a statistically significant benefit in overall survival for performing revision tumor debulking (p = 0.01) and also for chemotherapy at relapse (p < 0.01). Adjuvant radiation therapy was associated with longer survival, although this did not reach statistical significance (p = 0.06).

CONCLUSIONS

While the initial therapeutic goal in the management of osteosarcoma of the spine is neoadjuvant chemotherapy followed by en bloc marginal resection, this objective is not always achievable given anatomical constraints and other limitations at the time of initial clinical presentation. This systematic review supports the continued aggressive use of revision surgery and multimodal adjuvant therapy when possible to improve outcomes in patients who initially undergo subtotal debulking of osteosarcoma. A limitation of this systematic review is that lesions amenable to subsequent resection or tumors inherently more sensitive to adjuvants would exaggerate a therapeutic effect of these interventions when studied in a retrospective fashion.