Faculty Bibliography

OBJECT: Intramedullary spinal cord tumors can displace the surrounding neural tissue, causing enlargement and distortion of the normal cord anatomy. Resection requires a midline myelotomy to avoid injury to the posterior columns. Locating the midline for myelotomy is often difficult because of the distorted anatomy. Standard anatomical landmarks may be misleading in patients with intramedullary spinal cord tumors due to cord rotation, edema, neovascularization, or local scar formation. Misplacement of the myelotomy places the posterior columns at risk of significant postoperative disability. The authors describe a technique for mapping the dorsal column to accurately locate the midline. METHODS: A group of 10 patients with cervical and thoracic intramedullary spinal cord lesions underwent dorsal column mapping in which a strip electrode was used to define the midline. After the laminectomy and durotomy, a custom-designed multielectrode grid was placed on the exposed dorsal surface of the spinal cord. The electrode is made up of 8 parallel Teflon-coated stainless-steel wires (76-microm diameter, spaced 1 mm apart) embedded in silastic with each of the wires stripped of its insulating coating along a length of 2 mm. This strip electrode maps the amplitude gradient of conducted spinal somatosensory evoked potentials elicited by bilateral tibial nerve stimulation. Using these recordings, the dorsal columns are topographically mapped as lying between two adjacent numbers. RESULTS: The authors conducted a retrospective analysis of the preoperative, immediate, and short-term postoperative neurological status, focusing especially on posterior column function. There were 8 women and 2 men whose mean age was 52 years. There were 4 ependymomas, 1 subependymoma, 1 gangliocytoma, 1 anaplastic astrocytoma, 1 cavernous malformation, and 2 symptomatic syringes requiring shunting. In all patients the authors attempted to identify the midline by using anatomical landmarks, and then proceeded with dorsal column mapping to identify the midline electrophysiologically. In the 2 patients with syringomyelia and in 5 of the patients with tumors, the authors were unable to identify the midline anatomically with any certainty. In 2 patients with intramedullary tumors, they were able to identify the midline anatomically with certainty. Dorsal column mapping allowed identification of the midline and to confirm the authors' anatomical localization. In 2 patients with intramedullary tumors, posterior column function was preserved only on 1 side. All other patients had intact posterior column function preoperatively. CONCLUSIONS: Dorsal column mapping is a useful technique for guiding the surgeon in locating the midline for myelotomy in intramedullary spinal cord surgery. In conjunction with somatosensory evoked potential, motor evoked potential, and D-wave recordings, we have been able to reduce the surgical morbidity related to dorsal column dysfunction in this small group of patients

OBJECTIVE: To review and compare the techniques of fixation of the axis vertebral segment. Also, to review the anatomy of the axis vertebrae, ligamentous attachments, and unique biomechanics of this segment. METHODS: The use of wire, cable, screw, and plate fixation techniques are reviewed and discussed in the treatment of fractures of C1 and C2 along with utilization of the halo vest and cervical collar during the postoperative period. RESULTS: All fixation methods were useful. However, the appropriate fixation technique is best determined by the local anatomy (eg, anomalous vertebral artery), posterior element fractures, or the necessity to remove the posterior elements for treatment of the underlying condition. CONCLUSION: New techniques for fixation and instrumentation for fixation of the axis are available. Advanced imaging allows for advanced aggressive instrumentation while avoiding injury to adjacent structures. Biomechanical studies have influenced the utility and popularity of each technique

OBJECTIVE: Endoscopic thoracic sympathectomy (ETS) remains the definitive treatment for primary focal hyperhidrosis. Compensatory hyperhidrosis (CH) is a significant drawback of ETS. We sought to identify the predictors for the development of severe CH after ETS, its anatomic locations, and its frequency of occurrence, and we analyzed the impact of CH on patient satisfaction with ETS. METHODS: Bilateral ETS for primary focal hyperhidrosis was performed in 220 patients, and a retrospective chart review was conducted. Follow-up evaluation was conducted using a telephone questionnaire, and 73% of all patients were contacted. Patients' responses regarding CH and their level of satisfaction after ETS were analyzed. Statistical analysis was performed using SPSS software (Version 14.0; SPSS, Inc., Chicago, IL). A P value of <0.05 was considered statistically significant. RESULTS: Some degree of CH developed in 94% of patients. The number of levels treated was not related to the occurrence of severe CH. Isolated T3 ganglionectomy led to a significantly lower incidence of severe CH, when compared with all other levels (P < 0.03). Ninety percent of patients were satisfied with the procedure. The development of severe CH, as opposed to mild or moderate CH, significantly correlated with a lower satisfaction rate (P = 0.003). CONCLUSION: CH is common after ETS procedures, and the occurrence of severe, but not mild or moderate, CH is a major source of dissatisfaction after ETS. The overall occurrence of severe CH is reduced after T3 ganglionectomy as opposed to ganglionectomies performed at all other levels. The level of satisfaction with ETS is high

OBJECT: Chordomas of the cervical spine are rare tumors. Although en bloc resection has proven to be the ideal procedure in other areas, there is controversy regarding this approach in the cervical spine. The goal in this study was to determine whether piecemeal tumor resection was efficient in the management of chordomas that arise in this location. METHODS: The authors retrospectively reviewed all 74 cases of chordoma treated by their group. Seven patients with isolated cervical chordomas who were treated between October 1992 and January 2006 were identified. There were four male and three female patients, whose ages ranged from 6 to 61 years (mean 34.4 years). Follow-up duration ranged from 7 to 169 months (median 23 months). All cases were managed using a retrocarotid approach with mobilization of the vertebral artery. When the tumor could not be completely resected via the initial anterior approach, a subsequent posterior resection was performed. Tumor resection was intralesional in all cases, and gross-total tumor resection was achieved in six cases. One patient required a second resection 4 months later. In all cases, a posterior stabilization procedure was performed. Five patients underwent anterior fusion (three with fibular allograft and two with iliac crest), whereas two underwent occipitocervical fusion. In two patients with dedifferentiated chordoma metastasis developed, and one of them died 7 months later. The other patient with metastasis died suddenly at home 26 months postsurgery, presumably from aspiration. At the time of this submission, there were no signs of recurrence in five patients. CONCLUSIONS: The authors believe that, in most cases, en bloc resection of cervical chordoma is not feasible. This is due to the tendency of chordomas to involve multiple compartments at the time of diagnosis. In the authors' experience, intralesional radical resection remains an effective surgical approach to this disease entity

OBJECTIVE: Neurogenic paravertebral tumors are uncommon neoplasms arising from neurogenic elements within the thorax. These tumors may be dumbbell shaped, extending into the spinal canal or exclusively paraspinal. Generally encapsulated, they are located in the posterior mediastinum. In this report, we present our experience in the thoracoscopic resection of these tumors, including surgical technique and potential pitfalls. METHODS: A retrospective review of patients undergoing endoscopic surgery for paravertebral tumors was undertaken. Patient demographics, charts, operative reports, and pre- and postoperative images were reviewed. RESULTS: Between 1997 and 2004, 13 patients were treated thoracoscopically for paravertebral tumors in our departments. Our population consisted of four men and nine women. The median age was 44.9 years (range, 29-66 yr). Eight patients presented with pain, dyspnea, cough, and weakness. Five patients had tumors found incidentally. Sizes of the tumors varied from 3 to 9 cm. Final pathology included four neurofibromas, eight schwannomas, and one unclassified granular cell tumor. Gross total resection was achieved endoscopically in all cases. Three patients required a hemilaminectomy for resection of the intraspinal dumbbell component of the tumor during the same operation. The mean operative time was 229.5 minutes. The mean estimated blood loss was 371.1 ml. Postoperative morbidities included one each of tongue swelling, ulnar neuropathy, and intercostal hyperesthesia. The mean hospital stay was 2.8 days. CONCLUSION: Paravertebral tumors in the posterior mediastinum are amenable to endoscopic removal, even in hard to reach locations. Tumors with intraspinal extension can be removed concurrently by performing a hemilaminectomy, followed by thoracoscopy, without the need for a thoracotomy

OBJECT: Idiopathic spinal cord herniation (ISCH) is an uncommon clinical entity typically presenting with lower-extremity myelopathy. Despite the existence of 85 ISCH cases in the literature, misdiagnosis and delayed diagnosis remain a major concern. METHODS: The authors conducted a retrospective review of patients who underwent surgery for ISCH at their institutions between 1993 and 2004. Seven patients were treated for ISCH, five in New York and two in Buenos Aires. The patients' ages ranged from 32 to 72 years. There were three men and four women. The interval between the onset of symptoms and surgery ranged from 12 to 84 months (mean 42.1 months). Preoperatively, spinal cord function in four patients was categorized as American Spinal Injury Association (ASIA) Grade D, and that in the other three patients was ASIA Grade C. In all patients a diagnosis of posterior intradural arachnoid cyst had been rendered at other institutions, and three had undergone surgery for the treatment of this entity. In all cases, the herniation was reduced and the defect repaired with a dural patch. The follow-up period ranged from 10 to 147 months (mean 49.2 months). Clinical recovery following surgery varied; however, there was no functional deterioration compared with baseline status. Syringomyelia, accompanied by neurological deterioration, developed post-operatively in two patients at 2 and 10 years, respectively. CONCLUSIONS: Patients presenting with a diagnosis of posterior intradural arachnoid cyst should be evaluated carefully for the presence of an anterior spinal cord herniation. Based on the authors' literature review and their own experience, they recommend offering surgery to patients even when neurological compromise is advanced

OBJECT: Surgical access to tumors at the craniovertebral junction (CVJ) requires extensive bone removal. Guidelines for the use of occipitocervical fusion (OCF) after resection of CVJ tumors have been based on anecdotal evidence. The authors performed a retrospective study of factors associated with the use of OCF in 46 patients with CVJ tumors. The findings were used to develop recommendations for use of OCF in such patients. METHODS: The authors retrospectively reviewed the cases of 51 patients with CVJ tumors treated by their group between March 1991 and February 2004. Forty-six patients were available for follow up. Charts were reviewed to obtain data on demographic characteristics, presenting symptoms, and perioperative complications. Preoperative computerized tomography scans and magnetic resonance imaging studies were obtained in all patients. Occipitocervical fusion was performed in patients who had undergone a unilateral condyle resection in which 70% or more of the condyle was removed, a bilateral condyle resection with 50% removal, or C1-2 vertebral body destruction. Of the 46 patients, 16 had foramen magnum meningiomas, 17 had chordomas, one had a chondrosarcoma, two had Schwann cell tumors, two had glomus tumors, and eight had other types of tumors. Twenty-three (50%) of the 46 patients underwent OCF, including 15 of the 17 patients with chordomas (88%). None of the patients with meningiomas required fusion. Seventeen (71%) of the 24 patients presenting with neck pain preoperatively underwent OCF. CONCLUSIONS: Patients presenting with neck pain had a 71% chance of undergoing OCF. Patients with chordomas and metastatic tumors were most likely to require OCF. One patient with a 50% unilateral condylar resection returned with OC instability for which OCF was required. Based on their clinical experience and published biomechanical studies, the authors recommend that OCF be performed when 50% or more of one condyle is resected

OBJECT: Intramedullary spinal cord tumors (IMSCTs) in the older-age adult population pose complex management issues regarding the extent of resection and functional outcome, especially in terms of quality of life. Historically, IMSCTs in the older adult population were treated with irradiation alone because it was assumed that functional recovery would be poor. The authors examined their IMSCT database and report the first large series of IMSCTs in patients older than 50 years of age. METHODS: In this retrospective clinical and chart review there were 30 cases meeting inclusion criteria drawn from databases at three different institutions. A modified McCormick Scale was used to assess functional levels in all 30 patients pre- and postoperatively. The mean age of patients in this cohort was 59.8 years (range 50-78 years), and the mean follow-up period was 10.6 years (range 2-16 years). Ependymoma was the most common tumor (83%), and 55% were located in the thoracic spine. The most common presenting symptom was sensory dysesthesia, with rare motor loss. The prodromal period to treatment was 19.4 months. Based on the McCormick Scale score at last follow-up examination 67% of patients were clinically functionally the same, 9% were worse, and 24% were improved after surgery. There were two deaths due tumor progression (both malignant tumors) and one recurrence (anaplastic astrocytoma). All three patients in whom malignant astrocytomas were diagnosed underwent postoperative radiation therapy. CONCLUSIONS: In the population of patients older than age 50 years, thoracic ependymomas are the most common IMSCTs that present characteristically with sensory symptoms. The longer prodromal period in the older adult population may reflect the fact that their diagnosis and workup is inadequate. There was no significant increase in the length of stay in the neurosurgical ward. The authors recommend motor evoked potential-guided aggressive microsurgical resection, because the long-term outcome of benign lesions is excellent (good functional recovery and no tumor recurrence)

Complications of minimally invasive spinal surgery can be related to anesthesia, patient positioning, and surgical technique. The performance of successful minimally invasive spinal surgery is beset with several technical challenges, including the limited tactile feedback, two-dimensional video image quality of three-dimensional anatomy, and the manual dexterity needed to manipulate instruments through small working channels, which all account for a very steep learning curve. Knowledge of possible complications associated with particular minimally invasive spinal procedures can aid in their avoidance. This article reviews complications associated with minimally invasive spinal surgery in the cervical, thoracic, and lumbar spine by reviewing reported data of sufficient detail or with sufficient numbers of patients. In addition, possible complications associated with anesthesia use, patient positioning, and surgical techniques during thoracoscopic and laparoscopic spinal procedures are reviewed

The authors describe a case of paraspinal calcinosis in a 65-year-old woman with progressive systemic sclerosis. Although calcinosis occurs in up to 27% of cases of progressive systemic sclerosis, symptomatic paraspinal calcinosis is extremely rare. In the case reported here, multiple cervical facet joints were compromised by progressive calcinosis, leading to glacial spinal instability. Internal fixation was indicated to correct the instability and decompress the spinal canal. Medical therapy was instituted to arrest or reverse the ongoing calcinosis