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Objective: To evaluate risk factors for the development of dysphagia after anterior cervical surgery., Methods: The records of 249 patients who underwent anterior cervical surgery were reviewed. The presence and severity of dysphagia were assessed with the Dysphagia Disability Index 6 weeks and 3, 6, and 12 months after surgery. Age; sex; ethnicity; cigarette smoking; previous cervical surgeries; reoperation for same pathology; type of procedure, incision, and instrumentation; number and levels involved; side of procedure, length of surgery; and use of postoperative bracing were analyzed., Results: During the first 6 months after surgery, 27 (10.8%) patients developed dysphagia. From these patients the presence of dysphagia at 6 weeks and at 3 and 6 months was 88.8%, 29.6%, and 7.4%, respectively. By 12 months, dysphagia had resolved in all cases. The mean age of patients with dysphagia was 55 years (SD 12.98) and 50 years (SD 12.07) in patients without dysphagia (P = 0.05). Dysphagic patients had an average of 2.2 (SD 1.15) levels operated compared with 1.84 (SD 0.950) in nondysphagic patients (P = 0.05). Patients who developed dysphagia were most often treated at C4-5 (67%) and C5-6 (81%: P < 0.001). Although mean operative time was slightly longer in patients with dysphagia (186 minutes) compared with those without (169 minutes), the difference was not significant., Conclusions: In our patients, the incidence of dysphagia was low, and it had completely resolved at 12 months in all cases. Risk factors for dysphagia were multilevel procedures, involvement of C4-5 and C5-6, and age., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: We introduce a technique that enables the use of catheter angiography during image-guided surgery for the resection of previously embolized arteriovenous malformations., Methods: We used models to test the possibility of matching specific anatomic points 1:1 and the accuracy of merging catheter-based 3-dimensional angiography with standard computed tomographic angiography., Results: After obtaining excellent accuracy matching the 2 modalities, we merged both studies into the image-guidance platform. After embolizing a patient's arteriovenous malformation with Onyx, we successfully used the merged study to navigate during surgical resection of the lesion. No complications resulted from this technique, which increases contrast by only 15 cm and radiation exposure by 4 seconds., Conclusion: Catheter-based angiography can be used during image guidance to reduce the artifact from metal particles after embolization. Excellent accuracy was obtained in merging 3-dimensional angiography with computed tomographic angiography. Further studies are needed to evaluate catheter-based 3-dimensional angiography as a single method for navigation during neurovascular surgery.

The authors describe a unique headholder device adapted to facilitate the placement of anterior odontoid screws. The patient's head is affixed in the headholder equipped with an articulating arm that can be placed in a paramedian fashion. This configuration rigidly fixates the head and provides an unencumbered open-mouth view of the odontoid using radiographic images, thus making screw placement easier.

Atlantoaxial stabilization has evolved from simple posterior wiring to transarticular screw fixation. In some patients, however, the course of the vertebral artery (VA) through the axis varies, and therefore transarticular screw placement is not always feasible. For these patients, the authors have developed a novel method of atlantoaxial stabilization that does not require axial screws. In this paper, they describe the use of this technique in the first 10 cases. Ten consecutive patients underwent the combined C1-3 lateral mass-sublaminar axis cable fixation technique. The mean age of the patients was 62.6 years (range 23-84 years). There were six men and four women. Eight patients were treated after traumatic atlantoaxial instability developed (four had remote trauma and previous nonunion), whereas in the other two atlantoaxial instability was caused by arthritic degeneration. All had VA anatomy unsuitable to traditional transarticular screw fixation. There were no intraoperative complications in any of the patients. Postoperative computed tomography studies demonstrated excellent screw positioning in each patient. Nine patients were treated postoperatively with the aid of a rigid cervical orthosis. The remaining patient was treated using a halo fixation device. One patient died of respiratory failure 2 months after surgery. Follow-up data (mean follow-up duration 13.1 months) were available for seven of the remaining nine patients and demonstrated a stable construct with fusion in each patient. The authors present an effective alternative method in which C1-3 lateral mass screw fixation is used to treat patients with unfavorable anatomy for atlantoaxial transarticular screw fixation. In this series of 10 patients, the method was a safe and effective way to provide stabilization in these anatomically difficult patients.

Object: The authors compared the incidence of radiologically documented changes and symptomatic adjacent-level cervical disc disease after single-level discectomy and subsequent cervical fusion or arthroplasty in two independent prospective clinical studies., Methods: The patients were treated with the Affinity Anterior Cervical Cage System or the Bryan Artificial Cervical Disc. In each study the patients were required to undergo serial cervical radiography preoperatively and 24 months postoperatively, as well as serial clinical evaluations including documentation of adverse events, neurological status, and results of the 36-item Short Form Health Survey. All serial radiographs were reviewed prior to evaluating the clinical symptoms for development of increasing or new adjacent degenerative disc disease (DDD). Subsequently, the clinical data were analyzed. For various reasons of exclusion, the cases analyzed in the Bryan disc-treated cohort consisted of 74 patients and in the Affinity system-treated cohort there were 158 patients. New anterior osteophyte formation or enlargement, increased narrowing of an interspace, new DDD, and calcification of the anterior longitudinal ligament were the radiological findings indicative of adjacent-level disease. Fusion was associated with a significant increase in x-ray film-based changes of adjacent-disc disease (p = 0.009, odds ratio [OR] 2.44). In the cage fusion series, the incidence of symptomatic adjacent-level DDD was statistically greater than that in the group treated with the artificial disc (p = 0.018), and the patients required a statistically greater number of medical treatments related to episodic symptoms of neck, shoulder, and arm pain attributed to new disc disease (p = 0.001, OR 35.8)., Conclusions: In comparing these prospective studies the authors demonstrated that maintaining motion rather than fusion will prevent symptomatic adjacent-disc disease and will decrease adjacent-level radiological indicators of disease at a 24-month postoperative interval.

Study Design: Biomechanical laboratory research., Objective: To determine whether anterior, posterior, or combined instrumentation provides the best stability for treating a cervicothoracic compression-flexion injury., Summary of Background Data: As the junction between the mobile cervical spine and rigid thoracic spine, the cervicothoracic junction poses unique challenges to the success of any fixation system spanning this region. Although posterior instrumentation is the preferred method of fixation in the unstable cervical spine, it is unknown whether this is the case across the unstable cervicothoracic junction., Methods: Flexion, extension, lateral bending, and axial rotation of cadaveric specimens were studied during application of nondestructive pure moments in a sequence of conditions: (1) intact, (2) after destabilization, (3) with posterior instrumentation from C6-T1 or T2, and (4) with corpectomy/graft and anterior alone or combined anterior/posterior instrumentation., Results: Compared to anterior instrumentation, posterior instrumentation allowed an 89% smaller range of motion (ROM) during lateral bending (P = 0.01) and 64% smaller ROM during axial rotation (P = 0.04). In most loading modes, combined instrumentation outperformed either anterior or posterior instrumentation alone. Most biomechanical measurements of stability improved when posterior instrumentation was extended from T1 to T2. Small and usually insignificant reductions in ROM averaging 15% were observed with C7 included in the posterior construct versus C7 excluded., Conclusions: Combined instrumentation provides a significant improvement in stability over either anterior or posterior instrumentation alone. Extension of the posterior instrumentation to include T2 improves stability at T1-T2 as well as rostral levels. Inclusion of C7 in the construct is largely inconsequential biomechanically.

Study Design: Comparison of nondestructive multidirectional flexibility in groups of specimens receiving two different posterior instrumentation constructs with or without anterior plating., Objective: To compare stability after a three-column injury stabilized posteriorly by lateral mass screws-rods at C5-C6 and pedicle screws-rods at C7 ("LLP") or by pedicle screws-rods at C5-C6-C7 ("PPP"), and to compare posterior, anterior, and combined anterior-posterior fixation., Summary of Background Data: Pedicle screws resist pullout better than lateral mass screws, but little research has compared the stability of pedicle screws to that of lateral mass screws used within constructs., Methods: Fourteen human cadaveric C4-T1 specimens were tested intact, posteriorly instrumented (7 LLP and 7 PPP), anteriorly instrumented, or with combined (anterior-posterior) instrumentation. Nonconstraining, nondestructive torques induced flexion, extension, lateral bending, and axial rotation while angular motion was recorded optically., Results: Posterior, anterior, and combined instrumentation each significantly improved stability (P < 0.05). Combined fixation provided significantly better stability than either anterior or posterior instrumentation alone. In no loading mode and in no testing condition was any parameter significantly different between LLP and PPP. Posterior instrumentation provided significantly better stability than anterior instrumentation., Conclusions: Anterior plate and posterior screw-rod fixation alone improve stability in a two-level, three-column cervical injury model. Combined fixation further improves stability. There is little discernible difference in immediate postoperative stability between posterior rod constructs combining lateral mass and pedicle screws and those using only pedicle screws.

Study Design: Fifty-two study participants underwent cervical spine surgery using intraoperative Iso-C imaging with or without spinal navigation., Objectives: To evaluate prospectively the feasibility, advantages, limitations, and applications of Iso-C in cervical spine surgery., Summary of Background Data: Existing stereotactic spinal navigational systems images must be acquired before surgery and typically require cumbersome point-to-point registration. Intraoperative computed tomography (CT) and magnetic resonance imaging (MRI) provide real-time information but can restrict access to the patient, preclude the use of traditional operating room tables, and are time-consuming. The Iso-C allows quick, CT-quality, real-time data acquisition without restricting access to the patient. The data acquired can be automatically transferred to navigational systems with the immediate ability to navigate for anterior or posterior cervical spine procedures., Methods: High-resolution isotropic three-dimensional data sets were acquired using the Iso-C intraoperative fluoroscopy in 52 cervical spine cases. In 30 cases, the data were imported automatically to the StealthStation Treon to support neuronavigation. In 22 cases, a postprocedural intraoperative CT was obtained with the Iso-C primarily to assess the extent of osseous decompression and/or the accuracy of implants or instrumentation. In most cases, a postoperative high-resolution CT image was obtained and compared with the Iso-C data., Results: Successful automated registration suitable for navigation was attained for all anterior and posterior cervical spinal cases. The postprocedural intraoperative Iso-C data were 100% concordant with those of postoperative high-resolution CT as determined by a blinded neuroradiologist., Conclusions: Iso-C intraoperative fluoroscopy is an accurate and rapid way to perform CT-quality image-guided navigation in cervical spinal surgery. In most cases, it obviates the need for postoperative imaging.

Object: The authors sought to establish radiological criteria for the diagnosis of C1-2 vertical distraction injuries., Methods: Conventional radiography, computerized tomography (CT), and magnetic resonance (MR) imaging findings in five patients with a C1-2 vertical distraction injury were correlated with their clinical history, operative findings, and autopsy findings. The basion-dens interval (BDI) and the C-1 and C-2 lateral mass interval (LMI) were measured in 93 control patients who underwent CT angiography; these measurements were used to define the normal BDI and LMI. The MR imaging results obtained in 30 healthy individuals were used to characterize the normal signal intensity of the C1-2 joint. The MR imaging results were compared with MR images obtained in five patients with distraction injuries. In the 93 patients, the BDI averaged 4.7 mm (standard deviation [SD] 1.7 mm, range 0.6-9 mm) and the LMI averaged 1.7 mm (SD 0.48 mm, range 0.7-3.3 mm). Based on CT scanning in the five patients with distraction injuries, the BDIs (mean 11.9 mm, SD 3.2 mm; p < 0.001) and LMIs (mean 5.5 mm, SD 2 mm; p < 0.0001) were significantly greater than in the control group. Fast-spin echo inversion-recovery MR images obtained in these five patients revealed markedly increased signal distributed throughout the C1-2 lateral mass articulations bilaterally., Conclusions: In 95% of healthy individuals, the LMI ranged between 0.7 and 2.6 mm. An LMI greater than 2.6 mm indicates the possibility of a distraction injury, which can be confirmed using MR imaging. Patients with a suspected C1-2 distraction injury may be candidates for surgical fusion of C1-2.

Objective: The intraoperative Iso-C C-arm (Siremobil Iso-C 3D; Siemens Medical Solutions, Erlangen, Germany) provides a unique ability to acquire and view multiplanar three-dimensional images of intraoperative anatomy. Registration for intraoperative surgical navigation may be automated, thus simplifying the operative workflow., Methods: Iso-C C-arm intraoperative fluoroscopy acquires 100 images, each of which must be 1.8 degrees in a circumferential fashion about an "isocentric" point in space. The system generates a high-resolution isotropic three-dimensional data set that is available immediately after the 90-second C-arm rotation. The data set is ported to the image-guided workstation, registration is immediate and automated, and the surgeon can navigate with millimetric accuracy. The authors prospectively examined data from the initial 60 patients examined with the Iso-C, among whom were cases of anterior and posterior spinal instrumentation from the occiput to the sacrum. Percutaneous and minimally invasive spinal and cranial procedures were also included., Results: Automated registration for image-guided navigation was attainable for anterior and posterior cases from the cranial base and entire spine. In most cases, intraoperative postprocedural imaging with the Iso-C mitigated the need for postoperative imaging., Conclusion: Intraoperative Iso-C three-dimensional scanning allows real-time feedback during cranial base and spinal surgery and during procedures involving instrumentation. In most cases, it obviates the need for postoperative computed tomography. Its usefulness is in its simplicity, and it can be easily adapted to the operating room workflow. When coupled with intraoperative navigation, this new technology facilitates complex neurosurgical procedures by improving the accuracy, safety, and time of surgery.

Purpose: We established a canine model of subfertility after spinal cord injury and examined the time course of acute changes in semen quality and spermatogenesis after spinal cord injury., Materials and Methods: Seven dogs underwent surgical T7 spinal cord injury. Six dogs were used as controls. Electroejaculation and testicular fine needle aspiration were performed at baseline and twice weekly for 3 weeks after spinal cord injury. Semen quality change was examined by standard semen analysis. Spermatogenesis was assessed by flow cytometry of testicular fine needle aspiration in all dogs as well as by testicular histology at study conclusion in 4 controls and 4 spinal cord injured dogs., Results: No significant changes in spinal cord injured dogs were noted before 3 weeks after injury. From baseline to 3 weeks after injury certain changes were evident in spinal cord injured dogs. Mean antegrade sperm motility decreased from 62.9% to 20.1% (p = 0.008), mean total sperm (antegrade plus retrograde total sperm) decreased from 423 to 294 x 106 which was not statistically significant, and the incidence of testicular haploid cells decreased from 75.6% to 48.3% (p = 0.028). No significant change in any parameter was present in control dogs. The mean number of mature spermatids per cross-sectional tubule on final testicular histology was significantly decreased in spinal cord injured dogs compared with controls (13.6 versus 43.9, p = 0.02)., Conclusions: In the canine model tested the dogs readily survived spinal cord injury, electroejaculation was effective for obtaining ejaculate and fine needle aspiration allowed serial examination of spermatogenesis. Three weeks after spinal cord injury but not before 3 weeks sperm motility and spermatogenesis were significantly decreased. However, at the same point this decrease in spermatogenesis was not yet reflected in the total ejaculated sperm count.

Objective: Pedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques., Methods: During the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study., Results: Chart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (< or =2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4-T8, 16.7%; T1-T4, 8.8%; and T9-T12, 5.6%)., Conclusion: The low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.

Objective: The goal of this study was to determine the prognostic and clinical value of magnetic resonance imaging (MRI) performed within hours after cervical spinal cord injuries in human patients., Methods: Fifty-five patients with acute cervical vertebral column and spinal cord injuries underwent MRI as part of their initial treatment at the University of Michigan Medical Center. All images were obtained within 21 hours after injury (mean, 7.8 h) and were interpreted by an attending neuroradiologist who was blinded to the clinical status of the patients. Neurological function at presentation and in long-term follow-up examinations was compared with MRI characteristics assessed immediately after the injury., Results: The presence and rostrocaudal length of intra-axial hematoma, the rostrocaudal length of spinal cord edema, the presence of spinal cord compression, and spinal cord compression by extra-axial hematoma were each significantly associated with poor neurological function at presentation and in long-term follow-up examinations. Although the best single predictor of long-term improvement in neurological function was the neurological function at presentation, four MRI characteristics, i.e., the presence of intra-axial hematoma, the extent of spinal cord hematoma, the extent of spinal cord edema, and spinal cord compression by extra-axial hematoma, provided significant additional prognostic information. MRI data demonstrated spinal cord compression for 27 of 55 patients (49%), leading to emergency surgery. Among patients who underwent imaging after restoration of normal vertebral alignment using closed cervical traction, 13 of 26 (50%) underwent emergency surgery for treatment of persistent, MRI-demonstrated, spinal cord compression., Conclusion: Emergency MRI after spinal cord injury provides accurate prognostic information regarding neurological function and aids in the diagnosis and treatment of persistent spinal cord compression after vertebral realignment.

Object: Thrombotic complications (deep vein thrombosis and/or pulmonary embolization [DVT/PE]) occur in 18 to 50% of patients harboring brain tumors who undergo neurosurgical procedures. Such patients are at risk for DVT/PE because of immobility, paresis, hypovolemia, and lengthy surgery. The present study was undertaken to see whether tumor patients at highest risk for DVT/PE could be identified so that augmentation of prophylactic measures might be used to reduce the incidence of thrombotic complications., Methods: The authors conducted a retrospective analysis of 488 patients enrolled in their brain tumor registries between 1988 and 1995, identifying 57 patients (12%) with recorded symptomatic DVT, PE, or both postoperatively. In 24 of these 57 cases histological specimens were retrievable for review, allowing an in-depth analysis. Forty-five patients were lost to follow-up review, and the remaining 386 patients had no record of systemic thrombosis. Slides of pathological specimens were retrievable in 50 cases in which there was no DVT/PE. From these 50 cases, 25 were selected at random to represent the control group by a blinded observer. Seventeen (71%) of the 24 brain tumor specimens obtained in patients with DVT/PE stained positively for intraluminal thrombosis (ILT) after hematoxylin and eosin had been applied. The odds ratio associated with the presence of ILT was 17.8, with a confidence interval ranging from 4 to 79.3. No evidence of ILT was found in 22 patients (88%) within the control group (p < 0.0001, Fisher's exact test). Other factors that may predispose patients with brain tumors to DVT/PE-limb paresis, extent of tumor removal, and duration of the surgery-were also analyzed and found not to be statistically significant. Therefore, these factors were not the basis for differences seen between the study and control groups., Conclusions: These preliminary observations suggest that the presence of ILT within malignant glioma or glioblastoma tumor vessels may represent a marker of tumor-induced hypercoagulability.

Rationale and Objectives: The authors evaluated a method for obtaining reproducible, reliable measurements from standard lumbar spine radiographs for determining the degree of spondylolisthesis, vertebral body height, intervertebral disk space height, disk space angle, and degree of vertebral body wedging., Materials and Methods: Four to six easily defined points were identified on each vertebral body on anteroposterior and lateral plain radiographs of the lumbosacral spine of patients. From these points, the degree of spondylolisthesis, the vertebral body height, the intervertebral disk space height, the disk space angle, and the degree of vertebral body wedging were easily calculated by using well-known geometric relationships. This method requires the use of a personal computer and a standard spreadsheet program but does not require the use of any other specialized radiographic equipment, computer hardware, or custom software., Results: Calculations of intra- and interobserver variability for the measurement of spondylolisthesis, disk space height, disk space angle, and vertebral body height measurement showed that the technique is extremely reproducible., Conclusion: This technique may prove useful in the prospective evaluation of potential candidates for lumbar spinal stenosis surgery.

Study Design: Surgical spinal cable and wire fixation systems were tested mechanically using standardized methodologies., Objectives: To compare the relative mechanical properties and biomechanical performances of the different commercially available spinal wire and cable fixation devices, and to provide information that will help in selecting different cables for different clinical applications., Summary of Background Data: Spinal cables have become extensively used for spinal fixation; however, there are few published accounts delineating their mechanical properties. No reports have compared the relative properties of different cable systems., Methods: Nine spinal cable and wire fixation systems were mechanically tested to compare their static tensile strength, stiffness, fatigue strength, creep, conformance, and abrasion properties. Titanium and stainless steel Codman cable, Danek cable, and AcroMed cable, polyethylene Smith & Nephew cable, and 20- and 22-gauge stainless steel monofilament Ethicon wire were tested using identical methodologies. The cable or wire was connected into loops with methods that simulated in vivo clinical applications., Results: Under static tensile testing, titanium cables had 70% to 90% of the ultimate tensile strength of the comparable steel cables; the different cables were 100% to 600% stronger than monofilament wire; the ultimate strength of the polyethylene cable was similar to that of the strongest available steel cable. Fatigue testing delineated important differences among the different materials. For a given manufacturer, titanium cables were always more susceptible to fatigue than stainless steel cables of comparable diameter. Polyethylene cable withstood cyclical loading without breaking better than all of the metal cables and wires. The mechanisms of failure differed substantially among materials and types of tests. Polyethylene cables exhibited significant stretching or "creep" at loads that were much lower than the static failure loads. In contrast, no wire cable demonstrated creep. Monofilament wires demonstrated little creep. Polyethylene cables failed by elongating and loosening; wire cables failed by breaking. Monofilament wire and cables conformed least to a solid surface; polyethylene cable conformed the most and flattened out against solid surfaces. Abrasion properties depended on the surface characteristics of the implants. Polyethylene cable was abraded by (and eventually failed by wearing against) the simulated bone, a result that did not occur with any metal cables or wires. The steel and titanium cables and the monofilament wires all had an ability to abrade through simulated bone., Conclusions: Titanium, steel, and polyethylene cable systems all behave substantially differently mechanically compared with monofilament wire. The relative advantages and disadvantages of each particular products should be considered when selecting an implant for a specific clinical use.

The development and characterization of new receptor ligands for in vivo binding assays are often both lengthy and expensive. It is therefore desirable to predict the suitability of a ligand early in the process of its evaluation. In the present study, compartmental analysis following intracarotid ligand injection in the monkey is used to evaluate the in vivo kinetics of the muscarinic cholinergic receptor antagonists [11C]tropanyl benzilate ([11C]TRB) and [11C]N-methylpiperidyl benzilate ([11C]NMPB). Animals were implanted with chronic subcutaneous access ports and indwelling catheters with tips located in the common carotid artery, just proximal to its bifurcation. The external carotid artery was ligated to ensure selective tracer delivery through the internal carotid artery to the brain. Positron emission tomography was used to measure brain tissue time-activity curves following tracer injections. CBF was estimated from the clearance of [15O]H2O, and receptor ligand distributions were analyzed according to a physiologic model consisting of an intravascular compartment and nonspecific plus free and receptor-bound tissue ligand compartments. In [11C]TRB studies, marked reductions in the forward ligand-receptor binding rate and in both the total and the specific binding tissue-to-plasma volumes of ligand distribution were observed after scopolamine receptor blockade or with low administered specific activity. Conversely, neither the distribution volume of the nonspecific plus free ligand compartment nor the rate of ligand dissociation from receptor sites was affected. In [11C]NMPB studies, tissue compartments describing specific binding and nonsaturable components could not be reliably separated. The receptor-related term in this case, the total tissue-to-plasma distribution volume, demonstrated reduction after low specific activity ligand injection. Comparison of the two ligands suggests that NMPB interacts more rapidly with the receptors and has a lower apparent volume of distribution than does TRB. Thus, NMPB may be the more suitable ligand if accurate estimates of binding dissociation rate are limited by temporal constraints or if simplified, one-tissue-compartment analyses are used. The carotid injection method appears promising for the initial evaluation of ligand kinetics, permitting physiologic compartmental analyses without measurement of input functions or chromatography of blood samples.

Study Design: In a clinical retrospective study, the authors review long-term results of occipitocervical fusion using a wide diameter, contoured, threaded Steinmann pin., Objectives: To evaluate the clinical and radiographic results of occipitocervical fusion using this technique in a variety of abnormalities including rheumatoid arthritis. SUMMARY OF BACKGROUND DATA. The various surgical techniques and hardware developed for occipitocervical fusion have been associated with mixed results, particularly in patients with rheumatoid arthritis or basilar invagination., Methods: Thirty-nine patients with occipitocervical instability were internally fixed with a wide diameter, contoured, threaded Steinmann pin wired to the occiput and cervical laminae or facets. Fusion was facilitated using autologous iliac crest bone graft and a cervical orthosis. Instability resulted from rheumatoid arthritis (n = 12), congenital anomalies (n = 12), trauma (n = 10), tumor (n = 4), or osteogenesis imperfecta (n = 1). Fifteen patients had radiographic evidence of basilar invagination. Long-term outcome (mean follow-up period, 38.9 months; range, 12-78 months) was based on clinical and radiographic review., Results: Thirty-seven patients (97%) had a stable postoperative occipitocervical construct: there were 35 osseous unions, two fibrous unions, and one nonunion. There was on postoperative death from pulmonary complications. No patient developed evidence of new, recurrent, or progressive basilar invagination., Conclusion: The authors concluded that rigid segmental fixation of the craniovertebral junction using a wide diameter, contoured, threaded Steinmann pin and supplemental autograft creates excellent fusion with minimal complications. This technique is appropriate for a variety of abnormalities including rheumatoid arthritis.

Segmental spinal fixation using sublaminar or interspinous stainless steel wire has been successfully used for many years. Stainless steel cables have been developed that are stronger and more flexible, allowing for shorter operative time and decreased risk of neurological deficit. However, stainless steel implants create significant artifact on magnetic resonance imaging (MRI), reducing the postoperative usefulness of this imaging modality. Titanium instrumentation has the advantage of producing minimal MRI artifact. Recently, a braided titanium cable has been developed that has the advantages of strength and flexibility as well as minimal production of MRI artifact. We present a series of 50 patients who underwent internal fixation of the spine using a braided titanium cable either alone or in combination with supplementary titanium instrumentation. No instrument failures have occurred to date. Postoperative MRI scans have revealed minimal implant-related artifact, allowing for high-resolution, noninvasive postoperative imaging of the neuraxis. We conclude that braided titanium cable has significant advantages over stainless steel cable or monofilament wire and is a valuable instrument for segmental spine fixation.

Endothelium-dependent vasodilatation to acetylcholine is abnormal in animal models of hypertension. This abnormality reflects a change in the balance of relaxing and contracting factors produced in the vascular wall. In human cerebral arteries, endothelin has been implicated in the abnormal vasoconstrictor response following subarachnoid hemorrhage. This study tests the hypothesis that cerebral arteriolar dilatation to acetylcholine reduced in clinical hypertension due to an overproduction of endothelin. Our results show that at high concentrations of muscarinic agonist (0.3-3 microM), human vertebral arteries from hypertensive patients contract whereas those from normotensive patients remain maximally dilated. We conclude that the normal dilator response to acetylcholine is abrogated in vertebral arteries from treated hypertensive patients but endothelin-1 does not contribute to the abnormal responsiveness.

The myelographic, CT, and MR findings of a rare localized primary bone amyloidoma causing upper thoracic spinal cord compression are presented. Imaging showed a large, calcified mass centered in the posteromedial portion of the left second rib that invaded the second thoracic vertebra and the spinal canal.

A 50-year-old man with myelopathy secondary to basilar impression developed bilateral vertebral artery dissection after undergoing treatment with 8 pounds of cervical traction. The vertebral artery dissection resulted in vertebrobasilar insufficiency and posterior circulation stroke. In this report, the current management philosophies in the treatment of basilar impression are discussed, and the pertinent neurovascular anatomy is illustrated. This report suggests that vertebral artery injury may result from attempted reduction of severe basilar impression. Regardless of the cause of cranial settling, the risk of vertebral artery injury with cervical traction should be considered in patients with severe basilar impression.

Four human astrocytic gliomas of high grade of malignancy were each evaluated in tissue and in vitro for percentages of cells expressing glial fibrillary acidic protein (GFAP), collagen type IV, laminin and fibronectin assessed by immunofluorescence with counterstaining of nuclear DNA. Percentages of cells with reticulin and cells binding fluorescein-labeled Ulex europaeus agglutinin were also assessed. In tissue, each extracellular matrix (ECM) component was associated with cells in the walls of abnormal proliferations of glioma vessels, and all four tumors had the same staining pattern. Two strikingly different patterns of conversion of gene product expression emerged during in vitro cultivation. (1). In the most common pattern, percentages of all six markers consistently shifted toward the exact phenotype of mesenchymal cells in abnormal vascular proliferations: increased reticulin, collagen type IV, laminin and fibronectin; markedly decreased glial marker GFAP and absent endothelial marker Ulex europaeus agglutinin. The simplest explanation of this constellation of changes coordinated toward expression of vascular ECM markers is that primary glioma cell cultures are overgrown by mesenchymal cells from the abnormal vascular proliferations of the original glioma. These cell cultures were tested for in situ hybridization (ISH) signals of chromosomes 7 and 10. Cells from one glioma had diploid signals. Cells from the other glioma had aneuploid signals indicating they were neoplastic; however, their signals reflected different numerical chromosomal aberrations than those common to neoplastic glia. (2). The second pattern was different. Cells with ISH chromosomal signals of neoplastic glia retained GFAP, and gained collagen type IV. Their laminin and fibronectin diminished, but persisted among a lower percentage of cells. Cloning and double immunofluorescence confirmed the presence of individual cells with glial and mesenchymal markers. A cell expressing GFAP in addition to either fibronectin, reticulin or collagen type IV is not a known constituent of glioblastoma tissue. This provides evidence of a second mechanism of conversion of gene expression in gliomas.

All patients who underwent decompressive lumbar laminectomy in the Washtenaw County, Michigan metropolitan area during a 7-year period were studied for the purpose of defining long-term outcome, clinical correlations, and the need for subsequent fusion. Outcome was determined by questionnaire and physical examination from a cohort of 119 patients with an average follow-up evaluation interval of 4.6 years. Patients graded their outcome as much improved (37%), somewhat improved (29%), unchanged (17%), somewhat worse (5%), and much worse (12%) compared to their condition before surgery. Poor outcome correlated with the need for additional surgery, but there were few additional significant correlations. No patient had a lumbar fusion during the study interval. The outcome after laminectomy was found to be less favorable than previously reported, based on a patient questionnaire administered to an unbiased patient population. Further randomized, controlled trials are therefore necessary to determine the efficacy of lumbar fusion as an adjunct to decompressive lumbar laminectomy.

The pre- and postoperative lumbar spine radiographs of 119 patients who underwent decompressive lumbar laminectomy were studied to evaluate radiographic changes and to correlate them with clinical outcome. An accurate and reproducible method was used for measuring pre- and postoperative radiographs that were separated by an average interval of 4.6 years. Levels of the spine that underwent laminectomy showed greater change in spondylolisthesis, disc space angle, and disc space height than unoperated levels. Outcome correlated with radiographic changes at operated and unoperated levels. This study demonstrates that radiographic changes are greater at operated than at unoperated levels and that some postoperative symptoms do correlate with these changes. Lumbar fusion should be considered in some patients who undergo decompressive laminectomy. The efficacy of and unequivocal indications for lumbar fusion can only be determined from randomized, prospective, controlled trials, however, and these studies have not yet been undertaken.

The type II odontoid fracture, initially described by Anderson and D'Alonzo, is the most common axis fracture. Several factors that predict the need for operative intervention have been discussed in the literature; however, the initial treatment remains somewhat controversial. We present the case of a 20-year-old woman who suffered a Type II odontoid fracture during a skiing accident. She was managed initially with halo-vest immobilization, and after 12 weeks, bony fusion was documented by plain spine radiographs and tomography. Routine follow-up cervical spine films at 8 months after her injury revealed no union at the previous fracture site and resultant atlantoaxial instability. A posterior C1-C2 fusion was therefore performed, leading to a long-term solid bony fusion. There are no previous reports in the literature describing a nonunion after radiographically documented healing of a Type II odontoid fracture. We present this case in order to emphasize the importance of scheduled follow-up examinations, including cervical spine films, for at least 12 months after a documented fusion. Further reports of similar cases may generate a more thorough understanding of the pathogenesis of delayed nonunion and may elicit factors that will predict its development.

Contractions to serotonin (5-HT) and endothelin-1 (ET-1) in infant (0-2 yr) and adult (38-71 yr) vertebral arteries were examined in the presence of either the cyclooxygenase inhibitor indomethacin or NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide production. In addition, endothelium-dependent relaxations to acetylcholine were characterized in arteries contracted with agonist. The results showed that: (a) Contractions of infant arteries to 5-HT or ET-1 decreased to 44 +/- 8% and 27 +/- 13%, respectively, within 10 min. Indomethacin or removal of endothelium abolished this decreased response, whereas L-NMMA had no effect. (b) Adult arteries produced sustained contractions to 5-HT or ET-1 that were unaffected by indomethacin, endothelium denudation, or L-NMMA. (c) Endothelium-dependent relaxations to acetylcholine were greater in infant than adult arteries and were abolished by indomethacin (but not L-NMMA) in infants and L-NMMA (but not indomethacin) in adults. Thus, endothelium-dependent responses in infant arteries are attenuated because of increased prostaglandin activity not observed in adult tissues. Additionally, there is an age-dependent change in the primary mechanism responsible for acetylcholine-induced vasodilation. Apparently, endothelium dependency of acetylcholine-induced relaxation is highly dependent on cyclooxygenase activity in the infant vertebral artery, but in the adult artery, nitric oxide is linked to the vasodilator response.

Metastatic epidural spinal cord compression (MESCC) is a medical emergency complicating the course of 5-10% of patients with cancer [1]. When diagnosis and treatment is early with the patient ambulatory prognosis for continued ambulation is good [2]. If the patient is nonambulatory or paraplegic, prognosis for meaningful recovery of motor and bladder function is markedly decreased. In the last decade, significant advances in the understanding, management and treatment of metastatic epidural spinal cord compression have occurred. Recent pathophysiological and pharmacological animals studies have afforded insights into disease mechanisms [3-9]. The audit of standard methods of investigation and magnetic resonance imaging have resulted in revision of guidelines for patient evaluation [10-17]. Finally, new surgical philosophies and technical advances have generated interest and controversy [18-25]. With improved clinical awareness, new imaging modalities will help us diagnose epidural spinal cord compression earlier and institute appropriate treatment.

The authors report the resolution of essential hypertension following transoral odontoidectomy and medullary decompression in a 39-year-old woman with basilar invagination. Current understanding of central regulation of the cardiovascular system is discussed and the pertinent neuroanatomy illustrated. Experimental and clinical evidence supporting the role of neurogenic mechanisms in the pathogenesis of hypertension is reviewed.

The coexistence of traumatic locked facets of the cervical spine and a herniated disc is not well described. The authors present a series of patients with traumatic locked facets who demonstrated a high incidence of associated disc herniation documented on magnetic resonance (MR) imaging. Thirteen patients with either unilateral (four cases) of bilateral (nine cases) locked facets of the cervical spine were analyzed retrospectively. Immediate closed reduction using traction and/or manipulation was attempted in the first nine cases treated and was successful in only three; however, the procedure was abandoned in three cases due to deterioration in the patient's clinical status. In the subsequent four patients, an MR image was obtained prior to attempts at closed reduction. All patients underwent MR imaging of the cervical spine. Of eight consecutive cases treated at the University of Michigan, frank disc herniation with fragmented disc in the canal was found in five while pathological disc bulging was found in the other three. All five cases contributed by other institutions had concurrent disc herniation. This series illustrates the importance of using MR imaging to document the presence of a herniated disc during the initial evaluation of a patient with traumatic locked facets of the cervical spine and prior to attempted reduction of the locked facets. Experience indicates that closed reduction of facet dislocation associated with disc rupture may result in increased spinal cord compression and neurological deficit. If a herniated disc is discovered, anterior discectomy and fusion would be favored as the initial therapy over attempts at closed reduction or operative posterior reduction.

Fourteen occipitoatlantal dislocations were treated during an 11-year period. All patients presented with neurological deficits and definite evidence of spinal instability. Plain radiographs provided the diagnosis conclusively in 11 patients. Three patients required computed tomography (CT) or magnetic resonance (MR) imaging for diagnosis. Rotational subluxations were radiographically occult and associated with less severe neurological injuries compared to distracted or translated subluxations. Ten patients died acutely. One patient, who had complete C1 level quadriplegia, died after 3 months. Three patients with incomplete spinal cord syndromes had long-term survival and functional neurological recoveries. Extensive ligamentous injury predisposed patients to recurrent subluxations. In several patients, traction or a cervical collar caused distraction and neurological injury. Halo immobilization and urgent fusion are necessary for patients with salvageable neurological function. Nonoperative measures are inadequate for immediate or long-term spinal stability.

Patients with symptomatic lumbar disk disease may present with back pain, referred leg pain, radicular leg pain, sensory changes and leg weakness. Because neurologic deficits are commonly localized to the L5 or S1 nerve roots, evaluation of patients with such symptoms should focus on these dermatomes and muscle groups. Myelography, computed tomography, postmyelogram computed tomography and magnetic resonance imaging are the most valuable diagnostic studies. Initial management consists of physical therapy and reduced activity, followed by gradually increasing mobilization and exercise. Conservative treatment is effective for most patients. Surgical treatment is reserved for patients who have failed to improve with conservative therapy or those who present with a profound neurologic deficit. Prevention of recurrent symptoms centers on patient education and reassurance. A program of weight control, regular exercise and posture correction may reduce the frequency and severity of recurrent disk herniation and pain.

We report in vitro and in vivo preclinical studies of a new cerebral blood flow tracer, [99mTc]N1-(2-mercapto-2-methyl-propyl)-N2-(2- propargylthio-2-methylpropyl)-1,2-benzenediamine (T691). The tracer demonstrates excellent in vitro chemical stability and accumulates regionally in the brain in a pattern consistent with that of cerebral blood flow. First-pass cerebral extraction determined with the use of the brain uptake index method in the rat was 0.76. Bolus intracarotid injection in monkeys indicated a cerebral extraction of 68% and prolonged retention of 67% of the initially extracted activity. Autoradiographic studies in rats revealed a pattern characteristic of cerebral blood flow at both 1 and 60 min after systemic injection. Dynamic tomographic imaging following systemic injection in the monkey revealed peak brain activity 1 to 2 min postinjection, without significant decline over 60 min. Chromatographic studies of brain as long as 60 min following systemic injection of [99mTc]T691 showed no evidence of tracer metabolism to account for its retention. Overall, [99mTc]T691 demonstrates promise as a potential new clinical tracer of cerebral perfusion.

Continued investigation of the pathophysiology of primary and secondary neuronal injury following acute spinal cord injury (SCI) has led to positive results in two medical treatment protocols: methylprednisolone and GM1 ganglioside. The advent of improved high resolution radiologic studies has allowed a new dimension in the understanding of the physical and pathomechanical aspects of acute SCI. Advances in rehabilitation continue, allowing improved prognosis and long-term function. Prevention is clearly the best and most effective treatment of all.

This report details our recent experience with the surgical treatment of complex hangman's fractures after failure of closed reduction and immobilization in external orthosis. We have successfully treated hangman's fractures in 5 patients with anterior Caspar plate stabilization and C2-C3 interbody fusion. The specific anatomical features of these fractures were complex, rendering the spines of the patients highly unstable. The patients were considered surgical candidates when reduction could not be achieved or maintained with axial traction or halo immobilization. Each patient underwent anterior C2-C3 interbody bone fusion and Caspar plating from C2 to C3. All patients achieved adequate intraoperative reduction and were immobilized postoperatively with a halo vest. The follow-up period ranged from 3 to 28 months and provided a 100% fusion rate with no complications related to plating or nonunion. Our initial experience indicates that anterior C2-C3 interbody bone fusion and Caspar plate fixation is a suitable treatment option for patients with complex hangman's fractures who are not successfully managed nonoperatively.

Spinal cord astrocytomas are rare lesions, usually of low grade, with a long natural history. Because of this, it is difficult to define the optimum approach to therapy based on available data. To provide more data, a retrospective review was performed. From 1975 through 1989, 21 patients were seen and treated (median age, 21 years), and 15 patients received radiation therapy after undergoing either biopsy or resection. The median time until death or the last follow-up examination was 41 months. The actuarial survival of all patients was 68% at 5 years. Of the five deaths, four were related to local tumor recurrence. The overall survival and recurrence-free survival of irradiated patients at 5 years was 57% and 44%, respectively. The age of the patient was a prognostic factor, with younger patients surviving substantially longer before recurrence. Of the 15 irradiated patients, 7 experienced recurrence of the tumor, which occurred within the irradiated portion of the spinal cord in all 7. Gross total resections were rarely achieved and, also, the extent of resection did not influence the risk for recurrence. In summary, we observed a long natural history for this disease, and although additional local therapy appears needed, it is unclear that either higher doses of radiation or more extensive surgery will decrease the risk of recurrence.

In response to several agonists, tail arteries from spontaneously hypertensive stroke prone rats (SHRSP) contract in an oscillatory manner not observed in tail arteries from normotensive rats. This study evaluated whether oscillations in force development characterize the contractile pattern of vertebral arteries from hypertensive humans. Vertebral arteries were isolated and studied within 18-24 h post mortem. Helical strips of the arteries were mounted in a muscle bath for isometric force recording. Contractile responses to serotonin (10(-7)M) and endothelin (10(-8)M) in arteries from hypertensive subjects were characterized by fluctuations in force development whereas those in arteries from normotensive subjects usually remained constant with time. The frequency of the response was approximately 1-2 contraction/relaxation cycles per min. This pattern of oscillatory contractile activity was observed in all but one of the hypertensive arteries (n = 15), and in approximately 40% of the normotensive arteries (n = 12). Oscillatory activity was converted to maintained contraction by nifedipine (10(-7)M) which also caused relaxation of the contractile response. Relaxation to acetylcholine (10(-6)M) and nitroglycerin (10(-6)M) did not alter the oscillatory contractions. Endothelium removal did not influence the oscillatory pattern of contraction. These observations suggest that oscillatory contractile activity in vertebral arteries from hypertensive subjects is related to abnormal calcium entry into the smooth muscle cells. This altered membrane property may contribute to changes in vascular reactivity in hypertension.

It is important to remember that ESCC is a complication of systemic malignancy and usually denotes disseminated disease with poor survival rates. Early diagnosis is crucial. The initial symptom is almost always back pain, which is local, radicular, or both. Following neurologic examination and radiography, MRI scanning or myelography/CT is immediately indicated if radiculopathy or myelopathy is present or if the radiographs of the spine are abnormal. In cancer patients with local back pain and normal findings on neurologic examination and radiography of the spine, there is still a probability of 0.1 of significant ESCC. Therefore, urgent CT/MRI scanning is justified. At present, the best treatment for ESCC remains unknown. In the majority of patients, radiotherapy is the most readily available and appropriate option because it is equal in effect to posterior decompressive laminectomy in both radiosensitive and radioresistant tumors. In patients with posterior epidural disease without tissue diagnosis, laminectomy with or without stabilization should be performed. Posterior decompressive laminectomy alone is contraindicated in patients with vertebral collapse. In selected instances of anterior epidural compression without tissue diagnosis or after failure of radiotherapy, an anterior surgical approach or synchronous vertebral decompression with posterior stabilization may be indicated. In the future, after appropriate clinical trials, vertebral body resection may be the optimal approach in de novo selected patients with ESCC with radioresistant tumors and limited systemic spread of the disease.

Recent laboratory studies have demonstrated that intracisternal administration of recombinant tissue plasminogen activator (rt-PA) can facilitate the normal clearing of blood from the subarachnoid space and prevent or ameliorate delayed arterial spasm. The results of a preliminary Phase I trial of intracisternal rt-PA in 10 patients are reported with documented aneurysmal subarachnoid hemorrhage (SAH). All patients enrolled were classified as clinical Grade III or IV (according to Hunt and Hess) with thick clots or layers of blood in the basal cisterns and major cerebral fissures (Fisher Grade 3). Ventriculostomy and surgery for clipping of the aneurysms were performed within 48 hours of hemorrhage. In one patient, 10 mg rt-PA was instilled into the subarachnoid cisterns prior to closing the dura. In the remaining nine patients, a small silicone catheter was left in the subarachnoid space and rt-PA (5 mg in four cases or 1.5 mg (0.5 mg every 8 hours for three infusions) in five cases) was instilled 12 to 24 hours after surgery. Minor local bleeding complications were noted in all patients receiving 5 or 10 mg rt-PA. Oozing was noted at the operative incision site in four of five patients and at the ventriculostomy site in two patients. One patient developed a small epidural hematoma that was treated by delayed drainage. No bleeding complications were noted in the patients receiving the lower regimen of rt-PA (three infusions of 0.5 mg each). Serial coagulation studies demonstrated no evidence of systemic fibrinolysis. Analysis of cisternal cerebrospinal fluid samples revealed thrombolytic tissue plasminogen activator (t-PA) levels for 24 to 48 hours. Follow-up cerebral angiography 7 to 8 days after rupture disclosed mild to moderate spasm in nine patients, while one patient with hemorrhage from a posterior inferior cerebellar artery aneurysm had severe focal spasm of the vertebral arteries that was not symptomatic. These results suggest that postoperative treatment with rt-PA may be effective in reducing the severity of delayed cerebral vasospasm. The results of serial t-PA levels suggest that the lower dosage regimen with divided dosages at 8-hour intervals is well tolerated and that even lower dosages may be effective. Further studies are clearly indicated.