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Object: Stabilization of the craniocervical junction (CCJ) remains a significant challenge. In this multicenter study, the authors present the results of an evaluation of a precontoured titanium implant, the Ohio Medical Instruments (OMI) Loop, for craniocervical fixation., Methods: In this multicenter retrospective study the authors evaluated 30 patients (16 female, 14 male; mean age 53.8 years) with rheumatoid arthritis (15 cases), traumatic occipitoatlantoaxial instability (six cases), congenital vertebral anomalies (two cases), instability due to basilar invagination in the setting of Chiari malformation (two cases), or Down syndrome (one case), tumor (one case), os odontoideum (two cases), and pseudarthrosis/other (one case), who underwent OMI Loop-assisted occipitocervical reconstruction. The mean follow-up period was 25.4 months (range 6-60 months). A solid reconstruction was achieved in 29 of 30 cases; there was only one case of hardware failure requiring reoperation. Noncritical hardware failure occurred in two patients in whom partial occipital screw backout occurred but did not necessitate reoperation. There were no perioperative neurological complications. One patient (3.3%) experienced a delayed postoperative worsening of myelopathy at 1 year that resolved with further surgery. Postoperatively, in 66.6% of patients the degree of myelopathy remained stable (as measured by American Spinal Injury Association [ASIA] scores), whereas 30% improved by one or more ASIA grade. The rate of osseous fusion was 96.6% at a mean follow-up period of 25.4 months., Conclusions: The authors found that the OMI Loop is a versatile precontoured occipitocervical fixation device that can be applied to a wide range of CCJ lesions. It provides excellent immediate rigid fixation of the CCJ, a high rate of osseous fusion, and a low rate of hardware failure.

Transoral decompression of the cervicomedullary junction may be compromised by a narrow corridor in which surgery is performed, and thus the adequacy of surgical decompression/resection may be difficult to determine. This is problematic as the presence of spinal instrumentation may obscure the accuracy of postoperative radiological assessment, or the patient may require reoperation. The authors describe three patients in whom high-field intraoperative magnetic resonance (MR) images were acquired at various stages during the transoral resection of C-2 disease that had caused craniocervical junction compression. All three patients harbored different lesions involving the cervicomedullary junction: one each of plasmacytoma and metastatic breast carcinoma involving the odontoid process and C-2 vertebral body, and basilar invagination with a Chiari I malformation. All patients presented with progressive myelopathy. Surgical planning MR imaging studies performed after the induction of anesthesia demonstrated the lesion and its relationship to the planned surgical corridor. Transoral exposure was achieved through placement of a Crockard retractor system. In one case the soft palate was divided. Interdissection MR imaging revealed that adequate decompression had been achieved in all cases. The two patients with carcinoma required placement of posterior instrumentation for stabilization. Planned suboccipital decompression and placement of instrumentation were averted in the third case as the intraoperative MR images demonstrated that excellent decompression had been achieved. Intraoperatively acquired MR images were instrumental in determining the adequacy of the decompressive surgery. In one of the three cases, examination of the images led the authors to change the planned surgical procedure. Importantly, the acquisition of intraoperative MR images did not adversely affect operating time or neurosurgical techniques, including instrumentation requirements.

Object: Since publication in 1990, results from the National Acute Spinal Cord Injury Study II (NASCIS II) trial have changed the way patients suffering an acute spinal cord injury (SCI) are treated. More recently, recommendations from NASCIS III are being adopted by institutions around the world. The purpose of this paper is to reevaluate carefully the results and conclusions of these studies to determine the role they should play in influencing decisions about care of the acutely spinal cord-injured patient., Methods: Published results from NASCIS II and III were reviewed in the context of the original study design, including primary outcomes compared with post-hoc comparisons. Data were retroconverted from tabular form back to raw form to allow direct inspection of changes in treatment groups. These findings were further analyzed with respect to justification of practice standards. Although well-designed and well-executed, both NASCIS II and III failed to demonstrate improvement in primary outcome measures as a result of the administration of methylprednisolone. Post-hoc comparisons, although interesting, did not provide compelling data to establish a new standard of care in the treatment of patients with acute SCI., Conclusions: The use of methylprednisolone administration in the treatment of acute SCI is not proven as a standard of care, nor can it be considered a recommended treatment. Evidence of the drug's efficacy and impact is weak and may only represent random events. In the strictest sense, 24-hour administration of methylprednisolone must still be considered experimental for use in clinical SCI. Forty-eight-hour therapy is not recommended. These conclusions are important to consider in the design of future trials and in the medicolegal arena.

Object: Pain control can often be improved by local (as opposed to systemic) application of analgesic and/or anesthetic medication. The purpose of this study was to evaluate the efficacy of a single-dose epidural analgesic "paste" in the control of postoperative pain in patients who have undergone lumbar decompressive surgery., Methods: Sixty patients undergoing routine elective lumbar decompressive surgery were randomized in a double-blind fashion to one of two groups: those receiving active paste or placebo paste. The paste was applied to the exposed dura at the time of surgery, just prior to wound closure. Patients received follow-up care in the hospital and at home for 3 months postsurgery. Several outcome measures were studied to ascertain differences in pain control and to ensure comparability between groups. Patients who received active paste demonstrated significantly lower pain scores compared with those who received placebo paste for up to 6 weeks postoperatively. General health perception indexed by the Short Form 36 was also significantly better in patients who received active paste for up to 6 weeks. In-hospital and outpatient oral narcotic consumption was significantly lower in the active paste-treated group. Inpatient straight leg raising scores were improved in those patients who received active compared with control paste., Conclusions: Application of an analgesic paste directly to the epidural space during lumbar decompressive surgery significantly improves postoperative pain control, reduces prescribed analgesic drug consumption, and improves overall health perception for up to 6 weeks following surgery. The authors conclude that this postoperative pain control strategy is both effective and safe and may provide a new standard of pain management in patients undergoing lumbar discectomy or laminectomy.

Object: The purpose of this study was to compare cable techniques used in occipitocervical fixation with two types of screw fixation. The authors hypothesized that screw fixation would provide superior immobilization compared with cable methods., Methods: Ten cadaveric specimens were prepared for biomechanical analyses by using standard techniques. Angular and linear displacement data were recorded from the occiput to C-6 with infrared optical sensors after conditioning runs. Specimens underwent retesting after fatiguing. Six methods of fixation were analyzed: Steinmann pin with and without C-1 incorporation; Cotrel-Dubousett horseshoe with and without C-1 incorporation; Mayfield loop with C1-2 transarticular screw fixation; and a custom-designed occipitocervical transarticular screw-plate system. Sublaminar techniques were extended to include C-3 in the fusion construct, whereas transarticular techniques incorporated the occiput, C-1, and C-2 only. All methods of fixation provided significant immobilization in all specimens compared with the nonconstrained destabilized state. Despite incorporation of an additional vertebral segment, sublaminar techniques performed worse as a function of applied load than screw fixation techniques. Following fatiguing, these differences were more pronounced. The sublaminar techniques failed most prominently in flexion-extension and in axial rotation. On gross inspection, increased angular displacement associated with loosening of the sublaminar cables was observed., Conclusion: Occipitocervical fixation can be performed using a variety of techniques; all bestow significant immobilization compared with the destabilized spine. All methods tested in this study were susceptible to fatigue and loss of reduction and were weakest in resisting vertical settling. Screw fixation of the occiput-C2 reduces the number of vertebral segments that are necessary to incorporate into the fusion construct while providing superior immobilization and resistance to fatigue and vertical settling compared with sublaminar methods.

This 44-year-old man presented with a 4-year history of progressive spastic weakness of his legs. He was found to have epidural lipomatosis behind the thoracic spinal cord, and the nerve roots exited from the posterior and anterior midline planes of the dura, indicating a 90 degree rotation of the thoracic cord. Magnetic resonance images clearly demonstrated the segmental thoracic nerve roots exiting from the dorsal midline of the dura, a finding confirmed at surgery. The authors found only one previously published case of rotation of the spinal cord. Directed mechanical stress caused by deformation of the rotated spinal cord, rather than compression from adipose tissue, is proposed as the mechanism of the myelopathy. The extent, location, and thickness of the associated extradural adipose tissue is suggestive of epidural lipomatosis. The lipomatous tissue might have been an epiphenomenon and cord rotation an isolated congenital anomaly. Alternatively, asymmetrical growth of epidural fat may have exerted torque, rotating the thecal sac.

Electrical stimulation of the mammalian central nervous system (CNS) can result in extensive destruction of tissue unless applied within specific stimulation parameters. Classically, unbalanced or monopolar currents have been avoided in order to minimize these harmful effects. However, direct current (DC) fields have recently been proposed for the treatment of spinal cord injury. Until now, no rigorous analysis has been made of the safety of these fields in the mammalian CNS. The purpose of this study was to determine the amount of chronically applied DC current that can be tolerated by the normal rodent spinal cord stimulated with metal disc electrodes. Thirty-five normal rats underwent implantation of DC stimulating devices and were allowed to recover for a period of 2 to 12 weeks. The stimulators delivered constant currents of 0 to 50 microA through two disc-shaped platinum/iridium electrodes positioned extradurally at the C-7 and T-3 levels. Following sacrifice of the animals, serial 8-microns cross sections of the spinal cord at the electrode sites were examined microscopically. Evidence of demyelination presumed due to the physical presence of the rostral electrode was seen in animals from most groups including control animals. Pathological changes directly attributable to the applied fields were seen with current as low as 3 microA. It was concluded that DC's of 3 microA or more are harmful to the mammalian CNS with this method of stimulation. In addition, the data suggest that the maximum current density tolerated by the rodent spinal cord is in the order of 75 microA/sq cm. These findings have important implications for the use of chronic DC stimulation in the mammalian CNS.

Although the assessment of spinal cord function by electrophysiological techniques has become important in both clinical and research environments, current monitoring methods do not completely evaluate all tracts in the spinal cord. Somatosensory and motor evoked potentials primarily reflect dorsal column and pyramidal tract integrity, respectively, but do not directly assess the status of the ventral funiculus. The present study was undertaken to evaluate the use of evoked potentials, elicited by direct cerebellar stimulation, in monitoring the ventral component of the rodent spinal cord. Twenty-nine rats underwent epidural anodal stimulation directly over the cerebellar cortex, with recording of evoked responses from the lower thoracic spinal cord, both sciatic nerves, and/or both gastrocnemius muscles. Stimulation parameters were varied to establish normative characteristics. The pathways conducting these "posterior fossa evoked potentials" were determined after creation of various lesions of the cervical spinal cord. The evoked potential recorded from the thoracic spinal cord consisted of five positive (P1 to P5) and five negative (N1 to N5) peaks. The average conduction velocity (+/- standard deviation) of the earliest wave (P1) was 53 +/- 4 m/sec, with a latency of 1.24 +/- 0.10 msec. The other components followed within 4 msec from stimulus onset. Unilateral cerebellar stimulation resulted in bilateral sciatic nerve and gastrocnemius muscle responses; there were no significant differences (p greater than 0.05) in the thresholds, amplitudes, or latencies of these responses elicited by right- versus left-sided stimulation. Recordings performed following creation of selective lesions of the cervical cord indicated that the thoracic response was carried primarily in the ventral funiculus while the sciatic and gastrocnemius responses were mediated through the dorsal half of the spinal cord. It is concluded that the posterior fossa evoked potential has research value as a method of monitoring pathways within the ventral spinal cord of the rat, and should be useful in the study of spinal cord injury.