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Christopher B Shields

Publications and source records attributed to Christopher B Shields.

18 recordsLinked to original sources
PubMed2006

Adverse effects associated with high-dose recombinant human bone morphogenetic protein-2 use in anterior cervical spine fusion.

STUDY DESIGN: A retrospective review of patients who underwent an anterior cervical fusion using recombinant human bone morphogenetic protein (rhBMP)-2 with an absorbable collagen sponge (INFUSE; Medtronic Sofamor Danek, Minneapolis, MN). OBJECTIVE: To ascertain the complication rate after the use of high-dose INFUSE in anterior cervical fusions. SUMMARY OF BACKGROUND DATA: The rhBMP-2 has been primarily investigated in lumbar spine fusions, where it has significantly enhanced the fusion rate and decreased the length of surgery, blood loss, and hospital stay. METHODS: We present 151 patients who underwent either an anterior cervical discectomy and fusion (n = 138) or anterior cervical vertebrectomy and fusion (n = 13) augmented with high-dose INFUSE between July 2003 and March 2004. The rhBMP-2 (up to 2.1 mg/level) was used in the anterior cervical discectomy and fusions. RESULTS: A total of 35 (23.2%) patients had complications after the use of high-dose INFUSE in the cervical spine. There were 15 patients diagnosed with a hematoma, including 11 on postoperative day 4 or 5, of whom 8 were surgically evacuated. Thirteen individuals had either a prolonged hospital stay (> 48 hours) or hospital readmission because of swallowing/breathing difficulties or dramatic swelling without hematoma. CONCLUSIONS: A significant rate of complications resulted after the use of a high dose of INFUSE in anterior cervical fusions. We hypothesize that in the cervical area, the putative inflammatory effect that contributes to the effectiveness of INFUSE in inducing fusion may spread to adjacent critical structures and lead to increased postoperative morbidity. A thorough investigation is warranted to determine the optimal dose of rhBMP-2 that will promote cervical fusion and minimize complications.

Adult↗
PubMed2006

A novel role of phospholipase A2 in mediating spinal cord secondary injury.

OBJECTIVE: To investigate whether phospholipase A2 (PLA2) plays a role in the pathogenesis of spinal cord injury (SCI). METHODS: Biochemical, Western blot, histological, immunohistochemical, electron microscopic, electrophysiological, and behavior assessments were performed to investigate (1) SCI-induced PLA2 activity, expression, and cellular localization after a contusive SCI; and (2) the effects of exogenous PLA2 on spinal cord neuronal death in vitro and tissue damage, inflammation, and function in vivo. RESULTS: After SCI, both PLA2 activity and cytosolic PLA2 expression increased significantly, with cytosolic PLA2 expression being localized mainly in neurons and oligodendrocytes. Both PLA2 and melittin, an activator of endogenous PLA2, induced spinal neuronal death in vitro, which was substantially reversed by mepacrine, a PLA2 inhibitor. When PLA2 or melittin was microinjected into the normal spinal cord, the former induced confined demyelination and latter diffuse tissue necrosis. Both injections induced inflammation, oxidation, and tissue damage, resulting in corresponding electrophysiological and behavioral impairments. Importantly, the PLA2-induced demyelination was significantly reversed by mepacrine. INTERPRETATION: PLA2, increased significantly after SCI, may play a key role in mediating neuronal death and oligodendrocyte demyelination following SCI. Blocking PLA2 action may represent a novel repair strategy to reduce tissue damage and increase function after SCI.

Aldehydes↗
PubMed2006

Objective assessment of cervical spinal cord injury levels by transcranial magnetic motor-evoked potentials.

BACKGROUND: The neurologic examination serves as the optimal method to record the level of spinal cord injury (SCI). However, this test is subject to interexaminer variability. To address this shortcoming, we describe a technique that uses transcranial magnetic motor-evoked potentials (tcMMEPs) and dermatomal somatosensory-evoked potentials (d-SSEPs) to more accurately measure the precise level of SCI. METHODS: Two groups of subjects were studied: (1) complete cervical SCI (n = 10) and (2) neurologically intact volunteers (n = 10). Two additional patients were evaluated: one with a cervical central spinal cord syndrome and another with a head injury with a suspected cervical SCI. Each subject underwent upper extremity tcMMEPs and d-SSEPs. RESULTS: Transcranial magnetic motor-evoked potentials were elicited from all upper limb myotomes (C4-T1, bilaterally) in neurologically intact volunteers (20 sides). The level of injury was determined using tcMMEPs by observing the lowest level of measurable response. The level of injury obtained using tcMMEPs was the same as that determined by neurologic examination in 13 (65%) of the 20 sides. In 7 sides, tcMMEP responses were obtained 1 level lower than that assessed by physical examination. Dermatomal somatosensory-evoked potentials were obtained from all dermatomes of volunteers tested in the laboratory compared with only 5 of the 9 patients with SCI who underwent d-SSEP testing. CONCLUSION: Testing using tcMMEPs provides an objective supplement to the neurologic examination after acute cervical SCI. Dermatomal somatosensory-evoked potentials were of limited value in determining the level of cervical SCI.

Adolescent↗
PubMed2006

Dural repair reduces connective tissue scar invasion and cystic cavity formation after acute spinal cord laceration injury in adult rats.

This study examined whether duraplasty after acute cervical laceration spinal cord injury (SCI) in a rat model could (1) improve cerebrospinal fluid (CSF) circulation adjacent to the injury; (2) minimize connective tissue scarring; and (3) reduce post-traumatic inflammation and cystic cavitation. Following a transverse dural/arachnoid incision and C5-6 dorsal spinal hemisection, a 5-mm2 cadaveric dura mater allograft was placed over the lesion and fixed with fibrin glue (n=12). Control animals received an identical dural/arachnoid incision and cervical dorsal hemisection without dural repair (n=12). At 1, 5, and 10 weeks post-injury, plain film myelograms were obtained to characterize CSF circulation, and stereological methods were used to compare the extent of tissue sparing between the two groups. Immunohistochemical studies were performed to assess the degree of inflammation (ED-1), connective tissue scarring (laminin and type IV collagen), and reactive astrogliosis (GFAP). Our results indicate that dural allograft can improve CSF flow adjacent to the site of injury, which may be due to reduced meningeal fibrosis/scarring at the lesion site. Stereological analysis demonstrated that duraplasty resulted in a significant reduction in lesion volume at each time-point (p<0.01) associated with a nearly complete attenuation of post-traumatic cystic cavitation (p<0.001). Immunofluorescence studies demonstrated that duraplasty reduced the infiltration of ED-1-positive macrophages/microglia into and surrounding the lesion site, which may be responsible for the marked reduction in secondary injury following duraplasty. We conclude that duraplasty following acute spinal cord laceration may (1) improve CSF flow by limiting meningeal fibrosis; (2) reduce connective tissue scar formation; and (3) attenuate macrophage accumulation and progressive secondary injury.

Acute Disease↗
PubMed2005

Safety protocols for interventional MRI.

RATIONALE AND OBJECTIVES: To review magnetic resonance safety protocols and supplement them for interventional applications. MATERIALS AND METHODS: The American College of Radiology White Papers on MR Safety are summarized. Elements relevant to interventional MR procedures are emphasized. Additional policies and procedures specifically for interventional MR applications covering safety, training, and MR compatibility are proposed. RESULTS: A comprehensive operational policy for an interventional MR department is proposed. The policies and procedures helped our department perform over 400 surgeries and maintain a perfect safety record for 5 years. CONCLUSION: Interventional MR departments can operate safely but require policies and procedures beyond those required for diagnostic MR departments.

Electromagnetic Fields↗
PubMed2005

Functional and electrophysiological changes after graded traumatic spinal cord injury in adult rat.

A graded contusion spinal cord injury (SCI) was created in the adult rat spinal cord using the Infinite Horizons (IH) impactor to study the correlation between injury severity and anatomical, behavioral, and electrophysiological outcomes. Adult Fisher rats were equally divided into five groups and received contusion injuries at the ninth thoracic level (T9) with 100, 125, 150, 175, or 200 kdyn impact forces, respectively. Transcranial magnetic motor-evoked potentials (tcMMEPs) and BBB open-field locomotor analyses were performed weekly for 4 weeks postinjury. Our results demonstrated that hindlimb locomotor function decreased in accordance with an increase in injury severity. The locomotor deficits were proportional to the amount of damage to the ventral and lateral white matter (WM). Locomotor function was strongly correlated to the amount of spared WM, which contains the reticulospinal and propriospinal tracts. Normal tcMMEP latencies were recorded in control, all of 100-kdyn-injured and half of 125-kdyn-injured animals. Delayed latency responses were recorded in some of 125-kdyn-injured and all of 150-kdyn-injured animals. No tcMMEP responses were recorded in 175- and 200-kdyn-injured animals. Comparison of tcMMEP responses with areas of WM loss or demyelination identified the medial ventrolateral funiculus (VLF) as the location of the tcMMEP pathway. Immunohistochemical and electromicroscopic (EM) analyses showed the presence of demyelinated axons in WM tracts surrounding the lesion cavities at 28 days postinjury. These data support the notion that widespread WM damage in the ventral and lateral funiculi may be a major cause for locomotor deficits and lack of tcMMEP responses after SCI.

Animals↗
PubMed2005

Adult rat forelimb dysfunction after dorsal cervical spinal cord injury.

Repairing upper extremity function would significantly enhance the quality of life for persons with cervical spinal cord injury (SCI). Repair strategy development requires investigations of the deficits and the spontaneous recovery that occurs when cervical spinal cord axonal pathways are damaged. The present study revealed that both anatomically and electrophysiologically complete myelotomies of the C4 spinal cord dorsal columns significantly increased the adult rat's averaged times to first attend to adhesive stickers placed on the palms of their forepaws at 1 week. Complete bilateral myelotomies of the dorsal funiculi and dorsal hemisection, but not bilateral dorsolateral funiculi injuries, also similarly increased these times at 1 week. These data extend a previous finding by showing that a forepaw tactile sensory deficit that occurred in the adult rat after bilateral C4 spinal cord dorsal funiculi injury is due to damage of the dorsal columns. Averaged times to first attend to the stickers also decreased to those of sham-operated rats at 3 and 4 weeks post-dorsal hemisection with weekly testing. In contrast, a separate group of rats with dorsal hemisections had significantly increased times when tested only at 4 weeks. These data indicate that frequent assessment of this particular behavior in rats with dorsal hemisections extinguishes it and/or engenders a learned response in the absence of sensory axons in the dorsal columns and dorsolateral funiculi. This finding contrasted with weekly testing of grid walking where increased forelimb footfall numbers persisted for 4 weeks post-dorsal hemisection.

Afferent Pathways↗
PubMed2005

The therapeutic window for spinal cord decompression in a rat spinal cord injury model.

OBJECT: There are no clinically based guidelines to direct the spine surgeon as to the proper timing to undertake decompression after spinal cord injury (SCI) in patients with concomitant stenosis-induced cord compression. The following three factors affect the prognosis: (1) severity of SCI; (2) degree of extrinsic spinal cord compression; and (3) duration of spinal cord compression. METHODS: To elucidate further the relationship between varying degrees of spinal stenosis and a mild contusion-induced SCI (6.25 g-cm), a rat SCI/stenosis model was developed in which 1.13- and 1.24-mm-thick spacers were placed at T-10 to create 38 and 43% spinal stenosis, respectively. Spinal cord damage was observed after the stenosis-SCI that was directly proportional to the duration of spinal cord compression. The therapeutic window prior to decompression was 6 and 12 hours in the 43 and 38% stenosis-SCI lesions, respectively, to maintain locomotor activity. A significant difference in total lesion volume was observed between the 2-hour and the delayed time(s) to decompression (38% stenosis-SCI, 12 and 24 hours, p < 0.05; 43% stenosis-SCI, 24 hours, p < 0.05) indicating a more favorable neurological outcome when earlier decompression is undertaken. This finding was further supported by the animal's ability to support weight when decompression was performed by 6 or 12 hours compared with 24 hours after SCI. CONCLUSIONS: Analysis of the findings in this study suggests that early decompression in the rat improves locomotor function. Prolongation of the time to decompression may result in irreversible damage that prevents locomotor recovery.

Animals↗
PubMed2004

PKC mediates inhibitory effects of myelin and chondroitin sulfate proteoglycans on axonal regeneration.

Successful axon regeneration in the mammalian central nervous system (CNS) is at least partially compromised due to the inhibitors associated with myelin and glial scar. However, the intracellular signaling mechanisms underlying these inhibitory activities are largely unknown. Here we provide biochemical and functional evidence that conventional isoforms of protein kinase C (PKC) are key components in the signaling pathways that mediate the inhibitory activities of myelin components and chondroitin sulfate proteoglycans (CSPGs), the major class of inhibitors in the glial scar. Both the myelin inhibitors and CSPGs induce PKC activation. Blocking PKC activity pharmacologically and genetically attenuates the ability of CNS myelin and CSPGs to activate Rho and inhibit neurite outgrowth. Intrathecal infusion of a PKC inhibitor, Gö6976, into the site of dorsal hemisection promotes regeneration of dorsal column axons across and beyond the lesion site in adult rats. Thus, perturbing PKC activity could represent a therapeutic approach to stimulating axon regeneration after brain and spinal cord injuries.

Animals↗
PubMed2004

A neuroprotective role of glial cell line-derived neurotrophic factor following moderate spinal cord contusion injury.

The present study investigated neuroprotective effects of glial cell line-derived neurotrophic factor (GDNF), a distant member of the transforming growth factor-beta (TGF-beta) superfamily, following moderate contusive spinal cord injury (SCI) in adult rats. A T11 spinal cord contusion injury was made using an Infinite Horizon impactor (IH; impact force=150 kDyn) and recombinant human GDNF at two concentrations (rhGDNF; 1 or 5 microg/microl), or saline vehicle was delivered intrathecally for 28 days using an Alzet miniosmotic pump. We demonstrated that, at 7 weeks postinjury, GDNF infusion significantly reduced the total lesion volume by 34-42% (assessed stereologically) and increased the percentage of white matter sparing by 10-13% (measured at the injury epicenter), as compared to the vehicle infusion. Retrograde tracing revealed that GDNF infusion resulted in a significant increase in the number of FluoroGold (FG)-labeled neurons in propriospinal regions as well as in two supraspinal regions, that is, the medullary and pontine reticular formation, and the lateral vestibular nucleus. Immunofluorescent staining confirmed that the spared white matter contained neurofilament-positive axons. However, transcranial magnetic motor-evoked potential (tcMMEP) assessment revealed no significant difference in onset latency and amplitude between the GDNF- and vehicle-infused groups. These results suggest that GDNF has a strong neuroprotective effect on white matter sparing and the sparing of a subset of proprio- and supraspinal axons following injury. However, a return of tcMMEPs requires the sparing and/or myelination of axons in a defined region of the white matter which was either not spared or remyelinated at this level of injury severity.

Animals↗
PubMed2004

Dynamic weight-bearing cervical magnetic resonance imaging: technical review and preliminary results.

BACKGROUND: Conventional magnetic resonance imaging (MRI) of complex cervical spine disorders may underestimate the magnitude of structural disease because imaging is performed in a nondynamic non-weight-bearing manner. Myelography provides additional information but requires an invasive procedure. METHODS: This was a prospective review of the first 20 upright weight-bearing cervical MRI procedures with patients in the flexed, neutral, and extended positions conducted in an open-configuration MRI unit. RESULTS: This technique clearly illustrated the changes in spinal cord compression, angulation, and spinal column alignment that occur during physiologic movements with corresponding changes in midsagittal spinal canal diameter (P < 0.05). Image quality was excellent or good in 90% of the cases. CONCLUSIONS: Dynamic weight-bearing MRI provides an innovative method for imaging complex cervical spine disorders. This technique is noninvasive and has adequate image quality that may make it a good alternative to cervical myelography.

Adolescent↗
PubMed2004

Vaccinia virus complement control protein reduces inflammation and improves spinal cord integrity following spinal cord injury.

Traumatic spinal cord injury (SCI) claims approximately 10,000 new victims each year in the United States alone. The injury usually strikes those under the age of 30 years, often leading to a lifetime of pain, suffering, and disability. Therapeutic agents targeting spinal cord injury are sorely lacking, and therefore our laboratory endeavored to evaluate the potential therapeutic benefits of immediate post-injury administration of the vaccinia virus complement control protein (VCP). VCP is a multifunctional anti-inflammatory protein that can inhibit both pathways of complement activation and bind heparin. Utilizing a common animal model of contusion SCI, motor function recovery tests, and immunochemical stains, we evaluated the effects of VCP injected into spinal cord tissue following injury. Results demonstrate that VCP administration inhibits macrophage infiltration, reduces spinal cord destruction, and improves hind-limb function, establishing VCP as a strong candidate for further investigation in the treatment of SCI.

Animals↗
PubMed2004

Dural closure, cord approximation, and clot removal: enhancement of tissue sparing in a novel laceration spinal cord injury model.

OBJECT: Laceration-induced spinal cord injury (SCI) results in the invasion of a connective tissue scar, progressive damage to the spinal cord due to complex secondary injury mechanisms, and axonal dieback of descending motor pathways. The authors propose that preparation of the spinal cord for repair strategies should include hematoma removal and dural closure, resulting in apposition of the severed ends of the spinal cord. Such procedures may reduce the size of the postinjury spinal cord cyst as well as limit scar formation. METHODS: Using a novel device, the Vibraknife, the authors created a dorsal hemisection of the spinal cord at C-6 in the adult rat. In Group 1 (eight rats), the dura mater was repaired with apposition of the two stumps of the spinal cord to reduce the lesion gap. In Group 2 (10 rats), the dura was not closed and the two cord stumps were not approximated. All rats were killed at 4 weeks postinjury, and the spinal cords from each group were removed and examined using histological, stereological, and immunohistochemical methods. In Group 1 rats a significant reduction of the total lesion volume and connective tissue scar was observed compared with those in Group 2 (Student t-test, p < 0.05). Approximation of the stumps did not promote the regeneration of corticospinal tract fibers or sensory axons through the lesion site. CONCLUSIONS: Apposition of the severed ends of the spinal cord by dural closure reduces the lesion gap, cystic cavitation, and connective tissue scar formation. These outcomes may collectively reduce secondary tissue damage at the injury site and shorten the length of the lesion gap, which will facilitate transplantation-mediated axonal regeneration after laceration-induced SCI.

Animals↗
PubMed2003

Outcome following moderate traumatic brain injury.

BACKGROUND: Little is known about the outcome following moderate traumatic brain injury (TBI) (GCS 9-12). Most patients regain consciousness; however, the full magnitude of long-term cognitive and functional deficits is unknown. METHODS: We conducted a prospective observational study evaluating the outcome of patients suffering moderate TBI between October 1995 and March 1998. Long-term outcome was assessed by telephone interviews. RESULTS: A total of 79 consecutive patients were included. Average length of ICU and total hospital stay was 9.1 and 15.8 days respectively. The median GCS at 24 hours was 10 with 67% improving to GCS 15 by time of discharge. The presence of multisystem trauma did not affect outcome; however, age >/=45, initiation of enteral feeding after postinjury day 4 and the presence of pneumonia were all associated with longer lengths of stay and increased complication rates. Fifty-six (71%) patients were contacted for follow-up at an average of 27.5 months. GOS scores were 5 in 44%, 4 in 41%, 3 in 9%, 1 in 6%. Seventy-four percent of patients employed premorbidly returned to full-time work. Questions regarding cognitive and functional status revealed significant problems in the majority of patients. CONCLUSIONS: Pneumonia, age >/=45 years and a delay in initiation of enteral feeding all increased the duration of acute care hospital stay following moderate TBI. In addition, cognitive, emotional, and functional problems following such injuries are extensive and long lasting. Physicians must be knowledgeable of these long-term sequela so they can provide the appropriate support and treatment to these patients.

Activities of Daily Living↗
PubMed2003

New neurophysiology and central nervous system dysfunction.

PURPOSE OF REVIEW: The goal of this article is to summarize very recent technologic advances in neurophysiologic monitoring and to illustrate their potential benefit to critical care medicine. RECENT FINDINGS: Simplified, computer-processed electroencephalography devices now permit cost-effective, long-term critical care monitoring. They may be used alone to objectively assess sedation or coma level. In addition, these monitors serve as screening tools for more detailed electrophysiologic characterization of cortical dysfunction resulting from seizures, ischemia, or hypoxia. Somatosensory potentials broaden these capabilities to the entire neuraxis, whereas long-latency auditory evoked potentials facilitate measurement of changes in vigilance and cognition. Motor evoked potentials offer a sensitive and reliable method to determine the function of descending motor pathways in uncooperative or unresponsive patients. They may also yield a new measure of cortical excitability. New developments with transcranial Doppler ultrasonography promise noninvasive measures of cerebral perfusion pressure and particulate embolization. Near-infrared spectroscopy appears to enable noninvasive measurement of regional tissue oxygenation in both the brain and spinal cord. SUMMARY: When used together, these continuous measures of synaptic function, cerebral perfusion, and oxygenation give the clinician a vast amount of otherwise unobtainable information regarding the functional status of the central nervous system.

Central Nervous System Diseases↗
PubMed2002

Interventional MRI-guided frameless stereotaxy in pediatric patients.

INTRODUCTION: We prospectively reviewed our experience with intraoperative MRI (iMRI)-guided stereotactic procedures in pediatric patients. METHODS: All procedures were performed within the magnet bore of the General Electric Signa SP MRI system, which allows for either continuous real-time or periodic imaging. The internal optical tracking system was used to plan and monitor target localization and instrument trajectory. RESULTS: Fifteen patients underwent 16 frameless stereotactic procedures, consisting of 4 tumor biopsies and 12 cyst aspirations and stereotactic catheter placements (average age 6 years, range 6 weeks to 18 years). There were no hemorrhagic, neurologic or infectious complications. CONCLUSION: iMRI is an important component in expanding the horizon of minimally invasive neurosurgery for pediatric patients. Thus far, we have found this technology to be safe, reliable and extremely useful for frameless stereotactic procedures.

Adolescent↗
PubMed2002

R. Glen spurling: surgeon, author, and neurosurgical visionary.

Doctor Roy Glenwood Spurling (1894-1968) stands as a prominent figure in the field of neurosurgery. His innovative contributions have left an indelible mark, particularly in the treatment of lumbar and cervical intervertebral disc diseases and peripheral nerve injuries. He was instrumental in founding the Harvey Cushing Society (later renamed the American Association of Neurological Surgeons) and the American Board of Neurological Surgery. Spurling was a major participant in the military during World War II; he was stationed at Walter Reed Hospital and in the European Theater, and later became well known for his care of General George S. Patton. Glen Spurling is a role model to a younger generation of neurosurgeons for his tireless effort toward the advancement of neurosurgery.

History, 20th Century↗