Developmental expression and function analysis of protein tyrosine phosphatase receptor type D in oligodendrocyte myelination

Receptor protein tyrosine phosphatases (RPTPs) are extensively expressed in the central nervous system (CNS), and have distinct spatial and temporal patterns in different cell types during development. Previous studies have demonstrated possible roles for RPTPs in axon outgrowth, guidance, and synaptogenesis. In the present study, our results revealed that protein tyrosine phosphatase, receptor type D (PTPRD) was initially expressed in mature neurons in embryonic CNS, and later in oligodendroglial cells at postnatal stages when oligodendrocytes undergo active axonal myelination process. In PTPRD mutants, oligodendrocyte differentiation was normal and a transient myelination delay occurred at early postnatal stages, indicating the contribution of PTPRD to the initiation of axonal myelination. Our results also showed that the remyelination process was not affected in the absence of PTPRD function after a cuprizone-induced demyelination in adult animals.

Cells enriched in markers of neural tissue-committed stem cells reside in the bone marrow and are mobilized into the peripheral blood following stroke

The concept that bone marrow (BM)-derived cells participate in neural regeneration remains highly controversial and the identity of the specific cell type(s) involved remains unknown. We recently reported that the BM contains a highly mobile population of CXCR4+ cells that express mRNA for various markers of early tissue-committed stem cells (TCSCs), including neural TCSCs. Here, we report that these cells not only express neural lineage markers (beta-III-tubulin, Nestin, NeuN, and GFAP), but more importantly form neurospheres in vitro. These neural TCSCs are present in significant amounts in BM harvested from young mice but their abundance and responsiveness to gradients of motomorphogens, such as SDF-1, HGF, and LIF, decreases with age. FACS analysis, combined with analysis of neural markers at the mRNA and protein levels, revealed that these cells reside in the nonhematopoietic CXCR4+/Sca-1+/lin-/CD45 BM mononuclear cell fraction. Neural TCSCs are mobilized into the peripheral-blood following stroke and chemoattracted to the damaged neural tissue in an SDF-1-CXCR4-, HGF-c-Met-, and LIF-LIF-R-dependent manner. Based on these data, we hypothesize that the postnatal BM harbors a nonhematopoietic population of cells that express markers of neural TCSCs that may account for the beneficial effects of BM-derived cells in neural regeneration.

Vaccinia virus complement control protein modulates inflammation following spinal cord injury

The vaccinia virus complement control protein (VCP) possesses multiple modulatory functions. Functioning as a complement inhibitory protein, VCP reduces production of proinflammatory chemotactic factors produced during complement activation. Additionally, VCP binds heparin and heparan sulfate proteoglycans, resulting in added functions shown to block monocyte chemotaxis in vitro. Using an in vivo spinal cord contusive injury model in rats, the inflammation-modulating abilities of VCP were evaluated. The results of both myeloperoxidase assaying and H&E stained section counts of spinal tissue reveal that neutrophil infiltration to the area of the lesion was reduced in animals that received VCP as compared to saline-injected controls.

Intraoperative MRI for pediatric tumor management

The emergence of intraoperative MRI has opened new doors for the surgical treatment of pediatric disorders. This technology will hopefully not only improve the surgeon's ability to obtain complete tumor resections with minimal damage to surrounding structures, but also allows surgeons to perform various procedures via less invasive measures. We performed a total of 38 procedures in 36 children in our intraoperative MRI system (GE Signa SP, open configuration). All procedures were performed within the magnet bore, which allows for either continuous real-time or periodic imaging. Procedures included craniotomy for tumor resection, open biopsy, stereotactic biopsy or catheter placement into a tumor-related cyst. There were no infectious, hemorrhagic or neurological complications. Intraoperative MRI is an useful tool for the management of pediatric neurosurgical disorders. Intraoperative imaging not only helps surgeons navigate through eloquent areas of the brain, but also ensures the maximal possible tumor resection or confirms adequate catheter placement prior to skin closure. The impact of this technology on long term survival is yet to be determined.

Changes in cyst volume following intraoperative MRI-guided Ommaya reservoir placement for cystic craniopharyngioma

INTRODUCTION

Intracavitary treatment of solitary cystic craniopharyngiomas with (32)P is an emerging treatment option, especially for pediatric patients. We have treated two patients with solitary cystic craniopharyngiomas using intraoperative MRI (iMRI)-guided catheter placement.

METHODS

The optical tracking system of the General Electric Signa SP iMRI system was utilized for preoperative planning and intraoperative catheter tracking during insertion. Intraoperative volumetric imaging was then used to confirm final catheter position. Patients were brought back to the iMRI suite approximately 8 weeks later and diluted gadolinium was injected with further MRI to confirm the absence of communication between the cyst lumen and surrounding CSF spaces and for volumetric analysis.

RESULTS

Intraoperative imaging illustrated deformation and changes in the cyst wall during catheter placement and cyst aspiration and confirmed final catheter placement. Images acquired 8 weeks following catheter placement prior to the instillation of (32)P showed decreases in cyst volume of 40 and 85%.

CONCLUSION

iMRI-guided catheter placement for cystic craniopharyngiomas helps to assure successful catheter placement. Significant decreases in cyst volume occur in the interval between catheter placement and (32)P administration and must be accounted for to prevent overdosing of the radioisotope.

Development and implementation of a clinical pathway for severe traumatic brain injury

BACKGROUND

Clinical pathways (CPs) have been shown to be beneficial in optimizing patient care and resource use.

METHODS

A multidisciplinary CP for the treatment of severe traumatic brain injury (Glasgow Coma Scale score of 3-7) was developed. Data from these patients (group I) were collected prospectively and compared with a retrospective database (group II).

RESULTS

There were a total of 119 patients managed in conjunction with the CP and 43 patients in the control group. No statistical differences were found between the groups in age, Glasgow Coma Scale score at 24 hours, or Injury Severity Scores. There was a significant decrease in the length of hospital stay, intensive care unit stay, and length of ventilator support in the study group (group I: 22.5, 16.8, and 11.5 days, respectively; group II: 31.0, 21.2, and 14.4 days, respectively; p < 0.03).

CONCLUSION

The use of this CP helped to standardize and improve patient care with fewer complications and a potential cost savings of approximately $14,000 per patient.

Development and implementation of a clinical pathway for spinal cord injuries

The authors have developed a clinical pathway for the treatment of spinal cord injuries to help improve patient care. A clinical pathway for the treatment of patients with spinal cord injury was developed through a multidisciplinary approach. The control group (group 1) consisted of patients who were treated in the 2 years before the initiation of the pathway. Data from patients treated in conjunction with this pathway were collected prospectively (group 2). Thirty-six patients were treated in conjunction with the pathway compared with 22 in the control group. Group 2 had 6.8 fewer intensive care unit days, 11.5 fewer hospital days, 6 fewer ventilator days (p < 0.05), and a lower rate of complications. The use of a clinical care pathway for spinal cord injuries has resulted in improved patient care and fewer complications.

Incidence rates and populations at risk for spinal cord injury: A regional study

STUDY DESIGN

A 6 year retrospective study was conducted.

OBJECTIVES

The populations at risk for spinal cord injury (SCI) in the northwestern Kentucky (KY) and southern Indiana (IN) regions were identified following examination of the causes and factors associated with SCI.

SETTING

The database included patients primarily from the surrounding KY and IN counties admitted to the University of Louisville (U of L) Hospital.

METHOD

Specification of SCI patient demographics, injury causes and related factors was achieved utilizing the hospital's trauma institute database and an extensive review of patient medical records.

RESULTS

An adjusted average incidence rate of 27.1 cases per million per year was obtained for this region. A high rate of SCI was found for the youngest age group, 14-24 year olds, and for African Americans. A high frequency of injuries was also observed for adults between the ages of 25-39 years. Motor vehicle accidents (MVA) were the leading cause of SCI. Contributing factors included alcohol and widespread non-use of vehicle safety precautions.

CONCLUSIONS

In addition to the high proportion of youth at risk for SCI, a higher proportion of older adults with SCI was observed for this region compared to other studies. Because the primary source of transportation in this area is the use of private vehicles, rather than public transportation, greater effort is warranted in emphasizing the potential risks of combining driving with alcohol consumption and non-use of seatbelts.

Treatment of neoplastic diseases of the sacrum

Sacral neoplasms constitute a wide range of pathological entities including primary and metastatic as well as benign and malignant conditions. Often these lesions are large at the time of initial diagnosis and surgical cure may be difficult. Nonetheless, surgery may be indicated for a wide range of reasons including tissue diagnosis, palliation of pain, preservation of neurological function, or attempts for curative resection. There are numerous surgical approaches to lesions of this area which require a complete understanding of the neural, pelvic, and bony anatomy. For this reason we utilize a multidisciplinary team approach when treating these lesions. This allows for the combination of expertise from areas such as general surgery, orthopedic surgery, and neurosurgery that optimizes the treatment of these patients. In this article we review the basic techniques of diagnosis and treatment of these lesions. This overview includes the relative anatomy, symptoms, diagnosis, imaging, operative indications, surgical approaches, and potential complications.

A topical mixture for preventing, abolishing, and treating autophagia and self-mutilation in laboratory rats

The dysesthesia and paresthesia that occurs in laboratory rats after spinal cord injury and peripheral nerve injury results in autophagia and self-mutilation. This self-destructive behavior interferes with functional assessments in designed studies and jeopardizes the health of the injured rat. We developed a topical mixture that prevents, abolishes, and treats autophagia and self-mutilation. When the mixture is applied to the limb, its bitterness effectively prevents the rat from licking and biting the limb. In addition, the mixture has antiseptic properties.

Adult human olfactory stem cells

The location of stem cells within the adult CNS makes them impractical for surgical removal and autologous transplantation. Their limited availability and histocompatibility issues further restrict their use. In contrast, olfactory neuroepithelium (ONe) located in the nasal passageways has a continuous regenerative capability and can be biopsied readily. To investigate the potential of human ONe to provide viable populations of pluripotent cells, ONe was harvested from cadavers 6-18 h postmortem, dissociated, plated and fed every 3-4 days. Heterogeneous populations of neurons, glia, and epithelia were identified with lineage-specific markers. After several weeks, 5-10% of the cultures produced a population of rapidly dividing cells, which in turn, produced neurospheres containing at least two subpopulations based on neuronal and glial specific antigens. Most contained one or more neuronal markers; a few were positive for A2B5 and/or GFAP. To determine if growth modulators would affect the neurosphere forming cells, they were exposed to dibutyryl-cAMP. The nucleotide reduced cell division and increased process formation. Although the cells had been passaged more than 70 times, their viability remained constant as shown by the MTT viability index. Donor age or sex were not limiting factors, because neurospheres have been established from cadavers of both sexes from 50 to 95 years old at time of death. The ex vivo expansion of these cells will provide a patient-specific population of cells for immunological, genetic and pharmacological evaluation. Our long-term goal is to determine the utility of these cells to facilitate CNS repair.

Lasting paraplegia caused by loss of lumbar spinal cord interneurons in rats: no direct correlation with motor neuron loss

OBJECT

The aims of this study were to investigate further the role played by lumbar spinal cord interneurons in the generation of locomotor activity and to develop a model of spinal cord injury suitable for testing neuron replacement strategies.

METHODS

Adult rats received intraspinal injections of kainic acid (KA). Locomotion was assessed weekly for 4 weeks by using the Basso, Beattie, and Bresnahan (BBB) 21-point locomotor scale, and transcranial magnetic motor evoked potentials (MMEPs) were recorded in gastrocnemius and quadriceps muscles at 1 and 4 weeks. No changes in transcranial MMEP latency were noted following KA injection, indicating that the descending motor pathways responsible for these responses, including the alpha motor neurons, were not compromised. Rats in which KA injections included much of the L-2 segment (10 animals) showed severe locomotor deficits, with a mean BBB score of 4.5 +/- 3.6 (+/- standard deviation). Rats that received lesions rostral to the L-2 segment (four animals) were able to locomote and had a mean BBB score of 14.6 +/- 2.6. Three rats that received only one injection bilaterally centered at L-2 (three animals) had a mean BBB score of 3.2 +/- 2. Histological examination revealed variable loss of motor neurons limited to the injection site. There was no correlation between motor neuron loss and BBB score.

CONCLUSIONS

Interneuron loss centered on the L-2 segment induces lasting paraplegia independent of motor neuron loss and white matter damage, supporting earlier suggestions that circuitry critical to the generator of locomotor activity (the central pattern generator) resides in this area. This injury model may prove ideal for studies of neuron replacement strategies.

The role of directly applied hypothermia in spinal cord injury

STUDY DESIGN

The effect of intense local hypothermia was evaluated in a precision model of spinal canal narrowing and spinal cord injury in rats. The spinal cord injury was cooled with a custom cooling well used over the epidural surface. Basso, Beattie, and Bresnahan (BBB) motor scores and transcranial magnetic motor-evoked potential (tcMMEP) responses were used after injury to accurately evaluate neurologic recovery.

OBJECTIVE

This study was undertaken to determine whether the prognosis for neurologic recovery in a standardized rat spinal cord injury model is altered by the direct application of precisely controlled hypothermia to the area of injury.

SUMMARY OF BACKGROUND DATA

The role of hypothermia in the treatment of spinal cord injuries with neurologic deficits remains undefined. Hypothermia may decrease an area of spinal cord injury and limit secondary damage, therefore improving neurologic recovery. However, it has been difficult to consistently apply localized cooling to an area of spinal cord injury, and the use of systemic hypothermia is fraught with complications. This fact, along with the unavailability of a precise spinal cord injury model, has resulted in inconsistent results, both clinically and in the laboratory. In a rat model of spinal cord injury, 37 C and 19 C temperatures were used to study the role of hypothermia on neurologic recovery.

METHODS

Male Spraque-Dawley rats (n = 52; weight, 277.7 g) were anesthetized with pentobarbital and subjected to laminectomy at T10. The rats were divided into three groups: 1) placement of a 50% spacer in the epidural space (16 rats), 2) severe (25 g/cm) spinal cord injury (16 rats), 3) 50% spacer in combination with spinal cord injury (16 rats). Eight rats in each group were tested at two temperatures: normothermic (37 C) and hypothermic (19 C). With the use of a specially designed hypothermic pool placed directly over the spinal cord for 2 hours, epidural heating to 37 C, and epidural cooling to 19 C was accomplished. Simultaneous measurements of spinal cord and body temperatures were performed. The rats underwent behavior testing using the BBB motor scores and serial tcMMEPs for 5 weeks. Statistical methods consisted of Student's t tests, one-way analysis of variance, Tukey post hoc t tests and chi2 tests.

RESULTS

There was a significant improvement in motor scores in rats subjected to hypothermia compared with those that were normothermic after insertion of a 50% spacer. This improvement was observed during the 5-week duration of follow-up. In the severe spinal cord injury group and the spinal cord injury-spacer groups, no significant improvement in motor scores were obtained when the spinal cord was exposed to hypothermia.

CONCLUSION

The results demonstrate that there is a statistically significant (P < 0.05) improvement in neurologic function in rats subjected to hypothermia (19 C) after insertion of a spacer that induced an ischemic spinal cord injury. This indicates that directly applied hypothermia may be beneficial in preventing injury secondary to ischemic cellular damage. The data demonstrated minimal therapeutic benefit of hypothermia (19 C) after a severe spinal cord injury.

A laryngoscope designed for intubation of the rat

We successfully intubated 257 rats with a laryngoscope that we designed for this purpose. Orotracheal intubation with this laryngoscope can be performed quickly and without harm to the animal. This instrument provides direct visualization of the vocal cords, allowing rapid, safe intubation of the rat. Maintenance of an adequate airway with endotracheal intubation is superior to tracheostomy for repeated experiments, and therefore this laryngoscope makes such studies easier and safer to perform.

Magnetic motor evoked potential monitoring in the rat

OBJECT

The authors conducted a study to provide an objective electrophysiological assessment of descending motor pathways in rats, which may become a means for predicting outcome in spinal cord injury research.

METHODS

Transcranial magnetic motor evoked potentials (TMMEPs) were recorded under various conditions in awake, nonanesthetized, restrained rats. Normative data were collected to determine the reproducibility of the model and to evaluate the effect of changing the stimulus intensity on the evoked signals. In addition, an experiment was performed to determine if the TMMEPs produced were the result of auditory startle response (ASR) potentials elicited by the sound generated by the movement of the copper coil inside its casing during magnetic stimulation. Transcranial magnetic motor evoked potentials were elicited after magnetic stimulation. At 100% stimulus intensity, the mean forelimb onset latency was 4.2 +/- 0.39 msec, and the amplitude was 9.16 +/- 3.44 mV. The hindlimb onset latency was 6.5 +/- 0.47 msec, and the amplitude was 11.47 +/- 5.25 mV. As the stimulus intensity was decreased, the TMMEP onset latency increased and the response amplitude decreased. The ASR potentials were shown to have longer latencies, smaller amplitudes, and were more variable than those of the TMMEPs.

CONCLUSIONS

These experiments demonstrate that TMMEPs can be recorded in awake, nonanesthetized rats. The evoked signals were easy to elicit and reproduce. This paper introduces noninvasive TMMEPs as a new technique for monitoring the physiological integrity of the rat spinal cord.

Surgical treatment of lumbar spinal stenosis in patients older than 75 years of age

OBJECT

The purpose of this study was to evaluate the safety and efficacy of the surgical treatment of lumbar spinal stenosis in patients older than 75 years of age.

METHODS

The authors reviewed the records of 65 patients with lumbar spinal stenosis who were at least 75 years of age at the time of surgery, which was performed between November 1990 and May 1996. The 65 patients (43 women, 22 men; average age 78 years) underwent a total of 71 operations (one patient underwent three, and four patients underwent two). Fifteen patients (21%) underwent isolated lumbar decompression, and 56 patients (79%) underwent decompression in conjunction with posterior spinal fusion. There was an average of 1.7 levels decompressed per isolated lumbar decompression and 2.6 levels per decompression and fusion procedure. Seven patients (10%) experienced one or more serious postoperative complication, which included wound infection, septicemia, small bowel obstruction, stroke, myocardial infarction, gastrointestinal bleeding, and pulmonary embolus. In addition there was one intraoperative complication (hypotension [1%]) that required modification of the planned surgical procedure. No deaths were documented in the perioperative period.

CONCLUSIONS

With appropriate preoperative selection and evaluation, careful intraoperative monitoring, and attentive perioperative care, the surgical treatment of elderly patients with lumbar spinal stenosis can effect significant improvement with acceptable levels of morbidity and mortality.

The influence of spinal canal narrowing and timing of decompression on neurologic recovery after spinal cord contusion in a rat model

STUDY DESIGN

The effect of spinal canal narrowing and the timing of decompression after a spinal cord injury were evaluated using a rat model.

OBJECTIVE

To evaluate whether progressive spinal canal narrowing after a spinal cord injury results in a less favorable neurologic recovery. Additionally, to evaluate the effect of the timing of decompression after spinal cord injury on neurologic recovery.

SUMMARY OF BACKGROUND DATA

Results in previous studies are contradictory about whether the amount of canal narrowing or the timing of decompression after a spinal cord injury affects the degree of neurologic recovery.

METHODS

Forty adult male Sprague-Dawley rats were equally divided into a control group, in which spacers of 20%, 35%, and 50% were placed into the spinal canal after laminectomy, and an injury group in which the spacers were placed after a standardized incomplete spinal cord injury. After spacer removal, neurologic recovery in both was monitored by Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale (Ohio State University, Columbus, OH) motor scores and transcranial magnetic motor evoked potentials for 6 weeks followed by histologic examination of the spinal cords. Subsequently, 42 rats were divided into five groups in which, after spacer placement, the time until decompression was lengthened 0, 2, 6, 24, and 72 hours. Again, serial BBB motor scores and transcranial magnetic motor evoked potentials were used to assess neurologic recovery for 6 weeks until the animals were killed for histologic evaluation.

RESULTS

Spacer placement alone in the control animals resulted in no neurologic injury until canal narrowing reached 50%. All of the control groups (spacer only) exhibited significantly better (P < 0.05) motor scores compared with the injury groups (injury followed by spacer insertion). Within the injury groups the motor scores were progressively lower as spacer sizes increased from the no-spacer group to the 35% group. The results in the 35% and 50% groups were not statistically different. The results of the time until decompression demonstrated that the motor scores were consistently better the shorter the duration of spacer placement (P < 0.05) for each of the time groups (0, 2, 6, 24, and 72 hours) over the 6-week recovery period. Histologic analysis showed more severe spinal cord damage as both spinal canal narrowing and the time until decompression increased.

CONCLUSION

The results in this study present strong evidence that the prognosis for neurologic recovery is adversely affected by both a higher percentage of canal narrowing and a longer duration of canal narrowing after a spinal cord injury. The tolerance for spinal canal narrowing with a contused cord appears diminished, indicating that an injured spinal cord may benefit from early decompression. Additionally, it appears that the longer the spinal cord compression exists after an incomplete spinal cord injury, the worse the prognosis for neurologic recovery.

Comparing deficits following excitotoxic and contusion injuries in the thoracic and lumbar spinal cord of the adult rat

The majority of human spinal cord injuries involve gray matter loss from the cervical or lumbar enlargements. However, the deficits that arise from gray matter damage are largely masked by the severe deficits due to associated white matter damage. We have developed a model to examine gray matter-specific deficits and therapeutic strategies that uses intraspinal injections of the excitotoxin kainic acid into the T9 and L2 regions of the spinal cord. The resulting deficits have been compared to those from standard contusion injuries at the same levels. Injuries were assessed histologically and functional deficits were determined using the Basso, Beattie, and Bresnahan (BBB) 21-point open field locomotor scale and transcranial magnetic motor evoked potentials (tcMMEPs). Kainic acid injections into T9 resulted in substantial gray matter damage; however, BBB scores and tcMMEP response latencies were not different from those of controls. In contrast, kainic acid injections into L2 resulted in paraplegia with BBB scores similar to those following contusion injuries at either T9 or L2, without affecting tcMMEP response latencies. These observations demonstrate that gray matter loss can result in significant functional deficits, including paraplegia, in the absence of a disruption of major descending pathways.

Primary culture of adult mouse olfactory receptor neurons

Olfactory receptor neurons (ORNs) are unique because they can be replaced by stem cells throughout life. Previous studies have demonstrated that adult mouse olfactory epithelium (OE) injured by exposure to ZnSO4 through nasal irrigation can stimulate stem cell mitotic activity in situ, which continues when placed in culture. We report on an improved ZnSO4 delivery method, mist inhalation, which produces more consistent and greater yields of OE cells. Cultures established following this method contained bipolar, nest, fusiform, and giant cells. The bipolar cells usually underwent asymmetric process development. Some bipolar cells reacted positively to neuron-specific antibodies and were immunonegative for keratin and glia-specific proteins, suggesting that they were ORNs. Those that were negative for the neuron-specific proteins may represent either neuron progenitors or olfactory ensheathing cells. The fusiform cells were relatively small and undifferentiated, exposure to brain-derived neurotrophic factor resulted in their decrease and an increase in bipolar cells. Therefore, they might be the stem cells. The nest cells had morphological characteristics of epithelia and bound keratin antibodies. The giant cells had the morphology of epithelial cells but were negative for keratin; they may represent a unique cell population induced by the ZnSO4. These results indicate that the major cell types of intact OE are present in our cultures, and each retains characteristics found in situ. The mist inhalation method provides an in vitro population of adult mitotically active neurons for study.

The effects of propofol on rat transcranial magnetic motor evoked potentials

INTRAOPERATIVE MONITORING OF motor evoked potentials (MEPs) may become a valuable test of spinal cord function during surgery. Unfortunately, MEP responses are affected by most common anesthetics. We studied the effect of intravenous propofol on transcranial magnetic MEPs (tcMMEPs) in the rat. Baseline tcMMEPs were recorded before administration of the drug. Each rat then received three induction doses of propofol, 10, 5, and 5 mg/kg (totaling 10, 15, and 20 mg/kg) and three successive 20-minute infusion doses at rates of 10, 20, and 40 mg/kg/h, respectively. An MEP intensity series was performed after each induction dose, during each infusion, and during a 20-minute recovery period. tcMMEPs recorded during the induction period demonstrated a significant, dose-dependent increase in onset latency and a marked decrease in amplitude. Infusion tcMMEPs displayed increased onset latencies but demonstrated a significant change in amplitudes only after the largest infusion dose. The MEPs approached baseline levels after discontinuation of the propofol. This study demonstrates that tcMMEPs can be successfully recorded from the rat during propofol anesthesia.

Transcranial magnetic motor-evoked potentials in scoliosis surgery

Spinal cord monitoring using SSEPs is an accepted adjunct in the surgical correction of spinal deformities, but does not directly assess motor function. Motor-evoked potentials have been introduced in an effort to meet this important need. In this series of 18 patients, the feasibility of intraoperative monitoring using transcranial magnetic motor-evoked potentials is documented. The potential value of this neurophysiologic monitoring technique, as well as the pitfalls in interpretation, are reviewed.

An evaluation of motor-evoked potentials for detection of neurologic injury with correction of an experimental scoliosis

STUDY DESIGN

Controlled correction of scoliosis in a rat model was used to assess the accuracy of intraoperative motor-evoked potential monitoring.

OBJECTIVES

The purpose of this study was to develop a model in which motor-evoked potential changes could be compared with neurologic function after surgery, such that a threshold for responding to motor-evoked potential changes may be established.

SUMMARY OF BACKGROUND DATA

Intraoperative motor-evoked potential monitoring has become technically feasible. Clinical application now depends on the development of useful interpretation parameters and correlation with neurologic sequelae.

METHODS

Experimental scoliosis was produced in 30 rat pups. After growth, the rats underwent correction of their scoliosis by distraction. Changes in tcMMEP onset latency and amplitude were measured. Distraction was applied either until a 10% delay in tcMMEP onset latency (Group 1), until tcMMEP responses were ablated (Group 2), or for 10 minutes after the loss of transcranial magnetic stimulation response (Group 3).

RESULTS

In Group 1 (n = 10), all animals had tcMMEP with normal onset latency and normal neurologic examinations 24 hours after surgery. In Group 2 (n = 10), tcMMEP were normal in four rats, markedly delayed in three rats, and absent in three rats 24 hours after surgery. neurologic examination was normal in the four rats with normal tcMMEP. Moderate deficit was noted in two of the three rats with prolonged onset latency 24 hours after surgery; the third was intact. Moderate neurologic injury was noted in two of three rats with absent tcMMEP 24 hours after surgery; the third rat was paralyzed. In Group 3 (n = 10), vertebral dislocation was noted on lateral radiographs in eight of 10 animals. Twenty-four hours after surgery, tcMMEP remained absent, and paralysis was noted in the eight rats with dislocation. The two rats without dislocation had delayed tcMMEP but some return of neurologic function.

CONCLUSIONS

Comparison of the three groups shows a significant correlation between tcMMEP and endpoint neurologic outcome. None of the rats in Group 1 had a neurologic deficit after surgery as opposed to five of 10 rats in Group 2 and 10 of 10 rats in Group 3 with significant neurologic injury. These findings suggest that a 10% delay in onset latency would be an appropriate threshold for responsing to changes in tcMMEP.

A prospective analysis of intraoperative electromyographic monitoring of pedicle screw placement with computed tomographic scan confirmation

STUDY DESIGN

In a prospective study of 90 patients undergoing lumbar pedicle screw instrumentation, 512 screws were tested intraoperatively using electrical stimulation. The accuracy of this technique was verified after surgery by computed tomography.

OBJECTIVES

Computed tomographic scans taken after surgery were used to evaluate the efficacy of intraoperative screw stimulation and electromyographic monitoring of pedicle screw placement.

SUMMARY OF BACKGROUND DATA

Previous cadaveric and clinical studies showed the risk of pedicle screw malposition and the inadequate reliability of intraoperative radiographs to identify misplaced screws.

METHODS

Screws (total, 512) in 90 patients were stimulated intraoperatively, and stimulation threshold was recorded. Computed tomographic scans were taken after surgery to document pedicle screw position. Electromyographic thresholds and computed tomographic data were evaluated independently and compared to assess the accuracy of the electromyographic screw stimulation technique.

RESULTS

Intraoperative screw stimulation was extremely accurate in confirming the adequacy of screw position. A stimulation threshold greater than 15 mA provided a 98% confidence that the screw was within the pedicle. In eight of 90 patients (9%), electromyographic monitoring detected a screw malposition that was not identified on lateral radiograph.

CONCLUSIONS

Screw stimulation monitoring is a valuable and efficacious adjunct to lumbar pedicle screw instrumentation. A stimulation threshold greater than 15 mA reliably indicates adequate screw position. A stimulation threshold between 10 and 15 mA was generally associated with adequate screw position, although exploration of the pedicle is recommended. A stimulation threshold less than 10 mA was associated with a significant cortical perforation in most instances.

Radioneurosurgery using the LINAC scalpel: technique, indications, and literature review

Two available commercial units for radiosurgery are the modified linear accelerator (LINAC scalpel) and the gamma knife. Advantages of the LINAC scalpel over the gamma knife are its greater accuracy, the availability of a wide range of collimator sizes that allow for a more homogeneous field of radiation for large lesions, state-of-the-art computer software programs, and lower expense. Radiosurgery does not require an incision, is painless, and can be performed on an outpatient basis. It is ideally suited for the treatment of inaccessible, deep intracranial lesions that are radioresistant to conventional forms of radiotherapy, such as arteriovenous malformations, meningiomas, vestibular schwannomas, selected primary brain tumors, and cerebral metastases. Radiosurgery is an attractive treatment alternative to conventional neurosurgery for several intracranial lesions.

Anesthetic effects on motor evoked potentials in dogs

The effects of the various anesthetic agents on the production of transcranial magnetic motor evoked potentials (tcMMEP) were studied in a canine model. Pre-anesthetic baseline tcMMEPs demonstrated consistency in onset latency measurements and variability in measurement of peak-to-peak amplitudes. Changes in tcMMEPs were evaluated following the individual administrations of sodium pentothal, etomidate, halothane, fentanyl, and ketamine. For induction of anesthesia, etomidate was compatible with tcMMEP production, whereas sodium pentothal resulted in loss of hindlimb potentials for a period of 45 minutes. For maintenance of anesthesia, halothane was incompatible with the measurement of tcMMEPs. Fentanyl administration was consistent with the recording of reliable tcMMEPs, with consistent onset latencies but widely variable peak-to-peak amplitudes. Ketamine was compatible with stable and reproducible tcMMEP production. The results of this study suggest that anesthetic agents have a predictable and consistent effect on tcMMEP responses.

Correlation of motor-evoked potentials, somatosensory-evoked potentials, and the wake-up test in a case of kyphoscoliosis

The ability to monitor the descending motor pathways of the spinal cord during surgery is an important goal in neurophysiologic monitoring of spinal deformities. This report describes a case of a severe spinal deformity for which instrumentation and reduction carried a significant risk of neurologic complications. During the procedure, changes in neurologic status were monitored simultaneously using both SSEPs and tcMMEPs. The reliability of these two complimentary modalities was then verified by concurrent wake-up tests. This case provides documentation of the reliability of tcMMEP responses when an accurate assessment of motor function was necessary.

Imaging of radiation dose for stereotactic radiosurgery

The distributions of radiation dose for stereotactic radiosurgery, using a modified linear accelerator (Philips SL-25 and SRS-200), have been studied by using three different dosimeters: (1) ferrous-agarose-xylenol orange (FAX) gels, (2) TLD, and (3) thick-emulsion GafChromic dye film. These dosimeters were loaded into a small volume of defect in a phantom head. A regular linac stereotactic radiosurgery treatment was then given to the phantom head for each type of dosimeter. The measured radiation dose and its distributions were found to be in good agreement with those calculated by the treatment planning computer.

The role of stereotactic technology in the management of intracerebral hemorrhage

Stereotactic techniques have been utilized for more than 40 years in clinical neurosurgical practice. There has been considerable experience with stereotactic techniques in the drainage of intracerebral hemorrhages, although its effectiveness remains controversial. Stereotactic craniotomy, often incorporating advanced computer guidance, is increasingly applied to effect complete resection of small, deep brain lesions. Radiosurgery has become a viable alternative for the treatment of arteriovenous malformations that, in most cases, are untreatable by other means. Currently, stereotaxis is a valuable part of the therapeutic armamentarium available to cerebrovascular neurosurgeons.

Quantitative electroencephalographic monitoring during myocardial revascularization predicts postoperative disorientation and improves outcome

We evaluated computerized quantitative electroencephalography for the intraoperative detection of cerebral dysfunction. The quantitative electroencephalogram was recorded continuously during 96 myocardial revascularizations involving hypothermic cardiopulmonary bypass using Cerebrovascular Intraoperative MONitor (CIMON) software. CIMON relies on an adaptive statistical approach to detect subtle, but clinically relevant, changes in electroencephalographic activity indicative of cerebrocortical dysfunction. Relative (percent of total) low-frequency (1.5 to 3.5 Hz) power was chosen as the single quantitative electroencephalographic descriptor because it is an established hallmark of cortical dysfunction and is surprisingly insensitive to moderate changes in body temperature and level of opioid anesthesia. Reference values for this measure were established for each patient after anesthetic induction before sternotomy. The large sample variance often seen in low-frequency power was dramatically decreased by using log-transformed data and allowing each patient to serve as his own control. Quantitative electroencephalographic changes in standard deviation units or z-scores were determined from the individualized reference self-norm. Prolonged (greater than 5 minutes) and statistically significant (greater than 3 standard deviation) focal increases in relative low-frequency power were temperature-corrected to determine a standardized cerebrocortical dysfunction time at 37 degrees C. (CDT37). In phase I (n = 48), this objective quantitative electroencephalogram-based numeric descriptor was used to predict neuropsychologic outcome. These CDT37 greater than 5-minute episodes occurred 38 times in 19 patients. The quantitative electroencephalogram-based descriptor predicted the occurrence of such disorientation (n = 14 or 29%) with a 68% false positive rate but only an 8% false negative rate. Since these intraoperative quantitative electroencephalographic episodes were often (19/38) associated with low (less than 50 mm Hg) pump pressures, phase II (n = 48) sought to correct the quantitative electroencephalographic abnormality and prevent postoperative disorientation by appropriate increases in cerebral perfusion. Although the number of episodes of quantitative electroencephalographic abnormality was similar (n = 31) in phase II, these ischemic events disappeared after prompt elevation of perfusion pressure. The phase II disorientation rate fell significantly (p less than 0.002) to 4%. Thus statistically significant increases in low-frequency electroencephalographic relative power persisting for a temperature-corrected duration of 5 minutes or more are a reliable means of alerting the surgical/anesthesia team to the presence of cerebrocortical dysfunction and provide a rational and objective basis for corrective intervention. This form of electroencephalographic monitoring appears to offer an opportunity for the timely correction of perfusion abnormalities or the administration of cerebroprotectant compounds.

Is defibrillation testing safe?

Determination of defibrillation thresholds (DFTs) and implantable cardioverter defibrillator (ICD) testing requires repeated inductions of ventricular fibrillation (VF) and defibrillation attempts using known energy outputs. Little is known about the individual and cumulative effects of repetitive brief episodes of VF and hypoperfusion on cerebral function. The potential clinical utility of quantitative electroencephalographic (QEEG) monitoring during intraoperative ICD testing, by using processed 19-channel EEG (0.5-35 Hz bandwidth), was examined in ten anesthetized patients, five males and five females (mean age 62 +/- 10 years), who underwent ICD implantation and testing. Ischemic QEEG patterns were defined as those with a 3 standard deviation increase (P less than 0.01) in absolute delta (1.5-3.5 Hz) power persisting for greater than or equal to 2.5 minutes. The majority (80%) of the VF episodes (70) were accompanied by QEEG "slowing" (doubling of the pre-VF low frequency delta waves amplitude). All the patients (5/5) experiencing greater than 6 VF episodes showed a statistically significant increase in the low frequency amplitude. In contrast, this EEG abnormality was apparent in only one of five patients experiencing less than 6 VF episodes. These results suggest a cumulative QEEG depression associated with ICD testing. QEEG may provide an objective means for establishing an individualized upper safe limit of DFT testing and the total number of induced VF episodes.

Isolated injection injury to the posterior femoral cutaneous nerve

The sciatic nerve is by far the most common nerve accidentally injured during intramuscular injection. Despite its close proximity to the sciatic nerve, however, injury to the posterior femoral cutaneous nerve is apparently quite rare. In this report, clinical features of a patient with isolated injection injury to the posterior femoral cutaneous nerve are described.

Leadership in neurosurgery

These are challenging times for neurosurgery. Although no one can predict our future, great changes are in the wind--many of which we are powerless to prevent. We must all take on added social responsibility, above and beyond that of patient care. The leadership of your organization can only act with the support of active and concerned neurosurgeons who are willing to participate in many programs available to our profession. The individual must personally embrace the leadership standards of Sir William Osler and Harvey Cushing. One of the privileges of giving a presidential address is to pay public homage to those who have been supportive and instrumental in my long professional journey. During my residency, Dr. Dwight Parkinson was my mentor and teacher and set a wonderful standard for the ideal practice of neurosurgery. Decisions were black or white, never gray, with Dr. Parkinson, who left little doubt as to the correct way to handle clinical problems. He was, and continues to be, one of the most incisive, imaginative, innovative scientific minds in neurosurgery, and I owe him a great debt of gratitude. Two other men influenced my neurosurgical development. They are Dr. William Horsey, formerly neurosurgeon at the St. Michael's Hospital in Toronto, and Dr. Peardon Donaghy, with whom I spent a most enjoyable and productive year in Burlington at his microvascular neurosurgical laboratory. These two men demonstrated the humility, warmth, and kindness to patients that cannot be learned by formal study, but comes from observing the example of people who manifest those qualities in their own personality.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcranial magnetic motor evoked potentials (tcMMEP) for functional monitoring of motor pathways during scoliosis surgery

Transcranial magnetic motor evoked potentials (tcMMEP) were used to assess the functional integrity of the descending motor pathways. The tcMMEP, recorded bilaterally from anterior tibialis muscles, were evoked by an electric current induced in the motor cortex by a high-intensity transient magnetic field applied to the scalp surface. Potentials were recorded from ten of 12 volunteer subjects and preoperatively in 11 of 11 scoliotic patients. Group mean latency in the volunteers (32.0 +/- 2.1 msec) did not differ from that of the scoliotics (28.6 +/- 5.0 msec), but values in the latter group were more variable. During nitrous oxide-narcotic anesthesia, tcMMEP with reproducible latencies were obtained in 9 of 11 (82%) cases. A small, but statistically significant, increase in latency occurred during anesthesia. Compared with preoperative values (523 +/- 490 microV), individual tcMMEP amplitudes were significantly decreased intraoperatively (163 +/- 153 microV). Although the absolute amplitudes varied widely, the minimum recorded value was over 20 microV. Thus, intraoperative tcMMEP waveforms were readily discriminable from background electrical noise. These results demonstrate the technical feasibility of intraoperative tcMMEP monitoring. Combined somatosensory evoked potential and tcMMEP monitoring may provide a more complete picture of spinal cord function, intraoperatively.

Magnetically evoked facial nerve potential

Facial nerve stimulation by electrical current is painful and tends to discourage serial studies. Transcutaneous magnetic stimulation of the facial nerve is painless, easily reproducible, and elicits facial muscle responses identical to electrical stimulation.

MR imaging in acute cervical spine trauma

Fourteen patients with cervical spine injuries, 12 with resultant neurological deficits, were scanned with magnetic resonance (MR) imaging within 7 days following injury. Useful information concerning the status of the spinal canal and disks was obtained in most cases. In addition, MR was able to suggest the nature of the pathological changes within the spinal cord, as well as hemorrhage and edema in the extraspinal soft tissues. These observations indicate that following acute cervical spine trauma, MR is a valuable technique in assessing injury to the spinal cord, surrounding soft tissues, vertebra, and disks.

Safety and efficacy of chymopapain (Discase) in the treatment of sciatica due to a herniated nucleus pulposus. Results of a randomized, double-blind study

A prospective, multiinstitutional, double-blind trial comparing the effect of chymopapain (Discase) vs. placebo (cysteine-edetate-iothalamate: CEI) for lumbar intervertebral disc rupture with sciatica was carried out on 173 patients, the largest such study reported to date. Patients were matched with respect to age, sex, physical habitus, and level of injection. The procedure was carried out under local anaesthesia. The success rate was superior in the chymopapain group regardless of the method used to assess outcome or the time over the first 6 months at which the two groups were compared: 71% vs. 45% if code breaks were analyzed at 6 months, and 67% vs. 44% if code breaks were defined as lost to follow-up. A single case of anaphylaxis and one case of septic discitis were the only serious complications noted. This study supports the role of chymopapain in the treatment of lumbar disc rupture with sciatica.

The rat hippocampal slice preparation as an in vitro model of ischemia

In vivo models of cerebral ischemia do not fully control for the interacting effects of many variables (e.g., anesthesia, temperature, cerebrovascular changes) and often do not clearly define the region affected. Numerous in vivo studies have indicated that hyperglycemia augments ischemic brain damage; this effect is often attributed to lactic acidosis. To separate the effects on neuronal tissue of ischemia from those due to actions on the cerebrovascular system, we used an in vitro blood-free system as an ischemic model. In our study we evaluated the effects of various combinations of oxygen and glucose levels on evoked synaptic activity in the CA1 region of the rat hippocampal slice preparation. A 50% inhibitory dose for both oxygen and glucose on neuronal synaptic function was determined. It is our intention to use this model for preliminary screening of antihypoxic/anti-ischemic drugs.

Correlation of cerebral perfusion pressure and Glasgow Coma Scale to outcome

Cerebral Perfusion Pressures (CPP) and Glasgow Coma Scale (GCS) scores were monitored to guide the management of severely head-injured patients. These measures were correlated to outcome (Glasgow Outcome Scale-GOS) in 136 consecutive patients at least 1 year after injury. The GOS showed highly significant positive correlations to either CPP or GCS assessments (p less than 0.001). Two parameters that are correlated with subsequent death in most patients include 1) highest (h) GCS = 3 or 4 (Day 1: 31 of 32 patients died, and Day 2: 19 of 19 patients died), and 2) CPP less than or equal to 60 mm Hg more than 33% of the hourly measures during Day 2 (36% of all subsequent deaths; 11% overlap with the highest Glasgow Coma Scale). The Day 2 measures identifying two groups that have a greater than 75% incidence of "good outcome" or GOS = 4 or 5 include 1) hGCS greater than or equal to 6 (N = 45) and 2) the average (a) CPP greater than or equal to 90 mm Hg (N = 26). Of the 45 patients with a GOS = 4 or 5 who had both CPP and GCS recorded on the third day, 44 were identified by these "good outcome" parameters.

Chemonucleolysis with chymopapain: results in 150 patients

Chemonucleolysis with chymopapain has been advocated for the treatment of lumbar disc disease. When polled by a mail questionnaire, 150 consecutive patients who had undergone chemonucleolysis reported an overall success rate of only 40% and a failure rate of 60%. However, 57% of the patients were active or had only mild restriction of daily activities. Of those patients employed prior to injection, only 63% had returned to work. Those with workmen's compensation benefits fared considerably worse than those covered by third-party insurance (17% vs. 51% success). These results cast doubt on the long-term benefits of chymopapain in the treatment of lumbar disc disease.

Effect of the topical application of some newer antibiotics on the cerebral cortex

Five currently used antibiotics--moxalactam, cefotaxime, cefoperazone, metronidazole, and piperacillin--and bacitracin were compared for epileptogenetic effect against penicillin G as a standard when applied directly to cat cerebral cortex. Piperacillin was half as epileptogenic as penicillin. Moxalactam, cefotaxime, and cefoperazone showed epileptogenicity one-fourth to one-eighth that of penicillin on a milligram per cubic centimetre basis. Neither metronidazole nor bacitracin produced any focal seizure activity at the highest concentrations tested. Some of the newer cephalosporin antibiotics may have a significant risk of inducing seizure activity if high concentrations come in direct contact with neocortical tissue.

Multicenter retrospective review of results and complications of carotid endarterectomy in 1981

A multicenter retrospective audit of carotid endarterectomies performed during 1981 was completed with 46 institutions contributing 3,328 cases. Overall, there was a 2.5% risk of transient neurological dysfunction following surgery and a 6% risk of stroke or death. The intra-institutional combined major morbidity and mortality varied from 21% to 0. Those institutions with greater than 700 beds had a statistically lower incidence of stroke or death than did other institutions. The incidence of stroke or death postoperatively was significantly lower for patients who were operated on for amaurosis fugax or for unspecified reasons. Those patients who were operated on for a progressing stroke had a higher incidence of stroke but this group was at greatest risk for stroke without surgery. The incidence of postoperative stroke or death was related to the type of arterial repair; vein patch grafting was statistically better than both fabric patch grafting and primary closure. When all patients who were not monitored during surgery were compared to all patients who had electroencephalographic (EEG) monitoring, there was found to be a significant statistical difference in favor of the EEG group. Endarterectomy combined with coronary artery bypass or simultaneous bilateral endarterectomies had a statistically significant higher incidence of stroke or death than did unilateral carotid endarterectomy.

Cervical spine fractures with major associated trauma

A detailed review of 88 consecutive patients placed in skeletal tong traction for cervical fractures by the University of Louisville Neurosurgical Service during a 5-year period from July 1, 1979, through June 30, 1984, was carried out. Of this group, 60% of the patients had a major associated injury consisting of major facial and skull fractures, cerebral contusions or intracerebral blood clots, cardiac or pulmonary contusions, major thoracic injuries including rib fractures and hemo- or pneumothoraces, intra-abdominal injuries, and major extremity fractures. An additional 24% of the patients had minor associated injuries, including facial or scalp lacerations, general body lacerations, or abrasions and cerebral concussions. Only 16% of patients with cervical fractures had no evidence of any other associated injury. Acute cervical spine fractures require prompt assessment and resuscitation by personnel from multiple specialties, usually available only in major trauma centers where experienced personnel capable of handling diverse injuries are always present.