Clinical Characteristics and Surgical Outcomes of 2542 Patients with Spinal Schwannomas: A Systematic Review and Meta-Analysis

OBJECTIVE

This study was conducted to systematically analyze the data on the clinical features, surgical treatment, and outcomes of spinal schwannomas.

METHODS

We conducted a systematic review and meta-analysis under the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of bibliographic databases from January 1, 2001, to May 31, 2021, yielded 4489 studies. Twenty-six articles were included in our final qualitative systematic review and quantitative meta-analysis.

RESULTS

Analysis of 2542 adult patients' data from 26 included studies showed that 53.5% were male, and the mean age ranged from 35.8 to 57.1 years. The most common tumor location was the cervical spine (34.2%), followed by the thoracic spine (26.2%) and the lumbar spine (18.5%). Symptom severity was the most common indicator for surgical treatment, with the most common symptoms being segmental back pain, sensory/motor deficits, and urinary dysfunction. Among all patients analyzed, 93.8% were treated with gross total resection, which was associated with better prognosis and less chance of recurrence than subtotal resection. The posterior approach was the most common (87.4% of patients). The average operative time was 4.53 hours (95% confidence interval [CI], 3.18-6.48); the average intraoperative blood loss was 451.88 mL (95% CI, 169.60-1203.95). The pooled follow-up duration was 40.6 months (95% CI, 31.04-53.07). The schwannoma recurrence rate was 5.3%. Complications were particularly low and included cerebrospinal fluid leakage, wound infection, and the sensory-motor deficits. Most of the patients experienced complete recovery or significant improvement of preoperative neurological deficits and pain symptoms.

CONCLUSIONS

Our analysis suggests that segmental back pain, sensory/motor deficits, and urinary dysfunction are the most common symptoms of spinal schwannomas. Surgical resection is the treatment of choice with overall good reported outcomes and particularly low complication rates. gross total resection offers the best prognosis with the slightest chance of tumor recurrence and minimal risk of complications.

Continuous irrigation with thrombolytics for intraventricular hemorrhage: case-control study

Intraventricular hemorrhage (IVH) is a complication of a spontaneous intracerebral hemorrhage. Standard treatment is with external ventricular drain (EVD). Intraventricular thrombolysis may improve mortality but does not improve functional outcomes. We present our initial experience with a novel irrigating EVD (IRRAflow) that automates continuous irrigation with thrombolysis.Single-center case-control study including patients with IVH treated with EVD compared to IRRAflow. We compared standard demographics, treatment, and outcome parameters between groups. We developed a brain phantom injected with a human clot and assessed clot clearance using EVD/IRRAflow approaches with CT imaging.Twenty-one patients were treated with standard EVD and 9 patients with IRRAflow. Demographics were similar between groups. Thirty-three percent of patients with EVD also had at least one dose of t-PA and 89% of patients with IRRAflow received irrigation with t-PA (p = 0.01). Mean drain days were 8.8 for EVD versus 4.1 for IRRAflow (p = 0.02). Days-to-clearance of ventricular outflow was 5.8 for EVD versus 2.5 for IRRAflow (p = 0.02). Overall clearance was not different. Thirty-seven percent of EVD patients achieved good outcome (mRS ≥ 3) at 90 days versus 86% of IRRAflow patients (p = 0.03). Assessing only t-PA, reduction in mean days-to-clearance (p = 0.0004) and ICU days (p = 0.04) was observed. In the benchtop model, the clot treated with IRRAflow and t-PA showed a significant reduction of volume compared to control.Irrigation with IRRAflow and t-PA is feasible and safe for patients with IVH. Improving clot clearance with IRRAflow may result in improved clinical outcomes and should be incorporated into randomized trials.

HummingFlow: novel single twist-drill access for ventricular drainage, irrigation, monitoring, and automated local drug delivery in subarachnoid hemorrhage

OBJECTIVE

The management of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage (aSAH) remains one of the most important targets for neurocritical care. Advances in monitoring technology have facilitated a more thorough understanding of the pathophysiology and therapeutic approaches, but interventions are generally limited to either systemic therapies or passive CSF drainage. The authors present a novel approach that combines a multimodal monitoring bolt-based system with an irrigating ventricular drain capable of delivering intrathecal medications and describe their early experience in patients with aSAH.

METHODS

The authors performed a retrospective review of cases treated with the combined Hummingbird multimodal bolt system and the IRRAflow irrigating ventriculostomy.

RESULTS

Nine patients were treated with the combined multimodal bolt system with irrigating ventriculostomy approach. The median number of days to clearance of the third and fourth ventricles was 3 days in patients with obstructive intraventricular hemorrhage. Two patients received intrathecal alteplase for intraventricular hemorrhage clearance, and 2 patients received intrathecal nicardipine as rescue therapy for severe symptomatic angiographic vasospasm.

CONCLUSIONS

Combined CSF drainage, irrigation, multimodality monitoring, and automated local drug delivery are feasible using a single twist-drill hole device. Further investigation of irrigation settings and treatment approaches in high-risk cases is warranted.

Intraoperative navigation in surgical management of traumatic spine injury: a propensity score matching analysis

BACKGROUND

Traumatic spinal injury (TSI) can lead to severe morbidity and significant health care resource utilization. Intraoperative navigation (ION) systems have been shown to improve outcomes in some populations. However, controversy about the benefit of ION remains. To our knowledge, there is no large database analysis studying the outcomes of ION on TSI patients. Here we hope to compare complications and outcomes in patients with TSI undergoing spinal fusion of 3 or more levels with or without the use of ION.

METHODS

The 2015-2019 National Surgical Quality Improvement Program (NSQIP) database was queried for cases of posterior spinal instrumentation of 3 or more levels. This population was then selected for postoperative diagnosis consistent with TSI. The effect of prolonged operative time was analyzed for all patients. Propensity score matching analysis was performed to create ION case and non-ION control groups. Baseline demographic characteristics, complications, and outcome data were collected and compared between ION and non-ION groups.

RESULTS

A total of 1,034 patients were included in the propensity matched analysis. Among comorbidities, only obesity was significantly more likely in the non-ION group. There was no difference in case complexity between the two groups. ION was associated with higher incidence of prolonged operative time but was a negative independent predictor for sepsis. Prolonged operative time was a significant independent predictor for pulmonary embolism and requirement of transfusion in all patients. Discharge to home, readmission, and reoperation rates did not differ between TSI patients with or without ION.

CONCLUSIONS

Use of ION during posterior spinal fusion of 3 or more levels in TSI patients is not associated with worse outcomes. Prolonged operative time, rather than ION, appears to have a higher influence on the rate of complications in this population. Evaluation of ION in the context of specific populations and pathology is warranted to optimize its use.

Frailty Status Is a More Robust Predictor Than Age of Spinal Tumor Surgery Outcomes: A NSQIP Analysis of 4,662 Patients

Objective

The present study aimed to evaluate the effect of baseline frailty status (as measured by modified frailty index-5 [mFI-5]) versus age on postoperative outcomes of patients undergoing surgery for spinal tumors using data from a large national registry.

Methods

The National Surgical Quality Improvement Program database was used to collect spinal tumor resection patients’ data from 2015 to 2019 (n = 4,662). Univariate and multivariate analyses for age and mFI-5 were performed for the following outcomes: 30-day mortality, major complications, unplanned reoperation, unplanned readmission, hospital length of stay (LOS), and discharge to a nonhome destination. Receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminative performance of age versus mFI-5.

Results

Both univariate and multivariate analyses demonstrated that mFI-5 was a more robust predictor of worse postoperative outcomes as compared to age. Furthermore, based on categorical analysis of frailty tiers, increasing frailty was significantly associated with increased risk of adverse outcomes. ‘Severely frail’ patients were found to have the highest risk, with odds ratio 16.4 (95% confidence interval [CI],11.21–35.44) for 30-day mortality, 3.02 (95% CI, 1.97–4.56) for major complications, and 2.94 (95% CI, 2.32–4.21) for LOS. In ROC curve analysis, mFI-5 score (area under the curve [AUC] = 0.743) achieved superior discrimination compared to age (AUC = 0.594) for mortality.

Conclusion

Increasing frailty, as measured by mFI-5, is a more robust predictor as compared to age, for poor postoperative outcomes in spinal tumor surgery patients. The mFI-5 may be clinically used for preoperative risk stratification of spinal tumor patients.

Nationwide trends in middle meningeal artery embolization for treatment of chronic subdural hematoma: A population-based analysis of utilization and short-term outcomes

Middle meningeal artery (MMA) embolization represents a promising novel treatment modality for chronic subdural hematoma (cSDH), yet utilization and efficacy data are limited. This study evaluates the utilization and short-term outcomes of MMA embolization for cSDH treatment in a large national inpatient registry. cSDH patients treated with MMA embolization and/or surgical evacuation (craniotomy/burr hole drainage) were identified using the National Inpatient Sample (NIS) during 2012-2018 period. Temporal trends, complications, and discharge disposition were evaluated, and propensity score matching was implemented for adjusted comparisons and to mitigate confounding by indication. Among 60,045 cSDH patients identified, 390 (0.6%) underwent MMA embolization. Embolized patients presented more with high acute illness severity subclasses in comparison with surgically evacuated patients (53% vs. 34%, p = 0.004) yet did not experience any procedure-related hemorrhagic or ischemic complications. Although discharge disposition did not differ from those surgically managed, embolized patients had longer mean hospital stays (13 vs. 8 days, p = 0.023) and accrued greater hospital charges (p < 0.001). Following propensity adjustment, length of stay and charges remained greater in the embolization cohort, yet rates of routine discharge increased appreciably (40% vs. 30%, p = 0.141) relative to surgically treated cSDH patients. The utilization of embolization increased exponentially after 2015, reaching an apex in 2018 (3.7% of treated cSDH). This population-based national assessment demonstrates exponential increases in utilization of MMA embolization for cSDH treatment in recent years. Embolized patients had uncomplicated clinical courses and similar discharge dispositions as surgical evacuation patients. Large-scale prospective trials are warranted to further assess the efficacy of this modality.

Demographics and Outcomes of Interhospital Transfer Patients Undergoing Intracranial Tumor Resection: A Retrospective Cohort Analysis

Introduction

Interhospital transfer (IHT) contributes to increasing health care costs and typically accounts for increased patient morbidity and mortality compared to non-IHT patients. IHT inefficiencies leave patients vulnerable to delayed care and subsequent poor outcomes. In this study, we investigated factors influencing IHT of patients undergoing intracranial tumor resection (ITR), by comparing the variables distinguishing IHTs from non-IHT patients.

Methods

We performed a single-center retrospective review comparing IHT and non-IHT patients undergoing ITR from 2016 to 2018. Study variables included age, sex, race, the Milan Complexity Scale (MCS) score, 11-factor modified frailty index (mFI-11), length of stay (LOS), and Clavien-Dindo Score (CDS). Chi-square and Mann-Whitney U tests were used to identify significant differences in these variables between groups, while variables predictive of transfer status were identified using binary logistic regression.

Results

Data were collected from 219 patients undergoing ITR, with 80 (36.5%) IHT patients overall. The average age was 52 years (SD 18) and 57.7% were men. The MCS score was significantly higher in the IHT group (p = 0.014); however, mFI-11 was not (p = 0.322). The MCS score was predictive of IHT status in regression analysis (OR 1.17, p = 0.034). The IHT patients had a longer LOS (12 days vs 8 days, p = 0.014) with a lower CDS (p = 0.02).

Conclusion

The transfer patients for intracranial tumor resection had a higher MCS score and thus comprised a more surgically challenging population compared to non-transfer patients. As expected, IHT patients had a longer LOS as they lived further from hospital by definition.

A Perennial Threat: A Case Series of Tree-Related Neurotrauma

Background

Despite their devastating nature, injuries due to tree-related- traumas are sparsely reported in the literature. Over the last several years, the incidence of tree-related traumatic injuries presenting to our level one trauma center, in Westchester, New York, has been concerning. The present study was undertaken to evaluate the clinical presentation, injury pattern, and outcomes of tree-related neurotrauma at our institution. In addition, we describe the injury pattern and medical management of several relevant cases of tree-related neurotrauma.

Methods

We conducted a retrospective analysis of tree-related neurotrauma over a five-year period from January of 2014 to March of 2019 at Westchester Medical Center (WMC) and Maria Fareri Children’s Hospital, a level one trauma center. Patients presenting with neurotrauma that necessitated neurosurgical care were eligible for inclusion in this case series. Tree-related injury was defined as any trauma that was sustained as a direct result of collision with a tree.

Results

We identified 21 patients who sustained tree-related trauma. The cohort age ranged from 15 to 68 (mean=38 years). Injuries included seven skull fractures, four cases of subdural hematoma (SDH), six cases of intracranial hemorrhagic contusion, 14 spinal fractures, three cases of epidural hematoma (EDH), one case of spinal cord contusion, three vascular injuries, one case of dural laceration, and one case of pneumocephalus, with several patients suffering multiple injuries. Of the 21 patients, seven were female, and 12 were injured when their motor vehicle struck a tree. All but four patients were taken to the operating room for neurosurgical treatment, and nine of 21 patients were taken emergently to the operating room upon arrival.

Conclusion

The potential for serious head injuries with long-term neurologic sequelae exists with tree-related trauma. Clinicians should be advised of the challenging management of injuries secondary to tree-related trauma, and a greater emphasis should be placed on raising awareness of these accidental, but devastating injuries. Finally, a great majority of these injuries can be prevented or reduced in severity through helmet use and by adhering to safety guidelines.

Spine surgery complexity score predicts outcomes in 671 consecutive spine surgery patients

Background:

The spine surgery complexity score (SSCS), previously reported by us, is a simple grading system to predict postoperative complications and hospital length of stay (LOS). This scale is based on the technical difficulty of the spinal procedures being performed.

Methods:

We performed a retrospective chart review to validate SSCS in 671 consecutive patients undergoing spine procedures at a quaternary academic hospital.

Results:

The SSCS was predictive of the hospital LOS and postoperative complications (defined by the ClavienDindo score), based on linear regression analysis (P < 0.001 for both).

Conclusion:

Categorizing procedures according to the SSCS may enable neurosurgeons to assess surgical risk and predict longer LOS courses after spine surgery. Thus, it may prove useful in preoperative patient evaluation/ education and determining a prognosis based on surgical complexity.

The modified vaccination technique designed to prevent and cure acute and chronic disorders

In spite of enormous efforts there have been no solutions to date for preventing/terminating certain acute and chronic disorders of humans by vaccination or drugs. Yet it is well understood that if the target antigen (ag) could be presented appropriately to the cells of the immune system then solutions could be found. Recently, the Barabas research group has introduced and described the third vaccination method - called modified vaccination technique (MVT) - which has the ability to provide a corrective immune response in experimental animals with an autoimmune kidney disease. Injections of immune complexes - made up of the target ag and specific non-pathogenic IgM antibodies directed against the target ag - achieved downregulation of pathogenic immune responses and tolerance to self was regained. Utilizing the immune system's natural abilities to respond to corrective information, the MVT technique was able to prevent an autoimmune kidney disease from occurring (prophylactic effect) in experimental animals, and when present, terminating it (therapeutic effect) specifically and without measurable side effects.It is predicted that the application of the MVT will have the potential in the future to revolutionize the preventative and therapeutic options for dealing with chronic disorders in humans (such as autoimmune disease, cancer and acute chronic infections) and achieve cures.

Evaluation of a D-Dimer Protocol for Detection of Venous Thromboembolism

BACKGROUND

The use of venous duplex ultrasonography (VDU) for confirmation of deep venous thrombosis in neurosurgical patients is costly and requires experienced personnel. We evaluated a protocol using D-dimer levels to screen for venous thromboembolism (VTE), defined as deep venous thrombosis and asymptomatic pulmonary embolism.

METHODS

We used a retrospective bioinformatics analysis to identify neurosurgical inpatients who had undergone a protocol assessing the serum D-dimer levels and had undergone a VDU study to evaluate for the presence of VTE from March 2008 through July 2017. The clinical risk factors and D-dimer levels were evaluated for the prediction of VTE.

RESULTS

In the 1918 patient encounters identified, the overall VTE detection rate was 28.7%. Using a receiver operating characteristic curve, an area under the curve of 0.58 was identified for all D-dimer values (P = 0.0001). A D-dimer level of ≥2.5 μg/mL on admission conferred a 30% greater relative risk of VTE (sensitivity, 0.43; specificity, 0.67; positive predictive value, 0.27; negative predictive value, 0.8). A D-dimer value of ≥3.5 μg/mL during hospitalization yielded a 28% greater relative risk of VTE (sensitivity, 0.73; specificity, 0.32; positive predictive value, 0.24; negative predictive value, 0.81). Multivariable logistic regression showed that age, male sex, length of stay, tumor or other neurological disease diagnosis, and D-dimer level ≥3.5 μg/mL during hospitalization were independent predictors of VTE.

CONCLUSIONS

The D-dimer protocol was beneficial in identifying VTE in a heterogeneous group of neurosurgical patients by prompting VDU evaluation for patients with a D-dimer values of ≥3.5 μg/mL during hospitalization. Refinement of this screening model is necessary to improve the identification of VTE in a practical and cost-effective manner.

Utility of intraoperative rotational thromboelastometry in thoracolumbar deformity surgery

OBJECTIVE Blood loss during surgery for thoracolumbar scoliosis often requires blood product transfusion. Rotational thromboelastometry (ROTEM) has enabled the more targeted treatment of coagulopathy, but its use in deformity surgery has received limited study. The authors investigated whether the use of ROTEM reduces transfusion requirements in this case-control study of thoracolumbar deformity surgery. METHODS Data were prospectively collected on all patients who received ROTEM-guided blood product management during long-segment (≥ 7 levels) posterior thoracolumbar fusion procedures at a single institution from April 2015 to February 2016. Patients were matched with a group of historical controls who did not receive ROTEM-guided therapy according to age, fusion segments, number of osteotomies, and number of interbody fusion levels. Demographic, intraoperative, and postoperative transfusion requirements were collected on all patients. Univariate analysis of ROTEM status and multiple linear regression analysis of the factors associated with total in-hospital transfusion volume were performed, with p < 0.05 considered to indicate statistical significance. RESULTS Fifteen patients who received ROTEM-guided therapy were identified and matched with 15 non-ROTEM controls. The mean number of fusion levels was 11 among all patients, with no significant differences between groups in terms of fusion levels, osteotomy levels, interbody fusion levels, or other demographic factors. Patients in the non-ROTEM group required significantly more total blood products during their hospitalization than patients in the ROTEM group (8.5 ± 4.2 units vs 3.71 ± 2.8 units; p = 0.001). Multiple linear regression analysis showed that the use of ROTEM (p = 0.016) and a lower number of fused levels (p = 0.022) were associated with lower in-hospital transfusion volumes. CONCLUSIONS ROTEM use during thoracolumbar deformity correction is associated with lower transfusion requirements. Further investigation will better define the role of ROTEM in transfusion during deformity surgery.

A novel modified vaccination technique produces IgG antibodies that cause complement-mediated lysis of multiple myeloma cells carrying CD38 antigen

Objectives were to: 1) induce a lytic IgG antibody (ab) response (via the so called `third vaccination method') against CD38 antigen (ag) residing on the extra-cellular domain of multiple myeloma (MM) cells in recipient rabbits, by combining the CD38 ag with donor-derived anti-CD38 ag lytic IgG ab into an immune complex (IC); and 2) determine whether abs produced would cause complement-mediated lysis (in vitro) of human MM cells containing CD38 ag. The vaccine was created in a two-step process. First, ab (rabbit anti-CD38 ag IgG ab) was raised in donor rabbits by injections of low molecular weight soluble CD38 ag in Freund's complete adjuvant (FCA) and aqueous solution. Second, transfer of pathogenic lytic IgG ab response into recipient rabbits was achieved by injections of ICs composed of CD38 ag and homologous anti-CD38 ag IgG ab. Consequently, recipient rabbits produced the same ab with the same specificity against the target ag as was present in the inoculum, namely agglutinating, precipitating and lytic (as demonstrated in vitro). In an in vitro study, in the presence of complement, donor and recipient rabbits' immune sera caused lysis of CD38 ag associated human MM cells. The most effective lytic ab response causing sera were those from donor rabbits injected with CD38 ag in FCA and those from rabbits injected with ICs, especially when they were administered in adjuvants. These results provided proof of concept that the third vaccination method has good potential as a stand-alone and efficacious method of controlling cancer.

Suppression of tumor growth by a heterologous antibody directed against multiple myeloma dominant CD38 antigen in SCID mice injected with multiple myeloma cells

Employing passive immunization - using a heterologous anti-CD38 IgG antibody containing serum - in SCID mice injected subcutaneously with human multiple myeloma cells, we have shown that treatments with the antiserum - especially in the presence of complement - significantly decreased cancer growth. However, administered antibody and complement was not sufficient in amount to prevent cancer cell multiplication and cancer growth expansion to a satisfactory degree. Larger volumes of the same components more than likely would have further reduced cancer growth and prolonged the life of mice. In control mice, cancer growth progressed faster proving that lytic immune response against multiple myeloma cells is necessary for cancer cell kill.

Production of heterologous IgG antibody against Heymann nephritis antigen by injections of immune complexes

Heterologous IgG antibody (ab) can be produced against Heymann nephritis (HN) antigen (ag) in rabbits by administering it in Freund's complete adjuvant. The developing abs reacted at high titre with rat kidney brush border (BB) regions of the renal proximal tubules in an indirect fluorescence ab test. A single IV injection of the heterologous ab into a susceptible strain of rat resulted in the localization of IgG ab to glomerular fixed ags, producing immune complex glomerular nephritis. The injected ab also reacted with the BB region of the renal proximal tubules. The aim of this experiment was to find out whether heterologous IgG ab against the HN ag can also be produced in recipient rabbits by injecting immune complexes (ICs) composed of a rat kidney tubular preparation [rat kidney fraction 3 (rKF3)] and donor rabbit-derived rabbit anti-rKF3 IgG ab. We found that anti-rKF3 IgG ab--against the BB region of the renal proximal tubules--could be induced in rabbits injected with ICs, and the resulting ab was able to initiate passive HN in rats. This was the first time a pathogenic IgG ab was produced against HN ag in rabbits without the use of adjuvant. Ab responses in recipient rabbits were achieved by ab information transfer. Recipient rabbits injected with the IC produced the same class of immunoglobulin with the same specificity against the target ag rKF3, as was present in the innoculum, namely rabbit anti-rKF3 IgG ab.

Rathke cleft cyst presenting with hyponatremia: an unusual presentation

The authors report a case of Rathke cleft cyst presenting with severe hyponatremia. A 33-year-old man suffered sudden severe headaches, visual changes, dizziness, nausea, vomiting, and a metallic taste in his mouth. Initial laboratory values demonstrated severe hyponatremia. Magnetic resonance imaging revealed a cystic lesion with questionable intracystic hemorrhage, concerning for pituitary apoplexy. Transsphenoidal decompression and drainage of the cyst confirmed the diagnosis of Rathke cleft cyst and resolved the symptoms. Postoperative follow-up studies at 6 months demonstrated normal endocrine function and no evidence of a cyst.

Hemangiopericytomas of the spine: case report and review of the literature

We describe a rare case of a primary intracranial meningeal hemangiopericytoma (HPC) with late metastasis to the cervical spine. A 36-year-old woman had a left occipital lesion that was histopathologically identified as HPC. Fourteen years after resection, the tumor recurred and was treated with radiotherapy. Three years later, CT imaging showed a large mass in the liver consistent with metastatic HPC, and MRI of the cervical spine showed an extensive lesion of the C3 vertebral body. The patient underwent C3 corpectomy with en-bloc tumor removal and follow-up radiation with no local recurrence or other spinal metastasis for the following 4 years. Regardless of the subtype of spinal HPC, complete surgical removal and radiotherapy appear to be treatment of choice.

Noncontact dipole effects on channel permeation. III. Anomalous proton conductance effects in gramicidin

Proton transport on water wires, of interest for many problems in membrane biology, is analyzed in side-chain analogs of gramicidin A channels. In symmetrical 0.1N HCl solutions, fluorination of channel Trp(11), Trp-(13), or Trp(15) side chains is found to inhibit proton transport, and replacement of one or more Trps with Phe enhances proton transport, the opposite of the effects on K(+) transport in lecithin bilayers. The current-voltage relations are superlinear, indicating that some membrane field-dependent process is rate limiting. The interfacial dipole effects are usually assumed to affect the rate of cation translocation across the channel. For proton conductance, however, water reorientation after proton translocation is anticipated to be rate limiting. We propose that the findings reported here are most readily interpreted as the result of dipole-dipole interactions between channel waters and polar side chains or lipid headgroups. In particular, if reorientation of the water column begins with the water nearest the channel exit, this hypothesis explains the negative impact of fluorination and the positive impact of headgroup dipole on proton conductance.

Preventative and therapeutic vaccination to combat an experimental autoimmune kidney disease

We describe a new vaccination method called modified vaccination technique (MVT). The technique is able to achieve downregulation of pathogenic autoimmune events leading to a chronic progressive disorder in rats called slowly progressive Heymann nephritis. Downregulation of immunopathological events is achieved by injections of immune complex (IC) made up of the target native antigen (ag) and specific naturally occurring immunoglobulin M (IgM) antibody (ab) directed against it. Repeated injections of IC maintain high levels of specific circulating IgM autoantibodies (aabs) against the kidney ag. The developing physiologic IgM aabs assist in the catabolism of both modified and unmodified renal ags from the circulation. No disease-causing renal ags in the circulation results in no stimulation of pathogenic immunoglobulin G aab producing cell lines. Such specific targeted therapy leads to termination of disease-causing processes and reestablishment of tolerance. The MVT can be employed both prophylactically and therapeutically with equal effectiveness. A redirected immune response is achieved by specifically stimulating the animals' own IgM-producing cell lines with the injected ICs, resulting in a natural cure. Such ICs are nontoxic and nonirritant and cause no side effects. We surmise that the MVT, employing the appropriate components in each instance, can also be used to treat human ailments.

Spinal extradural arachnoid cysts: clinical, radiological, and surgical features

Extradural arachnoid cysts in the spine are rare and are seldom a cause of spinal cord compression. They are thought to arise from congenital defects in the dura mater, and they almost always communicate with the intrathecal subarachnoid space through a small defect in the dura. The mainstay of treatment in patients with neurological symptoms is surgical removal of the cyst together with ligation of the communicating pedicle and closure of the dural defect. In the present paper the authors review the literature and discuss the clinical and pathological features, mechanisms of pathogenesis, neuroimaging characteristics, and surgical management of spinal extradural arachnoid cysts. The surgical technique for removal of these lesions is illustrated in a patient with a large thoracolumbar spinal extradural arachnoid cyst causing neurogenic claudication.

Patterns of skull base meningioma progression after failed radiosurgery

Object

Stereotactic radiosurgery has been reported to be an effective alternative to surgical removal of small to medium benign meningiomas as well as an adjuvant treatment modality to reduce the risk of tumor progression after subtotal resection. Its efficacy has been proved by excellent short-term radiosurgically demonstrated control rates, which have been reported to approach or exceed 90% in many contemporary studies involving the use of either linear accelerator–based systems or the Gamma Knife. Little is known, however, regarding the growth patterns of meningiomas that fail to stabilize after radiosurgery.

Methods

The authors report 13 cases of benign skull base meningiomas (World Health Organization Grade I) that demonstrated progression after radiosurgical treatment as a primary or an adjuvant therapy. Several tumors demonstrated rapid growth immediately after radiosurgical treatment, whereas other lesions progressed in a very delayed manner in some patients (up to 14 years after treatment). Regardless of the interval after which it occurs, tumor growth can be quite aggressive once it has begun.

Conclusions

Skull base meningioma growth can be aggressive after failed radiosurgery in some patients, and treatment failure can occur at long intervals following treatment. Special attention must be devoted to such significant occurrences given the increasing number of patients undergoing stereotactic radiosurgery for benign tumors, and careful extended (> 10 years) follow up must be undertaken in all patients after radiosurgery.

Reduced incidence of slowly progressive Heymann nephritis in rats immunized with a modified vaccination technique

A slowly progressive Heymann nephritis (SPHN) was induced in three groups of rats by weekly injections of a chemically modified renal tubular antigen in an aqueous medium. A control group of rats received the chemically unmodified version of the antigen in an aqueous solution. One group of SPHN rats were pre- and post-treated with weekly injections of IC made up of rKF3 and rarKF3 IgM antibody at antigen excess (MIC) (immune complexes [ICs] containing sonicated ultracentrifuged [u/c] rat kidney fraction 3 [rKF3] antigen and IgM antibodies specific against the antigen, at slight antigen excess). One group of SPHN rats were post-treated with MIC 3 weeks after the induction of the disease and one group of SPHN animals received no treatment. The control group of rats received pre- and post-treatment with sonicated u/c rKF3.

The incidence of immune-complex glomerulonephritis (ICGN) in the untreated SPHN rats was 87%, in the pre- and post-treated animals 13%, and in the post-treated-only rats 20%. Rats receiving sonicated ultracentrifuged rKF3 antigen did not develop ICGN.

The present experiment demonstrates that the development of SPHN can be not only prevented but also effectively terminated by our newly developed modified vaccination technique.

Harvey Cushing and Oskar Hirsch: early forefathers of modern transsphenoidal surgery

The transnasal transsphenoidal approach is the preferred route for removal of most lesions of the sella turcica. The concept of transnasal surgery traversing the sphenoid sinus to reach the sella has existed for nearly a century. A comprehensive historical overview of the evolution of transsphenoidal surgery has been reported previously. In the present vignette, the authors focus on transsphenoidal surgery in the early 1900s, particularly on the methods advocated by Harvey Cushing and Oskar Hirsch, two prominent pituitary surgeons who pioneered the transsphenoidal technique. Cushing championed the sublabial approach, whereas Hirsch was the master of the endonasal route. Coincidentally, both surgeons independently performed the submucous septal resection for the first time on June 4, 1910. Although Cushing's and Hirsch's approaches were predicated on the work of their predecessors, their transsphenoidal procedures became the two most popular techniques and, for future generations of pituitary surgeons, laid the foundation for modem transsphenoidal surgery. In this comparative analysis, the authors compare the operative nuances of the approaches of Cushing and Hirsch and describe the contributions of these pioneers to modern transsphenoidal surgery.

Noncommunicating spinal extradural arachnoid cyst causing spinal cord compression in a child

Extradural arachnoid cysts in the spine are relatively uncommon causes of spinal cord compression in the pediatric population that are thought to arise from congenital defects in the dura mater. Most reports describe such cysts communicating with the intrathecal subarachnoid space through a small defect in the dura. The authors describe the case of a child who presented with spinal cord compression caused by a large spinal extradural arachnoid cyst that did not communicate with the intradural subarachnoid space. An 11-year-old girl presented with urinary urgency, progressive lower-extremity weakness, myelopathy, and severe gait ataxia. Magnetic resonance imaging of the spine demonstrated a large extradural arachnoid cyst extending from T-8 to T-12. The patient underwent a thoracic laminoplasty for en bloc resection of the spinal extradural arachnoid cyst. Intraoperatively, the dura was intact and there was no evidence of communication into the intradural subarachnoid space. Postoperatively, the patient's motor strength and ambulation improved immediately, and no subsequent cerebrospinal fluid leak occurred. Noncommunicating spinal extradural arachnoid cysts are extremely rare lesions that can cause spinal cord compression in children. Because the dura remains intact, they can be removed entirely without subsequent dural repair. The authors review the literature and discuss the proposed underlying mechanisms of formation of these arachnoid cysts.

Cranial base strategies for resection of craniopharyngioma in children

The optimal treatment of craniopharyngioma in children remains a challenge. The use of complete excision to minimize recurrence continues to be controversial because of the risk of postoperative morbidity and death. Advances in skull base approaches, modern microsurgical techniques, neuroimaging, and hormone replacement therapy, however, have allowed safe gross- or near-total resection in the majority of cases. Total removal of these tumors, if possible, offers the best chance of cure for the patient. Although craniopharyngiomas are not strictly tumors of skull base origin, their intimate relationship with the neurovascular structures of this region often requires a skull base approach to maximize the surgical corridor and facilitate adequate microsurgical resection. In this review, the authors focus on commonly used skull base approaches for the surgical management of craniopharyngioma. They discuss the relative indications, advantages, disadvantages, and complications associated with each approach. Illustrative cases and intraoperative videos are presented.

Cranial base strategies for resection of craniopharyngioma in children

The optimal treatment of craniopharyngioma in children remains a challenge. The use of complete excision to minimize recurrence continues to be controversial because of the risk of postoperative morbidity and death. Advances in skull base approaches, modern microsurgical techniques, neuroimaging, and hormone replacement therapy, however, have allowed safe gross- or near-total resection in the majority of cases. Total removal of these tumors, if possible, offers the best chance of cure for the patient. Although craniopharyngiomas are not strictly tumors of skull base origin, their intimate relationship with the neurovascular structures of this region often requires a skull base approach to maximize the surgical corridor and facilitate adequate microsurgical resection. In this review, the authors focus on commonly used skull base approaches for the surgical management of craniopharyngioma. They discuss the relative indications, advantages, disadvantages, and complications associated with each approach. Illustrative cases and intra-operative videos are presented.

Historical perspectives on the diagnosis and treatment of trigeminal neuralgia

Since the earliest recorded history of medicine, physicians have been challenged by the difficulty in relieving the great pain experienced by individuals suffering from trigeminal neuralgia (TN). The nature of the pain and the events that incite it have been well described, but effective treatments with acceptable levels of side effects remained elusive until the latter part of the 20th century. As a result, many theories about the origins of TN have been proposed, along with numerous treatment modalities. The pathophysiological causes of TN remain incompletely understood, but the medical and surgical treatment techniques currently used offer effective ways to relieve this extremely painful condition. In this historical review the authors discuss the initial descriptions of tic douloureux, Fothergill disease, and TN, along with various therapeutic interventions and their refinements.

Presence of immunoglobulin M antibodies around the glomerular capillaries and in the mesangium of normal and passive Heymann nephritis rats

Summary Diffuse distribution of small, faintly staining, beaded deposits of rat immunoglobulin M (IgM) around the glomerular capillary blood vessels, and a more intensely staining larger deposition in the mesangium, were observed on the kidney sections of normal rats. As glomerular-fixed nephritogenic antigens are known to be present on the epithelial aspect of the glomerular basement membrane (GBM), especially at the soles of foot processes and at the slit pores, it was assumed that the IgM antibodies were directed against these antigens. Investigation by immunofluorescent antibody double-staining techniques of rat kidney sections obtained from normal and rabbit anti-FX1A-injected rats stained for the nephritogenic antigen showed that a number of antigenic sites in the glomeruli and in the mesangium shared antibody hits by heterologous rabbit IgG and autologous rat IgM antibodies. Most sites in the glomeruli stained specifically for rat IgM or rabbit IgG, but preferentially for the latter. The intensely fluorescent mesangial deposits stained mainly for rat IgM, indicating that at these sites the antigenic material was virtually saturated, while areas at the entry to the mesangial space also stained for rabbit IgG, indicating that at these locations free nephritogenic epitopes were still available for reaction with the anti-FX1A antibody. Western blot analysis have shown that the rabbit anti-rat FX1A IgG and the rat anti-rat KF3 IgM antibodies are directed against the same renal tubular-derived antigen with a molecular weight of 70,000. These experimental findings collectively demonstrate that the heterologous IgG and autologous IgM antibodies are directed against the same nephritogenic antigen, which is found in the glomeruli, the mesangium and the proximal convoluted tubules. Thus, the IgM autoantibody has a possible physiological role but, in addition, there is evidence of active immunophagocytic events, manifested in a rapid and continuous entrapment and expulsion of macromolecules after their processing by the mesangial cells of normal and passive Heymann nephritis rats.

Down-regulation of pathogenic autoantibody response in a slowly progressive Heymann nephritis kidney disease model

In the present article, we describe an antigen-specific down-regulation of a pathogenic autoantibody (aab)-mediated disease process in an experimental autoimmune kidney disease in rats called slowly progressive Heymann nephritis (SPHN). This autoimmune disease is initiated and maintained by pathogenic immunoglobulin G (IgG) autoantibodies (aabs), which cause an immune-complex (IC) glomerulonephritis associated with proteinuria. We achieved down-regulated pathogenic aab response in SPHN rats by injections of an IC containing the native nephritogenic antigen and specific high-titred nonpathogenic IgM aabs, in antigen excess. The injected IC increased the level of circulating nonpathogenic IgM aabs; the increased levels of specific IgM aabs in turn facilitated the removal of the injected altered nephritogenic and liberated autoantigens from the renal tubules and greatly diminished the production of pathogenic aabs and the build up of immune deposits in the glomeruli. While animals treated early had advantages over rats whose kidney disease was well established before treatment; animals treated late into the disease still manifested noticeable improvements in similar areas, i.e. with lessened proteinuria, kidney lesion reduction and a decreased pathogenic aab response. At the end of the experiment at 29 weeks, 80% of all the treated rats had insignificantly low levels of circulating IgG aabs, indicating cessation of pathogenic aab production and corresponding termination of the disease process. In contrast, most untreated rats with the kidney disease still had high levels of circulating pathogenic aabs at the end of the experiment, which maintained disease progression.

Production of Heymann nephritis by a chemically modified renal antigen

An autoimmune kidney disease morphologically and functionally similar to Heymann nephritis (HN) was induced in mature male Sprague Dawley rats by repeated weekly IP injections of a chemically modified azo sonicated ultracentrifuged (u/c) rat kidney fraction 3 (rKF3) antigen in an aqueous medium. The experiment was terminated 15 weeks after the first injection of the chemically altered antigen. Serum samples collected and analysed by an indirect fluorescent antibody test on normal rat kidney sections during the course of the experiment showed a gradual rise in circulating pathogenic autoantibodies directed against the proximal tubular brush border regions. Proteinuria was present and significantly increased in the urine of two of eight rats. The arising immune-complex glomerulonephritis (ICGN) revealed typical HN kidney disease lesions in 70% of the rats in histological, direct fluorescent antibody and electron-microscopical examinations. Control rats injected similarly with the an unmodified version of the same antigen did not develop the HN-characteristic morphological and functional changes. To our knowledge, this is the first time that the autoimmune kidney disease designated as an active HN has been produced by the administration of a chemically altered renal antigen in an aqueous solution and not by the usual presentation of the nephritogenic renal antigen in an adjuvant.

Hyponatremia in the neurosurgical patient: diagnosis and management

Hyponatremia is frequently encountered in patients who have undergone neurosurgery for intracranial processes. Making an accurate diagnosis between the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting (CSW) in patients in whom hyponatremia develops is important because treatment differs greatly between the conditions. The SIADH is a volume-expanded condition, whereas CSW is a volume-contracted state that involves renal loss of sodium. Treatment for patients with SIADH is fluid restriction and treatment for patients with CSW is generally salt and water replacement. In this review, the authors discuss the differential diagnosis of hyponatremia, distinguish SIADH from CSW, and highlight the diagnosis and management of hyponatremia, which is commonly encountered in patients who have undergone neurosurgery, specifically those with traumatic brain injury, aneurysmal subarachnoid hemorrhage, recent transsphenoidal surgery for pituitary tumors, and postoperative cranial vault reconstruction for craniosynostosis.

Porous polyethylene implant for cranioplasty and skull base reconstruction

OBJECT

Cranial reconstruction after skull base surgery is important for restoration of function and cosmesis. The authors describe their experience with the Medpor porous polyethylene implant for cosmetic cranioplasty and reconstruction after skull base surgery.

METHODS

Medpor, a biocompatible implant, is flexible and can be contoured to facilitate surgical reconstruction of small to medium (< 8 cm) convexity or cranial base defects resulting from a variety of skull base approaches. This method provides similar cosmetic results to standard alloplast cranioplasty while decreasing operating time. The porous nature of the material allows ingrowth of soft tissue and bone to increase implant strength and decrease the risk of infection. This material can also be used safely in reconstruction of the cranium and skull base adjacent to the paranasal sinuses.

CONCLUSIONS

The authors have used the Medpor porous polyethylene implant in 611 standard cranial and skull base procedures and have achieved excellent cosmetic results and no implant-related complications.

Production of a new model of slowly progressive Heymann nephritis

A slowly progressive autoimmune kidney disease was induced in Sprague Dawley rats by subcutaneous injection of a chemically modified kidney antigen (rKF3), incorporated into Alum and Distemper complex vaccine, followed by subcutaneous injections of an aqueous preparation of the same antigen. Pathogenic autoantibodies developed, which reacted with fixed glomerular nephritogenic antigen. Subsequently, immunopathological events lead to chronic progressive immune complex glomerulonephritis and proteinuria. The slowly developing disease was morphologically and functionally similar to Heymann nephritis (HN). The damage observed in the kidneys of experimental animals at 8 weeks and at the end of the experiment was examined by direct fluorescent antibody test, histology and electron microscopy. The changes were similar to the typical lesions found in HN rat kidneys, but less severe. Animals became proteinuric from 17 weeks onward (instead of the usual 4-8 weeks). By the end of the experiment, at 8 months, 100% of the rats were proteinuric. This new experimental model of autoimmune kidney disease, which is not complicated by intraperitoneal deposition and retention of Freund's complete adjuvant and renal tubular antigens, allowed us to investigate the pathogenesis of the disease processes from a different aspect, and promises to be a useful and improved model for the investigation of future treatment options.

Noncontact dipole effects on channel permeation. VI. 5F- and 6F-Trp gramicidin channel currents

Fluorination of peptide side chains has been shown to perturb gramicidin channel conductance without significantly changing the average side chain structure, which, it is hoped, will allow detailed analysis of electrostatic modulation of current flow. Here we report a 1312-point potassium current-voltage-concentration data set for homodimeric channels formed from gramicidin A (gA) or any of eight fluorinated Trp analogs in both lecithin and monoglyceride bilayers. We fit the data with a three-barrier, two-site, two-ion (3B2S) kinetic model. The fluorination-induced changes in the rate constants were constrained by the same factor in both lipids. The rate constant changes were converted to transition-state free-energy differences for comparison with previous electrostatic potential energy differences based on an ab initio force field. The model allowed a reasonably good fit (chi = 8.29 with 1271 degrees of freedom). The measured changes were subtle. Nevertheless, the fitted energy perturbations agree well with electrostatic predictions for five of the eight peptides. For the other three analogs, the fitted changes suggested a reduced translocation barrier rather than the reduced exit barrier as predicted by electrostatics.

Noncontact dipole effects on channel permeation. IV. Kinetic model of 5F-Trp(13) gramicidin A currents

Nonlinear least squares fitting was used to assign rate constants for the three-barrier, two-site, double-occupancy, single-filing kinetic model for previously reported current-voltage relations of (5F-Indole)Trp(13) gramicidin A and gramicidin A channels (, 75:2830-2844). By judicious coupling of parameters, it was possible to reduce the parameter space from 64 parameters to 24, and a reasonable fit consistent with other experimental data was obtained. The main features of the fit were that fluorination increased the rate constant for translocation by a factor of 2.33, consistent with a free energy change in the translocation barrier of -0.50 kcal/mol, and increased first-ion binding affinity by a factor of 1.13, primarily by decreasing the first-ion exit rate constant. The translocation rate constant was 5.62 times slower in diphytanoyl phosphatidylcholine (DPhPC) bilayers than in monoolein (GMO) bilayers (coupled for the four combinations of peptide and salt), suggesting a 44.2-mV difference in the projection of the interfacial dipole into the channel. Thus fluorination caused increased currents in DPhPC bilayers, where a high interfacial dipole potential makes translocation more rate limiting because the translocation barrier was reduced, and decreased currents in GMO bilayers, where ion exit or entry is rate limiting because these barriers were increased.

Noncontact dipole effects on channel permeation. I. Experiments with (5F-indole)Trp13 gramicidin A channels

Gramicidin A (gA), with four Trp residues per monomer, has an increased conductance compared to its Phe replacement analogs. When the dipole moment of the Trp13 side chain is increased by fluorination at indole position 5 (FgA), the conductance is expected to increase further. gA and FgA conductances to Na+, K+, and H+ were measured in planar diphytanoylphosphatidylcholine (DPhPC) or glycerylmonoolein (GMO) bilayers. In DPhPC bilayers, Na+ and K+ conductances increased upon fluorination, whereas in GMO they decreased. The low ratio in the monoglyceride bilayer was not reversed in GMO-ether bilayers, solvent-inflated or -deflated bilayers, or variable fatty acid chain monoglyceride bilayers. In both GMO and DPhPC bilayers, fluorination decreased conductance to H+ but increased conductance in the mixed solution, 1 M KCl at pH 2.0, where K+ dominates conduction. Eadie-Hofstee plot slopes suggest similar destabilization of K+ binding in both lipids. Channel lifetimes were not affected by fluorination in either lipid. These observations indicate that fluorination does not change the rotameric conformation of the side chain. The expected difference in the rate-limiting step for transport through channels in the two bilayers qualitatively explains all of the above trends.

Double-blind comparison of teicoplanin versus vancomycin in febrile neutropenic patients receiving concomitant tobramycin and piperacillin: effect on cyclosporin A-associated nephrotoxicity

A prospective, randomized, and double-blind study comparing teicoplanin with vancomycin in the initial management of febrile neutropenic patients was conducted. Teicoplanin was administered at 6 mg per kg of body weight every 24 h (q24h) intravenously (i.v.) after initial loading at 6 mg/kg q12h for three doses. Vancomycin was administered at 15 mg/kg q12h i.v. Patients also received piperacillin (3 g q4h i.v.) and tobramycin (1.5 to 2.0 mg/kg q8h i.v.). Of 53 patients enrolled, 50 were judged to be evaluable. Among these, 25 received teicoplanin and 25 received vancomycin. At enrollment, both groups were comparable in age, sex, renal function, underlying hematologic condition, and concurrent therapy. Both groups had similar sites of infection and microbial pathogens. Empirical antimicrobial therapy resulted in the cure of or improvement in 23 (92%) teicoplanin patients and 21 (84%) vancomycin patients (P = 0.67). Failures occurred with two vancomycin patients but no teicoplanin patients. Clinical response was indeterminate for two patients in each group. Adverse reactions occurred significantly more often in the vancomycin group than in the teicoplanin group (P = 0.01), and these reactions required the termination of the study regimens of 6 vancomycin versus 0 teicoplanin patients (P = 0.02). Nephrotoxicity was observed more frequently in the vancomycin group (10 versus 2 patients; P = 0.02). Subgroup analysis revealed a significant deterioration of renal function when vancomycin and cyclosporin A, but not teicoplanin and cyclosporin A, were used concurrently (P = 0.02). Among patients who received vancomycin and amphotericin B or teicoplanin and amphotericin B concurrently, deterioration in renal function was equivalent in both groups. Teicoplanin in the dosage employed was tolerated better than vancomycin in the empirical treatment of fever and neutropenia in our patient population.