Pulsed ultrasound expands the extracellular and perivascular spaces of the brain

Diffusion within the extracellular and perivascular spaces of the brain plays an important role in biological processes, therapeutic delivery, and clearance mechanisms within the central nervous system. Recently, ultrasound has been used to enhance the dispersion of locally administered molecules and particles within the brain, but ultrasound-mediated effects on the brain parenchyma remain poorly understood. We combined an electron microscopy-based ultrastructural analysis with high-resolution tracking of non-adhesive nanoparticles in order to probe changes in the extracellular and perivascular spaces of the brain following a non-destructive pulsed ultrasound regimen known to alter diffusivity in other tissues. Freshly obtained rat brain neocortical slices underwent sham treatment or pulsed, low intensity ultrasound for 5min at 1MHz. Transmission electron microscopy revealed intact cells and blood vessels and evidence of enlarged spaces, particularly adjacent to blood vessels, in ultrasound-treated brain slices. Additionally, ultrasound significantly increased the diffusion rate of 100nm, 200nm, and 500nm nanoparticles that were injected into the brain slices, while 2000nm particles were unaffected. In ultrasound-treated slices, 91.6% of the 100nm particles, 20.7% of the 200nm particles, 13.8% of the 500nm particles, and 0% of the 2000nm particles exhibited diffusive motion. Thus, pulsed ultrasound can have meaningful structural effects on the brain extracellular and perivascular spaces without evidence of tissue disruption.

Evolving Drug Delivery Strategies to Overcome the Blood Brain Barrier

The blood-brain barrier (BBB) poses a unique challenge for drug delivery to the central nervous system (CNS). The BBB consists of a continuous layer of specialized endothelial cells linked together by tight junctions, pericytes, nonfenestrated basal lamina, and astrocytic foot processes. This complex barrier controls and limits the systemic delivery of therapeutics to the CNS. Several innovative strategies have been explored to enhance the transport of therapeutics across the BBB, each with individual advantages and disadvantages. Ongoing advances in delivery approaches that overcome the BBB are enabling more effective therapies for CNS diseases. In this review, we discuss: (1) the physiological properties of the BBB, (2) conventional strategies to enhance paracellular and transcellular transport through the BBB, (3) emerging concepts to overcome the BBB, and (4) alternative CNS drug delivery strategies that bypass the BBB entirely. Based on these exciting advances, we anticipate that in the near future, drug delivery research efforts will lead to more effective therapeutic interventions for diseases of the CNS.

Abstract B46: Development of biodegradable Fn14-targeted nanoparticles for controlled drug delivery for invasive brain tumors

Introduction: A major limitation associated with treatment of glioblastoma (GBM), the most common and deadly primary brain cancer, is delivery of therapeutics to invading tumor cells outside of the area that is safe for surgical removal. Recent advances in nanotechnology have allowed the incorporation of different therapeutic and targeting agents into nanoparticles offering the potential for improved detection, prevention, and treatment of various cancers. A promising way to target brain-invading GBM cells is via targeted therapeutics that bind to the cell surface receptor fibroblast growth-factor-inducible 14 (Fn14), which is specifically upregulated on the surface of invading GBM cells.

Objective: In this study, we aim to develop a biodegradable nanoparticle platform that employs a dense, low-molecular weight PEG coating coupled with a Fn14-specific monoclonal antibody (mAb) in order to maximize brain tissue penetration and GBM cell targeting

Materials and Methods: We previously showed that PEG-coated model polystyrene (PS) nanoparticles conjugated to the Fn14 mAb named ITEM4 bind strongly and selectively to the Fn14 extracellular domain. We synthesized a variety of PS-based brain tissue penetrating PEG-coated nanoparticles and characterized the (i) specificity of nanoparticle binding to Fn14 and (ii) nonspecific binding to brain ECM components, using surface plasmon resonance (SPR) and multiple particle tracking (MPT) assays. In parallel, we are transferring these findings and methodology towards formulation of biodegradable drug-loaded nanoparticles with matched size, surface chemistries, and Fn14 binding affinities for controlled drug delivery into brain tumors. We are loading biodegradable nanoparticles, including poly(lactic-co-glycolic acid) (PLGA), polyglutamic acid (PGA), and polysebacic acid (PSA) polymer platforms, with chemotherapeutics (i.e. cisplatin and bis-chloroethylnitrosurea (BCNU)) to study the optimization of drug-loading with particle penetration and targeting.

Results: The equilibrium binding affinity (KD) of nanoparticles scaled nearly linear with the surface density of the ITEM4 molecules, indicating that the adhesiveness of nanoparticle formulations depends on the ITEM4 molecular presentation on the nanoparticle surface. PEG-coated Fn14-targeted nanoparticles of ~100 nm in diameter were able to rapidly penetrate brain tissue by MPT experiment in rat brain slices. In contrast, uncoated nanoparticles were immobilized in brain tissue. We have preliminary data that suggests we can develop biodegradable nanoparticles that provide sustained release of a wide range of rugs over several days. We have successfully encapsulated cisplatin and BCNU to the polymer backbone of PGA and PLGA containing a low-molecular weight PEG coating. Additional surface modifications have been made to enable Fn14 targeting by conjugating ITEM4 on the particle surface. Particles will undergo complete physicochemical characterization to optimize Fn14 targeting, nanoparticle movement, drug release kinetics, and in vivo efficacy.

Conclusion: We have developed a nanoparticle platform that can diffuse and penetrate within brain tissue and selectively target remote experimental GBM tumors. Using this approach we can optimize therapeutics versions to improve drug efficacy while limiting many of the side effects and risks of free drug and non-targeted therapies.

Citation Format: Jimena G. Perez, Craig S. Schneider, Nina Connolly, Jeffrey A. Winkles, Graeme F. Woodworth, Anthony J. Kim. Development of biodegradable Fn14-targeted nanoparticles for controlled drug delivery for invasive brain tumors. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B46.

Surface plasmon resonance as a high throughput method to evaluate specific and non-specific binding of nanotherapeutics

Surface plasmon resonance (SPR) is a powerful analytical technique used to quantitatively examine the interactions between various biomolecules, such as proteins and nucleic acids. The technique has been particularly useful in screening and evaluating binding affinity of novel small molecule and biomolecule-derived therapeutics for various diseases and applications including lupus medications, thrombin inhibitors, HIV protease inhibitors, DNA gyrase inhibitors and many others. Recently, there has been increasing interest in nanotherapeutics (nanoRx), due to their unique properties and potential for controlled release of encapsulated drugs and structure-specific targeting to diseased tissues. NanoRx offer the potential to solve many drug delivery challenges by enabling, specific interactions between molecules on the surface of the nanoparticle and molecules in the diseased tissue, while minimizing off-target interactions toward non-diseased tissues. These properties are largely dependent upon careful control and balance of nanoRx interactions and binding properties with tissues in vivo. Given the great promise of nanoRx with regard to engineering specific molecular interactions, SPR can rapidly quantify small aliquots of nanoRx formulations for desired and undesired molecular interactions. Moving forward, we believe that utilization of SPR in the screening and design of nanoRx has the potential to greatly improve the development of targeted nanoRx formulations and eventually lead to improved therapeutic efficacy. In this review, we discuss (1) the fundamental principles of SPR and basic quantitative analysis of SPR data, (2) previous applications of SPR in the study of non-particulate therapeutics and nanoRx, and (3) future opportunities for the use of SPR in the evaluation of nanoRx.

Preservation of the greater occipital nerve during suboccipital craniectomy results in a paradoxical increase in postoperative headaches

BACKGROUND

Injury to the greater occipital nerve (GON) during suboccipital/retrosigmoid craniectomy (SOC) has been postulated as an etiology of postoperative headaches (HAs). We hypothesized that severe postoperative HAs may be due to the division of the GON during dissection.

OBJECTIVE

To determine whether the GON plays an important role in the development of postoperative HAs.

METHODS

A retrospective review of prospectively accrued patients undergoing SOC by 1 neurosurgeon at Johns Hopkins from 1995 to 2009 was performed. A total of 280 patients were included in the study. HA was categorized into 3 groups according to the severity and impact on daily activities. Data were analyzed using a stepwise multivariate logistic regression analysis to identify independent factors associated with HA development. Patients with a history of preoperative HAs and migraine were excluded from the analysis.

RESULTS

In this cohort, new postoperative severe HAs at last follow-up visit were found in 19% of patients. By multivariate analysis, only GON preservation (relative risk: 1.49; 95% confidence interval: 1.00-2.34; P = 0.05) and wound infection (relative risk: 2.29; 95% confidence interval: 0.91-4.25; P = 0.07) were statistically significant. By univariate analysis, positive dependent associations included GON preservation (P < .01), reconstruction of the porus with hydroxyapatite cement (P = 0.02), and wound infection (P < 0.01). Statistically significant differences in the incidence of HA after surgery were found in patients in whom the GON was preserved compared with patients in whom the GON was divided (P = 0.035).

CONCLUSION

Postoperative debilitating HAs are a common complication after SOC. Although these HAs are probably multifactorial in nature, preservation of the GON during SOC is independently associated with postoperative debilitating HAs.

Highly PEGylated DNA Nanoparticles Provide Uniform and Widespread Gene Transfer in the Brain

Gene delivery to the central nervous system (CNS) has potential as a means for treating numerous debilitating neurological diseases. Nonviral gene vector platforms are tailorable and can overcome key limitations intrinsic to virus-mediated delivery; however, lack of clinical efficacy with nonviral systems to date may be attributed to limited gene vector dispersion and transfection in vivo. It is shown that the brain extracellular matrix (ECM) strongly limits penetration of polymer-based gene vector nanoparticles (NP) through the brain parenchyma, even when they are very small (<60 nm) and coated with a polyethylene glycol (PEG) corona of typical density. Following convection enhanced delivery (CED), conventional gene vectors are confined to the injection site, presumably by adhesive interactions with the brain ECM and do not provide gene expression beyond the point of administration. In contrast, it is found that incorporating highly PEGylated polymers allows the production of compacted (≈43 nm) and colloidally stable DNA NP that avoid adhesive trapping within the brain parenchyma. When administered by CED into the rat striatum, highly PEGylated DNA NP distribute throughout and provide broad transgene expression without vector-induced toxicity. The use of these brain-penetrating gene vectors, in conjunction with CED, offers an avenue to improve gene therapy for CNS diseases.

Minimizing the non-specific binding of nanoparticles to the brain enables active targeting of Fn14-positive glioblastoma cells

A major limitation in the treatment of glioblastoma (GBM), the most common and deadly primary brain cancer, is delivery of therapeutics to invading tumor cells outside of the area that is safe for surgical removal. A promising way to target invading GBM cells is via drug-loaded nanoparticles that bind to fibroblast growth factor-inducible 14 (Fn14), thereby potentially improving efficacy and reducing toxicity. However, achieving broad particle distribution and nanoparticle targeting within the brain remains a significant challenge due to the adhesive extracellular matrix (ECM) and clearance mechanisms in the brain. In this work, we developed Fn14 monoclonal antibody-decorated nanoparticles that can efficiently penetrate brain tissue. We show these Fn14-targeted brain tissue penetrating nanoparticles are able to (i) selectively bind to recombinant Fn14 but not brain ECM proteins, (ii) associate with and be internalized by Fn14-positive GBM cells, and (iii) diffuse within brain tissue in a manner similar to non-targeted brain penetrating nanoparticles. In addition, when administered intracranially, Fn14-targeted nanoparticles showed improved tumor cell co-localization in mice bearing human GBM xenografts compared to non-targeted nanoparticles. Minimizing non-specific binding of targeted nanoparticles in the brain may greatly improve the access of particulate delivery systems to remote brain tumor cells and other brain targets.

Emerging insights into barriers to effective brain tumor therapeutics

There is great promise that ongoing advances in the delivery of therapeutics to the central nervous system (CNS) combined with rapidly expanding knowledge of brain tumor patho-biology will provide new, more effective therapies. Brain tumors that form from brain cells, as opposed to those that come from other parts of the body, rarely metastasize outside of the CNS. Instead, the tumor cells invade deep into the brain itself, causing disruption in brain circuits, blood vessel and blood flow changes, and tissue swelling. Patients with the most common and deadly form, glioblastoma (GBM) rarely live more than 2 years even with the most aggressive treatments and often with devastating neurological consequences. Current treatments include maximal safe surgical removal or biopsy followed by radiation and chemotherapy to address the residual tumor mass and invading tumor cells. However, delivering effective and sustained treatments to these invading cells without damaging healthy brain tissue is a major challenge and focus of the emerging fields of nanomedicine and viral and cell-based therapies. New treatment strategies, particularly those directed against the invasive component of this devastating CNS disease, are sorely needed. In this review, we (1) discuss the history and evolution of treatments for GBM, (2) define and explore three critical barriers to improving therapeutic delivery to invasive brain tumors, specifically, the neuro-vascular unit as it relates to the blood brain barrier, the extra-cellular space in regard to the brain penetration barrier, and the tumor genetic heterogeneity and instability in association with the treatment efficacy barrier, and (3) identify promising new therapeutic delivery approaches that have the potential to address these barriers and create sustained, meaningful efficacy against GBM.

Non-invasive delivery of stealth, brain-penetrating nanoparticles across the blood-brain barrier using MRI-guided focused ultrasound

The blood-brain barrier (BBB) presents a significant obstacle for the treatment of many central nervous system (CNS) disorders, including invasive brain tumors, Alzheimer's, Parkinson's and stroke. Therapeutics must be capable of bypassing the BBB and also penetrate the brain parenchyma to achieve a desired effect within the brain. In this study, we test the unique combination of a non-invasive approach to BBB permeabilization with a therapeutically relevant polymeric nanoparticle platform capable of rapidly penetrating within the brain microenvironment. MR-guided focused ultrasound (FUS) with intravascular microbubbles (MBs) is able to locally and reversibly disrupt the BBB with submillimeter spatial accuracy. Densely poly(ethylene-co-glycol) (PEG) coated, brain-penetrating nanoparticles (BPNs) are long-circulating and diffuse 10-fold slower in normal rat brain tissue compared to diffusion in water. Following intravenous administration of model and biodegradable BPNs in normal healthy rats, we demonstrate safe, pressure-dependent delivery of 60nm BPNs to the brain parenchyma in regions where the BBB is disrupted by FUS and MBs. Delivery of BPNs with MR-guided FUS has the potential to improve efficacy of treatments for many CNS diseases, while reducing systemic side effects by providing sustained, well-dispersed drug delivery into select regions of the brain.

Surgical outcomes using a medial-to-lateral endonasal endoscopic approach to pituitary adenomas invading the cavernous sinus

OBJECT

This study details the extent of resection and complications associated with endonasal endoscopic surgery for pituitary tumors invading the cavernous sinus (CS) using a moderately aggressive approach to maximize extent of resection through the medial CS wall while minimizing the risk of cranial neuropathy and blood loss. Tumor in the medial CS was aggressively pursued while tumor in the lateral CS was debulked in preparation for radiosurgery.

METHODS

A prospective surgical database of consecutive endonasal pituitary surgeries with verified CS invasion on intraoperative visual inspection was reviewed. The extent of resection as a whole and within the CS was assessed by an independent neuroradiologist using pre- and postoperative Knosp-Steiner (KS) categorization and volumetrics of the respective MR images. The extent of resection and clinical outcomes were compared for medial (KS 1-2) and lateral (KS 3-4) lesions.

RESULTS

Thirty-six consecutive patients with pituitary adenomas involving the CS who had surgery via an endonasal endoscopic approach were identified. The extent of resection was 84.6% for KS 1-2 and 66.6% for KS 3-4 (p = 0.04). The rate of gross-total resection was 53.8% for KS 1-2 and 8.7% for KS 3-4 (p = 0.0006). Six patients (16.7%) had preoperative cranial neuropathies, and all 6 had subjective improvement after surgery. Surgical complications included 2 transient postoperative cranial neuropathies (5.6%), 1 postoperative CSF leak (2.8%), 1 reoperation for mucocele (2.8%), and 1 infection (2.8%).

CONCLUSIONS

The endoscopic endonasal "medial-to-lateral" approach permits safe debulking of tumors in the medial and lateral CS. Although rates of gross-total resection are moderate, particularly in the lateral CS, the risk of permanent cranial neuropathy is extremely low and there is a high chance of improvement of preexisting deficits. This approach can also facilitate targeting for postoperative radiosurgery.

Highly compacted pH-responsive DNA nanoparticles mediate transgene silencing in experimental glioma

Complex genetic mutations are common in brain cancer, making gene therapy an attractive approach to repair or modulate altered genes and cellular pathways. Non-viral gene vectors can offer DNA delivery without the risk of immunogenicity and/or insertional mutagenesis that are common with viral vectors. We developed pH-responsive DNA nanoparticles, CH₁₂K₁₈PEG_5k, by inserting a poly-L-histidine segment between PEG and poly-L-lysine to engineer a triblock copolymer. CH₁₂K₁₈PEG_5k DNA nanoparticles trafficked through clathrin-dependent endocytosis (CME) as the primary pathway in mouse glioblastoma (GBM) cells, and protected plasmid DNA from both DNase-mediated and acidic lysosomal degradation. CH₁₂K₁₈PEG_5k DNA nanoparticles effectively silenced a tumor-specific transgene (firefly luciferase) following direct injection into mouse intracranial GBM. Toxicity and histological analysis showed no evidence of acute or delayed inflammatory responses. These results demonstrate the utility of using this DNA nanoparticle-based technology for delivering genes to tumor cells as a possible therapeutic approach for patients with brain cancer.

Nanoparticle diffusion in respiratory mucus from humans without lung disease

A major role of respiratory mucus is to trap inhaled particles, including pathogens and environmental particulates, to limit body exposure. Despite the tremendous health implications, how particle size and surface chemistry affect mobility in respiratory mucus from humans without lung disease is not known. We prepared polymeric nanoparticles densely coated with low molecular weight polyethylene glycol (PEG) to minimize muco-adhesion, and compared their transport to that of uncoated particles in human respiratory mucus, which we collected from the endotracheal tubes of surgical patients with no respiratory comorbidities. We found that 100 and 200 nm diameter PEG-coated particles rapidly penetrated respiratory mucus, at rates exceeding their uncoated counterparts by approximately 15- and 35-fold, respectively. In contrast, PEG-coated particles ≥500 nm in diameter were sterically immobilized by the mucus mesh. Thus, even though respiratory mucus is a viscoelastic solid at the macroscopic level (as measured using a bulk rheometer), nanoparticles that are sufficiently small and muco-inert can penetrate the mucus as if it were primarily a viscous liquid. These findings help elucidate the barrier properties of respiratory mucus and provide design criteria for therapeutic nanoparticles capable of penetrating mucus to approach the underlying airway epithelium.

A dense poly(ethylene glycol) coating improves penetration of large polymeric nanoparticles within brain tissue

Prevailing opinion suggests that only substances up to 64 nm in diameter can move at appreciable rates through the brain extracellular space (ECS). This size range is large enough to allow diffusion of signaling molecules, nutrients, and metabolic waste products, but too small to allow efficient penetration of most particulate drug delivery systems and viruses carrying therapeutic genes, thereby limiting effectiveness of many potential therapies. We analyzed the movements of nanoparticles of various diameters and surface coatings within fresh human and rat brain tissue ex vivo and mouse brain in vivo. Nanoparticles as large as 114 nm in diameter diffused within the human and rat brain, but only if they were densely coated with poly(ethylene glycol) (PEG). Using these minimally adhesive PEG-coated particles, we estimated that human brain tissue ECS has some pores larger than 200 nm and that more than one-quarter of all pores are ≥ 100 nm. These findings were confirmed in vivo in mice, where 40- and 100-nm, but not 200-nm, nanoparticles spread rapidly within brain tissue, only if densely coated with PEG. Similar results were observed in rat brain tissue with paclitaxel-loaded biodegradable nanoparticles of similar size (85 nm) and surface properties. The ability to achieve brain penetration with larger nanoparticles is expected to allow more uniform, longer-lasting, and effective delivery of drugs within the brain, and may find use in the treatment of brain tumors, stroke, neuroinflammation, and other brain diseases where the blood-brain barrier is compromised or where local delivery strategies are feasible.

Hyperglycemia is independently associated with post-operative function loss in patients with primary eloquent glioblastoma

The poor prognosis for patients with glioblastoma (GB) heightens the importance of maintaining function throughout treatment. Hyperglycemia has been linked to poor neurological outcomes following stroke, traumatic brain and spinal cord injury. We hypothesized this may also be true following the resection of GB. We assessed associations with post-operative function with the goal of identifying modifiable factors in the peri-operative period with a particular focus on blood glucose levels. Independent associations with worse post-operative function included: patient age, pre-operative motor deficit, deep tumor location, post-operative motor deficit, and elevated mean peri-operative glucose. Interestingly, controlling for associated factors including dexamethasone dosing, patients with elevated peri-operative glucose levels were nearly twice as likely to have new post-operative neurological deficits. These results suggest, together with the broad literature supporting a role for hyperglycemia in neurological injury, that this may represent a modifiable factor in the peri-operative care of these patients.

Endoscopic endonasal approaches to the cavernous sinus

BACKGROUND

Surgical access to the cavernous sinus (CS) has proven a challenge for the skull base surgeon. Traditional approaches include the transcranial route, which broaches the lateral wall of the CS and has a high risk of cranial nerve weakness. A medial approach is more logical but the microscopic transsphenoidal approach has a restricted view. The endoscopic endonasal approach provides an alternative medial approach with improved visualization to that provided with the microscope. We describe our results using this approach for resection of CS tumors.

METHODS

A retrospective chart review was performed of all patients treated surgically at a tertiary care referral center between January 2004 and February 2011 with a purely endoscopic endonasal approach to the CS.

RESULTS

Out of 400 total endoscopic skull base cases, 41 (10.3%) involved the cavernous sinus. The most common approach was the transsphenoidal transsellar approach (31 patients, 75.6%). Other approaches included the tran-sethmoidal transsphenoidal parasellar (4 patients, 9.8%) and transmaxillary transpterygoidal (6 patients, 14.6%). The most common pathology was pituitary macroadenoma (24 patients, 58.5%). Gross total resection was achieved in 18 patients (43.9%). Cerebrospinal fluid (CSF) leak was not encountered in any patient postoperatively. Complications included 1 case of new postoperative VIth nerve palsy, 1 case of intraoperative hemorrhage, 2 cases of persistent diabetes insipidus, and 2 cases of sinusitis.

CONCLUSION

The endoscopic endonasal approach is a safe and effective option for tumor resection in the CS using a medial to lateral route for selected cases. Morbidity is low and a variety of reconstructive options are available.

Inaccuracy of the administrative database: comparative analysis of two databases for the diagnosis and treatment of intracranial aneurysms

OBJECTIVE

Administrative databases of hospital admissions are increasingly being used, mostly without validation, for epidemiological and clinical outcomes studies. Although it has been difficult to assess the true accuracy of administrative databases, we have identified an opportunity to directly compare the State of Maryland administrative database against a prospectively maintained departmental database at The Johns Hopkins Hospital.

METHODS

Data for patients with the diagnosis of an intracranial aneurysm treated at The Johns Hopkins Hospital over a 17-year period were compared in the State of Maryland administrative database and the neurosurgery departmental database. Discrepancies were clarified by review of the original medical records. The sensitivity, specificity, and positive predictive value of each database were calculated.

RESULTS

The administrative database missed 16% of all cases and was significantly inaccurate in 10 of 12 categories. It had particularly low values in the specificity regarding surgical treatment (67%), the sensitivity regarding endovascular treatment (48%), and the positive predictive value regarding endovascular treatment (30%). By contrast, the lowest score of the departmental database in any category was 97%.

CONCLUSION

We show that this representative administrative database is significantly flawed. Given the exponentially increasing number of research studies based on administrative databases, the pitfalls of research based solely on these need to be recognized. Strong criteria requiring accurate data validation are critical to justify the conclusions of these studies, regardless of their large numbers and complex statistics.

Persistent outpatient hyperglycemia is independently associated with survival, recurrence and malignant degeneration following surgery for hemispheric low grade gliomas

OBJECTIVE

Hyperglycemia has been shown to augment tumor growth in vitro. However, the effects of persistent hyperglycemia on survival, recurrence and malignant degeneration in patients undergoing surgery for low grade gliomas remain unknown.

METHODS

All patients who underwent a craniotomy for hemispheric low grade glioma (WHO grade II) from 1996 to 2006 at a single institution were retrospectively reviewed. Persistent hyperglycemia was defined as serum glucose >180 microg/dl occurring three or more times between 1 and 3 months post-operatively. The independent association of outpatient glucose levels and recorded clinical and treatment variables with overall survival, tumor recurrence and malignant degeneration was assessed via separate multivariate proportional-hazards regression analyses.

RESULTS

In this study, 182 patients (89 fibrillary astrocytomas, 82 oligodendrogliomas and 11 mixed gliomas) were available for analysis. Eighteen (10%) patients experienced persistent hyperglycemia. Patients experiencing persistent hyperglycemia were older (44 +/- 16 versus 34 +/- 15) and more frequently diabetic [3 (17%) versus 4 (2%)]. All other clinical and treatment variables were not significantly different between the two cohorts. After adjusting for inter-group differences including age and diabetes and variables associated with survival and recurrence, persistent hyperglycemia was independently associated with decreased survival (p=0.001), increased recurrence (p=0.0001) and increased malignant degeneration (p<0.0001). This remained true after excluding all patients with diabetes and those on continued steroid administration. Five-year overall survival, progression-free survival and malignancy-free survival for persistent hyperglycemia versus relatively euglycemic cohorts were 43% versus 84%, 16% versus 46% and 46% versus 77%, respectively.

DISCUSSION

These findings may provide useful insight for increasing survival, decreasing tumor recurrence and decreasing malignant degeneration in patients undergoing surgery for low grade gliomas.

CEREBROSPINAL FLUID DRAINAGE AND DYNAMICS IN THE DIAGNOSIS OF NORMAL PRESSURE HYDROCEPHALUS

INTRODUCTION

Because of the difficulty in distinguishing idiopathic normal pressure hydrocephalus (INPH) from other neurodegenerative conditions unrelated to cerebrospinal fluid (CSF) dynamics, response to CSF shunting remains highly variable. We examined the utility of CSF drainage and CSF pressure (Pcsf) dynamics in predicting response to CSF shunting for patients with INPH.

METHODS

Fifty-one consecutive INPH patients underwent continuous lumbar Pcsf monitoring for 48 hours followed by 72 hours of slow CSF drainage before ventriculoperitoneal shunting. Response to CSF drainage and B-wave characteristics were assessed via multivariate proportional-hazards regression analysis.

RESULTS

Improvement in 1, 2, or all 3 INPH symptoms was observed in 35 (69%), 28 (55%), and 11 (22%) patients, respectively, after CSF shunt implantation by 12 months after surgery. A positive response to CSF drainage was found to be an independent predictor of shunt responsiveness (relative risk, 0.30; 95% confidence interval, 0.09–0.98; P = 0.05). There was no difference in Pcsf wave characteristics between the shunt-responsive and -nonresponsive groups, regardless of whether 1-, 2-, or 3-symptom improvement was used to define response to CSF shunting.

CONCLUSION

In this study of 51 INPH patients who underwent Pcsf monitoring with waveform analysis and CSF drainage followed by shunt surgery, there was no correlation between specific Pcsf wave characteristics and objective symptomatic improvement after shunt placement. Pcsf monitoring with B-wave analysis contributes little to the diagnostic dilemma with INPH patients. Clinical response to continuous CSF drainage over a 72-hour period suggests a high likelihood of shunt responsiveness.

Predictors of ambulatory function after decompressive surgery for metastatic epidural spinal cord compression

OBJECTIVE

Metastatic epidural spinal cord compression (MESCC) is a relatively common and debilitating complication of metastatic disease that often results in neurological deficits. This study was designed to explore associations with maintaining and regaining ambulatory function after decompressive surgery for MESCC.

METHODS

Seventy-eight patients undergoing decompressive surgery for MESCC at an academic tertiary care institution between 1995 and 2005 were retrospectively reviewed. Fisher's exact analysis was used to compare preoperative ambulatory and nonambulatory patients. Multivariate Cox proportional hazards regression was used to identify associations with either maintaining or regaining the ability to walk.

RESULTS

Patients were followed for 7.1 +/- 1.6 (mean +/- standard deviation) months after surgery. Preoperative nonambulatory patients required more extensive surgery (increased operative spinal levels and number of laminectomies) and had more surgical site complications (wound dehiscences and cerebrospinal fluid leaks) compared with preoperative ambulatory patients. From the multivariate analysis, preoperative ability to walk (relative risk [RR], 2.320; 95% confidence interval [CI], 1.301-4.416; P < 0.01) independently increased the likelihood of ambulation at the last follow-up evaluation 2.3-fold. Pathological vertebral compression fracture at presentation (RR, 0.471; 95% CI, 0.235-0.864; P = 0.01) independently decreased the likelihood of ambulation at the time of the last follow-up evaluation 2.1-fold. For patients unable to walk at the time of surgery, preoperative radiation therapy (RR, 0.406; 95% CI, 0.124-0.927; P = 0.03) decreased the likelihood of regaining the ability to walk 2.5-fold. Symptoms present for less than 48 hours (RR, 2.925; 95% CI, 1.133-2.925; P = 0.02) and postoperative radiotherapy (RR, 2.595; 95% CI, 1.039-8.796; P = 0.04) independently increased the likelihood of regaining ambulatory ability 2.9- and 2.6-fold, respectively, by the time of last follow-up evaluation.

CONCLUSION

The identification of these associations with neurological outcome may help guide in the preservation or return of ambulation after surgery for patients with MESCC.

Factors associated with cervical instability requiring fusion after cervical laminectomy for intradural tumor resection

Object

The indications remain unclear for fusion at the time of cervical laminectomy for intradural tumor resection. To identify patients who may benefit from initial fusion, the authors assessed clinical, radiological/imaging, and operative factors associated with subsequent symptomatic cervical instability requiring fusion after cervical laminectomy for intradural tumor resection.

Methods

The authors reviewed 10 years of data obtained in patients who underwent cervical laminectomy without fusion for intradural tumor resection and who had normal spinal stability and alignment preoperatively. The association of pre- and intraoperative variables with the subsequent need for fusion for progressive symptomatic cervical instability was assessed using logistic regression analysis, and percentages were compared using Fisher exact tests when appropriate.

Results

Thirty-two patients (mean age 41 ± 17 years) underwent cervical laminectomy without fusion for resection of an intradural tumor (18 intramedullary and 14 extramedullary). Each increasing number of laminectomies performed was associated with a 3.1-fold increase in the likelihood of subsequent vertebral instability (odds ratio 3.114, 95% confidence interval 1.207–8.034, p = 0.02). At a mean follow-up interval of 25.2 months, 33% (4 of 12) of the patients who had undergone a ≥ 3-level laminectomy required subsequent fusion compared with 5% (1 of 20) who had undergone a ≤ 2-level laminectomy (p = 0.03). Four (36%) of 11 patients initially presenting with myelopathic motor disturbance required subsequent fusion compared with 1 (5%) of 21 presenting initially with myelopathic sensory or radicular symptoms (p = 0.02). Age, the presence of a syrinx, intramedullary tumor, C-2 laminectomy, C-7 laminectomy, and laminoplasty were not associated with subsequent symptomatic instability requiring fusion.

Conclusions

In the authors' experience with intradural cervical tumor resection, patients presenting with myelopathic motor symptoms or those undergoing a ≥ 3-level cervical laminectomy had an increased likelihood of developing subsequent symptomatic instability requiring fusion. A ≥ 3-level laminectomy with myelopathic motor symptoms may herald patients most likely to benefit from cervical fusion at the time of tumor resection.