Daniel L. Silbergeld

Spatial spectral analysis of human electrocorticograms including the alpha and gamma bands.

Spatial spectral analysis is essential for deriving spatial patterns from simultaneous recordings of electrocorticograms (ECoG), in order to determine the optimal interval between electrodes in arrays, and to design spatial filters, particularly for extraction of information about the dynamics of human gamma activity. ECoG were recorded from up to 64 electrodes 0.5 mm apart in a linear array 3.2 cm long, which was placed on the exposed superior temporal gyrus or motor cortex of volunteers undergoing diagnostic surgery. Visual displays of multiple traces revealed broad spectrum oscillations in episodic bursts having a common aperiodic wave form with recurring patterns of spatial amplitude modulation (AM patterns) on selected portions of the array. The one-dimensional spatial spectrum of the human ECoG was calculated at successive time samples and averaged over periods of up to 20 s. Log power decreased monotonically with increasing log spatial frequency in cycles/mm (c/mm) to the noise level approximately 2 log units below maximal power at minimal frequency (0.039+/-0.002 c/mm). The inflection point at 0.40+/-0.05 c/mm specified an optimal value for a low pass spatial filter to remove noise, and an optimal interelectrode spacing of 1.25 mm to avoid undersampling and aliasing. An 8 x 8 array with that spacing would be 10 x 10 mm.

High-intensity focused ultrasound selectively disrupts the blood-brain barrier in vivo

High-intensity focused ultrasound (HIFU) has been shown to generate lesions that destroy brain tissue while disrupting the blood-brain barrier (BBB) in the periphery of the lesion. BBB opening, however, has not been shown without damage, and the mechanisms by which HIFU induces BBB disruption remain unknown. We show that HIFU is capable of reversible, nondestructive, BBB disruption in a targeted region-of-interest (ROI) (29 of 55 applications; 26 of 55 applications showed no effect); this opening reverses after 72 h. Light microscopy demonstrates that HIFU either entirely preserves brain architecture while opening the BBB (18 of 29 applications), or generates tissue damage in a small volume within the region of BBB opening (11 of 29 applications). Electron microscopy supports these observations and suggests that HIFU disrupts the BBB by opening capillary endothelial cell tight junctions, an isolated ultrastructural effect that is different from the mechanisms through which other (untargeted) modalities, such as hyperosmotic solutions, hyperthermia and percussive injury disrupt the BBB.

Preserved Function in Brain Invaded by Tumor

OBJECTIVE Intrinsic brain tumors can arise within regions of the cortex that are essential to language, motor, and somatosensory functions. Although it is commonly thought that such tumors can be safely resected, as long as the resection is limited to grossly abnormal cortex, functional mapping of the cerebral cortex during tumor resection does not support this contention. METHODS We report our experience with 14 patients (9 men, 5 women; median age, 43 yr) with intrinsic brain tumors of varying degrees of malignancy (four glioblastomas multiforme, four anaplastic astrocytomas, two anaplastic oligodendrogliomas, one anaplastic mixed glioma, three gangliogliomas). Cortical mapping was performed either intraoperatively (n = 11) or extraoperatively via intracranial electrodes (n = 3). RESULTS Tumors were found to grossly invade functioning cortices (frontal lobe language cortex, four tumors; temporal lobe language cortex, five tumors; motor cortex, four tumors; somatosensory cortex, one tumor). The gross invasion of functional cortex by tumor limited safe resection in all patients. Three patients experienced transient postoperative deficits caused by the proximity of the resection to functional cortex. One patient suffered a delayed postoperative hemorrhage, with resultant persistent motor aphasia. CONCLUSION Intrinsic brain tumors grow by infiltration of normal brain. Consequently, brain that appears to be abnormal may remain functional, thus precluding safe tumor resection.

Regional Hypoxia in Glioblastoma Multiforme Quantified with [18F]Fluoromisonidazole Positron Emission Tomography before Radiotherapy: Correlation with Time to Progression and Survival

Purpose: Hypoxia is associated with resistance to radiotherapy and chemotherapy and activates transcription factors that support cell survival and migration. We measured the volume of hypoxic tumor and the maximum level of hypoxia in glioblastoma multiforme before radiotherapy with [18F]fluoromisonidazole positron emission tomography to assess their impact on time to progression (TTP) or survival. Experimental Design: Twenty-two patients were studied before biopsy or between resection and starting radiotherapy. Each had a 20-minute emission scan 2 hours after i.v. injection of 7 mCi of [18F]fluoromisonidazole. Venous blood samples taken during imaging were used to create tissue to blood concentration (T/B) ratios. The volume of tumor with T/B values above 1.2 defined the hypoxic volume (HV). Maximum T/B values (T/Bmax) were determined from the pixel with the highest uptake. Results: Kaplan-Meier plots showed shorter TTP and survival in patients whose tumors contained HVs or tumor T/Bmax ratios greater than the median (P ≤ 0.001). In univariate analyses, greater HV or tumor T/Bmax were associated with shorter TTP or survival (P < 0.002). Multivariate analyses for survival and TTP against the covariates HV (or T/Bmax), magnetic resonance imaging (MRI) T1Gd volume, age, and Karnovsky performance score reached significance only for HV (or T/Bmax; P < 0.03). Conclusions: The volume and intensity of hypoxia in glioblastoma multiforme before radiotherapy are strongly associated with poorer TTP and survival. This type of imaging could be integrated into new treatment strategies to target hypoxia more aggressively in glioblastoma multiforme and could be applied to assess the treatment outcomes.

The cause of death in patients with glioblastoma is multifactorial: clinical factors and autopsy findings in 117 cases of supratentorial glioblastoma in adults.

To delineate the causes of death (COD) in adults with supratentorial glioblastoma multiforme (GM) we reviewed 117 consecutive cases examined at autopsy over a nineteen year period at the University of Washington. Twenty cases (17%) had expired unexpectedly without ante mortem diagnosis, 5 patients (4%) had been diagnosed as having lower grade astrocytomas prior to death. Other than the 20 patients without ante mortem diagnosis, all patients had a surgical procedure for treatment and/or diagnosis (biopsy 10%, craniotomy 90%). Postsurgical therapy varied, but there was no significant difference in median length of survival among the different treatment groups. Factors considered as potential COD were: herniation (axial, transtentorial, subfalcine, tonsillar), surgical complications (death within thirty days of surgery secondary to cerebral hemorrhage and/or edema), severe systemic illness, brainstem invasion by tumor, and neutron-induced cerebral injury (cerebral and brainstem gliosis were evident in these cases). A potential COD could be identified in 93% of patients. Patients with no ante mortem diagnosis were likely to have herniated (p = 0.01), whereas patients who underwent neutron irradiation were unlikely to have herniated (p = 0.001). No other variables were statistically significant predictors of herniation, including multifocal tumors (20 patients), and brainstem invasion by tumor (18 patients). No patients died as a result of treatment except those who underwent neutron radiotherapy and those who died postoperatively. Although significant mass effect, as evidenced by herniation, was apparent in 61% of patients, most of these patients had an additional identifiable COD. We conclude that the COD in patients with GM varies and is often multifactorial.

Convection-enhanced delivery of cintredekin besudotox (interleukin-13- PE38QQR) followed by radiation therapy with and without temozolomide in newly diagnosed malignant gliomas

OBJECTIVECintredekin besudotox (CB), a recombinant cytotoxin consisting of interleukin-13 and truncated Pseudomonas exotoxin, binds selectively to interleukin-13Rα2 receptors overexpressed by malignant gliomas. This study assessed the safety of CB administered by convection-enhanced delivery followed by standard external beam radiation therapy (EBRT) with or without temozolomide (Temodar; Schering-Plough, Kenilworth, NJ) in patients with newly diagnosed malignant gliomas. METHODSAfter gross total resection of the tumor, two to four intraparenchymal catheters were stereotactically placed and CB (0.25 or 0.5 μg/mL) was infused for 96 hours. This was followed, 10 to 14 days later, by EBRT (5940–6100 cGy, 5 d/wk for 6–7 wk) with or without temozolomide (75 mg/m2/d, 7 d/wk during EBRT). Safety was assessed during an 11-week observation period after catheter placement RESULTSTwenty-two patients (12 men, 10 women; median age, 55 yr; 21 with glioblastoma multiforme and one with an anaplastic mixed oligoastrocytoma) were enrolled. None of the patients experienced dose-limiting toxicities in the first two cohorts (0.25 μg/mL CB + EBRT [n = 3] and 0.25 μg/mL CB + EBRT + temozolomide [n = 3]). One patient experienced a dose-limiting toxicity (Grade 4 seizure) in the third cohort (0.5 μg/mL CB + EBRT [n = 6]). Six patients in the final cohort (0.5 μg/mL CB + EBRT + temozolomide [n = 10]) completed treatment, and one patient experienced a dose-limiting toxicity (Grade 3 aphasia and confusion). Four patients were not considered evaluable for a dose decision and were replaced. CB related adverse events occurring in more than one patient were fatigue, gait disturbance, nystagmus, and confusion. No Grade 3 to 4 hematological toxicities were observed. CONCLUSIONCB (0.5 μg/mL) administered via convection-enhanced delivery before standard radiochemotherapy seems to be well tolerated in adults with newly diagnosed malignant gliomas. Further clinical study assessment is warranted.

Use of propofol (Diprivan) for awake craniotomies: Technical note

We describe the use of propofol (Diprivan) to provide patient comfort during the initial stages of awake craniotomies.

The role of postoperative irradiation in the treatment of oligodendroglioma.

PURPOSE Controversy regarding the role of adjuvant radiation therapy for the treatment of oligodendroglioma continues to exist. To better define the utility of postoperative irradiation for this tumor, the experience at the University of Washington was retrospectively examined. METHODS AND MATERIALS The histologic samples of 63 patients given the diagnosis of oligodendroglioma were reviewed by a panel of neuropathologists and 41 were classified as pure oligodendroglioma. The two treatment groups included 14 patients treated with surgery only and 27 who received surgery and postoperative radiation and were analyzed using univariate and multivariate analysis with respect to prognostic factors, freedom from relapse, and survival. RESULTS Univariate statistical analysis of 14 clinical variables showed that a poorer prognosis was associated in patients with high cell density (p = .008), necrosis (p = .017), hemiparesis (p = .026), and papilledema (p = .091), while patients presenting with seizures had a better prognosis (p = .0096). Multivariate analysis showed necrosis (p = .001) and hemiparesis (p = .02) to be associated with decreased survival. Multivariate and univariate analysis of the treatment groups found them to be homogenous with respect to prognostic factors. Survival times were significantly longer in the group treated with postoperative irradiation (median survival time 84 vs. 47 months, p = .032). The 5 and 10 year survival rates were 83% and 46%, respectively, for the irradiated patients compared with 51% and 36% for those treated with surgery alone. Freedom from tumor recurrence times were also longer in irradiated patients (median relapse free time 79 vs. 42 months, p = .01). CONCLUSION Based on the results of this study, we recommend continuing the practice of treating oligodendroglioma with postresection irradiation until a prospective multicenter clinical trial is conducted to thoroughly evaluate the role of postoperative irradiation in the treatment of this tumor.

Extended Survival of Glioblastoma Patients After Chemoprotective HSC Gene Therapy

Gene therapy using P140K-modified hematopoietic progenitor cells is chemoprotective, enabling glioblastoma patients to withstand myelotoxic doses of chemotherapy. Arming Blood Stem Cells to Fight Cancer The toxic effects of chemotherapy (chemotoxicity) on blood and bone marrow cells of cancer patients can be a significant barrier to treating tumors. Delivery of a gene that can protect bone marrow stem and progenitor cells from chemotoxicity could overcome this barrier. In a new study by Adair et al., patients with chemotherapy-resistant brain tumors with very poor chances of survival were given a transplant with their own bone marrow hematopoietic stem cells after the cells had been modified with a gene that protects these cells from chemotherapy. After the bone marrow transplant, patients were then given dose-intensified chemotherapy. Adair et al. report that the patients were able to tolerate these chemotherapy doses better after transplant of the gene-modified bone marrow stem cells than did patients in previous studies who had received the same type of chemotherapy but without the gene-modified bone marrow stem cell transplant. The authors found that chemotherapy increased the number of gene-modified blood and bone marrow cells in these patients. These patients survived longer than predicted without any negative side effects from the transplanted cells or the treatment given. This strategy could be used for treating other types of cancer, or diseases treated with the same type of chemotherapy, to increase the efficacy of the drug regimen. This strategy could also be further developed as a clinical application in other diseases where defective bone marrow stem cells can be corrected by gene therapy but need to be increased to higher levels to produce a therapeutic benefit. Chemotherapy with alkylating agents for treating malignant disease results in myelosuppression that can significantly limit dose escalation and potential clinical efficacy. Gene therapy using mutant methylguanine methyltransferase (P140K) gene–modified hematopoietic stem and progenitor cells may circumvent this problem by abrogating the toxic effects of chemotherapy on hematopoietic cells. However, this approach has not been evaluated clinically. Here, we show efficient polyclonal engraftment of autologous P140K-modified hematopoietic stem and progenitor cells in three patients with glioblastoma. Increases in P140K-modified cells after transplant indicate selection of gene-modified hematopoietic repopulating cells. Longitudinal retroviral integration site (RIS) analysis identified more than 12,000 unique RISs in the three glioblastoma patients, with multiple clones present in the peripheral blood of each patient throughout multiple chemotherapy cycles. To assess safety, we monitored RIS distribution over the course of chemotherapy treatments. Two patients exhibited emergence of prominent clones harboring RISs associated with the intronic coding region of PRDM16 (PR domain–containing 16) or the 3′ untranslated region of HMGA2 (high-mobility group A2) genes with no adverse clinical outcomes. All three patients surpassed the median survival for glioblastoma patients with poor prognosis, with one patient alive and progression-free more than 2 years after diagnosis. Thus, transplanted P140K-expressing hematopoietic stem and progenitor cells are chemoprotective, potentially maximizing the drug dose that can be administered.

Mitogens as motogens

Numerous in vivo methodologies have documented the invasivebehavior of glioma cells through normal brain parenchyma.Glioma cell locomotion has also been assessed witha number of in vitro assays including theBoyden chamber and other chemotaxis assays, colloidal goldcell tracking, analysis of migration of cells tumorcells from spheroids, confrontation cultures of glioma cellswith aggregates of non-neoplastic tissue, time-lapse video microscopy,electron microscopic examination of the cytomorphologic correlates ofcell motility, the radial dish assay, and quantitativeenzyme immunoassay of proteins associated with invasion (e.g.laminin). Several of these techniques have been specificallymodified to assess the effects of cytokines onglioma cell motility in vitro. Cytokines studied utilizingthese methods include: epidermal growth factor (EGF), basicfibroblast growth factor (bFGF), the bb dimer ofplatelet-derived growth factor (PDGFbb), nerve growth factor (NGF),interleukin 2 (IL-2), transforming growth factors alpha andbeta 1 (TGFα and TGFstraat1), and tumor necrosisfactor alpha (TNFα). This review summarizes the investigationalmethods used to evaluate random and directional gliomacell motility and invasion in vivo and invitro. The roles of specific mitogens as motogens,as evaluated with these methods are then presented.