M. Sean Grady

Hypoxia is important in the biology and aggression of human glial brain tumors.

We investigated whether increasing levels of tissue hypoxia, measured by the binding of EF5 [2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] or by Eppendorf needle electrodes, were associated with tumor aggressiveness in patients with previously untreated glial brain tumors. We hypothesized that more extensive and severe hypoxia would be present in tumor cells from patients bearing more clinically aggressive tumors. Hypoxia was measured with the 2-nitroimidazole imaging agent EF5 in 18 patients with supratentorial glial neoplasms. In 12 patients, needle electrode measurements were made intraoperatively. Time to recurrence was used as an indicator of tumor aggression and was analyzed as a function of EF5 binding, electrode values and recursive partitioning analysis (RPA) classification. On the basis of EF5 binding, WHO grade 2 tumors were characterized by modest cellular hypoxia (pO2s ≈ 10%) and grade 3 tumors by modest-to-moderate hypoxia (pO2s ≈ 10%- 2.5%). Severe hypoxia (≈0.1% oxygen) was present in 5 of 12 grade 4 tumors. A correlation between more rapid tumor recurrence and hypoxia was demonstrated with EF5 binding, but this relationship was not predicted by Eppendorf measurements.

Neuronal and glial cell number in the hippocampus after experimental traumatic brain injury: analysis by stereological estimation.

Fluid percussion (FP) brain injury causes spatial memory dysfunction in rats regardless of injury location (midline vs. lateral). Standard histological analysis of the injured brains shows hippocampal neuronal loss after lateral, but not midline FP injury. We have used the optical volume fractionator (OVF) stereological procedure to quantify neuronal loss and glial proliferation within specific subregions of the hippocampus after midline or lateral FP injury. The OVF method is a design-based cell counting procedure, which combines cellular numerical density estimates (from the optical disector) with volume estimates (generated by point counting and the fractionator stereology method) to produce an estimate of the absolute cell number. Fifteen adult male Sprague-Dawley rats were randomly divided into 3 groups (n = 5/group): midline injury, lateral injury and naive. A single fluid percussion pulse was delivered to anesthetized rats in the injured groups. At 14 days post-injury, strict morphological criteria enabled the estimation of neurons, astrocytes, oligodendrocytes, and microglia in defined hippocampal subregions. The results confirm that hippocampal neurons are selectively vulnerable to brain injury, particularly observed as a significant loss in the hilus following both types of injury and in area CA3 after lateral injury. In contrast, the number of astrocytes and oligodendrocytes remains unaffected by brain injury, regardless of subregion. However, the significant increase in microglia number (bilaterally after midline and ipsilateral following lateral injury) suggests that underlying cellular processes continue weeks following injury. The implications of the observed cell population changes are discussed in relation to the reported cognitive deficits associated with both lateral and midline FP brain injury.

Structural and functional damage sustained by mitochondria after traumatic brain injury in the rat: Evidence for differentially sensitive populations in the cortex and hippocampus

The cellular and molecular pathways initiated by traumatic brain injury (TBI) may compromise the function and structural integrity of mitochondria, thereby contributing to cerebral metabolic dysfunction and cell death. The extent to which TBI affects regional mitochondrial populations with respect to structure, function, and swelling was assessed 3 hours and 24 hours after lateral fluid—percussion brain injury in the rat. Significantly less mitochondrial protein was isolated from the injured compared with uninjured parietotemporal cortex, whereas comparable yields were obtained from the hippocampus. After injury, cortical and hippocampal tissue ATP concentrations declined significantly to 60% and 40% of control, respectively, in the absence of respiratory deficits in isolated mitochondria. Mitochondria with ultrastructural morphologic damage comprised a significantly greater percent of the population isolated from injured than uninjured brain. As determined by photon correlation spectroscopy, the mean mitochondrial radius decreased significantly in injured cortical populations (361 ± 40 nm at 24 hours) and increased significantly in injured hippocampal populations (442 ± 36 at 3 hours) compared with uninjured populations (Ctx: 418 ± 44; Hipp: 393 ± 24). Calcium-induced deenergized swelling rates of isolated mitochondrial populations were significantly slower in injured compared with uninjured samples, suggesting that injury alters the kinetics of mitochondrial permeability transition (MPT) pore activation. Cyclosporin A (CsA)-insensitive swelling was reduced in the cortex, and CsA-sensitive and CsA-insensitive swelling both were reduced in the hippocampus, demonstrating that regulated MPT pores remain in mitochondria isolated from injured brain. A proposed mitochondrial population model synthesizes these data and suggests that cortical mitochondria may be depleted after TBI, with a physically smaller, MPT-regulated population remaining. Hippocampal mitochondria may sustain damage associated with ballooned membranes and reduced MPT pore calcium sensitivity. The heterogeneous mitochondrial response to TBI may underlie posttraumatic metabolic dysfunction and contribute to the pathophysiology of TBI.

Deep brain stimulation in the treatment of obesity

Obesity is a growing global health problem frequently intractable to current treatment options. Recent evidence suggests that deep brain stimulation (DBS) may be effective and safe in the management of various, refractory neuropsychiatric disorders, including obesity. The authors review the literature implicating various neural regions in the pathophysiology of obesity, as well as the evidence supporting these regions as targets for DBS, in order to explore the therapeutic promise of DBS in obesity. The lateral hypothalamus and ventromedial hypothalamus are the appetite and satiety centers in the brain, respectively. Substantial data support targeting these regions with DBS for the purpose of appetite suppression and weight loss. However, reward sensation associated with highly caloric food has been implicated in overconsumption as well as obesity, and may in part explain the failure rates of conservative management and bariatric surgery. Thus, regions of the brains reward circuitry, such as the nucleus accumbens, are promising alternatives for DBS in obesity control. The authors conclude that deep brain stimulation should be strongly considered as a promising therapeutic option for patients suffering from refractory obesity.

A panel of neuron-enriched proteins as markers for traumatic brain injury in humans.

Surrogate markers have enormous potential for contributing to the diagnosis, prognosis, and therapeutic evaluation of acute brain damage, but extensive prior study of individual candidates has not yielded a biomarker in widespread clinical practice. We hypothesize that a panel of neuron-enriched proteins measurable in cerebrospinal fluid (CSF) and blood should vastly improve clinical evaluation and therapeutic management of acute brain injuries. Previously, we developed such a panel based initially on the study of protein release from degenerating cultured neurons, and subsequently on rodent models of traumatic brain injury (TBI) and ischemia, consisting of 14-3-3beta, 14-3-3zeta, three distinct phosphoforms of neurofilament H, ubiquitin hydrolase L1, neuron-specific enolase, alpha-spectrin, and three calpain- and caspase-derived fragments of alpha-spectrin. In the present study, this panel of 11 proteins was evaluated as CSF and serum biomarkers for severe TBI in humans. By quantitative Western blotting and sandwich immunoassays, the CSF protein levels were near or below the limit of detection in pre-surgical and most normal pressure hydrocephalus (NPH) controls, but following TBI nine of the 11 were routinely elevated in CSF. Whereas different markers peaked coordinately, the time to peak varied across TBI cases from 24-96 h post-injury. In serum, TBI increased all four members of the marker panel for which sandwich immunoassays are currently available: a calpain-derived NH(2)-terminal alpha-spectrin fragment and the three neurofilament H phosphoforms. Our results identify neuron-enriched proteins that may serve as a panel of CSF and blood surrogate markers for the minimally invasive detection, management, mechanistic, and therapeutic evaluation of human TBI.

Transcriptome in vivo analysis (TIVA) of spatially defined single cells in live tissue

Transcriptome profiling of single cells resident in their natural microenvironment depends upon RNA capture methods that are both noninvasive and spatially precise. We engineered a transcriptome in vivo analysis (TIVA) tag, which upon photoactivation enables mRNA capture from single cells in live tissue. Using the TIVA tag in combination with RNA sequencing (RNA-seq), we analyzed transcriptome variance among single neurons in culture and in mouse and human tissue in vivo. Our data showed that the tissue microenvironment shapes the transcriptomic landscape of individual cells. The TIVA methodology is, to our knowledge, the first noninvasive approach for capturing mRNA from live single cells in their natural microenvironment.

Impact of the Accreditation Council for Graduate Medical Education work-hour regulations on neurosurgical resident education and productivity.

OBJECT Recently, the Institute of Medicine examined resident duty hours and their impact on patient safety. Experts have suggested that reducing resident work hours to 56 hours per week would further decrease medical errors. Although some reports have indicated that cutbacks in resident duty hours reduce errors and make resident life safer, few authors have specifically analyzed the effect of the Accreditation Council for Graduate Medical Education (ACGME) duty-hour limits on neurosurgical resident education and the perceived quality of training. The authors have evaluated multiple objective surrogate markers of resident performance and quality of training to determine the impact of the 80-hour workweek. METHODS The United States Medical Licensing Examination (USMLE) Step 1 data on neurosurgical applicants entering ACGME-accredited programs between 1998 and 2007 (before and after the implementation of the work-hour rules) were obtained from the Society of Neurological Surgeons. The American Board of Neurological Surgery (ABNS) written examination scores for this group of residents were also acquired. Resident registration for and presentations at the American Association of Neurological Surgeons (AANS) annual meetings between 2002 and 2007 were examined as a measure of resident academic productivity. As a case example, the authors analyzed the distribution of resident training hours in the University of Virginia (UVA) neurosurgical training program before and after the institution of the 80-hour workweek. Finally, program directors and chief residents in ACGME-accredited programs were surveyed regarding the effects of the 80-hour workweek on patient care, resident training, surgical experience, patient safety, and patient access to quality care. Respondents were also queried about their perceptions of a 56-hour workweek. RESULTS Despite stable mean USMLE Step 1 scores for matched applicants to neurosurgery programs between 2000 and 2008, ABNS written examination scores for residents taking the exam for self-assessment decreased from 310 in 2002 to 259 in 2006 (16% decrease, p < 0.05). The mean scores for applicants completing the written examination for credit also did not change significantly during this period. Although there was an increase in the number of resident registrations to the AANS meetings, the number of abstracts presented by residents decreased from 345 in 2002 to 318 in 2007 (7% decrease, p < 0.05). An analysis of the UVA experience suggested that the 80-hour workweek leads to a notable increase in on-call duty hours with a profound decrease in the number of hours spent in conference and the operating room. Survey responses were obtained from 110 program directors (78% response rate) and 122 chief residents (76% response rate). Most chief residents and program directors believed the 80-hour workweek compromised resident training (96%) and decreased resident surgical experience (98%). Respondents also believed that the 80-hour workweek threatened patient safety (96% of program directors and 78% of chief residents) and access to quality care (82% of program directors and 87% of chief residents). When asked about the effects of a 56-hour workweek, all program directors and 98% of the chief residents indicated that resident training and surgical education would be further compromised. Most respondents (95% of program directors and 84% of chief residents) also believed that additional work-hour restrictions would jeopardize patient care. CONCLUSIONS Neurological surgery continues to attract top-quality resident applicants. Test scores and levels of participation in national conferences, however, indicate that the 80-hour workweek may adversely affect resident training. Subjectively, neurosurgical program directors and chief residents believe that the 80-hour workweek makes neurosurgical training and the care of patients more difficult. Based on experience with the 80-hour workweek, educators think that a 56-hour workweek would further compromise neurosurgical training and patient care in the US.

Spontaneous Cerebrospinal Fluid Leaks: A Variant of Benign Intracranial Hypertension

Objectives: Previous reports indicate that elevated intracranial pressure (ICP) may cause spontaneous cerebrospinal fluid (CSF) leaks. In this study we examined the clinical diagnosis of benign intracranial hypertension (BIH) in this population using the modified Dandy criteria. Methods: We performed a retrospective review of clinical data and measurements of ICPs after surgical repair. Results: Sixteen patients with spontaneous CSF leaks were surgically treated from 1996 to 2002. In 11 patients with CSF pressure measurements, strict adherence to the modified Dandy criteria definitively confirmed a diagnosis of BIH in 8 patients (72%) and a likely diagnosis in the 3 remaining patients. The mean ICP was 31.1 cm H2O (range, 17.3 to 52 cm H2O), and 81% of the patients were obese middle-aged women. Clinically, all patients had signs and/or symptoms of elevated ICP, such as headache (91%), pulsatile tinnitus (45%), hypertension (45%), balance problems (27%), and visual complaints (18%). Surgical repair was 100% successful in leak cessation over a mean follow-up of 14.1 months. Conclusions: Most patients with spontaneous CSF leaks fulfill the modified Dandy criteria; thus, this disorder appears to be a variant of BIH. Further investigation is needed to determine the exact cause of elevated CSF pressures in this group and whether medical or surgical treatments to correct the intracranial hypertension are warranted.

Association Between In Vivo Fluorine 18–Labeled Flutemetamol Amyloid Positron Emission Tomography Imaging and In Vivo Cerebral Cortical Histopathology

OBJECTIVE To determine the correspondence of in vivo quantitative estimates of brain uptake of fluorine 18-labeled flutemetamol with immunohistochemical estimates of amyloid levels in patients who underwent previous biopsy. DESIGN Cross-sectional study of ¹⁸F-flutemetamol positron emission tomography (PET) findings in patients with prior cortical biopsy specimen stained for the presence or absence of amyloid plaques. SETTING University hospital. Patients Seven patients who previously had a prior right frontal cortical biopsy at the site of ventriculoperitoneal placement for presumed normal pressure hydrocephalus were recruited. Inclusion criteria included an adequate biopsy specimen for detection and quantification of β-amyloid pathology and age older than 50 years. Intervention All patients underwent an ¹⁸F-flutemetamol PET scan. MAIN OUTCOME MEASURES Quantitative measures of ¹⁸F-flutemetamol uptake (standardized uptake value ratio, a ratio of mean target cortex activity divided by that in a cerebellar reference region) were made at a location contralateral to the biopsy site and compared with estimates of amyloid load based on immunohistochemical and histological staining. RESULTS There was complete agreement between visual reads of ¹⁸F-flutemetamol PET scans (3 blinded readers with majority rule) and histology. A regression model, including time from biopsy as a covariate, demonstrated a significant relationship (P = .01) between ¹⁸F-flutemetamol uptake and percentage of area of amyloid measured by a monoclonal antibody raised against amyloid (NAB228). Similar results were found with the amyloid-specific monoclonal antibody 4G8 and Thioflavin S. CONCLUSION To our knowledge, these data are the first to demonstrate the concordance of ¹⁸F-flutemetamol PET imaging with histopathology, supporting its sensitivity to detect amyloid and potential use in the study and detection of Alzheimer disease.

Comparison of endoscopic and microscopic removal of pituitary adenomas: single-surgeon experience and the learning curve.

OBJECT The endoscopic endonasal approach for resection of pituitary lesions is an effective surgical option for tumors of the sella turcica. In this study the authors compared outcomes after either purely endoscopic resection or traditional microscope-aided resection. They also attempted to determine the learning curve associated with a surgical team converting to endoscopic techniques. METHODS Retrospective data were collected on patients who were surgically treated for a pituitary lesion at the Hospital of the University of Pennsylvania between July 2003 and May 2008. Age, sex, race, presenting symptoms, length of hospital stay, surgical approach, duration of surgery, tumor pathological features, gross-total resection (GTR) of tumor, recurrence of the lesion, and intraoperative and postoperative complications were noted. All procedures were performed by the same senior neurosurgeon, who was initially unfamiliar with the endoscopic endonasal approach. RESULTS A total of 25 patients underwent microscopic resection and 25 patients underwent endoscopic resection performed by a single skull base team consisting of the same senior neurosurgeon and otorhinolaryngologist (M.S.G. and B.W.O.). In the microscopically treated cohort, there were 8 intra- or postoperative complications, 6 intraoperative CSF leaks, 17 (77%) of 22 patients had GTR on postoperative imaging, 5 patients underwent >or= 2 operations, and 10 (59%) of 17 patients reported total symptom resolution at follow-up. The endoscopically treated group had 7 intraor postoperative complications and 7 intraoperative CSF leaks. Of the patients who had pre- and postoperative imaging studies, 14 (66%) of 21 endoscopically treated patients had GTR; 4 patients had >or= 2 operations, and 10 (66%) of 15 patients reported complete symptom resolution at follow-up. The first 9 patients who were treated endoscopically had a mean surgical time of 3.42 hours and a mean hospital stay of 4.67 days. The next 8 patients treated had a mean surgical time of 3.11 hours and a mean hospital stay of 3.13 days. The final 8 patients treated endoscopically had a mean surgical time of 2.22 hours and a mean hospital stay of 3.88 days. The difference in length of operation between the first 9 and the last 8 patients treated endoscopically was significantly different. There was a trend toward decreased CSF leaks and other complications from the first 2 groups compared with the third group. CONCLUSIONS In this subset of patients, the use of endoscopic endonasal resection results in a similar complication and symptom resolution rate compared with traditional techniques. The authors postulate that the learning curve for endoscopic resection can be </= 17 procedures.