- Brain Tumors
- Surgical epilepsy
- Arnold-Chiari Malformation
- Minimally invasive craniosynostosis
- Moya-moya disease
- Pediatric Neurological Surgery
Division Chief, Pediatric Neurosurgery (2014 - Present)
Boards, Advisory Committees, Professional Organizations
Section Editor, Neurosurgery (2014 - Present)
Education Chair, American Society of Pediatric Neurosurgery (2013 - Present)
Committee on Trauma, American College of Surgeons (2012 - Present)
Member at Large, Executive Commitee, Section of Pediatric Neurosurgery (2014 - Present)
Executive Committee, Congress of Neurological Surgeons (2014 - Present)
Board Certification: Pediatric Neurological Surgery, American Board of Pediatric Neurological Surgery (2008)
Fellowship:University of Washington (2002) WA
Residency:University of Washington (2001) WA
Internship:University of Washington (1995) WA
Board Certification: Neurological Surgery, American Board of Neurological Surgery (2005)
Medical Education:Stanford University School of Medicine (1994) CA
Bachelor of Sciences, Duke University, Neurosciences (1989)
Community and International Work
Stanford Neurosurgery in Uganda, Mulago Hospital
Opportunities for Student Involvement
Current Research and Scholarly Interests
Dr. Grant directs a Blood-brain Barrier Translational Laboratory focusing on enhancing drug delivery to brain tumors in children.
- Narratives in Neurosurgery
NSUR 200 (Spr)
- Independent Studies (5)
- Prior Year Courses
Postdoctoral Faculty Sponsor
Johana Carolina Vega Leonel
- R-SCAN: Imaging for Pediatric Simple Febrile Seizures. Journal of the American College of Radiology 2017
Perioperative outcomes for pediatric neurosurgical procedures: analysis of the National Surgical Quality Improvement Program-Pediatrics
JOURNAL OF NEUROSURGERY-PEDIATRICS
2017; 19 (3): 361-371
OBJECTIVE Existing studies have shown a high overall rate of adverse events (AEs) following pediatric neurosurgical procedures. However, little is known regarding the morbidity of specific procedures or the association with risk factors to help guide quality improvement (QI) initiatives. The goal of this study was to describe the 30-day mortality and AE rates for pediatric neurosurgical procedures by using the American College of Surgeons (ACS) National Surgical Quality Improvement Program-Pediatrics (NSQIP-Peds) database platform. METHODS Data on 9996 pediatric neurosurgical patients were acquired from the 2012-2014 NSQIP-Peds participant user file. Neurosurgical cases were analyzed by the NSQIP-Peds targeted procedure categories, including craniotomy/craniectomy, defect repair, laminectomy, shunts, and implants. The primary outcome measure was 30-day mortality, with secondary outcomes including individual AEs, composite morbidity (all AEs excluding mortality and unplanned reoperation), surgical-site infection, and unplanned reoperation. Univariate analysis was performed between individual AEs and patient characteristics using Fischer's exact test. Associations between individual AEs and continuous variables (duration from admission to operation, work relative value unit, and operation time) were examined using the Student t-test. Patient characteristics and continuous variables associated with any AE by univariate analysis were used to develop category-specific multivariable models through backward stepwise logistic regression. RESULTS The authors analyzed 3383 craniotomy/craniectomy, 242 defect repair, 1811 laminectomy, and 4560 shunt and implant cases and found a composite overall morbidity of 30.2%, 38.8%, 10.2%, and 10.7%, respectively. Unplanned reoperation rates were highest for defect repair (29.8%). The mortality rate ranged from 0.1% to 1.2%. Preoperative ventilator dependence was a significant predictor of any AE for all procedure groups, whereas admission from outside hospital transfer was a significant predictor of any AE for all procedure groups except craniotomy/craniectomy. CONCLUSIONS This analysis of NSQIP-Peds, a large risk-adjusted national data set, confirms low perioperative mortality but high morbidity for pediatric neurosurgical procedures. These data provide a baseline understanding of current expected clinical outcomes for pediatric neurosurgical procedures, identify the need for collecting neurosurgery-specific risk factors and complications, and should support targeted QI programs and clinical management interventions to improve care of children.
View details for DOI 10.3171/2016.10.PEDS16414
View details for Web of Science ID 000394925800014
View details for PubMedID 28059679
Magnetic Resonance-Guided Laser-Induced Thermal Therapy for Recurrent Brain Metastases in the Motor Strip After Stereotactic Radiosurgery.
2016; 8 (12)
The authors report a challenging case of a brain metastasis located in the motor cortex, which was not responsive to radiosurgery. Use of a novel technique, magnetic resonance-guided laser-induced thermotherapy (MRgLITT), resulted in the complete obliteration of the lesion without adverse effects or evidence of tumor recurrence at follow-up. This case illustrates that MRgLITT may provide a viable alternative for patients with brain metastases refractory to radiosurgery or in deep locations, where both stereotactic radiosurgery (SRS) and surgical resection may be ineffective.
View details for DOI 10.7759/cureus.919
View details for PubMedID 28083463
View details for PubMedCentralID PMC5218883
Diagnosis and treatment of pediatric frontotemporal pits: report of 2 cases
JOURNAL OF NEUROSURGERY-PEDIATRICS
2016; 18 (4): 471-474
In contrast to more common nasal and cervical lesions, the frontotemporal pit is a rarely encountered lesion that is often associated with a dermoid and may track intracranially. Due to delays in diagnosis, the propensity to spread intracranially, and the risk of infection, awareness of these lesions and appropriate diagnosis and management are important. The authors present 2 cases of frontotemporal pits from a single institution. Epidemiology, presentation, and management recommendations are discussed.
View details for DOI 10.3171/2016.5.PEDS1687
View details for Web of Science ID 000383938500015
View details for PubMedID 27391653
Integrin-Targeting Knottin Peptide-Drug Conjugates Are Potent Inhibitors of Tumor Cell Proliferation.
Angewandte Chemie (International ed. in English)
2016; 55 (34): 9894-9897
Antibody-drug conjugates (ADCs) offer increased efficacy and reduced toxicity compared to systemic chemotherapy. Less attention has been paid to peptide-drug delivery, which has the potential for increased tumor penetration and facile synthesis. We report a knottin peptide-drug conjugate (KDC) and demonstrate that it can selectively deliver gemcitabine to malignant cells expressing tumor-associated integrins. This KDC binds to tumor cells with low-nanomolar affinity, is internalized by an integrin-mediated process, releases its payload intracellularly, and is a highly potent inhibitor of brain, breast, ovarian, and pancreatic cancer cell lines. Notably, these features enable this KDC to bypass a gemcitabine-resistance mechanism found in pancreatic cancer cells. This work expands the therapeutic relevance of knottin peptides to include targeted drug delivery, and further motivates efforts to expand the drug-conjugate toolkit to include non-antibody protein scaffolds.
View details for DOI 10.1002/anie.201603488
View details for PubMedID 27304709
Management of moyamoya syndrome in patients with Noonan syndrome
JOURNAL OF CLINICAL NEUROSCIENCE
2016; 28: 107-111
A few isolated reports have described an association between Noonan syndrome and cerebrovascular abnormalities, including moyamoya syndrome. These reports have been limited to pediatric patients presenting with recurrent transient ischemic attacks (TIA) or headaches. Management has primarily been pharmacologic, with only one prior report of surgical revascularization to our knowledge. We report four cases of Noonan syndrome patients presenting with headaches and/or sensorimotor strokes in childhood that caused unilateral sensorimotor impairment. Cerebral angiography and MRI revealed bilateral moyamoya syndrome. All patients underwent successful bilateral extracranial-to-intracranial revascularization. The first patient was a 10-year-old girl who presented following a hemorrhagic stroke and recovered well after indirect bypass. The second patient was an adult with a history of childhood stroke whose symptoms progressed in adulthood. She underwent a direct bypass and improved, but continued to experience TIA at her 4 year follow-up. The third patient was a 7-year-old girl with headaches and a new onset TIA who failed pharmacological therapy and subsequently underwent bilateral indirect bypass. The fourth patient was a 24-year-old woman with worsening headaches and an occluded left middle cerebral artery from unilateral moyamoya syndrome. A left sided direct bypass was completed given delayed MRI perfusion with poor augmentation. To our knowledge these are the first reported surgical cases of combined Noonan and moyamoya syndrome. These cases highlight the need to recognize moyamoya syndrome in patients with Noonan syndrome. Early surgical revascularization should be pursued in order to prevent symptom progression.
View details for DOI 10.1016/j.jocn.2015.11.017
View details for Web of Science ID 000376714500021
View details for PubMedID 26778511
Epilepsy: A Disruptive Force in History.
2016; 90: 685-690
Since it was first described in a Mesopotamian text in 2000 bc, countless individuals have offered their perspectives on epilepsy's cause, treatment, and even deeper spiritual significance. However, despite the attention the disease has received through the millennia, it has only been within the past half-century that truly effective treatment options have been available. As a result, for the vast majority of recorded history, individuals with epilepsy have not only had to deal with the uncertainty of their next epileptic seizure but also the concomitant stigma and ostracization. Interestingly, these individuals have included several prominent historical figures, including Julius Caesar, Vladimir Lenin, and Fyodor Dostoyevsky. The fact that epilepsy has appeared in the lives of influential historical people means that the disease has played some role in affecting the progress of human civilization. Epilepsy has cut short the lives of key political leaders, affected the output of talented cultural icons, and, especially within the past half century, influenced the collective understanding of neuroscience and the human nervous system. In this article, the authors review how epilepsy throughout history has manifested itself in the lives of prominent figures and how the disease has helped shape the course of humanity's political, cultural, and scientific evolution.
View details for DOI 10.1016/j.wneu.2015.11.060
View details for PubMedID 26709155
Radiation-induced brain injury: low-hanging fruit for neuroregeneration
2016; 40 (5)
Brain radiation is a fundamental tool in neurooncology to improve local tumor control, but it leads to profound and progressive impairments in cognitive function. Increased attention to quality of life in neurooncology has accelerated efforts to understand and ameliorate radiation-induced cognitive sequelae. Such progress has coincided with a new understanding of the role of CNS progenitor cell populations in normal cognition and in their potential utility for the treatment of neurological diseases. The irradiated brain exhibits a host of biochemical and cellular derangements, including loss of endogenous neurogenesis, demyelination, and ablation of endogenous oligodendrocyte progenitor cells. These changes, in combination with a state of chronic neuroinflammation, underlie impairments in memory, attention, executive function, and acquisition of motor and language skills. Animal models of radiation-induced brain injury have demonstrated a robust capacity of both neural stem cells and oligodendrocyte progenitor cells to restore cognitive function after brain irradiation, likely through a combination of cell replacement and trophic effects. Oligodendrocyte progenitor cells exhibit a remarkable capacity to migrate, integrate, and functionally remyelinate damaged white matter tracts in a variety of preclinical models. The authors here critically address the opportunities and challenges in translating regenerative cell therapies from rodents to humans. Although valiant attempts to translate neuroprotective therapies in recent decades have almost uniformly failed, the authors make the case that harnessing human radiation-induced brain injury as a scientific tool represents a unique opportunity to both successfully translate a neuroregenerative therapy and to acquire tools to facilitate future restorative therapies for human traumatic and degenerative diseases of the central nervous system.
View details for DOI 10.3171/2016.2.FOCUS161
View details for Web of Science ID 000375119300002
View details for PubMedID 27132524
Randomized Placebo-Controlled Trial of Methylphenidate or Galantamine for Persistent Emotional and Cognitive Symptoms Associated with PTSD and/or Traumatic Brain Injury
2016; 41 (5): 1191-1198
We report findings from a 12-week randomized double-blinded placebo-controlled trial of methylphenidate or galantamine to treat emotional and cognitive complaints in individuals (n=32) with a history of PTSD, TBI, or both conditions. In this small pilot study, methylphenidate treatment was associated with clinically meaningful and statistically significant improvement compared with placebo on the primary outcome, a measure of cognitive complaints (Ruff Neurobehavioral Inventory-Postmorbid Cognitive Scale), as well as on the secondary outcomes reflecting post-concussive (Rivermead Post Concussive Symptom Questionnaire) and post-traumatic stress symptoms (Posttraumatic Stress Disorder Checklist). Treatment was well tolerated. These results suggest the need for a larger RCT to replicate and confirm these findings. Design considerations for such a trial should include the need for multiple sites to facilitate adequate recruitment and extension of the treatment and follow-up periods.
View details for DOI 10.1038/npp.2015.282
View details for Web of Science ID 000371801200002
View details for PubMedID 26361060
Sports-related brain injuries: connecting pathology to diagnosis
2016; 40 (4)
Brain injuries are becoming increasingly common in athletes and represent an important diagnostic challenge. Early detection and management of brain injuries in sports are of utmost importance in preventing chronic neurological and psychiatric decline. These types of injuries incurred during sports are referred to as mild traumatic brain injuries, which represent a heterogeneous spectrum of disease. The most dramatic manifestation of chronic mild traumatic brain injuries is termed chronic traumatic encephalopathy, which is associated with profound neuropsychiatric deficits. Because chronic traumatic encephalopathy can only be diagnosed by postmortem examination, new diagnostic methodologies are needed for early detection and amelioration of disease burden. This review examines the pathology driving changes in athletes participating in high-impact sports and how this understanding can lead to innovations in neuroimaging and biomarker discovery.
View details for DOI 10.3171/2016.1.FOCUS15607
View details for Web of Science ID 000373476500004
View details for PubMedID 27032917
- New tools for studying microglia in the mouse and human CNS PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2016; 113 (12): E1738-E1746
New tools for studying microglia in the mouse and human CNS.
Proceedings of the National Academy of Sciences of the United States of America
2016; 113 (12): E1738-46
The specific function of microglia, the tissue resident macrophages of the brain and spinal cord, has been difficult to ascertain because of a lack of tools to distinguish microglia from other immune cells, thereby limiting specific immunostaining, purification, and manipulation. Because of their unique developmental origins and predicted functions, the distinction of microglia from other myeloid cells is critically important for understanding brain development and disease; better tools would greatly facilitate studies of microglia function in the developing, adult, and injured CNS. Here, we identify transmembrane protein 119 (Tmem119), a cell-surface protein of unknown function, as a highly expressed microglia-specific marker in both mouse and human. We developed monoclonal antibodies to its intracellular and extracellular domains that enable the immunostaining of microglia in histological sections in healthy and diseased brains, as well as isolation of pure nonactivated microglia by FACS. Using our antibodies, we provide, to our knowledge, the first RNAseq profiles of highly pure mouse microglia during development and after an immune challenge. We used these to demonstrate that mouse microglia mature by the second postnatal week and to predict novel microglial functions. Together, we anticipate these resources will be valuable for the future study and understanding of microglia in health and disease.
View details for DOI 10.1073/pnas.1525528113
View details for PubMedID 26884166
View details for PubMedCentralID PMC4812770
Junior Seau: An Illustrative Case of Chronic Traumatic Encephalopathy and Update on Chronic Sports-Related Head Injury
Few neurologic diseases have captured the nation's attention more completely than chronic traumatic encephalopathy (CTE), which has been discovered in the autopsies of professional athletes, most notably professional football players. The tragic case of Junior Seau, a Hall of Fame, National Football League linebacker, has been the most high-profile confirmed case of CTE. Here we describe Seau's case, which concludes an autopsy conducted at the National Institutes of Health that confirmed the diagnosis.Since 1990, Junior Seau had a highly distinguished 20-year career playing for the National Football League as a linebacker, from which he sustained multiple concussions. He committed suicide on May 2, 2012, at age 43, after which an autopsy confirmed a diagnosis of CTE. His clinical history was significant for a series of behavioral disturbances. Seau's history and neuropathologic findings were used to better understand the pathophysiology, diagnosis, and possible risk factors for CTE.This high-profile case reflects an increasing awareness of CTE as a long-term consequence of multiple traumatic brain injuries. The previously unforeseen neurologic risks of American football have begun to cast doubt on the safety of the sport.
View details for DOI 10.1016/j.wneu.2015.10.032
View details for Web of Science ID 000369625300104
View details for PubMedID 26493714
Purification and Characterization of Progenitor and Mature Human Astrocytes Reveals Transcriptional and Functional Differences with Mouse
2016; 89 (1): 37-53
The functional and molecular similarities and distinctions between human and murine astrocytes are poorly understood. Here, we report the development of an immunopanning method to acutely purify astrocytes from fetal, juvenile, and adult human brains and to maintain these cells in serum-free cultures. We found that human astrocytes have abilities similar to those of murine astrocytes in promoting neuronal survival, inducing functional synapse formation, and engulfing synaptosomes. In contrast to existing observations in mice, we found that mature human astrocytes respond robustly to glutamate. Next, we performed RNA sequencing of healthy human astrocytes along with astrocytes from epileptic and tumor foci and compared these to human neurons, oligodendrocytes, microglia, and endothelial cells (available at http://www.brainrnaseq.org). With these profiles, we identified novel human-specific astrocyte genes and discovered a transcriptome-wide transformation between astrocyte precursor cells and mature post-mitotic astrocytes. These data represent some of the first cell-type-specific molecular profiles of the healthy and diseased human brain.
View details for DOI 10.1016/j.neuron.2015.11.013
View details for Web of Science ID 000373564300006
View details for PubMedID 26687838
View details for PubMedCentralID PMC4707064
Pediatric Central Nervous System Tumors in Nepal: Retrospective Analysis and Literature Review of Low- and Middle-Income Countries
2015; 84 (6): 1832-1837
Central nervous system (CNS) tumors are the most common cause of cancer-related death in children. Little is known about the demographics and treatment of pediatric brain tumors in low- and middle-income countries (LMICs).We performed a retrospective chart review of all pediatric patients who presented to the neurosurgical service at Tribhuvan University Teaching Hospital in Kathmandu, Nepal from 2009-2014 and collected information on patients <18 years old who received a diagnosis of a CNS tumor. We analyzed age, gender, clinical presentation, extent of surgical resection, histopathology, and length of hospital stay. We also conducted a literature review using specific terminology to capture studies of pediatric neuro-oncologic epidemiology conducted in LMICs. Study location, length of study, sample size, study type, and occurrence of 4 common pediatric brain tumors were extracted.We identified 39 cases of pediatric CNS tumors, with 62.5% observed in male children. We found that male children (median = 13 years) presented later than female children (median = 8 years). The most frequently observed pediatric brain tumor type was ependymoma (17.5%), followed by astrocytoma (15%) and medulloblastoma (15%). Surgical resection was performed for 80% of cases, and gross total resection reported in 62.9% of all surgeries. More than half (54.1%) of patients had symptoms for more than 28 days before seeking treatment. Symptomatic hydrocephalus was noted in 57.1% of children who presented with CNS tumors. The literature review yielded studies from 18 countries. Study length ranged from 2-20 years, and sample sizes varied from 35-1948. Overall, we found more pronounced variation in the relative frequencies of the most common pediatric brain tumors, compared with high-income countries.We present the first operative series of childhood CNS tumors in Nepal. Children often had delayed diagnosis and treatment of a tumor, despite symptoms. More comprehensive data are required to develop improved treatment and management algorithms in the context of a given country's demographics and medical capabilities for childhood CNS tumors.
View details for DOI 10.1016/j.wneu.2015.07.074
View details for Web of Science ID 000366286300060
View details for PubMedID 26283488
- Repeated autologous umbilical cord blood infusions are feasible and had no acute safety issues in young babies with congenital hydrocephalus PEDIATRIC RESEARCH 2015; 78 (6): 712-716
Ex vivo generation of dendritic cells from cryopreserved, post-induction chemotherapy, mobilized leukapheresis from pediatric patients with medulloblastoma.
Journal of neuro-oncology
2015; 125 (1): 65-74
Generation of patient-derived, autologous dendritic cells (DCs) is a critical component of cancer immunotherapy with ex vivo-generated, tumor antigen-loaded DCs. An important factor in the ability to generate DCs is the potential impact of prior therapies on DC phenotype and function. We investigated the ability to generate DCs using cells harvested from pediatric patients with medulloblastoma for potential evaluation of DC-RNA based vaccination approach in this patient population. Cells harvested from medulloblastoma patient leukapheresis following induction chemotherapy and granulocyte colony stimulating factor mobilization were cryopreserved prior to use in DC generation. DCs were generated from the adherent CD14+ monocytes using standard procedures and analyzed for cell recovery, phenotype and function. To summarize, 4 out of 5 patients (80 %) had sufficient monocyte recovery to permit DC generation, and we were able to generate DCs from 3 out of these 4 patient samples (75 %). Overall, we successfully generated DCs that met phenotypic requisites for DC-based cancer therapy from 3 out of 5 (60 %) patient samples and met both phenotypic and functional requisites from 2 out of 5 (40 %) patient samples. This study highlights the potential to generate functional DCs for further clinical treatments from refractory patients that have been heavily pretreated with myelosuppressive chemotherapy. Here we demonstrate the utility of evaluating the effect of the currently employed standard-of-care therapies on the ex vivo generation of DCs for DC-based clinical studies in cancer patients.
View details for DOI 10.1007/s11060-015-1890-2
View details for PubMedID 26311248
View details for PubMedCentralID PMC4592836
Evolution of cranioplasty techniques in neurosurgery: historical review, pediatric considerations, and current trends.
Journal of neurosurgery
2015; 123 (4): 1098-1107
Cranial bone repair is one of the oldest neurosurgical practices. Reconstructing the natural contours of the skull has challenged the ingenuity of surgeons from antiquity to the present day. Given the continuous improvement of neurosurgical and emergency care over the past century, more patients survive such head injuries, thus necessitating more than ever before a simple, safe, and durable means of correcting skull defects. In response, numerous techniques and materials have been devised as the art of cranioplasty has progressed. Although the goals of cranioplasty remain the same, the evolution of techniques and diversity of materials used serves as testimony to the complexity of this task. This paper highlights the evolution of these materials and techniques, with a particular focus on the implications for managing pediatric calvarial repair and emerging trends within the field.
View details for DOI 10.3171/2014.11.JNS14622
View details for PubMedID 25699411
Gorlin syndrome and desmoplastic medulloblastoma: Report of 3 cases with unfavorable clinical course and novel mutations
PEDIATRIC BLOOD & CANCER
2015; 62 (10): 1855-1858
We present three cases of genetically confirmed Gorlin syndrome with desmoplastic medulloblastoma (DMB) in whom tumor recurred despite standard therapy. One patient was found to have a novel germline missense PTCH1 mutation. Molecular analysis of recurrent tumor using fluorescent in situ hybridization (FISH) revealed PTEN and/ or PTCH1 loss in 2 patients. Whole exome sequencing (WES) of tumor in one patient revealed loss of heterozygosity of PTCH1 and a mutation of GNAS gene in its non-coding 3' -untranslated region (UTR) with corresponding decreased protein expression. While one patient died despite high-dose chemotherapy (HDC) plus stem cell rescue (ASCR) and palliative radiotherapy, two patients are currently alive for 18+ and 120+ months respectively following retrieval therapy that did not include irradiation. Infants with DMB and GS should be treated aggressively with chemotherapy at diagnosis to prevent relapse but radiotherapy should be avoided. The use of molecular prognostic markers for DMB should be routinely used to identify the subset of tumors that might have an aggressive course. Pediatr Blood Cancer 2015;62:1855-1858. © 2015 Wiley Periodicals, Inc.
View details for DOI 10.1002/pbc.25560
View details for Web of Science ID 000360228000027
View details for PubMedID 25940061
Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury
ANNALS OF BIOMEDICAL ENGINEERING
2015; 43 (8): 1918-1934
This preliminary study investigated whether direct measurement of head rotation improves prediction of mild traumatic brain injury (mTBI). Although many studies have implicated rotation as a primary cause of mTBI, regulatory safety standards use 3 degree-of-freedom (3DOF) translation-only kinematic criteria to predict injury. Direct 6DOF measurements of human head rotation (3DOF) and translation (3DOF) have not been previously available to examine whether additional DOFs improve injury prediction. We measured head impacts in American football, boxing, and mixed martial arts using 6DOF instrumented mouthguards, and predicted clinician-diagnosed injury using 12 existing kinematic criteria and 6 existing brain finite element (FE) criteria. Among 513 measured impacts were the first two 6DOF measurements of clinically diagnosed mTBI. For this dataset, 6DOF criteria were the most predictive of injury, more than 3DOF translation-only and 3DOF rotation-only criteria. Peak principal strain in the corpus callosum, a 6DOF FE criteria, was the strongest predictor, followed by two criteria that included rotation measurements, peak rotational acceleration magnitude and Head Impact Power (HIP). These results suggest head rotation measurements may improve injury prediction. However, more 6DOF data is needed to confirm this evaluation of existing injury criteria, and to develop new criteria that considers directional sensitivity to injury.
View details for DOI 10.1007/s10439-014-1212-4
View details for Web of Science ID 000358249800018
View details for PubMedCentralID PMC4478276
- Preface to Clinical Neurosurgery Volume 62, Proceedings of the Congress of Neurological Surgeons 2014 Annual Meeting. Neurosurgery 2015; 62: N1-?
Therapeutic strategies to improve drug delivery across the blood-brain barrier.
2015; 38 (3): E9-?
Resection of brain tumors is followed by chemotherapy and radiation to ablate remaining malignant cell populations. Targeting these populations stands to reduce tumor recurrence and offer the promise of more complete therapy. Thus, improving access to the tumor, while leaving normal brain tissue unscathed, is a critical pursuit. A central challenge in this endeavor lies in the limited delivery of therapeutics to the tumor itself. The blood-brain barrier (BBB) is responsible for much of this difficulty but also provides an essential separation from systemic circulation. Due to the BBB's physical and chemical constraints, many current therapies, from cytotoxic drugs to antibody-based proteins, cannot gain access to the tumor. This review describes the characteristics of the BBB and associated changes wrought by the presence of a tumor. Current strategies for enhancing the delivery of therapies across the BBB to the tumor will be discussed, with a distinction made between strategies that seek to disrupt the BBB and those that aim to circumvent it.
View details for DOI 10.3171/2014.12.FOCUS14758
View details for PubMedID 25727231
View details for PubMedCentralID PMC4493051
- Therapeutic strategies to improve drug delivery across the blood-brain barrier. Neurosurgical focus 2015; 38 (3): E9-?
Sertraline-induced potentiation of the CYP3A4-dependent neurotoxicity of carbamazepine: An in vitro study
2015; 56 (3): 439-449
Drug toxicity is a hurdle to drug development and to clinical translation of basic research. Antiepileptic drugs such as carbamazepine (CBZ) and selective serotonin reuptake inhibitors such as sertraline (SRT) are commonly co-prescribed to patients with epilepsy and comorbid depression. Because SRT may interfere with cytochrome P450 (CYP) enzyme activity and CYPs have been implicated in the conversion of CBZ to reactive cytotoxic metabolites, we investigated in vitro models to determine whether SRT affects the neurotoxic potential of CBZ and the mechanisms involved.Human fetal brain-derived dopaminergic neurons, human brain microvascular endothelial cells (HBMECs), and embryonic kidney (HEK) cells were used to evaluate cytotoxicity of CBZ and SRT individually and in combination. Nitrite and glutathione (GSH) levels were measured with drug exposure. To validate the role of CYP3A4 in causing neurotoxicity, drug metabolism was compared to cell death in HEK CYP3A4 overexpressed and cells pretreated with the CYP3A4 inhibitor ketoconazole.In all cellular systems tested, exposure to CBZ (127 μm) or SRT (5 μm) alone caused negligible cytotoxicity. By contrast CBZ, tested at a much lower concentration (17 μm) in combination with SRT (5 μm), produced prominent cytotoxicity within 15 min exposure. In neurons and HBMECs, cytotoxicity was associated with increased nitrite levels, suggesting involvement of free radicals as a pathogenetic mechanism. Pretreatment of HBMECs with reduced GSH or with the GSH precursor N-acetyl-l-cysteine prevented cytotoxic response. In HEK cells, the cytotoxic response to the CBZ + SRT combination correlated with the rate of CBZ biotransformation and production of 2-hydroxy CBZ, further suggesting a causative role of reactive metabolites. In the same system, cytotoxicity was potentiated by overexpression of CYP3A4, and prevented by CYP3A4 inhibitor.These results demonstrate an unexpected neurotoxic interaction between CBZ and SRT, apparently related to increased CYP3A4-mediated production of reactive CBZ metabolites. The potential clinical implications of these findings are discussed.
View details for DOI 10.1111/epi.12923
View details for Web of Science ID 000351240300016
View details for PubMedID 25656284
- Joint eQTL assessment of whole blood and dura mater tissue from individuals with Chiari type I malformation BMC GENOMICS 2015; 16
- Is there a role for decompressive craniectomy in children after stroke? World neurosurgery 2015; 83 (1): 44-45
- Preface to clinical neurosurgery volume 61, proceedings of the congress of neurological surgeons 2013 annual meeting. Neurosurgery 2014; 61: N1-?
- Identification of Chiari Type I Malformation subtypes using whole genome expression profiles and cranial base morphometrics BMC MEDICAL GENOMICS 2014; 7
Genome Sequencing of SHH Medulloblastoma Predicts Genotype-Related Response to Smoothened Inhibition
2014; 25 (3): 393-405
Smoothened (SMO) inhibitors recently entered clinical trials for sonic-hedgehog-driven medulloblastoma (SHH-MB). Clinical response is highly variable. To understand the mechanism(s) of primary resistance and identify pathways cooperating with aberrant SHH signaling, we sequenced and profiled a large cohort of SHH-MBs (n = 133). SHH pathway mutations involved PTCH1 (across all age groups), SUFU (infants, including germline), and SMO (adults). Children >3 years old harbored an excess of downstream MYCN and GLI2 amplifications and frequent TP53 mutations, often in the germline, all of which were rare in infants and adults. Functional assays in different SHH-MB xenograft models demonstrated that SHH-MBs harboring a PTCH1 mutation were responsive to SMO inhibition, whereas tumors harboring an SUFU mutation or MYCN amplification were primarily resistant.
View details for DOI 10.1016/j.ccr.2014.02.004
View details for Web of Science ID 000333233400015
View details for PubMedID 24651015
Reorganization and stability for motor and language areas using cortical stimulation: case example and review of the literature.
2013; 3 (4): 1597-1614
The cerebral organization of language in epilepsy patients has been studied with invasive procedures such as Wada testing and electrical cortical stimulation mapping and more recently with noninvasive neuroimaging techniques, such as functional MRI. In the setting of a chronic seizure disorder, clinical variables have been shown to contribute to cerebral language reorganization underscoring the need for language lateralization and localization procedures. We present a 14-year-old pediatric patient with a refractory epilepsy disorder who underwent two neurosurgical resections of a left frontal epileptic focus separated by a year. He was mapped extraoperatively through a subdural grid using cortical stimulation to preserve motor and language functions. The clinical history and extensive workup prior to surgery is discussed as well as the opportunity to compare the cortical maps for language, motor, and sensory function before each resection. Reorganization in cortical tongue sensory areas was seen concomitant with a new zone of ictal and interictal activity in the previous tongue sensory area. Detailed neuropsychological data is presented before and after any surgical intervention to hypothesize about the extent of reorganization between epochs. We conclude that intrahemispheric cortical plasticity does occur following frontal lobe resective surgery in a teenager with medically refractory seizures.
View details for DOI 10.3390/brainsci3041597
View details for PubMedID 24961623