Honors & Awards

  • Stanford Gold Humanism Honor Society Inductee, Gold Foundation (2019)
  • Neuroscience Scholars Program Fellow, Society for Neuroscience (2018-2020)
  • Medical Student Summer Research Fellowship, Neurosurgery Research & Education Foundation (2018)
  • Stanford Society of Physician Scholars Grant, Stanford University School of Medicine (2018)
  • Founder’s Day Award, New York University (2014)
  • Collegiate Science and Technology Entry Program Research Initiative Award, New York University (2013, 2014)

Professional Affiliations and Activities

  • Member, Society for Neuroscience (2018 - Present)
  • Member, American Association of Neurological Surgeons (2016 - Present)
  • Member, Congress of Neurological Surgeons (2017 - Present)

Membership Organizations

  • Neurosurgery Interest Group, Co-President (2015-2016)
  • Pacific Free Clinic, Lab Manager (2016-2017)
  • AANS Student Chapter, Founder/President (2016-2018)

Education & Certifications

  • Bachelor of Science, New York University, Neural Science (2014)

Current Research and Scholarly Interests

I seek to determine the genetic and epigenetic mechanisms driving disease progression in metastatic tumors to the brain. My efforts have focused on the use single-cell and cell subtype-specific transcriptomics to identify and target immune cells within these metastatic tumors. At the Gephart Lab I am engaged in collaborative projects, utilizing cutting edge techniques including next generation sequencing and exploring the genetic profiles of cell-free and single-cell RNA from human brain metastases and CSF samples. I hope to identify targetable genes crucial in the tumorigenesis and survival of metastatic tumors to the brain.

Lab Affiliations

All Publications

  • Patient Satisfaction and Press Ganey Scores for Spine Versus Nonspine Neurosurgery Clinics. Clinical spine surgery Chen, Y., Johnson, E., Montalvo, C., Stratford, S., Veeravagu, A., Tharin, S., Desai, A., Ratliff, J., Shuer, L., Park, J. 2019


    STUDY DESIGN: Retrospective survey review.OBJECTIVE: We seek to evaluate satisfaction scores in patients seen in neurosurgical spine versus neurosurgical nonspine clinics.SUMMARY OF BACKGROUND DATA: The Press Ganey survey is a well-established metric for measuring hospital performance and patient satisfaction. These measures have important implications in setting hospital policy and guiding interventions to improve patient perceptions of care.METHODS: Retrospective Press Ganey survey review was performed to identify patient demographics and patient visit characteristics from January 1st, 2012 to October 10th, 2017 at Stanford Medical Center. A total of 40 questions from the Press Ganey survey were investigated and grouped in categories addressing physician and nursing care, personal concerns, admission, room, meal, operating room, treatment and discharge conditions, visitor accommodations and overall clinic assessment. Raw ordinal scores were converted to continuous scores of 100 for unpaired student t test analysis. We identified 578 neurosurgical spine clinic patients and 1048 neurosurgical nonspine clinic patients.RESULTS: Spine clinic patients reported lower satisfaction scores in aggregate (88.2 vs. 90.1; P=0.0014), physician (89.5 vs. 92.6; P=0.0002) and nurse care (91.3 vs. 93.4; P=0.0038), personal concerns (88.2 vs. 90.9; P=0.0009), room (81.0 vs. 83.1; P=0.0164), admission (90.8 vs. 92.6; P=0.0154) and visitor conditions (87.0 vs. 89.2; P=0.0148), and overall clinic assessment (92.9 vs. 95.5; P=0.005).CONCLUSIONS: This study is the first to evaluate the relationship between neurosurgical spine versus nonspine clinic with regards to patient satisfaction. The spine clinic cohort reported less satisfaction than the nonspine cohort in all significant questions on the Press Ganey survey. Our findings suggest that efforts should be made to further study and improve patient satisfaction in spine clinics.LEVEL OF EVIDENCE: Level III.

    View details for DOI 10.1097/BSD.0000000000000825

    View details for PubMedID 30969193

  • Rapid-sequence brain magnetic resonance imaging for Chiari I abnormality JOURNAL OF NEUROSURGERY-PEDIATRICS Pan, J., Quon, J. L., Johnson, E., Lanzman, B., Chukus, A., Ho, A. L., Edwards, M. B., Grant, G. A., Yeom, K. W. 2018; 22 (2): 158–64


    OBJECTIVE Fast magnetic resonance imaging (fsMRI) sequences are single-shot spin echo images with fast acquisition times that have replaced CT scans for many conditions. Introduced as a means of evaluating children with hydrocephalus and macrocephaly, these sequences reduce the need for anesthesia and can be more cost-effective, especially for children who require multiple surveillance scans. However, the role of fsMRI has yet to be investigated in evaluating the posterior fossa in patients with Chiari I abnormality (CM-I). The goal of this study was to examine the diagnostic performance of fsMRI in evaluating the cerebellar tonsils in comparison to conventional MRI. METHODS The authors performed a retrospective analysis of 18 pediatric patients with a confirmed diagnosis of CM-I based on gold-standard conventional brain MRI and 30 controls without CM-I who had presented with various neurosurgical conditions. The CM-I patients were included if fsMRI studies had been obtained within 1 year of conventional MRI with no surgical intervention between the studies. Two neuroradiologists reviewed the studies in a blinded fashion to determine the diagnostic performance of fsMRI in detecting CM-I. For the CM-I cohort, the fsMRI and T2-weighted MRI exams were randomized, and the blinded reviewers performed tonsillar measurements on both scans. RESULTS The mean age of the CM-I cohort was 7.39 years, and 50% of these subjects were male. The mean time interval between fsMRI and conventional T2-weighted MRI was 97.8 days. Forty-four percent of the subjects had undergone imaging after posterior fossa decompression. The sensitivity and specificity of fsMRI in detecting CM-I was 100% (95% CI 71.51%-100%) and 92.11% (95% CI 78.62%-98.34%), respectively. If only preoperative patients are considered, both sensitivity and specificity increase to 100%. The authors also performed a cost analysis and determined that fsMRI was significantly cost-effective compared to T2-weighted MRI or CT. CONCLUSIONS Despite known limitations, fsMRI may serve as a useful diagnostic and surveillance tool for CM-I. It is more cost-effective than full conventional brain MRI and decreases the need for sedation in young children.

    View details for PubMedID 29749883

  • Single-Cell RNA-Sequencing in Glioma CURRENT ONCOLOGY REPORTS Johnson, E., Dickerson, K. L., Connolly, I. D., Gephart, M. 2018; 20 (5): 42


    In this review, we seek to summarize the literature concerning the use of single-cell RNA-sequencing for CNS gliomas.Single-cell analysis has revealed complex tumor heterogeneity, subpopulations of proliferating stem-like cells and expanded our view of tumor microenvironment influence in the disease process. Although bulk RNA-sequencing has guided our initial understanding of glioma genetics, this method does not accurately define the heterogeneous subpopulations found within these tumors. Single-cell techniques have appealing applications in cancer research, as diverse cell types and the tumor microenvironment have important implications in therapy. High cost and difficult protocols prevent widespread use of single-cell RNA-sequencing; however, continued innovation will improve accessibility and expand our of knowledge gliomas.

    View details for PubMedID 29637300

  • National Trends for Reoperation in Older Patients with Glioblastoma. World neurosurgery Chen, Y., Sole, J., Ugiliweneza, B., Johnson, E., Burton, E., Woo, S. Y., Koutourousiou, M., Williams, B., Boakye, M., Skirboll, S. 2018


    BACKGROUND: Despite multimodal therapies extending patient survival, glioblastoma (GBM) recurrence is all but a certainty. To date, there are few single-center studies of reoperations. Our study aimed to assess GBM reoperation trends nationally in older patients, with emphasis on outcomes.METHODS: The linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database was searched to identify patients 66 years and older with GBM from 1997 to 2010. The primary outcome was survival after diagnosis. Kaplan-Meier curves and multivariate analysis with proportional hazard ratios were used.RESULTS: Three thousand nine hundred sixty-three patients with recurrent GBM who initially received a surgical resection were identified (mean age= 74.7 years). Four hundred ninety-six (12%) of the patients with recurrent GBM underwent at least one reoperation at an average of 7.2 months after the initial diagnosis. Reoperation increased survival in patients compared with those who did not have surgical resection (12 vs. 5 months; P < 0.0001; hazard ratio [HR]= 0.666). Within the reoperated cohort, gross total resection improved median survival over subtotal resection (HR= 0.779). Two or more reoperations upon GBM recurrence improved survival to 17 months (P=0.002). The overall complication rate was 21.7% in the initial resection-only group, versus 20.4% in the 1-reoperation group and 25.3% in the 2-reoperation group.CONCLUSIONS: Although definitive conclusions cannot be made given the lack of granularity, our national database study supports gross total resection as the initial treatment of choice, followed by reoperation at the time of recurrence, if tolerated, even in older patients.

    View details for PubMedID 29427817

  • A review of potential applications of MR-guided focused ultrasound for targeting brain tumor therapy NEUROSURGICAL FOCUS Lamsam, L., Johnson, E., Connolly, I. D., Wintermark, M., Gephart, M. 2018; 44 (2): E10


    Magnetic resonance-guided focused ultrasound (MRgFUS) has been used extensively to ablate brain tissue in movement disorders, such as essential tremor. At a lower energy, MRgFUS can disrupt the blood-brain barrier (BBB) to allow passage of drugs. This focal disruption of the BBB can target systemic medications to specific portions of the brain, such as for brain tumors. Current methods to bypass the BBB are invasive, as the BBB is relatively impermeable to systemically delivered antineoplastic agents. Multiple healthy and brain tumor animal models have suggested that MRgFUS disrupts the BBB and focally increases the concentration of systemically delivered antitumor chemotherapy, immunotherapy, and gene therapy. In animal tumor models, combining MRgFUS with systemic drug delivery increases median survival times and delays tumor progression. Liposomes, modified microbubbles, and magnetic nanoparticles, combined with MRgFUS, more effectively deliver chemotherapy to brain tumors. MRgFUS has great potential to enhance brain tumor drug delivery, while limiting treatment toxicity to the healthy brain.

    View details for PubMedID 29385922

  • Massive Intradural Chondroma Masquerading as Lower Body Parkinsonism. Cureus Connolly, I. D., Johnson, E., Lummus, S., Hayden Gephart, M. 2018; 10 (1): e2099


    Intracranial chondromas of the dural convexity are exceedingly rare with less than 30 reported in the literature to date. We report a massive intradural convexity chondroma in a patient initially thought to have a frontal gait neurodegenerative disorder. This large tumor required a complex, piecemeal surgical resection due to the dense, fibrous nature of the tumor and the proximity of crucial structures. The patient had complete resolution of her preoperative symptoms after surgical excision.

    View details for PubMedID 29581912

  • Preoperative depression, lumbar fusion, and opioid use: an assessment of postoperative prescription, quality, and economic outcomes. Neurosurgical focus O'Connell, C., Azad, T. D., Mittal, V., Vail, D., Johnson, E., Desai, A., Sun, E., Ratliff, J. K., Veeravagu, A. 2018; 44 (1): E5


    OBJECTIVE Preoperative depression has been linked to a variety of adverse outcomes following lumbar fusion, including increased pain, disability, and 30-day readmission rates. The goal of the present study was to determine whether preoperative depression is associated with increased narcotic use following lumbar fusion. Moreover, the authors examined the association between preoperative depression and a variety of secondary quality indicator and economic outcomes, including complications, 30-day readmissions, revision surgeries, likelihood of discharge home, and 1- and 2-year costs. METHODS A retrospective analysis was conducted using a national longitudinal administrative database (MarketScan) containing diagnostic and reimbursement data on patients with a variety of private insurance providers and Medicare for the period from 2007 to 2014. Multivariable logistic and negative binomial regressions were performed to assess the relationship between preoperative depression and the primary postoperative opioid use outcomes while controlling for demographic, comorbidity, and preoperative prescription drug-use variables. Logistic and log-linear regressions were also used to evaluate the association between depression and the secondary outcomes of complications, 30-day readmissions, revisions, likelihood of discharge home, and 1- and 2-year costs. RESULTS The authors identified 60,597 patients who had undergone lumbar fusion and met the study inclusion criteria, 4985 of whom also had a preoperative diagnosis of depression and 21,905 of whom had a diagnosis of spondylolisthesis at the time of surgery. A preoperative depression diagnosis was associated with increased cumulative opioid use (β = 0.25, p < 0.001), an increased risk of chronic use (OR 1.28, 95% CI 1.17-1.40), and a decreased probability of opioid cessation (OR 0.96, 95% CI 0.95-0.98) following lumbar fusion. In terms of secondary outcomes, preoperative depression was also associated with a slightly increased risk of complications (OR 1.14, 95% CI 1.03-1.25), revision fusions (OR 1.15, 95% CI 1.05-1.26), and 30-day readmissions (OR 1.19, 95% CI 1.04-1.36), although it was not significantly associated with the probability of discharge to home (OR 0.92, 95% CI 0.84-1.01). Preoperative depression also resulted in increased costs at 1 (β = 0.06, p < 0.001) and 2 (β = 0.09, p < 0.001) years postoperatively. CONCLUSIONS Although these findings must be interpreted in the context of the limitations inherent to retrospective studies utilizing administrative data, they provide additional evidence for the link between a preoperative diagnosis of depression and adverse outcomes, particularly increased opioid use, following lumbar fusion.

    View details for DOI 10.3171/2017.10.FOCUS17563

    View details for PubMedID 29290135

  • Minimally invasive lumbar pedicle screw fixation using cortical bone trajectory - Screw accuracy, complications, and learning curve in 100 screw placements. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia Dayani, F., Chen, Y. R., Johnson, E., Deb, S., Wu, Y., Pham, L., Singh, H. 2018


    Cortical bone trajectory (CBT) is a novel pedicle insertion technique with comparable or superior mechanical properties and reduced invasiveness compared to traditional methods. We describe the screw accuracy, complications, and learning curve associated with CBT use. A prospective cohort study was performed involving 22 patients who underwent lumbar fusion with CBT screw placement. A total of 100 cortical screws were placed. Post-operative CT scans were reviewed to assess the adequacy of screw placement and calculate the incidence of vertebral body and pedicle breaches from cortical screw placement. Technique-related complications were examined. The entire surgical cohort was divided into two groups: early experience (first 11 patients) and late experience (last 11 patients), to study the effect of learning curve on CBT screw placement. Medial pedicle breach was observed in 6/100 cases and lateral vertebral body breach was observed in 1/100 cases. The incidence of durotomy related to the technique was 4.5% (N = 1/22). Post-surgical wound infection was seen in 9.1% of patients (N = 2/22). 66.7% (N = 4/6) of medial pedicle breaches, 100% (N = 1/1) of lateral breaches, 100% (N = 1/1) of CBT technique-related CSF leaks, and 100% (N = 2/2) of wound infections occurred in the early experience phase of our study (p = 0.0945). A shift in surgical technique and greater efficiency over time decreased the incidence of overall complications in the late cohort. The difference, however, did not reach statistical significance. A lateralized starting point for the cortical screw on the pars interarticularis and use of smaller diameter screws resulted in fewer medial pedicle out-fractures and breaches.

    View details for PubMedID 30420203

  • A pilot study on the use of cerebrospinal fluid cell-free DNA in intramedullary spinal ependymoma JOURNAL OF NEURO-ONCOLOGY Connolly, I., Li, Y., Pan, W., Johnson, E., You, L., Vogel, H., Ratliff, J., Gephart, M. 2017; 135 (1): 29–36


    Cerebrospinal fluid (CSF) represents a promising source of cell-free DNA (cfDNA) for tumors of the central nervous system. A CSF-based liquid biopsy may obviate the need for riskier tissue biopsies and serve as a means for monitoring tumor recurrence or response to therapy. Spinal ependymomas most commonly occur in adults, and aggressive resection must be delicately balanced with the risk of injury to adjacent normal tissue. In patients with subtotal resection, recurrence commonly occurs. A CSF-based liquid biopsy matched to the patient's spinal ependymoma mutation profile has potential to be more sensitive then surveillance MRI, but the utility has not been well characterized for tumors of the spinal cord. In this study, we collected matched blood, tumor, and CSF samples from three adult patients with WHO grade II intramedullary spinal ependymoma. We performed whole exome sequencing on matched tumor and normal DNA to design Droplet Digital™ PCR (ddPCR) probes for tumor and wild-type mutations. We then interrogated CSF samples for tumor-derived cfDNA by performing ddPCR on extracted cfDNA. Tumor cfDNA was not reliably detected in the CSF of our cohort. Anatomic sequestration and low grade of intramedullary spinal cord tumors likely limits the role of CSF liquid biopsy.

    View details for PubMedID 28900844

  • Microsurgical vs. Endoscopic Excision of Colloid Cysts: An Analysis of Complications and Costs Using a Longitudinal Administrative Database. Frontiers in neurology Connolly, I. D., Johnson, E., Lamsam, L., Veeravagu, A., Ratliff, J., Li, G. 2017; 8: 259


    Open microsurgical and endoscopic approaches are the two main surgical options for excision of colloid cysts. Controversy remains as to which is superior. Previous studies consist of small cohort sizes. This topic has not been investigated using national administrative claims data which benefits from larger patient numbers.Current Procedural Terminology (CPT) and International Classification of Disease version 9 (ICD-9) coding at inpatient visit was used to select for index surgical procedures corresponding to microsurgical or endoscopic excision of colloid cysts. Comorbidities, costs, and complications were collected.We identified a total of 483 patients. In all, 240 were from the microsurgical cohort and 243 were from the endoscopic cohort. The two groups displayed similar demographic and comorbidity profiles. Thirty-day post-operative complications were also similar between groups with the exception of seizures and thirty-day readmissions, both higher in the open surgical cohort. The seizure rates were 14.7 and 5.4% in the microsurgical and endoscopic cohorts, respectively (p = 0.0011). The thirty-day readmission rates were 17.3 and 9.6% in the microsurgical and endoscopic cohorts, respectively (p = 0.0149). Index admission costs and 90-day post discharge payments were higher in patients receiving microsurgical excision.An analysis of administrative claims data revealed few differences in surgical complications following colloid cyst excision via microsurgical and endoscopic approaches. Post-operative seizures and thirty-day readmissions were seen at higher frequency in patients who underwent microsurgical resection. Despite similar complication profiles, patients undergoing microsurgical excision experienced higher index admission costs and 90-day aggregated costs suggesting that complications may have been more severe in this group.

    View details for PubMedID 28649225

  • Neurosurgical Randomized Controlled Trials-Distance Travelled. Neurosurgery Azad, T. D., Veeravagu, A., Mittal, V., Esparza, R., Johnson, E., Ioannidis, J. P., Grant, G. A. 2017


    The evidence base for many neurosurgical procedures has been limited. We performed a comprehensive and systematic analysis of study design, quality of reporting, and trial results of neurosurgical randomized controlled trials (RCTs).To systematically assess the design and quality characteristics of neurosurgical RCTs.From January 1961 to June 2016, RCTs with >5 patients assessing any 1 neurosurgical procedure against another procedure, nonsurgical treatment, or no treatment were retrieved from MEDLINE, Scopus, and Cochrane Library.The median sample size in the 401 eligible RCTs was 73 patients with a mean patient age of 49.6. Only 111 trials (27.1%) described allocation concealment, 140 (34.6%) provided power calculations, and 117 (28.9%) were adequately powered. Significant efficacy or trend for efficacy was claimed in 226 reports (56.4%), no difference between the procedures was found in 166 trials (41.4%), and significant harm was reported in 9 trials (2.2%). Trials with a larger sample size were more likely to report randomization mode, specify allocation concealment, and power calculations (all P < .001). Government funding was associated with better specification of power calculations ( P = .008) and of allocation concealment ( P = .026), while industry funding was associated with reporting significant efficacy ( P = .02). Reporting of funding, specification of randomization mode and primary outcomes, and mention of power calculations improved significantly (all, P < .05) over time.Several aspects of the design and reporting of RCTs on neurosurgical procedures have improved over time. Better powered and accurately reported trials are needed in neurosurgery to deliver evidence-based care and achieve optimal outcomes.

    View details for PubMedID 28645203