- Traumatic Brain Injury
- Peripheral Nerve
Associate Professor - Med Center Line, Neurosurgery
Director, Defense Veterans Brain Injury Center (2009 - Present)
Associate Chief of Staff, Rehabilitation (TBI, Spinal Cord Injury, Blind Service, PM&R), PAVAHCS (2015 - Present)
Associate Chief of Staff, Polytrauma, PAVAHCS (2009 - Present)
Director, Brain Injury, Department of Neurosurgery (2009 - Present)
Honors & Awards
Research Award, The Western Neurosurgical Society (2001)
The William P. Van Wagenen Fellowship Award, American Association of Neurological Surgeons (2003)
National Road Safety Council Award, Awarded by Prime Minister and Minister of Health, Jamaica (2004)
Woodruff Leadership Academy Fellow, Emory University (2009)
Stanford Leadership Development Program, Stanford University School of Medicine (2010)
Scientific Award, Caribbean Association Neuroscience Symposium/University Hospital of the West Indies (2011)
Advanced Stanford Leadership Development Program, Stanford University School of Medicine (2012)
President, Women in Neurosurgery, Women in Neurosurgery (2012)
Stanford Faculty Research Fellow at the Michelle R. Clayman Institute for Gender Research, Stanford Michelle R. Clayman Institute for Gender Research (2012)
STARS Volunteer Leadership Assembly Honoree, Stanford Alumni Association (2013)
Board Certification: Neurosurgery, American Board of Neurological Surgery (2008)
Residency:Stanford University School of Medicine (2003) CA
Fellowship:Van Wagenen Fellowship / University Hospital of the West Indies (2004) West Indies
Fellowship:Louisiana State University - New Orleans (2007) LA
Fellowship, LSU, Peripheral Nerve (2007)
Medical Education:Stanford University School of Medicine (1996) CA
MPH, UC Berkeley, Public Health, Epidemiology (2001)
BA, Dartmouth College, Biology (1991)
Community and International Work
Neurosurgery Training and Education, Kingston, Jamaica
University Hospital of the West Indies
Opportunities for Student Involvement
Current Research and Scholarly Interests
Traumatic brain injury with a focus on epidemiology and outcomes.
- Independent Studies (5)
Abducens Nerve Avulsion and Facial Nerve Palsy After Temporal Bone Fracture: A Rare Concomitance of Injuries.
2016; 88: 689 e5-8
Avulsion of the abducens nerve in the setting of geniculate ganglion injury after temporal bone fracture is unreported previously. We discuss clinical assessment and management of a patient with traumatic avulsion of cranial nerve (CN) VI in the setting of an ipsilateral CN VII injury after temporal bone fracture and call attention to this unusual injury.A 26-year-old man suffered a temporal bone fracture after a motor vehicle accident and developed diplopia and right-sided facial droop. Six weeks after the accident, the patient was readmitted with worsening diplopia and ipsilateral facial weakness. He demonstrated absent lateral gaze on the right suggestive of either restrictive movement or right.In addition, he had right-sided facial palsy graded as 6/6 House-Brackmann. High-resolution computed tomography demonstrated a right-sided longitudinal otic capsule-sparing temporal bone fracture that propagated into the facial nerve canal and geniculate fossa. Magnetic resonance imaging revealed discontinuity of the right CN VI between the pons and the Dorello canal, as well as injury to the ipsilateral geniculate ganglion. CN VII was intact proximally, from the pons through the internal auditory canal. Consensus was reached to proceed with conservative management. At 13 months after injury, the patient reported 1/6 House-Brackmann with no improvement in CN VI function.This case illustrates 2 subtle findings on imaging with potential therapeutic implications, notably the role of surgical intervention for facial nerve palsy.
View details for DOI 10.1016/j.wneu.2015.11.076
View details for PubMedID 26723286
- Intracranial Dislocation of the Mandibular Condyle: A Case Report and Literature Review WORLD NEUROSURGERY 2016; 86
Interdisciplinary Rehabilitation Approach for Functional Neurological Symptom (Conversion) Disorder: A Case Study
2016; 61 (1): 102-111
To describe a coordinated interdisciplinary approach to the treatment of functional neurological symptom (conversion) disorder (FNSD), mixed symptoms, including motor dysfunction, in a rehabilitation setting.Adult patient was admitted with worsening neurological symptoms in the absence of contributory clinical pathology. Interdisciplinary diagnostic and treatment approach included physiatry, neuro- and rehabilitation- psychology, occupational, physical, recreational, and speech therapy. Providers coordinated care and delivered psychologically informed therapies consistent with the standards appropriate to the setting.Diagnosis of FNSD was made 5 weeks after admission. The patient achieved symptom remission at 13 weeks after admission. He remained symptom free at 6 months postdischarge.Rehabilitation settings are uniquely suited to the treatment of FNSD. (PsycINFO Database Record
View details for DOI 10.1037/rep0000063
View details for Web of Science ID 000371302000011
View details for PubMedID 26689100
- Prognostic Value of Quantitative Diffusion-Weighted MRI in Patients with Traumatic Brain Injury JOURNAL OF NEUROIMAGING 2016; 26 (1): 103-108
Prognostic Value of Quantitative Diffusion-Weighted MRI in Patients with Traumatic Brain Injury.
Journal of neuroimaging
2016; 26 (1): 103-108
Data about the predictive value of quantitative diffusion-weighted MRI in traumatic brain injury (TBI) patients is lacking. This study aimed to determine if specific apparent diffusion coefficient (ADC) thresholds could be determined that correlate with outcome in moderate-severe TBI.This retrospective observational study investigated patients with moderate-severe TBI. MRIs obtained post-injury days 1-13 were analyzed. MRIs were obtained on a 1.5T scanner; 20-23 contiguous diffusion-weighted imaging (DWI) sections with a spin-echo echo planar imaging DWI 256×256 reconstructed matrix; field of view 24×24 cm; slice thickness/gap of 5/1.5 or 5/2.5 mm. The ADC value of each brain tissue voxel was determined. The percentage of voxels below different ADC thresholds was calculated and correlated with outcome. A good outcome was defined as discharge to home or a rehabilitation facility.Seventy-six patients were analyzed. Thirty-five patients (46%) had a good outcome. The timing of MRI scans did not differ between groups, but the mean age did (42±18 years vs. 56±19 years, p<.01, good vs. poor outcome). Patients with poor outcome had significantly higher percentage of brain volume with ADC < 400×10(-6) mm2 /second (.85±.67% vs. .60±.29%, poor vs. good outcome, p<.05). Using a ROC curve analysis and Youden's index, an ADC <400×10(-6) mm2 /second in ≥.49% of brain was 85% sensitive and 46% specific for poor outcome (p<.05).Quantitative MRI offers additional prognostic information in acute TBI. A whole brain tissue ADC threshold of <400×10(-6) mm2 /second in ≥.49% of brain may be a novel prognostic biomarker.
View details for DOI 10.1111/jon.12286
View details for PubMedID 26296810
Prediction of neurosurgical intervention after mild traumatic brain injury using the national trauma data bank.
World journal of emergency surgery
2015; 10: 23-?
Patients with mild traumatic brain injury (TBI) as defined by an admission Glasgow Coma Score (GCS) of 14-15 often do not require neurosurgical interventions, but which patients will go on to require neurosurgical care has been difficult to predict. We hypothesized that injury patterns would be associated with need for eventual neurosurgical intervention in mild TBI.The National Trauma Databank (2007-2012) was queried for patients with blunt injury and a diagnosis of TBI with an emergency department GCS of 14-15. Patients were stratified by age and injury type. Multiple logistic regression for neurosurgical intervention was run with patient demographics, physiologic variables, and injury diagnoses as dependent variables.The study included 50,496 patients, with an overall 8.8 % rate of neurosurgical intervention. Neurosurgical intervention rates varied markedly according to injury type, and were only correlated with age for patients with epidural and subdural hemorrhage. In multiple logistic regression, TBI diagnoses were predictive of need for neurosurgical interventions; moreover, after controlling for injury type and severity score, age was not significantly associated with requiring neurosurgical intervention.We found that in mild TBI, injury pattern is associated with eventual need for neurosurgical intervention. Patients with cerebral contusion or subarachnoid hemorrhage are much less likely to require neurosurgical intervention, and the effects of age are not significant after controlling for other patient factors. Prospective studies should validate this finding so that treatment guidelines can be updated to better allocate ICU resources.
View details for DOI 10.1186/s13017-015-0017-6
View details for PubMedID 26060506
- Prediction of neurosurgical intervention after mild traumatic brain injury using the national trauma data bank. World journal of emergency surgery 2015; 10: 23-?
- A Systematic Review of an Emerging Consciousness Population: Focus on Program Evolution JOURNAL OF TRAUMA-INJURY INFECTION AND CRITICAL CARE 2011; 71 (5): 1465-1474
Hospital costs, incidence, and inhospital mortality rates of traumatic subdural hematoma in the United States Clinical article
JOURNAL OF NEUROSURGERY
2011; 115 (5): 1013-1018
This study provides the first US national data regarding frequency, cost, and mortality rate of traumatic subdural hematoma (SDH), and identifies demographic factors affecting morbidity and death in patients with traumatic SDH undergoing surgical drainage.A retrospective analysis was conducted by querying the Nationwide Inpatient Sample, the largest all-payer database of nonfederal community hospitals. All cases of traumatic SDH were identified using ICD-9 codes. The study consisted of 2 parts: 1) trends data, which were abstracted from the years 1993-2006, and 2) univariate analysis and multivariate logistic regression of demographic variables on inhospital complications and deaths for the years 1993-2002.Admissions for traumatic SDH increased 154% from 17,328 in 1993 to 43,996 in 2006. Inhospital deaths decreased from 16.4% to 11.6% for traumatic SDH. Average costs increased 67% to $47,315 per admission. For the multivariate regression analysis, between 1993 and 2002, 67,864 patients with traumatic SDH underwent operative treatment. The inhospital mortality rate was 14.9% for traumatic SDH drainage, with an 18% inhospital complication rate. Factors affecting inhospital deaths included presence of coma (OR = 2.45) and more than 2 comorbidities (OR = 1.60). Increased age did not worsen the inhospital mortality rate.Nationally, frequency and cost of traumatic SDH cases are increasing rapidly.
View details for DOI 10.3171/2011.6.JNS101989
View details for Web of Science ID 000296377800026
View details for PubMedID 21819196
The role of hypothermia in the management of severe brain injury. A meta-analysis
ARCHIVES OF NEUROLOGY
2002; 59 (7): 1077-1083
Hypothermia is utilized in the management of severe traumatic brain injury despite the lack of unequivocal evidence supporting its use. Because of its widespread use, the effects of hypothermia are a concern.To determine the effectiveness of hypothermia in the management of severe brain injury.Two investigators working independently abstracted data in a blinded fashion from studies identified using multiple literature databases, including MEDLINE, Ovid, PubMed, the Cochrane Database of Systematic Reviews, EMBASE, and the abstract center for the American Association of Neurological Surgery and the Congress of Neurological Surgery, as well as the bibliographies of these articles. Additionally, experts in the field of hypothermia and neurotrauma provided additional references.Seven studies met predetermined inclusion criteria: (1) the study was a randomized clinical trial comparing the efficacy of hypothermia vs normothermia in patients with posttraumatic head injury, (2) only subjects aged 10 years or older were included in the study, and (3) relative risks (odds ratios [ORs], cumulative incidence, or incidence density measures) and 95% confidence intervals (CIs) or weighted mean differences and 95% CIs could be calculated from the data presented in the article. These criteria were applied in a blinded fashion by 2 independent investigators.No single outcome variable was evaluated in all studies. The following outcome variables were assessed: intracranial pressure, Glasgow Outcome Scale score, pneumonia, cardiac arrhythmia, prothrombin time, and partial thromboplastin time. Either ORs or weighted mean differences (when the data provided did not permit calculation of an OR) comparing the effects of hypothermia vs normothermia were calculated from the data provided.The weighted mean difference (hypothermia - normothermia) for intracranial pressure was -2.98 mm Hg (95% CI, -7.58 to 1.61; P =.2). The OR (hypothermia vs normothermia) for Glasgow Outcome Scale score was 0.61 (95% CI, 0.26-1.46; P =.3). The OR for pneumonia was 2.05 (95% CI, 0.79-5.32; P =.14). The OR for cardiac arrhythmia was 1.27 (95% CI, 0.38-4.25; P =.7). The weighted mean difference for prothrombin time was 0.02 seconds (95% CI, -0.07 to 0.10; P =.7). The weighted mean difference for partial thromboplastin time was 2.22 seconds (95% CI, 1.73-2.71; P<.001).This meta-analysis of randomized controlled trials suggests that hypothermia is not beneficial in the management of severe head injury. However, because hypothermia continues to be used to treat these injuries, additional studies are justified and urgently needed.
View details for Web of Science ID 000176714500002
View details for PubMedID 12117354
Infratentorial traumatic brain hemorrhage: May outcome be predicted by initial GCS?
49th Annual Meeting of the Congress-of-Neurosurgeons
LIPPINCOTT WILLIAMS & WILKINS. 2000: 1076–82
Overall prognosis of nonpenetrating traumatic brain hemorrhage may be predicted by neurologic function days after insult. The relationship between immediate function and outcome has not been examined for infratentorial traumatic brain hemmorhage (iTBH) identified on computed tomographic (CT) scan. Given the severity of brain stem injury, it is conceivable that immediate function may be predictive.A retrospective review of 1,500 brain injuries occurring at our institution identified 18 patients (1.2%) with iTBH on CT scan (eight brain stem, five cerebellum, five both). Demographics, supratentorial injuries, and outcome at 6 months (Glasgow Outcome Scale) were recorded.Initial Glasgow Coma Scale (GCS) in 11 patients was less than 5 (group I). Seven patients had GCS scores greater than or equal to 6 (group II). Nine patients in group I either died or were vegetative. In group II, one died; none were vegetative (p < 0.02). Regression analysis demonstrated a strong correlation between initial GCS and Glasgow Outcome Scale scores at 6 months for all patients (p < 0.001).We conclude that initial GCS score may be predictive of long-term outcome in patients with CT scan evidence of iTBH-a relationship to be explored further for prognostic information.
View details for Web of Science ID 000165909500018
View details for PubMedID 11130492
Acquired cerebral arteriovenous malformation induced by an anaplastic astrocytoma: An interesting case
2000; 22 (5): 473-477
High grade gliomas foster an environment rich in angiogenic factors that promote neovascularity. We report a case of a cerebral arteriovenous malformation, which developed in the setting of a high grade astrocytoma. The patient presented with complaints of confusion and left hemiparesis. An initial cerebral angiogram was normal. Repeat angiography six weeks later demonstrated an extremely vascular lesion with arteriovenous shunting involving the right thalamus and occipital lobe. Histopathologic evaluation of open biopsy and autopsy specimens demonstrated a high grade astrocytoma in association with an arteriovenous malformation. Immunohistochemical staining with VEGF was diffusely positive. A possible role for the hyperangiogenic environment of a high grade astrocytoma resulting in the development of an arteriovenous malformation is discussed.
View details for Web of Science ID 000088406000007
View details for PubMedID 10935219
Analysis of the proliferative potential of residual tumor after radiosurgery for intraparenchymal brain metastases
JOURNAL OF NEUROSURGERY
1996; 85 (4): 667-671
A retrospective immunohistochemical study of radiosurgically treated brain metastases was performed to determine whether residual tumor has reduced proliferative potential. The monoclonal antibodies MIB-10 and PC-10 were used as markers for proliferation. The experimental group consisted of pathological specimens obtained from five patients in whom brain metastasis previously had been treated with radiosurgery. Pathological specimens obtained from 10 patients with brain metastases, matched in histology to diseases in the experimental group but untreated by radiosurgery, served as controls. A significant decrease in proliferative indices was observed in metastatic brain cancers after radiosurgery (p < 0.001). These results indicate that the persistent tumor that is present at the site of a metastasis previously treated with radiosurgery is less viable and may not in itself be a significant finding.
View details for Web of Science ID A1996VJ24700021
View details for PubMedID 8814172