Neurosurgery Advanced Practice Providers

Our neurosurgery nurse practitioners and physician assistants have advanced educational and clinical experiences that contribute to our academic programs. They treat all patients with kindness and respect, and offer information services that promote healing and lead to healthier life styles.

Bonnie Taft, MSN, RN, CPNP
Bonnie Taft, RN, MSN, CPNPBonnie is a Certified Pediatric Nurse Practitioner (CPNP) with a rich background in the pediatric primary care setting. Bonnie is also an experienced educator and served as a member of the pediatric clinical faculty at the University of California at San Francisco for several years. Bonnie completed her undergraduate degree at State University of New York at Stony Brook in 1994 and she later went on to attain her Master of Science in Nursing at Boston College in 2003.
Candice Osuga Lin, MSN, APRN, BC, ACNP
Candice Osuga Lin, MSN, APRN, BC, ACNPCandice earned her Bachelor of Science in Biological Sciences from the University of California at Davis and her Master of Science in Nursing with clinical specialization as an Acute Care Nurse Practitioner from Vanderbilt University. Candice came to Stanford Hospital & Clinics as Staff Nurse in the Medical, Surgical Intensive Care Unit (E2ICU). She joined the Department of Neurosurgery as a nurse practitioner and has been active with neuro-oncology and spine neurosurgery. Candice has been the study coordinator on several research studies and has a passion for patient care.
David E. Stewart, MBA, PA-C
David Stewart, PA David joined the Neurosurgery department in 2013 after more than a decade of clinical practice as a physician assistant. After obtaining his Bachelor of Arts in Russian Language and Literature from the University of Southern California in 1998, he obtained his Bachelor of Science in Health Sciences in 2001 and a Masters in Business Administration in 2008. David is a member of the of the American Academy of Physician Assistants, Association of Neurosurgical Physician Assistants, California Academy of Physician Assistants, American College of Physicians, American College of Physician Executives, and the American Association of Nurse Practitioners.
Elizabeth Lee, MSN, RN, NP
Elizabeth Lee, MSN, RN, NPElizabeth joined the Department of Neurosurgery in 1996. She obtained her Bachelors of Science in Nursing in 1992, and her Master of Science as Family and Geriatric Nurse Practitioner in 1996 from the University of California, Los Angeles. Currently, her practice focuses on neurosurgical treatments of brain and spine tumors, arteriovenous malformations, and aneurysms using conventional surgery and/or Cyberknife Radiosurgery. Her 17 year nursing career has always been devoted to neurosurgery both in the inpatient and outpatient settings. She is a member of Sigma Theta Tau, facilitates local brain tumor support groups, and has published many articles regarding the use of Cyberknife in the treatment of brain and spine diseases. She has received several grants to support educational projects for brain tumor and Parkinson's disease support groups.
J.J. Baumann, MS, RN, CNS
JJ Baumann, RN, MS, CNS After finishing her masters in critical care/trauma nursing at UCSF, JJ joined the Stanford team.  With a passion for neuroscience and acute care, she initially worked with the Stanford Stroke Service before her current position with the Department of Neurosurgery.  She specializes in acute care management of hospitalized neurosurgical patients.  JJ is an active member of the American Association of Neuroscience Nurses and the Neurocritical Care Society of Medicine. 
Joli Vavao, MSN, ACNP, CNRN
Joli VavaoJoli joined the Neurosurgical team in 2004. She obtained her masters degree as an acute care nurse practitioner from the University of California, Los Angeles. She has worked as a nurse for over 13 years specializing in neurosurgery and stroke neurology. She has received national certification in neuroscience nursing. She plays an active role coordinating the care of cerebrovascular patients in both an inpatient and outpatient setting. She participates in lectures to hospital staff and local health care professionals regarding the care of neuroscience patients.
Joy Sabig, RN, CCRN, MSN, Adult NP- BC
Joy Sabig, NP  Joy Sabig earned her Bachelor of Science in Nursing from the University of St. La Salle in the Philippines and her Masters of Science Degree as an Adult Nurse Practitioner from Florida International University.  Joy came to Stanford Hospital in 2003 and worked in the Cardiovascular ICU as an RN and relief Charge Nurse before working as a Nurse Practitioner in the Pre-Op Anesthesia Department in 2007.   In 2010, she transferred to Vascular Surgery and worked there for 2 years before joining the Neurosurgery Team in November of 2012.  Her experiences as an NP include working in the Anticoagulation Clinic at UCSF and Cardiology at SFGH. 

Mary L. Marcellus, RN
Mary L. Marcellus, RNOriginally from Connecticut, Mary came to Stanford in 1980. She began as a staff nurse in the ICU and then went on to become an Assistant Nurse Manager for several years before taking on the role of Interventional Neuroradiology Nurse Coordinator in 1993. She has lectured on various cerebrovascular topics as well as published several articles in her area of expertise. Patient advocacy remains the most important part of her daily patient care responsibilities
May Casazza, CPNP
May is a certified pediatric neurosurgery nurse practitioner with extensive experience working with pediatric intensive care patients. May received her undergraduate nursing degree from Johns Hopkins University and her graduate training at UC San Francisco.

Melissa Ballard, BSN, MSN, RN, CPNP
Melissa Ballard, RN, MSN, CPNPMelissa is a Certified Pediatric Nurse Practitioner (CPNP) specializing in the care of hospitalized children with an emphasis in the transition from intensive to acute care, end-of-life care and all acute care settings. She received a Bachelor of Science in Nursing from San Francisco State University in 1985 and a Master of Science in Nursing as an Acute Care Pediatric Nurse Practitioner from University of California, San Francisco in 2007.

Melissa Lewis, MSN, ANP-BC
Melissa Lewis, NP-BCMelissa has been at Stanford Hospital since 2006, working with the neurosurgery and general patient populations. She received her Bachelor of Science in Nursing from Brigham Young University in 2006, and her Master of Science in Nursing from University of California San Francisco in 2011. Now as a Nurse Practitioner she works with patients and their families in the Neuroscience Department working in both the inpatient and outpatient settings. She coordinates care for patients with vascular malformations, moyamoya, aneurysms and tumors.
Olivia Chu, MSN, FNP
Olivia Chu, MSN, FNPOlivia is a family nurse practitioner providing care for patients in the Pituitary Center of the Department of Neurosurgery since 2006. She obtained her undergraduate degree at University of California, Berkeley, and completed a bachelors and masters degree at Johns Hopkins University. Currently she specializes in neuro-endocrine cases, predominately pituitary tumors.


Teresa Bell-Stephens, RN, BSN, CNRN
Teresa Bell-StephensTeresa came to Stanford from the East Coast in 1988. She worked in critical care for many years before joining the Department of Neurosurgery in 1990. She has coordinated programs in cerebrovascular surgery since then. Teresa is an excellent resource for information on vascular malformations, aneurysms and Moyamoya disease, and is available to guide care for patients and families before, during and after their treatment at Stanford Hospital & Clinics. Teresa has been involved in clinical research trials that have studied various methods of neuroprotection, including mild hypothermia, in patients with stroke and head injury. She regularly lectures in the Bay Area, and nationally and internationally.
Vania Bernatsky, NP
Vania BernatskyVania received her Master of Science in Nursing with a minor in Education from the University of California, San Francisco in 2001. She is certified as an Acute Care Nurse Practitioner through the American Academy of Nurse Practitioners, and is a member of the American Association of Neurosciences Nursing, American Association of Nurse Practitioners and Sigma Theta Tau. She has spent her career caring for patients both in acute care inpatient, as well as outpatient settings.

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