Leadership & Physicians

Driving our mission to return patients to lives of productivity and meaning are our leadership team, physicians, and clinicians. The entire Nexus Health Systems family is committed to mending minds and helping our patients and their families during the recovery process.


Erin Cassidy, MSN, MBA



Erin Cassidy joined Nexus Health Systems in 2008 and is currently the President. Prior to assuming her current role, she held various roles at Nexus Specialty Hospital including CEO and Administrator, Operations Specialist, and Assistant Administrator. She began her career at Nexus as a Marketing Liaison. Prior to joining Nexus, Ms. Cassidy held several leadership positions in medical doctor practice management in Sydney, Australia.

Ms. Cassidy holds a Bachelor of Arts in Sociology and Anthropology from Smith College and a Certificate in Culture Health Sciences from the Five College Consortium. In addition, she holds a Masters in Nursing from the University of Sydney, and a MBA with a concentration in Health Care Management from Rice University.


John Cassidy, MD

Founder, Chief Executive Officer, Chief Medical Officer


Dr. John W. Cassidy is certified by the American Board of Psychiatry and Neurology and has over 30 years of experience in clinical neuroscience and neurobehavioral rehabilitation programs. Currently operating as CEO and Chief Medical Officer of Nexus Health Systems – which he founded in 1992 – Dr. Cassidy was previously the Psychiatrist in Charge and Co-Founder of the Neuropsychiatry Program at McLean Hospital; Chief Medical Officer and Founder of the Neurobehavioral Institute of Houston; Director and Founder of the Neuropsychiatry Subspecialty Services of Del Oro Rehabilitation Hospital; and Medical Director of Neurobehavioral Programs at Cypress Creek Hospital.

Devoting his career to improving the understanding and treatment of individuals with acquired and traumatic brain injuries, Dr. Cassidy continues to help patients return to productive and meaningful lives through a neurospecialty continuum of care. His comprehensive rehabilitative approach delivers more than traditional therapies, addressing a person’s interpersonal, behavioral, cognitive, physical, and emotional challenges to ensure a more successful rehabilitation journey and clinical outcome.

Dr. Cassidy received his Bachelor of the Arts from Hiram College and Doctor of Medicine from the University of Cincinnati College of Medicine. In addition, he received his post-graduate training at Harvard Medical School. Dr. Cassidy has spoken nationally and internationally about the sequela and management of severe traumatic brain injury and authored three books and a number of papers, book chapters, and editorials.


Joel Talley

Chief Operations Officer


Propelling Nexus’ vision, Joel Talley works directly with facility administration to create and communicate facility strategy. He oversees new program development and ensures alignment with corporate goals. Mr. Talley joined the Nexus team in 2012 as a member of the Finance Department. Prior to this latest promotion, he was VP of Business Development. Before his tenure at Nexus, Mr. Talley accumulated nearly ten years in the finance and healthcare industries. Between his sales and finance experience, Mr. Talley looks forward to driving growth and ensuring all facilities run efficiently.


Ann De la Rosa, RN, BSN, CRRN

VP of Sales & Marketing


Ann De la Rosa graduated from UT Health Science Center in Houston, Texas in 1990 with a Bachelor’s of Science in Nursing, and has been a practicing nurse for 26 years. In 2011, she received certification as a Rehabilitation Nurse. Her tenure includes time as a SICU/PACU staff nurse responsible for patient care and clinical liaison responsible for community outreach and education for case managers and physicians.

Ms. De la Rosa has been with Nexus Health Systems for over 20 years, and has been in a marketing and clinical liaison role for most of that time. She is currently based out of the Nexus Health Systems corporate office as the VP of Business Development and assists all facilities and clinical teams. She is responsible for national outreach, education, and patient evaluations. Ms. De La Rosa also collaborates with insurance companies, worker’s compensation, and the military to provide solutions for complex cases.


Kim Fields, MBA, CPA

VP of Finance


As the head of the finance department, Kim Fields oversees the accounting and purchasing divisions, manages internal and external financial reporting and cost containment, and develops performance measures that support Nexus’ strategic direction. For nearly the past five years, Ms. Fields has worked exclusively for Nexus’ finance department. Prior to her time with Nexus, she was a Senior Auditor at Deloitte and was a Financial Analyst for an Austin-based healthcare system. Ms. Field’s extensive background in finance, coupled with her existing knowledge of Nexus Health Systems, proves to be invaluable.


Kevin McAndrews, MHR

VP of Human Resources


Kevin McAndrews brings a depth of HR management expertise with over 20 years of experience in the bio-instrumentation and healthcare industry. The past 15 years, Mr. McAndrews held executive leadership roles within the private, private equity, and publicly traded organizations. He joined Nexus Health Systems in June 2015 as the Vice President of Human Resources. In his previous roles Mr. McAndrews oversaw all national and international human resources offices, with offices and HR Staff in over 10 countries. Additionally, under Mr. McAndrews leadership, his past companies have been recognized and received the Wall Street Journal Best Places to Work, The International Spirit at Work Award, Red Cross Platinum Award, and Inc. 5000 Fastest Growing Companies.

Mr. McAndrews holds a Bachelor’s Degree in Sociology & Psychology from Loyola Marymount University in Los Angeles and holds a Master of Science in Human Resources from Golden Gate University in San Francisco. He is a native of Los Angeles and a full-time resident of Houston since 2015.


Eric Cantrell

VP of Business Development


Eric Cantrell is CEO of both Nexus Specialty Hospital campus in Shenandoah and The Woodlands, overseeing all aspects of operations. He also identifies and executes immediate and long-term goals that include improving operational efficiencies, developing more extensive in-house service offerings, enhancing patient care and satisfaction, and implementing strategies to best place patients in Nexus’ continuum of care. Prior to his new role with Nexus Health Systems, Mr. Cantrell has held various CEO positions since the mid-2000s. His successes as part of healthcare administration range from negotiating agreements and physician recruitment, to meeting or exceeding patient quality benchmarks and increasing revenue.


Mary Harbeson, BSN, MS

Chief Executive Officer, Nexus Children’s Hospital


Mary Harbeson joined Nexus Health Systems in 2018 with over 30 years of experience in the healthcare industry. As CEO of Nexus Children’s Hospital in Houston, she oversees all aspects of operations, patient care and satisfaction, clinical staff, and medical decisions.

As an RN, Ms. Harbeson has held positions in various leadership roles including VP Clinical Operations, Chief Clinical Officer, and CEO. She is a focused and resourceful executive with a solid background in advancing quality patient care through strategic planning, program development, and physician recruitment. She has advanced expertise in designing and leading hospital construction from the ground up, as well as expanding market share and controlling costs. Ms. Harbeson also has a notable history of recognition for quality and safety, in addition to improving customer perception of care.

Ms. Harbeson holds a Bachelor of Science in Nursing from UTMB Galveston and a Master of Science – Nursing and Healthcare Administration from Texas Women’s University.


Randy Thompson, FACHE

Chief Executive Officer, Nexus Specialty Hospital


Randy has almost 20 years of healthcare management experience in various rehabilitation and acute care facilities. His most recent senior leadership role was at a rehabilitation facility where he served as the Associate Administrator/Chief Executive Officer. Randy received his Master’s degree in Business Administration from Webster University. He also became a fellow of the American College of Healthcare Executives (FACHE) and earned a Lean Six Sigma Black Belt certification. Randy enjoys spending time with his family and exercising by practicing jiu-jitsu.


Tracy Wilson, M.S., CCC-SLP

Chief Executive Officer, Nexus Neurorecovery Center


By trade, Tracy is a Speech-Language Pathologist and is always focused on providing quality care to patients. She joins Nexus with over 25 years of healthcare management experience, ranging from Director of Rehabilitation Services to Chief Executive Officer. In her most recent role, Tracy was the Senior Director of Quality and Client Experience at a nationally known rehabilitation facility. She oversaw the national wellness program and was responsible for survey preparation for more than 30 rehabilitation facilities. In her free time, you will find Tracy fishing around the local area or spending time with her family.


Anita Marban

Corporate Director of Clinical Operations

Anita has a wealth of experience as a Clinical Leader, including past positions as Director/Chief Nursing Officer at Houston Methodist, HealthSouth, and Memorial Hermann Health Systems. She also held Director positions at the National Institutes of Health in Bethesda, Maryland. Anita obtained her Bachelor of Science in Nursing from the University of Florida and her Master of Health Administration from the University of Maryland. She advances clinic care and improves outcomes by working with all facility leadership as a resource for best practices, clinical operations, accreditations, quality, and risk management. Her role is crucial in helping Nexus meet and exceed our clinical goals and outcomes.
Nexus Physician Services

Since its inception in 2014, Nexus Physician Services has recruited physicians and physician extenders, including nurse practitioners and physician assistants, who have specialized education and training. Additionally, our physicians are board certified in a variety of specialties that permit medical interdisciplinary treatment of our patients, including: neurology, psychiatry, neuropsychiatry, pediatric neuropsychiatry and adult and pediatric physical medicine and rehabilitation.

Exclusively caring for our neurospecialty patients full-time, Nexus Physician Services represents a group of doctors who are dedicated to furthering our neurocontinuum of care and supporting our patients and their families. Additionally, these physicians educate our staff and community through continuing education presentations, grand rounds, and other educational opportunities.

Physicians associated with this elite group are aligned to Nexus’ standards and treatment philosophy. All doctors who are a part of Nexus Physician Services are under our supervision and clinically report to Dr. John Cassidy, Chief Medical Officer.

Services Include:

  • Inpatient and outpatient consultation
  • Record review
  • Legal case review
  • Pre-program placement comprehensive assessment
  • Program recommendations

Journey Toward Independence

Nexus' NeuroContinuum sequence provides a range of care for those recovering from acquired or traumatic brain injuries and other complicated illnesses or diseases.
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