We are the only neurological rehabilitation clinic that specializes in measuring and training the systems that regulate blood flow to the brain.
See How This Works
The tilt table test is the standard in autonomic testing, but we do not view it as sufficient on its own. We combine autonomic testing with tools more often seen in state-of-the-art research settings to measure how blood flow to the brain is being regulated under stress, use those findings to guide treatment, and then measure progress throughout your visit.
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Patient Success & Communications
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Clinical Director and Founder
Dr. Nathan Keiser founded The Keiser Clinic and developed the brain-first approach that defines our care. A board-certified chiropractic neurologist, he was certified as a diplomate in chiropractic neurology by the American Board of Chiropractic Neurology (ACNB) in 2010 and has worked with patients from across North America and around the globe.
As Clinical Director, Dr. Keiser leads our team's daily case rounds, reviews each patient's neurodiagnostic testing, and oversees treatment strategy. His focus is on the diagnostic and clinical thinking that makes the team's hands-on work effective.
Dr. Keiser also serves as an Assistant Professor of Clinical Neurology for the Carrick Institute, which provides Post-Graduate instruction for doctors of all disciplines in the field of clinical and functional neurology. He is actively involved in ongoing research and presents regularly across North America and Europe.
Outside of work, you'll usually find Dr. Keiser with his wife and three kids, at one of their sports or outside together. When he gets a quiet hour, it's almost always at the gym.
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Administrative Lead
Dr Claire Keiser is a board certified chiropractic neurologist specializing in the non-surgical, non-pharmaceutical treatment of dysautonomia, traumatic brain injury, and movement disorders. She was certified as a diplomate in chiropractic neurology by the American Board of Chiropractic Neurology (ACNB) in 2010 after graduating from Life University.
Since 2018, she's taken a step back from her clinical work to stay at home with the Keiser's 3 young children. She currently serves as the clinic's administrative lead. Her vast clinical knowledge is an asset to the Keiser Clinic team, supporting patient coordination and serving as an additional resource throughout the treatment process.
Outside of ensuring the clinic runs smoothly and her duties as Keiser Mom Extraordinaire, Claire is an avid Crossfit athlete and loves to experiment in the kitchen.
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Dr. Erin Kepreos DC, DACNB is a board-certified chiropractic neurologist specializing in non-surgical, non-pharmaceutical treatments for dysautonomia, traumatic brain injury, and movement disorders. She achieved diplomate status in chiropractic neurology from the American Board of Chiropractic Neurology (ACNB) in 2023. Dr. Kepreos earned her Bachelor of Science in Kinesiology from Queen's University before obtaining her Doctorate of Chiropractic from Life University.
Originally from Toronto, Canada, Dr. Kepreos finds joy in exploring Michigan alongside her husband. Outside of the clinic, she embraces outdoor activities such as hiking, swimming, and skiing.
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Dr. Alexa Tenwalde, DC, DACNB, FACFN, is a board-certified chiropractic neurologist specializing in non-surgical, non-pharmaceutical treatments for dysautonomia, traumatic brain injury, and movement disorders. She achieved diplomate status in chiropractic neurology from the American Board of Chiropractic Neurology (ACNB) and fellowship recognition from the American College of Functional Neurology (ACFN) in 2023.
Dr. Tenwalde earned her Bachelor of Science in Biomedical Sciences from Grand Valley State University before obtaining her Doctorate of Chiropractic from Life University. Her clinical interests include supporting individuals with complex neurological and autonomic presentations through individualized, functionally-integrated rehabilitation programs.
A proud Michigander, Dr. Tenwalde enjoys ice hockey, rollerblading, skate skiing, and woodworking outside the clinic.
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Dr. Corissa Mattson, DC, DACNB, is a board-certified chiropractic neurologist specializing in non-surgical, non-pharmaceutical treatments for dysautonomia, traumatic brain injury, and movement disorders. She achieved diplomate status in chiropractic neurology from the American Board of Chiropractic Neurology (ACNB) in 2026. Originally from the Upper Peninsula of Michigan, Dr. Mattson attended the University of Michigan and obtained her Bachelor of Science degree in Biology and Creative Writing before going on to receive her Doctorate of Chiropractic from Life University.
Dr. Mattson first encountered functional neurology while interning for a summer at the Keiser Clinic. Since then, she has developed a passion for helping individuals with dysautonomia and other neurological conditions get back to living their lives. Outside of the clinic, she enjoys disc golfing with her husband, skiing, rollerblading, and reading science fiction and fantasy books.
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Dr. James R. Muldoon, BS, DC, DACNB, is a chiropractic neurologist born and raised in Michigan. He is proud to serve the community he calls home and is passionate about helping patients achieve healthier, more active lives. He specializes in both traditional musculoskeletal conditions and complex neurological disorders, and after 11 years of running his own clinic, he couldn't resist the opportunity to join The Keiser Clinic.
Dr. Muldoon earned his Bachelor of Science in Movement Science from the University of Michigan, where he competed as a wrestler and developed a passion for human performance and rehabilitation. He went on to receive his Doctor of Chiropractic degree from Life University before completing extensive postgraduate training through the Carrick Institute for Graduate Studies and earning his Diplomate of the American Chiropractic Neurology Board (DACNB).
With more than 15 years of clinical experience and hundreds of hours of advanced neurological education, Dr. Muldoon focuses on identifying and addressing dysfunction within the nervous system. He treats a wide range of conditions, including post-concussion/mTBI, dysautonomia, post-COVID, chronic pain, headaches and migraines, sports injuries, balance disorders, movement disorders, and other complex neurological conditions.
Known for his patient-centered approach, Dr. Muldoon believes every patient deserves a personalized treatment plan tailored to their unique needs and goals. He is committed to lifelong learning and continually integrates the latest research and clinical techniques into his practice.
Outside the clinic, Dr. Muldoon enjoys spending time with his wife, Christy, and their children. He has a passion for faith, family, and functional neurology, and in his spare time he enjoys Brazilian jiu-jitsu, hunting, fishing, snowboarding, and golf.
Team Member
Kelly has been a valued member of The Keiser Clinic team since 2023. She is passionate about creating a comfortable and supportive experience for those undergoing treatment away from home.
Her compassion and empathy are deeply rooted in personal experience, having navigated years of syncope and the challenges of post-concussion recovery herself. These experiences allow her to connect with others in a genuine and understanding way.
Kelly holds a BFA from Michigan State University and is a Michigan native. As a mother of three, caregiving has always been at the heart of her life. Outside the clinic, she enjoys home renovation projects and exploring the outdoors with her family and their three-legged dog, Hugo.
Patient Success & Communications
Dr. Ginia Marsico, originally from Milwaukee, Wisconsin, holds a Bachelor's in Mass Communication (Public Relations) from the University of Wisconsin-Milwaukee, and a Doctorate of Chiropractic from Southern California University of Health Sciences. With a background in sports, health, and wellness, she and her husband previously owned a functional training gym and wellness facility in Los Angeles.
Having faced severe illness with POTS herself, her personal journey through recovery at the Keiser Clinic ignited a passion to support others navigating their own health paths. Now based in Orlando, Florida, she finds joy in helping patients at the clinic reach their goals and regain their wellness.
When she's not working, she's often found spending quality time with her husband and son at Disney World.
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Dr. Yuliya Gruppina, DC, is a licensed chiropractor in California with more than 10 years of clinical experience helping patients improve mobility, function, and overall well-being. She earned her Doctor of Chiropractic degree and a Master's in Oriental Medicine from Southern California University of Health Sciences.
Dr. Gruppina utilizes a comprehensive approach to care that may include chiropractic adjustments, soft-tissue therapy, corrective exercises, acupuncture, and therapeutic taping. Her focus is on helping patients move better, recover from injury, and maintain active, healthy lifestyles.
Raised in the San Fernando Valley in a family with a strong healthcare background, Dr. Gruppina is passionate about patient-centered care and empowering individuals through education and personalized treatment. Outside the clinic, she enjoys reading, cooking, and spending time with her toddler.
We have spent over a decade walking this path with people like you. We come each day ready to listen and provide the best possible care.
We aim to empower our patients and know those that invest in their own healing usually see the best results.
Your time is valuable. We promise to be honest, real, and straight forward with you regarding your success.
Applying the right treatments in the correct dosage for each individual patient is a primary reason for our patients' success.
Find and fix the driver of your neurological symptoms.
We combine advanced diagnostic technologies with the latest in clinical neuroscience and a patient centered approach to identify and correct the imbalances driving your symptoms.