TORONTO, May 7, 2025 /CNW/ – A study published today in JAMA Neurology has found patients previously diagnosed with a “mystery brain disease” that emerged in New Brunswick, Canada, had known neurological conditions—some involving brain cell damage, such as dementia, and others not involving degeneration, like head injuries.
Led by Dr. Anthony Lang, a neurologist and Senior Scientist at University Health Network’s (UHN) Krembil Brain Institute, the study was a collaboration between Horizon Health Network in New Brunswick and UHN in Toronto. It involved a detailed clinical and pathological (post-mortem tissue) analysis of 25 individuals previously labeled as having New Brunswick Neurological Syndrome of Unknown Cause (NSUC).
Researchers conducted independent clinical evaluations of 14 patients and autopsy evaluations of 11 deceased individuals. Most of the 105 patients originally identified either did not respond or declined the offer for further investigation.
“We found that what had been termed a ‘mystery brain disease’ was, in fact, a collection of identifiable medical conditions,” said Dr. Lang. “These included well-characterized neurological disorders, such as Parkinson’s disease, dementia, traumatic brain injury, and functional neurological disorder, a condition where physical symptoms like tremors or memory issues occur without clear structural brain damage.”
The research team reviewed clinical records and diagnostic tests—including MRI scans, brain blood flow studies, and electroencephalograms (EEGs), which measure electrical activity in the brain—spanning from 2019 to 2025. They found no evidence of a novel or previously unidentified disease in any of the 25 cases.
The study also revealed significant discrepancies in many cases between the original clinical documentation and the findings from the second, independent assessments. Some diagnoses leaned too heavily on specific tests without enough clinical context on certain diagnostic tests. In all 25 cases, researchers found no evidence of a new disease.
“By analyzing the data, we were able to clarify the specific conditions contributing to the patients’ symptoms,” said Dr. Nathaniel Bendahan, a UHN Clinical Research Fellow at the time and first author of this study. “Rather than a single new disease, we found a range of distinct neurological diseases.”
The findings underscore the importance of expert second opinions in complex or uncertain neurological cases—especially when initial diagnoses are unclear.
“Involving input from various health care professionals such as neurologists, psychologists, and rehabilitation specialists can play a vital role in guiding patients through complex and uncertain diagnostic journeys,” added Dr. Lang.
About the Krembil Brain Institute
The Krembil Brain Institute at Toronto Western Hospital, part of University Health Network, is home to one of the world’s largest and most comprehensive teams of physicians and scientists uniquely working hand-in-hand to prevent and confront problems of the brain and spine. One in three Canadians will experience a brain-related condition such as Parkinson’s, Alzheimer’s or epilepsy in their lifetime. Through state-of-the-art patient care and advanced research, we are working relentlessly to find new treatments and cures. For more information, visit: www.uhn.ca/krembil
About University Health Network
UHN is Canada’s No. 1 hospital and the world’s No. 1 publicly funded hospital. With 10 sites and more than 44,000 TeamUHN members, UHN consists of Toronto General Hospital, Toronto Western Hospital, Princess Margaret Cancer Centre, Toronto Rehabilitation Institute, The Michener Institute of Education and West Park Healthcare Centre. As Canada’s top research hospital, the scope of biomedical research and complexity of cases at UHN have made it a national and international source for discovery, education, and patient care. UHN has the largest hospital-based research program in Canada, with major research in neurosciences, cardiology, transplantation, oncology, surgical innovation, infectious diseases, genomic medicine and rehabilitation medicine. UHN is a research hospital affiliated with the University of Toronto. For more information, visit: www.uhn.ca
SOURCE University Health Network
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