• A new study in JAMA Neurology found no evidence of a novel neurological disease in a cluster of patients in New Brunswick, Canada, attributing symptoms to known conditions.
• The study involved re-evaluating 25 patients and autopsy data, leading researchers to identify conditions like Alzheimer's, Parkinson's, traumatic brain injury, and functional neurological disorder.
• The findings are disputed by the neurologist who initially identified the cluster and some patient advocates, who believe environmental factors may be at play.

A controversy arose in New Brunswick, Canada, starting around 2019 with reports of residents exhibiting a range of neurological symptoms that defied easy diagnosis. Moncton neurologist Dr. Alier Marrero identified a cluster of patients with symptoms including hallucinations, muscle spasms, memory loss, and balance issues, suggesting a possible 'neurological syndrome of unknown cause' (NSUC). This led to investigations by provincial health officials and sparked widespread concern. A new study published in JAMA Neurology challenges the existence of such a novel syndrome, re-evaluating a subset of these cases and attributing the symptoms to known neurological conditions. The debate continues, with some advocating for further investigation into potential environmental triggers and questioning the study's methodology.

• What: A study published in JAMA Neurology analyzed 25 patients previously diagnosed with a 'neurological syndrome of unknown cause' in New Brunswick, concluding that their symptoms could be attributed to known conditions like Alzheimer's, Parkinson's, traumatic brain injury, and functional neurological disorder.
• Who: Key individuals involved include Dr. Anthony Lang (lead author of the JAMA Neurology study), Dr. Alier Marrero (Moncton neurologist who first identified the cluster), Dr. Yves Léger (New Brunswick's chief medical officer of health), Stacie Quigley Cormier (patient advocate), and Susan Holt (Premier of New Brunswick).
• When: The controversy began around 2019. The JAMA Neurology study was published in May 2024, with data collected between November 2023 and March 2024. The New Brunswick government launched its investigation in March 2025, with results expected in the summer.
• Where: The events primarily occurred in New Brunswick, Canada, although some patients were also from neighboring provinces. The research was conducted by researchers from the Horizon Health Network in New Brunswick and the University Health Network in Ontario.

The JAMA Neurology study attempts to resolve a long-standing controversy surrounding a cluster of neurological cases in New Brunswick. By re-evaluating patients and autopsy data, the researchers provide evidence against the existence of a novel 'mystery' disease, attributing symptoms to known conditions. However, the study is not without its critics. Dr. Marrero, who initially identified the cluster, disputes the findings and questions the study's methodology. Patient advocates also express skepticism, arguing that the study does not address potential environmental factors contributing to the illnesses. This controversy highlights the challenges of diagnosing complex neurological disorders and the importance of clear communication between healthcare professionals, patients, and the public. The differing opinions also suggest that there is a decline in public trust in health institutions since the COVID-19 pandemic. The study may not fully resolve the concerns of those who believe in the existence of a novel syndrome, but it provides valuable insights and emphasizes the need for thorough evaluations and multidisciplinary support for patients with neurological symptoms.

"I am in profound disagreement with the study conclusions and have many questions regarding the methods and the content."

"We really felt we had a good explanation for 100% of the cases."

"Sadly, the one thing that all the patients have in common is the same neurologist. And the patients who have been seen by other neurologists get a diagnosis of a known entity that’s not a mystery."

Why in a province so small as New Brunswick, why are so many people experiencing these neurological symptoms, neurological conditions?

The JAMA Neurology study offers a significant counterpoint to the theory of a novel neurological disease in New Brunswick, providing evidence that the symptoms observed can be attributed to known conditions. While the study is likely to generate further debate and may not fully resolve the concerns of all stakeholders, it underscores the importance of rigorous scientific evaluation, multidisciplinary assessment, and clear communication in addressing complex health issues. The ongoing investigation by the New Brunswick government will provide further insights, and addressing the underlying factors contributing to public concern and mistrust in health institutions remains crucial.