After years of uncertainty for patients, New Brunswick has released the results of its neurological illness investigation.
The final report concludes that the 222 patients did not share a common exposure, pattern or underlying condition that would indicate a single cause.
Chief medical officer of health Dr. Yves Léger said the province analyzed environmental testing, medical records, hospital data and autopsy findings for patients reported between 2020 and 2025.
He said the overall results do not point to a common exposure or a widespread issue.
“Our investigation does not find evidence of a widespread issue among this patient group,” Léger said.
“We don’t think exposure to these substances is a contributing factor to most patients’ illness.”
The review began after a neurologist raised concerns in early 2023 about a growing number of patients with neurological symptoms and what appeared to be elevated levels of certain herbicides and metals.
The neurologist had reported what they believed were unusual symptoms and elevated laboratory results among some of their patients.
Public Health had received 399 notifications from the neurologist, but only 222 complete and validated reports were eligible for analysis.
A total of 320 enhanced data files were submitted, and 225 were signed off by the neurologist, with 222 included in the final dataset.
This was the second major review of the issue. An earlier investigation between 2020 and 2022 examined 48 patients and found no evidence of a common illness.
The second investigation focused on whether elevated herbicide or metal levels could be linked to illness and whether patients had diagnosable neurological conditions.
Léger said the province agreed to examine the data to help determine whether those findings were reliable and whether they could be linked to illness.
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Environmental testing results
The investigation examined biomonitoring results for glyphosate, glufosinate, their breakdown products, and nine metals, including aluminum, arsenic, cadmium, chromium, copper, lead, manganese, mercury and vanadium.
Herbicide testing covered nearly the entire patient group, with just over 200 patients tested for each substance.
Léger said more than 90 per cent of herbicide results were within expected ranges.
A small number of patients had elevated results, but nearly all repeat tests came back normal.
When compared to Atlantic Canadian reference data, herbicide levels in the patient group were “very similar” to what would be expected in the general population.
Metals testing involved blood, plasma and 24‑hour urine samples.
For example, aluminum testing included more than 250 samples across different specimen types, and lead testing included more than 270.
Some patients showed elevated metal levels, but Léger said the vast majority of results were within expected ranges.
Only a small proportion of elevated metal results were retested, and most of those repeat tests returned to normal ranges.
He said interpreting the metals data was challenging because many samples were not collected using the most appropriate specimen type.
Laboratories also used different reference ranges, and in some cases, the upper limits varied widely between labs.
When compared to national biomonitoring data, most metal levels in the patient group were the same or lower than those seen in the Canadian population.
A few exceptions appeared, but they were difficult to interpret because of the limitations in the data.
Diagnostic findings and autopsy results
The investigation also reviewed hospital records, physician billing data and autopsy reports to assess whether patients may have diagnosable neurological conditions.
Autopsies were available for nine patients.
Léger said those reports identified known conditions such as Alzheimer’s disease, Lewy body disease and Creutzfeldt‑Jakob disease.
“The reports did not indicate any unusual findings,” he said.
Nearly 60 per cent of patients had been seen by another neurologist at some point, according to billing data.
Léger said the broader evidence suggests many patients may have conditions that can be diagnosed.
“We are seeing an accumulating body of evidence suggesting that these patients may not actually have an undiagnosed condition but may have conditions that can be diagnosed,” he said.
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PHAC review and report revisions
The Public Health Agency of Canada conducted two scientific reviews of the draft report in 2025.
PHAC recommended clearer objectives, better descriptions of the patient population, additional analyses and the use of national reference data.
The Office of the Chief Medical Officer of Health adopted most of those recommendations.
The final report was shared with PHAC and released publicly on Friday.
Public Health said the investigation took time because patient files had to be completed and validated before analysis, and additional information was requested at several points during the review.
Léger said the province will implement several recommendations, including:
- improving testing practices and ensuring elevated results are repeated
- encouraging clinicians to use the correct specimen types
- urging caution when interpreting laboratory reference ranges
- supporting patients in receiving second independent assessments
- formalizing a requirement that two specialists must sign off before a case is reported as an undiagnosed neurological illness
The province has also asked PHAC to conduct a separate review of the individual patient‑level data, once consent and data‑sharing agreements are in place.
That review will look for any trends or issues of concern within the dataset.
Léger said the priority now is helping patients get clear diagnoses and appropriate care.
“These are patients who are suffering and need support,” he said.
“Our goal is to make sure patients receive accurate information and the right care.”
