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.

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 metabolites, and nine metals, including aluminum, arsenic, cadmium, chromium, copper, lead, manganese, mercury and vanadium.

Léger said most herbicide results were within expected ranges.

When compared to Atlantic Canadian reference data, the levels in the patient group were “very similar” to what would be expected in the general population.

Nearly all repeat tests for herbicides came back normal.

For metals, some patients had elevated results, but Léger said the vast majority of tests were within expected levels.

When compared to national reference data, most metal levels were the same or lower than those seen in the Canadian population, with a few exceptions.

He said those exceptions were difficult to interpret because of significant limitations in the data.

One of the most important limitations, Léger said, was the lack of repeat testing.

Only about one in five elevated results were tested again, and most of those repeat tests came back normal.

“Very few results that came back as high were retested,” he said. “This greatly affects our ability to interpret those results.”

The investigation also found that many samples were not collected using the most appropriate specimen type, which can affect accuracy.

Laboratories used different reference ranges, and in some cases, the upper limits varied widely between labs.

Population comparisons and health‑based guidance values

The province compared patient results to the Canadian Health Measures Survey, which provides national and regional biomonitoring data.

Léger said this comparison was the most useful because it allowed the province to see whether the patient group differed from the general population.

Most results were similar to national or Atlantic Canadian levels.

For metals that showed some elevated values, the province looked for health‑based guidance values—thresholds below which no health effects are expected.

Léger said only a few patients exceeded the available value for aluminum, and none of those results were confirmed through repeat testing.

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.

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.”