A report by Canadian officials has found no evidence of a new disease after hundreds of reports of neurological symptoms led to claims of a mystery brain condition.
The results of the investigation by New Brunswick's Chief Medical Officer of Health add to a growing body of research that suggests patients may have diagnosable illnesses instead.
About 500 people in New Brunswick and other provinces have been identified by neurologist Dr Alier Marrero as having unexplained neurological symptoms.
Officials said they also found no evidence to support Marrero's claims that patients' symptoms were caused by elevated levels of herbicides and heavy metals. The BBC has contacted Marrero for comment.
"Regardless of the findings of our investigation, the fact remains there are patients who are very ill and need support," said New Brunswick's chief medical officer of health Dr Yves Léger on Friday.
