Doctors in Canada are concerned they could be dealing with a previously unknown brain disease amid a string of cases involving memory loss, hallucinations and muscle atrophy. Politicians in the province of New Brunswick have demanded answers, but with so few cases, experts say there are far more questions than answers and have urged the public not to panic. For more than a year public health officials have been tracking a “cluster” of 43 cases of suspected neurological disease in the province with no known cause. Residents first learned of the investigation last week after a leaked memo from the province’s public health agency asked physicians to be on the lookout for symptoms similar to Creutzfeldt-Jakob disease – a rare, fatal brain disease caused by misformed proteins known as prions. “We are collaborating with different national groups and experts; however, no clear cause has been identified at this time,” said the memo. A number of the symptoms including memory loss, vision problems and abnormal jerking movements triggered an alert with Canada’s CJD surveillance network. Despite the initial similarities, screening produced no confirmed cases of CJD. “We don’t have evidence to suggest it’s a prion disease,” said Dr Alier Marrero, the neurologist leading New Brunswick’s investigation. Now a team of researchers, including federal scientists, are racing to determine if they are dealing with a previously unknown neurological syndrome, or a series of unrelated, but previously known – and even treatable – ailments. Marrero says patients initially complained of unexplained pains, spasms and behavioural changes – all symptoms that could be easily diagnosed as anxiety or depression. But over 18 to 36 months they began developing cognitive decline, muscle wasting, drooling and teeth chattering. A number of patients also began experiencing frightening hallucinations, including the feeling of insects crawling on their skin. In order for a new case to be included in the New Brunswick “cluster”, Marrero and his team conduct an extensive study of the patient’s history, as well as a battery of tests including brain imaging, metabolic and toxicology tests and spinal taps, to rule out other possible illnesses like dementia, neurodegenerative disorders, autoimmune disorders and possible infections. Only a single suspected case was recorded in 2015, but in 2019 there were 11 cases and 24 in 2020. Researchers believe five people have died from the illness. “We have not seen over the last 20-plus years a cluster of diagnosis-resistant neurological disease like this one,” said Michael Coulthart, head of Canada’s CJD surveillance network. The majority of cases are linked to the Acadian peninsula, a sparsely populated region in the north-eastern part of the province. The overall number of cases in the cluster remains low but New Brunswick has a population of fewer than 800,000 people. Health officials have refused to disclose the precise locations of the cases. Marrero and his team have consulted experts in neurology, environmental health, field epidemiology, zoonotics and toxicology to better understand what could be causing the mystery illness. A growing team of researchers is working to determine if there is a common link to the cases or any environmental causes, including water sources, plants and insects. “We don’t know what is causing it,” said Marrero. “At this time we only have more patients appearing to have this syndrome.” News of the unknown illness has prompted concern but experts have cautioned against drawing premature conclusions. “I don’t really know if we even have a defined syndrome. There just isn’t enough information yet,” said Valerie Sim, a researcher of neurodegenerative diseases at the University of Alberta. She noted that key markers for degenerative neurological illnesses had not been documented and that the wide range of symptoms in the cluster was “atypical” for most brain diseases. At the same time, certain cancers, dementia or even misdiagnoses could explain the scope of symptoms, she said. The saga also exposes the frustrating reality of medicine: diagnosing a patient can be tough and it is a task riddled with unknowns. Neurologists can often deploy a number of tools in treating a patient when the root cause of an ailment is unclear, “and then the patient somehow recovers. You come away never knowing what they actually had,” said Sim. “We see odd neurological syndromes from time to time. Sometimes we figure them out. Sometimes we don’t.”