When the immune system attacks the brain

As a parental nightmare, Rasmussen’s Syndrome is a degenerative disease that primarily targets young children, in which it causes brain damage, seizures, cognitive decline and irreversible learning disabilities. “But it often takes a first attack to diagnose the disease,” says the professor of neuroscience at the University of Montreal, Alexander Prat.
With a recent study, a Quebec team, of which the researcher was a member, has just confirmed that this orphan pediatric disease has its origin in the immune system. The discovery of researchers from the University of Montreal and the CHUM and CHU Sainte-Justine research centers gives some hope to the possibility of early diagnosis.

Rasmussen’s encephalitis, named after its discoverer, mainly affects children – a first attack occurs between 14 months and 14 years – and is resistant to the antiepileptic treatments normally associated with convulsions. The inflammation and deterioration of a hemisphere of the brain requires, as the main treatment, a removal of a part of the brain. This intervention reduces epileptic seizures and the spread of the disease to the other hemisphere of the brain.

“The cure is exceptional, because generally, the patients end up going out,” notes Lionel Carmant, neurologist and researcher at CHU mother-child Sainte-Justine.

This recent study, however, identifies the true cause of the disease. “We had no evidence of the autoimmune nature of Rasmussen’s disease. Our mouse model without immune system has confirmed this hypothesis, “says Elie Haddad, professor in the Department of Pediatrics at the University of Montreal and researcher at CHU Sainte-Justine. “The mouse could also become an avatar for screening the patient and even personalizing the treatment,” says Prat.

Not to mention that this could advance the search for new treatments and, if so, avoid surgery. One of the options considered is that of immunomodulators to reduce the advance of lesions to the brain and anti-inflammatory drugs to counter inflammation of the lateral zone. “We can imagine the same treatment as for multiple sclerosis – another autoimmune disease that attacks the central nervous system. If the mouse model reacts well, it could be tried on humans, “says Haddad.

Orphan pediatric disease

This rare disease – it affects at most two young Canadians each year – remains poorly understood, even though its first description dates back 60 years. “We never have enough patients to build a model. That’s why the mouse model helps us a lot in understanding this disease, “says Haddad. And funding for rare diseases is also more difficult.

A disease is classified as rare and orphan when it affects less than one person in 2000. There are about 7,000 diseases in this category worldwide – 75% of them affect children.

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