Canadian researchers say they have developed a treatment for a rare and potentially deadly inflammatory disease that causes severe neurological effects in children, but is often misdiagnosed.

Researchers at the Hospital for Sick Children say immunosuppressive therapy appears to alleviate the symptoms of small vessel vasculitis of the central nervous system, a disorder that can be mistaken for conditions ranging from epilepsy or multiple sclerosis to atypical autism.

Children with small vessel vasculitis can exhibit a wide array of symptoms including headaches, nausea, seizures, hallucinations or memory and behavioural problems, and their condition deteriorates as they go untreated.

Scientists have discovered that the condition is almost entirely reversible if it is caught and treated quickly. But unlike medium-large vessel vasculitis, which can be diagnosed via angiography because it affects larger arteries, small vessel vasculitis is confirmed after a biopsy of the brain.

In a study of 19 children positively diagnosed with the disorder, more than 70 per cent returned to normal after receiving six months of immunosuppressive drugs and another 18 months of maintenance therapy to reduce inflammation and increase blood flow to the brain.

Researcher Dr. Susanne Benseler says doctors should ask themselves: "When a perfectly healthy child presents with a new neurological problem, seizures, movement disorders, could this possibly be an inflammation or irritation of the blood vessels of the brain?"

"Because the impact is this is a reversible condition," Benseler told CTV News.

The findings were published in the medical journal Lancet Neurology.

Heather Loftus is back in dance class after fully recovering from small vessel vasculitis. Five years ago, Loftus fell ill around Christmas, suffering from headaches and vomiting. She became so sick doctors had to put her in a coma.

"At the time I was scared because I didn't know if I was going to live or die," said Loftus, who was six years old when she first got sick.

Loftus was tested for encephalitis, meningitis and other illnesses but doctors were failing to confirm a diagnosis.

"They came into the ICU with a social worker basically to get us to start planning for her funeral," Loftus's mother, Margaret, told CTV News.

After five weeks, doctors finally discovered an unusual inflammation of the blood vessels in her brain.

Once doctors began treating Heather with immunosuppressive drugs, "every day, every hour, it seemed like she was doing something that would indicate that she was getting better and better," her mother said. "The actual recovery was amazingly fast, once it started to happen."

Since starting the new program to test and treat children at Sick Kids, Benseler and her colleagues have found hundreds of children suffering from brain inflammation.

And she hopes her study will give doctors around the world the tools to detect and treat small vessel vasculitis.

"Children still die of inflammation of the blood vessels of the brain, and that is something I think we can change," Benseler said. "Awareness is the key."

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip