More than 90 per cent of the overall bill came from dealing with the canisters of laughing gas, a major headache for authorities in the last few years.

"Unscrupulous vendors are supplying them. But they're dicing with young people's lives," said Dublin City councillor Danny Byrne

A study published in the American Journal of Neuroradiology was led by a consultant neuroradiologist at Beaumont Hospital in Dublin, Seamus Looby.