teen with deadly brain tumour has raised $ 80,000 for emergency surgery .
18-year-old jackson byrnes has stage four brain tumour .
he was told by doctors it was too aggressive to operate on .
instead he found a neurosurgeon who would do the operation .
he had to find $ 80,000 by tuesday night to pay the surgeon up front .
the risky operation will likely see him end up paralysed down his left side .