Erik Ortiz Cruz suffers up to 30 epileptic fits a day and surgery is the only solution to his condition.
The boy's family have been unable to meet massive hospital bills with each test carried out costing around £5,020 (6,000 euros) and surgery likely to run to £50,240 (60,000 euros).
Incredible: Cristiano Ronaldo has paid over £50,000 for the operation for 10-month old Erik Ortiz Cruz
Money to a good cause: Erik Ortiz Cruz and his mother in hospital together
Care: Erik was born with a neurological disorder and he desperately needed the operation
The player was at first asked to donate boots and a shirt to a fund-raising auction but decided to go the extra mile and foot the bill.
Earlier in the year Ronaldo celebrated his Ballon D’Or win with children suffering from Leukaemia keeping a promise made on Spanish radio last year.
Ronaldo met the children on radio Cope show Partido de la 12 in November and said if he won he would celebrate with them.
Following the celebrations he spoke to one of the children - who will have an operation this month - and told the youngster: 'Don't worry I have not forgotten'.
Donating: The Portuguese star is well known for helping charitable causes
Success: Erik is just 10 months old but may now get all the treatment he needs
Promise: Ronaldo said that he would celebrate with children who have Leukaemia if he won the Ballon d'Or