The parents of a three-year-old who suffered a debilitating stroke hope new tests can shed some light on why he was struck down.

Jacob Jackson suffered a rare childhood stroke just two weeks before his third birthday.

It left him paralysed down one side, unconscious and unable to speak for six days.

Next week he will attend Leeds General Infirmary with parents Liz, 25, and Garry, 35, to undergo an MRI brain scan.

"He had a scan after the stroke, but his brain was pebble-dashed with blood clots and it was difficult to see what had actually happened to it," said Liz. "This time he will have to be knocked out, which is terrifying.

"I am dreading it - the whole thing is just awful and still totally unbelievable. Hopefully the blood clots will have gone now and doctors can look at what damage has occurred."

Brave Jacob also faces a heart operation in the near future. "Doctors are trying to find out what caused the stroke because all the tests have drawn a blank so far," said Liz, of Cornmill Drive. Liversedge.

"The heart operation will be an angiogram where a probe is inserted into his body to take photographs of his heart. They will investigate whether there is damage to the arteries, valves or tissues in his heart.''

Jacob was born weighing 9lb 10oz and before the stroke, was an ordinary little boy. When it happened in June, Liz was in the garden playing with him and his four-year-old sister, Molly. She noticed Jacob's mouth was hanging down, he had lost his speech and began to fit.

His body was also lopsided and his neck was floppy. He was rushed to Dewsbury District Hospital where tests ruled out meningitis, an allergic reaction or a tumour.

"Doctors believe 150 to 200 children in the UK suffer strokes every year, but in 20 per cent of cases of childhood strokes, the cause of the stroke is never established," said Liz.

"Jacob is still very weak down his right-hand side and has terrible mood swings. It is bound to change him and he gets frustrated by not being able to use his hand. He is having to learn to write again with his left hand."

Jacob now has speech therapy, occupational therapy, physiotherapy and play therapy. "They have to work on his concentration. He shouts and screams a lot because he knows people will take notice.

"It seems like a really freak thing. At least if he had suffered a head injury, we would have known why it had happened, but this is just a mystery."