Little Nicole Black from Portadown died two days after she had hurt herself while playing in the garden of a friend's house on June 12, 2006.

After her death, Nicole's heart was donated to save the life of four-year-old Londonderry boy Paul Donnelly, who had been suffering from dilated cardiomyopathy - an incurable enlargement of the heart.

Initially, it was thought that some form of trauma might have led to Nicole's death.

Those who tended to the distressed youngster immediately afterwards noticed that she had a small cut at her left eye which became swollen.

Nicole, from Corbrackey Road, complained of feeling sick and was taken to Craigavon Area Hospital but was later transferred to the Royal Hospital for Sick Children in Belfast, where she died two days later.

Nicole's cause of death was initially given as cerebral oedema, or swelling of the brain, due to trauma.

At an inquest yesterday in Craigavon Courthouse, none of the witnesses before Coroner John Leckey, was able to explain how exactly Nicole had hurt herself. The inquest heard that when asked about what she may have done at the time, Nicole had repeatedly said, "I don't want to talk about it" .

The inquest heard an extract from a report by Mr Peter Richards, a consultant neurosurgeon from the John Radcliffe Hospital in Oxford which highlighted the rare veins disorder Arteriovenous malformation (AVM) .

Mr Leckey said that although Mr Richards was unable to identify with certainty the underlying reason for the cerebral oedema, he accepted "on the balance of probabilities" Mr Richards' opinion that "a low-level fall as is speculated happened in Nicole's case would not be expected to cause her death from massive intra-cerebral haemorrhage".

Mr Leckey went on to quote from Mr Richards' report that: "If she had suffered a severe primary head injury from an event ... I would not have expected her to have been talking and walking immediately following the injury. I therefore consider it likely that some other event has led to her haemorrhage and I would speculate that a small arteriovenous malformation has ruptured coincidentally and in the process destroyed itself, such that no trace of it is identifiable on pathological examination."

Mr Leckey said that he was not sufficiently confident that trauma was the underlying reason for the oedema, and ruled that the cause of death had been from cerebral oedema, with a secondary cause of death of subdural and sub-arachnoid haemorrhage.

Mr Leckey also paid tribute to Nicole's family for allowing her organs to be donated. Four people, including young Paul, were among those who were helped following her death. Such was the gratitude of Paul's mother, Bella, that she named her daughter Nicole in tribute when she was born in September, just a few months later.

Speaking after the inquest, Nicole's mother, Barbara, told of her relief at the findings.

"I definitely came out of (the inquest) feeling better. We went in wondering if we were going to get any answers at all, and we did," she said.

AVM is described as "a tangle of abnormal blood vessels", which is not inherited or infectious. It can occur anywhere in the body, with brain AVMs considered rare and affecting less than 1% of the population.