Specialists in France have ruled out neurological problems as the cause of the symptoms that saw Simon Best admitted to hospital last night and subsequently ruled out of the remainder of Ireland's World Cup campaign.

The prop was brought to hospital in Bordeaux after he developed a loss of sensation on his right side, as well as a headache and a difficulty in speaking.  Tests carried out this morning have led doctors to believe that the cause of the symptoms is a cardiac issue.

His symptoms are now said to be resolved and he has been joined at the Haut Levque Hospital by his wife Katie, who arrived in Bordeaux today.  He is expected to return to Ireland within 48 hours.

"This is very positive news for Simon and we will all continue to monitor his progress carefully. The care he has received so far has been excellent and team doctor Dr. Gary O'Driscoll has been with him throughout this," said coach Eddie O'Sullivan, who today called Munster prop Tony Buckley into the squad as cover for the Ulsterman.

O'Sullivan has opted to start Jerry Flannery at hooker against Argentina on Sunday, after he came through a fitness test this afternoon.  Flannery was floored by Best in training earlier in the week and took a few days to overcome the "shoulder stinger".

Fellow hooker and the other half of the Best brothers, Rory, also passed a fitness test but is named on the bench. O'Sullivan said this afternoon that the decision was not influenced by Simon's illness.

"We have named Rory Best on the bench for this weekend and while we did consider his brother Simons condition when making that decision, Rory is an incredibly mentally tough individual and was adamant that he wanted to be considered for selection. We have no doubts that he will be ready if called upon."

The squad's media commitments were cancelled for the day, due to Best's condition.