The two-year-old Egyptian twins who were separated during major surgery have reacted differently as doctors wean them off coma-inducing drugs.
Father Ibrahim Mohammed Ibrahim with his sons before surgery
Mohamed Ibrahim came off the drugs on Wednesday, and was said to have shown some movement on one side of his body and was breathing spontaneously over a mechanical respirator.
His brother Ahmed had minor seizures during the night prompting doctors to keep him in his coma for a while longer.
Doctors said both boys continue to do well following the 34-hour operation last weekend to separate them at the crown of their heads.
"They are doing extremely well. This is remarkable," said Dr Jim Thomas, head of critical care at the Children's Medical Center in Dallas.
They had been kept in a coma following the operation to reduce the risk of brain swelling.
He said both boys had had several drains removed and were taken off blood pressure medications.
They had a slight fever on Wednesday, which soon abated and antibiotics were stopped as planned.
The goal on Thursday was to decrease Mohamed's ventilator support and to bring Ahmed's drug-induced coma to an end.
Dr Thomas said the twins' parents were also being encouraged to touch and talk to them.
"We tell them that they probably hear. They may not remember, but they're hearing," he said.
It may take a number of days for the twins to become fully conscious.
Born by Caesarean section in Qus, Egypt, 2 June 2001
Arrive in Dallas in 2002
World Craniofacial Foundation funds their trip
Tissue expanders inserted under skin in April 2003 to prepare for reconstruction
34-hour operation carried out 11-12 October
Well-wishers flood hospital with messages
Dr Thomas said tests on their brains and circulatory systems had not shown any problems, but it may be weeks before doctors can fully determine their levels of function.
The twins' family - from southern Egypt - decided to go ahead with the operation, knowing there was a risk of brain damage or death to one or both the boys.
They said it was the only chance they had of a normal life.
The boys had trouble closing their eyes, moving their necks and swallowing.
They could not stand on their own and would have faced progressive loss of functions had they remained as they were.
After they were separated, the boys' wounds were covered with skin and tissue created by skin expanders put in their thighs and heads about five months ago.
They face years of reconstructive surgery.