Surgeons were pleased with the recovery so far of 2-year-old Egyptian twins whose fused heads were surgically separated over the weekend, but cautioned that there are still several concerns, including long-term questions about brain damage.

A day after the completion of a 34-hour surgery to separate the two, who were born joined at the top of their heads, Dr. James Thomas, chief of critical care at Children's Medical Center Dallas (search), said Monday that they both were recovering well. The boys remained in critical but stable condition Tuesday morning.

The operation to separate Ahmed and Mohamed Ibrahim (search) began Saturday morning and ended Sunday afternoon, after which they spent their first-ever night apart.

"The neurosurgical team is pleased so far," Thomas said. "But this is really an hour-to-hour, almost moment-to-moment thing right now."

Concerns include the possibility of stroke, infection and how the wounds will heal.

"The longer that you go without the appearance of complications, that's always taken as a positive sign," Thomas said. "But to let your guard down I think would be a mistake. After coming back from the operating room last night the twins have had a remarkably stable course."

Brain scans Monday morning showed no hemorrhaging and minimal brain swelling.

The boys, who shared an intricate connection of blood vessels but have separate brains, were in drug-induced comas to minimize the risk of brain swelling. They were expected to stay that way for the next two or three days, Thomas said.

The boys' father, Ibrahim Mohammed Ibrahim, fainted when told that his sons had been separated.