One of the Egyptian twins whose heads were delicately separated more than a year ago will undergo reconstructive surgery on Monday to help complete his skull, and his brother will have the same surgery in March, doctors said Thursday.

Ahmed and Mohamed Ibrahim (search), born joined at the tops of their heads, were separated at a Dallas hospital in October 2003 in a risky 34-hour procedure.

Ahmed will go first in the latest round of surgery.

The boys, now 3½, are walking and talking after months of rehabilitation, but they still wear helmets to protect their brains.

"Ahmed and Mohamed are ready for the critical phase of reconstructive surgery," Dr. Kenneth Salyer, a craniofacial surgeon, said Thursday at Medical City Children's (search).

Salyer's non-profit World Craniofacial Foundation (search) brought the twins to Dallas for the separation surgery, which was done at Children's Medical Center Dallas (search).

It will take each boy about 12 weeks after the reconstructive surgery to form the skull bone, Salyer said. Then, he said, they'll be ready to return to Egypt with their parents. The family has been living in a Dallas apartment.

Some of the boys' own cranial bone will be used in the regeneration process. The bone was stored in their thighs at the time of separation for use at this stage of their recovery.