Los Angeles ? The 1-year-old Guatemalan twins born joined at the head and separated in a lengthy surgery opened their eyes and began moving Thursday, a doctor said.

Maria de Jesus Quiej Alvarez and sister Maria Teresa remained on breathing devices and in critical condition at the University of California Los Angeles Medical Center.

Nurse Michelle Murray, left, tends to formerly-conjoined Guatemalan twin Maria Teresa Quiej Alvarez after the infant was returned to the pediatric intensive care unit following a marathon 22-hour procedure to separate her from her twin.

Both have opened their eyes and move in response to stimulation, said Dr. Andy Madikians, head of pediatric intensive care at UCLA’s Mattel Children’s Hospital.

“I think what we’re seeing is what we expect to see at this point,” Madikians said.

Maria Teresa, who had nearly five additional hours of surgery because of blood on the brain, wasn’t moving as much as her sister, the doctor said.

Maria de Jesus was the first to show some movement. Earlier Thursday, the hospital said she fluttered her eyes after doctors took the twins off the paralyzing drugs they had been given to prevent coughing and other movement that could injure their brains.

“We remain cautiously optimistic about the long-term prospects of Maria Teresa and Maria de Jesus,” Madikians said. “There are still many medical hurdles to cross.”

The girls were born in rural Guatemala to Alba Leticia Alvarez, 23, and Wenceslao Quiej Lopez, a 21-year-old banana packer.

They were attached at the the skull and faced opposite directions. They shared bone and blood vessels but not brains. Cases like theirs happen in fewer than one in 2.5 million live births.