Ten-month-old Manar Magid had the operation because she developed hydrocephalus, a condition in which fluid accumulates in the cerebral ventricles causing convulsions and an enlargement of the skull, one of her doctors said on Sunday.
A valve was planted in her brain in a one-hour operation on Friday that managed to stop her convulsions, Nasif Hifnawy, head of paediatrics at Benha Children's hospital north of Cairo, said.
"Manar's case is now stable with normal heartbeat, blood pressure, enzyme level and reflex actions," he added.
She remains in intensive care at the hospital but doctors expect to remove her from a ventilator on Monday or Tuesday.
Doctors have said Manar's case is extremely rare and her survival of the operation was a big achievement in itself.
She was born attached skull-to-skull to the head of an undeveloped twin, a very rare birth defect known as craniopagus parasiticus.
The condition occurs when an embryo begins to split into identical twins but does not complete the process.