Two-year-old conjoined twins connected above the nape of their necks were successfully separated in an Italian hospital. The Ospedale Pediatrico Bambino Gesù (Baby Jesus Pediatric Hospital) in Rome said the case is believed to be the first successful operation of its kind.

Ervina and Prefina were born with a condition described Tuesday as “one of the rarest and most complex forms of cranial and cerebral fusion,” according to Agence France-Presse. The hospital said it was the first time in Italy and likely the world that surgeons were able to separate twins who shared the back of their skull and its venous system.

The two sisters were brought to Italy in September 2018 from Bangui, Central African Republic. Medical tests showed the girls to be generally in good health. But, one sister’s heart was working harder to maintain the “physiological balance of the organs of both, including the brain,” AFP reported.

The hospital said that doctors faced the greatest challenge due to the shared network of blood vessels bringing blood from the girls’ brains to their hearts. That required “three very delicate operations to progressively reconstruct two independent venous systems,” it added.

Representational image of a surgery. Image by skeeze from Pixabay

On June 5, the twins underwent the final operation, which took 18 hours and included 30 doctors and nurses. Doctors worked to divide the bones of the shared skull followed by a reconstruction of the membrane covering the two brains and recreating the skin lining over the girls’ new skulls.

“A month after the final separation, the twins are fine,” the hospital said, along with a video of a party it threw on June 29 for their second birthday.

The hospital said the girls would have to wear protective helmets for a few months due to the ongoing risk of infection. Doctors believe the children will have the opportunity to “lead a normal life, like all girls of their age.”

Twins conjoined by the skull are extremely rare, or approximately one case every 2.5 million live births, the hospital said.