Undeveloped twin removed from girl's skull

Doctors have surgically removed the fetus of a twin from the head of its sister aged one year in China which, according to doctors, had developed upper limbs, bones and fingernails — the condition medically called fetus-in-fetu.

Doctors have also maintained that this fetus has been likely growing for months inside the womb with its sibling. And it has the ability to grow further.

It is a medical rarity, which has been encountered several times by doctors throughout the world.

The four inches long fetus was identified when the parents took their daughter for her neurological problems and an enlarged head.

The fetus was recorded in December in the journal Neurology of the American Academy of Neurology which noted that a girl was brought to the hospital for abnormalities in her motor skills — problems with walking and sitting.

The doctors from the hospital did not provide further details regarding this condition. The CT scans have revealed her sibling that was seen pressed with the girl’s brain.

According to the available details, the girl also had a fluid inside her brain which resulted in her head's enlargement, with a possibility of causing seizures and extreme sleepiness.

The fetus survived due to the blood supply shared with the host. The long-term complications for the girl cannot be foretold at this point, the details show.

Dr Zongze Li, a neurologist at Huashan Hospital — who treated this abnormality — believed "this condition is caused by unseparated blastocysts."

He also said that "the conjoined parts develop into the fore-brain of the host fetus and envelop the other embryo during neural plate folding."

It is the 18th reported case of this kind to date. In 2017, doctors in Thailand had found three siblings inside the skull of an unborn baby that had well-developed organs, including a nervous, digestive and respiratory system.

The fetus were connected by a single artery and vein which according to doctors had been "the umbilical cord".

Similarly, doctors came across an unborn fetus inside the scrotal sac of its male twin, in China in the year 2015.

The fetus was also removed by surgery from the host, and the host made a full recovery.

Moreover, fetus had also been detected in other parts of the hosts' body such as in the pelvis, mouth and intestines. 200 cases have been registered of which 18 were seen developed inside the skull.

Currently, doctors have not been able to identify how this condition occurs, however, it is known that it is caused by the incomplete separation of one egg. Some experts suggest "it happens as a result of late cell division."