A woman in the state of Indiana in United States was shocked when she was told by her doctor that an embryonic twin was removed from her brain, as against what they thought was a tumor.

Embryonic development is the series of changes an embryo undergoes as it grows toward a mature organism.  Generally, in humans this stage of embryonic development is from up to about eight weeks where the baby is then called a fetus.

Yamini Karanam, a Ph.D student at the Indiana University, said since September 2015, she had been having difficulties comprehending what she read.

"Problems with reading comprehension, listening comprehension. If a couple people were talking in a room, I wouldn't understand what was happening," Karanam told NBC4 News on Tuesday, April 21.

The 26-year-old said she became more frustrated when her doctors gave her conflicting reports about what was wrong with her. But her research led her to Dr. Hrayr Shahinian at the Skullbase Institute in Los Angeles, where her rare case was uncovered.

"Unlike traditional brain surgery where you open the skull and use metal retractors and you bring a microscope to see in the depths of the brain, what we're doing is keyhole surgery," Shahinian said.

The method uses fiber-optic technology with digital imagery. A half-inch incision into the brain allows for an endoscope to reach in and slowly and very delicately chisel away at the tumor.

After the surgery, Karanam was relieved that what had troubled her for many years was finally gone. She referred to the ‘twin’ as the "evil twin sister who's been torturing me for the past 26 years."

According to the doctor, Karanam is expected to make full recovery in three weeks.

The case has been described as a rarity in modern medicine, with the twin having complete bone, hair and teeth.