Connecticut chimpanzee attack victim Charla Nash got a full face and hand transplant late last month in a 20-hour surgery. The prerequisites of a full face transplant surgery are the availability of a suitable donor with blood and tissues matching the patient’s and the physical and psychological health of the patient.

According to the Guardian, the world's first full face transplant surgery was made in 2005 in the case of Isabelle Dinoire, a French woman who received the first transplant having been mauled by a dog.

And since then there have been many successful face transplants. In 2009, a woman who had lost her nose, cheeks, roof of her mouth and parts of eye in a shotgun attack got a full face transplant. After a day-long surgery at the Cleveland Clinic in Ohio, she got back about 80 percent of her face.

Five months on from the transplant, she is eating and enjoying the taste of pizzas and hamburgers again, she drinks from a cup, breathes for herself, has regained the sense of smell. Her chronic pain has been reduced, the report said.

Last month, 26-year-old Dallas Wiens of Texas, who had previously come to terms with a vastly deformative injury which virtually erased his face, made his first public appearance after getting a full facial transplant.

HOW FACE TRANSPLANT WORKS

Sophisticated surgery can stitch together bones, muscles, nerves and skin from a suitable donor on the patient's face. Quite a few full face transplant surgeries have taken place recently, offering a second life to many people who lose their facial identity in macabre accidents, fires and animal attacks.

Full face transplant is the culmination of a long series of experiments, starting with facial reattachment an then partial face transplants.

According to howstuffworks.com, French doctors performed a third partial face transplant on a 29-year-old man with neurofibromatosis, a disease that causes tumors to grow on nerves throughout the body.

These successes led doctors into the experimenting full face transplant surgeries on patients who had lost their entire face, scalp and hair.

The prerequisites of a full face transplant surgery are the availability of a suitable donor with blood and tissues matching the patient’s and the physical and psychological health of the patient.

After the suitable donor is found, it is necessary that the donor is kept on lie support so that tissues are connected to an active blood source. But the donor should be brain dead with no hope of recovery.

Doctors use a test called HLA typing, which looks for proteins called antigens on the surface of tissues to find a good match, the article says. The closer the antigens match, the less likely that the recipient will reject the transplanted tissue.

The first surgical process is cutting and peeling away the donor's face. By then another team of doctors will have removed the remaining facial tissues from the recipient’s face. And then, using microscopic needles and thread, surgeons connect arteries and veins to the new tissue to supply it with the oxygen-rich blood it needs to live.

However, according to the article, they don't need to connect all of the arteries and veins as just a few will ensure that enough blood flows to the face. The surgeons will also connect the nerves and muscles so that the patient has feeling and movement in his or her face. Doctors will drape the donor's face over the recipient's skull, adjust it to fit and sew it into place. The recipient will have to take immunosuppressant drugs for the rest of his or her life to prevent tissue rejection.

RISKS

Rejection is the biggest risk. The face is coming from another person, and hence even if the tissue types closely match there is a high chance o rejection. The drugs used to prevent rejection work to reduce the patient's immune system, making the patient vulnerable to many diseases in future.

People who take immunosuppressive drugs are more likely to develop diabetes, kidney disease, infections and cancer.