"I have attempted to break my back, but I missed. I need to be paraplegic, paralysed from the waist down."

Sean O’Connor is a very rational man. But he also tried, unsuccessfully, to sever his spine, and still feels a need to be paralysed.

Sean has body integrity identity disorder (BIID), which causes him to feel that his limbs just don’t belong to his body.

Sean’s legs function correctly and he has full sensation in them, but they feel disconnected from him. “I don’t hate my limbs – they just feel wrong,” he says. “I’m aware that they are as nature designed them to be, but there is an intense discomfort at being able to feel my legs and move them.”

The cause of his disorder has yet to be pinpointed, but it almost certainly stems from a problem in the early development of his brain. “My earliest memories of feeling I should be paralysed go back to when I was 4 or 5 years old,” says Sean.

The first case of BIID was reported in the 18th century, when a French surgeon was held at gunpoint by an Englishman who demanded that one of his legs be removed. The surgeon, against his will, performed the operation. Later, he received a handsome payment from the Englishman, with an accompanying letter of thanks for removing “a limb which put an invincible obstacle to my happiness” (Experimental Brain Research).

We now think that there are at least two forms of BIID. In one, people wish that part of their body were paralysed. Another form causes people to want to have a limb removed. BIID doesn’t have to affect limbs either – there have been anecdotal accounts of people wishing they were blind or deaf.

DIY operations

There are many reported cases of people with BIID attempting to break their back, like Sean, or perform a DIY operation to alleviate their discomfort. Some even pay for surgeons to amputate their healthy limbs. Now the first study of this desperate form of treatment, by Peter Brugger at the University of Zurich, Switzerland, and colleagues, suggests that chopping off a healthy limb “cures” people of this form of BIID. Brugger says they interviewed about 20 people with BIID, many of whom have had an illegal amputation. All said they were satisfied with the outcome.

But the findings, so far unpublished, are tentative and do not justify such a treatment, says Brugger. “We don’t have enough scientific evidence to propose amputation or paralysis. Before we have an understanding of something, we can’t think of developing a treatment.”

Brugger disagrees with the suggestion that the disorder is psychological. “The neurological side of the data is too convincing,” he says. “Why would a vague desire to be handicapped show itself as a precise need to be amputated two centimetres above the knee, for example? I certainly think it’s more a representational deficit in the brain in all cases, than a psychological need for attention.”

The parietal lobe, situated at the top of the brain, is almost certainly involved. It is here that a complex set of brain networks enable us to attach a sense of self to our limbs. In 2011, V. S. Ramachandran, at the University of California, San Diego, and his colleagues examined the brain activity of four people with BIID.

Confusion in the brain

They found significantly reduced activation in the right superior parietal lobe when researchers touched the part of the leg that people wanted amputated, compared with when they touched the part people wanted to keep. The researchers say that this area of the brain is key to creating a “coherent sense of having a body” (Journal of Neurological Neurosurgery and Psychiatry).

The brain hates to be confused, says Ramachandran. So when people with BIID feel the sensation of touch, they can’t incorporate this message into the regions of the brain that identify the limb as being part of themselves. In an attempt to remove the confusion, it seems the brain rejects the limb altogether.

Brugger hypothesises that some people are born with a relative weakness in brain networks which enable us to accept all our limbs as our own. This is usually naturally corrected as they grow up, he says, but in some people, the sight of an amputee at a very young age may have reinforce the alterations in the brain. About half of people with BIID – itself a condition so rare there aren’t proper estimates of its prevalence – recall having a fascination or close relationship with an amputee while they were a child.

Would Sean contemplate having his limbs amputated? “I would, if it was available,” he says, “but there are no surgeons currently offering the treatment openly.”

"But I am who and what I am in part because of having BIID and my lived experiences. Take away BIID, and I will be a different person. Not necessarily better, nor worse, but different. But the idea of making all my pain go away? It’s definitely appealing."