Not My Left Leg: An Analysis of the Brain Structure of People with Xenomelia

The more complex the system, the more diverse the breakdowns. This applies to the human brain, in particular to his psyche. The number of mental disorders is really large, but not all of them are well understood. One of these puzzles is the syndrome of violation of the integrity of the perception of one’s own body (body integrity dysphoria or BID), when a person believes that some of his limbs does not belong to his body. Patients with this diagnosis sometimes behave as if "not their" limbs are not at all, and some are tempted to amputate an unwanted arm or leg. Today we will consider a study in which scientists tried to find a reflection of this ailment in the activity of the human brain. What exactly have scientists discovered, how serious are the changes in the structure of the brain,and how can the data help in the treatment of BID? We learn about this from the report of scientists. Go.

BID History

The syndrome of impaired perception of one’s own body was first described in 1977 by Gregg Furth and John Mani. In those days, this ailment was called "apotemophilia" and was attributed to sexual deviations. In 1986, John Mani described a new form of BID called "acrotomophilia", which manifests itself in the form of sexual arousal in response to the amputation of a partner.

For many years, BID and its variations were found in the scientific literature only in the form of descriptions of specific few cases. And only in 2004, Michael Furst published a clinical study that described 52 cases of this disorder. The worst thing is that a quarter of the patients interviewed by Ferst were able to achieve their terrible goal, that is, their unwanted limbs were amputated. It was First who proposed the term "body integrity identity disorder ", i.e. syndrome of impaired perception of one’s own body He believed that this ailment is much closer to a disturbance in perception than to paraphilia.

After this classification, the study of BID has moved from the field of psychiatry and sexology to neurology. One of the first neurological studies showed that patients with BID of both legs would prefer to amputate the left leg, which is consistent with damage to the right parietal lobe of the brain. Skin conduction studies have also been conducted that show significant differences above and below the line of desired amputation. At the same time, this line remains unchanged over time, and such desires in a person can appear even at an early age (from 8-12 years).

These data give at least some understanding of what is happening with the brain of a person suffering from BID. However, there is extremely little information to draw any intelligible conclusions. It is for this reason that a study was conducted, the results of which we will now consider.

Research results

Scientists note that we perceive our body in a framework clearly defined by biological and social norms. In people with BID, this framework is broken, which makes them want amputation. Having achieved what they want, they experience the so-called integrity, as if removing an unwanted limb makes them complete.

In terms of behavioral characteristics, there are two distinct features: erotic attraction to patients with amputation (usually lower extremities) and modeling of the desired state of the body using crutches or wheelchairs (ie “pretense”).

Researchers managed to assemble a group of subjects from 16 people (men) who, without exception, would like to amputate their left leg. It is curious that none of them had previously recorded any mental or neurological disorders.

The control group consisted of 16 absolutely healthy men with approximately the same education and age group.

The identification of differences in the functional and structural architecture of the brain between individuals with BID and the control group provided a unique opportunity to identify neural networks associated with the feeling of belonging to the limb as an integral part of the body. Moreover, this allowed us to identify the areas of the brain that underlie the satisfaction of a certain configuration of the body.

More specifically, in subjects with BID were investigated:

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Changes in functional coherence and gray matter concentration were associated with the subject's desire to amputate the limb and his own description of the reasons for such a need, which were carefully evaluated during a clinical interview.

In BID participants, compared with the control group, cortical nodes with reduced functional connectivity were represented by the following brain areas: right paracentral lobule (rPCL), right superior parietal lobe (rSPL), left lower frontal gyrus (lIFGOrb) and left lower temporal gyrus (lITG) .


Image 1: Cortical nodes of BID patients with reduced functional coherence.


Table No. 1: a decrease in the internal coherence of cortical nodes, atrophy and hypertrophy of brain regions of patients with BID.

Regions with a lower concentration of gray matter in patients with BID compared with the control group were: right superior parietal lobule (rSPL), left premotor cortex (lPMv) and lower frontal gyrus (lFGOrb).


Image No. 2: atrophy and hypertrophy of brain regions of patients with BID.

The gray matter concentration in rSPL negatively correlates with the strength of amputation (Pearson correlation coefficient; r (14) = 0.51; p = 0.01) and mock behavior (Pearson correlation coefficient; r (14) = 0.62; p = 0.01).

The rPCL region, which contains the primary somatosensory representation of the left leg (which they most often want to amputate), showed a reduced internal functional connection with other cortical areas. Remarkably, no structural changes were detected in rPCL. In other words, tactile and motor functions were not impaired.

rSPL showed both reduced internal functional coherence and gray matter concentration. Scientists emphasize that the absence of any violations and symptoms of BID relative to the right leg indicates the specificity of changes in the brain.

The results of the analysis fully confirm the theory that rejection of a limb in people with BID results from a mismatch between the preserved projections of somatosensory inputs from the limb and the primary cortical areas of the brain. Thus, the primary idea of ​​your own is violated at the highest level of integration. Simply put, the brain of patients with BID does not perceive the unwanted limb as part of a holistic image of the whole body; in the rSPL region, it was previously identified as a critical center for the formation of this image.

These conclusions were confirmed in practice: tactile stimulation of the unwanted limb was accompanied by reduced activation of rSPL. A morphological study also revealed a decrease in rSPL thickness in patients with BID.

The image of your own body is formed as a result of the joint work of several sensory subsystems: visual, tactile, proprioceptive, vestibular and reafferent motor signals.

In addition, it is believed that the image of the body is supported by the work of distributed neural networks, the integrity of which is responsible for the perception by a person of his body as a connected and unitary one.

For example, lPMv combines visual and tactile information about a limb through its anatomical connections with the frontoparietal region. In patients with BID, the central region of multisensory integration (lPMv) was atrophied. In addition, BOLD activity (depending on the level of oxygen in the blood) of lPMv at the moment of touching an undesirable limb was reduced by about 5 times.

It is believed that the body image formed by rSPL is genetically determined. Confirmation of this theory is the phenomenon of phantom pain. When a person with an amputated limb imagines its movement, it is rSPL that is activated in the brain, while other sensory or motor areas remain inactive.

An additional confirmation of the importance of rSPL in the problem of the syndrome of impaired perception of one’s own body is the fact that the stronger the atrophied rSPL, the greater the desire for amputation.

Scientists also note that the development of BID in humans does not proceed quickly. The first signs of the syndrome can be replaced at an early age, which is associated with an inborn individual way of your own body. There is a theory in which the individual image of the human body depends on the cortical template embedded in rSPL. Such a pattern will form bonds within the limbic system. Therefore, the presence of irregularities in the pattern leads to the development of BID and the desire to amputate any limb in order to comply with this pattern.

For a more detailed acquaintance with the nuances of the study, I recommend that you look into the report of scientists .

Epilogue

Any mental disorder is a heavy burden both for the patient himself and for the people around him. A more detailed study of the causes of the disease, the mechanisms of its work and methods for its suppression / treatment are as important as, and the understanding that all these problems have a common source - the brain.

In the work we examined today, scientists were able to fully prove that people with a syndrome of impaired integrity of their own body perception (BID) are not some kind of perverts, but hostages of their own brain, which provides them with a body image that they do not correspond to. Impaired functioning of certain parts of the brain (to a large extent rSPL) leads to rejection of one's own healthy limb, to the perception of it as superfluous, not its own, alien. The desire to amputate a leg or arm in patients with BID can be so strong and irresistible that they are ready to perform amputation on their own. It is not necessary to say how terrible it is and, among other things, it is extremely life threatening.

The problem with most mental disorders is the lack of attention on the part of the scientific community. Not all diseases are equally “interesting” for scientists, no matter how cynical it sounds. Nevertheless, if you pay enough attention to the search for the causes of certain disorders, you will understand how to treat them or even how to prevent them.

It is also worth noting that an impressive part of the work in the fight against mental disorder is performed by the relatives and friends of the patient. The primary task is to contact specialists in a timely manner. And in case of revealing an ailment, it is necessary to show maximum understanding and patience. Of course, it’s not in the laboratory to sit above the microscope in search of answers to the riddles of the brain, but it is also a hard and responsible work. The consolidation of efforts on the part of physicians, scientists, and those around the sick people can do real miracles. In any case, no matter what problem a person faces in his life's journey, whether it be some kind of illness or a domestic turmoil, it is always easier to overcome it when you know that there are those who are simply not indifferent to you.

Thank you for your attention, stay curious, and have a great weekend, guys.

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