joi, 19 septembrie 2013

The story of Abby and Brittany Hensel, a medical mistery

Abby and Brittany were born a little bit different than us. The story about the two girls held together for life by flesh isn't a new one. Born as conjoined twins, they shared one body. This is a very rare phenomenon and the chanches of surviving the first 24 hour of their lives were 1 in 30 milion. But sometimes nature decides to give us a surprise and the twins did indeed survive not only the first 24 hour of their lives but a full childhood and adolescence.

There were many articles about Abbigalil and Brittany in their early childhood. They parents were very protectie so few pictures were taken and little was known about the natural improbability that actually happened. After a more or less normal infancy the girls were ready to show their story to the world. A documentary was made and after that they had their very own reality show named "Joined for life", and joined for life indeed they were, but the question we will probabily never have an answer to is how? 

How can these girls be what they are today? These are the questions many phisicians have posed since Abby and Brit were born. Parents didn't want us to know or to understand how,so we can only speculate on the complex anatomy that glued these two people together into one conjoined life. 
In the picture you can see that their unique body has two hearts and two sets of lungs in one rib cage. The cariovascular system of their body is astoneshing. There is no mammal on this planet that has something like that. How do their hearts work? Do they have one aorta that splits to both hearts, do they have two that fuse at some point? Are the limbs and the heads irigated by the heart on their side or do the hearts work together? What happens if one heart stops? Not only we do not know the answers of these questions but more importantly we cannot understand if they are two or one.

One of the most interesting things about their individuality is that each girl controls the arm and leg on her side of the body and they cannot feel the other's side. Despite these aspects the twins can synchronize their movements extremely well and they developed a complex psychological bond that allows them to finish each other's sentences. While writing an e-mail with both hands there is little comunication between the girls. Brittany admits "While we're YM-ing or writing e-mails we normally say -I am- not -we are-, I don't know why". Scientists all over the world are eager to determine through brain and nervous sistem imaging techniques their sense of space and movement, how do they react to the other's gestures. These things are now possible with brain scans that detect subtle alterations in the blood flow or in the brain metabolism but the parents and the girls don't want their lives to be anything than normal. 

But what actually is normal with these girls? Doctors say these special nervous connections that allow them to be so in sync with each other have occured very early after conception. The nervous system will have been developing only a few weeks later and this specific one involved connections that don't normally occur in normal people. You can't have motor fibers going down one spine and up the other, at least we shouldn't be able to. Each normal brain has two hemispheres, a right one and a left one and each hepisphere controls the opposite side of the body. These girls have only one body and normally four hemispheres so how does that work? Being a huge fan of speculation myself, I would say that even if they cannot feel the others touch, there are more complex spacial maps in their brains that allow them to know where the other limb is situated. 

I think that some of you may be familiar with the term Phantom Limb syndrome. The Phantom Limb sindrome is the sensation 60 to 80 % of amputee pacients feel after having one limb removed. The sensation is often as if the missing limb is still there and it may cause severe frustration to the individual and pain where the leg should have been. First scientists tought that the pain was caused by the nerve endings that were severed in the surgery and were sending signals that the brain interpreted as pain. Surgeons usually operated again to cut and remove the severed inflamated nerve endings but it only made it worse.
Ronald Melzack wrote that the experience of the body is made by a wide network of interconnecting neural structures. Tim Pons and his coleagues from the National Institute of Health showed that the primary somatosensory cortex undergoes massive reorganisation after loss of sensory imput. To make it simpler, the wires get mixed up in your head and the brain doesn't know which are which so you feel strokes that are on other parts of your body on your missing limb like it's still there.

I told you that part to help you uderstand my speculation. Even if their brains are wired differently than ours, the major rules that make us work still apply to them. So if the somatosensory cortex is in charge with all the information nerves send from the body to the brain, after Abby and Brittany were conceived and the nervous system started to form, each of their brains adapted to only one side but each somatosensory cortex (situated in the postcentral gyrus of each brain) received imput from both sides therefore giving the girls the possibility of having almost the coorination of a normal human being.

We also have to understand that they have grown up together and although they had two heads, they did the work of one human. Even if each mind can think for itself they were constructed to also think for each other. Indeed their individuality was affected but their quality of life is much greater by not separating them. We will always wonder how can they be the way they are and we can always speculate but maybe one day this medical mistery will be solved and we will understand how they ca be at the same time two people and one.

Thenk you for reading. The information for this post was taken form Wikipedia and the documentary "The Twins who Share a Body-My shocking story"

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