Phantom Limbs: Ghosts of Amputated Body Parts!

 Can you imagine having one your your arms or legs amputated? The horror of losing a body part probably stays with you forever. Amputations are not done for fun, though. Its usually to save someone's life. But how scary must it be to wake up one morning thinking "Wow my leg really hurts! I wonder what's wrong with- Darn it! I forgot! I don't have a leg!"
 This is the phenomenon of Phantom Limb Syndrome. Almost all amputees report feeling pain or other sensations in the limb that has been amputated. Scientists used to think that this was due to damaged nerve endings in the stump sending weird signals to the brain. They used to amputate more of the stump in order to remove the damaged nerves. This, as we now know, would not help the patients. In fact, it would cause more phantom limb pains!! Phantom Limb Syndrome is actually due to the rewiring of the brain's somatosensory cortex. Since the person no longer has a certain limb, all the space in the brain dedicated to that limb is now a waste. So, the brain rewires that area to correspond to another body part. The homunculus is a representation of the post-central gyrus and the are of the body that it receives sensory information from.

 An individual who has lost their arm, usually has the hand area taken over by the face area. Someone who has lost a leg sometimes has the leg area taken over by the genital area! Because of this, if someone felt a sensation on their face, for example,  they would also feel it on their phantom arm. This video explains the phenomenon of phantom limb syndrome very clearly. 

Phantom pain can also occur in people who were born without a certain limb. This is because the nerves that would usually innervate the missing limb cause pain. 

 There are many treatments for phantom limb syndrome including medication and therapy. One treatment that is very interesting is the mirror box treatment developed by V.S. Ramachandran. It involves having the patient sit next to a mirror with the amputated stump hidden from view. The limb on the other side is seen in the mirror and looks like the patient has both limbs. The patient moves the limb and in the mirror it looks like both limbs are moving. This can help the patient reposition the phantom limb in less painful positions, or unclench. 

 This video shows that phantom sensations can be induced in people who haven't had amputations. This is more of an illusion than the actual rewiring of the brain that happens in phantom limb syndrome but it produces similar effects. 

Addiction

I would say I’m addicted to watching TV, reading, and eating chocolate (which I’m doing right now). Lots of people say they’re addicted to things, but are they really? Addiction is when you do something that’s pleasurable, but you do it so much that you develop a compulsive need to continue doing it. It interferes with your normal life. The most common addictions are to drugs and alcohol, but people can become addicted to other activities like gambling and video games too.

The actual biological state of addiction is when a person’s body has adapted to the presence of a drug so much that the body can’t handle being without it. There’s also a behavioral perspective, where people are dependent on something to cope with daily life. There are actually stages of addiction. The first stage is dependence, where the person spends most of his time looking for the object of his addiction. Eventually, he becomes tolerant. This is where his body gets used to it. So, in order to get the same effect, he needs to consume more of the substance. The symptoms of addiction vary depending on the substance or activity and the person. Being without this substance, or activity, leads to withdrawal symptoms, which also vary based on the same factors. For example, symptoms of opiate (heroin, morphine, codeine, etc.)  withdrawal include anxiety, muscle aches, insomnia, and sweating. It can also lead to diarrhea, vomiting, shaking, and cramps. On the other hand, withdrawal from cocaine abuse can cause depression, vivid and unpleasant dreams, fatigue, paranoia. As you can tell, withdrawal from cocaine causes less of the physical symptoms that are associated with other drugs like heroin. More concrete ways to tell if someone is suffering from addiction or withdrawal are blood tests and urine analysis, where there will be actual physical evidence of the drug.

According to Medical News Today, chocolate is a valid substance to be addicted to. Maybe I need rehab!

Guillain Barré Syndrome: Do we really need Myelin Sheaths?

     Guillain Barré Syndrome is one of several demyelinating diseases. Demyelinating Diseases do just what the name implies, they demyelinate neurons. This is a very serious issue because myelin sheaths on axons are more than just decoration. They are used to transmit impulses quickly down the length of an axon. The speed of transmission in an unmyelinated axon is about 0.7m/s (2mi/hr). This is about the speed that you jog. You might think that this is fast enough because a human body is about 2 meters tall so an impulse travelling to your feet would only take about a second or two. And you would be partly right. This is fast enough for information that needs to be sent to your digestive tract and other not-super-important stuff. However, if you start to trip, you need to reposition your body within a split second.  This is where myelinated neurons come into play. Neurons innervating skeletal muscle are myelinated. This myelination increases speed of transmission to about 120m/s (270mi/hr). So now that you can see how important myelin sheaths are, lets talk about what it would be like to lose that myelination.

       There are two types of glial cells that assist with myelination: Schwann Cells and Oligodendrocytes. Schwann Cells wrap around axons in the peripheral nervous system while Oligodendrocytes hug axons in the central nervous system. Guillain Barré Syndrome occurs when specifically the peripheral nervous system is attacked and becomes demyelinated. The initial symptoms of this disease include weakness and tingling in the legs. These sensations slowly spread upwards to the upper body and arms. The brain being unable to transmit commands efficiently to the muscles causes the weakness. It can increase in intensity until some muscles can’t be used at all. This can be very severe because it leads to the individual becoming paralyzed. If the muscles used for respiration are affected, it can be potentially fatal. The tingling is because the sensory receptors cannot transmit information to the brain. It can manifest in an inability to feel heat, pain, and other sensations. Or, the brain might receive weird, altered signals that result in tingling, creepy-crawly, or even painful feelings.

      It is an autoimmune disease which means that it’s not a virus or bacteria destroying the myelin, its your own body. Sometimes, it can be caused be preceded by an infection. A virus or bacteria could have changed the cells in the nervous system so the immune system thinks they are foreign, or it could have made the immune system more belligerent and care less about what it attacks.

      Sadly, there is no cure for this syndrome; only therapies that try to lessen the intensity of the symptoms and treatments for its complications. 

     This article explains Guillain Barré Syndrome in a little more depth, as well as explains many of the complications and their treatments.  

NY Times: Guillain Barré Syndrome