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- Keyur P.
- Biology...Science
- Rasmussen's Encephalitis
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- The human immune system is an amazing system that is constantly on the alert protecting us from
- sicknesses. Thousands of white blood cells travel in our circulatory system destroying all foreign
- substances that could cause harm to our body or to any of the millions of processes going on inside. Now
- imagine a condition where this awesome system turns against the most complex organ in the human body,
- the brain. Deadly as it is, this condition is known as RasmussenÆs encephalitis.
- The meaningful research on RasmussenÆs encephalitis was begun (unintentionally) by Scott Rogers
- and Lorise Gahring, two neurologists, who were at the time measuring the distribution of glutamate
- receptors in the brain. Later on when more provocative information was found they enlisted the help of
- James McNamara and Ian Andrews, epilepsy experts at Duke University Medical Center.
- The details on RasmussenÆs encephalitis were very bleak at the time when the men began their
- research. All that was known is that RasmussenÆs encephalitis was a degenerative disease of the brain
- that caused seizures, hemiparesis, and dementia normally in the first ten years of life. The seizures that
- were caused by RasmussenÆs encephalitis were unstoppable by normal anti-seizure drugs used
- conventionally. What the worst part of the disease was that the pathogenesis for it were not known and
- even worse was how it developed.
- The first clue was delivered when Rogers and Gahring were trying to register the distribution of the
- glutamate receptors using antibodies, that tag on to the receptor itself. The proteins that make up the
- glutamate receptors(GluR) are only found inside the blood brain barrier(BBB). Glutamate and a few
- related amino acids are the dominant form of excitatory neurotransmitter in the central nervous system of
- mammals. If one of these GluRs happens to wander into the actual bloodstream, that is outside the BBB,
- it would be considered an outsider and destroyed immediately. So if these GluRs were put into the normal
- blood stream then the immune system would produce antibodies which could then be used in the
- searching for the glutamate receptors.
- In order to test this theory the researchers injected the GluRs into the blood stream of a normal
- healthy rabbit hoping to produce good results. At this point the experiment took a dramatic turn, after
- receiving a few doses of the protein two of the three rabbits began to twitch, as though they were suffering
- the pain of an epileptic seizure. Now the help of McNamara and Andrews was enlisted.
- When McNamara and Andrews examined the brain tissue of the rabbits, they saw what seemed to be
- a familiar inflammatory pattern, clumps of immune cells all around blood vessels. This description
- exactly matched the description of persons suffering from RasmussenÆs encephalitis, moreover something
- as this would never be found in a healthy brain. A healthy brain has its blood capillaries enclosed in the
- BBB membrane, so such a case as the one mentioned above would not be possible.
- As protective as the BBB is, it can be breached by something like a head injury. What was
- happening was that the antibodies which were out to get the GluR proteins were somehow finding a way
- into the brain and directing an attack towards all GluR receptor proteins in the brain itself.
- After some more examinations Rogers and McNamara decided that these attacks were the cause of
- the seizures that are often experienced by sufferers of RamussenÆs encephalitis. Then if the case is of
- antibodies in the bloodstream, than sufferers of RamussenÆs encephalitis should have them in their
- bloodstream and healthy normal peoples shouldnÆt. When this was actually tested the results were
- positive that Rasmussen sufferers did have these antibodies in their bloodstreams and healthy people did
- not. These were not only the right kind of antibodies but, the very antibodies that caused the seizures in
- people and rabbits. Thus when these antibodies were removed by plasma exchange(PEX) it caused a
- temporary relief from the seizures but soon the body starts making more antibodies of the type and the
- seizures start once again. After all the examinations two questions remained, why does the body mount
- an immune response against one of its own brain proteins, and how do these antibodies get through the
- BBB?
- What is thought right now is that people get antibodies when they are infected by a microorganism
- like a bacterium or a virus that is similar in structure to the GluR. When this happens the body mounts an
- immune response against, and it just so happens that at this stage you suffer a blow to the head. This will
- open your BBB to the antibodies and they will attack the friendly GluRs in the brain, causing seizures and
- further opening your BBB to more antibodies.
- Now a malicious rhythm begins: antibodies break through the BBB, inflammation is caused due to
- the break in, seizures are now caused and BBB opens up further, further opening in the BBB cause more
- seizures. The inflammation is caused by the autoimmune process against the GluR. All the seizures
- occur where the initial break in the BBB happened due to a blow to the head, explaining why they
- seizures are confined to just one hemisphere. The only problem with this theory is that the rabbits
- developed seizures without ever being whacked on the head, but that also could be because a rabbitÆs brain
- is not as well insulated as a humanÆs.
- Normally what happens to an individual is that after he or she is involved in this cycle the only
- thing that can make for relief is the recurrent plasma exchange. This will only cease the seizures
- temporarily, but they will start again when the body has made more new antibodies. After this has been
- done many times the hemisphere in which sufferers of RamussenÆs encephalitis is present will deteriorate
- to the point where a hemispherectomy has to be performed. This will render the person to mental
- disintegration where he or she has no more mental capacity and generally to the point of no return, death.
- RasmussenÆs encephalitis is a very deadly disease, but it is also a very rare disease, occurring in only
- 48 people between 1957 and 1987. As of now there are no FDA approved drugs for the sufferers of
- RamussenÆs encephalitis. Now the researchers are working on a drug that will block the activity of this
- particular antibody, but this could lead to further problems. If this drug is being administered and a
- bacteria or virus of a similar structure as the GluR is present the body would disregard it and this would
- cause more health problems. After all this bad news all one can say is, "Good luck" to the ones suffering
- from this living hell.
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- Atkins, "RasmussenÆs encephalitis: nueroimaging findings in four patients." AJR-Am-J-
- Roentgenol. June 1992.
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- Blume, "RasmussenÆs chronic encephalitis in adults." Arch-Nuerol. March 1993.
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- Hanovar, "RasmussenÆs encephalitis in surgery for epilepsy." Dev-Med-Child-Nuerol.
- January 1992.
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- Leary, "Clues Found To Rare Form of Epilepsy." New York Times. December 5 1994,
- pp. A4.
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- Whisenand, "Autoantibodies to glutamate receptor GluR3 in RasmussenÆs encephalitis,"
- Science. July 29 1994.
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