Multiple
Sclerosis Introduction
Multiple
sclerosis is a slowly progressing neurological disease, which affects the central
nervous system. There are patches of demyelination where the myelin sheath, which
functions similar as insulation material around electric wires does, breaks down
in a process called demyelination. For electrical signals that were generated
in the brain to safely arrive at any part in the body, intact "wires"
are needed to deliver the message. In the nervous system of the body these "wires"
are called nerve tracts. They are made up of nerve fibers in the center of the
tract and they are surrounded by insulation material, which is made up of living
cells such as the oligodendroglia cells and Schwann cells. They stretch
out thin tentacles that wrap around the nerve fibers. This way they form an insulation
layer and enhance the speed of nerve impulse transmission. With
multiple sclerosis demyelination foci can be seen in the brain and the spinal
cord using MRI scanning technology. On a histological level there is a
breakdown of these insulating cells that provide the tentacles that normally wrap
around the nerve fibers. Iinflammation develops around these foci of demyelination,
which eventually leads to scarring. In the beginning the nerve cells and the axon
fibers are preserved. However, in the later stages of multiple sclerosis nerve
fibers are also destroyed, particularly in the long tracts of the spinal cord,
and are replaced with "fibrous gliosis", which is just another term
for scar tissue. These can be distinguished on an MRI scan as "old lesions".
"New lesions" from an early inflammatory reaction have a different appearance
on the MRI scan. At this point the cause for multiple sclerosis is not
known. However, we do know that there is an immunological abnormality taking place
at the level where these demyelination foci occur. For many years it has been
postulated that certain neurotropic viruses such as red measles, human herpes
virus or retroviruses may after an initial infection go "underground"
and incubate within nerve cells. A secondary immune response some 15 years later
would then be the cause of the initial multiple sclerosis attack. It is postulated
that there are certain HLA cell surface antigen constellations that are associated
with a higher risk for multiple sclerosis. This line of work was initiated when
pockets of families with a higher incidence of multiple sclerosis were found.
A certain HLA constellation was found to lead to a higher genetic susceptibility. Other
factors are certain geographic factors. For instance, it was noted that multiple
sclerosis is more common in temperate climatic regions where the incidence is
1 case in 2,000 of the population. In the tropics the incidence is only 1 in 10,000,
fivefold less. Another interesting observation is that this high frequency versus
low frequency occurrence of multiple
sclerosis has been linked to the geographic area where the first
15 years of a person's life were spent. The onset of the first multiple sclerosis
symptoms are typically in the age range of 20 to 40 years. Women tend to get it
more often than men. Full spectrum sunlight (the natural light from the sun) produces
vitamin D in the skin. In a publication in January of 2004 the protective
effect against MS with high enough vitamin D supplementation was
described (reported in my Feb. 2004 monthly health newsletter, see link).
The
above notion of MS being an autoimmune disease is getting more and more confirmed
by newer research and new therapies that have been recently developed or trials
that are still ongoing, but very promising. This was reviewed at the 50th Annual
continuing education conference of St. Paul's in Vancouver/BC/Canada by Dr. John
Hooge, Director of the UBC MS Clinic (Ref. 6). It is now confirmed that there
are two steps for MS before it becomes irreversible: First there is the inflammatory
phase of early MS where the autoimmune antibodies cause inflammation and loss
of the nerve pathways, seen on MRI scans as lesions. Secondly, with the later
MS there is further deterioration of the nerve pathway lesions by a degenerative
process that leads to the final destruction and interruption of the nerve pathways,
but there is little inflammation and therefore little change on the MRI scans.
A Canadian trial involving 24 patients is on the
way at the present time where the immune system was inactivated with high doses
of chemotherapy and the patients' own bone marrows that were harvested prior to
the chemotherapy were re-injected into the patients to re-establish a healthy
immune system without the autoantibody-producing immune cells. Some of these patients
have experienced miraculous turnarounds of their MS, but there is a 10% mortality
associated with the bone marrow transplant and longterm studies have to be awaited
as to whether the initial encouraging results hold true. There is also a late
complication from high doses of chemotherapy with leukemias being more common
5 to 10 years down the road. Genetic tests with experimental animals (autoimmune
mouse model) have shown encouraging results, but to translate these successes
safely into the human situation can take many years, if not decades. |
