Neurology and Encephalomyelitis
Some points of
interest from
an
internationally recognized
authority in
multiple sclerosis
and
Professor of Neurology
Harvard
Medical School
---------------------------------------------------
" while
"encephalopathy" is a generic term that simply describes
a
pathological condition of the brain; "encephalomyelitis" refers to
an
"allergic" or immune reaction of the nervous system. It is the
latter term
that should be generally used for the nervous system
complications of vaccinations."
======================================================
Neurological
Complications of Vaccinations
By
Charles M. Poser MD FRCP
Neurological complications of immunizations have been recorded in the
medical
literature for many years, yet many physicians fail to
recognize their clinical manifestations and identify their etiology.
This is
due in part to their rarity, and to the well-publicized,
overriding public health benefits that make these complications easily
overlooked. Yet they can be devastating despite the fact that early
treatment is often successful.
A great
deal of knowledge regarding their pathogenesis has
accumulated over the years based on the existence of excellent animal
models
of the human disease, acute disseminated encephalomyelitis,
the
commonest neurological manifestation of an adverse immune
response to vaccines. Experimental allergic encephalomyelitis and
neuritis faithfully reproduce the pathologic alterations of the
nervous
system that may complicate immunizations.
Adverse
reactions involving the nervous system from a wide variety of
immunizations result from the same pathogenetic mechanism. They may
affect
any and all parts of the central and peripheral nervous
systems. With rare exceptions, e.g. rubella immunization, the nature
of the
vaccine does not seem to influence the nature of the response.
Thus
the nervous system ailments include many different clinical
forms,
ranging from the classic acute disseminated encephalomyelitis
to
aseptic meningoencephalitis. In rare instances, in the case of live
viruses, e.g. polio and smallpox, an actual infection by the virus
itself
may ensue. Many different vaccinations involving many different
sites
in the nervous system have been reported. This is particularly
true of
vaccines commonly used in children against measles, varicella
and
rubella.
The
pathogenetic mechanism is as follows: the primary effect of the
hyperergic (immune) reaction is on the small blood vessels of the
nervous
system, usually capillaries, but occasionally involving
arterioles and venules; in exceptional circumstances, even major
arteries such as the carotid may be affected. The vasculopathy may
cause
vessel obstruction and ischemia, a stroke. Rupture of the vessel
wall
results in hemorrhage.
More
commonly, however, there is alteration of the blood-brain
barrier, exsudation of water and edema (swelling) of nervous tissue.
Inflammation and disorganization of the myelin lamellae (layers) and
destruction of myelin may ensue but are not obligatory. In some cases,
there
is sufficient red blood cell diapedesis (migration through the
vessel
wall) to produce what is known as acute hemorrhagic
leukoencephalopathy, which despite its awesome appearance is usually
responsive to vigorous treatment.
The
extent of pathological involvement of nervous tissue also varies
greatly, as seen in vaccination against measles, mumps and varicella.
In
infants, brain swelling, also known as congestive edematous
encephalopathy, may be the only complication, a condition that often
responds dramatically to treatment with corticosteroids. It occurs
most
commonly in vaccination against smallpox.
The
diagnosis of acute disseminated encephalomyelitis, the commonest
complication of vaccinations in both children and adult, has been
aided
by magnetic resonance imaging (MRI). The pictures are reasonably
characteristic, yet, unfortunately, despite many published
descriptions, these images are not always correctly interpreted, and
are
often misread as those of multiple sclerosis.
There
is also some confusion in terminology: "encephalitis" and
"meningoencephalitis"
refer to actual invasion of the brain by a
virus,
while "encephalopathy" is a generic term that simply describes
a
pathological condition of the brain; "encephalomyelitis" refers to
an
"allergic" or immune reaction of the nervous system. It is the
latter
term that should be generally used for the nervous system
complications of vaccinations.
The
official publications that commented on the ill effects of the
1976
swine-flu (A-New Jersey 76) vaccination campaign illustrate the
problems that arise when there is need to extrapolate scientific data
to
judicial considerations. The report stating that the
Landry-Guillain-Barré
syndrome (LGBS) was the only "real" complication
of the
swine-flu vaccine passed over published reports to the
contrary. The statement that there had been underreporting of
complications was simply ignored. The accepted view is that if an
adverse
reaction does not reach the magical figure of 5 percent, it
does
not exist.
The
reverence accorded to statistical analyses overlooks the value of
anecdotal reports in constructing valid medical hypotheses; this is
despite
the warnings by respected epidemiologists that such studies
can
never deny the existence of a cause-and-effect relationship. This
is
illustrated by the report of nervous system complications following
vaccination against hepatitis B. Another problem arose from the
decision to limit the "acceptable" time period of onset after
immunization, which ignored a number of reports of well-documented
delayed
reactions.
In the
last few years a new mantra has emerged to the effect that all
published results such as proposed new treatments, must meet the test
of
being "evidence-based," which means that they must be derived from
statistically verified data. Thus calculations of probabilities, also
known
as educated guesses, will take precedence over clinical,
pathological, radiological or experimental data. Close examination of
some
specific situations will reveal the flaws of this concept.
There
is no way of predicting who will have an adverse reaction to
vaccination. The individual's susceptibility is determined by the
genetic
background and previous immunological history. We are
constantly exposed to a wide variety of viral antigens that cause our
immune
system to develop antibodies against them. The phenomenon of
molecular mimicry explains why some people's immune system will
mistakenly respond to the measles antigen, for instance, in the
vaccine
because some of its amino acid groupings, its epitopes, are
the
same as those in the protein of a previously encountered viral
antigen.
This is
why there was an unexpected preponderance of people in their
50s and
60s who developed LGBS after swine-flu vaccination, because
they
might have been exposed to the "Asian flu" caused by a somewhat
similar
virus in the 1920s. It is also germane to point out that
vaccines contain a number of substances, many of them as antigenic as
the one
for which they were designed. Preservatives may also
contribute to the adverse side effects. It is extremely difficult to
distinguish the effects of the vaccines' constituents.
Physicians often neglect to ask about previous vaccinations when
confronted with puzzling neurological illness. Most of them appear to
have
been convinced that immunizations are completely harmless. Many
also
believe that such reactions must occur within one month from
vaccination, and therefore do not inquire about immunizations in
previous months.
Because
of the expense of testing drugs, vaccines and other medical
products, the pharmaceutical industry has assumed an increasingly
important role in the conduct of therapeutic trials and post-marketing
surveillance. This is both understandable and often
beneficial. On the downside, however, is the appearance of conflict
of
interest when the analyses of the results are carried out by the
pharmaceutical firm itself, or the government agency charged with
guarding the safety of the product.
Dr. Poser is Visiting Professor of
Neurology, Department of
Neurology, Harvard Medical School, Boston,
and is senior neurologist
with Beth Israel Deaconess Med Center in
Boston.
[Copyright 2003 by the author.
First printed in Mealey's Litigation
Report, Thimerosal & Vaccines,
Volume 1, Issue #10, April 2003]
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