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."
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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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