What
is peripheral neuropathy?
Peripheral
neuropathy is a nervous system condition that causes numbness, tingling, and
muscle weakness by involvement of the peripheral nervous system, that is, nerves
outside the brain and spinal cord.
Why
are Vietnam veterans concerned about peripheral neuropathy?
Does Agent Orange/dioxin cause it?
Some
Vietnam veterans have been diagnosed with peripheral neuropathy and others have
expressed concern about developing this condition. Some scientific literature has linked peripheral neuropathy
to exposure to dioxin, which was contained in Agent Orange.
On
May 23, 1991, the Veterans' Advisory Committee on Environmental Hazards
considered the relationship between exposure to dioxin and the development of
this condition. The Committee
concluded that there is a "significant statistical association"
between peripheral neuropathy and exposure to dioxin.
The Committee qualified this opinion, stating that the association could
be said to exist in the absence of exposure to chemical substances known to
cause this disorder. Committee
members indicated that other risk factors that must be considered are age and
whether the individual suffers from other known causes of peripheral neuropathy
such as diabetes, alcoholism, or Guillain-Barre syndrome. The Committee also advised that the disorder must become
manifest within ten years of the last known dioxin exposure.
What
did the Department of Veterans Affairs (VA) do in response to the Advisory
Committee's finding and the subsequent report released by the National Academy
of Sciences in July 1993?
On
July 1, 1991, Secretary of Veterans Affairs Derwinski announced that VA will
propose rules granting service-connected disability status to certain veterans
with peripheral neuropathy. Proposed
rule implementing the Secretary's decision was published for public comment in
the Federal Register in January 1992.
(See 57 Fed. Reg. 2236, January 21, 1992).
It was anticipated that the final rule would be published in 1993.
However, in July 1993, when the National Academy of Sciences (NAS) released its
comprehensive report, entitled Veterans and Agent Orange -
Health Effects of Herbicides Used in Vietnam,
peripheral neuropathy was not included in the category "sufficient evidence
of an association" or even "limited/suggestive evidence of an
association." Rather, the NAS
reviewers concluded that there is "inadequate or insufficient evidence to
determine whether an association exists between exposure to herbicides (2,4-D;
2,4,5-T and its contaminant TCDD; cacodylic acid; and picloram) and disorders of
the peripheral nervous system." The
NAS report added, "Although many case reports suggest that an acute or
subacute peripheral neuropathy can develop with exposure to TCDD and related
chemicals, reports with comparison groups do not offer clear evidence that TCDD
exposure is associated with chronic peripheral neuropathy.
The most rigorously conducted studies argue against a relationship
between TCDD or herbicides and chronic neuropathy."
Acute
is used to mean immediate effect, as opposed to chronic that means an effect not
appearing immediately.
VA
asked the NAS, in its follow-up report, to consider the relationship between
exposure to herbicides and the subsequent development of the acute and subacute
effects of peripheral neuropathy (as compared to the chronic effects, which were
focused on in the initial report).
In
January 1994, VA published a notice in the Federal Register that
Secretary Brown has determined that a presumption of service connection based on
exposure to herbicides used in Vietnam is not warranted for a long list of
conditions identified in the NAS report. Peripheral
neuropathy was included in this list. (See
59 Fed. Reg. 341, January 4, 1994).
What
did the NAS 1996 update conclude about peripheral neuropathy?
When
the NAS reviewers separately reviewed chronic persistent peripheral neuropathy
and acute and subacute transient peripheral neuropathy, they found that there
was still inadequate or insufficient evidence to determine whether an
association exists between exposure to herbicides and chronic persistent
peripheral neuropathy. On the other
hand, they reported that there is some evidence to suggest that “neuropathy of
acute or subacute onset may be associated with herbicide exposure.”
They included acute and subacute transient peripheral neuropathy among
those conditions they placed in their second category “limited/suggestive
evidence of an association.” (Chronic
persistent peripheral neuropathy remained in category three,
“inadequate/insufficient evidence to determine whether an association
exists.”)
What
was VA’s response to the NAS 1996 finding about acute and subacute transient
peripheral neuropathy?
After
careful review of the report, Secretary Brown decided that VA should add acute
and subacute peripheral neuropathy (when manifested within one year of exposure)
to the list of conditions recognized for presumption of service connection for
Vietnam veterans based on exposure to herbicides.
President Clinton announced this, along with other, decisions, at the
White House, on May 28, 1996. The
proposed rule was published for public comment in the Federal Register in
August 1996. (See 61 Fed. Reg.
41368, August 8, 1996). The final rule was published in the Federal Register
in November 1996. (See 61 Fed.
Reg. 57587, November 7, 1996).
What
did subsequent NAS updates conclude about peripheral neuropathy?
With
regard to chronic persistent peripheral neuropathy, the 1998 report stated,
“No new information has appeared in the intervening two years that alters this
(the 1996) conclusion.”
With
regard to acute and subacute transient peripheral neuropathy, the 1998 update
reported, “The committee is aware of no new publications that bear on this
issue. If TCDD were associated with
the development of transient acute and subacute peripheral neuropathy, the
disorder would become evident shortly after exposure.
The committee knows of no evidence that new cases developing long after
service in Vietnam are associated with herbicide exposure.”
In
update 2000: For chronic persistent
peripheral neuropathy, there is only inadequate or insufficient evidence to
determine whether an association exists between exposure to dioxin or the
herbicides studied in this report. NAS found that there was limited/suggestive
evidence of an association between exposure to the herbicides considered in this
report and acute or subacute transient peripheral neuropathy. The
evidence regarding association was drawn from occupation and other studies in
which subjects were exposed to a variety of herbicides and herbicides
components. Information available to NAS cotinued to support this conclusion.
The 2002 update
concluded that there is inadequate or insufficient evidence to determine whether
an association exists between the chemicals studied and chronic persistent
peripheral neuropathy. In relation
to acute and subacute transient peripheral neuropathy, the NAS concluded that
there was limited or suggestive evidence of an association between chemical
exposure and the disease, as stated in the update 1996 report.
Update 2002 also indicated that if TCDD were associated with the
development of transient acute and subacute peripheral neuropathy, the disorder
would become evident shortly after exposure.
The NAS was unaware of any evidence
that new cases developing long after service in Vietnam that could be attributed
to herbicide exposure in Vietnam.
Where
can a veteran get additional information about peripheral neuropathy?
Information
regarding peripheral neuropathy and related matters can be obtained at VA
medical center libraries, from the Environmental Health Clinicians at every VA
medical center, or from the Environmental Agents Service (131), Department of
Veterans Affairs, 810 Vermont Avenue, N.W., Washington, DC 20420.
Where
can a veteran obtain additional information about Agent Orange–related issues?
The following Agent Orange Brief fact sheets (including the one you are reading)
are available on the World Wide Web at www.va.gov/AgentOrange: A1.Agent Orange - General Information; A2.Agent Orange
Class Action Lawsuit; B1.Agent Orange Registry Program; B2.Agent Orange –
Health Care Eligibility; B3.Agent Orange and VA Disability Compensation; B4.VA
Information Resources on Agent Orange and Related Matters; C1.Agent Orange –
The Problem Encountered in Research; C2.Agent Orange and Vietnam Related
Research – VA Projects; C3.Agent Orange and Vietnam Related Research –
Non-VA Projects; D1.Agent Orange and Birth Defects; D2.Agent Orange and
Chloracne; D3.Agent Orange and Non-Hodgkin’s Lymphoma; D4.Agent Orange and
Soft Tissue Sarcomas; D5.Agent Orange and Peripheral Neuropathy; D6.Agent Orange
and Hodgkin’s Disease; D7.Agent Orange and Porphyria Cutanea Tarda; D8.Agent
Orange and Multiple Myeloma; D9.Agent Orange and Respiratory Cancers; D10.Agent
Orange and Prostate Cancer; D11.Agent Orange and Spina Bifida; D12.Agent Orange
and Diabetes; and D13.Agent Orange and Chronic Lymphocytic Leukemia. Hard copies can be obtained from
local VA medical centers or from the VA Central Office at the Environmental
Agents Service (131) Department of Veterans Affairs, 810 Vermont Avenue, N.W.,
Washington, DC 20420.
At the same Web site you will find copies of
past and current issues of the “Agent Orange Review” newsletter and other
items of interest.
This
fact sheet was prepared in late October 2003 and does not include any subsequent
developments.