Undiagnosed Small Fiber Polyneuropathy Is It a Component of Gulf War Illness
GWIRP 2012 Investigator Vignette Title: Undiagnosed Small Fiber Polyneuropathy:Is It a Component of Gulf War Illness? Investigators: Max Klein, PhD and Anne LouiseOaklander, MD, PhD; Massachusetts General Oaklander: Our grant is to test the hypothesisthat what we call Gulf War Illness may in some patients be a signal of underlying peripheralneuropathy. Klein: And so we're recruiting 150 Veteranswho are ill with Gulf War Illness and also 150 Veterans who are free of Gulf War Illness.And we're comparing their results with these
test results that we've obtained in thepast to see which ones give us the best indication of Gulf War Illness and hence, small fiberpolyneuropathy. Oaklander: Gulf War Illness is a mysteriousconstellation of symptoms, socalled multiorgan symptoms, meaning they affect a lot of differentparts of the body. Other labs have established that Gulf War Illness is a true medical problem,but no one has been able to figure out what the underlying cause is. And that's reallyimportant because when you don't know the cause of something it's very hard to treatit effectively. Klein: What we're studying right now isthe hypothesis that there's a component
of Gulf War Illness that may be due to a specifictype of small fiber polyneuropathy; that would be a disorder of some small nerve fibers.And it turns out that the symptoms from this small fiber polyneuropathy bear a strong resemblanceto a lot of the symptoms of Gulf War Illness. And so what we're trying to do is to establisha relationship between the two with a series of tests. Oaklander: This research grant has two partsto it. The first is to study normal nonVeteran as well as Veterans to find out what are thebest tests to diagnose this kind of small fiber polyneuropathy.
The second part of the study is to apply thesebest tests specifically to Gulf War Ill Veterans and controls to see if we can detect smallfiber polyneuropathy disproportionately among the Gulf WarIll population. Specific testsinclude the use of skin biopsies that are specially stained to reveal the nerve endingswithin. These are counted and compared to what we would expect from a normal personto look for evidence of neuropathy. We also use a battery of tests of autonomic function,things such as heart rate, blood pressure, and sweating activity. These are all underneural control, and so if they're abnormal, it can be a sign of neuropathy.
Klein: So the first one is a sweat test andwe introduce a little chemical into the skin that will actually make you sweat in a certainarea, and we actually collect the sweat and measure it and see how much sweat has beenproduced in that area. And another test is a tilt table test. Andall we do there is we're simulating the action of say when you stand up suddenly froma crouched position. You sometimes get lightheaded because your body hasn't quite reacted torestored blood flow to your brain fast enough. So we do exactly that; and all the while we'remonitoring their heart rate and blood pressure. What we're really looking for mostly isa reaction to theâ€”the stress that we're
putting on the body. So the difference betweenbeing recumbent and being tilted upward should result in a characteristic change in yourblood pressure and heart rate, which if your body is functioning correctly will then recoverfrom. So we have of course the biopsy where we'relooking for abnormal densities of nerve fibers in the skin. So that tells us one thing. Theseautonomic function tests tell us if there's a malfunction in the nerve fibers.And it turnsout that results of the skin biopsy and results with the autonomic function test don't alwayscorrelate at the same time; so in other words, it may be that oneâ€”one effect is seen beforethe other. So we're trying to establish