Pathophysiology of Post Amputation Pain
Your participation in this study will last for 5 weeks and you will be asked to come to a
total of 3 visits. The first visit will be during the first week of the study, the second
visit during the second week of the study and the third (final) visit will be during the
fifth (and final) week of the study. For your first visit you will have a physical
examination with some sensory stimulation tests (such as vibration and pinprick tests), some
questionnaires about your health and pain history, hot and cold sensory tests, and we will
take thermal pictures of your body before and after receiving a quick electrical stimulus.
You will also be trained on how to use the finger-span device to rate your pain during the
second visit, and how to use an electronic pain diary to record your pain scores three times
a day during the five weeks of the study.
The second visit will begin with questionnaires from the first visit and thermal images with
a quick electrical stimulus. You will then be brought to an fMRI scanner room at
Northwestern University. For an hour and fifteen minutes we will take pictures of your
brain and these pictures will help us understand the changes in your brain relating to pain.
You will then be put into one of four treatment groups randomly.
The study treatment that you will get will be decided randomly or by chance, like flipping a
coin. Injections in this study will use the local anesthetic bupivacaine (a long lasting
drug like the numbing agent novocaine used by dentists). This drug causes numbness, blocks
pain and other nerve function near the injection site for 6-8 hours. Group 1 will get a
sympathetic nerve block of bupivacaine, which changes how your nerves transmit pain, in
either the neck or lower back (depending on where the amputation is located), Group 2 will
get a placebo injection (no active medicine) in either the neck or lower back (depending on
where the amputation is located), Group 3 will get a neuroma injection of bupivacaine (a
neuroma is a group of nerves at the end of your residual limb), and Group 4 will get a
placebo injection (no active medicine) at the neuroma. Some people get the bupivacaine
injection and some people get the placebo injection so that we can compare the groups and
see if the bupivacaine brings more, less or the same pain relief as a placebo injection. We
scan your brain before the injection so that we can see how your brain responds to pain. We
also scan your brain after the injection so that we can see if your brain responds
differently to pain after the injection has been done.
You will know the location of your injection before you receive the treatment (neck, lower
back or neuroma on your affected limb), but you will not know if you are getting a pain
medication injection or placebo injection. Only the study doctors will know this
information, and it can be told to you in case of an emergency. After the injection, you
will have a second hour of brain scanning. After the scanning, you will be asked to complete
some questionnaires, sensory tests, hot and cold temperature testing and we will take
thermal pictures of your body before and after a quick electrical stimulus.
Your third visit will be four weeks after your second visit. For your third visit you will
have the same questionnaires as during the first and second visits, sensory tests, hot and
cold temperature testing and we will take thermal pictures of your body before and after a
quick electrical stimulus.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Single Group Assignment, Masking: Single Blind (Subject), Primary Purpose: Treatment
Change in Electronic Pain Diary Ratings
A time series analysis will be utilized to compare the change in pain diary 0-10 numeric ratings before and after the injection.
Ratings 3 times a day for 5 weeks
Norman Harden, M.D.
Rehabilitation Institute of Chicago
United States: Institutional Review Board
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