Positron Emission Tomography to Measure Pain and Pain Control
Status:
Completed
Trial end date:
2005-08-01
Target enrollment:
Participant gender:
Summary
This study will examine how the brain processes pain signals and how the different parts of
the brain work with each other in response to painful stimuli. A better understanding of how
people experience pain may be helpful in developing more effective treatments.
Healthy normal volunteers, patients requiring third molar (wisdom tooth) extraction, and
patients with persistent pain due to disease, injury or other reason may be eligible for this
study.
Participants will receive one or more of the following sensory stimuli, which may cause brief
discomfort or pain:
- Heat/Cold - applied by an electronically controlled device that touches the skin, or by
temperature-controlled water baths, or by a thermally controlled brass cylinder the
subject grasps
- Capsaicin (active ingredient in hot chili peppers) - injected in a small volume of fluid
under the skin or into a muscle
- Mechanical stimulation - brushings or vibrations that do not normally cause pain
- Ischemic stimulation - inflation of a blood pressure cuff on the arm or leg for up to 30
minutes
These stimuli will be applied both before and during positron emission tomography (PET)
scanning. This test shows which parts of the brain are active and which are not and is
important for studying how different parts of the brain work together to feel and react to
specific sensations. For this procedure, the subject lies on a table in the PET scanner while
a series of scans are taken during different sensory conditions. At the beginning of each
scan, radioactive water is injected into an arm vein through a catheter (a thin plastic
tube). A special camera records the arrival and disappearance of the radiation in various
brain areas, creating a picture of the brain's activity in various regions. Oral surgery
patients may have PET scans both before and after their wisdom tooth extraction. Alfentanil,
a commonly used narcotic pain reliever, will also be given during the PET procedure to
determine how the brain responds to sensory stimuli while under the effects of a pain killer.
Participants will also have a magnetic resonance imaging (MRI) scan of the brain to help
interpret the PET results. MRI uses a magnetic field and radio waves to show structural and
chemical changes in tissues. During the scan, the subject lies on a table in a cylindrical
machine (the scanner). He or she can speak with a staff member via an intercom system.
Some sensory studies may require placing an arterial and/or intravenous line. Following
injection of a local anesthetic, a catheter is placed in an artery in the arm. At regular
intervals during various sensory stimuli, small blood samples are drawn from the artery to
measure blood gases and other substances. Samples may also be drawn from a catheter placed in
a vein.
Subjects may also have ultrasound monitoring to evaluate blood flow in the arteries, veins
and brain. A gel is spread over the skin above the blood vessel and a hand-foot-and-mouth
device is placed on the gel. The device emits high-frequency sound waves to produce a picture
of the speed of blood flow in the artery and the diameter of the vessel.
Details
Lead Sponsor:
National Institute of Dental and Craniofacial Research (NIDCR)