Pain Pathways in the Brain
Information source: National Institutes of Health Clinical Center (CC)
Information obtained from ClinicalTrials.gov on June 20, 2008
Link to the current ClinicalTrials.gov record.
Condition(s) targeted: Healthy; Tooth Extraction
Intervention: MRI (Procedure)
Phase: Phase 2
Sponsored by: National Institute of Dental and Craniofacial Research (NIDCR)
This study will evaluate brain pathways involved in feeling pain and pain relief following
administration of pain medication. Magnetic resonance imaging (MRI) will be used to measure
brain activity at sites that become more active following oral surgery and then to see if the
activity changes after pain medication is administered. MRI combines a powerful magnet with
an advanced computer system and radio waves to produce detailed pictures of organs and
tissues. During the scan, the subject lies on a table in a narrow cylinder containing a
magnetic field. He or she can speak with a staff member via an intercom system at all times
during the procedure.
Healthy dental patients recruited through the NIH Clinical Research Volunteer Program may
enroll in this study. Participants will undergo the following tests and procedures in two
Visit 1 - Sensitivity Testing
Participants are tested for sensitivity to warm and hot temperatures. A probe is applied to
the skin (usually the forearm) and heated to temperatures ranging from room temperature to
that of a hot cup of coffee. Participants rate the temperature using a scale ranging from "no
pain" to the "worst pain imaginable" and rate the unpleasantness of the heat using a similar
scale. The probe is applied up to 30 times, using random heat intensities. Participants are
also asked compare the heat intensity to varying levels of sounds and to rate the magnitude
of different sensations they have experienced in the past, such as the brightness of the sun
and the loudness of a jet plane. A blood sample of about 2 ounces is also collected at this
visit for DNA analysis to look for genes related to pain.
Visit 2 - Oral Surgery
Under local anesthetic, participants undergo extraction of their lower right wisdom tooth.
After surgery, the patient is moved to the MRI scanner for brain imaging over 1-2 hours while
the local anesthetic wears off. Patients may request a postoperative pain drug (Toradol)
during the procedure, if needed. When the scan is complete, patients are dismissed from the
clinic with additional pain medication (flurbiprofen) to use at home as directed.
Official title: Imaging Neural Mechanisms Underlying Pain Modulation
Study design: Treatment, Safety/Efficacy Study
Functional neuroimaging provides a powerful tool for understanding how the brain may be
involved in the perception of pain. It has made it possible to identify areas of the brain
that are involved in the perception of experimental pain but very few studies have evaluated
the sites in the brain that are activated during clinical pain and the effects of analgesic
drugs. The proposed study will use the surgical removal of an impacted third molar as a
model of acute clinical pain to identify sites that are activated following the offset of
local anesthesia and to examine the effects of the NSAID analgesic ketorolac on attenuating
sites that are activated as pain is relieved. Scans will be performed under non-pain
baseline conditions, and again immediately following surgery as the local anesthetic wears
off, clinical pain occurs, and following administration of the NSAID ketorolac. Differences
among subjects in the amount of pain reported and brain activation will be compared to
subjects' prior ratings of experimental pain and the presence of any genetic polymorphisms
that are related to pain perception, inflammation, known pain pathways, or psychological
factors related to pain. The findings from this research may help to reveal how pain is
appreciated in the central nervous system, pharmacologically modified by NSAID analgesics and
differs among individuals due to genetic factors.
Minimum age: N/A.
Maximum age: N/A.
Subjects will be a convenience sample selected from the pool of 500 - 700 new patients
screened annually for acute pain studies. Inclusion and Exclusion criteria will be applied
to result in a homogeneous population of subjects with respect to the surgical difficulty
of the tooth being extracted, a single lower right third molar.
Locations and Contacts
National Institute of Dental And Craniofacial Research (NIDCR), Bethesda, Maryland 20892, United States
Bingel U, Quante M, Knab R, Bromm B, Weiller C, Buchel C. Subcortical structures involved in pain processing: evidence from single-trial fMRI. Pain. 2002 Sep;99(1-2):313-21.
Apkarian AV, Krauss BR, Fredrickson BE, Szeverenyi NM. Imaging the pain of low back pain: functional magnetic resonance imaging in combination with monitoring subjective pain perception allows the study of clinical pain states. Neurosci Lett. 2001 Feb 16;299(1-2):57-60.
Chen AC. New perspectives in EEG/MEG brain mapping and PET/fMRI neuroimaging of human pain. Int J Psychophysiol. 2001 Oct;42(2):147-59. Review.
Starting date: February 2004
Ending date: August 2005
Last updated: March 3, 2008