This study will use microdialysis to investigate myofascial pain. This pain is characterized
by "trigger points" (exquisitely tender spots) in a group of tense muscle fibers that extend
from the trigger point to the muscle attachments. Trigger points in the trapezius, a large
muscle lying between the neck and shoulder, are typically caused by emotional stress,
postures such as hunching shoulders, certain activities like using a telephone receiver
without elbow support, or by wearing certain articles such as a heavy coat or heavy purse.
Microdialysis uses a very thin needle probe (about the size and shape of an acupuncture
needle) to collect and measure chemicals directly from soft tissue. Analysis of these
chemicals will show whether changes in the tissue around a muscle with trigger points are
confined to that muscle, or if these changes also occur in more distant muscles.
The study will examine two types of trigger points. An "active" trigger point causes pain or
other abnormal symptoms and often causes problems with movement. A "latent" trigger point
often causes movement problems without causing pain. Many healthy adults have latent trigger
People between 21 and 65 years of age with the following characteristics may be eligible for
this study: 1) no neck pain or trigger points in either upper trapezius muscle; 2) no neck
pain but a latent trigger point in at least one upper trapezius muscle; or 3) neck pain of
less than 3 months' duration and an active trigger point in at least one upper trapezius
muscle. Participants undergo the following procedures:
- Physical examination of the muscles of the neck and shoulder area, testing strength and
range of motion, and response to palpation to find trigger points.
- Pain inventory. Subjects complete a questionnaire for measuring pain and its intensity,
location, quality, causes, relievers, and associated symptoms. The questionnaire is
filled in before and after each microdialysis procedure.
- Microdialysis in upper trapezius muscle. An electrode patch is placed on either side of
the site for insertion of the microdialysis probe and another electrode is placed on the
outer edge of the shoulder. The electrodes are used to measure any electrical activity
that occurs with insertion or movement of the probe. The subject lies face down and the
probe is inserted in the upper trapezius muscle. It remains in place for 5 minutes while
chemical substances are collected from the muscle. It is then advanced about 1.5 cm
deeper into the muscle until a twitch response is obtained and remains in place for 10
more minutes while substances are collected.
- Microdialysis in the gastrocnemius muscle (large muscle of the calf). The same procedure
for the upper trapezius muscle is done in the calf muscle.
Preliminary data suggest that patients with active myofascial trigger points (MTrPs) have a
significantly different biochemical profile within the local milieu of the MTrPs compared to
those without MTrPs or those with a latent (non-symptomatic) MTrP. An important question to
answer is whether anatomical loci, remote from active or latent MTrPs have similar
biochemical profiles to the MTrP itself. These remote sites should be evaluated to help
distinguish whether MTrPs have local biochemical profiles or are associated with a more
We will select three groups of subjects based on the following characteristics [1, 2, 3
below]. We will sample GB-21 in the upper trapezius muscle and LV-7 (posterior and inferior
to the medial condyle of the tibia in the upper portion of the medial gastrocnemius)
standardized sites for pH, muscle metabolites, inflammatory mediators, arachidonic acid
derivatives, neuropeptides, etc.
The goal of this study is to determine whether the local biochemical milieu of an active MTrP
is the same as the biochemical milieu at anatomical sites remote from the MTrP.
The acupuncture points GB-21 and LV-7 are selected specifically to standardize the locations
of a sampling point in three carefully selected groups:
1. healthy subjects without neck pain and who have no MTrPs identified by palpation
bilaterally in GB-21, and who have no MTrPs identified by palpation bilaterally in LV-7,
2. healthy subjects without neck pain in whom latent MTrPs are identified by palpation in
GB-21 in one of the upper trapezius muscles, and who have no MTrPs indentified by
palpation bilaterally in LV-7,
3. healthy subjects complaining of neck pain of less than 3 months duration with active
MTrPs identified by palpation in GB-21 in one of the upper trapezius muscles, and who
have no MTrPs identified by palpation bilaterally in LV-7.
- INCLUSION CRITERIA:
A total of 24 adults are expected to be accrued (8 in each group; Normal, Latent and
Active) ages 18-65, without pain and those with continuous idiopathic cervical pain of less
than 3 months duration.
Atypical facial neuralgia.
History of trigger point injections in the upper trapezius muscle.
History of cervical spine or shoulder surgery.
History of previous trigger point injections in the medial gastrocnemius muscle.
History of below the knee or above the knee amputation.
History of total knee arthroplasty.
History of bleeding disorder.
Subjects on anticoagulation therapy.
If the subject has taken aspirin within 3 days of needling.
Other concurrent pain syndromes.
On any NSAID, COX2 inhibitor, TCA, narcotic, antiepilectic, muscle relaxant, ancetaminophen
or other medication for the purpose of pain relief.
Subjects who have an inoordinate fear of needles.
History of DVT.
History of Baker's Cyst.
History of Myopathy.
History of meniscal tear.
History of anterior cruciate ligament/posterior cruciate ligament/medial collateral
ligament/lateral collateral ligament tear.
History of knee surgery.
History of Achilles pathology or rupture.